Tackling the characterization of canine chromosomal breakpoints with an integrated in-situ/in-silico approach: the canine PAR and PAB.

The domestic dog continues to represent an influential model organism for comparative biomedical research owing to the numerous genetic and pathophysiological similarities shared between human and dog diseases. The combined availability of a high-quality genome assembly and a 1 Mb-resolution genome-assembly integrated bacterial artificial chromosome (BAC) panel now provides the essential resources to combine cytogenetic and computational analyses to determine the precise locations of chromosome breakpoint regions within aberrant karyotypes. In this study we demonstrate the synergy of using a such a combined in-situ/in-silico approach to define chromosome breakpoints using the naturally occurring breakpoint present on all canine X chromosomes--the pseudoautosomal breakpoint (PAB). In so doing we have further characterized the canine pseudoautosomal region (PAR) to extend approximately 6.6 Mb from the telomeric end of CFA Xp and established that the canine PAB is contained within a 2 kb region. Our characterization of the canine PAR allowed for the comparative study of gene content across previously defined mammalian PARs and indicates that the canine PAB is contained with the gene Shroom2. The future application of the approach demonstrated in this study will prove useful when seeking to identify the genomic sequences surrounding recurrent chromosome breakpoints present in canine cancers.