Candidate gene analysis for bilateral convergent strabismus with exophthalmus in German Brown cattle

Congenital bilateral convergent strabismus with exophthalmus (BCSE) has been reported in many cattle populations. In German Brown cattle BCSE is supposed to be caused by a dominant single major gene. Affected animals show a bilateral symmetrical protrusion of the eyeball associated with an anterior-medial rotation of the eye. According to the high similarity of pathology and clinical features of BCSE with progressive external ophthalmoplegia (PEO) in man, three genes (POLG, SLC25A4, C10orf2), responsible for the human PEO, have been identified as potential candidate genes for BCSE in German Brown cattle. Using the bovine mapping results for these three genes we performed a linkage analysis with 27 microsatellite markers from BTA21, BTA26 and BTA27. Additional 8 geneassociated microsatellites were developed and these markers were included into the genome scan covering BTA21, 26 and 27 to clarify a potential role of these candidate genes for the bovine BCSE phenotype. Our results clearly showed that none of the microsatellite markers used was significantly linked to BCSE in German Brown cattle.