Single-Cell Transcriptomics Defines Sequential Cell Fate Transitions and Sertoli Cell Maturation During Yak Testis Development
Description
The delayed sexual maturity of yaks markedly limits their reproductive efficiency and genetic improvement. To comprehensively clarify the cellular and molecular mechanisms underlying yak testis development, this study combined histological analysis and single-cell RNA sequencing (scRNA-seq) to examine testicular tissues from 6-month-old (6M), 18-month-old (18M), 4-year-old (4Y) yaks, and adult cattle-yaks (TES). Histological analysis indicated that lumens within the seminiferous tubules emerged in yaks after 6 months, while complete spermatogenesis was achieved at approximately 30 months. Using scRNA-seq, 45,290 high-quality testicular cells were profiled, enabling the construction of single-cell transcriptional atlases of yak testis development and adult cattle-yak testes. This study centered on Sertoli cells (SCs) and identified four sequential developmental states, namely Progenitor, Immature-1, Immature-2, and Mature. Each state was defined by distinct marker genes, such as CDCA3, INHA, WFDC2, and AARD, which were further confirmed using RT-qPCR and immunofluorescence. Pseudotime and GeneSwitches analyses highlighted critical gene expression changes during SC maturation, showing that DEFB119 expression begins specifically in the late developmental stage. Functional assays indicated that DEFB119 overexpression markedly increased the expression of genes associated with cell differentiation and steroid synthesis in SCs, supporting its potential role as an important regulator for SC functional maturation. This study mapped the cellular dynamics of yak testis development and the progressive maturation of SCs at single-cell resolution, identifying stage-specific marker genes and potential regulatory factors. The findings offer an important data resource and theoretical framework for understanding the molecular mechanisms behind delayed sexual maturity in yaks, developing early fertility prediction markers, and reducing the generation interval through molecular breeding.