Genotyping By SNPs to Identify Carriers of the wg-2 Mutation with a Reduced Linked Candidate Region in Chicken

The objective of this study is to further define the region encompassing the causative mutation of the autosomal recessive wingless-2 mutation (wg-2). Affected homozygous progeny display multisystem developmental abnormalities, most notably absent wings. Phenotypically normal heterozygotes (+/-) are bred inter se after genotype determination by sequencing a tightly-linked variant (SNP 390) with transmission status confirmed by test crossing.

Initial SNP studies in 2004 indicated a candidate region of 2 Mb on GGA 12 in our breeding population which was updated to a size of 260 kb five years ago using a study of mutant (-/-) progeny. However, since no genotype-specific selection criteria were imposed on the breeding scheme beyond SNP 390 genotype, the size of the wg-2 candidate region segregating in the carrier population was unknown. Herein we set out to investigate whether recombination has further reduced the candidate region size in the breeding population. Two carrier populations were screened (2015 and 2014 parents) using twelve SNPs across the 260 kb region.

Results indicate that recombination events have occurred and as such have further reduced the region linked to the wg-2 phenotype to a minimum of 220 kb in the 2014 carriers. Test matings and sequencing at SNPs across that region in the 2015 progeny are under way to determine if additional events have occurred, and results will be reported. As the candidate region shrinks in overall size, additional recombination becomes unlikely and so additional genomic technologies are also being employed to inform candidate gene analyses.