Early functional divergence of adipose tissue depots in lambs: evidence from RNA-Seq and deconvolution analyses

Adipose tissue development in early life is crucial for thermoregulation, energy storage, and long-term metabolic programming. Understanding depot-specific differences provides insight into fat specialization and its adaptive significance. In fat- and semi-fat-tailed lambs, perirenal and tail fat are the main depots; however, their early postnatal development remains poorly understood. Here, we compared RNA-Seq data from perirenal and tail adipose tissues in 1-month-old Assaf lambs using differential gene expression and deconvolution analyses. A total of 2,507 genes were differentially expressed between the two fat depots. Perirenal fat exhibited transcriptional signatures associated with adipose tissue remodeling, thermogenic regulation, and the transition from brown to white adipose tissue, whereas tail fat showed increased expression of genes involved in lipid metabolism, insulin responsiveness, and mature adipocyte function. Despite the marked transcriptional divergence, deconvolution analyses did not identify significant differences in cell-type proportions between depots. Cell-type deconvolution using both a bovine single-nucleus RNA-seq reference atlas and an ovine embryonic single-cell RNA-seq atlas consistently identified adipocytes as the predominant cell populations, although they recovered distinct secondary cellular populations. The bovine reference atlas yielded higher Pearson’s correlation coefficients (0.728–0.803 vs. 0.254–0.602) and lower RMSE values (0.685–0.838 vs. 0.846–1.159) than the ovine embryonic reference, indicating a better fit to the bulk transcriptomic profiles despite being derived from a different species. These results suggest that, in 1-month-old lambs, the developmental stage represented by the reference atlas may have a greater impact on deconvolution performance than species origin. Overall, our findings provide new insights into adipose tissue specialization during early postnatal development and support the hypothesis that tail fat acquires mature lipid-storage characteristics earlier than perirenal fat in Assaf lambs.