**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** AS A CONSEQUENCE OF INTENSIVE SELECTION, GENETIC DIVERSITY HAS BEEN SEVERELY REDUCED IN MALE SPECIFIC Y-CHROMOSOME LINKED GENES, CAUSING POTENTIAL DELETERIOUS EFFECTS ON MALE REPRODUCTION IN BOTH BEEF AND DAIRY CATTLE. AS FERTILITY AND SUBFERTILITY CONTINUE TO BE A COMMON PROBLEM IN CATTLE, AS WELL AS OTHER LIVESTOCK SPECIES, THE NEED FOR KNOWLEDGE ABOUT MOLECULAR MECHANISMS INFLUENCING FERTILITY REMAINS HIGHLY IMPORTANT. THIS PROJECTAIMS TO STUDY A NEWLY DISCOVERED, BOVID Y-CHROMOSOME GENE FAMILY, NAMED PREFERENTIALLY EXPRESSED ANTIGEN IN MELANOMA, Y-LINKED (PRAMEY).OUR RECENT FINDINGS ON PRAMEY'S EFFECT ON EARLY EMBRYO CLEAVAGE LEADS US TO BELIEVE THAT PRAMEY MAY PLAY AN IMPORTANT ROLE IN THE EPIGENETIC ALTERATIONS THAT OCCUR IN DEVELOPING EMBRYOS THROUGH METHYLATION REMODELING.TO DETERMINE PRAMEY'S INVOLVEMENT IN EARLY EMBRYONIC DEVELOPMENT WE WILL UTILIZE WELL ESTABLISHED BOVINE IN VITRO FERTILIZATION TECHNIQUES. EMBRYOS OF VARIOUS PRE-IMPLANTATION STAGES WILL BE PRODUCED USING SPERMATOZOA THAT HAVE BEEN TREATED TO INHIBIT THE PRAMEY PROTEIN DURING THE FERTILIZATION PROCESS. THE EMBRYOS WILL BE ANALYZED FOR CHANGES IN EPIGENETIC MARKS INCLUDING DNA AND HISTONE METHYLATION, AS WELL AS FOREXPRESSION LEVEL OF THE CDKN1A GENE, WHICH IS KNOWN TO BE PRESENT INEACH STAGE OF PREIMPLANTATION EMBRYO DEVELOPMENT ANDINVOLVED IN CELL CYCLE ARREST AND EMBRYONIC STEM CELL (ESC) DIFFERENTIATION. COLLECTED DATA WILL BE USED TO INFER IF THEPRAMEY PROTEIN PLAYS A ROLE IN EPIGENOMIC REPROGRAMMING DURING EARLY EMBRYONIC DEVELOPMENT. THE WORK PROPOSED IN THIS PROJECT WILL LEAD TO A BETTER UNDERSTANDING OF PRAMEY'S ROLE IN EARLY EMBRYONIC DEVELOPMENT AND CAN BE COMPILED WITH THE CURRENT KNOWLEDGE OF PRAMEY IN REPRODUCTION TO CREATE A RELIABLE WAY FOR PRODUCERS TO PREDICT BULL FERTILITY.IMPROVED PREDICTIONS OF BULL FERTILITYHAVETHE POTENTIAL TO INCREASE THE CONFIDENCE OF BREEDERS TO USE YOUNG BULLS AND FACILITATE AN INCREASE IN MALE CATTLE ENTERING THE MARKET FOR CONSUMPTION, WHICH COULD RELIEVE PRESSURE FORTHE NEED OFEDIBLE PROTEIN AS OUR WORLD POPULATION CONTINUES TO GROW.ADDITIONALLY, THE KNOWLEDGE FROM THIS PROJECTWILL BE APPLICABLE TO GENOMIC SELECTION AND REPRODUCTIVE PERFORMANCE OF OTHER LIVESTOCK SPECIES, AS WELL AS FERTILITY IN HUMANS.