A comprehensive review of reported heritable noggin-associated syndromes and proposed clinical utility of one broadly inclusive diagnostic term: NOG-related-symphalangism spectrum disorder (NOG-SSD)

The NOG gene encodes noggin, a secreted polypeptide that is important for regulating multiple signaling pathways during human development, particularly in cartilage and bone. The hallmark of NOG-related syndromes is proximal symphalangism, defined by abnormal fusion of the proximal interphalangeal joints of the hands and feet. Many additional features secondary to NOG mutations are commonly but inconsistently observed, including a characteristic facies with a hemicylindrical nose, congenital conductive hearing loss due to stapes fixation, and hyperopia. The variable clinical presentations led to the designation of five different autosomal dominant syndromes, all subsequently found to have resulted from NOG mutations. These include (1) proximal symphalangism; (2) multiple synostoses syndrome 1; (3) stapes ankylosis with broad thumbs and toes; (4) tarsal-carpal coalition syndrome; and (5) brachydactyly type B2. Herein, we review the phenotypic features associated with mutations in the NOG gene, demonstrating the overlapping characteristics of these syndromes. Due to the variable phenotypic spectrum within families and among families with the same mutation, we propose a unifying term, NOG-related symphalangism spectrum disorder (NOG-SSD), to aid in the clinical recognition and evaluation of all affected individuals with these phenotypes. These NOG gene variants are available in a new locus-specific database (https://NOG.lovd.nl).     

Aberrant Bmp signaling and notochord delamination in the pathogenesis of esophageal atresia.

Human foregut malformation known as esophageal atresia with tracheoesophageal fistula (EA/TEF) occurs in 1 in 4,000 live births with unknown etiology. We found that mice lacking Noggin (Nog(-/-)) displayed Type C EA/TEF, the most common form in humans, and notochordal defects strikingly similar to the adriamycin-induced rat EA/TEF model. In accord with esophageal atresia, Nog(-/-) embryos displayed reduction in the dorsal foregut endoderm, which was associated with reduced adhesion and disrupted basement membrane. However, significant apoptosis in the Nog(-/-) dorsal foregut was not observed. Instead, non-notochordal, likely endodermal, cells were found in Nog(-/-) notochord, suggesting that Noggin function is required in the notochordal plate for its proper delamination from the dorsal foregut. Notably, ablating Bmp7 function in Nog(-/-) embryos rescued EA/TEF and notochord branching defects, establishing a critical role of Noggin-mediated Bmp7 antagonism in EA/TEF pathogenesis.     

Further delineation of the GDF6 related multiple synostoses syndrome

A mutation in GDF6 was recently found to underlie a multiple synostoses syndrome. In this report, we describe the second family with GDF6‐related multiple synostoses syndrome (SYNS4), caused by a novel c.1287C>A/p.Ser429Arg mutation in GDF6. In addition to synostoses of carpal and/or tarsal bones, at least 6 of 10 affected patients in this family have been diagnosed with mild to moderate hearing loss. In four of them otosclerosis was said to be present, one patient had hearing loss due to severe stapes fixation at the age of 6 years, providing evidence that hearing loss in the GDF6‐related multiple synostoses syndrome can be present in childhood. Two others had surgery for stapes fixation at adult age. We hypothesize that, identical to the recently published GDF6‐related multiple synostoses family, the p.Ser429Arg mutation also leads to a gain of function. The previously reported c.1330T>A/pTyr444Asn mutation was located in a predicted Noggin and receptor I interacting domain and the gain of function was partly due to resistance of the mutant GDF6 to the BMP‐inhibitor Noggin. The results in our family show that mutations predicting to affect the type II receptor interface can lead to a similar phenotype and that otosclerosis presenting in childhood can be part of the GDF6‐related multiple synostoses syndrome.     

P35S mutation in the NOG gene associated with Teunissen-Cremers syndrome and features of multiple NOG joint-fusion syndromes

We report on a new family with Teunissen-Cremers syndrome. The proband presented with congenital conductive hearing loss due to stapes ankylosis and incus short process fixation with skeletal anomalies including symphalangism, broad thumbs and broad first toes, syndactyly, brachydactyly, contractures of the elbows and knees, hyperopia and lens opacities. This constellation of symptoms is compatible with the diagnosis of one of the joint-fusion syndromes namely the Teunissen-Cremers syndrome (TCS), which was first reported in 1990. Mutations in the NOG gene which encodes the noggin protein, a bone morphogenetic protein antagonist, have been identified in TCS as well as in four other autosomal dominant disorders including proximal symphalangism (SYM1), multiple synostosis (SYNS1), Tarsal-Carpal coalition syndrome and brachydactyly type B (BDB). Interestingly, we found that the mutation P35S described in this family has already been reported in patients affected with SYM1 as well as with BDB syndromes.     

Clinical and genetic analysis of two Tunisian otosclerosis families

Otosclerosis is caused by an abnormal bone homeostasis of the otic capsule resulting in a conductive hearing loss when the free motion of the stapes is compromised. An additional sensorineural hearing loss arises in some patients, most likely due to otosclerotic foci that invade the cochlear endosteum. Otosclerosis is a very common hearing impairment among Caucasians with a prevalence of about 0.3-0.4% among white adults. In the majority of cases, otosclerosis can be considered as a complex disease, caused by both genetic as environmental factors, but autosomal dominant forms of otosclerosis exist. However, families large enough for genetic analysis are very rare and often show reduced penetrance. To date five loci have been reported, but none of the genes have been cloned yet. In this study, we analyzed two new autosomal dominant otosclerosis families from Tunisia, and genotyped them with microsatellite markers for the known loci, the collagen genes COL1A1 and COL1A2, and NOG gene. In the family LK, linkage to all known loci was excluded. However, the family LS shows suggestive linkage to the OTSC3 region on chromosome 6p21.3-p22.3. This result points out that, besides the five reported loci, there must be at least one additional locus for autosomal dominant otosclerosis.     

Noggin null allele mice exhibit a microform of holoprosencephaly

Holoprosencephaly (HPE) is a heterogeneous craniofacial and neural developmental anomaly characterized in its most severe form by the failure of the forebrain to divide. In humans, HPE is associated with disruption of Sonic hedgehog and Nodal signaling pathways, but the role of other signaling pathways has not yet been determined. In this study, we analyzed mice which, due to the lack of the Bmp antagonist Noggin, exhibit elevated Bmp signaling. Noggin(-/-) mice exhibited a solitary median maxillary incisor that developed from a single dental placode, early midfacial narrowing as well as abnormalities in the developing hyoid bone, pituitary gland and vomeronasal organ. In Noggin(-/-) mice, the expression domains of Shh, as well as the Shh target genes Ptch1 and Gli1, were reduced in the frontonasal region at key stages of early facial development. Using E10.5 facial cultures, we show that excessive BMP4 results in reduced Fgf8 and Ptch1 expression. These data suggest that increased Bmp signaling in Noggin(-/-) mice results in downregulation of the hedgehog pathway at a critical stage when the midline craniofacial structures are developing, which leads to a phenotype consistent with a microform of HPE.     

Possible autosomal recessive inheritance of progressive hearing loss with stapes fixation.

Four sibs with progressive, bilateral conductive hearing loss are presented. Symmetrical hearing loss averaging 30-60 dB (0.125-8 kHz) became apparent between 8 and 24 years of age. Tympanotomy showed a fixed stapes either through ossified stapedius tendon or through ossified stapedius tendon or through a bony bridge from the stapes to the pyramidal eminence in all patients. After surgical removal of the bony tendon hearing was normal. Both parents, four other sibs, and all grandparents had normal hearing. This family and a further published case suggest a possibly recessive inheritance of this form of conductive hearing loss.     

Regulation of the early expression patterns of the zebrafish Dishevelled-interacting proteins Dapper1 and Dapper2.

The Dapper/Frodo family of proteins are Dishevelled-interacting regulators of Wnt signaling. In this study, I characterize the regulation of the early expression patterns of dpr1 and dpr2. Although both dpr1 and dpr2 are expressed on the prospective dorsal side, I find that their pregastrula expression patterns have differences that have not been reported previously. Early dpr1 expression is much more dynamic than dpr2 expression. I use gain and loss of function experiments to identify dorsal organizer genes that regulate dpr1 and dpr2 expression. The dorsalizing factors beta-catenin, Bozozok (Boz), Noggin (Nog), and the mesendoderm-inducing factor Squint (Sqt) are all able to induce ectopic expression of dpr1 and dpr2. In reciprocal loss of function experiments, loss of maternal beta-catenin signaling leads to loss of early dorsal dpr1 and dpr2 expression, whereas loss of Boz and/or Nodal signaling does not. Ectopic expression of the ventralizing molecule Bmp2b leads to reduction of dpr1 and dpr2 expression. These results suggest that, in early zebrafish development, dpr1 and dpr2 are targets of beta-catenin and/or an unknown downstream effector. Their expression from 30% epiboly through shield is maintained by Nodal signaling and likely refined by the mutually antagonistic effects of Boz and bone morphogenetic protein signaling.     

Congenital stapes ankylosis, broad thumbs, and hyperopia: report of a family and refinement of a syndrome

We report on a family with conductive hearing loss due to congenital stapes ankylosis, and with hyperopia, broad thumbs, and broad first toes. Neither of the studied relatives had symphalangism, possibly distinguishing this syndrome as an entity separate from the facio-audio-symphalangism and proximal symphalangism syndromes. An alternative possibility is that this family falls within the spectrum of the facioaudio-symphalangism and proximal symphalangism syndromes. Visualization of the ossicular chain, and ophthalmologic and radiologic studies are important in the evaluation of families with congenital conductive hearing loss. A characteristic physiognomy in our patients is present; this autosomal dominant syndrome was first described by Teunissen and Cremers [1990: Laryngoscope 100:380-384].     

Bmp2 and Bmp4 accelerate alveolar bone development

Alveolar bone remodeling is a continuous process that takes place during development and in response to various physiological and pathological stimuli. However, detailed knowledge regarding the underlying mechanisms involved in alveolar bone development is still lacking. This study aims at improving our understanding of alveolar bone formation and the role of bone morphogenetic proteins (Bmps) in this process. Mice at embryonic (E) day 13.5 to postnatal (PN) day 15.5 were selected to observe the process of alveolar bone development. Alveolar bone development was found to be morphologically observable at E14.5. Molar teeth isolated from mice at PN7.5 were pretreated with Bmp2, Bmp4, Noggin, or BSA, and grafted subcutaneously into mice. The subcutaneously implanted tooth germs formed alveolar bone indicating the role of the dental follicle in alveolar bone development. Alveolar bone formation was increased after pretreatment with Bmp2 and Bmp4, but not with Noggin. Gene expression levels in dental follicle cells from murine molars were also determined by real-time RT-PCR. The expression levels of Runx2, Bsp, and Ocn were significantly higher in dental follicle cells cultured with Bmp2 or Bmp4, and significantly lower in those cultured with Noggin when compared with that of the BSA controls. Our results suggest that the dental follicle participates in alveolar bone formation and Bmp2/4 appears to accelerate alveolar bone development.     

Role of bone morphogenetic proteins on cochlear hair cell formation: Analyses of Noggin and Bmp2 mutant mice

The mammalian organ of Corti of the inner ear is a highly sophisticated sensory end organ responsible for detecting sound. Noggin is a secreted glycoprotein, which antagonizes bone morphogenetic proteins 2 and 4 (Bmp2 and Bmp4). The lack of this antagonist causes increased rows of inner and outer hair cells in the organ of Corti. In mice, Bmp2 is expressed transiently in nascent cochlear hair cells. To investigate whether Noggin normally modulates the levels of Bmp2 for hair cell formation, we deleted Bmp2 in the cochlear hair cells using two cre strains, Foxg1^cre/+ and Gfi1^cre/+. Bmp2 conditional knockout cochleae generated using these two cre strains show normal hair cells. Furthermore, Gfi1^cre/+;Bmp2^lox/? mice are viable and have largely normal hearing. The combined results of Noggin and Bmp2 mutants suggest that Noggin is likely to regulate other Bmps in the cochlea such as Bmp4. Developmental Dynamics 239:505–513, 2010. Published 2010 Wiley‐Liss, Inc.     

Mutations of the NOG gene in individuals with proximal symphalangism and multiple synostosis syndrome

Proximal symphalangism is an autosomal-dominant disorder with ankylosis of the proximal interphalangeal joints, carpal and tarsal bone fusion, and conductive deafness. These symptoms are shared by another disorder of joint morphogenesis, multiple synostoses syndrome. Recently, it was reported that both disorders were caused by heterozygous mutations of the human noggin gene (NOG). To date, seven mutations of NOG have been identified from unrelated families affected with joint morphogenesis. To characterize the molecular lesions of proximal symphalangism, we performed analyses of NOG in three Japanese individuals with proximal symphalangism. We found three novel mutations: g.551G>A (C184Y) in a sporadic case of symphalangism, g.386T>A (L129X) in a familial case of symphalangism, and a g.58delC (frameshift) in a family with multiple synostosis syndrome. Characteristic genotype-phenotype correlations have not been recognized from the mutations in the NOG gene.     

In vivo performance of the Nitinol shape-memory stapes prosthesis during hearing restoration surgery in otosclerosis: a first report

The limitations of manual prosthesis crimping in hearing restoration surgery for otosclerosis are thought to have a key role in the occurrence of incomplete postoperative elimination of conductive hearing loss and postoperative recurrences of conductive hearing loss. To eliminate manual crimping, the self-crimping, shape-memory alloy Nitinol stapes piston was introduced in nine otosclerosis patients. The results were compared with those in a database of surgeries performed with conventional titanium pistons. The effects of the self-crimping Nitinol prosthesis on the postoperative elimination of conductive hearing loss and its postoperative variations were investigated. The variations of postoperative residual conductive hearing loss were significantly smaller and the extent of conductive hearing-loss elimination greater in the Nitinol group. The mean postoperative residual conductive hearing loss was smaller in the Nitinol group. The postoperative stability of conductive hearing loss elimination was similar in both patient groups. Preliminary results suggest that the self-crimping shape-memory alloy Nitinol stapes piston overcomes the drawbacks of manual crimping in hearing restoration surgery for otosclerosis.     

5.9 Mb microdeletion in chromosome band 17q22-q23.2 associated with tracheo-esophageal fistula and conductive hearing loss

Only eight cases involving deletions of chromosome 17 in the region q22-q24 have been reported previously. We describe an additional case, a 7-year-old boy with profound mental retardation, severe microcephaly, facial dysmorphism, symphalangism, contractures of large joints, hyperopia, strabismus, bilateral conductive hearing loss, genital abnormality, psoriasis vulgaris and tracheo-esophageal fistula. Analysis with whole-genome SNP genotyping assay detected a 5.9 Mb deletion in chromosome band 17q22-q23.2 with breakpoints between 48,200,000-48,300,000 bp and 54,200,000-54,300,000 bp (according to NCBI 36). The aberration was confirmed by real-time quantitative PCR analysis. Haploinsufficiency of NOG gene has been implicated in the development of conductive hearing loss, skeletal anomalies including symphalangism, contractures of joints, and hyperopia in our patient and may also contribute to the development of tracheo-esophageal fistula and/or esophageal atresia.     

Multiple synostoses syndrome: Clinical report and retrospective analysis

Multiple synostoses syndrome (SYNS1; OMIM# 186500) is a rare autosomal dominant disorder reported in a few cases worldwide. We report a Chinese pedigree characterized by proximal symphalangism, conductive hearing loss, and distinctive facies. We examined the genetic cause and reviewed the literature to discuss the pathogeny, treatment, and prevention of SYNS1. Audiological, ophthalmological, and radiological examinations were evaluated. Whole‐exome sequencing (WES) was performed to identify mutations in the proband and her parents. Sanger sequencing was used to verify the results for the proband, parents, and grandmother. The literature on the genotype–phenotype correlation was reviewed. The patient was diagnosed with multiple synostoses syndrome clinically. WES and bioinformatic analysis revealed a novel missense mutation in the NOG gene, c.554C>G (p.Ser185Cys), cosegregated in this family. The literature review showed that the phenotype varies widely, but the typical facies, conductive hearing loss, and proximal symphalangism occurred frequently. All reported mutations are highly conserved in mammals based on conservation analysis, and there are regional hot spots for these mutations. However, no distinct genotype–phenotype correlations have been identified for mutations in NOG in different races. Regular systematic examinations and hearing aids are beneficial for this syndrome. However, the outcomes of otomicrosurgery are not encouraging owing to the regrowth of bone. This study expanded the mutation spectrum of NOG and is the first report of SYNS1 in a Chinese family. Genetic testing is recommended as part of the diagnosis of syndromic deafness. A clinical genetic evaluation is essential to guide prevention, such as preimplantation genetic diagnosis.     

Local delivery of siRNA using a biodegradable polymer application to enhance BMP-induced bone formation

Small interfering RNA (siRNA) is useful tool for specific and efficient knockdown of disease-related genes. However, in vivo applications of siRNA are limited due to difficulty in its efficient delivery to target cells. In this study, we investigated the efficacy of a biodegradable hydrogel, poly-d,l-lactic acid-p-dioxanone-polyethylene glycol block co-polymer (PLA-DX-PEG), as a siRNA carrier. PLA-DX-PEG pellets with or without fluorescein-labeled dsRNA were implanted into mouse dosal muscle pouches. The cellular uptake of dsRNA surround the polymer was confirmed by fluorescent microscopy. The fluorescence intensity was dose-dependent of the dsRNA, and exhibited a time-dependent decrease. To investigate its biological efficiency, noggin (antagonoist to BMPs) gene-silencing with siRNA (siRNA/Noggin) was examined by the amount of suppression of BMP-2-induced noggin expression and the level of performance of BMP, indicated by ectopic bone formation. Noggin gene expression induced by BMP-2 was suppressed by addition of siRNA/Noggin to the implant, and the ectopic bone formation induced by implants with both BMP-2 and siRNA/Noggin was significantly greater than those induced by implants with BMP-2 alone. These results indicate the efficacy of local delivery of siRNAs by PLA-DX-PEG polymer, which intensified bone-inducing effects of BMP and promoted new bone formation by suppressing gene expression of Noggin.     

Endogenous bone morphogenetic protein antagonists regulate mammalian neural crest generation and survival.

We demonstrate here that Chordin and Noggin function as bone morphogenetic protein (BMP) antagonists in vivo to promote mammalian neural crest development. Using Chrd and Nog single and compound mutants, we find that Noggin has a major role in promoting neural crest formation, in which Chordin is partially redundant. BMP signaling is increased in dorsal tissues lacking Noggin and is further increased when Chordin is also absent. The early neural crest domain is expanded with decreased BMP antagonism in vivo. Noggin and Chordin also regulate subsequent neural crest cell emigration from the neural tube. However, reduced levels of these BMP antagonists ultimately result in perturbation of neural crest cell derived peripheral nervous system and craniofacial skeletal elements. Such defects reflect, at least in part, a function to limit apoptosis in neural crest cells. Noggin and Chordin, therefore, function together to regulate both the generation and survival of neural crest cells in mammalian development.     

The Noggin null mouse phenotype is strain dependent and haploinsufficiency leads to skeletal defects.

Noggin is a secreted peptide that binds and inactivates Bone Morphogenetic Proteins, members of the transforming growth factor beta superfamily of secreted signaling molecules. In vertebrate limbs, Noggin is expressed in condensing cartilage and immature chondrocytes. Inactivation of the Noggin gene has been reported in an inbred 129X1/SvJ mouse genetic background. The null allele was lethal at 18.5 dpc and resulted in severe hyperplasia of the cartilage together with multiple joint fusions. In order to investigate the effect of the genetic background on the phenotypic manifestation of Noggin inactivation, we crossed the Noggin null allele into the outbred CD1 and inbred DBA1 and C57BL/6 mouse strains. We describe here skeletal phenotypes of Noggin null mice, such as accelerated or delayed mineralization of different bones suggestive of a complex tissue response to the perturbations in BMP balances. Additionally, we found that in the absence of Noggin, early specification of myogenic differentiation was unaffected, whereas terminal stages of myogenesis were delayed. Furthermore, we have discovered Noggin haploinsufficiency leading to carpal and tarsal fusions reminiscent of some phenotypes reported for NOGGIN haploinsufficiency in humans.     

Bone morphogenetic protein signaling regulates postnatal hair follicle differentiation and cycling

Hair follicle morphogenesis and cycling were examined in transgenic mice that overexpress the bone morphogenetic protein (BMP) inhibitor Noggin under the control of the neuron-specific enolase promoter. The Noggin transgene was misexpressed in the proximal portion of the hair follicle, primarily the matrix cells, apart from the usual expression in neurons. Transgene expression appeared only after induction of both the primary (tylotrich) and secondary (nontylotrich) pelage hair follicles had already occurred, thus allowing examination of the role of BMP signaling in follicles that had been induced normally in the presence of BMPs. The overexpression of Noggin in these animals resulted in a dramatic loss of hair postnatally. There was an apparently normal, but shortened period of postnatal hair follicle morphogenesis, followed by premature initiation of hair follicle cycling via entry into the first catagen transformation. This resulted in a complete loss of hair shafts from the nontylotrich hair follicles in these mice while the tylotrich hair follicles were normal. The onset of anagen of the first postnatal hair follicle cycle was also accelerated in the transgenic mice. Our results show that BMP signaling is specifically required for proper proliferation and differentiation during late morphogenesis of nontylotrich hair follicles and that inhibition of this signaling pathway may be one of the triggers for the onset of catagen when the follicles are in anagen and the onset of anagen when the follicles are in telogen. Ectopic sebocyte differentiation was another hallmark of the phenotype of these transgenic mice suggesting that BMP signaling may be an important determinant of lineage selection by common progenitor cells in the skin. BMPs likely promote a hair follicle-type differentiation pathway of keratinocytes while suppressing the sebaceous differentiation pathway of skin epithelium.