Congenital keratoconjunctivitis sicca and ichthyosiform dermatosis in Cavalier King Charles spaniel dogs. Part II: candidate gene study.

PURPOSE: To identify causative mutation(s) for congenital keratoconjunctivitis sicca and ichthyosiform dermatosis (CKCSID) in Cavalier King Charles spaniel (CKCS) dogs using a candidate gene approach.

METHODS

DNA samples from 21 cases/parents were collected. Canine candidate genes (CCGs) for similar inherited human diseases were chosen. Twenty-eight candidate genes were identified by searching the Pubmed OMIM database (http://www.ncbi.nlm.nih.gov/omim). Canine orthologues of human candidate genes were identified using the Ensembl orthologue prediction facility (http://www.ensembl.org/index.html). Two microsatellites flanking each candidate gene were selected, and primers to amplify each microsatellite were designed using the Whitehead Institute primer design website (http://frodo.wi.mit.edu/primer3/). The microsatellites associated with all 28 CCGs were genotyped on a panel of 21 DNA samples from CKCS dogs (13 affected and eight carriers). Genotyping data was analyzed to identify markers homozygous in affected dogs and heterozygous in carriers (homozygosity mapping).

RESULTS

None of the microsatellites associated with 25 of the CCGs displayed an association with CKCSID in the 21 DNA samples tested. Three CCGs associated microsatellites were monomorphic across all samples tested.

CONCLUSIONS

Twenty-five CCGs were excluded as cause of CKCSID. Three CCGs could not be excluded from involvement in the inheritance of CKCSID.