Booroola BMPR1B mutation alters early follicular development and oocyte ultrastructure in sheep

Abstract

Booroola ewes homozygous (BB) for a mutation in the bone morphogenetic protein receptor-1b (BMPR1B) gene exhibit higher ovulation rates, have larger diameter oocytes at earlier stages of follicular development (i.e. Type 3) and smaller diameter follicles at ovulation than wild-type (++) sheep. However, it is not known when BMPR1B is first expressed in the developing ovary or the cell types involved. In addition, the effects of the BMPR1B mutation on primordial (Type 1) follicles or during growth to the Type 3 stage are unknown. In the present study, BB and++fetal ovaries at Days 30-135 of gestation were screened by in situ hybridisation for BMPR1B mRNA. Ovaries from BB and++lambs were examined by microscopy to measure follicular and oocyte ultrastructural characteristics in Type 1-3 follicles. BMPR1B mRNA was observed in ovaries from Day 35 of gestation and was evident in oocytes of newly forming and fully formed Type 1 follicles. In BB animals, the Type 1 follicles had larger mean follicular and oocyte diameters, a greater volume of mitochondria, smooth endoplasmic reticulum and ribosomes and a greater surface area of junctions with the granulosa cells compared with++animals. It is concluded that the BMPR1B mutation alters follicular development from the onset of follicular formation.

Genomic prediction of reproduction traits for Merino sheep

“…; Reader et al . ). We also found SNPs with effects of 1.2 × 10 −3 SD at PGF ( placental growth factor ), CAPN2 ( calpain 2 ) and FGFR1 ( fibroblast growth factor receptor 1 ; Fig.…”

Genome-wide transcriptome analysis of mRNAs and microRNAs in Dorset and Small Tail Han sheep to explore the regulation of fecundity

“…In this study, we performed genome-wide analyses to compare the mRNAs and miRNAs in Dorset sheep and two Small Tail Han sheep containing the FecB mutation (Han BB and Han ++) using RNA-Seq technology. The FecB phenotype, which is associated with a mutation in BMPR1B, has been shown to alter early follicular development and oocyte ultrastructure (Reader et al, 2012), which require protein synthesis and metabolism activities. Through GO and KEGG pathway analyses, we identified genes involved in metabolic activity such as phosphatidylcholine-sterol acyltransferase, ATPase 2C1 and γ-glutamyl kinase, which are differentially expressed in the Han sheep compared to the Dorset sheep.…”

Using sheep lines with mutations in single genes to better understand ovarian function

“…In contrast, BMPR1B mRNA is expressed in the ovary before and during formation of the follicles and the mutation would appear to affect ovarian follicles from the primordial stage onwards. Differences in follicle and oocyte size and cellular organelles have been observed when comparing primordial follicles from ewes homozygous for the Booroola mutation to their wild-type contemporaries (Reader et al 2012). Whether the numbers of follicles formed are influenced by the Booroola mutation is unclear as different studies have drawn different conclusions, with some studies showing increased numbers of follicles (Smith et al 1994) and others indicating that the number of follicles may be reduced in ewes homozygous for the Booroola mutation (Ruoss et al 2009).…”