Cloning, Analysis And Mapping Of Callipyge Gene In Pigs

Genomic imprinting refers to parent-of-origin-dependent gene expression. The presence of imprinted gene can cause cells with a full parental complement of functional autosomal genes to specifically express one allele but not the other, resulting in monoalielic expression of imprinted loci. Genomic imprinting is a normal process and has been found in primary animals and plants for a long time. Imprinted genes play a critical role in fetal growth and behavioral development even though they account for less than 5% of all human genes.In 1983, a ram lamb exhibiting obvious muscular hypertrophy in the hindquarters was born into a commercial Dorset flock in Oklahoma. The ram produced offspring expressing the same phenotype, which is referred to as callipyge (Greek: calli- beautiful+ -pyge buttocks). Callipyge is a muscle hypertrophy phenotype in sheep. Dramatic effects on muscle development, carcass composition, shape, meat quality, feed efficiencies and feed intakes are hallmarks of the callipyge syndrome. The callipyge phenotype in sheep is an inherited muscular hypertrophy that affects only heterozygous individuals who receive the CLPG mutation from their father. The CLPG mutation is a A→G substitution 32.8 kb upstream of GTL2, which was later shown to be the only difference between the callipyge and wild-type chromosome in what is probably a long-range control element (LRCE).In this research we have selected 4 pigs which exhibiting obvious muscular hypertrophy in the hindquarters, and 4 pigs with normal phenotype. We extracted total RNA from their longissum tissue. Part of the CLPG cDNA have been obtained by RT-PCR, but we didn't find the A→G substitution as indentified in sheep. Then we have screened the BAC library built by our lab, and got two BAC clones. More than 1kb sequence around this CLPG1 was gotten by sequencing these two BAC clones. This CLPG1 gene was assigned to pig 7q12-7q23 by RH mapping.Understanding the mechanism by which the CLPG1 mutation alters these phenotypes would improve our basic knowledge of factors involved in muscle growth, carcass leanness, and meat quality, as well as delineate unique forms of genomic imprinting regulation.