A missense mutation in PFAS (phosphoribosylformylglycinamidine synthase) is likely causal for embryonic lethality associated with the MH1 haplotype in Montbéliarde dairy cattle
Résumé
A candidate mutation in the sex hormone binding globulin gene was proposed in 2013 to be responsible for the MH1 recessive embryonic lethal locus segregating in the Montbéliarde breed. In this follow-up study, we excluded this candidate variant because healthy homozygous carriers were observed in large-scale genotyping data generated in the framework of the genomic selection program. We fine mapped the MH1 locus in a 702-kb interval and analyzed genome sequence data from the 1,000 bull genomes project and 54 Montbéliarde bulls (including 14 carriers and 40 noncarriers). We report the identification of a strong candidate mutation in the gene encoding phosphoribosylformylglycinamidine synthase (PFAS), a protein involved in de novo purine synthesis. This mutation, located in a class I glutamine amidotransferase-like domain, results in the substitution of an arginine residue that is entirely conserved among eukaryotes by a cysteine (p.R1205C). No homozygote for the cysteine-encoding allele was observed in a large population of more than 25,000 individuals despite a 6.7% allelic frequency and 122 expected homozygotes under neutrality assumption. Genotyping of 18 embryos collected from heterozygous parents as well as analysis on nonreturn rates suggested that most homozygous carriers died between 7 and 35 d postinsemination. The identification of this strong candidate mutation will enable the accurate testing of the reproducers and the efficient selection against this lethal recessive embryonic defect in the Montbéliarde breed.