In other species: alpaca

Mendelian trait/disorder: yes

Considered a defect: no

Key variant known: yes

Year key variant first reported: 2017

Mapping: By conducting a GWAS on half-sib families of the Romane breed, involving "two thousands lambs produced from ten unrelated rams", Demars et al. (2017) identified two QTL for fleece variation (woolly vs hairy) on chromosomes OAR13 and 25. Fine-mapping of the latter (larger-effect) QTL narrowed its location to "72 kb (7,435,557–7,508,217 bp".

Molecular basis: Following whole-genome sequencing of "seven selected individuals carrying either the “Q” ancestral hairy allele (Romanov, n = 2), the “q” modern woolly allele (Berrichon du Cher, n = 3) or both (heterozygous QTL sires, n = 2)", Demars et al. (2017) narrowed 18 variants within the candidate region down to one likely causal variant: "the "woolly" allele results from the insertion of an antisense EIF2S2 retrogene (called asEIF2S2) into the 3' UTR of the IRF2BP2 gene leading to an abnormal IRF2BP2 transcript". Demars et al. (2017) reported that this IRF2BP2^asEIF2S2 allele variant "segregated perfectly with the QTLOar25 status for the 8 QTL rams since heterozygous sires were heterozygous for the insertion and homozygous rams were homozygous for the mutated IRF2BP2^asEIF2S2 allele". These same authors also provided "evidence that this chimeric IRF2BP2/asEIF2S2 messenger 1) targets the genuine sense EIF2S2 RNA and 2) creates a long endogenous double-stranded RNA which alters the expression of both EIF2S2 and IRF2BP2 mRNA. This represents a unique example of a phenotype arising via a RNA-RNA hybrid, itself generated through a retroposition mechanism".

Breed: Romane.

Associated gene: