Linkage mapping of the MC3R gene to porcine chromosome 17

Family of melanocortin receptor (MCR) genes in mammals-mutations, polymorphisms and phenotypic effects

The melanocortin receptor gene family consists of five single-exon members, which are located on autosomes. Three genes (MC2R, MC4R and MC5R) are syntenic in the human, mouse, cattle and dog genomes, while in the pig, the syntenic group comprises MC1R, MC2R and MC5R. Two genes (MC1R and MC4R) have been extensively studied due to their function in melanogenesis (MC1R) and energy control (MC4R). Conservative organisation of these genes in five mammalian species (human, mouse, cattle, pig and dog), in terms of the encoded amino acid sequence, is higher in the case of MC4R compared to MC1R. Polymorphisms of these two genes are responsible or associated with variation of pigmentation (MC1R) and adipose tissue deposition (MC4R). Polymorphic variants in MC1R, causing coat colour variation, were described in humans and domestic mammals (cattle, horse, pig, sheep, dog), as well as farm red and arctic foxes. The MC4R gene is very polymorphic in humans and it is well known that some variants cause monogenic obesity or significantly contribute to the development of polygenic obesity. Such relationships are not so evident in domestic mammals; however, at least one missense substitution (298Asp > Asn) in the porcine MC4R significantly contributes, at least in some breeds, to fat tissue accumulation, feed conversion ratio and daily weight gain. Knowledge on the phenotypic effects of polymorphisms of MC2R, MC3R and MC5R in domestic mammals is scarce, probably due to the small number of reports addressing these genes. Thus, further studies focused on these genes should be undertaken.

SNiPORK - a microarray of SNPs in candidate genes potentially associated with pork yield and quality - development and validation in commercial breeds

SNiPORK is an oligonucleotide microarray based on the arrayed primer extension (APEX) technique, allowing genotyping of single nucleotide polymorphisms (SNPs) in genes of interest for pork yield and quality traits. APEX consists of a sequencing reaction primed by an oligonucleotide anchored with its 5' end to a glass slide and terminating one nucleotide before the polymorphic site. Extension with one fluorescently labeled dideoxynucleotide complementary to the template reveals the polymorphism. Ninety SNPs were selected from those associated directly or potentially with pork traits. Of the 90 SNPs, 5 did not produce a positive signal. For 85 SNPs, 100% repeatiblity was proved by double genotyping of 13 randomly chosen boars. In addition, the accuracy of genotyping was verified in 2 sib-families by a Mendelian inheritance of 49-50 homozygous genotypes from sire to sons. Three genotype discrepancies were found (97% accuracy rate). All inaccurities were confirmed by an alternative method (sequencing and PCR-RFLP assays). Moreover, the exclusion power of the chip was evalueted by an SNP inheritance analysis of unrelated boars within each sib-family. In the validation step, 88 boars (13 Pietrain, 31 Landrace, 16 Large White, 8 Duroc, 7 Hampshire x Pietrain crosses, and 13 other hybrid lines) were screened to validate SNPs. Among the 85 selected SNPs, 12 were found to be monoallelic, the rest showing at least two genotypes for the entire population under study. The primary application of the SNiPORK chip is the simultaneous genotyping of dozens of SNPs to study gene interaction and consequently better understand the genetic background of pork yield and quality. The chip may prospectively be used for evolutionary studies, evaluation of genetic distances between wild and domestic pig breeds, traceability tests, as well as the starting point for developing a platform for identification and paternity analysis.

SNaPshot Minisequencing and a Panel of Candidate Genes for Complex Routine Testing of Meat Performance Traits in Pigs

The aim of the study was to introduce a convenient method for identification of differences among individual animals in genes supposed to influence meat performance in pigs. The set of seven candidate genes (IGF2, FOS, MC4R, DGAT1, MYF4, MYF, and MC3R) was used. To determine the genotypes, multiplex polymerase chain reaction (PCR) and minisequencing using SNaPshot system (Applied Biosystems; Forster City, CA, USA) were applied. The efficiency of this gene panel for routine testing in pigs was verified in the Black Pied Prestice pig breed by the statistical general linear model. The results showed that both the method and the gene panel are convenient for meat quality testing and offer reproducible results.