Assignment of the PAX6 gene to bovine chromosome 15q25→q27 by fluorescence in situ hybridization and confirmation by radiation hybrid mapping

Abstract

Paired box gene 6 (PAX6), as a member of the paired box gene family, encodes a homeodomain transcription factor involved in oculogenesis and other developmental processes (Gehring, 2002). PAX6 represents a universal master control gene for eye morphogenesis and in cattle PAX6 has been shown to be essential for eye development and for tissue-specific gene expression within the eye (Jaworski et al., 1997). Various known mutations in the PAX6 homologs of man and mouse cause different congenital ocular disorders. Mouse Pax6 heterozygous mutants have small eyes, whereas homozygous mutants have only remnants of ocular tissues (Graw, 2003). In humans PAX6 mutations mainly cause aniridia and less commonly cause isolated cataracts (OMIM 607108). The human PAX6 gene consists of 14 exons spanning about 21.3 kb and has been mapped on human chromosome (HSA) 11p13 (Glaser et al., 1992). A considerable number of the sporadic aniridia cases in man have large chromosomal deletions in 11p13 detectable by fluorescence in situ hybridization (FISH) analysis, and some are also visible with conventional cytogenetic banding (van Heyningen and Williamson, 2002). Because of the possible involvement of PAX6 in bovine congenital ocular diseases (OMIA 0049/0050; Nicolas, 2003) we have started to clone the PAX6 gene in cattle. This report describes the identification and mapping of a PAX6 BAC clone which provides a basis for cytogenetic studies of possible chromosomal deletions that may occur in bovine anopthalmia/ micropthalmia. We report here the assignment of the bovine PAX6 gene to BTA15q25→q27 by fluorescence in situ hybridization (FISH) and radiation hybrid (RH) mapping. This location is consistent with known conservation of synteny between cattle, human and mouse genomes (Hayes et al., 2003).