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Genome-wide association study (GWAS) identifies the FecXGr allele in BMP15 segregating in Rasa Aragonesa sheep breed
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International audience. Rasa Aragonesa is an autochthonous Mediterranean sheep breed, mainly reared in extensive or semiextensive farming systems and oriented to meat production. The Cooperative Oviaragon-Grupo Pastores carries out since 1994 a selection program for prolificacy in this breed, with 490,337 controlled ewes at present. A FecX-mutated allele called FecXR in BMP15 gene was described in Rasa Aragonesa sheep breed. This polymorphism causes increased prolificacy in heterozygous and sterility in homozygous ewes. However, highly prolific ewes without the FecXR allele have been found in the population. A genome-wide association study (GWAS) was performed to identify other hyperprolific genetic variants in the Rasa Aragonesa sheep breed. The GWAS was performed with the GCTA software (Yang et al., 2011) using 158 ewes (73 high prolific vs. 85 low prolific ewes) with the Illumina AgResearch Sheep HD (680K) microarray. Ewes having at least 3 lambing records, and without the FecX.R allele were selected from the whole Cooperative Oviaragon-Grupo Pastores database. These ewes came from 33 and 36 different farms for high prolific and low prolific ewes, respectively, and were selected as unrelated as possible based on their pedigree information. A significant association at the genome level (pBonferroni < 0.05) was found for SNP oar3_OAR27_50971170_dup located in BMP15 gene (Oar3.1 X: g. 50971170C > T). This is the FecXGr mutation (NM_001114767.1: c.950C > T) associated with increased prolificacy in other sheep breeds. Only 14 heterozygous animals were found (MAF = 0.04), all of them associated with high prolific ewes. These animals were sequenced for BMP15, finding only the FecXGr allele. No homozygous animals were found for this allele. This allele was first described in Grivette (Demars et al., 2013), and recently in Mouton Vendeen (Chantepie et al., 2018), Romanov, Dorper and Ovella Galega (Vera et al., 2018) sheep breeds. These results could indicate the ancestry of this variant in sheep. The selection program should implement the genotyping of reproducers for the FecXGr allele, to know its frequency and the size of its effects to be able to undertake decisions about its management.
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