Chromosome abnormalities in dogs with disorders of sex development (DSD)

Pathological characteristics of SRY-negative 38,XX-DSD pigs: A family case report

Disorders of sex development (DSD) are congenital conditions characterized by atypical development of chromosomes, gonads, or anatomical sex. XX-DSD pigs disrupt the production of high-quality breeding pigs and impede the advancement of the pig industry. However, the etiology of XX-DSD pigs remains unclear. Systematic reports on the genetic and pathological characteristics of prepubescent XX-DSD pigs in familial contexts are sparse. This study aimed to investigate the genetic and pathological features of one-month-old XX-DSD pigs within a familial context and to provide phenotypic information to elucidate the pathogenic mechanisms of XX-DSD pigs. The findings revealed that inbreeding within the XX-DSD family may contribute to the pathogenesis of XX-DSD pigs. All XX-DSD pigs in the family had a chromosomal sex of female and were male pseudohermaphrodites. The degree of masculinization of the reproductive organs varied among XX-DSD pigs, demonstrating phenotypic heterogeneity. HE staining showed that the testes of prepubescent XX-DSD pigs contained vesicles in the seminiferous tubules, with or without vestigial germ cells. Ultrastructural analyses indicated that sertoli cells, leydig cells and germ cells in the testes of XX-DSD pigs exhibited pathological damage, confirming impaired testicular function. Immunofluorescence staining revealed high expression of SRY-box transcription factor 9 (SOX9) in XX-DSD pig testicular tissues, while forkhead box L2 (FOXL2) was minimally expressed. Disordered secretion of reproductive hormones in prepubescent XX-DSD pigs indicated abnormal hypothalamic-pituitary-gonadal axis (HPGA) function. This study elucidates the genetic and pathological characteristics of prepubescent XX-DSD pigs in familial case, providing valuable insights for further exploration of the pathogenic mechanisms underlying XX-DSD.

An Unusual Case of Collision Testicular Tumor in a Female DSD Dog

Collision tumors (CT) consist of two independent neoplasms with distinct neoplastic populations. Disorders of sexual development (DSDs) are characterized by atypical sexual development leading to various abnormalities of the genital tract. Sex reversal (SR) syndromes are a type of DSD characterized by a discrepancy between chromosomal sex and gonadal development (testes/ovaries) and the presence or the absence of the SRY gene. A phenotypically female 8-year-old Jack Russell terrier dog was referred due to anomalous vaginal discharge and non-pruritic cutaneous bilateral symmetrical alopecia on the flanks. During abdominal palpation, a voluminous mass was detected in the left quadrant area, later confirmed by ultrasound. The owner decided to proceed with euthanasia and necropsy. In the abdominal cavity, the left gonad was increased in size, the right one and the uterus were decreased, and the vagina and vulva appeared to be thickened. Histologically, both gonads were revealed to be testes: the left one was affected by a double neoplastic component (sustentacular tumor and interstitial cell tumor), whereas the right gonad showed coarctated seminiferous tubules. PCR amplification of the genes SRY and AMELX revealed the absence of the MSY region of the Y chromosome. To the authors’ knowledge, this is the first report describing a case of a testicular collision tumor in a DSD SRY-negative dog.

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.

Copy number variation of the SRY gene showed an association with disorders of sex development in Yorkshire Terrier dogs

The molecular background of disorders of sex development (DSD) in dogs is poorly understood. Several copies of the SRY genes have been reported in the dog genome. We used droplet digital PCR with the aim of determining variability in SRY copy number and its association with DSD in dogs. Altogether 19 DSD male dogs (XY DSD) of 10 breeds and 87 control dogs of eight breeds were analyzed. Moreover, we performed a comparative analysis of SRY copy number in other canids: wolves (3), red foxes (16), and Chinese raccoon dogs (10). We found that the modal number of SRY copies in dogs, wolves, red foxes, and Chinese raccoon dogs was 3, 3, 1, and 3 respectively. Variability of copy number was only observed in Yorkshire Terriers (two or three copies) and red foxes (one or two copies). An analysis of six DSD Yorkshire Terriers and 38 control males of this breed showed that 50% of the DSD dogs had two copies, while the incidence of this variant was significantly lower in the control dogs (10.5%). Searching for the copy number of the coding and 5'-flanking fragments revealed full concordance with the copy number. These fragments were also sequenced in DSD (19) and control (24) dogs, and no DNA variants were found. We conclude that, in the dog, two or three functional copies of the SRY gene are present, and a smaller number of copies showed an association with the risk of DSD phenotype in Yorkshire Terriers.

Identification of aneuploidy in dogs screened by a SNP microarray

Microarray analysis is an efficient approach for screening and identifying cytogenetic imbalances in humans. SNP arrays, in particular, are a powerful way to identify copy-number gains and losses representing aneuploidy and aneusomy, but moreover, allow for the direct assessment of individual genotypes in known disease loci. Using these approaches, trisomies, monosomies, and mosaicism of whole chromosomes have been identified in human microarray studies. For canines, this approach is not widely used in clinical laboratory diagnostic practice. In our laboratory, we have implemented the use of a proprietary SNP array that represents approximately 650,000 loci across the domestic dog genome. During the validation of this microarray prior to clinical use, we identified three cases of aneuploidy after screening 2053 dogs of various breeds including monosomy X, trisomy X, and an apparent mosaic trisomy of canine chromosome 38 (CFA38). This study represents the first use of microarrays for copy-number evaluation to identify cytogenetic anomalies in canines. As microarray analysis becomes more routine in canine genetic testing, more cases of chromosome aneuploidy are likely to be uncovered.