Flow cytometric analysis of FSHR, BMRR1B, LHR and apoptosis in granulosa cells and ovulation rate in merino sheep

Abstract

The aim of the present study was to determine the direct cause of the mutation-induced, increased ovulation rate in Booroola Merino (BB) sheep. Granulosa cells were removed from antral follicles before ovulation and post-ovulation from BB (nZ5) and WT (nZ12) Merino ewes. Direct immunofluorescence measurement of mature cell surface receptors using flow cytometry demonstrated a significant up-regulation of FSH receptor (FSHR), transforming growth factor beta type 1, bone morphogenetic protein receptor (BMPR1B), and LH receptor (LHR) in BB sheep. The increased density of FSHR and LHR provide novel evidence of a mechanism for increasing the number of follicles that are recruited during dominant follicle selection. The compounding increase in receptors with increasing follicle size maintained the multiple follicles and reduced the apoptosis, which contributed to a high ovulation rate in BB sheep. In addition, we report a mutation-independent mechanism of down-regulation to reduce receptor density of the leading dominant follicle in sheep. The suppression of receptor density coincides with the cessation of mitogenic growth and steroidogenic differentiation as part of the luteinization of the follicle. The BB mutation-induced attenuation of BMPR1B signaling led to an increased density of the FSHR and LHR and a concurrent reduction in apoptosis to increase the ovulation rate. The role of BMPs in receptor modulation is implicated in the development of multiple ovulations.Reproduction (2015) 150 151-163

Genome‐wide association study to identify genomic regions affecting prolificacy in Lori‐Bakhtiari sheep

“…; Regan et al . ). The LHCGR gene is located on sheep chromosome 3:75 705 738–75 748 262 with 11 exons (http://www.ensembl.org).…”

“…Recently, it was shown that the Booroola Merino sheep mutation‐induced attenuation of BMPR1B signaling led to an increased density of FSHR and LHR and a concurrent reduction in apoptosis to increase the ovulation rate (Regan et al . ).…”

A polymorphism in the transcriptional regulatory region strongly influences ovine FSHR mRNA decay

“…In female domestic animal, FSHR is exclusively expressed in GCs of the ovary and plays a crucial role in GC proliferation, apoptosis, differentiation, follicle maturation and atresia, and ovulation, which are all involved in reproductive function (Cory, Price, Lefebvre, & Palin, ; Du et al, ; Pan et al, ; Regan et al, ; Wang et al, ). Furthermore, FSHR has been identified as a major candidate gene for assessing the ovulation rate (number of corpora lutea) in pigs from a Duroc and Meishan cross (Sato, Hayashi, & Kobayashi, ).…”

“…In sheep, the mRNA levels of FSHR in ovarian follicles were closely associated with fecundity (Ni et al, ; Wang, ). Importantly, increasing FSHR mRNA level or its density in the follicles or ovaries of sheep carried FecB mutation in the BMPR1B gene (the first identified gene responsible for fecundity in sheep), and is considered to be the main reason for FecB mutation, which affects ovulation rate and litter size (Goyal et al, ; Jia et al, ; Regan et al, ). Furthermore, polymorphisms in the 5′ regulatory region (e.g., g.‐200G>A, g.‐197G>A and g.‐98T>C) and coding region (e.g., c.1235T>C) of the ovine FSHR gene have shown to be significantly associated with litter size (Chu et al, ; Wang, ).…”

“…for FecB mutation, which affects ovulation rate and litter size (Goyal et al, 2017;Jia et al, 2005;Regan et al, 2015). Furthermore, polymorphisms in the 5′ regulatory region (e.g., g.-200G>A, g.-197G>A and g.-98T>C) and coding region (e.g., c.1235T>C) of the ovine FSHR gene have shown to be significantly associated with litter size (Chu et al, 2012;Wang, 2013).…”