Identification of two alphaRYR alleles and characterization of alphaRYR transcript variants in turkey skeletal muscle

We hypothesized that a mutation in the turkey skeletal muscle ryanodine receptor alpha isoform (alphaRYR) underlies turkey meat quality problems which are strikingly similar to pale, soft, exudative (PSE) pork. RT-PCR analysis of turkey alphaRYR mRNA covering amino acids 376 to 615 (numbered according to the human sequence) revealed at least three transcript variants. One transcript was homologous to the mammalian skeletal muscle RYR1 sequence in this region. The second transcript variant (AS-81) was characterized by the absence of 81 bases located at the beginning of exon 13, while the third transcript variant (AS-193) carried a deletion of 193 bases, corresponding to the entire exon 13. Two alphaRYR genomic DNA alleles (alphaRYR-I and alphaRYR-II) carrying the region of deletions in the turkey cDNA sequences were identified. Nucleotide sequence analysis demonstrated that the two alleles are identical in exon sequences but different in intron sequences. Comparison of genomic and cDNA sequences indicated that both AS-81 and AS-193 transcript variants probably arose via alternative splicing. Consistent with this mechanism, the last eight nucleotides of the 81 bases form a consensus sequence for a splice acceptor site. Both alleles could give rise to the AS-81 and AS-193 transcript variants via alternative splicing. Birds homozygous for alphaRYR-II tended to have superior meat quality indicators including significantly higher muscle pH at 15-min post mortem and lower muscle exudate at 24-h post mortem, compared to birds homozygous for alphaRYR-I.