R-spondin2, a novel target of NOBOX: identification of variants in a cohort of women with primary ovarian insufficiency

Abstract

BackgroundR-spondin2 (Rspo2) is a secreted agonist of the canonical Wnt/β-catenin signaling pathway. Rspo2 plays a key role in development of limbs, lungs and hair follicles, and more recently during ovarian follicle development. Rspo2 heterozygous deficient female mice become infertile around 4 months of age mimicking primary ovarian insufficiency (POI). The study aimed to investigate the regulation of RSPO2 and its potential involvement in pathophysiology of POI.MethodsWe cloned the RSPO2 promoter and performed transcriptional assays to determine if RSPO2 can be regulated by NOBOX, an ovarian transcription factor. Then, we evaluated 100 infertile women after obtaining a detailed history of the disease and follicle-stimulating hormone measurements, besides karyotype determination and fragile-X premutation syndrome investigation. All exons, intron-exon boundaries and untranslated regions of the RSPO2 gene were identified by sequencing, and the results were statistically analyzed.ResultsWe found that RSPO2 can be regulated by NOBOX via the presence of NOBOX Binding Element in its promoter. Among 9 identified variants in POI women, 4 of them were equally homozygous, 4 have never been described (c.-359C > G, c.-190G > A, c.-170 + 13C > T and c.-169-8 T > A), only one c.557 T > C was predicted to alter a single amino acid in the RSPO2 protein (p.Leu186Pro).Conclusions RSPO2 is a novel target gene of the NOBOX key transcription factor, confirming its important role during the follicular growth in ovary. However, RSPO2 mutations are rare or uncommon in women with POI.

R-spondin2 signaling is required for oocyte-driven intercellular communication and follicular growth

“…In the ovary, the regulation of Rspo2 expression is attributed to the oocyte-specific homeobox gene, Nobox as evidenced by microarray analysis of Nobox loss-of-function ovaries showing a downregulation of Rspo2 [47] and by in silico analysis of the Rspo2 promoter revealing the presence of two NOBOX binding elements [48]. However, the ablation of Nobox triggers rapid degeneration of perinatal oocytes, thus impacting the expression of many oocyte-specific genes like Rspo2 [49].…”

“…Considering the fertility defect in heterozygous Rspo2 mutant mice, the severe follicular growth defect in Rspo2 homozygous mutant ovaries and the conservation of RSPO2 expression in ovaries in a little girl, we can assume that RSPO2 is a candidate gene for premature ovarian insufficiency (POI) in women. Bouilly et al [48] previously screened 100 patients suffering from POI and did not associate RSPO2 as a potential cause. This might be due to the heterozygous condition.…”

The chromatin mapping of H3K4me3 and H3K27me3 modification in ovaries during porcine puberty initiation

“…RUXN1, a TF in periovulatory follicles, is induced by an LH surge to transactivate Ptgs2, which is essential for ovulation [40]. Oogenesis homeobox NOBOX encodes a TF that plays a role in folliculogenesis and the regulation of oocyte-speci c genes, among which the target Rsp2 is essential for follicular development [41].…”

The transcriptional regulator CBX2 and ovarian function: A whole genome and whole transcriptome approach

“…Mutations of ESR2 were found to be responsible for 46,XY and 46,XX DSD, both with gonadal dysgenesis 42 . The genes KISS1 and FSHR were related to ovarian diseases like POF and PCOS 43,44 . Recent studies have shown that kisspeptin-1 and its receptor are expressed in the mammalian ovary and are critical for initiating puberty and regulating ovulation in sexually mature females via the central control of the hypothalamic-pituitary-gonadal axis 45 .…”