Mapping of the CYP1A1, SSTR1 and TTF1 genes to pig chromosome 7q refines the porcine-human comparative map

The cytochrome P-450, subfamily I, polypeptide 1 (CYP1A1), somatostatin rec eptor 1 (SSTR1) and transcription termination factor 1 (TTF1) genes, predic ted to reside on SSC7q based on chromosome painting studies, were selected for genetic mapping in the pig. Porcine sequence tagged sites (STSs) spanni ng 0.9-1.5 kb genomic DNA sequences were generated and all genes were physi cally assigned to SSC7q12-q23, q26 using a pig-rodent somatic cell hybrid p anel. Direct sequencing of PCR products from four different breeds revealed single nucleotide polymorphisms (SNPs) in all genes. SNPs in the SSTR1 and CYP1A1 genes allowed simple genotyping using PCR-restriction fragment leng th polymorphism (RFLP) analysis and linkage mapping with the PiGMaP referen ce families. SSTR1 was found to be closely linked to CYP1A1 (0.0 cM; LOD =1 1.1) and ANPEP (0.0 cM; LOD = 9.0). This refined the localization of a prev iously identified breakpoint in the linkage map between regions with orthol ogy to human chromosome 15q (represented by CYP1A1 and ANPEP) and 14q (repr esented by SSTR1). Moreover, multipoint linkage data suggest inverted segme nts of orthology between HSA14q11-q13 and SSC7q. The TTF1 SNP was confirmed by allele-specific PCR but was not informative in any of the families used for linkage analysis.