Analysis of transcript and methylation levels of INSL3 and RXFP2 in undescended and descended dog testes suggested promising biomarkers associated with cryptorchidism

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.

New Insights into the Role of INSL-3 in the Development of Cryptorchidism

Cryptorchidism, defined as the failure of at least one or both testicles to descend into the scrotal pouches, is the most frequent (1.6-9% at birth, 1/20 males at birth) congenital anomaly encountered in newborn males, resulting in one of the most frequent causes of non-obstructive azoospermia in men. Similar to other congenital malformations, cryptorchidism is thought to be caused by endocrine and genetic factors, combined with maternal and environmental influences. The etiology of cryptorchidism is unknown, as it involves complex mechanisms aiming to control the testicular development and descent from their initial intra-abdominal location in scrotal pouches. The implication of insulin-like 3 (INSL-3) associated with its receptor (LGR8) is critical. Genetic analysis discloses functionally deleterious mutations in INSL3 and GREAT/LGR8 genes. In this literature review, we discuss and analyze the implication of INSL3 and the INSL3/LGR8 mutation in the occurrence of cryptorchidism in both human and animal models.

The RXFP2-PLC/PKC signaling pathway mediates INSL3-induced regulation of the proliferation, migration and apoptosis of mouse gubernacular cells

BACKGROUND

Testicular hypoplasia can affect the sexual and reproductive ability in adulthood, and even increase the risk of cancer. Abnormal development of the gubernaculum is one of the important factors of testicular hypoplasia. Therefore, a study of the structure and function of the gubernaculum is an important but neglected new breakthrough point for investigating the normal/abnormal development of the testis. Previous findings showed that Insulin like factor 3 (INSL3) is a key factor regulating the growth of gubernaculum, however, the mechanism by which INSL3 acts on the gubernaculum remains unknown. Therefore, we probed the mechanism associated with INSL3-induced the proliferation, migration, and apoptosis of gubernacular cells in mice.

METHODS

A culture cell model of neonatal mice gubernaculum is established by INSL3 intervention. We blocked PLC/PKC signaling pathway with U73122 pretreat to investigate the role of the PLC/PKC signaling pathway. The changes of cell proliferation, migration, and apoptosis were detected by molecular biological methods. In addition, the levels of PCNA and F-action were detected by immunofluorescence and western blotting.

RESULTS

We found that INSL3 can promote the proliferation and migration of gubernacular cells and inhibit their apoptosis, meanwhile, INSL3 significantly up-regulated PLC/PKC protein phosphorylation. However, treatment with the PLC/PKC signaling pathway inhibitor U73122 significantly inhibited these effects of INSL3. Besides, we found that INSL3 could up-regulate the protein expression level of PCNA and F-actin, while the PCNA and F-actin expression was significantly weakened after U73122 pretreatment.

CONCLUSIONS

This research revealed that INSL3 binding to RXFP2 may up-regulate the expression levels of PCNA and F-actin by activating the PLC/PKC signaling pathway to promote the proliferation and migration of gubernacular cells. It suggests that the RXFP2-PLC/PKC axis may serve as a novel molecular mechanism by which INSL3 regulates growth of the gubernaculum.

Revisiting the gonadotropic regulation of mammalian spermatogenesis: evolving lessons during the past decade

Spermatogenesis is a multi-step process of male germ cell (Gc) division and differentiation which occurs in the seminiferous tubules of the testes under the regulation of gonadotropins - Follicle Stimulating Hormone (FSH) and Luteinising hormone (LH). It is a highly coordinated event regulated by the surrounding somatic testicular cells such as the Sertoli cells (Sc), Leydig cells (Lc), and Peritubular myoid cells (PTc). FSH targets Sc and supports the expansion and differentiation of pre-meiotic Gc, whereas, LH operates via Lc to produce Testosterone (T), the testicular androgen. T acts on all somatic cells e.g.- Lc, PTc and Sc, and promotes the blood-testis barrier (BTB) formation, completion of Gc meiosis, and spermiation. Studies with hypophysectomised or chemically ablated animal models and hypogonadal (hpg) mice supplemented with gonadotropins to genetically manipulated mouse models have revealed the selective and synergistic role(s) of hormones in regulating male fertility. We here have briefly summarized the present concept of hormonal control of spermatogenesis in rodents and primates. We also have highlighted some of the key critical questions yet to be answered in the field of male reproductive health which might have potential implications for infertility and contraceptive research in the future.

Reproductive Management in Catteries: Optimising health and wellbeing through veterinarian-breeder collaboration

PRACTICAL RELEVANCE

Many veterinarians - even those engaged in small animal reproduction - are uncomfortable with taking care of cat breeders or being in charge of catteries. Likely reasons for this are that feline reproduction is largely under-represented in undergraduate and graduate reproduction teaching, as well as in postgraduate education and science, whereas cat breeders themselves are often well informed and actively share knowledge with other cat breeders via the internet and social media.

CLINICAL CHALLENGES

A variety of problems can exist within a cattery, and collaboration between veterinarian and breeder to solve these is ultimately beneficial for the breeder, for the veterinarian, and for the health and wellbeing of the individual cats and of the cattery as a whole.

AIM

This review presents a comprehensive overview of aspects of cattery management that might negatively impact reproduction, including sanitation, hygiene and infectious disease control. It also discusses monitoring of reproductive performance, breeding recommendations, and the diagnostic and therapeutic approach to some common and specific problems.

EQUIPMENT AND TECHNICAL SKILLS

Reproductive management in the cattery requires no specialised equipment, as such. What it does need is an open mind, in terms of seeing how things are done, an open ear, for listening to the breeder, and the veterinarian's clinical skills in palpation, auscultation and, where required, further examination of the animals. Keeping abreast of the latest information on infectious diseases, disinfection and genetics ensures proper advice is provided.

EVIDENCE BASE

Current knowledge of reproductive management in catteries is summarised in order to apply an evidence-based approach, whenever possible. Notwithstanding, much of the information remains empirical.

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

Cryptorchidism is the most common congenital sex development disorder in dogs. Despite this, little progress has been made in understanding its genetic background. Extensive genetic testing of dogs through consumer and veterinary channels using a high-density SNP genotyping microarray coupled with links to clinical records presents the opportunity for a large-scale genome-wide association study to elucidate the molecular risk factors associated with cryptorchidism in dogs. Using an inter-breed genome-wide association study approach, a significant statistical association on canine chromosome 10 was identified, with the top SNP pinpointing a variant of HMGA2 previously associated with adult weight variance. In further analysis we show that incidence of cryptorchidism is skewed towards smaller dogs in concordance with the identified variant’s previous association with adult weight. This study represents the first putative variant to be associated with cryptorchidism in dogs.

Whole genome sequencing identifies a missense polymorphism in PADI6 associated with testicular/ovotesticular XX disorder of sex development in dogs

Disorders of sex development (DSDs) are congenital malformations defined as discrepancies between sex chromosomes and phenotypical sex. Testicular or ovotesticular XX DSDs are frequently observed in female dogs, while monogenic XY DSDs are less frequent. Here, we applied whole genome sequencing (WGS) to search for causative mutations in XX DSD females in French Bulldogs (FB) and American Staffordshire Terries (AST) and in XY DSD Yorkshire Terries (YT). The WGS results were validated by Sanger sequencing and ddPCR. It was shown that a missense SNP of the PADI6 gene, is significantly associated with the XX DSD (SRY-negative) phenotype in AST (P = 0.0051) and FB (P = 0.0306). On the contrary, we did not find any associated variant with XY DSD in YTs. Our study suggests that the genetic background of the XX DSD may be more complex and breed-specific.

Anti-Müllerian hormone, testosterone, and insulin-like peptide 3 as biomarkers of Sertoli and Leydig cell function during deslorelin-induced testicular downregulation in the dog

The role of anti-Müllerian hormone (AMH) and insulin-like peptide 3 (INSL3) in male infertility is not fully understood. We used the downregulated testis as a model of gonadotropin-dependent infertility. Serum testosterone and AMH concentrations were studied in five adult male Beagles implanted (day 0) with 4.7 mg deslorelin (Suprelorin®, Virbac) (DES group). Testicular expression of LH receptor (LHR) and androgen receptor (AR), AMH, type 2 AMH receptor (AMHR2), INSL3 and its receptor (RXFP2) was evaluated 112 days (16 weeks) after deslorelin treatment by qPCR and immunohistochemistry, and compared to untreated adult (CON, n = 6) and prepubertal (PRE, n = 8) dogs. Serum testosterone concentration decreased significantly by the onset of aspermia on study day 14 (four dogs) or day 21 (one dog), and was baseline on day 105 (week 15). In contrast, serum AMH started to increase only after the onset of aspermia and reached the maximum detectable concentration of the assay by day 49-105 in individual dogs. Testicular LHR gene expression in DES was lower than in CON and PRE (P < 0.0001), while AR gene expression in DES was similar to CON and significantly higher than PRE (P < 0.0001). Testicular AMH expression in DES was intermediate compared to the lowest mRNA levels found in CON and the highest in PRE (P ≤ 0.006). AMHR2 gene expression was similar between groups. AMH protein was detected in Sertoli cells only, while AMHR2 immunoreactivity was principally detected in Leydig cells which appeared to be increased in DES. INSL3 and RXFP2 gene expression was significantly downregulated in the DES testis along with noticeably weak Leydig cell immunosignals compared to CON. In conclusion, deslorelin treatment caused testicular LH insensitivity without affecting androgen sensitivity, and de-differentiation of Sertoli and Leydig cells. In DES, upregulation of the AMH-AMHR2 feed-back loop and downregulation of the INSL3-RXFP2 feed-forward loop are paracrine-autocrine mechanisms that may additionally regulate testosterone production independent of gonadotropins. Our results support AMH and INSL3 as unique biomarkers and paracrine-autocrine regulators of testis function involved in the intimate interplay between Sertoli and Leydig cells.