Wioleta Drobik, Julie Demars, Raffaella Rossetti, Stéphane Fabre, Julien Sarry, Gwenola Tosser-Klopp, Hélène Gilbert, E. Martyniuk, Zuzanna Nowak, Philippe Mulsant, Luca Persani, Loys Bodin, Laboratoire de Génétique Cellulaire (LGC), Institut National de la Recherche Agronomique (INRA)-Ecole Nationale Vétérinaire de Toulouse (ENVT), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, Ecole Nationale Vétérinaire de Toulouse (ENVT), Institut National de la Recherche Agronomique (INRA), Physiologie de la reproduction et des comportements [Nouzilly] (PRC), Institut National de la Recherche Agronomique (INRA)-Institut Français du Cheval et de l'Equitation [Saumur]-Université de Tours (UT)-Centre National de la Recherche Scientifique (CNRS), Université Francois Rabelais [Tours], Institut Français du Cheval et de l'Equitation, Università degli Studi di Milano [Milano] (UNIMI), Warsaw University of Life Sciences (SGGW), Station d'Amélioration Génétique des Animaux (SAGA), This work was supported by grants from France via Agence National pour la Recherche (http://www.agence-nationale-recherche.fr /) (ANR 2010 BLANC grant 160801, MONOPOLY) and EC (FP7/2007–2013), grant 245140, '3SR', Sustainable Solutions for Small Ruminants (http://www.3srbreeding.eu/), WP4 (this publication reflects only the authors' views and the EC is not liable for any use that may be made of the information contained herein), and the DEGERAM Program (FNADT, FEDER, CR Midi Pyrénées, Auvergne et Limousin). This work was partially supported by Telethon Foundation, Italy (grant GGP09126 to LP)., Institut National de la Recherche Agronomique (INRA)-Institut Français du Cheval et de l'Equitation [Saumur]-Université de Tours-Centre National de la Recherche Scientifique (CNRS), and Demars, Julie
Some sheep breeds are naturally prolific, and they are very informative for the studies of reproductive genetics and physiology. Major genes increasing litter size (LS) and ovulation rate (OR) were suspected in the French Grivette and the Polish Olkuska sheep populations, respectively. To identify genetic variants responsible for the highly prolific phenotype in these two breeds, genome-wide association studies (GWAS) followed by complementary genetic and functional analyses were performed. Highly prolific ewes (cases) and normal prolific ewes (controls) from each breed were genotyped using the Illumina OvineSNP50 Genotyping Beadchip. In both populations, an X chromosome region, close to the BMP15 gene, harbored clusters of markers with suggestive evidence of association at significance levels between 1E−05 and 1E−07. The BMP15 candidate gene was then sequenced, and two novel non-conservative mutations called FecXGr and FecXO were identified in the Grivette and Olkuska breeds, respectively. The two mutations were associated with the highly prolific phenotype (pFecXGr = 5.98E−06 and pFecXO = 2.55E−08). Homozygous ewes for the mutated allele showed a significantly increased prolificacy (FecXGr/FecXGr, LS = 2.50±0.65 versus FecX+/FecXGr, LS = 1.93±0.42, p, Author Summary Although causes altering reproductive function and leading to several fertility syndromes in women are various, a clear association between mutations in some members of the TGFβ family (BMP15 and GDF9) and abnormal ovarian phenotype has established the importance of these factors for normal female fertility. Some sheep breeds are naturally prolific since they carry major genes affecting ovulation rate and litter size. These species are therefore unique informative models for the study of reproductive genetics and physiology. Through a GWAS conducted in two sheep breeds using highly prolific ewes as cases and normal prolific ewes as controls, we identified an X chromosome locus close to the BMP15 gene in both breeds. Two novel non-conservative BMP15 mutations, one in each population, located in very well conserved domains of the protein were associated with the phenotype at heterozygous and homozygous status. Moreover, we showed that both mutations altered the BMP15 signaling activity, suggesting a novel kind of BMP15 variant responsible for an atypical high prolificacy, in contrast to all other BMP15 variants described so far. Our findings suggest an additional role of the BMP15 protein in folliculogenesis and could contribute to a better understanding of the pathogenesis of women′s fertility disorders.