miRNA Sequencing and Differential Analysis of Testis in 1-Year-Old and 2-Year-Old Kazakh Horses.

The Kazakh horse represents a significant genetic resource within China's equine population, characterized by notable resilience and an ability to thrive on coarse forage. Nevertheless, a decline in its numbers has been observed recently, making the improvement of its reproductive performance crucial for the preservation of this breed and the advancement of the related industry. In this study, testicular tissues from 1-year-old (pre-pubertal) and 2-year-old (post-pubertal) Kazakh horses were analyzed. miRNA sequencing was conducted on tissues from these age groups, followed by bioinformatics analyses to elucidate the functions of differentially expressed miRNAs (DEmiRNAs). The reliability of the sequencing data was subsequently verified using RT-qPCR. Analysis revealed 165 differentially expressed miRNAs (DEmiRNAs) in the testicular tissues between the two age groups. Of these, 118 DEmiRNAs (e.g., eca-miR-206 and eca-miR-2483) were significantly up-regulated (p < 0.05), and 47 DEmiRNAs (e.g., eca-miR-196a and eca-miR-211) were significantly down-regulated (p < 0.05). These DEmiRNAs were mainly implicated in biological processes including lipid metabolism and signal transduction. Their predicted target genes are potentially involved in key reproductive processes, notably testicular development and spermatogenesis. This study identifies candidate miRNAs and potential regulatory pathways associated with sexual maturation in Kazakh horses, providing a preliminary molecular basis for future functional validation and improvement of equine reproductive performance.