Genetic control of multiple births in low ovulating mammalian species

Abstract

In mammals, litter size is a highly variable trait. Some species such as humans or cattle are monotocous, with one or sometimes two newborns per birth, whereas others, the polytocous species such as mice or pigs, are highly prolific and often produce a dozen newborns at each farrowing. In monotocous species, however, two or three newborns per birth may sometime be unwanted. In more polytocous species such as sheep or pigs, litter size is studied in order to increase livestock prolificacy. By contrast, twinning rates in humans or cattle may increase birth difficulties and health problems in the newborns. In this context, the aim of our review was to provide a clearer understanding of the genetic and physiological factors that control multiple births in low-ovulating mammalian species, with particular focus on three species: sheep, cattle, and humans, where knowledge of the ovulation rate in one may enlighten findings in the others. This article therefore reviews the phenotypic and genetic variability observed with respect to ovulation and twinning rates. It then presents the QTL and major genes that have been identified in each species. Finally, we draw a picture of the diversity of the physiological mechanisms underlying multiple ovulation. Although several major genes have been discovered in sheep, QTL detection methods in humans or cattle have suggested that the determinism of litter size is complex and probably involves several genes in order to explain variations in the number of ovulations.

Genome-Wide Association Studies Identify Two Novel BMP15 Mutations Responsible for an Atypical Hyperprolificacy Phenotype in Sheep

“…Genetic studies have indicated that LS and OR can be genetically determined by the action of single genes with a major effect, named fecundity (Fec) genes [38]. All the three Fec genes discovered so far belong to the TGFß superfamily: BMPR1B gene ( FecB ) located on OAR6 [18], [19], [20], GDF9 gene ( FecG ) located on OAR5 [14], [21], [22] and BMP15 gene ( FecX ) located on the X chromosome [13], [14], [15], [16], [17].…”

The Highly Prolific Phenotype of Lacaune Sheep Is Associated with an Ectopic Expression of the B4GALNT2 Gene within the Ovary

“…The finding of non-coding SNPs as causal mutations contrasts with other known mutations affecting ovulation rate through alteration of the coding sequence of BMP15 , GDF9 and BMPR1B genes impairing the protein function [10]. To go further in the fine mapping study, different strategies can be proposed.…”

“…In contrast, plasma concentrations of Follicle Stimulating Hormone (FSH) were not different compared to wild-type ewes. Based on ovarian phenotype and endocrine profiles, these findings suggest that the FecL L mutation affects ovarian function in a different way compared to other known hyperprolificacy-associated mutations, all affecting genes of the bone morphogenetic protein signaling system, BMP15 , GDF9 and BMPR1B [1], [10].…”

Review: Towards the agroecological management of ruminants, pigs and poultry through the development of sustainable breeding programmes. II. Breeding strategies

“…For instance, sheep prion diseases have been virtually eradicated by selecting rams carrying the ARR allele and selecting against the VRQ allele to the PRNP gene involved in resistance to scrapie (Sidani et al, 2010). To increase the meat yield of sheep flocks, the major prolificity genes (Vinet et al, 2012) have also been introgressed or selected in some sheep breeds worldwide.…”