Fertile male tortoiseshell cat with true chimerism 38,XY/38,XY

The tortoiseshell coat colour is characteristic to female cats, and its occurrence in tomcats is very rare and associated with chromosome abnormalities (additional copy of X chromosome). The aim of this study was identification of the genetic basis of a case of tortoiseshell colour in a fertile Maine coon tomcat. Cytogenetic and molecular genetic studies were carried out with painting molecular probes (WCPP) specific to the X and Y sex chromosomes as well as a DNA microsatellite panel for the parentage verification of cats. Cytogenetic analysis revealed only a single set of sex chromosomes typical for male - 38,XY. The results of the microsatellite polymorphism obtained from DNA showed three alleles in locus FCA201 and four alleles in loci FCA149 and FCA441 in different tissues (blood, hair roots and testicles). Based on these results, the case was diagnosed as a true chimerism 38,XY/38,XY. To the best of our knowledge, this is the first case of a 38,XY/38,XY chimera diagnosed in cats, confirmed by genetic analysis.