The first case of 38,XX (SRY-positive) disorder of sex development in a cat (Molecular Cytogenetics)

Background: SRY-positive XX testicular disorder of sex development (DSD) caused by X;Y translocations was not yet reported in domestic animals. In humans it is rarely diagnosed and a majority of clinical features resemble those which are typical for Klinefelter syndrome (KS). Here we describe the first case of SRY-positive XX DSD in a tortoiseshell cat with a rudimentary penis and a lack of scrotum. Results: Molecular analysis showed the presence of two Y-linked genes (SRY and ZFY) and a normal sequence of the SRY gene. Application of classical cytogenetic techniques revealed two X chromosomes (38,XX), but further FISH studies with the use of the whole X chromosome painting probe and BAC probes specific to the Yp chromosome facilitated identification of Xp;Yp translocation. The SRY gene was localised at a distal position of Xp. The karyotype of the studied case was described as: 38,XX.ish der(X)t(X;Y)(p22;p12)(SRY+). Moreover, the X inactivation status assessed by a sequential R-banding and FISH with the SRY-specific probe showed a random inactivation of the derivative XSRY chromosome. Conclusions: Our study showed that among DSD tortoiseshell cats, apart from XXY trisomy and XX/XY chimerism, also SRY-positive XX cases may occur. It is hypothesized that the extremely rare occurrence of this abnormality in domestic animals, when compared with humans, may be associated with a different organisation of the Yp arm in these species.