Transcriptomic Analysis of Testicular Gene Expression in Normal and Cryptorchid Horses

SIMPLE SUMMARY: Cryptorchidism is a common congenital malformation that results in impaired fertility in horses. The high abdominal temperature and the effects of this disease lead to differences in gene expression between retained testes and descended testes (DTs). Here, we focus on the genetic effects of cryptorchidism. All the differentially expressed genes (DEGs) between undescended testes (UDTs) and DTs were analyzed in this study. A total of 84 DEGs were associated with functions related to sperm development and male reproductive performance. Our study has provided fundamental transcriptomic data for future studies on equine testes and cryptorchidism. ABSTRACT: Testes produce sperm, and investigations into gene expression in the testes will enhance the understanding of the roles of testicular genes in male reproduction. Cryptorchidism, the failure of one or both testes to descend into the scrotal sac, is a common congenital malformation in horses. The major clinical consequence of this abnormality is impaired fertility. The aim of this study was to analyze the expression patterns of testicular genes and to identify the differentially expressed genes (DEGs) in testes between cryptorchid and normal horses. In this study, the gene expression patterns in equine testes and the DEGs between mature descended testes (DTs) and undescended testes (UDTs) were identified by RNA-seq and validated by real-time qPCR. Our results provide comprehensive transcriptomic data on equine testes. The transcriptomic analysis revealed 11 affected genes that were downregulated in UDTs, possibly as a result of the higher temperature in the abdomen than in the scrotal sac. These 11 genes have previously been associated with male reproduction, and their downregulation might explain the impaired fertility of cryptorchid horses. Two homozygous missense mutations detected in horses with cryptorchidism were absent in normal horses and were listed as potential pathogenic mutations; these mutations should be verified in the future.