Large scale across-breed genome-wide association study reveals a variant in HMGA2 associated with inguinal cryptorchidism risk in dogs

Identification of key genes related to unilateral cryptorchidism in sheep by comprehensive transcriptomics and proteomics analyses

BACKGROUND

Cryptorchidism is one of the most common reproductive abnormalities in rams, which seriously harms the reproductive capacity of rams and causes significant economic losses to the sheep industry. However, there are few studies elucidating its hereditary predisposition in sheep.

RESULTS

In the present study, the transcriptome and proteome of the cryptic (CT) and contralateral (CLT) testis from four unilaterally cryptorchid rams, and the normal testis (NT) from four healthy rams were analyzed using RNA-seq and TMT-based proteomics, respectively. A total of 10,357, 10,175, and 132 differentially expressed genes (DEGs) were identified between CT vs. CLT, CT vs. NT, and CLT vs. NT. Venn diagram showed that 9744 DEGs (5499 up-regulated and 4245 down-regulated) shared in CT vs. CLT and CT vs. NT. Functional enrichment analysis revealed that 5499 up-regulated DEGs were mainly involved in regulation of programmed cell death and metabolic process, while 4245 down-regulated DEGs were closely related to reproductive process, such as spermatogenesis, sexual reproduction, reproduction and male gamete generation. Furthermore, 325 overlapped genes (114 up-regulated and 211 down-regulated) between DEGs and DAPs that shared the same regulatory status were identified by combining transcriptomics and proteomics. Ten genes, including AKAP4, AKAP3, FSIP2, HSPA1L, HSPA4L, TUBB, TXNRD2, CDC42, PGK1 and HSPA1A, were identified as candidate key genes related to unilateral cryptorchidism.

CONCLUSION

Our results revealed that both gene and protein expression in the cryptic testis of unilateral cryptorchid rams is massively altered. Bioinformatics analysis unveiled several candidate genes and signaling pathways potentially involved in unilateral cryptorchidism. These findings provide new insights into the molecular mechanism underlying spermatogenesis failure caused by cryptorchidism.

Exploring Testicular Descent: Recent Findings and Future Prospects in Canine Cryptorchidism

BACKGROUND

Canine cryptorchidism, manifested by an abnormal testicular position, poses significant health risks and reproductive challenges in affected males. Despite a high prevalence, estimated at up to 10% in the canine population, a comprehensive understanding of its pathogenesis remains elusive. Studies in human cryptorchids and knockout mice have identified key factors involved in testicular descent, including INSL3, RXFP2, and AR. To date, only three DNA variants, found in the RXFP2, HMGA2, and KAT6A genes, have been associated with canine cryptorchidism.

SUMMARY

This review briefly summarizes current knowledge on testicular descent and the factors that regulate this process, based on cryptorchidism in humans and mice. It also highlights recent findings related to canine cryptorchidism, focusing on the INSL3, HMGA2, and KAT6A genes. The most significant results are discussed, with an emphasis on the role of the epididymis in testicular descent. This report presents insights that may facilitate further research aiming to broaden our understanding of canine cryptorchidism pathogenesis.

KEY MESSAGES

DNA polymorphism in the KAT6A gene, associated with changes in global H3K9 acetylation, as well as the DNA methylation pattern in the INSL3 gene, suggest that further research should strongly focus on epigenetic modifications. In addition, the development of the epididymo-testicular junction and the link between cryptorchidism prevalence and dog size should be further investigated.

Cryptorchidism and testicular cancer in the dog: unresolved questions and challenges in translating insights from human studies†

Cryptorchidism, the failure of one or both testes to descend into the scrotum, and testicular cancer show a strong correlation in both dogs and humans. Yet, long-standing medical debates persist about whether the location of undescended testes directly causes testicular cancer in humans or if both conditions stem from a common origin. Although testicular cancer is a prevalent disease in dogs, even less is known about its cause and correlation with testicular descent in this species. This review investigates the relation between these two disorders in dogs, drawing insights from human studies, and examines key biomarkers identified thus far. In addition, it explores potential causal links, including the impact of temperature on maturing testicular cells and a potential shared genetic origin. Notably, this literature review reveals significant differences between men and dogs in reproductive development, histological and molecular features of testicular tumors, and the prevalence of specific tumor types, such as Sertoli cell tumors in cryptorchid dogs and germ cell tumors in humans. These disparities caution against using dogs as models for human testicular cancer research and underscore the limitations when drawing comparisons between species. The paper concludes by suggesting specific research initiatives to enhance our understanding of the complex interplay between cryptorchidism and testicular cancer in dogs.

A massive alteration of gene expression in undescended testicles of dogs and the association of KAT6A variants with cryptorchidism

Cryptorchidism is the most common form of disorder of sex development in male dogs, but its hereditary predisposition is poorly elucidated. The gonadal transcriptome of nine unilaterally cryptorchid dogs and seven control dogs was analyzed using RNA-seq. Comparison between the scrotal and inguinal gonads of unilateral cryptorchid dogs revealed 8,028 differentially expressed genes (DEGs) (3,377 up-regulated and 4,651 down-regulated). A similar number of DEGs (7,619) was found by comparing the undescended testicles with the descended testicles of the control dogs. The methylation status of the selected DEGs was also analyzed, with three out of nine studied DEGs showing altered patterns. Bioinformatic analysis of the cDNA sequences revealed 20,366 SNP variants, six of which showed significant differences in allelic counts between cryptorchid and control dogs. Validation studies in larger cohorts of cryptorchid (n = 122) and control (n = 173) dogs showed that the TT genotype (rs850666472, p.Ala1230Val) and the AA genotype in 3'UTR (16:23716202G>A) in KATA6, responsible for acetylation of lysine 9 in histone H3, are associated with cryptorchidism (P = 0.0383). Both the transcript level of KAT6A and H3K9 acetylation were lower in undescended testes, and additionally, the acetylation depended on the genotypes in exon 17 and the 3'UTR. Our study showed that the massive alteration of the transcriptome in undescended testicles is not caused by germinal DNA variants in DEG regulatory sequences but is partly associated with an aberrant DNA methylation and H3K9 acetylation patterns. Moreover, variants of KAT6A can be considered markers associated with the risk of this disorder.