Data from: Mapping the four-horned locus and testing the polled locus in three Chinese sheep breeds

Four-horned sheep are an ideal animal model for illuminating the genetic
basis of horn development. The objective of this study was to locate the
genetic region responsible for the four-horned phenotype and to verify a
previously reported polled locus in three Chinese breeds. A genome-wide
association study (GWAS) was performed using 34 two-horned and 32
four-horned sheep from three Chinese indigenous breeds: Altay, Mongolian
and Sishui Fur sheep. The top two significant single nucleotide
polymorphisms (SNPs) associated with the four-horned phenotype were both
located in a region spanning positions 132.6 to 132.7 Mb on sheep
chromosome 2. Similar locations for the four-horned trait were previously
identified in Jacob, Navajo-Churro, Damara and Sishui Fur sheep,
suggesting a common genetic component underlying the four-horned
phenotype. The two identified SNPs were both downstream of the metaxin 2
(MTX2) gene and the HOXD gene cluster. For the top
SNP—OAR2:g.132619300G>A—the strong associations of the AA and AG
genotypes with the four-horned phenotype and the GG genotype with the
two-horned phenotype indicated the dominant inheritance of the four-horned
trait. No significant SNPs for the polled phenotype were identified in the
GWAS analysis, and a PCR analysis for the detection of the 1.8-kb
insertion associated with polled sheep in other breeds failed to verify
the association with polledness in the three Chinese breeds. This study
supports the hypothesis that two different loci are responsible for horn
existence and number. This study contributes to the understanding of the
molecular regulation of horn development and enriches the knowledge of
qualitative traits in domestic animals.