Linkage of bilateral convergent strabismus with exophthalmus (BCSE) to BTA5 and BTA18 in German Brown cattle.

Bilateral convergent strabismus with exophthalmus (BCSE) is a widespread inherited eye defect in several cattle populations. Its progressive condition often leads to blindness in affected cattle and decreases their usability. Furthermore, the German animal welfare laws prevent breeding with animals whose progeny are expected to be affected by genetic defects. Identifying genes involved in the heredity of BCSE should lead to insights into the molecular pathogenesis of this eye disease and permit the establishment of a genetic test for this disease. A whole-genome scan for 10 families containing a total of 159 genotyped individuals identified two BCSE loci. One BCSE locus mapped to the centromeric region on bovine chromosome (BTA) 5 and the other BCSE locus mapped to the telomeric region of BTA18. Thus, it is possible that two genes are involved in the development of BCSE. Alternatively, one of these loci could be the cause for the development of BCSE and the other locus could affect the progression and severity of the defect.