New Anti-Müllerian Hormone Target Genes Involved in Granulosa Cell Survival in Women With Polycystic Ovary Syndrome

PURPOSE

A protective effect of anti-Müllerian hormone (AMH) on follicle atresia was recently demonstrated using long-term treatments, but this effect has never been supported by mechanistic studies. This work aimed to gain an insight into the mechanism of action of AMH on follicle atresia and on how this could account for the increased follicle pool observed in women with polycystic ovary syndrome (PCOS).

METHODS

In vivo and in vitro experiments were performed to study the effects of AMH on follicle atresia and on the proliferation and apoptosis of granulosa cells (GCs). RNA-sequencing was carried out to identify new AMH target genes in GCs. The expression of some of these genes in GCs from control and PCOS women was compared using microfluidic real time quantitative RT-PCR.

RESULTS

A short-term AMH treatment prevented follicle atresia in prepubertal mice. Consistent with this result, AMH inhibited apoptosis and promoted proliferation of different models of GCs. Moreover, integrative biology analyses of 965 AMH target genes identified in 1 of these GC models, confirmed that AMH had initiated a gene expression program favoring cell survival and proliferation. Finally, on 43 genes selected among the most up- and down-regulated AMH targets, 8 were up-regulated in GCs isolated from PCOS women, of which 5 are involved in cell survival.

MAIN CONCLUSIONS

Our results provide for the first time cellular and molecular evidence that AMH protects follicles from atresia by controlling GC survival and suggest that AMH could participate in the increased follicle pool of PCOS patients.

Prenatal programming by testosterone of follicular theca cell functions in ovary

In mammalian ovaries, the theca layers of growing follicles are critical for maintaining their structural integrity and supporting androgen synthesis. Through combining the postnatal monitoring of ovaries by abdominal magnetic resonance imaging, endocrine profiling, hormonal analysis of the follicular fluid of growing follicles, and transcriptomic analysis of follicular theca cells, we provide evidence that the exposure of ovine fetuses to testosterone excess activates postnatal follicular growth and strongly affects the functions of follicular theca in adulthood. Prenatal exposure to testosterone impaired androgen synthesis in the small antral follicles of adults and affected the expression in their theca cells of a wide array of genes encoding extracellular matrix components, their membrane receptors, and signaling pathways. Most expression changes were uncorrelated with the concentrations of gonadotropins, steroids, and anti-Müllerian hormone in the recent hormonal environment of theca cells, suggesting that these changes rather result from the long-term developmental effects of testosterone on theca cell precursors in fetal ovaries. Disruptions of the extracellular matrix structure and signaling in the follicular theca and ovarian cortex can explain the acceleration of follicle growth through altering the stiffness of ovarian tissue. We propose that these mechanisms participate in the etiology of the polycystic ovarian syndrome, a major reproductive pathology in woman.

Transcriptome analysis of ovine granulosa cells reveals differences between small antral follicles collected during the follicular and luteal phases

Ovarian follicular growth occurs in both the follicular and luteal phases of the estrous cycle but in very different endocrine contexts. In both phases, many small antral follicles with similar morphologic and histologic characteristics are present within the ovaries as a reserve for the terminal folliculogenesis. However, there are several gaps in our molecular knowledge of the gene expression profiles of small antral follicles in the follicular and luteal phases. The aim of the present study was to use RNA sequencing to compare and analyze the global transcriptional profile of ovine granulosa cells collected from small antral follicles (1-3 mm) either during the follicular or the luteal phase of the estrous cycle, with the hypothesis that they should be differential. We identified 663 genes whose mRNA was differentially expressed or accumulated in the granulosa cell layer of small antral follicles in the two phases. A comprehensive interpretation of these data was performed through integrative analyses (Gene Ontology, Ingenuity Pathway Analysis) and the exploitation of already available transcriptomic data on follicular growth and atresia. In particular, we observed that the contrasted endocrine context between follicular and luteal phases may have an impact on estradiol, follicle-stimulating hormone (FSH), and on the activin/inhibin signaling pathways. Furthermore, we reveal the possible initiation of early follicular atresia in small antral follicles during the follicular phase in interaction with the presence of immune cells. This study provides new insights into the gene expression profile in ovine granulosa cells, and we suggest that these molecular changes may have an implication at the time of follicle selection.

Detection of QTL controlling metabolism, meat quality, and liver quality traits of the overfed interspecific hybrid mule duck

The mule duck, an interspecific hybrid obtained by crossing common duck (Anas platyrhynchos) females with Muscovy (Cairina moschata) drakes, is widely used for fatty liver production. The purpose of the present study was to detect and map single and pleiotropic QTL that segregate in the common duck species, and influence the expression of traits in their overfed mule duck offspring. To this end, we generated a common duck backcross (BC) population by crossing Kaiya and heavy Pekin experimental lines, which differ notably in regard to the BW and overfeeding ability of their mule progeny. The BC females were mated to Muscovy drakes and, on average, 4 male mule ducks hatched per BC female (1600 in total) and were measured for growth, metabolism during growth and the overfeeding period, overfeeding ability, and the quality of their breast meat and fatty liver. The phenotypic value of BC females was estimated for each trait by assigning to each female the mean value of the phenotypes of her offspring. Estimations allowed for variance, which depended on the number of male offspring per BC and the heritability of the trait considered. The genetic map used for QTL detection consisted of 91 microsatellite markers aggregated into 16 linkage groups (LG) covering a total of 778 cM. Twenty-two QTL were found to be significant at the 1% chromosome-wide threshold level using the single-trait detection option of the QTLMap software. Most of the QTL detected were related to the quality of breast meat and fatty liver: QTL for meat pH 20 min post mortem were mapped to LG4 (at the 1% genome-wide significance level), and QTL for meat lipid content and cooking losses were mapped to LG2a. The QTL related to fatty liver weight and liver protein and lipid content were for the most part detected on LG2c and LG9. Multitrait analysis highlighted the pleiotropic effects of QTL in these chromosome regions. Apart from the strong QTL for plasma triglyceride content at the end of the overfeeding period mapped to chromosome Z using single-trait analysis, all metabolic trait QTL were detected with the multitrait approach: the QTL mapped to LG14 and LG21 affected the plasma cholesterol and triglyceride contents, whereas the QTL mapped to LG2a seemed to impact glycemia and the basal plasma corticosterone content. A greater density genetic map will be needed to further fine map the QTL.

Retinoic acid activates myogenesis in vivo through Fgf8 signalling

Retinoic acid (RA) has been shown to regulate muscle differentiation in vitro. Here, we have investigated the role of RA signalling during embryonic myogenesis in zebrafish. We have altered RA signalling from gastrulation stages onwards by either inhibiting endogenous RA synthesis using an inhibitor of retinaldehyde dehydrogenases (DEAB) or by addition of exogenous RA. DEAB reduces expression of the myogenic markers myoD and myogenin in somites, whereas RA induces increased expression of these genes and strongly induces premature myoD expression in the presomitic mesoderm (psm). The expression dynamics of myf5 in presomitic and somitic mesoderm suggest that RA promotes muscle differentiation, a role supported by the fact that RA activates expression of fast myosin, while DEAB represses it. We identify Fgf8 as a major relay factor in RA-mediated activation of myogenesis. We show that fgf8 expression in somites and anterior psm is regulated by RA, and find that in the absence of Fgf8 signalling in the acerebellar mutant RA fails to promote myoD expression. We propose that, in the developing embryo, localised synthesis of RA by Raldh2 in the anterior psm and in somites activates fgf8 expression which in turn induces the expression of myogenic genes and fast muscle differentiation.

Corticosteroid Binding Globulin: A New Target for Cortisol-Driven Obesity

We present data suggesting that corticosteroid-binding globulin (CBG) may be the causal gene of a previously identified quantitative trait locus (QTL) associated with cortisol levels, fat, and muscle content in a pig intercross. Because Cbg in human and mouse maps in the region orthologous to the pig region containing this QTL, we considered Cbg as an interesting positional candidate gene because CBG plays a major role in cortisol bioavailability. Firstly, we cloned pig Cbg from a bacterial artificial chromosome library and showed by fluorescent in situ hybridization and radiation hybrid mapping that it maps on 7q26 at the peak of the QTL interval. Secondly, we detected in a subset of the pig intercross progeny a highly significant genetic linkage between CBG plasma binding capacity values and the chromosome 7 markers flanking the cortisol-associated QTL. In this population, CBG capacity is correlated positively to fat and negatively to muscle content. Thirdly, CBG capacity was three times higher in Meishan compared with Large White parental breeds and a 7-fold difference was found in Cbg mRNA expression between the two breeds. Overall, the data accumulated in this study point to Cbg gene as a key regulator of cortisol levels and obesity susceptibility.

A refined comparative map between porcine chromosome 13 and human chromosome 3

We report here the localisation of BAIAP1 (13q24), HTR1F (13q45), PTPRG (13q23) and UBE1C (13q24) by fluorescence in situ hybridisation (FISH), and BAIAP1 (Swr2114; 21 cR; LOD = 11.03), GATA2 (Sw2448; 37 cR; LOD = 8.26), IL5RA (Swr2114; 64 cR; LOD = 3.85), LMCD1 (Sw2450; 61 cR; LOD = 4.73), MME (CP; 50 cR; LOD = 7.75), RYK (Swc22; 12 cR; LOD = 18.62) and SGU003 (Sw1876; 6 cR; LOD = 16.99) by radiation hybrid (RH) mapping to porcine chromosome 13 (SSC13). The mapping of these 10 different loci (all mapped to human chromosome 3; HSA3) not only confirms the extended conservation of synteny between HSA3 and SSC13, but also defines more precisely the regions with conserved linkage. The syntenic region of the centromeric part of SSC13 was determined by isolating porcine bacterial artificial chromosome (BAC) clones (842D4 and 1031H1) using primers amplifying porcine microsatellite markers S0219 and S0076 (mapped to this region). Sequence comparison of the BAC end sequences with the human genome sequence showed that the centromeric part of SSC13 is homologous with HSA3p24.

Integration of porcine chromosome 13 maps

In order to expand the comparative map between human chromosome 3 (HSA3) and porcine chromosome 13 (SSC13), seven genes from HSA3 were mapped on SSC13 by fluorescence in situ hybridisation (FISH), viz. ACAA1, ACPP, B4GALT4, LTF, MYLK, PDHB and RARB. With a view to integrating this expanded comparative map with the existing SSC13 linkage map, we used the INRA-University of Minnesota porcine Radiation Hybrid panel (IMpRH) to localize more precisely and to order 15 genes on the SSC13 map, viz. ACPP, ADCY5, APOD, BCHE, CD86, DRD3, GAP43, PCCB, RAF1, RHO, SI, TF, TFRC, TOP2B and ZNF148. In this way, we were able to create an integrated map, containing 38 type I and 81 type II markers, by correlating the linkage, radiation hybrid (RH) and cytogenetic maps of SSC13. This integrated map will give us the opportunity to take maximal advantage of the comparative mapping strategy for positional candidate cloning of genes responsible for economically important traits.

Radiation hybrid comparative mapping between human chromosome 17 and porcine chromosome 12 demonstrates conservation of gene order

A comparative study of human chromosome 17 (HSA17) and pig chromosome 12 (SSC12) was conducted using both somatic cell hybrid panel (SCHP) and radiation hybrid (RH) panel analysis. Sequences from an expressed sequence tag (EST) project in pig reproduction were examined and six genes and ESTs originally believed to map to HSA17 were selected for this study. The genes/ESTs were TATA box binding protein-associated factor (TAF2N/RBP56), alpha-2-plasmin inhibitor (SERPINF2/PLI), H3 histone family 3B (H3F3B), aminopeptidase puromycin sensitive (NPEPPS), an expressed sequence tag (ESTMI015) and P311 protein (P311). The SCHP analysis mapped five genes/ESTs (TAF2N, H3F3B, SERPINF2, NPEPPS and ESTMI015) to SSC12q11-q15 and SSC12p11-p15 with 100% concordance, and assigned P311 to SSC2 (1/2q24)-q29 with 100% concordance. Radiation hybrid analysis of all six genes confirmed the SCHP mapping results, with average retention frequency of 25%. Recent human sequence data demonstrated that P311 is actually located on HSA5q. As HSA5q and SSC2q show conserved syntenic regions predicted from bi-directional painting, our P311 mapping data is consistent with these results. An expanded comparative SSC12 RH map integrating the five new type I markers and 23 previously mapped loci was established using a LOD score threshold of 4.8. The gene order of the five genes/ESTs on the SSC12 framework RH map (H3F3B-ESTMI015-NPEPPS-TAF2N-SERPINF2) is identical to the HSA17 GB4 map but with inversion of the map as conventionally drawn.

In the QTL region surrounding porcine MHC, gene order is conserved with human genome

On the porcine genome, the region surrounding the Major Histocompatibility Complex, also called Swine Leukocyte Antigens (SLA), is of particular interest not only owing to itq role in the control of immune response, but also because of its influence on many traits such as growth, fatness, and meat quality. To help in the identification of responsible genes, detailed comparative maps of the MHC region in mammalian species and powerful mapping tools allowing accurate ordering of genes and markers in this region are needed. In this report, we describe the use of the recently developed IMpRH radiation hybrid panel, to construct a higher density radiation hybrid map of swine Sscr 7p-q12, containing 23 additional loci. Our results show that the gene order is conserved between the two MHC-containing regions, even if an inversion is observed above the QTL region in the region containing DEK, SCA1, and EDN1 genes. The framework map produced shows that the IMpRH panel permits the ordering of genes and markers in the three MHC classes and would thus allow accurate localization of ESTs and candidate genes.