Using a Xenopus expression-cloning screen, Hsu et al. (1998) isolated Gremlin, an antagonist of bone morphogenetic protein
(BMP) signaling that is expressed in the neural crest. Gremlin belongs to a novel gene family that includes the
head-inducing factor Cerberus (OMIM 603777) and the tumor suppressor DAN (OMIM 600613). Hsu et al. (1998) showed that all family
members are secreted proteins and that they act as BMP antagonists in embryonic explants. They also provided support for
the model that Gremlin, Cerberus, and DAN block BMP signaling by binding BMPs, preventing them from interacting with
their receptors. They proposed that Gremlin, Cerberus, and DAN control diverse processes in growth and development by
selectively antagonizing the activities of different subsets of the transforming growth factor (TGF)-beta ligands.
NCBI Summary:
This gene encodes a member of the BMP (bone morphogenic protein) antagonist family. Like BMPs, BMP antagonists contain cystine knots and typically form homo- and heterodimers. The CAN (cerberus and dan) subfamily of BMP antagonists, to which this gene belongs, is characterized by a C-terminal cystine knot with an eight-membered ring. The antagonistic effect of the secreted glycosylated protein encoded by this gene is likely due to its direct binding to BMP proteins. As an antagonist of BMP, this gene may play a role in regulating organogenesis, body patterning, and tissue differentiation. In mouse, this protein has been shown to relay the sonic hedgehog (SHH) signal from the polarizing region to the apical ectodermal ridge during limb bud outgrowth. Alternatively spliced transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Jul 2010]
General function
Ligand, Extracellular binding protein
Comment
Cellular localization
Secreted
Comment
candidate123
Ovarian function
Follicle development, Oocyte maturation, Early embryo development
Comment
BMP signalling in human fetal ovary somatic cells is modulated in a gene-specific fashion by GREM1 and GREM2. Bayne RA et al. (2016) Do changes in the expression of bone morphogenetic proteins (BMPs) 2 and 4, and their antagonists Gremlin1 (GREM1) and Gremlin2 (GREM2) during human fetal ovarian development impact on BMP pathway activity and lead to changes in gene expression that may influence the fate and/or function of ovarian somatic cells? BMPs 2 and 4 differentially regulate gene expression in cultured human fetal ovarian somatic cells. Expression of some, but not all BMP target genes is antagonised by GREM1 and GREM2, indicating the existence of a mechanism to fine-tune BMP signal intensity in the ovary. Leucine-rich repeat-containing G-protein coupled receptor 5 (LGR5), a marker of immature ovarian somatic cells, is identified as a novel transcriptional target of BMP4. Extensive re-organisation of the germ and somatic cell populations in the feto-neonatal ovary culminates in the formation of primordial follicles, which provide the basis for a female's future fertility. BMP growth factors play important roles at many stages of ovarian development and function. GREM1, an extracellular antagonist of BMP signalling, regulates the timing of primordial follicle formation in the mouse ovary, and mRNA levels of BMP4 decrease while those of BMP2 increase prior to follicle formation in the human fetal ovary. Expression of genes encoding BMP pathway components, BMP antagonists and markers of ovarian somatic cells were determined by quantitative (q)RT-PCR in human fetal ovaries (from 8 to 21 weeks gestation) and fetal ovary-derived somatic cell cultures. Ovarian expression of GREM1 protein was confirmed by immunoblotting. Primary human fetal ovarian somatic cell cultures were derived from disaggregated ovaries by differential adhesion and cultured in the presence of recombinant human BMP2 or BMP4, with or without the addition of GREM1 or GREM2. we demonstrate that the expression of BMP antagonists GREM1, GREM2 and CHRD increases in the lead-up to primordial follicle formation in the human fetal ovary, and that the BMP pathway is active in cultured ovarian somatic cells. This leads to differential changes in the expression of a number of genes, some of which are further modulated by GREM1 and/or GREM2. The positive transcriptional regulation of LGR5 (a marker of less differentiated somatic cells) by BMP4 in vitro suggests that increasing levels of GREM1 and reduced levels of BMP4 as the ovary develops in vivo may act to reduce LGR5 levels and allow pre-granulosa cell differentiation. While we have demonstrated that markers of different somatic cell types are expressed in the cultured ovarian somatic cells, their proportions may not represent the same cells in the intact ovary which also contains germ cells. This study extends previous work identifying germ cells as targets of ovarian BMP signalling, and suggests BMPs may regulate the development of both germ and somatic cells in the developing ovary around the time of follicle formation. Not applicable.//////////////////
Impaired Gremlin 1 (GREM1) expression in cumulus cells in young women with diminished ovarian reserve (DOR). Jindal S et al. PURPOSE: A symbiotic relationship between ovarian granulosa cells (GC) and the developing oocyte is critical. Genetic modulations in GC's can lead to reproductive insufficiency, highlighting the role of GC's in reproductive competence. Utilizing gene expression analyses in cumulus GC's, we attempt to enhance our understanding of mechanisms that may contribute to poor reproductive capacity in young women with diminished ovarian reserve (DOR). METHODS: We measured gremlin 1 (GREM1) gene expression in GC's from infertile women <38years undergoing in vitro fertilization in the context of DOR. RESULTS: GREM1, a member of the differential screening-selected gene aberrative in neuroblastoma (DAN) family of genes known for its highly regulated expression pattern during folliculogenesis and a downstream effecter of oocyte-derived growth and differentiation factor 9, was down-regulated 3-fold (-3.08) in women with DOR versus control; down-regulation was confirmed by qRT-PCR (-4.02). CONCLUSION: This is the first demonstration linking differential expression of Gremlin with etiology of infertility in women.
Growth differentiation factor 9 regulates expression of the bone morphogenetic protein antagonist, gremlin.
Pangas SA, et a .
Growth differentiation factor 9 (GDF9) is an oocyte-expressed member of the transforming growth factor {beta }(TGFbeta) superfamily and is required for normal ovarian follicle development and female fertility. GDF9 acts as a paracrine factor and affects granulosa cell physiology. Only a few genes regulated by GDF9 are known. Our microarray analysis has identified gremlin as one of the genes upregulated by GDF9 in cultures of primary granulosa cells. Gremlin is a known member of the Dan family of BMP antagonists, but its expression and function in the ovary is unknown. We have investigated the regulation of gremlin in mouse granulosa cells by GDF9 as well as other members of the TGFb superfamily. GDF9 and BMP4 induce gremlin, but TGFbeta does not. In addition, in cultures of granulosa cells, gremlin negatively regulates BMP4 signaling but not GDF9 activity. The expression of gremlin in the ovary was also examined by in situ hybridization. A distinct change in gremlin mRNA compartmentalization occurs during follicle development and ovulation, indicating a highly regulated expression pattern during folliculogenesis. We propose that gremlin modulates the crosstalk between GDF9 and BMP signaling that is necessary during follicle development since both ligands utilize components of the same signaling pathway.
Human cumulus granulosa cell gene expression: a predictor of fertilization and embryo selection in women undergoing IVF McKenzie LJ, et al .
BACKGROUND: A biochemical marker for embryo development would increase the chance of a successful pregnancy with IVF by optimizing oocyte and embryo selection, and allow fewer embryos to be transferred. In this study, we correlated cumulus granulosa cell gene expression of hyaluronic acid synthase 2 (HAS2), cyclooxygenase 2 (COX2; PTGS2) and gremlin (GREM1) with subsequent embryo development in search of a parameter for embryo selection. METHODS: Cumulus cell gene expression was determined prospectively on eight consecutive patients undergoing IVF with ICSI. Immediately following oocyte retrieval, the cumulus was stripped from the oocyte, and cumulus gene expression for PTGS2, HAS2 and GREM1 was assessed using a one-step real-time quantitative RT-PCR assay. Oocyte quality, fertilization and embryo morphology were correlated to relative gene expression. RESULTS: Gene expression data were available on cumulus cells from 108 oocytes that developed into 70 embryos (64.8% fertilization rate). Cumulus PTGS2, HAS2 and GREM1 expression was higher from oocytes that developed into higher quality embryos (grades 3, 4 and 5) compared with lower quality embryos (grades 1 and 2) (P<0.05, P<0.001 and P<0.001, respectively). HAS2 and GREM1 expression was also higher from the cumulus surrounding oocytes that gave rise to higher grade embryos (P<0.001). The expression of PTGS2 and HAS2 was 6-fold higher, and that of GREM1 was 15-fold higher in cumulus yielding higher grade embryos versus lower grade embryos. CONCLUSION: PTGS2, HAS2 and GREM1 gene expression correlates to morphological and physiological characteristics and provides a novel approach to predict human embryo development. Ultimately, with better predictors of follicular and embryonic health, higher quality embryos can be selected and transferred, reducing higher order pregnancy rates.
Association between human oocyte developmental competence and expression levels of some cumulus genes. Cillo F et al. At present, oocyte selection is mainly based upon morphological criteria but it is generally acknowledged that its reliability requires further improvement. The aim of this study was to determine whether transcript levels in cumulus cells can provide a useful marker of oocyte developmental competence in vitro. A retrospective study was performed on cumulus cells isolated from 90 oocytes retrieved from 45 patients. Upon fertilization, 35 oocytes originated good-quality embryos and 36 developed into poor-quality embryos, whereas 19 failed to be fertilized. Semi-quantitative measurement of hyaluronic acid synthase 2 (HAS2), gremlin1 (GREM1), and pentraxin 3 (PTX3) mRNAs was performed and data for all genes were obtained from all the samples. Cumulus cells isolated from oocytes that originated high-quality embryos on day 3 of culture had HAS2 and GREM1 transcript levels higher than those detected in cells from oocytes that did not fertilize or developed into poor-quality embryos. No differences were observed in PTX3 levels. Results indicate that the measurement of HAS2 and GREM1 levels in cumulus cells would reliably complement the morphological evaluation providing a useful tool for selecting oocytes with greater chances to be fertilized and develop in vitro.
Human cumulus cell gene expression as a biomarker of pregnancy outcome after single embryo transfer. Gebhardt KM et al. OBJECTIVE: To identify the cumulus cell gene expression associated with oocyte developmental competence, specifically live birth, after single ET (SET) assisted reproductive technology. DESIGN: Retrospective gene expression analysis in human cumulus cells from oocytes that established a pregnancy resulting in live birth versus no pregnancy after SET. SETTING: Independent IVF clinic and research institute. PATIENT(S): Women undergoing IVF/intracytoplasmic sperm injection with SET. INTERVENTION(S): Quantitative reverse-transcriptase-polymerase chain reaction analysis was performed on cumulus masses collected before insemination. Oocytes and embryos were cultured and transferred independently in 38 patients undergoing elective SET. Paired cumulus samples from oocytes that developed into high- versus low-grade embryos also were compared. MAIN OUTCOME MEASURE(S): Gene expression profiles of metabolic (ALDOA, LDHA, PFKP, PKM2), signaling (AHR, GREM1, PTGS2, STS), extracellular matrix (HAS2, PTX3, TNFAIP6, VCAN), and loading control GAPDH in individual cumulus masses. RESULT(S): VCAN and PTGS2 mRNA expression was significantly higher in cumulus cells from oocytes yielding a pregnancy resulting in a live birth, while PTX3 mRNA expression trended toward higher expression in pregnant samples. Cumulus cell levels of VCAN, GREM1, and PFKP correlated with birth weight in patients at 38 weeks of gestation. No genes correlated with clinical embryo morphology scores. CONCLUSION(S): Cumulus cell VCAN, PTGS2, GREM1, and PFKP expression may identify oocytes with high developmental potential, leading to enhanced implantation rates and greater developmental capacity throughout gestation.
Expression regulated by
Growth Factors/ cytokines, GDF9
Comment
Ovarian localization
Cumulus, Granulosa, Theca, Stromal cells
Comment
Gremlin-1 and gremlin-2 levels in polycystic ovary syndrome and their clinical correlations. Koroglu N et al. (2019) Gremlin 1 and 2 regulate oocyte primordial follicle transition in animal models. The main objective of this study is to measure the blood levels of Gremlin 1 and 2 in the women with Polycystic Ovary Syndrome (PCOS). We also aimed to evaluate the association of these markers with hormonal and biochemical parameters of PCOS as interrupted folliculogenesis in those women is related to metabolic dysfunction. Fifty women with PCOS were diagnosed according to Rotterdam criteria, and thirty age-matched female controls were included in this prospective study. Gremlin 1 and 2 levels along with hormonal and metabolic parameters were compared between PCOS and control groups. Serum Gremlin 1 levels were significantly higher in the PCOS group than in the control group (p = .001). Gremlin 2 levels were similar between the groups. Besides, there was a significant positive correlation between Gremlin 1 and insulin levels, Homeostasis Model Assessment-Insulin Resistance (HOMA-IR) and waist to hip ratio (WHR) (r = 0.305; r = 0.297; r = 0.303, respectively). Our data suggest that Gremlin 1 may be the key regulator in the pathogenesis of PCOS. In future, Gremlin 1 may be a novel therapeutic target for the treatment of PCOS.//////////////////
Jabara S, et al 2003 reported stromal cells of the human postmenopausal ovary display a
distinctive biochemical and molecular phenotype.
The stroma of the human postmenopausal ovary is postulated to produce androgens,
but evidence for and against this idea exits in the literature. The purpose of this study
was to determine whether key steroidogenic enzymes involved in androgen synthesis
are expressed in the postmenopausal ovarian stroma. Stromal cells were isolated
from postmenopausal ovaries and expression for genes involved in steroidogenesis
[steroidogenic acute regulatory protein (StAR), P450scc, 3beta-hydroxysteroid
dehydrogenase (3beta-HSD) P450c17, and P450c27] as well as for several growth
factor binding proteins [gremlin, IGF binding protein-4, follistatin, and secreted
frizzled-related protein (sFRP)-1 and -4], were compared with cultured human theca
cells and dermal fibroblasts. Follistatin, gremlin, IGF
binding protein-4, and sFRP-1 and -4 transcripts were detected in the stromal cells in
relative amounts significantly higher than theca cells, but not significantly different
from fibroblasts, except for sFRP-1, which was significantly higher in stromal cells.
The observations demonstrate that stromal cells of the postmenopausal ovary have a
signature biochemical and molecular phenotype that can be distinguished from
fibroblasts.
Species: mouse
Mutation name: None
type: null mutation fertility: fertile Comment: Loss of Gremlin Delays Primordial Follicle Assembly but Does Not Affect Female Fertility in Mice. Myers M et al. The transforming growth factor beta (TGFB) protein family is renowned for its diverse roles in developmental biology including reproduction. Gremlin is a member of the differential screening-selected gene aberrative in neuroblastoma (DAN)/cerberus family of bone morphogenetic protein (BMP) antagonists. Recent studies on gremlin focus on its involvement in embryonic skeletal, lung, and kidney development. To define the role of gremlin (Grem1) in female reproduction, we analyzed postnatal folliculogenesis using global and conditional knockout (cKO) mice for gremlin. Grem1(-/-) mice die within 48 h after birth and ovaries collected from neonatal Grem1(-/-) mice demonstrated reduced oocyte numbers and delayed primordial follicle development. Transplanting Grem1(-/-) neonatal ovaries showed that folliculogenesis proceeded to large antral follicle stage, but Grem1(-/-) ovaries contained corpora lutea-like structures not found in control-transplanted ovaries. However, Grem1 cKO mice had comparable fertility to control mice. These data suggest that gremlin plays a previously uncharacterized role in the regulation of oocyte numbers and the timing of primordial follicle development, but is either not required for later folliculogenesis, or its loss is possibly compensated by other BMP antagonists.
SSR 2010 610. The BMP Antagonist Gremlin Is Not Essential for Folliculogenesis
in the Mouse. Michelle Myers, Brooke S. Middlebrooke, Robert W. Cook, and
Stephanie A. Pangas. Baylor College of Medicine, Houston, TX, USA
Members of the transforming growth factor beta superfamily are renowned for
their diverse roles in developmental processes, including folliculogenesis. Bone
morphogenetic proteins (BMPs) are regulated by specific BMP antagonists and
gremlin, a member of the DAN family of BMP antagonists, has been implicated in
reproduction. We hypothesized that ablation of gremlin in the ovary would disrupt
BMP antagonism. Gremlin is present in neonatal ovaries and continues to be
expressed throughout folliculogenesis. To investigate the potential role of gremlin
throughout follicle development, we utilized two mouse models, each unique to a
different stage of folliculogenesis: i) mice globally deficient in gremlin (denoted
Grem1-/-); and ii) mice with granulosa cell deletion of gremlin (denoted Grem1 cKO).
Grem1-/- mice die within 24-48 hours of birth with no obvious differences observed
between wildtype and Grem1-/- neonatal ovaries. Additionally, we transplanted
Grem1-/- neonatal ovaries into ovariectomized adult wildtype mice to study later
follicle development in ovaries devoid of gremlin. Transplanted Grem1-/- ovaries
revealed that folliculogenesis could proceed to large antral follicle development,
suggestive that the loss of gremlin did not alter folliculogenesis. These findings were
further confirmed utilizing Grem1 cKO mice, which demonstrated normal ovarian
folliculogenesis and had comparable fertility to control mice. Analysis of other BMP
antagonists in the ovary demonstrates that multiple related proteins are co-expressed
with gremlin. These data suggest that gremlin is not required for folliculogenesis and
loss of Grem1 in the ovary may be compensated by other BMP antagonists
Species: human
Mutation name: type: naturally occurring fertility: subfertile Comment: New mutations in non-syndromic primary ovarian insufficiency patients identified via whole-exome sequencing. Patiño LC et al. (2017) Is it possible to identify new mutations potentially associated with non-syndromic primary ovarian insufficiency (POI) via whole-exome sequencing (WES)? WES is an efficient tool to study genetic causes of POI as we have identified new mutations, some of which lead to protein destablization potentially contributing to the disease etiology. POI is a frequently occurring complex pathology leading to infertility. Mutations in only few candidate genes, mainly identified by Sanger sequencing, have been definitively related to the pathogenesis of the disease. This is a retrospective cohort study performed on 69 women affected by POI. WES and an innovative bioinformatics analysis were used on non-synonymous sequence variants in a subset of 420 selected POI candidate genes. Mutations in BMPR1B and GREM1 were modeled by using fragment molecular orbital analysis. Fifty-five coding variants in 49 genes potentially related to POI were identified in 33 out of 69 patients (48%). These genes participate in key biological processes in the ovary, such as meiosis, follicular development, granulosa cell differentiation/proliferation and ovulation. The presence of at least two mutations in distinct genes in 42% of the patients argued in favor of a polygenic nature of POI. It is possible that regulatory regions, not analyzed in the present study, carry further variants related to POI. WES and the in silico analyses presented here represent an efficient approach for mapping variants associated with POI etiology. Sequence variants presented here represents potential future genetic biomarkers. This study was supported by the Universidad del Rosario and Colciencias (Grants CS/CIGGUR-ABN062-2016 and 672-2014). Colciencias supported Liliana Catherine Patiño´s work (Fellowship: 617, 2013). The authors declare no conflict of interest.//////////////////