Functional genomics of fat metabolism and fat tail development in domestic sheep (Ovis aries)

Prolonged natural selection and human-mediated breeding has produced substantial phenotypic variation in ovine tail morphology and physiology, encompassing fat-tailed, fat-rumped and thin-tailed sheep. Currently, little is known about the specific biological processes contributing to prenatal fat tail development. The regulation of prenatal adipose tissue development is also one of the least understood aspects of adipose biology. Therefore, in this thesis, I initially used bulk RNA sequencing (RNA-seq) and histological assays to compare the microstructure and gene expression patterns for three foetal time points and an adult stage, and identified the key stages and pathways involved in ovine fat tail development. The stem cells residing in fat depots act as a progenitor pool to support adipocyte differentiation and adipose tissue development. Subsequently, I isolated primary adipose-derived stem cells (ADSCs) from prenatal fat tail tissues to examine their biological characteristics using cellular approaches and a comparative transcriptome approach across three different mammalian species. These ovine ADSCs exhibit excellent adipogenic ability and enhanced energy metabolic properties compared to human and mouse cells. They represent an excellent cell model for tissue engineering, basic fat metabolism research, and development of stem cell therapies. Furthermore, to illustrate tissue heterogeneity and the specific cell populations contributing to adipogenesis, I employed a single-cell sequencing strategy covering multiple stages of fat tail morphogenesis, which highlighted the multicellular origins of adipocytes and the complex gene regulatory networks (GRNs) governing lineage specialization. Overall, this thesis presents an in-depth exploration focusing on the developmental patterns, cellular foundations, and dynamic gene expression programs that drive ovine fat tail morphogenesis during foetal development.