WHILE THE DNA WITHIN ALL CELLS OF A SINGLE INDIVIDUAL IS VIRTUALLY IDENTICAL, THE ACTIVITY OF THAT DNA AMONG CELLS CLEARLY DIFFERS AS, FOR EXAMPLE, CELLS IN THE EYE HAVE A DISTINCT FUNCTION COMPARED TO CELLS IN THE LIVER. DIFFERENCES IN THE FUNCTION OF CELLS CAN BE ATTRIBUTED TO EPIGENETICS - VARIATION IN HOW THE GENOME IS REGULATED AND EXPRESSED. BEYOND SINGLE CELLS, MANY OF THE MOST IMPORTANT TRAITS OF A HORSE, SUCH AS ATHLETIC PERFORMANCE, GROWTH, AND FERTILITY, ARE COMPLEX, MEANING THEY ARE DETERMINED BY SMALL CONTRIBUTIONS OF MANY GENES AND INTERACTIONS AMONG MANY CELL POPULATIONS. ADDITIONALLY GENOME REGULATION DIFFERS BETWEEN THE SEXES, IS DEPENDENT UPON AN INDIVIDUAL'S STAGE OF LIFE, AND IS ALTERED BY THE ENVIRONMENT. THE UNDERSTANDING OF GENOME REGULATION AND THUS THE DETERMINATION OF COMPLEX TRAITS REMAINS ELUSIVE. THE INTERNATIONAL FUNCTIONAL ANNOTATION OF ANIMAL GENOMES (FAANG) INITIATIVE WAS FORMED TO ADDRESS THIS GAP IN KNOWLEDGE. THE EFFORTS OF THE FAANG INITIATIVEWILL HELP CONNECT THE GENOME TO OUTCOMES IN PERFORMANCE AND HEALTH OF ANIMALS, AND IN TURN, ACCELERATE THE DEVELOPMENT OF GENOMIC TOOLS FOR AGRICULTURAL SPECIES. THE EQUINE FAANG COMMUNITY REPRESENTS A UNIQUE RESEARCH COOPERATIVE THAT HAS COLLABORATED TO BOLSTER CONTRIBUTIONS TO THE INITIATIVE. EXPANDING UPON ONGOING EFFORTS, THIS PROJECT WILL CONTRIBUTE TO OUR LONG-TERM GOAL OF CREATING A TISSUE-SPECIFIC FUNCTIONAL ANNOTATION OF THE EQUINE GENOME TO CORRELATE WITH GENOME EXPRESSION (THE TRANSCRIPTOME) ACROSS SEXES, BREEDS, AND DEVELOPMENTAL STAGES. THE GOALS OF THIS PROJECT ARE TO DEFINE GENOME REGULATION AND FUNCTION IN TISSUES OF THE ADULT STALLION AND TO PROVIDE UNIQUE INFORMATION REGARDING THE INTERPLAY BETWEEN EPIGENETICS AND A CRITICAL CHROMOSOMAL FEATURE, THE CENTROMERE. WE WILL DEFINE THE TRANSCRIPTOME ACROSS-TISSUES COLLECTED FROM TWO, WELL-PHENOTYPED THOROUGHBRED STALLIONS (OBJECTIVE 1). WITHIN EACH TISSUE, THE TRANSCRIPTOME WILL BE CORRELATED WITH EPIGENETIC MARKS OF GENOME REGULATION (OBJECTIVE 2) AND THE UNIQUE EPIGENETIC DETERMINATION OF CENTROMERE FUNCTION, ITS POSITIONAL VARIATION, AND CORRELATION WITH THE TRANSCRIPTOME WILL BE EVALUATED (OBJECTIVE 3). THE RESULTING PUBLICALLY AVAILABLE ATLAS OF GENOME REGULATION WILL BECOME THE BASIS OF COMPARISON BETWEEN SEXES, ACROSS BREEDS AND SPECIES. THESE DATA WILL PROVIDE A MEANS BY WHICH TO DEFINE GENOME DYSREGULATION IN HERITABLE TRAITS, AND ACCELERATE BUILDING OF THE LINK BETWEEN THE GENOME AND ANIMAL HEALTH AND PERFORMANCE.