**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** BRAHMAN IS A VERY POPULAR CATTLE BREED IN THE SOUTHERN US. HOWEVER, THE BEEF PRODUCED BY BRAHMAN CATTLE IS GENERALLY TOUGH BECAUSE OF THE LOW MARBLING LEVEL. UP TO NOW, THE UNDERLYING MECHANISM IS STILL UNCLEAR. WE RECENTLY FOUND THAT A GROUP OF CELLS NAMED FIBRO/ADIPOGENIC PROGENITORS (FAPS) IN CATTLE SKELETAL MUSCLE CAN BECOME BOTH ADIPOCYTES (MARBLING FAT) AND CELLS THAT PRODUCE CONNECTIVE TISSUE. WE HYPOTHESIZE THAT THE DIFFERENCE IN QUALITY BETWEEN BEEF PRODUCED BY WAGYU CATTLE, A BREED PRODUCING HIGHLY MARBLED BEEF, AND BRAHMAN BEEF IS DUE TO THEIR DIFFERENCES IN FAPS. IN AIM #1, GENE EXPRESSION OF FAPS IN THE TWO CATTLE BREEDS AT DIFFERENT GROWTH AND DEVELOPMENTAL STAGES WILL BE STUDIED AT SINGLE-CELL LEVEL. IN AIM #2, THE EPIGENETIC MECHANISMS RESPONSIBLE FOR THE DIFFERENTIAL GENE EXPRESSION BETWEEN FAPS OF THE TWO BREEDS WILL BE EXPLORED THROUGH GENOME-WIDE DNA METHYLATION AND CHROMATIN ACCESSIBILITY ANALYSES. IN AIM #3, WAGYU X BRAHMAN CROSSBREEDING EXPERIMENT WILL BE CONDUCTED TO EVALUATE THE BEEF QUALITY OF CROSSBRED CATTLE. WE EXPECT TO REVEAL THE MECHANISM THROUGH WHICH FAPS REGULATE BEEF QUALITY. THE PROPOSED STUDY WILL SUGGEST THE USE OF FAP GENE EXPRESSION AND EPIGENETIC SIGNATURES IN MARKER-ASSISTED ANIMAL SELECTION AND DEMONSTRATE A NEW BEEF QUALITY IMPROVEMENT STRATEGY.