title: Genome-wide association scan suggests basis for microtia in Awassi sheep.
abstract: Hereditary underdevelopment of the ear, a condition also known as microtia, has been observed in several sheep breeds as well as in humans and other species. Its genetic basis in sheep is unknown. The Awassi sheep, a breed native to southwest Asia, carries this phenotype and was targeted for molecular characterization via a genome-wide association study. DNA samples were collected from sheep in Jordan. Eight affected and 12 normal individuals were genotyped with the Illumina OvineSNP50(®) chip. Multilocus analyses failed to identify any genotypic association. In contrast, a single-locus analysis revealed a statistically significant association (P = 0.012, genome-wide) with a SNP at basepair 34 647 499 on OAR23. This marker is adjacent to the gene encoding transcription factor GATA-6, which has been shown to play a role in many developmental processes, including chondrogenesis. The lack of extended homozygosity in this region suggests a fairly ancient mutation, and the time of occurrence was estimated to be approximately 3000 years ago. Many of the earless sheep breeds may thus share the causative mutation, especially within the subgroup of fat-tailed, wool sheep.
authors.affiliation: Animal Breeding and Genetics, Department of Animal Production, Faculty of Agriculture, Jordan University of Science and Technology (JUST), Irbid, Jordan.
authors.forename: K
authors.initials: K
authors.lastname: Jawasreh
authors.affiliation: Animal Genetic Resources Branch, Animal Production and Health Division, Agriculture and Consumer Protection Department, Food and Agriculture Organization of the United Nations (FAO), 00153, Rome, Italy.
authors.forename: P J
authors.initials: PJ
authors.lastname: Boettcher
authors.affiliation: Parco Tecnologico Padano, 26900, Lodi, Italy.|Institute of Agricultural Biology and Biotechnology, National Research Council, Milan, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Stella
mesh_terms: D000483:Alleles; D000818:Animals; D001947:Breeding; D065817:Congenital Microtia / Q000235:genetics / Q000662:veterinary*; D050993:GATA6 Transcription Factor / Q000235:genetics; D056726:Genetic Association Studies; D005838:Genotype; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D017422:Sequence Analysis, DNA; D012756:Sheep; D012757:Sheep Diseases / Q000235:genetics*; D034561:Sheep, Domestic / Q000235:genetics*
chemical_list: D050993:GATA6 Transcription Factor
keywords: Jordan; earlessness; genome-wide association study; ovine