>> WELL, GOOD AFTERNOON, I'M ANDIE GIVE ITG AND I'M THE SCIENTIFIC DIRECTOR FOR NICHD. THANK YOU FOR COMING TODAY. IT'S MY PLEASURE TO INTRODUCE OUR SPEAKER ELEN LUMPKIN. SOME OF YOU MAY BE WONDERING WHAT THIS HAS TO DO WITH SENSATION? I WAS TALKING TO A COLLEAGUE ON FROM FRIDAY FROM THE HELEN KELLER NATIONAL CENTER AND I REALIZE FOR THE DEAF-BLIND, BY TOUCH IS HOW THEY COMMUNICATE AND IT'S ALSO HOW ALL BLIND PEOPLE READ. AND SO, THIS IS REALLY A MEDICALLY SIGNIFICANT ISSUE AMONG OTHER APPLICATIONS, SO, THAT--IN ADDITION TO THE FACT THAT THERE'S COUSINS OF INNER EAR HAIR CELLS IN THE SKIN WHICH I'M SURE ELEN WILL TELL US ABOUT. SO ELEN WAS BORN AND RAISED IN TEXAS AND THAT WAS THE BEGINNING OF A CYCLE OF OSCILLATIONS BETWEEN NEW YORK AND TEXAS. SHE RECEIVED HER UNDERGRADUATE DEGREE IN ANIMAL SCIENCE AT TEXAS TECH AND HE HAD ALSO SPENT TIME AT TEXAS A&M. SHE STAYED IN TEXAS FOR HER Ph.D. AT UT SOUTHWESTERN WHERE AT THE TIME JIM HUDSPET H WAS STARTING UP HIS INDEPENDENT RESEARCH PROGRAM AND AFTER 3 YEARS HE PICKED UP AND MOVED WITH DR. HUDSPETH TO THE ROCKEFELLER AND ELLEN WAS ON THE GROUND FLOOR OF THE OBSERVATION OF HAIR CELL FUNCTION AND PHYSIOLOGY FOR WHICH DR. HUDSPETH IS KNOWN AND THESE INCLUDED CALCIUM ENTRY THROUGH THE MECHAN O TRANSDUCTION CHANNEL OF HAIR CELLS TO LOCALIZE THE SIDE OF THE CHANNELS, THE CALCIUM SELECTIVITY OF THE CHANNEL AS WELL AS REGULATION OF FREE CALCIUM AND STEREO CILIA. AFTER FINISHING UP Ph.D. WORK AT ROCKEFELLER SHE WEPT ON IT A POST DOC IN WASHINGTON WITH JOHN HOWARD IN BIOPHYSICS AND I BELIEVE IT WAS THERE THAT SHE MADE HER PIVOT TOWARDS CUTANEOUS MECHANO SENSATION AND QUICKLY, MOVED TO A UNIQUE PROGRAM AT UCSF, CALLED THE FELLOW PROGRAM WHICH SOUNDS A LOT LIKE EARLIER INVESTIGATOR PROGRAM HERE TO GET OUR BEST AND BRIGHTEST INTO THE INDEPENDENT TRACK AS EARLY AS POSSIBLE. IT'S THERE SHE DEVELOPED HER PROGRAM ON CUTANEOUS MECHANO SENSATION WITH A SPECIAL INTEREST IN MIRACLE CELLS IN AND 1 OF THE FIRST PAPERS ID READ WAS THE USE OF GFP TAG TRANSGENIC MICE TO ISOLATE THE CELLS FROM THE MOLECULAR PROFILES AND I THOUGHT THAT WAS REALLY COOL. SHE THEN WENT TO AN INDEPENDENT POSITION AT BAYLOR AS AN ASSISTANT PROFESSOR OF NEUROSCIENCE FOR 4 YEARS BUT TRUE TO HER CYCLICAL NATURE AND GEOGRAPHIC LOCATION, SHE MOVED BACK TO COLUMBIA IN 2010 WHERE THESE BEEN AN ASSOCIATE PROFESSOR OF SOPHISTICATED MAT O SENSORY RESEARCH IN COLUMBIA, SHE HAS MANY AWARDS AND LEADERSHIP POSITIONS AND CONFERENCES, AND I'VE BEEN IMPRESSED BY HER ABILITY TO BRING DIFFERENT TOOLS TO UNDERSTAND MECHANO SENSATION AND THE TITLE OF TODAY'S TALK IS MECHANISMS OF SENSORY SIGNALING IN MAMMALIAN TOUCH RECEPTOR AND IT'S MY PLEASURE TO INTRODUCE DR. LUMPKIN. >> THANK YOU. OKAY, THANK YOU. THANKS FOR THE OPPORTUNITY TO VISIT THE NIH CAMPUS, THIS IS MY FIRST TIME TO DO SO AND TO PRESENT AN OVERVIEW OF OUR WORK, TRYING TO UNDERSTAND MECHANISMS AND SENSORY COAT NOTHING MAMMALIAN TOUCH RECEPTORS. THE NEURONS THAT INITIATE OUR SENSES OF TOUCH AND PAIN, ARE PSEUDOUNIPOLAR NEURONS THAT RESIDE IN DORSAL ROOT AND TRIGEMINAL GANGLIA AND THEY SEND SENSORY ACONS TO TARGETING SYSTEM THE TISSUES LIKE THE SKIN WHERE THEY ENCODE SENSORY STIMULI THAT CAN BE MECHANICAL OR THERMAL OR CHEMICAL IN NATURE INTO CHAINS OF ACTION PROTENTIAL THAT BACK ALONG THIS CABLE TO THE SYNAPSE SIS EITHER IN THE SPINAL CORD OR THE HYPED BRAIN SO THAT INFORMATION FROM THE PERIPHERY CAN BE TRANSMITTED TO AND INTERPRETINAL LOCATIONED BY THE BRAIN. NOW THE SKIN IS OUR LARGEST SENSORY ORGAN AND IT'S A VARIETY OF MORPH LOGICALLY AND PHYSIOLOGICALLY DISTINCT RECEPTORS. HERE I'M SHOWING A 3DAL RECONSTRUCTION THROUGH FULL IF I THICKNESS MOUSE SKIN. THIS IS HAIRY SKIN, YOU CAN TELL THAT BECAUSE OF THE AUTOFLUORESCENT HAIR SHAFTS THAT ARE THE BIG TREE TRUNKS HERE AND WHAT YOU CAN SEE OR I HOPE YOU APPRECIATE HERE IS THAT THE NEURONS THAT INNERIVATE THE HAIRY SKIN ARE MORPH LOGICALLY DISTINCT ININATE AND YOU ARE SOME OF THEM WIND UP THROUGH THE DERMIS TO EPIDERMIS AND HAIR FOLLICLES BY MAKING THESE RINGS CALLED CIRCUMFERENTIAL OR THESE PICKET FENCES CALLED ENDING. NOW 1 OF THESE FEATURES OF THESE NEURONS ARE THAT THEY ARE PHYSIOLOGICALLY SPECIALIZED TO ENCODE DISTINCT SENSORY QUALITIES FROM THE STIMULI THAT IMPINGE UPON OUR SKIN. SO FOR EXAMPLE, THE CORE PUSLE, THIS ONJON SHAPED RECEPTOR HERE, IS INNERIVATED BY A RAPIDLY ADAPTING AFFERENT THAT ENCODES VIBRATORY STIMULI. STILL OTHER TACTILE RECEPTORS EXTRACT OBJECT FEATURES SUCH AS OBJECT FLIPPED, HAIR MOVEMENT, SKIN STRETCH OR HAND POSITION OR SHAPES AND TEXTATURES. AND THOSE DIFFERENT QUALITIES, THEN LEAD TO DIFFERENT PHYSIOLOGICAL OUTPUT FROM THESE DIFFERENT RECEPTORS. NOW THESE ARE WHAT WE CALL GEPTLE RECEPTORS, THERE ARE NO SUSEPTERS THAT INITIATE THE SENSATION OF SLOW BURNING BANE PAIN, STINGING PAIN OR ITCH. THE QUESTION I WANT TO FOCUS ON TODAY IS HERE, HOW DO THESE TOUCH RECEPTORS PRODUCE THESE UNIQUE PATTERNS OF ACTIVITY THAT REPRESENT SPECIFIC TACTILE QUALITY. NOW WE HAVE A PROBLEM, THAT IS, THE DIVERSITY OF TOUCH RECEPTORS AND THE FACT THAT THEY'RE SCATTERED THROUGHOUT OUR LARGEST SENSORY ORGAN HAS MADE IT DIFFICULT TO STUDY THESE RECEPTORS WITH HIGH RESOLUTION PHYSIOLOGICAL APPROACHES. SO TO GET AROUND THIS OBSTACLE, MY GROUP HAS FOCUSED MUCH OF OUR EFFORT ON AN EXPERIMENTALLY TRACTABLE TOUCH RECEPTOR CALLED THE MERKL COMPLEX. THESE CLUSTER IN AREAS OF THE SKIN THAT ARE SPECIALIZED FOR HIGH TACTILE ACUITY AND THIS INCLUDES FINGERTIPS, WHISKER FOLLICLES CAN WE CAN SEE HERE AND IN THE HAIRY SKIN THESE ARE FOUND IN SPECIALIZED REGIONS CATCHED TOUCH DONE AND I'M SHOWING YOU AN EXAMPLE OF THESE IN A MOUSE TAUPE DOWN. NOW THESE COMPLEXES WITHIN THESE SPECIALIZED AREAS ARE THOUGHT TO MEDIATE FINE TACTILE DISCRIMINATION WHICH WE AS HUMANS RELY ON, FROM MANIPULATING OBJECTS AS WE ACCOMPLISH VIRTUALLY EVERY BASIC TASK, THAT WE HAVE TO ACCOMPLISH TO ENABLE INDEPENDENT LIVING. THAT INCLUDES EVERYTHING FROM FEEDING OURSELVES TO COMMUNICATING THROUGH E-MAIL OR TEXT WHICH IS OBVIOUSLY ESSENTIAL FOR MY INDEPENDENT LIVING AND FOR MY CAREER. SO THE IDEA THAT MERKEL NEURITE COMPLEXES MEDIATE THIS ACUITY COME FROM STUDIES BY KEN JOHNSON AND OTHERS THAT SHOW THAT MERKEL COMPLEXES HAVE THE HIGHEST SPACIAL RESOLUTION OF ANY MAMMALIAN TOUCH RECEPTOR. AND THAT CAN BE SEEN HERE, IN THESE ESPECIALLY EVENT PLOTS WHICH ARE--COME FROM RECORDINGS OF MERKEL COMPLEXES FOR MONKEY AND PRIMATE SKIN AND WHAT YOU CAN SEE IN THESE BRAILLE LIKE CHARACTERS IS THE SLOWLY ADAPTING AFRIP WHICH IS THE OUTPUT OF THE NEURON THAT INNERIVATES THE CELLS DOES A BEAUTIFUL JOB OF REPRESENTING THE SPACIAL FEATURES OF THESE BRAILLE LIKE CHARACTERS. BY CONTRAST ADAPTING AFRIPS SMEAR OUT THE RESPONSE--SMEAR OUT THE SPACIAL RESOLUTION OR SPACIAL PROFILES AT THESE BRAILLE LIKE CHARACTERS. MORE OVER, SA 1 A41S DO A BEAUTIFUL JOB OF REPRESENTING EDGES OF TACTILE RESOLUTION, AND YOU CAN SEE THAT HERE IN THE FIRING PATTERN AS THE GRADING IS SCANNED ACROSS THE FINGERTIP, WHERE THE RAPIDLY ADAPTING AND AFRIPS FAIL TO REPRODUCE THE SPACIAL EDGES NEAR OUR LIMIT OF TACTILE ACUITY. NOW I WANT TO EMPHASIZE HERE, THAT ALL THESE--ALTHOUGH THESE ARE CALLED SLOWLY ADAPTING AFRIPS, THEY RESPOND BEST TO A MOVING STIMULOUS AND THAT MAKES PERFECT SENSE BECAUSE AS YOU KNOW, SCANNING OUR SKIN ACROSS A SURFACE IS HOW WE PALPATE OR RECOGNIZE TACTILE FEATURES AND AS OUR FINGERTIPS MOVE CROSS THE SURFACE, IT'S THE SA 1 AFRIP SPACIAL TEMPORAL PATTERN OF ACTIVITY THAT REPRESENT THE OBJECTS, EDGES CURVEATURE AND SHAPES. SO WE CAN RECORD THE RESPONSES OF THESE SA-1 AFRIPS USING THESE NERVE PREPARATION AND I WANT TO SHOW YOU SOME OF THESE RECORDINGS AND POINT OUT A FEW FEATURES OF THE SA-1 PATTERN OF ACTIVITY THAT ARE NOTABLE. SO AT THE TOP I'M SHOWING YOU, THE SKINS REACTIVE FORCE TO A COMPRESSOR OR A SERIES OF COMPRESSIVE STIMULI AND THIS IS SHOWING SINGLE UNIT RECORDINGS FROM INNOVATING THE RECEPTIVE FIELD THAT WE'RE STIMULATING HERE. SO THAT--A RESPONSE OF THIS PARTICULAR TYPE OF TOUCH RECEPTOR, IS A BI PAYSIC RESPONSE THAT HAS AN EXTRAORDINARILY FREQUENCY DYNAMIC COMPONENT SO WHEN THE SKIN IS MOVED, THE AFRIP CAN FIRE UP TO AN INSTANTANEOUS FIRING RATE OF 1500-HERTZ. AND THEN THAT RATE IS--ADAPTS AS THE SKIN IS CONSTANTLY HELD IN AND IT ADAPTS TO A FEW 10S OF HERTZ. THIS IS ROUGH ATOM MARKABLY ROBUST. SO AS LONG AS THE SKIN IS HELD, IT WILL CONTINUE TO FIRE UP TO 10 MINUTES WHICH IS AS LONG AS WE USUALLY GIVE A SINGLE STIMULUS AND THEN WHEN THE STIMULUS IS REMOVED, THE NEURON GOES BACK TO ITS RESTING FIRING RANGE WHICH IS 0. SO THEY HAVE NO SPONTANEOUS ACTIVITY BUT A ROBUST SUSTAINED ACTIVITY THEY ALSO HAVE A HIGHLY IRREGULAR INNER SPIKE INTERVAL AND YOU CAN APPRECIATE THAT HERE BY LOOKING AT THIS HISTOGRAM OF INNER SPIKE INTERVAL, YOU CAN SEE THE SA 1 HAS A GRAD DISTRIBUTION, HERE'S A 2 ATRENT WHICH HAS A SHARP DISTRIBUTION AND WE CAN USE THAT AS A FEATURE TO DISTINGUISH AFRIPS FROM OTHER AFRIPS AND WE KNOW THAT SA 1 REQUIRE AMERICALE CELLS WITHIN THE FEEL AND WE'VE BEEN ABLE TO VERIFY THAT BY RECORDING FROM THE GFP MICE THAT ANDIE MENTIONED THAT EXPRESS GFP SELECTIVELY AND SO THIS IS LOOKING THROUGH THE TRANSPARENT EPIDERMIS AT A TOUCH TONE AND WE CAN VERIFY THAT THE SA 1 AFERENCE FIELD IS LIMITED TO THE AREA OF SKIN THAT ACTUALLY CONTAINS MERKEL CELLS AND MORE IMPORTANTLY WE SEE A KNOCKOUT MICE, WE SEE COMPLETE LOSS OF THESE AND I'LL SHOW YOU THOSE DATA LATER. SO OUR GEL IS TO DISCOVER THE BIOLOGICAL MECHANISMS THAT DICTATE THE SA 1 AFRIPS UNIQUE PHYSIOLOGICAL FIRING PATTERNS THAT I JUST DESCRIBED. SO TODAY I WILL TALK ABOUT 2 RECENT PROJECTS, AND SHOW SOME UNPUBLISHED DATA THAT ADDRESS 2 QUESTIONS, THAT THAT WE HAVE SET OUT TO ANSWER IN PURSUING THIS MAIN GOAL. THE FIRST QUESTION IS, HOW DOES THE NEURONAL ARCHITECTURE OF THE SAC1 AFRIP GOVERN THE FIRING PROPERTIES. SECOND, I'LL GIVE, JUST AN OVERVIEW OF OR TASTE OF OUR EFFORTS TO FIGURE OUT THE ROLE OF THE DERMAL MERKEL CELLS IN TOUCHING. SO TO ADDRESS THE FIRST QUESTION, WE TEAMED UP WITH GREG GUREMARKS LING, TO DEVELOP A TACTILE ENCODE NOTHING THE SAC1 ATRENT. NOW THIS IS A COLLABORATIVE GRANT, COLLABORATIVE PROJECT THAT'S FUNDED THROUGH THE COLLABORATIVE--CRCNS, COLLABORATIVE RESEARCH AND COMPUTATIONAL NEUROSCIENCE THAT'S FUNDED THROUGH NINDS. SO AS A FIRST STEP TO DEVELOPING A QUANTITATIVE UNDERSTANDING, GREG'S GROUP BUILT A NETWORK MODEL THAT CONSISTS OF A FINITE ELEMENT MODEL, TISSUE MECHANICS THAT TAKES DISPLACEMENT AND FORCE DATA FROM OUR EXVIVO SKIN NERVE PREPARATION RECORDING AND THEN CONVERTS THAT INTO STRAIGHT ENERGY DENSITY, AT THE SITE OF MERKEL SITE COMPLEXES. THAT GOES THROUGH A TRANSDUCTION FUNCTION AND CONVERT THIS IS STIMULUS INTO A RECEPTOR CURRENT THAT THEN GOES INTO A NEURAL DYNAMIC MODEL, TO PREDICT SPIKE TIMES SO WHAT WE CAN DO IS USE DATA FROM OUR RECORDINGS. FEED THAT INSTATE REGULATOR MODEL AND THE MODEL PREDICTS BY TIME WHICH WE CAN QUANTITATIVELY COMPARE TO THE OUTPUT OF SAC1 AX FRIPS FROM OUR MOUSE BIOLOGICAL RECORDINGS. AND AN INITIAL SUBSTANTIATION OF THE MODEL, ELRINE. KIM WHO WAS A GRADUATE OPPORTUNITY IN THE LAB COMPARED THE MODELS OUTPUT TO SA-1 RESPONSES OVER A VARIETY OF STIMULUS MAGNITUDES AND STIMULUS RATES. AND HERE YOU CAN SEE THE BIOLOGICAL OUTPUT IN MAGENTA AND THE MODEL OUTPUT IN YELLOW AND WHAT YOU CAN SEE IS THAT FOR THESE 2 PHYSIOLOGICAL FIRING PROPERTIES, THE MODEL DOES A GOOD JOB OF PREDICTING DYNAMIC AND STATIC FIRE RATES OVER THIS RANGE OF MAGNITUDES AND STIMULUS RATES AND WHEN WE LOOK AT MORE DETAIL, WE CAN LOOK AT THE RESPONSES OF THE MODEL TO 2 DIFFERENT STIMULUS MAGNITUDES AND I HOPE YOU CAN SEE THAT AT THIS LIGHT LEVEL. SO WHAT YOU CAN SEE OR WHAT YOU CAN HOPEFULLY QUALITATIVELY APPRECIATE S&P THAT THE MODEL DOES A GOOD JOB OF PREDICTING AN ONSITE RESPONSE SO YOU HAVE EYE HIGH FIRING RATE AT THE ONSET OF STIMULUS AND IT DOES A REMARKABLY GOOD JOB AT PREDICTING THE RATE OF ADAPTATION AND WHAT WE'VE FOUND FROM OUR MODELS IS THAT THE ADAPTATION RATE IN THIS TOUCH RECEPTOR IS DOMINATED ALMOST COMPLETELY BY SKIN MECHANICS. BUT WHAT THE MODEL DOES A MISERABLE JOB AT PREDICTING IS THE VARIABLE INNER SPIKE INTERVAL SO YOU CAN SEE HERE THAT THOSE ACTION POTENTIALS ARE QUITE REGULARLY FACED AND IT CANNOT PREDICT FIBER TO FIBER DIFFERENCES SO ANY TIME WE PUT IN THIS FORCE, WE GET THIS PREDICTED FIRING PATTERN. WHAT WE SEE IN MOUSE SAC1 UNITS AND OTHER PEOPLE HAVE REPORTED IN THE OTHER SPECIES AS LIS THAT SAC1 APRINTS ACTUALLY QUITE DRAMATICALLY IN THEIR RESPONSE PROPERTIES TO TOUCH. SO HERE I'M SHOWING DISPLACEMENT RESPONSE RELATIONS FOR 4 DIFFERENT SAC1 AFRIPS AND WHAT I WANT TO POINT OUT IS THAT THE SENSITIVITY OF THE APRINT, THAT IS THE SLOPE OF THE DISPLACEMENT RESPONSE CURVE IS DIFFERENT SO 2 OF THESE AFFERENTS HAVE DEEP RESPONSES AND 2 HAVE SHALL O DISPLACEMENT RESPONSES AND THESE ARE QUITE REPRESENTATIVE OF RECORDING THAT WE SEE THIS OUR PREPARATION. SO OUR FIRST--SO THE--THE OTHER THEN I WANT TO POINT OUT HERE IS THAT THESE DIFFERENCES IN SENSITIVITY, ARE NOT A FUNCTION OF SKIN MECHANICS INTRINSIC TO THE NEURON AND WE KNOW THAT BECAUSE WE MEASURE 4S AS WE DISPLACE THE SKIN AND THE SKIN MECHANICS FOR THESE FIELDS WERE HAVE VIRTUALLY IDENTICAL. SO OUR FIRST HYPOTHESIS WAS THAT THE SENSITIVITY OF THESE WOULD BE SET BY THE NUMBER OF MIRKLES IN THE--MERKELS, IN THE RESUPPORTOR FIELD. THIS IS QUITE SIMPLE. THE IDEA IS FOR A SUBMAXIMAL STIMULATION, MORE TRANSDUCTION UNITS WILL GIVE RISE TO HIGHER FIRING RATES BECAUSE THEY'LL BRING THE NEURON TO THRESHOLD FASTER. SO BECAUSE WE CAN COUNT THE NUMBER OF MERKEL CELLS WITHIN THE NUMBER AS WE'RE RECORDING WE WERE ABLE TO TEST THAT HYPOTHESIS AND WE SAW THAT WAS COMPLETELY WRONG. SO 1 OF THESE VERY SENSITIVE AFFERENTS HAS 12 MERKEL CELLS AND 1 OF THE INSENTATIVE HAS 20 MERKEL CELLS. SO WE NEXT HYPOTHESIZED THAT IT'S NOT THE--JUST THE NUMBER OF MERKEL CELLS OR COMPLEXES BUT RATHER THE ARRANGEMENT OF COMPLEXES WITHIN THE ARBOR, THAT DICTATES ITSELF. SO TO TEST THIS HYPOTHESIS, WE SET OUT TO RECONSTRUCT, COMPLETELY RECONSTRUCT SA AFFERENT MARKERS. SO WE FIRST HAD TO IDENTIFY A MARKER TO ALLOW US TO VISUALIZE AND COULD YOU RECOLLECT THE NUMBER OF NODES WHICH IN TACTILE ARE THE SALES OF SPIKE INITIATION AND NODES WHICH ARE THE SITES OF SPIKE INTEGRATION AND PROPAGATION. SO MY STUDENT BLAIR JENKINS USING CONFOCAL MIRROR MICROSCOPY WAS ABLE TO FICIALIZE THE SITE OF MYELIN END POINTS ON THE AFREERENTS. SO THIS IS--THIS HAS BEEN THE SIDE OF THE HEMINODE AND SHE DID THAT WITH MYELIN AND BASIC PROTEIN. AND HE COULD VISUALIZE GAP IN THE MYELIN SHEET, WHICH SHE THOUGHT--BUT SHE THEN OBSERVED THAT NAB 1.6 WHICH IS THE PREDOMINANT SODIUM CHANNEL AT PERIPHERAL NODES OF BA LOCALIZE TO THESE END POINTS AND GAPS AND WHEN SHE QUANTIFIED THESE DATA SHOW FOUND THAT MORE THAN 95% OF HEMINODES OR MILEN END POINTINGS WERE MARKED BY NAB 1.6 AND A HUNDRED% WERE MARKED MY 1.6. SO THIS GIVES US THEN, 2 WAYS OR 2 MARKERS THAT WE CAN USE TO VISUALIZE AND QUANTIFY MYLENSMAZE NODE. MY STUDENT CAROLYN USED THESE MARKERS WITH NF2 HUNDRED TO VISUALIZE THESE THEMSELVES AS WELL AS A MARKER FOR MERKEL CELLS WHICH IS KERATIN 8 AND SHE PERFORMED COMPLETE RECONSTRUCTION IN TAXIN. SO HERE I'M SHOWING YOU RECONSTRUCTION WITH MERKEL CELLS IN BLUE, AFFERENTS IN RED AND THE MYELIN SHEET SHOWN IN GREEN AND HERE YOU CAN SEE A GAP THAT REPRESENTS THE NODE AND HERE YOU SEE THE END POINTS THAT HEPATITIS REPRESENT THE NODES. WHEN SHE TOOK THESE TO ELUC EDUCATIONALLA, MORE THAN 200 MICROMETERS FROM THE SITE OF CONTACT AND WITH AMERICA ERKEL CELLS IN THE EPIDERMIS, AND BACK TO THE DRURCHG. WHAT CAN YOU SEE IS THAT THIS TOUCH STONE WITH THE CLUSTER OF 17 MERKELEX CELLS IS INNERIVATED BY A SINGLE AFFERENT THAT BRANCHES OVER THE ORDERS TO PRODUCE 21 BRANCHES WITH 4 HEMINODES SO WITH 4 SITES OF SPIKE INITIATION. WHEN WE--HERE I WILL SHOW YOU A SECOND EXAMPLE THAT RESOLES AN UNEXPECTED LEVEL OF COMPLEXITY IN THE AFFERENT. SO THIS IS A TOUCH TONE WITH A FEW CELLS, 23 MERKEL CELLS AND AGAIN WE CAN SEE THE NODES AND THE HEMINODES AND UPON FIRST EXAMINATION, IT LOOKS LIKE THIS--THIS CLUSTER OF CELLS IS INNERIVATED BY AN AFFERENT WITH 2 MAJOR BRANCHES AND 1 MINOR BRANCH THAT PROJECTS UP TO THE MIDDLE OF THE CLUSTER. WHEN CARARECONSTRUCTED THIS, SHE FOUND THAT THEY CONVERGE INTO A TYPICAL 1 SA-AFFERENT AND THAT CENTER BRANCH ACTUALLY PROJECTS TO A SMALLER AND INTO THE MIDDLE OF CLUSTER AND CONTACTS 2 OF THESE 23 MERKEL CELLS, SO WE HAVE 21 INNERIVATED BY WHAT WE WOULD THINK OF AS AN A-BETA AFFERENT AND WHAT MORPH LOGICALLY LOOKS LIKE A DELTA AFFERENT. SO THESE DATA SUGGEST THAT THERE ARE--THERE IS A DIFFERENT CLASS OF AFFERENTS WHOSE ROLE AND TOUCH IS COMPLETELY UNKNOWN. SO SHE THEN PERFORMED ANALYSIS AND SHOW TOUCHED ON THE SINGLE AFFERENT THAT REPRESENTS THE VAST MAJORITY OF TOUCH TONES THAT WE OBSERVED AND SHE FINDS THAT THE STRUCTURE OF THESE SA-1 AFFERENTS ARE DIVERSE, EVEN THOUGH THESE ARE WHAT WE WOULD THINK OF AS A SINGLE CLASS OF TOUCH RECEPTORS, WE SEE THAT IN ADULT SKIN, THE NUMBER OF MERKEL CELLS VARYYS ALMOST 5 FOLD AND CORRESPONDINGLY, WE SEE A LARGE RANGE OF TOTAL NUMBER OF BRANCHES BUT WHEN KARA BROKE THOSE UP AND COMPARED MILENNATED TO UNMYELENNATED, PROJECTIONS THAT ARE FOUND JUST PROXIMAL TO THE EPIDERMIS, SHE SEES THAT MOST OF THE VARIATION, COMES IN THE UNMYELINNATED NEURONS, THAT'S THE BRANCHES THAT ALMOST INVARIANT AMONG TOUCH STONES. AND AS A RESULT THE NUMBER OF HEMINODES IS QUITE CONSTANT ACROSS TOUCH TONES. NOW BECAUSE THE NUMBER OF CELLS CHANGES DRAMATICALLY, THE NUMBER OF HEMINODES IS QUITE CONSTANT, WHAT THIS MEANS IS THAT THE GROUPING, OF CELLS TO HEMINODES, CHANGES QUITE BROADLY, BOTH BETWEEN TOUCH TONES AND AS WELL AS WITHIN A SINGLE TOUCH TONE. SO FOR EXAMPLE, THE FIRST TOUCH TONE I SHOWED YOU HAD 17 MERKEL IN GROUPINGS OF 8, 5, 3 AND 1 CELLS PER HEMINODE. I SHOULD SAY MERKEL COMPLEXES FOR HEMINODE. SO THEN, IN COLLABORATION WITH GREG, WE MODELED THIS COMPLEXITY TO ASK COMPUTATIONALLY DOES THE GROUPING OF THE CELL COMPLEXES TO HEMINODE MATTER, SO THE WAY THAT THEY DID THIS, WHO WAS A GRADUATE STUDENT IN GREG'S LAB WHO GRADUATED LAST WEEK, ACTUALLY, HE CREATED A NETWORK MODEL, A RECONFIGURABLE NETWORK MODEL WHERE EACH CLUSTER IN THE RIGHT COMPLEXES, IS REPRESENTED AS INDEPENDENT TRANSDUCTION UNIT THAT COUPLES TO A HEMINODE. WHICH IS A NEURAL DYNAMIC MODEL AND THIS IS THE MODEL CONFIGURATION FOR THAT 17 TOUCH TONE AFFERENT THAT I SHOWED YOU. WITH THIS IT MODEL, DANE IS ABLE--WAS ABLE TO RECAPITULATE ALL THE KEY FEATURES OF THE SAWOEVER-1 FIRING PROPERTIES AND I WILL SHOW YOU THIS QUALITATIVELY HERE, BY SHOWING YOU 2 EXAMPLES OF OF RECORDINGS THIS, IS THE AFFERENT, STIMULATED AT 2 DIFFERENT DISPLACEMENT MAGNITUDES AND THIS IS THE OUTPUT OF A MODEL, THAT IS DISPLACED AT SIMILAR MAGNITUDES AND YOU CAN SEE THAT THE MODEL HAS A HIGH FIRING RATE, AT THE DYNAMIC PHASE AND HAS A SUSTAINED BUT VARIABLE FIRING RATE DURING THE SUSTAINED PHASE AND IT HAS INCREASING FIRING WITH INCREASING DISPLACEMENT MAGNITUDE. NOW YOU MIGHT BE NOTING HERE THAT THE FIRING RATE IN THE MODEL IS LESS THAN IN THIS PARTICULAR EXAMPLE AND THAT'S BECAUSE WE FIT THE MODEL TO THE AVERAGE OF A POPULATION OF SA-1 AFFERENTS AND THIS HAPPENS, THIS FIRING RATE HAPPENS TO FALL ABOVE THAT MEAN POPULATION RESPONSE. SO THEN THEY USE THIS BASE MODEL TO COMPUTATIONALLY MOVE THE CELLS AROUND IN THE ARBOR TO ASK IF THE GROUP GROUPING OF THE CELLS MATTERS AND WITH A DOTTED LINE SHOWING THE BASE RESPONSE, THIS IS THE BEST FIT OF THIS 17 MERKEL COMPLEX ARBOR TO THE MEAN POPULATION DATA FROM THE SA-1 RECORDINGS AND HE THEN DID A SIMPLE EXPERIMENT OR COMPUTATIONALLYICISMEM EXPERIMENT THAT WOULD BE IMPOSSIBLE TO DO BIOLOGICALLY AND THAT IS HE MOVED TO THOSE CELLS TO THE BIG GROUP. SO HE TOOK THEM AND MOVED THEM TO THE BIG GROUP AND WHAT HE SAW IS THAT THE SENSITIVITY OF THE AFFERENT TO TOUCH, SIGNIFICANTLY INCREASED, SIMPLY BY MOVING TO MEARE, KEL CELLS AX ROUND. HE THEN DID THE CONVERS EXPERIMENT AND TOOK 2 AND MOVED IT TO THE SMALLEST CLUTTER AND SHOWED THAT THE PREDICTED FIRING--PREDICTED SENSITIVITY TO TOUCH IS CORRESPONDINGLY DECREASED. SO OUR CONCLUSION FROM THESE COMPUTATIONAL EXPERIMENTS IS THAT THE INTRUSION OF MERKEL COMPLEXES WITHIN AN ARDOR ACCOUNTS IN PART FOR THE DIFFERENCES IN TOUCH SENSITIVITY THAT WE OBSERVE BIOLOGICALLY. MORE OVER DANE'S SIMULATIONS SUPPORT OUR WORKING HYPOTHESIS, THAT FIRING RATE SHOULD INCREASE AS MEARE, KEL AND THE RIGHT COMPLEXES ARE ADDED TO THE ARBOR. BUT IT'S NOT THAT SIMPLE. WHAT HE DID IN THIS COMPUTATIONAL EXPERIMENT IS TAKE A BASE ARBOR AND ADD MERKEL COMPLEXES 1 AT A TIME TO THE ARBOR BUT HE ADDED THEM UNDER 2 STRATEGIES, 1 STRATEGY TO EQUALIZE THE NUMBER OF MERKEL COMPLEX AND NODES AND THE OTHER TO MAXIMIZE THE DEFICIENCIES IN THE COMPLEXES AND WHAT HE SAW IF YOU CAN COMPARE THIS POINT HERE IS BY ADDING 4 MERKELCELLS BY DISTRIBUTING 4 MERKEL CELLS BETWEEN THE NODES, THE PREDICTED FIRING RATE FOR THE AFFERENT IS ESSENTIALLY THE SAME. SO ADDING 4 MERKEL CELLS BUT ADDING THEM ACROSS THE NODES HAD NO EFFECT ON FIRING RATES. WHEREAS IF HE TOOK THOSE, AND INSTEAD ADD THEM TO THEA SINGLE HEMINODE IS NOT THE BIGGEST, HE SAW A DOUBLING IN FIRING RATE. SO THESE DATA SAY, THAT IT'S THE POSITION AS MUCH AS THE NUMBER OF TRANSDUCTION UNITS THAT AFFECTS THE FIRING PROPERTY. NOW HE SHOWED THAT THIS GENERALIZES TO OTHER ARBORS BY BUILDING ADDITIONAL MODELS WHOSE ARBOR CONSIDERATIONS SPAN THE RANGE THAT WE OBSERVED BIOLOGICALLY SO HE CHANGED THE NUMBER OF HEMINODES AND THE CHANGED THE NUMBER OF CELLS ACROSS THE RANGE WE OBSERVED AND YOU SEE THE SAME BASIC CONCLUSIONS APPLIED ACROSS THESE DIFFERENT MODELS FOR ARBORS. SO HE THEN ASKED IN 1 FINAL COMPUTATIONAL EXPERIMENT, CAN YOU BUILD OR COULD HE BUILD ARBORS THAT RECAPITULATE THE DATA THAT WE OBSERVED BIOLOGICALLY, WHERE A SMALL CLUSTER OF MERKEL CELL COMPLEXES GIVE RISE TO AN AFFERENT TO A LARGE INDOOR AND THAT'S WHAT HE SAW. SO BY TAKING 12 MERKEL CELLS AND CLUSTERING MOST OF THOSE IN A SINGLE HEMINODE, HE WAS ABLE TO PREDICT FIRING RATES THAT ARE MUCH MORE SENSITIVE, SO BOTH FIRING RATE AS HIGHER AS WELL AS THE MECHANICAL SENSITIVITY, IS HIGHER FOR THE SMALL SA-1 AFFERENT ARBOR COMPARED TO LARGER ARBOR WHERE TRANSDUCTION AUTOPSY SERIESS ARE DISTRIBUTED EQUALLY AMONG HEMINODES. SO THESE DATA SUGGEST THAT TOUCH RECEPTORS WILL BE MORE SENSITIVE WHEN TRANSDUCTION UNITS ARE CLUSTERED AT INDIVIDUAL HEMINODES WHICH IS WHAT WE OBSERVED BIOLOGICALLY. SO I WANT TO SUMMARIZE THIS FIRST PART OF THE TALK BY JUST SUMMARIZING WHAT I JUST TOLD YOU. FIRST I'VE SHOWN THAT MAMMALIAN TACTILE AFFERENTS CONTAIN MULTIPLE HEMINODES CAPABLE OF SERVING AS SIGNS OF SPIKE INITIATION, SECOND WE FOUND WITH OUR EELECTRICITY ROUGH ATOM PHYSIOLOGY AND OUR QUANTITATIVE MORPH ORDER OF MICRONSETRY THAT THEY DISPLAY A SURPRISING DEGREE OF VARIABILITY IN NEURONAL ARCHITECTURE AND PHYSIOLOGICAL RESPONSE TO TOUCH. AND OUR MODELING PREDICTS THAT THE DISTRIBUTION OF TRANSDUCTION SITES, AMONG SPIKEIN INITIATION ZONE IS A KEY FEATURE THAT GOVERNING MECHANICAL CODING AND AND TACTILE RECEPTORS. I'D NOW LIKE TO TURN TO THE SECOND QUESTION, THAT I INTRODUCED AND THAT IS WHAT IS THE ROLE OF MERKEL CELLS IN TOUCH RECEPTION? BASED ON THE COMPLEXES MORPHOLOGY, THESE ARE MECHAN O SENSE RESILIENCE SEPTORSOR CELLS IN THE SKIN MUCH AS HAIR CELLS SERVE AS RECEPTORS IN THE INNER EAR. IN THIS MODEL TOUCH WHICH HAPPENS AT THE SURFACE OF THE SKIN UP HERE PROP GATES THROUGH THE SKIN AND SOMEHOW DEFORMS THIS CELL SURFACE SO 1 COULD IMAGINE, 1 THING WE LIKE TO IMAGINE IS THAT THAT DEVELOPMENTAL ENDOCRINOLOGY ORATION MIGHT BE AT MICROVILLY WHICH MERKEL CELLS HAVE, THEY HAVE ABOUT 50 VILLI, THAT PROTRUES INTO THE KEROTIN O SIGHTS WHICH MAKE THE BULK OF THE EPIDERMIS AND THESE MICROVI HAVE LIE HAVE TIGHT--VILL LIE, AND THESE ARE DISPLACED AND THAT OPENS MECHAN O SENSITIVE CHANNELS WHICH THEN LEADS TO DEPOLARIZATION OF THE CELL'S MEMBRANE WHICH WOULD LEAD TO CHANGES IN THE OPENING VOLTAGE ACTIVATED CALCIUM CHANNELS ALONG THE MERKEL SURFACE WHICH CAN THEN STIMULATE SYNAPTIC RELEASE TO SET UP THE ACTION POTENTIAL CHANGE THAT WE OBSERVE ON IN OUR EXVIVO RECORDING. NOW 1 CAN ENVISION MORE COMPLICATED MODELS TO EXPLAIN SENSORY TRANSDUCTION IN THIS COMPLEX, FOR EXAMPLE, IT COULD BE THAT THE MERKEL CELL OR THAT THE NERVE ITSELF IS THE MECHAN O SENSORY CELL AND THE MERKEL IS PLAYING AN ACCESSORY ROLE EITHER BY PROVIDING TROPEIC SUPPORT TO THE SAC1 AFFERENT OR BY RELEASING NEUROACTIVE MOLECULE TO CONTROL THE SENSITIVITY OF THE NEURON. IT'S ALSO POSSIBLE THAT MERKEL CELLS ARE BOTH MECHAN O SENSITIVE CELLS AND THEY EACH CONTRIBUTE TO 1 PHASE OF THIS BI PHASIC RESPONSE THAT I'VE TALKED ABOUT EARLIER. AND THESE ARE ALL MODELS THAT HAVE BEEN WIDELY DEBATED IN THE FIELD. WE A NUMBER OF YEARS AGO SET OUT TO TEST THE HYPOTHESIS, AND WE AND OTHERS HAVE GENERATED SEVERAL LINES OF COMPELLING BUT INDIRECT EVIDENCE THAT SUGGESTS THAT MERKEL CELLS MIGHT PLAY A SENSORY ROLE AND THESE AGAIN ARE DATA NOT FROM MY GROUP OF DATA FROM OTHER GROUPS THAT HAVE BEEN IN THE LITERATURE FOR DECADES, SO ULTRA STRUCTURAL ANALYSIS, SUGGESTS THAT THERE ARE PUTATIVE PREAND POST SYNAPTIC DENSITIES AT SITES OF CONTACTS AND SENSORY NEURONS. WE SHOWED SEVERAL YEARS AGO, THAT MERKEL CELLS EXPOSE DOZENS OF RELEASE MOLECULES THAT ARE ESSENTIAL FOR SYNAPTIC RELEASE IN THE NEURONAL SYNAPSE SIS AND THE COMPLEX PROTEINS YOU WOULD EXPECT AND ACTIVE SIGN OF MATRIX, PICOLOU, AND GLUTEA MATE TRANSPORTERS SUCH AS THE GLUTEA MATE TRANSPORTER THAT SUGGESTS THAT THESIS CELLS MIGHT MAKE SENSES WITH SENSORY AFREERENT WE WE SEE THAT THEY HAVE CALCIUM CHANNELS AND HERE I'M SHOWING YOU CALCIUM IPT GREATERRAGES OF A FIELD OF GFP EXPRESSING CELLS, IMAGES WITH RADIO METRIC CALCIUM IMAGES AND WHEN YOU DEPOLARIZE THESE CELLS WE SEE MORE THAN 90% OF THESE CELLS HAVE ROUGH ROBUST RESPONSES AND WE DO WHOLE CELL RECORD AND THEY'RE LTYPE AND PK AND MORE OVER, IN PRELIMINARY EXPERIMENT SHOWN THAT THESE PURIFIED CELLS ARE INTRINSICALLY TOUCH SENSITIVE AND I'LL SHOW YOU 1 EXAMPLE OF THIS AFTER 3 OR 4 DAYS IN CULTURE, STIMULUS PROBE THAT IS RUESED TO IN THIS CASE, FIRST STIMULATION TO SHOW THAT IT'S A HEALTHY CELL AND THEN YOU CAN SEE WHEN THIS PROTRUSION IS DISPLACED BY AS LITTLE AS A COUPLE OF MICROMETERS THAT THEN SPREAD THROUGHOUT THE CELL THOSE MIGHT BE TOUCH SENSITIVE CELLS. BUT WHAT THESE DO NOT ADDRESS SO THEY SAY THAT MERKEL CELLS ARE INCAPABLE OF RELEASING THE TRANSMITTERS AND INCAPABLE TRANSDUCING MECHANICAL FORCE INTO ELECTRICAL SIGNALS BUT THEY DON'T TELL US WHETHER OR NOT THEY'RE NECESSARY FOR THE RESPONSES. SO TO ADDRESS THIS QUESTION, WE TEEMED UP TO ANALYZE A MOUSE THAT LACKS ATO-1 IN THE SKIN. SO IN THIS MOUSE, IT'S AN ATOH1 KNOCK OUT. AND WE FOUND THAT THESE MICE COMPLETELY LACK MERKEL CELLS. SO THESE ARE IN CONTROL MICE, YOU CAN SEE THE MERKEL CELLS HERE AND MAKING CONTACT WITH THE AFERENT, SHOCKING TO ME THEIR TOUCHDOWNS ARE INNERIVATED STILL MILENNATED AND WHICH SAYS IN PRINCIPLE THEY'RE CAPABLE OF GENERATING ACTION POTENTIALS SO WE ASK, DO SHE'S AFFERENTS GIVE RISE TO SAC1 RESPONSES AND WHAT WE SAW WHEN WE LOOKED UP AN AGGREGATE ACROSS THE POPULATION, WE SEE THAT THE RESPONSES OF THESE LOOK VERY NORMAL, VERY COMPARABLE TO WILD-TYPE. SO THIS IS A CUMULATIVE PLOT SHOWING THE FRACTION OF NEURONS RESPONDING AT DIFFERENT FORCES AND YOU CAN SEE THAT OVERALL THE TOUCH SENSITIVITY OF THESE IS PERFECTLY NORMAL. WE ALSO SAW THAT THE DISTRIBUTION OF FIBERS CLASSIFIED BY INDUCTION VELOCITY IS QUITE NORMAL. SO FIBERS GENERALLY TACTILE AFFERENTS, ADELTA AND C-FIBERS INCLUDE NO SUSEPTORS AND HAIR RECEPTORS THAT SO RECEPTORS THAT INNERIVATE HAIR FOLLICLES. SO THIS WAS A GOOD CONTROL BECAUSE WE EXPECT IN A MERKEL KNOCK OUT WOULD HAVE DEFICITS IN THE SAC1 KNOCK OUTS AND NOT TOUCH SENSITIVITY SO THAT'S WHAT WE SAW. NO GENERAL DIFFERENCE. BUT WHEN WE FOCUSED ON THESE ABETTA AFFERENTS WE FOUND THAT IN WILD-TYPE OR CONTROL MICE, THESE 20% OF THESE AFFERENTS OR SAC1 BASED ON FIRING PROPERTIES AND WHEN YOU BLIND THE DATA WE FOUND THAT THAT CLASS OF AFFERENTS IS COMPLETELY MISSING IN THE KNOCKOUT MICE AND THE OTHER TYPES AFFER EPTS AND RAAFFERENTS EXPAND PROPORTIONALLY, SO THIS SUGGESTS THAT THE SAC1 POPULATION IS DROPPING OUT OF THE AFFERENT POPULATION BECAUSE THEY'RE NONAPOPTOTIC LONGER TOUCH SENSITIVE. SO THESE DATA CONFIRM HYPOTHESIS, THE MERKEL ARE NECESSARY FOR SAC1 RESPONSES. SO NEXT QUESTION IS ARE MERKEL CELLS SUFFICIENT TO DRIVE SPIKE FIRING IN SAC1 AFFERENT. BECAUSE IF OUR HYPOTHESIS IS CORRECT AND MERKEL ARE MECHAN O SENSORY CELLS, THEY MUST--IT'S ALMOST CERTAIN THEY WOULD MAKE EXCITATORY SYNAPSES WITH THE SAC1 AFFERENT. SO TO TEST THIS QUESTION, WHAT WE ARE BEGUN TO DO IS TAKE AN OPTICAL IMAGES O GENETIC APPROACH AND WHAT WE WOULD LIKE TO DO IS EXPRESS AND SELECTIVELY EXPRESS IT IN CELLS IN THE SKIN OR AFFERENTS AND THEN SHINE LIGHT ON THE SKIN IN OUR INTACT EXVIVO SKIN NERVE PREPARATION. IF THE LIGHT ALONE IS SUFFICIENT TO DRIVE THE SPIKE FIRING IN THE AFFERENT. IF THEY'RE NOT EXCITATORY, IF THEY'RE MAD LATTERY, PLAYING A PASSIVE ROLE AS A PASSIVE MECHANICAL FILTER THAN WE WOULD EXPECT THAT SHINING LIGHT ON THE SKIN WOULD LEAD TO NO FIRE NOTHING THE AFFERENT. NOW THIS IS AN IMPORTANT EXPERIMENT BECAUSE WE CANNOT PROVIDE MECHANICAL STIMULI TO MIRACLE CELLS, AND THEY'RE ALSO STIMULATING AFFERENT BECAUSE AS CAN YOU SEE IN THIS MICROGRAPH, MIRKLE CELLS MAKE INTIMATE CONTACTS WITH THESE AFFERENTS, SO THESE ARE IN MOST CASES THEY'RE LARGE CONTACTS THAT ARE ALMOST LIKE CONTACTS SO THEY'RE NOT SAYS LITTLE BUTTON LIKE CONTACTS. SO THIS IS WHY WE USE THE OPTICAL IMAGES O GENETIC APPROACH AS OPPOSE TO SELECTIVELY TOUCH THE MIRKLE CELL SO MY POST DOC CSR HAS MANAGED TO CREATE THE MOUSE, BAYOUSING A CREE THAT DRIVES SELECTIVE EXPRESSION OF GENES IN MERKEL CELLS AND CROSSING THAT WITH A REDOB SIN MOUSE, AND WHAT YOU CAN SEE HERE, THIS IS A WHOLE MOUNT AND YOU CAN SEE THE CELLS RETREAT BRIGHTLY. AND YOU CAN SEE THE CHANNEL REDOPSIN CAN BE VISUALIZED IN THE MICRO VILLI, SO WE'RE GETTING A LOT OF PROTEIN IN THE PLASMA MEMBRANE AND YOU CAN ALSO SEE THAT IT'S QUITE SELECTIVE FOR THE AMERICALE CELLS, THERE'S NO CHANNEL REDOBSIN THAT WE CAN SEE EXPRESSED IN THE SAC1 AFFERENT. SO SIR JOHN THEN DID THE EXPERIMENT IN INTACT SKIN AND HERE I'M SHOWING YOU A FLUORESCENT MICROGRAPH TAKEN WITH THE STEREO SCOPE THAT ON THE SKIN AND YOU CAN SEE IT'S A VERY LOW MAG NI5ICATION IMAGE AND EACH OF THESE DOTS REPRESENTS A TESTIFY TONE THAT HAS A CLUSTER EXPRESSING CHANNEL REDOPSIN AND YOU CAN SEE HOW BROADLY DISTRIBUTED THEY ARE AT THIS BODY SITE AND HE THEN STIMULATED A PATCH OF THE SKIN BY SHINING BLUE LIGHT ON A PATCH OF SKIN THAT CONTAINED A COUPLE OF TOUCH TONES AND HE SAW SPIKE SPIRING THAT CORRELATES WITH THE TIMING ON ONSET OF LIGHT, SO LIGHT ONSET AND OFFSET, SO HERE SHE'S SHOWING YOU HERE WITH SPIKE SORTING 1 UNIT THAT IS MARKED IN RED AND ANOTHER AUTOPSY SERIES THAT HAS A SMALLER ACTION POTENTIAL SHOWN HERE IN GREEN. AND YOU SEE THOSE UNITS FIRE, WHEN THE LIGHT IS ON AND THEY DON'T FIRE WHEN THE LIGHT IS OFF. >> HE THEN USED A TOUCH TONES WITHIN THE RECEPTIVE FIELD AND HE SAW THAT TOUCHING 1 TOUCH STONE, ELIAISONSITIED SPIKES WITH THE SMALL ACTION POTENTIAL AND TOUCHING ANOTHER TOUCH TONE, ELIAISONSITIED SPIKES THAT HAVE A LARGE ACTION POTENTIAL. AND THEN COMPARED THE ACTION POTENTIAL FOR THE BY LIGHT AND BY TOUCH, SHOWN HERE AND WHEN HE OVERLAID THOSE SPIKE SHAPES HE SHOWED THAT THEY MATCH EXSEATINGLY WELL SO WHAT'S SHOWN IN COLOR IS A POINTS ALONG THE SPIKE WHERE THE LIGHT OF ECOSYSTEMS SPIKE AND THE TOUCH LINES UP SO FROM THIS ANALYSIS WE CAN SAY THAT LIGHT IS ACTIVATING THE SAME UNIT THAT THE TOUCH IS ACTIVATING AND I GO BACK AND WHAT YOU CAN SEE IS THAT THE RESPONSES ARE SLOWLY ADAPTING TYPE 1 RESPONSES SO WE CAN TELL THIS BASED ON PHYSIOLOGICAL FEATURES I DESCRIBED EARLIER. SO THE NEXT THING IS ANALYZE THE FIRING PROPERTIES OF THESE IN THE STATIC OR SUSTAINED PHASE AND WHAT HE SAW IS THAT THE REDOPS SIN, THE LIGHT EVOKED FIRING PATTERNS ARE REMARKABLILY VARIABLE JUST LIKE WE OBSERVE IN SAC1 RESPONSES SO HERE HE'S SHOWING THE ININSIDE INTERVAL DISTRIBUTION FOR WHAT WE CONSIDER THE SUSTAINED FACE OF THESE LIGHT EVOKED RESPONSES AND YOU CAN SEE THAT THE ISI DISTRIBUTION MATCHES EXTREMELY WELL TO A TOUCH OF EVOKED RESPONSES FROM SAC1 AFFERENT AND THE OTHER THING YOU MIGHT NOTICE, IS THAT THERE DOESN'T SEEM TO BE A DYNAMIC PHASE TO THESE LIGHT OF OAK RESPONSES. SO FROM THESE DATA THESE SPECULATE THESE CELLS ARE INITIATING THE SUSTAINED PHASE OF THE SAC1 RESPONSE, AND ARE UNLIKELY TO BE INITIATING THAT DYNAMIC INITIAL VERY FAST PHASE OF THE SAC1 RESPONSE. SO I'LL SUMMARIZE THE DATA FROM THE SECOND PART OF MY TALK. I'VE SHOWN YOU PRELIMINARY DATA FROM NELSON IN MY GROUP THAT THE CELLS ARE TOUCH SENSITIVE CELLS, USING MOUSE MODELS AND INTACT RECORDINGS WE'VE DEMONSTRATED THAT THESE CELLS ARE NECESSARY OF ESSAY RESPONSES AND USING AN OPTICAL IMAGES O GENETIC APPROACH, WE DEMONSTRATE THAD THE ACTIVATION OF THE MERKEL CELLS ARE IS DRIVE BY FIRING AND AFFERENTS AND SPECULATE BASED ON THESE DAT AT AMERICALE CELL ACTIVATION IS LIKE TOW MEDIATE THE STATIC PHASE OF THE SAC1 RESPONSE. I WOULD ALSO LIKE TO TAKE A MEMORY CLONE TONIGHT ACKNOWLEDGE THE PEOPLE WHO CONTRIBUTED TO THIS WORK. TODAY I'VE SHOWN YOU MORPHOMETRIC DATA FROM CAROL MARSHAL, A GRADUATE STUDENT IN THE LAB. THE WORK ON THE ISOLATED MERKLEX EL CELLS AND IT'S NOW TAKEN OVER BY MARASHI, NAKATANI, AND THEN BOB'S WORK WHO I DIDN'T SHOW TODAY IS LOOKING AT SAC1 AFFERENTS IN THE MOUSE SKIN. THIS WAS DONE AT THE UNIVERSITY OF VIRGINIA, TODAY, AND THAT WORK IS SUPPORTED THROUGH THE CRCNS PROGRAM, AS I MENTIONED, THE OTHER WORK HAS ALL BEEN SUPPORTED THROUGH FUNDING FOR NIAMS, FOR THE WORK ON THE MERKEL, CELLS. AND I THANK YOU FOR YOUR ATTENTION. [ APPLAUSE ] >> DOES ANYONE HAVE ANY QUESTIONS, PLEASE USE THE MICROPHONE. >> IF EVERY MERKEL CELL INNERIVATED AND HOW PLASTIC IS THIS, THIS IS A VERY PLASTIC ORGAN AND REMODELING OF THE RELATIONSHIP BETWEEN MERKEL AND THE NERVE CELLS. >> I WILL TUMOR SPECTRUM THAT I DID NOT PLANT THAT QUESTION BUT I DO HAVE AN ANSWER. >> SO AS HE JUST POINTED OUT, THE SKIN IS AN INTERESTING TARGET ORGAN FOR THE NERVOUS SYSTEM BECAUSE IT REMODELS, TURNS OVER EVERY 28 DAYS AND AS EPIDERMAL CELLS IN THE SKIN, WE WOULD EXPECT THAT THAT REMODELING MIGHT AFFECT NEURONAL STRUCTURE AND OF COURSE WE THINK THAT THAT COULD AFFECT THE RELIABILITY OF SENSORY SIGNALING SO 1 THING WE STARTED TO DO IS TO ANALYZE THE STRUCTURAL FEATURES OF THE AFFERENT, DURING PHYSIOLOGICAL STATES THAT WILL CAUSE REMODELING OF THE SKIN AND 1 OF THOSE IS HAIR GROWTH. SO THROUGHOUT YOUR LIFE, YOUR HAIR GROWS THROUGH A PROCESS OF ORGANO GENESIS, WHICH IS CALLED ANTIGEN, AND THEN SO THE HAIR GROWS, THE FOLLICLE INCREASES IN LENGTH BY MORE THAN 4 FOLD. IT CHANGES THE VASCULARIZATION OF THE FOLLICLE CHANGES AND THERE HAVE BEEN A FEW STUDIES THAT SHOWED THAT INNERVATION CHANGES DURING ACTIVE HAIR GROWTH. NOW FOR HUMANS, HOUR HAIR GROWTH IN A MOSAIC PATTERN SO THIS IS HAPPENING ALL THE TIME ACROSS YOUR BODY AND ON YOUR HEAD, BUT IN MICE THAT HAIR GROWTH IS QUITE SYNCHRONIZED SO THERE'S A WAVE OF HAIR GROWTH THAT PROP GATES DOWN THE BODY AND 1 THING THAT IS QUITE INTERESTING IS WHEN HAIR GROWS, THE SKIN INCREASES THICKNESS BY MORE THAN A FACTOR OF 2. SO YOU CAN IMAGINE THAT A CHANGE IN THICKNESS WILL CHANGE THE SKIN MECHANICS AND YOU KNOW THAT FROM MECHAN O SENSORY ORGAN, OR MECHAN O SENSORY CELL, 1 OF THE IMPORTANT FEATURES, THAT DETERMINES WHETHER THE CELL IS WELL STIMULATED IS HOW THAT CELL IS HOOKED UP TO ITS ACCESSORY ORGANS SO THIS IS 1 OF THE THINGS THAT MAKES A FEST INCREASE IN BODYULAR HAIR CELL DIFFERENT THAN AN AUDITORY HAIR CELL IS THAT IT'S HOOKED UP TO DIFFERENT ACCESSORY STRUCTURES THAT PERFORM A PHYSICAL TRANSMISSION OF THE FORCE. THE SKIN, THE SKIN IS THAT ACCESSORY STRUCTURE SO IF THE SKIN IS THICK AND COMPLIANT, THEN THE SAME DISPLACEMENT WILL LEAD TO LESS FIRING BECAUSE THE SKIN IS COMPLIANT, SO IF THE SKIN IS THIN AND STIFF, A SMALL DISPLACEMENT WILL LEAD TO A LOT OF FIRINGS IN THE NEURON SO WHAT WE FOUND, IS IN RESTING SKIN, SO ALL THE DATA I SHOWED YOU IS RESTING SKIN, AT WHICH A THIN--IT HAS A THIN FAT LAYER AND THE SKIN IS RELATIVELY STIFF. AND WE SAW--WE SEE THE DISTRIBUTION OF MERKEL CELL COMPLEXES I JUST SHOWED YOU AND HERA THE NUMBER IN RESTING SKIN. WHEN WE LOOKED IN ACTIVE HAIR GROWTH WHICH DIFFERS BY ONLY A COUPLE OF WEEKS IN THE MOUSE MOUSE'S LIFE, WE SEE THE NUMBER OF COMPLEXES INCREASES BY MORE THAN 50% BUT THE% OF CELLS CONTACTED STAYS THE SAME. SO WE SAN FRANCISCO THAT NUMBER OF MERKEL CELLS INCREASES AND WE INFER THAT THE NEURON IS SPROUTING TO INNERIVATE THOSE NEW CELLS. AND SO, WHAT WE'RE TRYING TO DO NOW, IS TO ASK WHETHER THESE DIFFERENCES IN STRUCTURE FOR THESE AFFERENTS LEADS TO AN INCREASE IN INTRINSIC NEURONAL ACTIVITY THAT IS CAPABLE OF CHANGE TAG SKIN ASK MECHANICS AND THAT IS THE FOCUS OF MY RO-1 THAT IS DUE TODAY. [LAUGHTER] EMPLOY. >> I JUST WANT TO UNDERSTAND THE LOGIC OF THE KNOCK OUT EXPERIMENTS. IT SEEMS TO ME, THE ALTERNATIVE EXPLANATION, BUT I MAY HAVE MISSED SOMETHING AND THAT IS RATHER THAN MIRACLE CELLS BEING NECESSARY FOR THE TRANSDUCTION, BEING NECESSARY TO GIVE THE CHARACTERISTICS OF EFFORTS AND YOU IDENTIFY THEM, EVEN IF THEY WERE THERE. SO THAT'S CORRECT, SO I WAS WAS--HOPE THAT I WAS CAREFUL TO SAY THAT WE HAVE NOTE SHOWN THAT THEY ARE NECESSARY FOR TOUCH SENSITIVITY IN THAT AFFERENT. WE'VE SHOWN THEY ARE NECESSARY FOR TOUCH EVOKED SAC1 FIRING SO IT COULD BE THAT-- >> TALK TO ABOUT THE FIRING OF THE CHARACTERISTIC OF SO1. >> SAC1 FIRING THE TOUCH STONE AFFERENT MIGHT BE A TOUCH RECEPTOR BUT IT'S NOT AN SAC1 ACT RECEPTOR ANYMORE. SO THE SIMPLE HYPOTHESIS, SO THE SIMPLEST HYPOTHESIS IS THAT THE CELLS ARE ABSOLUTELY ESSENTIAL AND THAT THAT NEURON WOULD HAVE NO TOUCH EVOKED FIRING. WE'RE TESTING THAT NOW. >> I GUESS THE SECOND HYPOTHESIS WOULD BE--I THINK OUR CHANNEL REDOBSIN DATA PROVIDES SOME SUPPORT FOR THIS, THAT THE AFFERENT ITSELF IS TOUCH SENSITIVE AND THAT IT IS MEDIATING A RAPIDLY ADAPTING RESPONSE AND THEN, THE MERKEL CELLS AT TOUCH SENSORS AND PROLONG THAT TO A SLOWLY ADAPTING RESPONSE. IF THAT WERE THE CASE, WE WOULD HAVE EXPECTED TO SEE A SELECTIVE ENHANCEMENT IN THE NUMBER OF RAPIDLY RECEPTORS IN OUR GENOTYPE LINE SURVEY AND WE DID NOT SEE THAT. WE SAW AN ERVETION PANGS OF BOTH AFFERENTS AND RAPIDLY ADAPTING AFFERENT. SO WE THINK THAT OUR--OUR DATA FAVOR A MODEL WHERE SA-1 MERKEL CELLS ARE OBELYINGATTOR ILLEGALSY REQUIRED FOR TOUCH SENSITIVITY BUT WE HAVE NOT TEMON STRAIGHTED THAT DIRECTLY. >> YOU HAD A QUESTION? >> SO DO YOU LIKE THE SPECULATE FOR A CASE FOR THE PATIENT IF THERE IS AN INJURY FOR THE REST OF THIS RESPONSE OF TOUCH? >> SO THE QUESTION--COULD YOU REPEAT THE QUESTION? >> IF THERE IS AN INJURY, HOW WILL THE RESPONSE BE AFFECTED. SO, OTHER GROUPS HAVE DONE EXPERIMENTS WHERE THEY DO NERVE INJURY, NOT A SKIN INJURY BUT A NERVE INJURY WHICH CAUSES A DISCIPLINARY BACK AND WHAT YOU SEE IN THOSE CASES IS WHEN THE NERVE DIES BACK, MERKEL CELLS IN IN BODY SITE, DISAPPEAR AND THEN AS THE NERVE REINNERIVATES THE RECEPTOR FIELD, THEY COME BACK. SO IN THE CASE OF A NEUROPATHIC INJURY, AT LEAST A LARGE INJURY LIKE THAT, WE WOULD EXPECT TO SEE LOTS OF TOUCH AND SENSITIVITY BECAUSE OF THE AFFERENT. NOW 1 QUESTION THAT WE'VE BEEN THINKING ABOUT, WHEN WE STARTED TO SEE THESE ARBORS WITH THIS--WHAT WE WOULD CALL A DRIVER AFFECT, 1 LARGE CLUSTER OF MERKEL CELLS, COMPLEXES SEEM TO BE DOMINATING THE OVERALL SA-1 RESPONSE. WE ASK, YOU KNOW WHY WOULD YOU HAVE THOSE OTHER CLUSTERS, LIKE WHY NOT--THE WAY TO GET MOST SENSITIVE TOUCH RECEPTOR IS TO TAKE ALL YOUR TRANSDUCTION UNITS AND CLUSTER THEM IN A SINGLE HEMINODE. THAT'S WHAT HAPPENS IN INVERTEBRATE TOUCH RECEPTORS FOR EXAMPLE, SO 1 POSSIBILITY IS THAT AN EVOLUTIONARY ADVANTAGE TO HAVING MULTIPLE SPEC INITIATION ZONES AND MULTIPLE CLUSTERS AND MERKEL CELLS AND TO HAVE ROBUSTNESS AND INJURY, SO IF THERE IS INJURY IN THE SKIN, THAT YOU MIGHT LOSE SOME TOUCH SENSITIVITY BUT YOU WON'T LOSE COMPLETE TOUCH OR SENSITIVITY OF THE RECEPTIVE FIELD BECAUSE THE OTHER CLUSTERS CAN PRODUCE TACTILE RESPONSES EVEN IF THE DRIVER CLUSTER IS INJURED. >> AND LIKE SAY I HAD THIS FINGER INJURY AND IT'S NOD PLACEMENT SO 1 OF THE NOD IS ALMOST NORMAL BUT THEN [INDISCERNIBLE] I HEAR BLANK FILLING AND SOME FUNNY PAIN SENSATION, SO HOW DOES THE PAIN SENSATION FIGURE IN THE PICTURE, WE WOULD EXPECT THAT THE PAIN SENSATION IN THAT CASE WOULD BE PRODUCED BY ACTIVATION OF OTHER AFFERENTS THAT ARE NOT SA-1 AFFERENTS SO THAT WOULD BE NO SUSCEPTIVE AFFERENTS AND IN THAT CASE, MY HYPOTHESIS, WOULD BE, THAT THE MERKEL CELLS WOULD NOT PLAY A VERY BIG ROLE FOR THAT SORT OF ACUTE PAIN. NOW WHERE WE THINK IT MIGHT BE PLAYING A ROLE IS IN NEUROPATHIC INJURY, WHERE--WHERE--STIMULI THAT WOULD NORMALLY BE INOXUOUS, THEN FEEL EXTREME LOW PAINFUL AND THE MODEL AND THE FIELD, IF THAT'S DUE TO PLASTICITY AND SPINAL CORD CIRCUITRY ASK PROBABLY NOT DUE TO CHANGES OUT HERE IN THE PERIPHERY AND WE HAVEN'T TESTED THAT, WE EVAPORATE DONE ANYTHING WITH NERVE INJURY WITH OUR MODELS. >> [INDISCERNIBLE] >> SO WE HAVE NOT DONE THAT BUT PETER'S GROUP HAS DONE A BEAUTIFUL JOB OF THOSE KINDS OF EXPERIMENTS, LOOKING AT COMPLEXES IN WHISKER FOLLICLES AND WHAT PETER FOUND IS WITH A BROAD SPECTRUM,AN TAGANIST OF IONOTROPIC RECEPTORS THAT HE COULD COMPLETELY KNOCK OUT, THE SLOWLY ADAPTING PHASE AND THE SENSITIVITY OF THE DYNAMIC PHASE WAS REDUCED BUT THEY--BUT IT WAS THERE, SO HE WAS ABLE TO UNCOUPLE THE SLOWLY ADAPTING VERSES THE DYNAMIC PHASE IN THE CONVERSION WAY, THEN WE DONE WITH CHANNEL REDOBSIN. PETER'S GROUP HAS GONE ON TO LOOK AT A VARIETY OF RECEPTORS AND THE RESULT VS BEEN QUITE CONFUSING, I WOULD SAY, SO, BASED ON THOSE DATA, PETER'S MODEL NOW IS THAT, THAT GLUTEA MATE RECEPTORS ARE ACTUALLY HITTING TRANSDUCTION CHANNELS, AND NOT--THE ANTAGONIST AND AGONIST ARE NOT HITTING GLUTEA MATE RECEPTS, SELECTIVELY. >> SO, IT'S PROBLEMATIC AND I'LL TELL YOU WHY. AS WITH EVERYTHING, ASSOCIATE WIDE MERKEL CELLS, THERE'S ALWAYS A TWIST AND THE TWIST IS THAT WE SEE LARGE AMOUNTS OF THE PROTEIN IN MERKELCELLS BUT WE ALSO SEE IT IN THE AFFERENTS SO IT IS POSSIBLE THIS IS A RECIPROCAL EXCITAATORY SYNAPSE WHICH I DON'T KNOW WHAT TO MAKE OF THAT. SO ANYTHING THAT MANIPULATES, VIGLO2 IN A NONSPECIFIC CELL TYPE MANNER WON'T GET AT A DIRECT ROLE IN TOUCH. >> ARE THERE ANYMORE QUESTIONS? >> SO I'D LIKE TO THANK ELEN FOR A WONDERFUL LECTURE. [ APPLAUSE ]