Analysis of testosterone pathway genes in dogs (78,XY;SRY‐positive) with ambiguous external genitalia revealed a homozygous animal for 2‐bp deletion causing premature stop codon in HSD17B3

Abstract

SummaryThe genetic background of disorders of sex development (DSD) in dogs with a normal male sex chromosome set (78,XY) is poorly described. In this study, we present for the first time, an analysis of six genes of the testosterone pathway, encoding enzymes (CYP17A1, HSD3B2, HSD17B3, SRD5A2) and transcription factors (NR5A1, AR). The entire coding sequence and flanking regions of the introns, 5′‐UTR and 3′‐UTR were analyzed in five DSD dogs (78,XY, SRY‐positive) with ambiguous external genitalia and in 15 control dogs. A homozygous deletion of 2 bp in exon 2 of HSD17B3 (hydroxysteroid 17‐beta dehydrogenase 3) was found in a Dachshund dog with enlarged clitoris, vulva and abdominal gonads and decreased serum testosterone level. In silico analysis revealed that this deleterious variant causes truncation of the encoded polypeptide (from 306 to 65 amino acids) and deprivation of the active site of the encoded enzyme. Genotyping of 23 control Dachshund dogs showed a normal homozygous genotype. Thus, we assumed that the 2‐bp deletion is the causative variant. Moreover, 24 SNPs (four in CYP17A1, three in HSD3B2, six in HSD17B3, five in SRD5A2, one in AR and five in NR5A1), two intronic indels (one in HSD3B2 and one in SRD5A2) and two microsatellite polymorphisms in exon 1 of AR were found. Six SNPs appeared to be novel. No association with DSD phenotype was observed. Identification of the first case of DSD in domestic animals caused by a deleterious variant of a gene involved in testosterone synthesis showed that these genes are important candidates in such studies.

Cytogenetic Analyses in Ewes with Congenital Abnormalities of the Genital Apparatus

“…From a phenotypic point of view, both cases previously reported are different from Case 3, but the lack of complete anatomic and histopathological analyses prevents the possibility of correctly classifying this DSD, hypothesizing the molecular causes and stating if this is another expression of the same genetic condition of previous cases. XY SRY -positive DSDs have been reported for different animal species [24,25,26,27], and only in dogs has a molecular cause been identified [28]. Even so, the DNA sample of this case is of great importance, since it could be used in a future genomic analysis aimed to study this condition in sheep.…”

Isolated cryptorchidism in dogs is not associated with polymorphisms of the INSL3 and AR candidate genes

“…Three SNPs were identified, but the distributions of their variants were similar in cryptorchid and control dogs (Nowacka‐Woszuk et al, 2020). The variability of CAG repeats in the AR gene was also analyzed in dogs with a complex DSD, but distribution of the variants was again similar in the affected and control dogs (Krzeminska et al, 2019a, 2019b; Nowacka‐Woszuk & Switonski, 2010).…”

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

“…The XY DSD dogs had ambiguous external genitalia (such as a rudimentary penis or enlarged clitoris with a bone); the phenotypes of the majority of them have been described elsewhere (Krzeminska et al . 2019; Nowacka‐Woszuk et al . 2020).…”

“…2009); (2) HSD17B3 , which causes underdevelopment of the male external genitalia (Krzeminska et al . 2019); and (3) NR5A1 , as seen in dogs with abnormal penile development associated with cryptorchidism (Nowacka‐Woszuk et al . 2020).…”