Mutations In BMP4 Research Articles

Mutations in LRP5 and BMP4 are associated with mesiodens, tooth agenesis, root malformation, and oral exostoses.

WNT/β-catenin and BMP signaling pathways play important roles in the process of tooth development. Dysregulation of WNT/β-catenin and BMP signaling is implicated in a number of human malformations, including dental anomalies. Whole exome and Sanger sequencing identified seven patients with LRP5 mutations (p.Asn1121Asp, p.Asp856Asn, p.Val1433Met, and p.Val1245Met) and six patients with BMP4 mutations (p.Asn150Lys, p.Gly168Arg, p.Arg269Gln, and p.Ala42Glu). All patients were affected with isolated dental anomalies (dental anomalies with no other structural defects), including mesiodens, tooth agenesis, unseparated roots, narrow roots, shortened and tapered roots, and taurodontism. Five patients with LRP5 and one with BMP4 mutations had oral exostoses. Protein models of LRP5 mutations indicate the possible functional effects of the mutations. Here we report for the first time that mutations in LRP5 are associated with dental anomalies. LRP5 appears to be the first gene related to pathogenesis of mesiodens. We also show for the first time that in addition to tooth agenesis, mutations in BMP4 are also implicated in root maldevelopment and torus mandibularis. Sharing of the phenotypes of the patients with LRP5 and BMP4 mutations, which include root maldevelopment, tooth agenesis, and torus mandibularis, implicates cross talks between the WNT/β-catenin and BMP signaling pathways, especially during root development.

BMP7 functions predominantly as a heterodimer with BMP2 or BMP4 during mammalian embryogenesis.

BMP7/BMP2 or BMP7/BMP4 heterodimers are more active than homodimers in vitro, but it is not known whether these heterodimers signal in vivo. To test this, we generated knock in mice carrying a mutation (Bmp7R-GFlag) that prevents proteolytic activation of the dimerized BMP7 precursor protein. This mutation eliminates the function of BMP7 homodimers and all other BMPs that normally heterodimerize with BMP7. While Bmp7 null homozygotes are live born, Bmp7R-GFlag homozygotes are embryonic lethal and have broadly reduced BMP activity. Furthermore, compound heterozygotes carrying the Bmp7R-G allele together with a null allele of Bmp2 or Bmp4 die during embryogenesis with defects in ventral body wall closure and/or the heart. Co-immunoprecipitation assays confirm that endogenous BMP4/7 heterodimers exist. Thus, BMP7 functions predominantly as a heterodimer with BMP2 or BMP4 during mammalian development, which may explain why mutations in either Bmp4 or Bmp7 lead to a similar spectrum of congenital defects in humans.

Ciliary margin-derived BMP4 does not have a major role in ocular development.

Heterozygous Bmp4 mutations in humans and mice cause severe ocular anterior segment dysgenesis (ASD). Abnormalities include pupil displacement, corneal opacity, iridocorneal adhesions, and variable intraocular pressure, as well as some retinal and vascular defects. It is presently not known what source of BMP4 is responsible for these defects, as BMP4 is expressed in several developing ocular and surrounding tissues. In particular, BMP4 is expressed in the ciliary margins of the optic cup which give rise to anterior segment structures such as the ciliary body and iris, making it a good candidate for the required source of BMP4 for anterior segment development. Here, we test whether ciliary margin-derived BMP4 is required for ocular development using two different conditional knockout approaches. In addition, we compared the conditional deletion phenotypes with Bmp4 heterozygous null mice. Morphological, molecular, and functional assays were performed on adult mutant mice, including histology, immunohistochemistry, in vivo imaging, and intraocular pressure measurements. Surprisingly, in contrast to Bmp4 heterozygous mutants, our analyses revealed that the anterior and posterior segments of Bmp4 conditional knockouts developed normally. These results indicate that ciliary margin-derived BMP4 does not have a major role in ocular development, although subtle alterations could not be ruled out. Furthermore, we demonstrated that the anterior and posterior phenotypes observed in Bmp4 heterozygous animals showed a strong propensity to co-occur, suggesting a common, non-cell autonomous source for these defects.

Next-generation sequencing reveals genetic landscape in 46, XY disorders of sexual development patients with variable phenotypes

Disorders of sexual development (DSD) are rare congenital conditions in which chromosomal, gonadal, or anatomical sex is atypical. Currently, less than 20% of patients receive an accurate genetic diagnosis. Targeted next-generation sequencing, consisting of 33 candidate genes and 47 genes involved in sexual differentiation and development, was performed on 70 46, XY DSD patients. Functional assays were performed to evaluate the expression and transcriptional activity of one reported and nine novel mutations of NR5A1. In total, 113 mutations, including 86 novel and 27 reported sites in 40 genes, were identified in 52 patients. Among them, 37 mutations from 19 genes were first identified in 46, XY DSD patients, including EGF, LHX9, and CST9. Nine patients displayed biallelic mutations, 12 had mutations in sex chromosome genes and 14 had monoallelic mutations in NR5A1, BMP4, and WT1. Higher frequency mutations were identified in AR, SRD5A2, and NR5A1. Six missense, one frameshift, and one three-nucleotide deletion mutations of NR5A1 were shown to impair the transactivation ability with an altered nuclear aggregation of p.T29K and p.N44del variants. Multiple genetic mutations were identified in 33 of the 70 patients. The targeted sequencing panel provides an efficient method for the etiological diagnosis of 46, XY DSD patients and expands the candidate genes and inherited patterns.

A mouse model of aniridia reveals the in vivo downstream targets of Pax6 driving iris and ciliary body development in the eye

The Pax6 transcription factor is essential for development of the brain, eye, olfactory and endocrine systems. Haploinsufficiency of PAX6 in humans and mice causes the congenital condition aniridia, with defects in each of these organs and systems. Identification of the PAX6 transcription networks driving normal development is therefore critical in understanding the pathophysiology observed with loss-of-function defects. Here we have focused on identification of the downstream targets for Pax6 in the developing iris and ciliary body, where we used laser capture microdissection in mouse eyes from E12.5–E16.5, followed by chromatin immunoprecipitation, promoter-reporter assays and immunohistochemistry. We identified 6 differentially expressed genes between wildtype and Pax6 heterozygous mouse tissues and demonstrated that Bmp4, Tgfβ2, and Foxc1 were direct downstream targets of Pax6 in developing iris/ciliary body. These results improve our understanding of how mutations in Bmp4, Tgfβ2, and Foxc1 result in phenocopies of the aniridic eye disease and provide possible targets for therapeutic intervention.

Cardiac responses to 24 hrs hyperoxia in Bmp2 and Bmp4 heterozygous mice

Background: Hyperoxia or clinical oxygen (O2) therapy is known to result in increased oxidative burden. Therefore, understanding susceptibility to hyperoxia exposure is clinically important. Bone morphogenetic proteins (BMPs) 2 and 4 are involved in cardiac development and may influence responses to hyperoxia.Methods. Bmp2+/−. Bmp4+/− and wild-type mice were exposed to hyperoxia (100% O2) for 24 hrs. Electrocardiograms (ECG) were recorded before and during exposure by radio-telemetry.Results: At baseline, a significantly higher low frequency (LF) and total power (TP) heart rate variability (HRV) were found in Bmp2+/− mice only (p < 0.05). Twenty-four hours hyperoxia-induced strain-independent reductions in heart rate, QTcB and ST-interval and increases in QRS, LF HRV and standard deviation of RR-intervals were observed. In Bmp4+/− mice only, increased PR-interval (PR-I) (24 hrs), P-wave duration (P-d; 18 and 21–24 hrs), PR-I minus P-d (PR – Pd; 24 hrs) and root of the mean squared differences of successive RR-intervals (24 hrs) were found during hyperoxia (p < 0.05).Discussion: Elevated baseline LF and TP HRV in Bmp2+/− mice suggests an altered autonomic nervous system regulation of cardiac function in these mice. However, this was not related to strain specific differences in responses to 24 hrs hyperoxia. During hyperoxia, Bmp4+/− mice were the most susceptible in terms of atrioventricular conduction changes and risk of atrial fibrillation, which may have important implications for patients treated with O2 who also harbor Bmp4 mutations. This study demonstrates significant ECG and HRV responses to 24 hrs hyperoxia in mice, which highlights the need to further work on the genetic mechanisms associated with cardiac susceptibility to hyperoxia.

Heart rate, PR‐interval and QT‐interval responses to 24hrs hyperoxia in Bmp2 and Bmp4 heterozygous mice

BackgroundProlonged hyperoxia (96hrs) leads to adverse murine cardiac responses, but clinical therapy with high O2 levels is often short‐term. Therefore, understanding susceptibility to short‐term hyperoxia exposure is clinically important. Bone morphogenetic proteins (BMP) 2 and 4 are important in cardiac development and may influence cardiac responses to hyperoxia. We investigated cardiac responses to 24hrs hyperoxia in Bmp2+/− and Bmp4+/− mice.MethodsBmp2+/−, Bmp4+/− and WT littermates were exposed to 24hrs hyperoxia (100% O2). ECG was recorded before and during exposure.ResultsNo differences in baseline HR, QTcB, QRS, ST‐I, PR‐I, P‐wave duration (P‐d) or PR‐I/P‐d were found (P &gt;;0.05). After ~18hrs hyperoxia, significant decreases in HR and increases in PR‐I and P‐d were found in Bmp4+/− mice only. Also, there were reductions in QTcB in the WT, but not in Bmp2+/− or Bmp4+/− mice after 17hrs hyperoxia (P &lt;0.05).DiscussionResults suggest that developmental effects of Bmp2 or Bmp4 disruption did not affect basal cardiac function or were not detectable by ECG. During hyperoxia, Bmp4+/− mice were susceptible in terms of HR and atrioventricular conduction responses, which may have important implications for patients treated with O2 who also harbor Bmp4 mutations. Conversely, QTcB in Bmp2+/− or Bmp4+/− mice was not affected by hyperoxia, unlike WT mice, suggesting a protective effect in these genotypes.

Double homozygous missense mutations in DACH1 and BMP4 in a patient with bilateral cystic renal dysplasia

Renal hypodysplasia (RHD) is characterized by small and/or disorganized kidneys following abnormal organogenesis. Mutations in several genes have been identified recently to be associated with RHD in humans, including BMP4, a member of the transforming growth factor (TGF)-β family of growth factors. DACH1 has been proposed as a candidate gene for RHD because of its involvement in the EYA-SIX-DACH network of renal developmental genes. Here, we present a patient with renal dysplasia carrying homozygous missense mutations in both BMP4 (p.N150K) and DACH1 (p.R684C). The genotype-phenotype correlation in the family hints at an oligogenic mode of inheritance of the disease in this kindred. Functional analyses of the identified DACH1 mutation in HEK293T cells demonstrated enhanced suppression of the TGF-β pathway suggesting that both mutations could act synergistically in the development of the phenotype in this patient. This finding provides a model for RHD as an oligo-/polygenic disorder and supports a role for DACH1 in the development of RHD in humans.

Cleft Lip in Oculodentodigital Dysplasia Suggests Novel Roles for Connexin43

Oculodentodigital Dysplasia (ODDD) is a rare syndrome involving anomalies in eye, tooth, and digit formation, caused by mutations in CX43/GJA1. In addition to classic dental features, ODDD includes oral and craniofacial accessory symptoms such as characteristic facial appearance and cleft palate. However, there have been no reports of ODDD accompanied by cleft lip. Herein we report, for the first time, a male, sporadic, Asian proband presenting bilateral cleft lip. By direct sequence analysis, our proband was diagnosed as having ODDD with a heterozygous mutation, codon 142 G>A in GJA1 and CX43E48K. We excluded the possibility of pathogenic mutations in B3GALTL, BMP4, TFAP2A, PVRL1, IRF6, and MSX1. To address how CX43/GJA1 is related to cleft lip, we performed immunohistochemistry using mouse and human mid-facial tissue. CX43 expression was detected in the nasal compartment and nasal and maxillary processes at murine developmental stage E12.5. Furthermore, CX43 expression was found in the epithelial tissue inside the human subepithelial cleft lip that completes epithelial fusion. Therefore, we suggest that CX43/GJA1 is involved in lip formation. Our case report of ODDD with a bilateral cleft lip suggests that CX43/GJA1 might be a novel candidate gene for syndromic cleft lip.

Variability in expression of a familial 2.79 Mb microdeletion in chromosome14q22.1–22.2

Deletions in chromosome 14q22-23 have been associated with variable manifestations including malformations of the eye, limbs, palate, and brain, and with developmental and growth delay. Haploinsufficiency of BMP4, OTX2 and possibly SIX6 are thought to contribute to the phenotype. We present a three generation family with four individuals carrying a 2.79 Mb microdeletion 14q22.1-22.2 encompassing BMP4 but not OTX2 nor SIX6. The highly variable manifestations in this family range from multiple congenital malformations with Robin sequence, microphthalmia, postaxial polydactyly, and developmental delay in the index patient to cleft uvula, growth delay, and mild developmental delay in her sister. The adults have a normal intelligence, postaxial polydactyly, and short stature or early cataract. Genotype-phenotype correlations suggest that the severity of eye manifestations in 14q22 deletions are influenced by the size of the deletion, but the marked intrafamilial variability observed in this family, as well as in familial BMP4 or OTX2 intragenic mutations points to additional modifiers outside this region.

Aetiology of hypospadias: a systematic review of genes and environment

Hypospadias is a common congenital malformation of the male external genitalia. Most cases have an unknown aetiology, which is probably a mix of monogenic and multifactorial forms, implicating both genes and environmental factors. This review summarizes current knowledge about the aetiology of hypospadias. Pubmed was used to identify studies on hypospadias aetiology published between January 1995 and February 2011. Reference lists of the selected manuscripts were also searched to identify additional studies, including those published before 1995. The search provided 922 articles and 169 articles were selected for this review. Studies screening groups of patients with hypospadias for single gene defects found mutations in WT1, SF1, BMP4, BMP7, HOXA4, HOXB6, FGF8, FGFR2, AR, HSD3B2, SRD5A2, ATF3, MAMLD1, MID1 and BNC2. However, most investigators are convinced that single mutations do not cause the majority of isolated hypospadias cases. Indeed, associations were found with polymorphisms in FGF8, FGFR2, AR, HSD17B3, SRD5A2, ESR1, ESR2, ATF3, MAMLD1, DGKK, MID1, CYP1A1, GSTM1 and GSTT1. In addition, gene expression studies indentified CTGF, CYR61 and EGF as candidate genes. Environmental factors consistently implicated in hypospadias are low birthweight, maternal hypertension and pre-eclampsia, suggesting that placental insufficiency may play an important role in hypospadias aetiology. Exogenous endocrine-disrupting chemicals have the potential to induce hypospadias but it is unclear whether human exposure is high enough to exert this effect. Other environmental factors have also been associated with hypospadias but, for most, the results are inconsistent. Although a number of contributors to the aetiology of hypospadias have been identified, the majority of risk factors remain unknown.

BMP4 loss-of-function mutations in developmental eye disorders including SHORT syndrome

BMP4 loss-of-function mutations and deletions have been shown to be associated with ocular, digital, and brain anomalies, but due to the paucity of these reports, the full phenotypic spectrum of human BMP4 mutations is not clear. We screened 133 patients with a variety of ocular disorders for BMP4 coding region mutations or genomic deletions. BMP4 deletions were detected in two patients: a patient affected with SHORT syndrome and a patient with anterior segment anomalies along with craniofacial dysmorphism and cognitive impairment. In addition to this, three intragenic BMP4 mutations were identified. A patient with anophthalmia, microphthalmia with sclerocornea, right-sided diaphragmatic hernia, and hydrocephalus was found to have a c.592C>T (p.R198X) nonsense mutation in BMP4. A frameshift mutation, c.171dupC (p.E58RfsX17), was identified in two half-siblings with anophthalmia/microphthalmia, discordant developmental delay/postaxial polydactyly, and poor growth as well as their unaffected mother; one affected sibling carried an additional BMP4 mutation in the second allele, c.362A>G (p.H121R). This is the first report indicating a role for BMP4 in SHORT syndrome, Axenfeld–Rieger malformation, growth delay, macrocephaly, and diaphragmatic hernia. These results significantly expand the number of reported loss-of-function mutations, further support the critical role of BMP4 in ocular development, and provide additional evidence of variable expression/non-penetrance of BMP4 mutations.

Functional analysis of BMP4 mutations identified in pediatric CAKUT patients

Human congenital anomalies of the kidney and urinary tract (CAKUT) represent the major causes of chronic renal failure (CRF) in children. This set of disorders comprises renal agenesis, hypoplasia, dysplastic or double kidneys, and/or malformations of the ureter. It has recently been shown that mutations in several genes, among them BMP4, are associated with hereditary renal developmental diseases. In BMP4, we formerly identified three missense mutations (S91C, T116S, N150K) in five pediatric CAKUT patients. These BMP4 mutations were subsequently studied in a cellular expression system, and here we present functional data demonstrating a lower level of messenger RNA (mRNA) abundance in Bmp4 mutants that indicates a possible negative feedback of the mutants on their own mRNA expression and/or stability. Furthermore, we describe the formation of alternative protein complexes induced by the S91C-BMP4 mutation, which results in perinuclear endoplasmic reticulum (ER) accumulation and enhanced lysosomal degradation of Bmp4. This work further supports the role of mutations in BMP4 for abnormalities of human kidney development.

Reduced TFAP2A function causes variable optic fissure closure and retinal defects and sensitizes eye development to mutations in other morphogenetic regulators.

Mutations in the transcription factor encoding TFAP2A gene underlie branchio-oculo-facial syndrome (BOFS), a rare dominant disorder characterized by distinctive craniofacial, ocular, ectodermal and renal anomalies. To elucidate the range of ocular phenotypes caused by mutations in TFAP2A, we took three approaches. First, we screened a cohort of 37 highly selected individuals with severe ocular anomalies plus variable defects associated with BOFS for mutations or deletions in TFAP2A. We identified one individual with a de novo TFAP2A four amino acid deletion, a second individual with two non-synonymous variations in an alternative splice isoform TFAP2A2, and a sibling-pair with a paternally inherited whole gene deletion with variable phenotypic expression. Second, we determined that TFAP2A is expressed in the lens, neural retina, nasal process, and epithelial lining of the oral cavity and palatal shelves of human and mouse embryos--sites consistent with the phenotype observed in patients with BOFS. Third, we used zebrafish to examine how partial abrogation of the fish ortholog of TFAP2A affects the penetrance and expressivity of ocular phenotypes due to mutations in genes encoding bmp4 or tcf7l1a. In both cases, we observed synthetic, enhanced ocular phenotypes including coloboma and anophthalmia when tfap2a is knocked down in embryos with bmp4 or tcf7l1a mutations. These results reveal that mutations in TFAP2A are associated with a wide range of eye phenotypes and that hypomorphic tfap2a mutations can increase the risk of developmental defects arising from mutations at other loci.

Mutations in BMP4 Are Associated with Subepithelial, Microform, and Overt Cleft Lip

Cleft lip with or without cleft palate (CL/P) is a complex trait with evidence that the clinical spectrum includes both microform and subepithelial lip defects. We identified missense and nonsense mutations in the BMP4 gene in 1 of 30 cases of microform clefts, 2 of 87 cases with subepithelial defects in the orbicularis oris muscle (OOM), 5 of 968 cases of overt CL/P, and 0 of 529 controls. These results provide confirmation that microforms and subepithelial OOM defects are part of the spectrum of CL/P and should be considered during clinical evaluation of families with clefts. Furthermore, we suggest a role for BMP4 in wound healing.

SIX2 and BMP4 Mutations Associate With Anomalous Kidney Development

Renal hypodysplasia (RHD) is characterized by reduced kidney size and/or maldevelopment of the renal tissue following abnormal organogenesis. Mutations in renal developmental genes have been identified in a subset of affected individuals. Here, we report the first mutations in BMP4 and SIX2 identified in patients with RHD. We detected 3 BMP4 mutations in 5 RHD patients, and 3 SIX2 mutations in 5 different RHD patients. Overexpression assays in zebrafish demonstrated that these mutations affect the function of Bmp4 and Six2 in vivo. Overexpression of zebrafish six2.1 and bmp4 resulted in dorsalization and ventralization, respectively, suggesting opposing roles in mesendoderm formation. When mutant constructs containing the identified human mutations were overexpressed instead, these effects were attenuated. Morpholino knockdown of bmp4 and six2.1 affected glomerulogenesis, suggesting specific roles for these genes in the formation of the pronephros. In summary, these studies implicate conserved roles for Six2 and Bmp4 in the development of the renal system. Defects in these proteins could affect kidney development at multiple stages, leading to the congenital anomalies observed in patients with RHD.

Mutations in GATA4, NKX2.5, CRELD1, and BMP4 are infrequently found in patients with congenital cardiac septal defects

American Journal of Medical Genetics Part AVolume 146A, Issue 2 p. 251-253 Research Letter Mutations in GATA4, NKX2.5, CRELD1, and BMP4 are infrequently found in patients with congenital cardiac septal defects†‡ Maximilian G. Posch, Maximilian G. Posch Charité—Universitätsmedizin Berlin, Cardiology at Campus Buch and Helios-Klinikum Berlin-Buch and Max-Delbrück Center for Molecular Medicine, Berlin, GermanySearch for more papers by this authorAndreas Perrot, Andreas Perrot Charité—Universitätsmedizin Berlin, Cardiology at Campus Buch and Helios-Klinikum Berlin-Buch and Max-Delbrück Center for Molecular Medicine, Berlin, GermanySearch for more papers by this authorKatharina Schmitt, Katharina Schmitt German Heart Institute Berlin, Department of Congenital Heart Disease and Pediatric Cardiology, Berlin, GermanySearch for more papers by this authorSebastian Mittelhaus, Sebastian Mittelhaus Charité—Universitätsmedizin Berlin, Biomedical Research Center, Berlin, GermanySearch for more papers by this authorEva-Maria Esenwein, Eva-Maria Esenwein German Heart Institute Berlin, Department of Congenital Heart Disease and Pediatric Cardiology, Berlin, GermanySearch for more papers by this authorBrigitte Stiller, Brigitte Stiller German Heart Institute Berlin, Department of Congenital Heart Disease and Pediatric Cardiology, Berlin, GermanySearch for more papers by this authorChristian Geier, Christian Geier Charité—Universitätsmedizin Berlin, Cardiology at Campus Buch and Helios-Klinikum Berlin-Buch and Max-Delbrück Center for Molecular Medicine, Berlin, Germany Charité—Universitätsmedizin Berlin, Cardiology at Campus Virchow Klinikum, Berlin, GermanySearch for more papers by this authorRainer Dietz, Rainer Dietz Charité—Universitätsmedizin Berlin, Cardiology at Campus Buch and Helios-Klinikum Berlin-Buch and Max-Delbrück Center for Molecular Medicine, Berlin, Germany Charité—Universitätsmedizin Berlin, Cardiology at Campus Virchow Klinikum, Berlin, GermanySearch for more papers by this authorReinhard Geßner, Reinhard Geßner Charité—Universitätsmedizin Berlin, Biomedical Research Center, Berlin, GermanySearch for more papers by this authorCemil Özcelik, Corresponding Author Cemil Özcelik oezcelik@mdc-berlin.de Charité—Universitätsmedizin Berlin, Cardiology at Campus Buch and Helios-Klinikum Berlin-Buch and Max-Delbrück Center for Molecular Medicine, Berlin, GermanyCharité Campus Buch, FVK (Haus 129) CardioGenetic Laboratory, Wiltbergstrasse 50, 13125 Berlin, Germany.Search for more papers by this authorFelix Berger, Felix Berger German Heart Institute Berlin, Department of Congenital Heart Disease and Pediatric Cardiology, Berlin, Germany Charité—Universitätsmedizin Berlin, Otto-Heubner Centrum at Campus Virchow Klinikum, Berlin, GermanySearch for more papers by this author Maximilian G. Posch, Maximilian G. Posch Charité—Universitätsmedizin Berlin, Cardiology at Campus Buch and Helios-Klinikum Berlin-Buch and Max-Delbrück Center for Molecular Medicine, Berlin, GermanySearch for more papers by this authorAndreas Perrot, Andreas Perrot Charité—Universitätsmedizin Berlin, Cardiology at Campus Buch and Helios-Klinikum Berlin-Buch and Max-Delbrück Center for Molecular Medicine, Berlin, GermanySearch for more papers by this authorKatharina Schmitt, Katharina Schmitt German Heart Institute Berlin, Department of Congenital Heart Disease and Pediatric Cardiology, Berlin, GermanySearch for more papers by this authorSebastian Mittelhaus, Sebastian Mittelhaus Charité—Universitätsmedizin Berlin, Biomedical Research Center, Berlin, GermanySearch for more papers by this authorEva-Maria Esenwein, Eva-Maria Esenwein German Heart Institute Berlin, Department of Congenital Heart Disease and Pediatric Cardiology, Berlin, GermanySearch for more papers by this authorBrigitte Stiller, Brigitte Stiller German Heart Institute Berlin, Department of Congenital Heart Disease and Pediatric Cardiology, Berlin, GermanySearch for more papers by this authorChristian Geier, Christian Geier Charité—Universitätsmedizin Berlin, Cardiology at Campus Buch and Helios-Klinikum Berlin-Buch and Max-Delbrück Center for Molecular Medicine, Berlin, Germany Charité—Universitätsmedizin Berlin, Cardiology at Campus Virchow Klinikum, Berlin, GermanySearch for more papers by this authorRainer Dietz, Rainer Dietz Charité—Universitätsmedizin Berlin, Cardiology at Campus Buch and Helios-Klinikum Berlin-Buch and Max-Delbrück Center for Molecular Medicine, Berlin, Germany Charité—Universitätsmedizin Berlin, Cardiology at Campus Virchow Klinikum, Berlin, GermanySearch for more papers by this authorReinhard Geßner, Reinhard Geßner Charité—Universitätsmedizin Berlin, Biomedical Research Center, Berlin, GermanySearch for more papers by this authorCemil Özcelik, Corresponding Author Cemil Özcelik oezcelik@mdc-berlin.de Charité—Universitätsmedizin Berlin, Cardiology at Campus Buch and Helios-Klinikum Berlin-Buch and Max-Delbrück Center for Molecular Medicine, Berlin, GermanyCharité Campus Buch, FVK (Haus 129) CardioGenetic Laboratory, Wiltbergstrasse 50, 13125 Berlin, Germany.Search for more papers by this authorFelix Berger, Felix Berger German Heart Institute Berlin, Department of Congenital Heart Disease and Pediatric Cardiology, Berlin, Germany Charité—Universitätsmedizin Berlin, Otto-Heubner Centrum at Campus Virchow Klinikum, Berlin, GermanySearch for more papers by this author First published: 12 December 2007 https://doi.org/10.1002/ajmg.a.32042Citations: 66 † A. Perrot, K. Schmitt, S. Mittelhaus, C. Özcelik, and F. Berger contributed equally to this work. ‡ How to cite this article: Posch MG, Perrot A, Schmitt K, Mittelhaus S, Esenwein E-M, Stiller B, Geier C, Dietz R, Geßner R, Özcelik C, Berger F. 2007. Mutations in GATA4, NKX2.5, CRELD1, and BMP4 are infrequently found in patients with congenital cardiac septal defects. Am J Med Genet Part A 146A:251–253. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. 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Potential roles for BMP and Pax genes in the development of iris smooth muscle

The embryonic optic cup generates four types of tissue: neural retina, pigmented epithelium, ciliary epithelium, and iris smooth muscle. Remarkably little attention has focused on the development of the iris smooth muscle since Lewis ([1903] J. Am. Anat. 2:405-416) described its origins from the anterior rim of the optic cup neuroepithelium. As an initial step toward understanding iris smooth muscle development, I first determined the spatial and temporal pattern of the development of the iris smooth muscle in the chick by using the HNK1 antibody, which labels developing iris smooth muscle. HNK1 labeling shows that iris smooth muscle development is correlated in time and space with the development of the ciliary epithelial folds. Second, because neural crest is the only other neural tissue that has been shown to generate smooth muscle (Le Lievre and Le Douarin [1975] J. Embryo. Exp. Morphol. 34:125-154), I sought to determine whether iris smooth muscle development shares similarities with neural crest development. Two members of the BMP superfamily, BMP4 and BMP7, which may regulate neural crest development, are highly expressed by cells at the site of iris smooth muscle generation. Third, because humans and mice that are heterozygous for Pax6 mutations have no irides (Hill et al. [1991] Nature 354:522-525; Hanson et al. [1994] Nat. Genet. 6:168-173), I determined the expression of Pax6. I also examined the expression of Pax3 in the developing anterior optic cup. The developing iris smooth muscle coexpresses Pax6 and Pax3. I suggest that some of the eye defects caused by mutations in Pax6, BMP4, and BMP7 may be due to abnormal iris smooth muscle.

Evaluation of BMP4 and its specific inhibitor NOG as candidates in human neural tube defects (NTDs).

Neural tube defects (NTD) are among the most common congenital malformations in humans. The current view is that there are no major genes causing NTDs, but combinations of sequence variants in different genes have additive effects on determining the malformation. Therefore it is important to identify such sequence variants to get a better understanding of NTD pathogenesis. Studies on animal models have shown that BMP4 and NOG are involved in the patterning of the neural tube. We therefore performed a single-strand conformation analysis (SSCA) mutation screen for both genes in 179 spina bifida aperta (SBA) patients. Our SSCA screen revealed four missense mutations in BMP4 and one in NOG. It is likely that these mutations have acted together with other gene variants in independently segregating loci as susceptibility factors in these SBA cases. In addition, a case-control association study provides evidence for a genotype disequilibrium of BMP4 polymorphism 455T-->C (V152A) in exon 5. The frequency of the heterozygous 455TC genotype is lower in cases than in controls (nominal P=0.017), although allele frequencies are similar in both groups. A possible explanation for this finding might be that BMP4 455TC heterozygosity at this site is a protective factor in the normal population, although this hypothesis cannot be proven to date.

Requirement of Bmp8b for the generation of primordial germ cells in the mouse.

In the mouse embryo, the generation of primordial germ cells (PGCs) from the epiblast requires a bone morphogenetic protein-4 (BMP4) signal from the adjacent extraembryonic ectoderm. In this study, we report that Bmp8b, a member of the Gbb-60A class of the BMP superfamily, is expressed in the extraembryonic ectoderm in pregastrula and gastrula stage mouse embryos and is required for PGC generation. A mutation in Bmp8b on a mixed genetic background results in the absence of PGCs in 43% null mutant embryos and severe reduction in PGC number in the remainder. The heterozygotes are unaffected. On a largely C57BL/6 background, Bmp8b null mutants completely lack PGCs, and Bmp8b heterozygotes have a reduced number of PGCs. In addition, Bmp8b homozygous null embryos on both genetic backgrounds have a short allantois, and this organ is missing in some more severe mutants. Since Bmp4 heterozygote embryos have reduced numbers of PGCs, we used a genetic approach to generate double-mutant embryos to study interactions of Bmp8b and Bmp4. Embryos that are double heterozygotes for the Bmp8b and Bmp4 mutations have similar defects in PGC number as Bmp4 heterozygotes, indicating that the effects of the two BMPs are not additive. These findings suggest that BMP4 and BMP8B function as heterodimers and homodimers in PGC specification in the mouse.