Physical mapping of CHX10, ALDH6A1, and ABCD4 on bovine chromosome 10q34.

Bilateral anophthalmia/microphthalmia represents a rare and severe form of structural eye malformation in different species and has also been observed in cattle (Bähr et al., 2003). Therefore we started to map possible candidate genes for anophthalmia/microphthalmia in cattle. The ceh-10 homeo domain containing homolog (C. elegans) (CHX10) gene is an essential component in the network of genes required for the development of the mammalian eye, with profound effects on retinal progenitor cell proliferation and bipolar cell specification or differentiation. The recessive mouse mutation ocular retardation is characterized in the homozygous state by blindness with obvious non-syndromic microphthalmia and this phenotype is caused by a Chx10 mutation (Burmeister et al., 1996). A similar phenotype has been reported recently in two human families suffering from recessive mutations in CHX10 (Percin et al., 2000). A considerable number of comparable cases of human and murine anophthalmia/microphthalmia showed chromosomal deletions and translocations in affected individuals (Graw, 2003). For the chromosomal assignment of the bovine CHX10 gene we developed three locus-specific bovine BAC probes spanning the chromosomal region of CHX10. The human CHX10 gene maps at 73.77 Mb on HSA14q24 (NCBI map viewer, human genome build 35) and is flanked proximally by the aldehyde dehydrogenase 6 family, member A1 (ALDH6A1) gene at 73.59 Mb, and distal by the ATP-binding cassette, sub-family D (ALD), member 4 (ABCD4) gene at 73.82 Mb on HSA14. This report describes the identification and mapping of a BAC clone that can be used as the basis for cytogenetic studies of possible chromosomal deletions which may occur in bovine anopthalmia/micropthalmia using fluorescence in situ hybridization (FISH). We report here the assignment of the bovine CHX10 and the flanking ALDH6A1, and ABCD4 genes to BTA10q34 by FISH and radiation hybrid (RH) mapping.