Transcriptomic Analysis of Testicular Gene Expression in Normal and Cryptorchid Horses

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.

Cryptorchidism in stallions

“…22 Cryptorchidism has been attributed to 4 primary mechanisms: failure of the gubernaculum to enlarge the inguinal ring, failure of regression of the gubernaculum, primary testicular abnormalities (cystic rete testis or neoplasia) and persistence of the suspensory ligament of the testis. 1,3,23,24 It has been shown that equine cryptorchid testes have a decreasein immunoreactive INSL-3 in the testicular interstitial cells. 25 Also, serum INSL3 was found to be lower in bilaterally cryptorchid stallions and unilaterally cryptorchid stallions following removal of the scrotal testis compared to intact and unilateral cryptorchid stallions with 1 scrotal testis.…”

The G-Protein-Coupled Membrane Estrogen Receptor Is Present in Horse Cryptorchid Testes and Mediates Downstream Pathways

“…In horses, cryptorchidism is a common congenital malformation associated with the failure to descend by one or both testes into the scrotal sac. The major clinical consequences resulting from elevated temperatures in the undescended testes are impaired fertility and a significantly increased risk of testicular malignancy [29]. It is a well-known fact that cryptorchid testis is incapable of producing spermatozoa, or, in some cases when the retained testis is located in the inguinal canal close to the scrotum, rare production of spermatozoa has been noted [30,31].…”

Transcriptional Specificity Analysis of Testis and Epididymis Tissues in Donkey

“…Three sets of transcriptome data, including donkey testis and epididymis tissues, as well as horse testis tissue, were downloaded and a total of 65.6 Gb of raw data was obtained. Accession numbers were listed as follows: donkey testis, donkey epididymis [PRJNA512590, PRJNA431818] [ 7 , 18 ], horse testis [PRJNA509608, PRJNA395221] ( Supplementary Table S1 ) [ 4 , 19 ].…”