<p>This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.</p> <p>The bovine RPCI-42 BAC library was screened to construct a sequence-ready ~4 Mb
single contig of 92 BAC clones on BTA 1q12. The contig covers the region between
the genes <italic>KRTAP8P1</italic> and <italic>CLIC6</italic>. This genomic segment in cattle is of special interest
as it contains the dominant gene responsible for the hornless or polled phenotype in
cattle. The construction of the BAC contig was initiated by screening the bovine BAC
library with heterologous cDNA probes derived from 12 human genes of the syntenic
region on HSA 21q22. Contig building was facilitated by BAC end sequencing and
chromosome walking. During the construction of the contig, 165 BAC end sequences
and 109 single-copy STS markers were generated. For comparative mapping of 25
HSA 21q22 genes, genomic PCR primers were designed from bovine EST sequences
and the gene-associated STSs mapped on the contig. Furthermore, bovine BAC
end sequence comparisons against the human genome sequence revealed significant
matches to HSA 21q22 and allowed the <italic>in silico</italic> mapping of two new genes in cattle.
In total, 31 orthologues of human genes located on HSA 21q22 were directly mapped
within the bovine BAC contig, of which 16 genes have been cloned and mapped for the
first time in cattle. In contrast to the existing comparative bovine–human RH maps of
this region, these results provide a better alignment and reveal a completely conserved
gene order in this 4 Mb segment between cattle, human and mouse. The mapping of
known polled linked BTA 1q12 microsatellite markers allowed the integration of the
physical contig map with existing linkage maps of this region and also determined
the exact order of these markers for the first time. Our physical map and transcript
map may be useful for positional cloning of the putative polled gene in cattle. The
nucleotide sequence data reported in this paper have been submitted to EMBL and
have been assigned Accession Numbers AJ698510–AJ698674.</p>
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Comp Funct Genomics. 2005 Jun; 6(4):194-203