Allelic incidence in several pig breeds of a missense variant of pig melanocortin-4 receptor (MC4R) gene associated with carcass and productive traits; its relation to IGF2 genotype.

MC4R, melanocortin-4 receptor, is involved in feed intake regulation. A mutation in a single base of MC4R, a G/A substitution in position 1426, has been linked to enhanced backfat thickness, average daily gain and daily feed intake. We present in this work a method to diagnose this mutation using real time PCR (RT-PCR) which allows rapid, cheap and reliable analysis of hundreds of samples in just 2h after DNA extraction. We have used this RT-PCR based assay to study the incidence of the mutation in several pig breeds or crosses (Iberian, Duroc, Pietrain, Large White, Large White×Pietrain) and wild boars. IGF2, insuline like growth factor 2, a gene with well demonstrated effects on carcass composition, of all these animals has also been analyzed and we show, using linkage disequilibrium analysis that both genes are independent. The implications of our results for pig selection toward fatty or lean carcasses are discussed.

Incidence in diverse pig populations of an IGF2 mutation with potential influence on meat quality and quantity: An assay based on real time PCR (RT-PCR).

IGF2, insulin-like growth factor 2, is implicated in myogenesis and lean meat content. A mutation in a single base (A for G substitution) of the gene for IGF2 (position 3072 in intron 3) has been recently described as the cause of a major QTL effect on muscle growth in pigs [Van Laere, A. S, Nguyen, M., Braunschweig, M., Nezer, C., Collete, C., & Moreau, L. et al. (2003). Nature, 425, 832-836]. We describe here a rapid assay based on real time PCR (RT-PCR) to detect this mutation. We have evaluated the incidence of the mutation in commercial pig crosses, in three populations of purebred Iberian or Iberian×Duroc crosses, and in cured meat products and wild boars. The incidence of the mutation varies among these groups. Penetrance of the A mutation is about 80% in the commercial population. Purebred Iberian pigs were all homozygous G/G whereas crosses of Iberian pigs were heterozygous (90%) or homozygous A/A (10%). The implications of this gene for the selection of Iberian pigs are discussed.

A real time PCR (RT-PCR) alternative assay to detect the T/C mutation in position 1843 of the ryanodine receptor gene.

The discovery of the causal mutation of malignant hyperthermia in pigs, a T for C substitution in base 1843 of the ryanodine receptor gene, opened the door to selection procedures based on the analysis of ryanodine receptor genotype based on PCR amplification of the region containing base 1843, subsequent digestion with specific restriction enzymes of the amplified DNA fragment, and electrophoretic analysis of the resulting bands. In this paper, we describe an assay that allows analysis of the three possible genotypes of the ryanodine receptor gene using real time PCR to amplify and detect them in a single step. Results obtained with the RT-PCR assay described in this work match 100% with those obtained using traditional PCR methods. RT-PCR methods are cheaper and faster than traditional ones allowing one to genotype up to 384 samples in a single run.