Publication Date:
2012-07-14
Description:
Background: MUC4 is a type of membrane anchored glycoprotein and serves as the major constituent ofmucus that covers epithelial surfaces of many tissues such as trachea, colon and cervix.MUC4 plays important roles in the lubrication and protection of the surface epithelium, cellproliferation and differentiation, immune response, cell adhesion and cancer development. Togain insights into the evolution of the porcine MUC4 gene, we surveyed the nucleotidevariability and linkage disequilibrium (LD) within this gene in Chinese indigenous breedsand Western commercial breeds. Results: A total of 53 SNPs covering the MUC4 gene were genotyped on 5 wild boars and 307domestic pigs representing 11 Chinese breeds and 3 Western breeds. The nucleotidevariability, haplotype phylogeny and LD extent of MUC4 were analyzed in these breeds.Both Chinese and Western breeds had considerable nucleotide diversity at the MUC4 locus.Western pig breeds like Duroc and Large White have comparable nucleotide diversity asmany of Chinese breeds, thus artificial selection for lean pork production have not reducedthe genetic variability of MUC4 in Western commercial breeds. Haplotype phylogenyanalyses indicated that MUC4 had evolved divergently in Chinese and Western pigs. Thedendrogram of genetic differentiation between breeds generally reflected demographichistory and geographical distribution of these breeds. LD patterns were unexpectedly similarbetween Chinese and Western breeds, in which LD usually extended less than 20 kb. This isdifferent from the presumed high LD extent (more than 100 kb) in Western commercialbreeds. The significant positive Tajima'D, and Fu and Li's D statistics in a few Chinese andWestern breeds implied that MUC4 might undergo balancing selection in domestic breeds.Nevertheless, we cautioned that the significant statistics could be upward biased by SNPascertainment process. Conclusions: Chinese and Western breeds have similar nucleotide diversity but evolve divergently in theMUC4 region. Western breeds exhibited unusual low LD extent at the MUC4 locus,reflecting the complexity of nucleotide variability of pig genome. The finding suggests thathigh density (e.g. 1SNP/10 kb) markers are required to capture the underlying causal variantsat such regions.
Electronic ISSN:
1471-2156
Topics:
Biology
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