Variable phenotypes of multiple synostosis syndrome in patients with novel NOG mutations

Clinical observation and genetic analysis of a SYNS1 family caused by novel NOG gene mutation

Objective

Analyze the clinical and genetic characteristics of a rare Chinese family with Multiple synostoses syndrome and identify the causative variant with the high‐throughput sequencing approach.

Methods

The medical history investigation, physical examination, imaging examination, and audiological examination of the family members were performed. DNA samples were extracted from the family members. The candidate variant was identified by performing whole‐exome sequencing of the proband, then verified by Sanger sequencing in the family.

Results

The family named HBSY‐018 from Hubei province had 18 subjects in three generations, and six subjects were diagnosed with conductive or mixed hearing loss. Meanwhile, characteristic features including short philtrum, hemicylindrical nose, and hypoplastic alae nasi were noticed among those patients. Symptoms of proximal interdigital joint adhesion and inflexibility were found. The family was diagnosed as Multiple synostoses syndrome type 1 (SYNS1).The inheritance pattern of this family was autosomal dominant. A novel mutation in the NOG gene c.533G>A was identified by performing whole‐exome sequencing of the proband. The substitution of cysteine encoding 178th position with tyrosine (p.Cys178Tyr) was caused by this mutation, which was conserved across species. Co‐segregation of disease phenotypes was demonstrated by the family verification.

Conclusion

The family diagnosed as SYNS1 was caused by the novel mutation (c.533G>A) of NOG. The combination of clinical diagnosis and molecular diagnosis had improved the understanding of this rare disease and provided a scientific basis for genetic counseling in the family.

GDF5 mutation case report and a systematic review of molecular and clinical spectrum: Expanding current knowledge on genotype-phenotype correlations

INTRODUCTION

Brachydactyly is a bone development abnormality presenting with variable phenotypes and different transmission patterns. Mutations in GDF5 (Growth and Differentiation Factor 5, MIM *601146) account for a significant amount of cases. Here, we report on a three-generation family, where the proband and the grandfather have an isolated brachydactyly with features of both type A1 (MIM #112500) and type C (MIM #113100), while the mother shows only subtle hand phenotype signs.

MATERIALS AND METHODS

Whole Exome Sequencing (WES) was performed on the two affected individuals. An in-depth analysis of GDF5 genotype-phenotype correlations was performed through literature reviewing and retrieving information from several databases to elucidate GDF5-related molecular pathogenic mechanisms.

RESULTS

WES analysis disclosed a pathogenic variant in GDF5 (NM_000557.5:c.157dup; NP_000548.2:p.Leu53Profs*41; rs778834209), segregating with the phenotype. The frameshift variant was previously associated with Brachydactyly type C (MIM #113100), in heterozygosity, and with the severe Grebe type chondrodysplasia (MIM #200700), in homozygosity. In-depth analysis of literature and databases allowed to retrieve GDF5 mutations and correlations to phenotypes. We disclosed the association of 49 GDF5 pathogenic mutations with eight phenotypes, with both autosomal dominant and recessive transmission patterns. Clinical presentations ranged from severe defects of limb morphogenesis to mild redundant ossification. We suggest that such clinical gradient can be linked to a continuum of GDF5-activity variation, with loss of GDF5 activity underlying bone development defects, and gain of function causing disorders with excessive bone formation.

CONCLUSIONS

Our analysis of GDF5 pathogenicity mechanisms furtherly supports that mutation and zygosity backgrounds resulting in the same level of GDF5 activity may lead to similar phenotypes. This information can aid in interpreting the potential pathogenic effect of new variants and in supporting an appropriate genetic counseling.

Multiple synostoses syndrome: Radiological findings and orthopedic management in a single institution cohort

PURPOSE

Multiple synostoses syndrome (MSS) is a rare genetic condition. Classical features consist of joint fusions which notably start at the distal phalanx of the hands and feet with symphalangism progressing proximally to carpal, tarsal, radio-ulnar, and radio-humeral joints, as well as the spine. Usually, genetic testing reveals a mutation of the NOG gene with variable expressivity. The goal was to present the anatomical, functional, and radiological presentations of MSS in a series of patients followed since childhood.

METHODS

Patients with more than 3 synostoses affecting at least one hand joint were included. When possible, genetic screening was offered.

RESULTS

A retrospective study was performed from 1972 to 2017 and included 14 patients with a mean follow-up of 18.6 years. Mutation of the NOG protein coding gene was seen in 3 patients. All presented with tarsal synostoses including 9 carpal, 7 elbow, and 2 vertebral fusions. Facial dysmorphia was seen in 6 patients and 3 were hearing-impaired. Surgical treatment of tarsal synostosis was performed in 4 patients. Progressing joint fusions were invariably seen on x-rays amongst adults.

CONCLUSION

Long radiological follow-up allowed the assessment of MSS progression. Feet deformities resulted in a severe impact on quality of life, and neurological complications secondary to spine fusions warranted performing at least one imaging study in childhood. As there is no treatment of ankylosis, physiotherapy is not recommended. However, surgical arthrodesis for the treatment of pain may have reasonable outcomes.

Effect of lentivirus-mediated miR-182 targeting FGF9 on hallux valgus

The pathogenesis of hallux valgus is not clearly understood. However, genetics research about hallux valgus is rare. Therefore, the present study aimed to explore the pathogeny of hallux valgus from the perspective of genetics. Human samples were collected from normal bone tissue and hallux valgus region bone tissue. The bone samples were studied using real time-PCR, western blot and immunohistochemical. Lentivirus-mediated miR-182 transfected osteoblasts and tested the expression of FGF9 mRNA with real time-PCR. To test alkaline phosphatase activity, number of calcium nodules and proliferation of osteoblast with enzymatic activity analysis, calcium nodules stained and MTT assay. We found that (1) FGF9 expressed in hallux valgus region bone tissue was significantly higher than normal bone tissue. (2) miR-182 expression levels in hallux valgus region bone tissue were notably lower than those of normal bone tissue. (3) miR-182 could negatively regulate the expression of FGF9 in osteoblasts. (4) FGF9 may enhance osteoblasts proliferation. We have demonstrated that miR-182 promotes the formation of bone by targeting FGF9, implicating an essential role of miR-182 in the etiology of hallux valgus. Moreover, miR-182 might potentially be a therapeutic target for hallux valgus treatment.

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.

Identification of a novel mutation of NOG in family with proximal symphalangism and early genetic counseling

BACKGROUND

Proximal symphalangism is a rare disease with multiple phenotypes including reduced proximal interphalangeal joint space, symphalangism of the 4th and/or 5th finger, as well as hearing loss. At present, at least two types of proximal symphalangism have been identified in the clinic. One is proximal symphalangism-1A (SYM1A), which is caused by genetic variants in Noggin (NOG), another is proximal symphalangism-1B (SYM1B), which is resulted from Growth Differentiation Factor 5 (GDF5) mutations.

CASE PRESENTATION

Here, we reported a Chinese family with symphalangism of the 4th and/or 5th finger and moderate deafness. The proband was a 13-year-old girl with normal intelligence but symphalangism of the 4th finger in the left hand and moderate deafness. Hearing testing and inner ear CT scan suggested that the proband suffered from structural deafness. Family history investigation found that her father (II-3) and grandmother (I-2) also suffered from hearing loss and symphalangism. Target sequencing identified a novel heterozygous NOG mutation, c.690C > G/p.C230W, which was the genetic lesion of the affected family. Bioinformatics analysis and public databases filtering further confirmed the pathogenicity of the novel mutation. Furthermore, we assisted the family to deliver a baby girl who did not carry the mutation by genetic counseling and prenatal diagnosis using amniotic fluid DNA sequencing.

CONCLUSION

In this study, we identified a novel NOG mutation (c.690C > G/p.C230W) by target sequencing and helped the family to deliver a baby who did not carry the mutation. Our study expanded the spectrum of NOG mutations and contributed to genetic diagnosis and counseling of families with SYM1A.

Novel NOG (p.P42S) mutation causes proximal symphalangism in a four-generation Chinese family

Background

Proximal symphalangism (SYM1; OMIM 185800), also called Cushing’s symphalangism, is an infrequent autosomal dominant disease. An SYM1 patient typically features variable fusion of proximal interphalangeal joints in the hands and feet.

Methods

We recruited a four-generation Chinese non-consanguineous family with SYM1. We examined their hands and feet using X-rays to confirm fusion of proximal interphalangeal joints. We evaluated their audiology using standard audiometric procedures and equipment. Then, we identified genetic variants using whole exome sequencing and validated mutations using Sanger sequencing. Mutation pathogenicity was analyzed with bioinformatics.

Results

Radiographs revealed proximal-joint fusion of fingers and toes in the patients. Two elderly individuals (II:1 and II:4) exhibited slight hearing loss. Additionally, we detected a novel heterozygous missense mutation in exon 1 of NOG (NM_005450) c.124C > T, p.(Pro42Ser) in all patients. This c.124C > T mutation is highly conserved across multiple species and the p.(Pro42Ser) variation is potentially highly pathogenic.

Conclusion

Our results suggest that heterozygous c.124C > T, p.(Pro42Ser) in NOG is a novel mutation that causes human SYM1 phenotype.

Electronic supplementary material

The online version of this article (10.1186/s12881-019-0864-1) contains supplementary material, which is available to authorized users.

Nonsyndromic Massive Tarsal and Tarsometatarsal Coalitions in a Young Female

Tarsal coalition is an abnormal connection between 2 or more tarsal bones, with the most common sites being between the talus and the calcaneus and between the navicular and the calcaneus. The occurrence of multiple and massive tarsal coalitions is rare. We describe a rare case of nonsyndromic bilateral tarsal coalition involving most of the tarsal bones and extending to the metatarsal bones in a 4-year-old female. The condition was not painful and did not affect her gait. The main concern was the abnormal shape of her feet. Tarsal coalition can occur as an isolated anomaly or in association with other congenital disorders, usually presenting around the age of 12 years. The coexistence of nonsyndromic bilateral multiple tarsal coalitions is seldom reported. Regardless of the presentation, treatment is not indicated in cases of asymptomatic tarsal coalition. Our patient had a unique presentation of tarsal coalition, involving both the tarsal and tarsometatarsal bones. To our knowledge, this is the first report of this type of presentation.

Autosomal dominant stapes fixation, syndactyly, and symphalangism in a family with NOG mutation: Long term follow-up on surgical treatment

OBJECTIVE

Evaluation of clinical findings and audiological outcome after surgery in a Danish family with autosomal dominant facio-audio-symphalangism syndrome with stapes fixation, syndactyly and symphalangism.

METHODS

Retrospective report on eight affected family members in a Danish family. Clinical investigation included X-ray, audiology and in one case video-recorded surgery. Main outcome measure was audiologic results after stapedectomy. Sanger DNA sequencing of NOG was performed on peripheral blood.

RESULTS

Audiologic analysis showed that seven of eight affected family members had bilateral conductive hearing loss. Three patients were treated with stapedectomy, on one or both ears, due to fixation of stapes. All the affected members had syndactyly and symphalangism. A not previously reported mutation in the NOG gene (c.688_699del, p.Cys230_Cys232delins11) was found to segregate with the stapes fixation, syndactyly, and symphalangism. p.Cys230_Cysdelins11 was classified as likely pathogenic according to guidelines from the American College of Medical Genetics and Genomics.

CONCLUSION

The clinical presentation of the reported mutation corresponds with previous case reports of families with NOG mutation. In this family, surgery with stapedectomy had lasting effect without renewed fixation of the stapes in a follow up period of 18 months-38 years.