Background: Mammals utilise an XX/XY system of sex determination in which the Y-linked gene SRY (Sexdetermining region Y) exerts a dominant masculinising influence on sexual development. Sex chromosome homology and comparative sequence studies suggest that SRY evolved from the related SOX3 gene on the X chromosome, although there is no direct functional evidence to support this hypothesis. The ...

Differentiation of the bipotential gonad into testis is initiated by the Y chromosome-linked gene SRY (Sex-determining Region Y) through upregulation of its autosomal direct target gene SOX9 (Sry-related HMG box-containing gene 9). Sequence and chromosome homology studies have shown that SRY most probably evolved from SOX3, which in humans is located at Xq27.1. Mutations causing SOX3 loss-of-fu...

In mammals, male sex determination is governed by SRY-dependent activation of Sox9, whereas female development involves R-spondin1 (RSPO1), an activator of the WNT/beta-catenin signaling pathway. Genetic analyses in mice have demonstrated Sry and Sox9 to be both required and sufficient to induce testicular development. These genes are therefore considered as master regulators of the male pathwa...

Evolutionary transitions between sex-determining mechanisms (SDMs) are an enigma. Among vertebrates, individual sex (male or female) is primarily determined by either genes (genotypic sex determination, GSD) or embryonic incubation temperature (temperature-dependent sex determination, TSD), and these mechanisms have undergone repeated evolutionary transitions. Despite this evolutionary lability...

The 46,XX testicular disorder of sex development (DSD), also known as 46,XX male syndrome, is a rare form of DSD and clinical phenotype shows complete sex reversal from female to male. The sex-determining region Y (SRY) gene can be identified in most 46,XX testicular DSD patients; however, approximately 20% of patients with 46,XX testicular DSD are SRY-negative. The SRY-box 9 (SOX9) gene has se...

Here, we describe a 3-month-old XX male French Bulldog. The diagnosis was based on the clinical signs, gonadal histology and cytogenetic analysis. Additionally, the dog was confirmed to be Sry negative by semi-quantitative reverse transcription polymerase chain reaction (sqRT-PCR). Canine Sry-negative XX sex reversal is a disorder of gonadal development where individuals who have a female karyo...

SOX9 is one of the genes that play critical roles in male sexual differentiation. Mutations of SOX9 leading to haploinsufficiency can cause campomelic dysplasia and XY sex reversal. We report here evidence supporting that SOX9 duplication can cause XX sex reversal. A newborn infant was referred for genetic evaluation because of abnormal male external genitalia. The infant had severe penile/scro...

In mammals, female development has traditionally been considered a default process in the absence of the testis-determining gene, Sry. Recently, it has been documented that the gene for R-spondin1 (RSPO1), a novel class of soluble activator for Wnt/beta-catenin signaling, is mutated in two Italian families with female-to-male (XX) sex reversal. To elucidate the role of Rspo1 as a candidate fema...

XX male is a kind of sexual differentiation disorder that affects one out of every 20,000 to 25,000 male births. The patients have male phenotypes with female chromosomes, the karyotype 46XX. More than 150 XX males have been reported in the medical literature since Albert de la Chapelle first reported a male human with a pure XX sex chromosome constitution in 1964.1,2 Most patients with this co...

Medaka, Oryzias latipes, has a firm XX-XY sex-determining system with the sex-determining gene, DMY, on the Y chromosome. However, previous studies have suggested that high water temperature might affect sex determination in Medaka. In the present study, the influence of high water temperature on sex reversal was examined. Fertilized eggs of two inbred strains of Medaka were developed at high w...