Screening for causative mutations in ovine BMPR1B and BMP15 genes and their homologous fragments in human

PURPOSE

The BMPR1B and BMP15 genes are well known for their considerable associations with prolificacy in sheep. These genes may also affect fertility or prolificacy in other species, including human. This study was conducted to investigate possible causative mutations in BMPR1B and BMP15 genes in human and an indigenous breed of sheep.

METHODS

Blood samples were collected from 83 singleton- and prolific Mehraban ewes and 81 infertile, singleton- and twin-bearing women. A 190-bp fragment, containing the FecB mutation in ovine BMPR1B, a 380-bp fragment in ovine BMP15 gene and their homologous fragments in human were amplified and then investigated by single-stranded conformation polymorphism and DNA sequencing methods.

RESULTS

The FecB mutation of BMPR1B (g.159A>G) was detected in the sheep population, but no polymorphic loci were found in the homologous fragment in studied human samples. The studied fragments of BMP15 were monomorphic in both sheep and human samples. A total of nine and 69 point-differences in the studied fragments of BMPR1B and BMP15 genes were detected between the species, respectively. In sheep, the G allele of BMPR1B had a positive effect on litter size (p<0.05), whereby all AG or GG ewes were prolific.

CONCLUSION

The FecB mutation for the first time was detected in Mehraban sheep and therefore could be considered for marker-assisted selection in this breed. The studied fragments of BMPR1B and BMP15 genes are not responsible for reproduction variation in human. More studies on other genes, associated with fertility in human, are necessary in the future.

Effects of New Mutations in BMPRIB, GDF9, BMP15, LEPR, and B4GALNT2 Genes on Litter Size in Sheep

Prolificacy is a crucial characteristic of livestock, particularly for species such as sheep that have many births. The objectives of this study were as follows: (1) to investigate the genetic diversity of the 13 new and 7 known variants in the BMPRIB, GDF9, BMP15, LEPR, and B4GALNT2 genes in Ujimqin (UM), the F1 population of Dorper × Ujimqin crossbred (DPU), the F1 population of Suffolk × Ujimqin crossbred (SFKU), Sonid sheep (SN), Tan sheep (Tan), Hu sheep (Hu), and Small-tailed Han sheep (STH) sheep breeds/populations; (2) to perform an association analysis of the above 20 variants with litter size in 325 UM, 304 DPU, and 66 SFKU sheep populations; (3) to compare the frequencies of the litter-size-related alleles of these 20 variants among 8 sheep breeds/populations (the above seven sheep breeds + Mongolia sheep breed). With the use of the Sequenom MassARRAY®SNP assay technology, these 20 mutations were genotyped. The association analysis results showed that the c.746A>G (FecB) mutation in BMPR1B was significantly associated with the litter size of UM and DPU, the c.994A>G (FecGA) in GDF9 was significantly associated with the litter size of SFKU, and the c.31_33CTTinsdel (B1) in BMP15 was significantly associated with the litter size of UM. Our findings might provide valuable genetic markers for expanding sheep litter sizes.

Effects of novel variants in BMP15 gene on litter size in Mongolia and Ujimqin sheep breeds

Reproductive traits, such as ovulation rate and litter size, are important factors influencing the sheep industry. The bone morphogenetic protein 15 (BMP15) is a major gene affecting the reproductive traits in sheep, and multiple mutations in BMP15 gene could affect the ovulation rate and litter size in many sheep breeds, showing high breed specificity. However, identification of novel variations and seeking breed-specific markers associated with litter size in other sheep breeds are still important. In this study, we sequenced the BMP15 gene of Mongolia sheep, and 12 novel variants were detected by direct sequencing and whole-genome resequencing. Among them, the g.50985975 G > A polymorphism in intron and synonymous c.755 T > C (Leu252Pro) in exon 2 of BMP15 were significantly associated with the litter sizes of Mongolia ewes (P < 0.01 and P < 0.01, respectively), as well as the g.50988478C > A and g.50987863G > A in the promoter region of BMP15 were significantly associated with the litter sizes of Ujimqin ewes (P < 0.05 and P < 0.01, respectively). The c.755 T > C mutation is predicted to change the tertiary structure of BMP15. Our findings may provide potentially useful genetic markers for increasing litter size in sheep.

The Identification of Mutation in BMP15 Gene Associated with Litter Size in Xinjiang Cele Black Sheep

The Bone Morphogenetic Protein 15 (BMP15) gene is known to have multiple single-nucleotide polymorphism sites associated with sheep fecundity. This study used gene sequence analysis and mutation detection assays for BMP15 by using 205 blood samples of ewes with known lambing records. Sequence analysis showed that mutation B1 missed the CTT base in exon 1 at positions 28-30, leading to a leucine deletion in the BMP15 protein. Litter size of ewes differed significantly between BB and B+ genotypes of B1 (p < 0.05); however, the differences between wild genotype (++) and homozygous (BB) or wild genotype (++) and heterozygous (B+) were not significant (p > 0.05). Another mutation, T755C, is a T-to-C base change at position 755 of exon 2, resulting in leucine replacement by proline at this position of the BMP15 protein (p.L252P). Two genotypes were identified in the flock: heterozygous (E+) and wild-type genotype (++). Ewes with heterozygous (E+) p.L252P had significantly larger litter sizes than those with the wild-type genotype (p < 0.05). Comprehensive analysis suggests that p.L252P is a mutation that affects fecundity in Cele black sheep.

Frequency of BMP15 and GDF9 mutations increasing litter size and their phenotypic effects in Olkuska sheep population

Two mutations affecting the ovulation rate and litter size are segregating in Olkuska sheep population, FecXO in the BMP15 gene, and the G7 site mutation in GDF9 gene. Homozygous carriers of both mutations are hyperprolific, contrary to the sterility observed in homozygous carriers of most other BMP15 and GDF9 mutations. The objective of this study was to assess frequency and phenotypic effects of both mutations. Blood samples were obtained from 740 individuals, 111 rams and 629 ewes, out of which 91 rams and 561 ewes were successfully genotyped for the BMP15 and GDF9 loci. The reproductive performance included a number of lambs born/born alive and a number of lambs reared until 60 days of age, and for a subset of ewe ovulation rates. The study proved a high frequency of the FecXO mutation in two flocks that have been selected for many years for increased litter size (0.7–1.0 in breeding ewes and rams respectively), and a moderate frequency in another 19 private flocks (0.4–0.5). The frequency of the GDF9 mutation was low, with only 50 sheep out of 312 genotyped being carriers of the GDF9/G7 mutation, including three homozygous carriers. The FecXO mutation in the BMP15 had a significant effect on both litter size and the ovulation rate. The single copy in heterozygous carriers increased litter size by 0.255 (0.063), while the effect of two copies in homozygous genotypes was +0.874 (0.081) lambs born. Due to the low frequency of the GDF9 mutation, it can only be preliminarily concluded that litter size has been increased in double carriers of both the BM15 and GDF9 mutation, which may suggest their additive interaction. The positive effect of both mutations supports their direct use in selection programmes.

Genome-Wide Identification of a Regulatory Mutation in BMP15 Controlling Prolificacy in Sheep

The search for the genetic determinism of prolificacy variability in sheep has evidenced several major mutations in genes playing a crucial role in the control of ovulation rate. In the Noire du Velay (NV) sheep population, a recent genetic study has evidenced the segregation of such a mutation named FecL L . However, based on litter size (LS) records of FecL L non-carrier ewes, the segregation of a second prolificacy major mutation was suspected in this population. In order to identify this mutation, we have combined a case/control genome-wide association study with ovine 50k SNP chip genotyping, whole genome sequencing, and functional analyses. A new single nucleotide polymorphism (OARX:50977717T > A, NC_019484) located on the X chromosome upstream of the BMP15 gene was evidenced to be highly associated with the prolificacy variability (P = 1.93E-11). The variant allele was called FecX N and shown to segregate also in the Blanche du Massif Central (BMC) sheep population. In both NV and BMC, the FecX N allele frequency was estimated close to 0.10, and its effect on LS was estimated at +0.20 lamb per lambing at the heterozygous state. Homozygous FecX N carrier ewes were fertile with increased prolificacy in contrast to numerous mutations affecting BMP15. At the molecular level, FecX N was shown to decrease BMP15 promoter activity and supposed to impact BMP15 expression in the oocyte. This regulatory action was proposed as the causal mechanism for the FecX N mutation to control ovulation rate and prolificacy in sheep.

Genome-wide scans identify known and novel regions associated with prolificacy and reproduction traits in a sub-Saharan African indigenous sheep (Ovis aries)

Maximizing the number of offspring born per female is a key functionality trait in commercial- and/or subsistence-oriented livestock enterprises. Although the number of offspring born is closely associated with female fertility and reproductive success, the genetic control of these traits remains poorly understood in sub-Saharan Africa livestock. Using selection signature analysis performed on Ovine HD BeadChip data from the prolific Bonga sheep in Ethiopia, 41 candidate regions under selection were identified. The analysis revealed one strong selection signature on a candidate region on chromosome X spanning BMP15, suggesting this to be the primary candidate prolificacy gene in the breed. The analysis also identified several candidate regions spanning genes not reported before in prolific sheep but underlying fertility and reproduction in other species. The genes associated with female reproduction traits included SPOCK1 (age at first oestrus), GPR173 (mediator of ovarian cyclicity), HB-EGF (signalling early pregnancy success) and SMARCAL1 and HMGN3a (regulate gene expression during embryogenesis). The genes involved in male reproduction were FOXJ1 (sperm function and successful fertilization) and NME5 (spermatogenesis). We also observed genes such as PKD2L2, MAGED1 and KDM3B, which have been associated with diverse fertility traits in both sexes of other species. The results confirm the complexity of the genetic mechanisms underlying reproduction while suggesting that prolificacy in the Bonga sheep, and possibly African indigenous sheep is partly under the control of BMP15 while other genes that enhance male and female fertility are essential for reproductive fitness.