Common variants increase risk for congenital diaphragmatic hernia within the context of de novo variants.

Congenital diaphragmatic hernia (CDH) is a severe congenital anomaly often accompanied by other structural anomalies and/or neurobehavioral manifestations. Rare de novo protein-coding variants and copy-number variations contribute to CDH in the population. However, most individuals with CDH remain genetically undiagnosed. Here, we perform integrated de novo and common-variant analyses using 1,469 CDH individuals, including 1,064 child-parent trios and 6,133 ancestry-matched, unaffected controls for the genome-wide association study. We identify candidate CDH variants in 15 genes, including eight novel genes, through deleterious de novo variants. We further identify two genomic loci contributing to CDH risk through common variants with similar effect sizes among Europeans and Latinx. Both loci are in putative transcriptional regulatory regions of developmental patterning genes. Estimated heritability in common variants is ∼19%. Strikingly, there is no significant difference in estimated polygenic risk scores between isolated and complex CDH or between individuals harboring deleterious de novo variants and individuals without these variants. The data support a polygenic model as part of the CDH genetic architecture.

PLS3 missense variants affecting the actin-binding domains cause X-linked congenital diaphragmatic hernia and body-wall defects.

Congenital diaphragmatic hernia (CDH) is a relatively common and genetically heterogeneous structural birth defect associated with high mortality and morbidity. We describe eight unrelated families with an X-linked condition characterized by diaphragm defects, variable anterior body-wall anomalies, and/or facial dysmorphism. Using linkage analysis and exome or genome sequencing, we found that missense variants in plastin 3 (PLS3), a gene encoding an actin bundling protein, co-segregate with disease in all families. Loss-of-function variants in PLS3 have been previously associated with X-linked osteoporosis (MIM: 300910), so we used in silico protein modeling and a mouse model to address these seemingly disparate clinical phenotypes. The missense variants in individuals with CDH are located within the actin-binding domains of the protein but are not predicted to affect protein structure, whereas the variants in individuals with osteoporosis are predicted to result in loss of function. A mouse knockin model of a variant identified in one of the CDH-affected families, c.1497G>C (p.Trp499Cys), shows partial perinatal lethality and recapitulates the key findings of the human phenotype, including diaphragm and abdominal-wall defects. Both the mouse model and one adult human male with a CDH-associated PLS3 variant were observed to have increased rather than decreased bone mineral density. Together, these clinical and functional data in humans and mice reveal that specific missense variants affecting the actin-binding domains of PLS3 might have a gain-of-function effect and cause a Mendelian congenital disorder.

A screen of repurposed drugs identifies AMHR2/MISR2 agonists as potential contraceptives.

We identified the anti-Mullerian hormone (also known as Müllerian inhibiting substance or MIS) as an inhibitory hormone that induces long-term contraception in mammals. The type II receptor to this hormone, AMHR2 (also known as MISR2), represents a promising druggable target for the modulation of female reproduction with a mechanism of action distinct from steroidal contraceptives. We designed an in vitro platform to screen and validate small molecules that can activate MISR2 signaling and suppress ovarian folliculogenesis. Using a bone morphogenesis protein (BMP)­response element luciferase reporter cell­based assay, we screened 5,440 compounds from a repurposed drug library. Positive hits in this screen were tested for specificity and potency in luciferase dose­response assays, and biological activity was tested in ex vivo Mullerian duct regression bioassays. Selected candidates were further evaluated in ex vivo follicle/ovary culture assays and in vivo in mice and rats. Here, we report that SP600125, CYC-116, gandotinib, and ruxolitinib can specifically inhibit primordial follicle activation and repress folliculogenesis by stimulating the MISR2 pathway.

Rare and de novo variants in 827 congenital diaphragmatic hernia probands implicate LONP1 as candidate risk gene.

Congenital diaphragmatic hernia (CDH) is a severe congenital anomaly that is often accompanied by other anomalies. Although the role of genetics in the pathogenesis of CDH has been established, only a small number of disease-associated genes have been identified. To further investigate the genetics of CDH, we analyzed de novo coding variants in 827 proband-parent trios and confirmed an overall significant enrichment of damaging de novo variants, especially in constrained genes. We identified LONP1 (lon peptidase 1, mitochondrial) and ALYREF (Aly/REF export factor) as candidate CDH-associated genes on the basis of de novo variants at a false discovery rate below 0.05. We also performed ultra-rare variant association analyses in 748 affected individuals and 11,220 ancestry-matched population control individuals and identified LONP1 as a risk gene contributing to CDH through both de novo and ultra-rare inherited largely heterozygous variants clustered in the core of the domains and segregating with CDH in affected familial individuals. Approximately 3% of our CDH cohort who are heterozygous with ultra-rare predicted damaging variants in LONP1 have a range of clinical phenotypes, including other anomalies in some individuals and higher mortality and requirement for extracorporeal membrane oxygenation. Mice with lung epithelium-specific deletion of Lonp1 die immediately after birth, most likely because of the observed severe reduction of lung growth, a known contributor to the high mortality in humans. Our findings of both de novo and inherited rare variants in the same gene may have implications in the design and analysis for other genetic studies of congenital anomalies.

A Tracheal Aspirate-derived Airway Basal Cell Model Reveals a Proinflammatory Epithelial Defect in Congenital Diaphragmatic Hernia.

Rationale: Congenital diaphragmatic hernia (CDH) is characterized by incomplete closure of the diaphragm and lung hypoplasia. The pathophysiology of lung defects in CDH is poorly understood. Objectives: To establish a translational model of human airway epithelium in CDH for pathogenic investigation and therapeutic testing. Methods: We developed a robust methodology of epithelial progenitor derivation from tracheal aspirates of newborns. Basal stem cells (BSCs) from patients with CDH and preterm and term non-CDH control subjects were derived and analyzed by bulk RNA sequencing, assay for transposase accessible chromatin with sequencing, and air-liquid interface differentiation. Lung sections from fetal human CDH samples and the nitrofen rat model of CDH were subjected to histological assessment of epithelial defects. Therapeutics to restore epithelial differentiation were evaluated in human epithelial cell culture and the nitrofen rat model of CDH. Measurements and Main Results: Transcriptomic and epigenetic profiling of CDH and control BSCs reveals a proinflammatory signature that is manifested by hyperactive nuclear factor kappa B and independent of severity and hernia size. In addition, CDH BSCs exhibit defective epithelial differentiation in vitro that recapitulates epithelial phenotypes found in fetal human CDH lung samples and fetal tracheas of the nitrofen rat model of CDH. Furthermore, blockade of nuclear factor kappa B hyperactivity normalizes epithelial differentiation phenotypes of human CDH BSCs in vitro and in nitrofen rat tracheas in vivo. Conclusions: Our findings have identified an underlying proinflammatory signature and BSC differentiation defects as a potential therapeutic target for airway epithelial defects in CDH.

Structure of AMH bound to AMHR2 provides insight into a unique signaling pair in the TGF-ß family.

Anti-Müllerian hormone (AMH), or Müllerian-inhibiting substance, is a protein hormone that promotes Müllerian duct regression during male fetal sexual differentiation and regulation of folliculogenesis in women. AMH is a member of the transforming growth factor beta (TGF-ß) family, which has evolved to signal through its own dedicated type II receptor, AMH receptor type II (AMHR2). Structures of other TGF-ß family members have revealed how ligands infer specificity for their cognate receptors; however, it is unknown how AMH binds AMHR2 at the molecular level. Therefore, in this study, we solved the X-ray crystal structure of AMH bound to the extracellular domain of AMHR2 to a resolution of 2.6Å. The structure reveals that while AMH binds AMHR2 in a similar location to Activin and BMP ligand binding to their type II receptors, differences in both AMH and AMHR2 account for a highly specific interaction. Furthermore, using an AMH responsive cell-based luciferase assay, we show that a conformation in finger 1 of AMHR2 and a salt bridge formed by K534 on AMH and D81/E84 of AMHR2 are key to the AMH/AMHR2 interaction. Overall, our study highlights how AMH engages AMHR2 using a modified paradigm of receptor binding facilitated by modifications to the three-finger toxin fold of AMHR2. Furthermore, understanding these elements contributing to the specificity of binding will help in the design of agonists or antagonists or the selection of antibody therapies.

Single-cell sequencing reveals suppressive transcriptional programs regulated by MIS/AMH in neonatal ovaries.

Müllerian inhibiting substance (MIS/AMH), produced by granulosa cells of growing follicles, is an important regulator of folliculogenesis and follicle development. Treatment with exogenous MIS in mice suppresses follicle development and prevents ovulation. To investigate the mechanisms by which MIS inhibits follicle development, we performed single-cell RNA sequencing of whole neonatal ovaries treated with MIS at birth and analyzed at postnatal day 6, coinciding with the first wave of follicle growth. We identified distinct transcriptional signatures associated with MIS responses in the ovarian cell types. MIS treatment inhibited proliferation in granulosa, surface epithelial, and stromal cell types of the ovary and elicited a unique signature of quiescence in granulosa cells. In addition to decreasing the number of growing preantral follicles, we found that MIS treatment uncoupled the maturation of germ cells and granulosa cells. In conclusion, MIS suppressed neonatal follicle development by inhibiting proliferation, imposing a quiescent cell state, and preventing granulosa cell differentiation.

Systematic analysis of copy number variation associated with congenital diaphragmatic hernia.

Congenital diaphragmatic hernia (CDH), characterized by malformation of the diaphragm and hypoplasia of the lungs, is one of the most common and severe birth defects, and is associated with high morbidity and mortality rates. There is growing evidence demonstrating that genetic factors contribute to CDH, although the pathogenesis remains largely elusive. Single-nucleotide polymorphisms have been studied in recent whole-exome sequencing efforts, but larger copy number variants (CNVs) have not yet been studied on a large scale in a case control study. To capture CNVs within CDH candidate regions, we developed and tested a targeted array comparative genomic hybridization platform to identify CNVs within 140 regions in 196 patients and 987 healthy controls, and identified six significant CNVs that were either unique to patients or enriched in patients compared with controls. These CDH-associated CNVs reveal high-priority candidate genes including HLX, LHX1, and HNF1B We also discuss CNVs that are present in only one patient in the cohort but have additional evidence of pathogenicity, including extremely rare large and/or de novo CNVs. The candidate genes within these predicted disease-causing CNVs form functional networks with other known CDH genes and play putative roles in DNA binding/transcription regulation and embryonic development. These data substantiate the importance of CNVs in the etiology of CDH, identify CDH candidate genes and pathways, and highlight the importance of ongoing analysis of CNVs in the study of CDH and other structural birth defects.

De novo variants in congenital diaphragmatic hernia identify MYRF as a new syndrome and reveal genetic overlaps with other developmental disorders.

Congenital diaphragmatic hernia (CDH) is a severe birth defect that is often accompanied by other congenital anomalies. Previous exome sequencing studies for CDH have supported a role of de novo damaging variants but did not identify any recurrently mutated genes. To investigate further the genetics of CDH, we analyzed de novo coding variants in 362 proband-parent trios including 271 new trios reported in this study. We identified four unrelated individuals with damaging de novo variants in MYRF (P = 5.3x10(-8)), including one likely gene-disrupting (LGD) and three deleterious missense (D-mis) variants. Eight additional individuals with de novo LGD or missense variants were identified from our other genetic studies or from the literature. Common phenotypes of MYRF de novo variant carriers include CDH, congenital heart disease and genitourinary abnormalities, suggesting that it represents a novel syndrome. MYRF is a membrane associated transcriptional factor highly expressed in developing diaphragm and is depleted of LGD variants in the general population. All de novo missense variants aggregated in two functional protein domains. Analyzing the transcriptome of patient-derived diaphragm fibroblast cells suggest that disease associated variants abolish the transcription factor activity. Furthermore, we showed that the remaining genes with damaging variants in CDH significantly overlap with genes implicated in other developmental disorders. Gene expression patterns and patient phenotypes support pleiotropic effects of damaging variants in these genes on CDH and other developmental disorders. Finally, functional enrichment analysis implicates the disruption of regulation of gene expression, kinase activities, intra-cellular signaling, and cytoskeleton organization as pathogenic mechanisms in CDH.

AMH/MIS as a contraceptive that protects the ovarian reserve during chemotherapy.

The ovarian reserve represents the stock of quiescent primordial follicles in the ovary which is gradually depleted during a woman's reproductive lifespan, resulting in menopause. Müllerian inhibiting substance (MIS) (or anti-Müllerian hormone/AMH), which is produced by granulosa cells of growing follicles, has been proposed as a negative regulator of primordial follicle activation. Here we show that long-term parenteral administration of superphysiological doses of MIS, using either an adeno-associated virus serotype 9 (AAV9) gene therapy vector or recombinant protein, resulted in a complete arrest of folliculogenesis in mice. The ovaries of MIS-treated mice were smaller than those in controls and did not contain growing follicles but retained a normal ovarian reserve. When mice treated with AAV9/MIS were paired with male breeders, they exhibited complete and permanent contraception for their entire reproductive lifespan, disrupted vaginal cycling, and hypergonadotropic hypogonadism. However, when ovaries from AAV9-MIS-treated mice were transplanted orthotopically into normal recipient mice, or when treatment with the protein was discontinued, folliculogenesis resumed, suggesting reversibility. One of the important causes of primary ovarian insufficiency is chemotherapy-induced primordial follicle depletion, which has been proposed to be mediated in part by increased activation. To test the hypothesis that MIS could prevent chemotherapy-induced overactivation, mice were given carboplatin, doxorubicin, or cyclophosphamide and were cotreated with AAV9-MIS, recombinant MIS protein, or vehicle controls. We found significantly more primordial follicles in MIS-treated animals than in controls. Thus treatment with MIS may provide a method of contraception with the unique characteristic of blocking primordial follicle activation that could be exploited to prevent the primary ovarian insufficiency often associated with chemotherapy.

Follicular fluid anti-Müllerian hormone (AMH) concentrations and outcomes of in vitro fertilization cycles with fresh embryo transfer among women at a fertility center.

PURPOSE: To enhance the understanding of the clinical significance of anti-Müllerian hormone (AMH) in follicular fluid, we aimed to determine the variability of AMH concentrations in follicular fluid within and across IVF cycles and whether high follicular fluid AMH concentrations are associated with improved clinical IVF outcomes. METHODS: This was a retrospective cohort study of companion follicular fluid and serum samples from 162 women enrolled in the Environment and Reproductive Health (EARTH) Study between 2010 and 2016. AMH concentrations were quantified using a sandwich enzyme-linked immunosorbent assay. Spearman correlation and intra-class correlation (ICC) were calculated to assess variability of follicular fluid AMH, and generalized linear mixed models were used to evaluate the associations of FF AMH with IVF outcomes. RESULTS: The median (interquartile range, IQR) age of the 162 women was 34.0 years (32.0, 37.0). Follicular fluid AMH concentrations were highly correlated between follicles within each IVF cycle (Spearman r = 0.78 to 0.86) and across cycles for each woman (ICC 0.87 (95% CI 0.81 to 0.92)). Compared with women in the highest tertile of FF AMH (mean AMH = 2.3 ng/ml), women in the lowest tertile (mean AMH = 0.2 ng/ml) had lower serum AMH (T1 = 0.1 ng/ml vs. T3 = 0.6 ng/ml, p < 0.0001). In adjusted models, higher tertiles of follicular fluid AMH concentrations were associated with lower mean endometrial thickness and higher probability of clinical pregnancy. CONCLUSIONS: Follicular fluid AMH concentrations show little variability between pre-ovulatory follicles, and higher pre-ovulatory follicular fluid AMH may predict a higher probability of clinical pregnancy.

Towards international standardization of immunoassays for Müllerian inhibiting substance/anti-Müllerian hormone.

RESEARCH QUESTION: Is formulated and lyophilized, recombinant human Müllerian inhibiting substance, also known as anti-Müllerian hormone (AMH), suitable for the preparation of a WHO international standard to calibrate AMH immunoassays? DESIGN: The AMH content of a trial preparation, coded SS-581, was determined by five laboratories using seven immunoassay methods. Participants were requested to report the content of the preparation in terms of their method calibrators through the measurement of a minimum of five concentrations in the linear part of the dose-response curve. Participants were also asked to measure, concomitantly, a panel of six serum samples containing AMH at concentrations of 0.1-13.0 ng/ml. RESULTS: Across all assays, including two automated assays in development, the geometric mean content was 361.76 ng/ampoule with a geometric coefficient of variation (GCV%) of 39.95%. When measured by immunoassays that were commercially available at the time of the study, the mean content was 423.08 ng/ampoule, with a GCV% of 26.67%. The inter-method geometric means of five serum samples with an AMH concentration >0.3 ng/ml and measured concomitantly with dilutions of SS-581 varied with a range of GCV% of 14.90-22.35%, which may reflect the use of serum sample value transfer to calibrate current immunoassays, some of which use non-human AMH calibrators. The AMH in trial preparation SS-581 was shown to be biologically active in the Müllerian duct regression assay. CONCLUSIONS: A reference material prepared using human recombinant AMH is a promising candidate for the preparation of an international standard for AMH for immunoassays calibrated to recombinant human AMH.

AAV9 delivering a modified human Mullerian inhibiting substance as a gene therapy in patient-derived xenografts of ovarian cancer.

To improve ovarian cancer patient survival, effective treatments addressing chemoresistant recurrences are particularly needed. Mullerian inhibiting substance (MIS) has been shown to inhibit the growth of a stem-like population of ovarian cancer cells. We have recently engineered peptide modifications to human MIS [albumin leader Q425R MIS (LRMIS)] that increase production and potency in vitro and in vivo. To test this novel therapeutic peptide, serous malignant ascites from highly resistant recurrent ovarian cancer patients were isolated and amplified to create low-passage primary cell lines. Purified recombinant LRMIS protein successfully inhibited the growth of cancer spheroids in vitro in a panel of primary cell lines in four of six patients tested. Adeno-associated virus (AAV) -delivered gene therapy has undergone a clinical resurgence with a good safety profile and sustained gene expression. Therefore, AAV9 was used as a single i.p. injection to deliver LRMIS to test its efficacy in inhibiting growth of palpable tumors in patient-derived ovarian cancer xenografts from ascites (PDXa). AAV9-LRMIS monotherapy resulted in elevated and sustained blood concentrations of MIS, which significantly inhibited the growth of three of five lethal chemoresistant serous adenocarcinoma PDXa models without signs of measurable or overt toxicity. Finally, we tested the frequency of MIS type II receptor expression in a tissue microarray of serous ovarian tumors by immunohistochemistry and found that 88% of patients bear tumors that express the receptor. Taken together, these preclinical data suggest that AAV9-LRMIS provides a potentially well-tolerated and effective treatment strategy poised for testing in patients with chemoresistant serous ovarian cancer.

Genome-wide enrichment of damaging de novo variants in patients with isolated and complex congenital diaphragmatic hernia.

Congenital Diaphragmatic Hernia (CDH) is a common and often lethal birth defect characterized by diaphragmatic structural defects and pulmonary hypoplasia. CDH is isolated in 60% of newborns, but may also be part of a complex phenotype with additional anomalies. We performed whole exome sequencing (WES) on 87 individuals with isolated or complex CDH and on their unaffected parents, to assess the contribution of de novo mutations in the etiology of diaphragmatic and pulmonary defects and to identify new candidate genes. A combined analysis with 39 additional trios with complex CDH, previously published, revealed a significant genome-wide burden of de novo variants compared to background mutation rate and 900 control trios. We identified an increased burden of likely gene-disrupting (LGD, i.e. nonsense, frameshift, and canonical splice site) and predicted deleterious missense (D-mis) variants in complex and isolated CDH patients. Overall, an excess of predicted damaging de novo LGD and D-mis variants relative to the expected frequency contributed to 21% of complex cases and 12% of isolated CDH cases. The burden of de novo variants was higher in genes expressed in the developing mouse diaphragm and heart. Some overlap with genes responsible for congenital heart defects and neurodevelopmental disorders was observed in CDH patients within our cohorts. We propose that de novo variants contribute significantly to the development of CDH.

Polygenic Causes of Congenital Diaphragmatic Hernia Produce Common Lung Pathologies.

Congenital diaphragmatic hernia (CDH) is one of the most common and lethal congenital anomalies, and significant evidence is available in support of a genetic contribution to its etiology, including single-gene knockout mice associated with diaphragmatic defects, rare monogenetic disorders in humans, familial aggregation, and association of CDH with chromosomal abnormalities. Structural lung defects in the form of lung hypoplasia are almost invariably seen in patients with CDH and frequently in animal models of this condition. Better understanding of the mechanisms of pulmonary defects in CDH has the potential for creating targeted therapies, particularly in postnatal stages, when therapeutics can have maximum clinical impact on the surviving cohorts. Successful treatment of CDH is dependent on the integration of human genomic and genetic data with developmental expression profiling, mouse knockouts, and gene network and pathway modeling, which have generated a large number of candidate genes and pathways for follow-up studies. In particular, defective alveolarization appears to be a common and potentially actionable phenotype in both patients and animal models.

Molecular pathogenesis of congenital diaphragmatic hernia revealed by exome sequencing, developmental data, and bioinformatics.

Congenital diaphragmatic hernia (CDH) is a common and severe birth defect. Despite its clinical significance, the genetic and developmental pathways underlying this disorder are incompletely understood. In this study, we report a catalog of variants detected by a whole exome sequencing study on 275 individuals with CDH. Predicted pathogenic variants in genes previously identified in either humans or mice with diaphragm defects are enriched in our CDH cohort compared with 120 size-matched random gene sets. This enrichment was absent in control populations. Variants in these critical genes can be found in up to 30.9% of individuals with CDH. In addition, we filtered variants by using genes derived from regions of recurrent copy number variations in CDH, expression profiles of the developing diaphragm, protein interaction networks expanded from the known CDH-causing genes, and prioritized genes with ultrarare and highly disruptive variants, in 11.3% of CDH patients. These strategies have identified several high priority genes and developmental pathways that likely contribute to the CDH phenotype. These data are valuable for comparison of candidate genes generated from whole exome sequencing of other CDH cohorts or multiplex kindreds and provide ideal candidates for further functional studies. Furthermore, we propose that these genes and pathways will enhance our understanding of the heterogeneous molecular etiology of CDH.

Type IV collagen drives alveolar epithelial-endothelial association and the morphogenetic movements of septation.

BACKGROUND: Type IV collagen is the main component of the basement membrane that gives strength to the blood-gas barrier (BGB). In mammals, the formation of a mature BGB occurs primarily after birth during alveologenesis and requires the formation of septa from the walls of the saccule. In contrast, in avians, the formation of the BGB occurs rapidly and prior to hatching. Mutation in basement membrane components results in an abnormal alveolar phenotype; however, the specific role of type IV collagen in regulating alveologenesis remains unknown. RESULTS: We have performed a microarray expression analysis in late chick lung development and found that COL4A1 and COL4A2 were among the most significantly upregulated genes during the formation of the avian BGB. Using mouse models, we discovered that mutations in murine Col4a1 and Col4a2 genes affected the balance between lung epithelial progenitors and differentiated cells. Mutations in Col4a1 derived from the vascular component were sufficient to cause defects in vascular development and the BGB. We also show that Col4a1 and Col4a2 mutants displayed disrupted myofibroblast proliferation, differentiation and migration. Lastly, we revealed that addition of type IV collagen protein induced myofibroblast proliferation and migration in monolayer culture and increased the formation of mesenchymal-epithelial septal-like structures in co-culture. CONCLUSIONS: Our study showed that type IV collagen and, therefore the basement membrane, play fundamental roles in coordinating alveolar morphogenesis. In addition to its role in the formation of epithelium and vasculature, type IV collagen appears to be key for alveolar myofibroblast development by inducing their proliferation, differentiation and migration throughout the developing septum.

De novo frameshift mutation in COUP-TFII (NR2F2) in human congenital diaphragmatic hernia.

COUP-TFII (NR2F2) is mapped to the 15q26 deletion hotspot associated with the common and highly morbid congenital diaphragmatic hernia (CDH). Conditional homozygous deletions of COUP-TFII in mice result in diaphragmatic defects analogous to the human Bochdalek-type hernia phenotype. Despite evidence from animal models however, mutations in the coding sequence of COUP-TFII have not been reported in patients, prompting the speculation that additional coding or non-coding sequences in the 15q26 locus are necessary for diaphragmatic hernias to develop. In this report, we describe a case of a patient with a heterozygous de novo COUP-TFII frameshift mutation, presenting with CDH and an atrial septal defect. The p.Pro33AlafsTer77 mutation specifically disrupts protein isoform 1 which contains the DNA binding domain. In addition, we review other COUP-TFII sequence variations and deletions that have been described in cases of CDH. We conclude that COUP-TFII mutations can cause diaphragmatic hernias, and should be included in the differential diagnosis of CDH patients, particularly those with comorbid congenital heart defects. © 2016 Wiley Periodicals, Inc.

Mutations in LRP2, which encodes the multiligand receptor megalin, cause Donnai-Barrow and facio-oculo-acoustico-renal syndromes.

Donnai-Barrow syndrome is associated with agenesis of the corpus callosum, congenital diaphragmatic hernia, facial dysmorphology, ocular anomalies, sensorineural hearing loss and developmental delay. By studying multiplex families, we mapped this disorder to chromosome 2q23.3-31.1 and identified LRP2 mutations in six families with Donnai-Barrow syndrome and one family with facio-oculo-acoustico-renal syndrome. LRP2 encodes megalin, a multiligand uptake receptor that regulates levels of diverse circulating compounds. This work implicates a pathway with potential pharmacological therapeutic targets.

Induction of WNT inhibitory factor 1 expression by Müllerian inhibiting substance/antiMullerian hormone in the Müllerian duct mesenchyme is linked to Müllerian duct regression.

A key event during mammalian sexual development is regression of the Müllerian ducts (MDs) in the bipotential urogenital ridges (UGRs) of fetal males, which is caused by the expression of Müllerian inhibiting substance (MIS) in the Sertoli cells of the differentiating testes. The paracrine signaling mechanisms involved in MD regression are not completely understood, particularly since the receptor for MIS, MISR2, is expressed in the mesenchyme surrounding the MD, but regression occurs in both the epithelium and mesenchyme. Microarray analysis comparing MIS signaling competent and Misr2 knockout embryonic UGRs was performed to identify secreted factors that might be important for MIS-mediated regression of the MD. A seven-fold increase in the expression of Wif1, an inhibitor of WNT/ß-catenin signaling, was observed in the Misr2-expressing UGRs. Whole mount in situ hybridization of Wif1 revealed a spatial and temporal pattern of expression consistent with Misr2 during the window of MD regression in the mesenchyme surrounding the MD epithelium that was absent in both female UGRs and UGRs knocked out for Misr2. Knockdown of Wif1 expression in male UGRs by Wif1-specific siRNAs beginning on embryonic day 13.5 resulted in MD retention in an organ culture assay, and exposure of female UGRs to added recombinant human MIS induced Wif1 expression in the MD mesenchyme. Knockdown of Wif1 led to increased expression of ß-catenin and its downstream targets TCF1/LEF1 in the MD mesenchyme and to decreased apoptosis, resulting in partial to complete retention of the MD. These results strongly suggest that WIF1 secretion by the MD mesenchyme plays a role in MD regression in fetal males.