Sry-negative XX sex reversal in purebred dogs

The gene responsible for testis induction in normal male mammals is the Y-l inked Sry. However, there is increasing evidence that other genes may have testis-determining properties. In XX sex reversal (XXSR), testis tissue dev elops in the absence of the Y chromosome. Previous polymerase chain reactio n (PCR) assays indicated that autosomal recessive XXSR in the American cock er spaniel is Sry-negative. In this study, genomic DNA from the breeding co lony of American cocker spaniels and from privately owned purebred dogs wer e tested by PCR using canine primers for the Sry HMG box and by Southern bl ots probed with the complete canine Sry coding sequence. Sry was not detect ed by either method in genomic DNA of affected American cocker spaniels or in the majority (20/21) of affected privately owned purebred dogs. These re sults confirm that the autosomal recessive form of XXSR in the American coc ker spaniel is Sry-negative. In combination with previous studies, this ind icates that Sly-negative XXSR occurs in at least 15 dog breeds. The canine disorder may be genetically heterogeneous, potentially with a different mut ation in each breed, and may provide several models for human Sry-negative XXSR. A comparative approach to sex determination should be informative in defining the genetic and cellular mechanisms that are common to all mammals . Mel. Reprod. Dev. 53:266-273, 1999. (C) 1999 Wiley-Liss, Inc.