Single-cell multiomics reveals multiple adipogenic pathways and diverse multilineage specializations during embryonic fat tail morphogenesis.

Embryonic adipogenesis remains one of the least understood aspects of adipose biology in mammals due to time sensitivity, limited tissue volume, and ethical concerns. Here, we uniquely applied single-cell multi-omics sequencing to the developing adipose tissues of fat-tailed sheep, characterized by genetically determined, significant fat deposition in the tail during embryogenesis. Our dataset spans all stages of adipogenesis (E50 to E80), revealing three major cellular origins of fat deposition: progenitor and stem cells, connective tissue progenitors, and vascular smooth muscle cells. By integrating scRNA-seq, snATAC-seq, and functional validation, we identified key enhancer-driven gene regulatory networks (eGRNs) governing adipogenesis, with emerging as a critical regulator through its interaction with PPARG. Additionally, we delineated developmental trajectories and unique eGRNs underlying angiogenesis, osteogenesis, chondrogenesis, and myogenesis associated with fat formation. Our findings provide novel insights into embryonic adipogenesis in mammals and reveal critical regulons governing lineage specialization.