Pregnancy-associated plasma protein A (PAPPA) is a large zinc glycoprotein of placental origin. The amino acid sequence deduced from the cDNA shows conserved motifs resembling the short consensus repeats (SCRs) of complement control proteins. The maternal serum level of PAPPA increased exponentially until term. PAPPA is found in the ovarian follicles, follicular fluid, luteal cells, and fallopian tubes of nonpregnant women. Because low serum levels of PAPPA have been demonstrated in first-trimester pregnancies associated with chromosomally abnormal fetuses, PAPPA has been suggested as a potential biochemical marker for such pregnancies. Lawrence JB, et al. reported that the insulin-like growth factor (IGF)-dependent IGF binding protein-4 protease secreted by human fibroblasts is pregnancy-associated plasma protein-A.
NCBI Summary:
This gene encodes a secreted metalloproteinase which cleaves insulin-like growth factor binding proteins (IGFBPs). Following IGFBP cleavage, insulin growth factors dissociate from IGFBPs and bind to IGF receptors, resulting in activation of the IGF pathway. The encoded protein plays a role in bone formation, inflammation, wound healing and female fertility. Enhanced expression of this protein is associated with diabetic nephropathy in human patients and this protein may promote tumor invasion and growth in various human cancers. [provided by RefSeq, Aug 2017]
Sinosich MJ, et al. identify the IGFBP4 protease in human follicular fluid as pregnancy associated plasma protein-A (PAPP-A) based on distinctive IGFBP-4 cleavage pattern, the same protease inhibitor profile, specific inhibition and immunodepletion of IGFBP-4 protease activity with PAPP-A polyclonal antibodies, and immunorecognition by PAPP-A monoclonal antibodies in ELISA. PAPP-A was also secreted by human granulosa cells, the reputed source of IGFBP-4 protease activity in follicular fluid.
Expression regulated by
FSH, LH, Steroids, Growth Factors/ cytokines
Comment
The proteolytic activity of pregnancy-associated plasma protein-A is potentially regulated by stanniocalcin-1 and -2 during human ovarian follicle development. Jepsen MR et al. (2016) Is the proteolytic activity of pregnancy-associated plasma protein-A (PAPP-A) regulated by the stanniocalcins (STC1 and STC2) during human follicle maturation? The STCs and PAPP-A show similar expression by immunohistochemistry in developing follicles, and regulation of PAPP-A proteolytic activity is suggested by the identification of inhibited protein complexes between PAPP-A and STC1 or STC2 in human follicular fluid (FF). The insulin-like growth factor (IGF)-regulating proteinase PAPP-A is secreted by the granulosa cells of estrogen-dominant follicles and is involved in follicle growth. STC1 and STC2 have recently been identified as novel PAPP-A inhibitors, and their expression in non-human mammalian ovaries has previously been observed. The proteolytic activity of PAPP-A in human follicular fluid was assessed, and the interaction between PAPP-A and the STCs in human ovarian tissues and follicular fluid was analyzed using immunoassays. From 21 women, matched pairs of follicular fluid were obtained from one follicle just prior to final maturation of follicles with human chorionic gonadotrophin (hCG), and from another follicle in connection with oocyte aspiration after hCG treatment. Ovarian tissues were obtained from women having one ovary removed for fertility preservation by cryopreservation prior to gonadotoxic treatment. The concentration and activity of PAPP-A were determined in all samples of follicular fluid. Furthermore, to investigate PAPP-A regulation during follicle development, immunohistochemical staining of PAPP-A, STC1, and STC2 was performed on pre-antral and antral human follicles. To attempt the demonstration of native complexes between PAPP-A and the STCs, immunoprecipitation from a pool of human follicular fluid was performed. The concentration of PAPP-A antigen in follicular fluid increased upon stimulation of ovulation with hCG (P < 0.02), but at the same time, PAPP-A activity was decreased. PAPP-A, STC1, and STC2 were localized together in primordial, late primary, and antral follicles, indicating that complex formation is possible in ovarian tissue. Covalent PAPP-A:STC2 and non-covalent PAPP-A:STC1 complexes were immunoprecipitated from follicular fluid, documenting for the first time native inhibited complexes between PAPP-A and the STCs. We have demonstrated the presence of native complexes between PAPP-A and the STCs in the human ovary, indicating STC-mediated PAPP-A proteolytic inhibition. Further investigation is required to extend this principle to other tissues. Our data suggest that the STCs contribute to PAPP-A regulation during folliculogenesis and support a general model in which STC1 and STC2 are regulators of mammalian IGF activity through inhibition of PAPP-A. We suggest that future functional studies take both PAPP-A and the STCs into consideration. This work was supported by grants from the Novo Nordisk Foundation, and the Danish Council for Independent Research. No competing interests declared.//////////////////
Chandrasekher YA, et al. reported that estrogen- but not androgen-dominant human ovarian follicular fluid contains an insulin-like growth factor binding protein-4 protease.
The effect of follicle stimulating hormone (FSH) and insulin-like growth factors (IGFs) on IGFBP-4 proteolytic activity was studied by Iwashita M et al using granulosa cell cultures. Proteolytic activity was assessed by the incubation of [1251]-IGFBP-4 with medium and cleaved products which were analysed by autoradiography. The iodinated IGFBP-4 was
cleaved into an 18 kDa fragment when cells were incubated with FSH or IGFs while IGFBP-4 remained intact in the control
culture. Inhibition of IGFBP-4 degradation by several protease inhibitors suggests that IGFBP-4 degradation was induced by
a metalloserine protease. Addition of IGFs, but not FSH, to medium from untreated granulosa cell cultures stimulated proteolysis of [1251]-IGFBP-4. Similarly, exogenously added covalently cross-linked [125I]-IGF-II-IGFBP-4 complexes were proteolyzed; however, IGFs did not enhance the degradation of these complexes.
Ovarian localization
Cumulus, Granulosa, Luteal cells
Comment
Cumulus cell pappalysin-1, luteinizing hormone/choriogonadotropin receptor, amphiregulin and hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase 1 mRNA levels associate with oocyte developmental competence and embryo outcomes. Kordus RJ et al. (2019) To determine whether a selected set of mRNA biomarkers expressed in individual cumulus granulosa cell (CC) masses show association with oocyte developmental competence, embryo ploidy status, and embryo outcomes. This prospective observational cohort pilot study assessed levels of mRNA biomarkers in 163 individual CC samples from 15 women stimulated in antagonist cycles. Nineteen mRNA biomarker levels were measured by real-time PCR and related to the development of their corresponding individually cultured oocytes and subsequent embryos, embryo ploidy status, and live birth outcomes. PAPPA mRNA levels were significantly higher in CC from oocytes that led to euploid embryos resulting in live births and aneuploid embryos compared to immature oocytes by ANOVA. LHCGR mRNA levels were significantly higher in CC of oocytes resulting in embryos associated with live birth compared to immature oocytes and oocytes resulting in arrested embryos by ANOVA. Using a general linearized mixed model to assess ploidy status, CC HSD3B mRNA levels in oocytes producing euploid embryos were significantly lower than other oocyte outcomes, collectively. When transferred euploid embryos outcomes were analyzed by ANOVA, AREG mRNA levels were significantly lower and PAPPA mRNA levels significantly higher in CC from oocytes that produced live births compared to transferred embryos that did not form a pregnancy. Collectively, PAPPA, LHCGR, and AREG mRNA levels in CC may be able to identify oocytes with the best odds of resulting in a live birth, and HSD3B1 mRNA levels may be able to identify oocytes capable of producing euploid embryos.//////////////////
Ariel Hourvitz, et al 2002 reported that
PAPP-A mRNA was undetectable in ovaries of untreated
immature 25-d-old mice. Treatment with PMSG led to a marked time-dependent increase in PAPP-A expression in
well-defined subsets of granulosa cells and follicles. Specifically, PAPP-A expression was detectable exclusively in
centrifugally residing membrana granulosa cells of antral follicles during a 3- to 36-h period post PMSG. PAPP-A
expression then fell to nondetectable levels in dominant preovulatory follicles at 48 h post PMSG. Treatment of
PMSG-primed mice with human CG caused a rapid reinduction of PAPP-A expression in granulosa cells of dominant
follicles and was sustained at relatively high levels throughout the ovulation and luteinization. These results suggest a role
for gonadotropin-stimulated PAPP-A gene expression in the physiologic processes of dominant follicle development,
ovulation, and luteogenesis in the mammalian ovary. The early onset and extended duration of gonadotropin-dependent
PAPP-A expression in granulosa cells may serve to degrade the antigonadotropin IGFBP-4. Accordingly, successful antral
follicle development, ovulation, and corpus luteum formation may be contingent on an IGFBP-4-deplete/PAPP-A-replete
circumstance, hence resulting in an IGF-I-replete intrafollicular microenvironment.
Follicle stages
Antral, Preovulatory, Corpus luteum
Comment
Sinosich MJ et al reported that, by radioimmunoassay, pregnancy-associated plasma protein-A (PAPP-A) was undetectable in matched follicular and luteal phase serum samples.
Matsui M, et al show that FSH and oocytes regulate PAPP-A expression in granulosa cells (GCs). By in situ hybridization, ovary PAPP-A mRNA was markedly increased by PMSG treatment, and the message was localized to the membrana GCs (MGC) but not cumulus GCs (CGC) of dominant follicles. To explore mechanism, we used primary cultures of rat GCs. Control (untreated) cells produced little or no PAPP-A spontaneously. Conversely, FSH markedly stimulated PAPP-A mRNA and protein in a dose- and time- dependent fashion. Interestingly, PAPP-A expression in isolated CGC was also strongly induced by FSH, and the induction was inhibited by added oocytes. To investigate the nature of the inhibition, we tested the effect of oocyte-derived BMP-15. BMP-15 alone had no effect on basal levels of PAPP-A expression by cultures of MGC or CGC. However, BMP-15 markedly inhibited the FSH stimulation of PAPP-A production in a dose-dependent manner. The cleavage of IGFBP-4 by conditioned media from FSH-treated GCs was completely inhibited by anti PAPP-A antibody, indicating the IGFBP-4 protease secreted by GCs is PAPP-A. These results demonstrate stimulatory and inhibitory roles for FSH and BMP-15, respectively, in regulating PAPP-A production by GCs. We propose that FSH and oocyte-derived BMP-15 form a controlling network that ensures the spatiotemporal pattern of GC PAPP-A expression in the dominant follicle.
Phenotypes
POF (premature ovarian failure)
Mutations
2 mutations
Species: mouse
Mutation name: None
type: null mutation fertility: subfertile Comment: Lack of Functional Pregnancy-Associated Plasma Protein-A (PAPPA) Compromises Mouse Ovarian Steroidogenesis and Female Fertility. Nyegaard M et al. The insulin-like growth factor (IGF) system plays an important role in regulating ovarian follicular development and steroidogenesis. IGF binding proteins (IGFBP) mostly inhibit IGF actions, and IGFBP proteolysis is a major mechanism for regulating IGF bioavailability. Pregnancy-associated plasma protein-A (PAPPA) is a secreted metalloprotease responsible for cleavage of IGFBP4 in the ovary. The aim of this study was to investigate whether PAPPA plays a role in regulating ovarian functions and female fertility, by comparing the reproductive phenotype of wild type (WT) mice with mice heterozygous or homozygous for a targeted Pappa gene deletion (HET and PAPP-A KO mice, respectively). PAPP-A KO females when mated with WT males demonstrated an overall reduction in average litter size. PAPP-A KO mice had a reduced number of ovulated oocytes, lower serum E(2) levels following eCG administration, lower serum P(4) levels after hCG injection, and reduced expression of ovarian steroidogenic enzyme genes, compared to WT controls. In PAPP-A KO mice, inhibitory IGFBP2, IGFBP3, and IGFBP4 ovarian gene expression was reduced post-gonadotropin stimulation, suggesting some compensation within the ovarian IGF system. Expression levels of follicle stimulating hormone receptor, luteinizing hormone receptor and genes required for cumulus expansion were not affected. Analysis of pre-ovulatory follicular fluid showed complete loss of IGFBP4 proteolytic activity in PAPP-A KO mice, demonstrating no compensation for loss of PAPPA proteolytic activity by other IGFBP proteases in vivo in the mouse ovary. Taken together, these data demonstrate an important role of PAPPA in modulating ovarian function and female fertility by control of the bioavailability of ovarian IGF.
Species: human
Mutation name: None
type: naturally occurring fertility: subfertile Comment: Gene dosage as a relevant mechanism contributing to the determination of ovarian function in Turner syndrome. Castronovo C 2013 et al.
STUDY QUESTION
What is the burden of X chromosome mosaicism in the occurrence of spontaneous menarche (SM) in Turner syndrome (TS)?
SUMMARY ANSWER
SM was significantly associated with X chromosome mosaicism in the TS patients; a mosaicism with around 10% euploid cell line may predict spontaneous pubertal development when determined by molecular-cytogenetic techniques on uncultivated tissues.
WHAT IS KNOWN ALREADY
Spontaneous puberty can be observed in a minority of patients with TS, more frequently, but not exclusively, in those with a high level of 46,XX/45,X mosaicism at standard karyotype. The genetic mechanisms contributing to ovarian function in TS patients are still not determined. However, submicroscopic X-linked and autosomal copy number variations (CNVs) have recently emerged as an important genetic risk category for premature ovarian insufficiency and may be involved in modulating the TS ovarian phenotype.
STUDY DESIGN, SIZE, DURATION
A group of 40 patients with a diagnosis of TS at conventional karyotyping participated in the study; 6 patients had SM and 34 patients had primary amenorrhoea (PA). All clinical data and the patients' DNA samples were collected over the years at a single paediatric clinic.
PARTICIPANTS/MATERIALS, SETTING, METHODS
The patients' samples were used to perform both genetic (Copy Number Assay) and molecular-cytogenetic (array-CGH and iFISH, interphase-FISH) analyses in order to evaluate the X chromosome mosaicism rate and to detect possible rare CNVs of genes with a known or predicted role in female fertility.
MAIN RESULTS AND THE ROLE OF CHANCE
All TS patients showed variable percentages of the 46,XX lineage, but these percentages were higher in the SM group (P < 0.01). A mosaicism around 10% for the euploid cell line may predict spontaneous pubertal development when determined by molecular-cytogenetic techniques performed in uncultivated tissues. A few CNVs involving autosomal and X-linked ovary-related loci were identified by array-CGH analysis and confirmed by real-time quantitative PCR, including a BMP15 gene duplication at Xp11.22, a deletion interrupting the PAPPA gene at 9q33.1, and an intragenic duplication involving the PDE8A gene at 15q25.3.
LIMITATIONS, REASONS FOR CAUTION
This is a pilot study on a relatively small sample size and confirmation in larger TS cohorts may be required. The ovarian tissue could not be studied in any patients and in a subgroup of patients, the mosaicism was estimated in tissues of different embryonic origin.
WIDER IMPLICATIONS OF THE FINDINGS
The combined determination of X chromosome mosaicism by molecular and molecular-cytogenetic techniques may become useful for the prediction of SM in TS. The detection of CNVs in both X-linked and autosomal ovary-related genes further suggests gene dosage as a relevant mechanism contributing to the ovarian phenotype of TS patients. These CNVs may pinpoint novel candidates relevant to female fertility and generate further insights into the mechanisms contributing to ovarian function.
STUDY FUNDING/COMPETING INTEREST(S)
This study was funded by Telethon Foundation (grant no: GGP09126 to L.P.), the Italian Ministry of the University and Research (grant number: 2006065999 to P.F.) and a Ministry of Health grant 'Ricerca Corrente' to IRCCS Istituto Auxologico Italiano (grant number: 08C704-2006). The authors have no conflict of interest to declare.
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