Genetic characterization of Calabrese and Casertana pig ancient autochthonous genetic types (AAGT) at CRC locus

Calcium Release Channel (CRC) is a “candidate DNA segment encoding protein (gene)” of high interest for pork quality. It maps on the short arm of chromosome 6 and has two allelic forms: N (normal dominant allele) and n [mutated recessive allele, also known as “halothane sensitivity” allele (Haln)]. Haln is due to a point mutation (SNP, single nucleotide polymorphism) which consists in the transition of a thymine nucleotide base for a cytosine at position 1843 in the 134 bp exon, responsible for the synthesis of a protein containing a substitution of an “arginine” for a “cysteine” at position 615; in the muscle fiber this substitution induces anomalies in the calcium flow regulation at sarcoplasmic reticulum level (ionic calcium deregulation). This deregulation in pig species is manifested as PSS (Porcine Stress Syndrome). Meat of PSS animals displays PSE (Pale Soft Exudative) myopathy, which makes meat less acceptable to consumer and poorly suitable to transformation in products of a good quality. The individuation of the point mutation allowed to set up a fast and efficient “genetic prophylaxis” test based on the genotype determination at CRC locus in order to detect heterozygous carriers of mutated allele and their incidence. In fact, the halothane test does not distinguish between the heterozygous (Nn) and homozygous normal (NN) animals, because both of these genotypes are non reactive. Furthermore, some nn subjects are halothane negative due to incomplete penetrance. In order to individuate the possible presence of mutated allele within Casertana (CT) and Calabrese (CA) AAGTs, a genetic screening was performed on 110 subjects of CT AAGT and 40 CA AAGT pigs, reared at ConSDABI experimental farm, using PCR-RFLP (Polymerase Chain Reaction - Restriction Fragment Lenght Polymorphisms) method. The results showed that all Casertana AAGT pigs were NN (100%) while in AAGT Calabrese the frequencies of NN and Nn genotypes were 75% and 25% respectively. No nn genotype was found in the tested animals. It is opportune to specify that familiar relationships exist between Calabrese subjects, due to the reduced consistency of pig population. These results, valid within the observation field, confirm what found in a previous research in which Casertana was different from Calabrese and Nero Siciliano AAGTs for genotypic frequencies values: NN: 100,0% vs 65,5% vs 93,9%, respectively