Comparative mapping of the POLG gene to cattle chromosome 21q17→q22 by FISH and confirmation by RH mapping

Abstract

The DNA directed polymerase gamma gene (POLG), known to be located on human chromosome (HSA) 15q25 (Walker et al., 1997), encodes the only DNA polymerase responsible for mitochondrial DNA (mtDNA) replication. Mutations in human POLG have been identified in affected families with progressive external ophthalmoplegia (PEO) characterized by accumulation of large-scale mitochondrial DNA deletions (OMIM #157640; Van Goethem et al., 2001). This gene was identified as candidate gene for congenital bilateral convergent strabismus with exophthalmus (BCSE) in cattle (OMIA 000353; Distl, 1993; Distl and Gerst, 2000). This monogenic autosomal dominant inherited phenotype in cattle shows similarities to the heterogeneous dominant and recessive forms of PEO in man, e.g. eye muscle biopsies of affected humans and cattle demonstrated the presence of ragged red fibers and many mtDNA deletions (Li et al., 1999). Application of a comparative approach, using a human cDNA to screen a bovine BAC library revealed a POLG-containing bovine BAC clone. To facilitate future linkage studies we report the physical mapping of the bovine POLG gene to cattle chromosome (BTA) 21q17→q22 by FISH and RH mapping.