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New insights into polar overdominance in callipyge sheep
Author(s) -
Bidwell C. A.,
Waddell J. N.,
Taxis T. M.,
Yu H.,
Tellam R. L.,
Neary M. K.,
Cockett N. E.
Publication year - 2014
Publication title -
animal genetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.756
H-Index - 81
eISSN - 1365-2052
pISSN - 0268-9146
DOI - 10.1111/age.12132
Subject(s) - biology , genetics , allele , myosin , gene , exon , transcriptome , gene expression , single nucleotide polymorphism , phenotype , genotype , microbiology and biotechnology
Summary The callipyge phenotype in sheep involves substantial postnatal muscle hypertrophy and other changes to carcass composition. A single nucleotide polymorphism in the DLK 1 – DIO 3 imprinted gene cluster alters gene expression of the paternal allele‐specific protein‐coding genes and several maternal allele‐specific long noncoding RNA and micro RNA when the mutation is inherited in cis . The inheritance pattern of the callipyge phenotype is polar overdominant because muscle hypertrophy only occurs in heterozygous animals that inherit a normal maternal allele and the callipyge SNP on the paternal allele ( +/C ). We examined the changes of gene expression of four major transcripts from the DLK 1– DIO 3 cluster and four myosin isoforms during the development of muscle hypertrophy in the semimembranosus as well as in the supraspinatus that does not undergo hypertrophy. The homozygous ( C/C ) animals had an intermediate gene expression pattern for the paternal allele‐specific genes and two myosin isoforms, indicating a biological activity that was insufficient to change muscle mass. Transcriptome analysis was conducted by RNA sequencing in the four callipyge genotypes. The data show that homozygous animals ( C/C ) have lower levels of gene expression at many loci relative to the other three genotypes. A number of the downregulated genes are putative targets of the maternal allele‐specific micro RNA with gene ontology, indicating regulatory and cell signaling functions. These results suggest that the trans ‐effect of the maternal noncoding RNA and associated mi RNA is to stabilize the expression of a number of regulatory genes at a functional, but low level to make the myofibers of homozygous ( C/C ) lambs less responsive to hypertrophic stimuli of the paternal allele‐specific genes.