Hearing loss in the nonocular Stickler syndrome caused by a COL11A2 mutation

Hearing Loss in Stickler Syndrome: An Update

Stickler syndrome is a connective tissue disorder characterized by ocular, skeletal, orofacial and auditory manifestations. Its main symptoms are high myopia, retinal detachment, joint hypermobility, early osteoarthritis, cleft palate, midfacial hypoplasia, micrognathia and hearing loss. Large phenotypical variability is apparent and partly explained by the underlying genetic heterogeneity, including collagen genes (COL2A1, COL11A1, COL11A2, COL9A1, COL9A2, COL9A3) and non-collagen genes (BMP4, LRP2, LOXL3). The most frequent type of Stickler syndrome (COL2A1) is characterized by a rather mild high-frequency sensorineural hearing loss in about half of the patients. COL11A1- and COL11A2-related Stickler syndrome results in more frequent hearing loss, being moderate and involving all frequencies. Hearing loss in the rarer types of Stickler syndrome depends on the gene expression in the cochlea, with moderate to severe downsloping hearing loss for Stickler syndrome caused by biallelic type IX collagen gene mutations and none or mild hearing loss for the non-collagen genes. Inherent to the orofacial manifestations, middle ear problems and temporary conductive hearing loss, especially at young age, are also prevalent. Consequently, hearing loss should be actively sought for and adequately treated in Stickler syndrome patients given its high prevalence and the concomitant visual impairment in most patients.

Mutation Spectrum and De Novo Mutation Analysis in Stickler Syndrome Patients with High Myopia or Retinal Detachment

Stickler syndrome is a connective tissue disorder that affects multiple systems, including the visual system. Seven genes were reported to cause Stickler syndrome in patients with different phenotypes. In this study, we aimed to evaluate the mutation features of the phenotypes of high myopia and retinal detachment. Forty-two probands diagnosed with Stickler syndrome were included. Comprehensive ocular examinations were performed. A targeted gene panel test or whole exome sequencing was used to detect the mutations, and Sanger sequencing was conducted for verification and segregation analysis. Among the 42 probands, 32 (76%) presented with high myopia and 29 (69%), with retinal detachment. Pathogenic mutations were detected in 35 (83%) probands: 27 (64%) probands had COL2A1 mutations, and eight (19%) probands had COL11A1 mutations. Truncational mutations in COL2A1 were present in 21 (78%) probands. Missense mutations in COL2A1 were present in six probands, five of which presented with retinal detachment. De novo COL2A1 mutations were detected in 10 (37%) probands, with a mean paternal childbearing age of 29.64 ± 4.97 years old. The mutation features of probands with high myopia or retinal detachment showed that the probands had a high prevalence of COL2A1 mutations, truncational mutations, and de novo mutations.

Audiologic Manifestations of Marshall Syndrome

OBJECTIVE

Marshall syndrome is a genetic disorder caused by mutations in the COL11A1 gene. This syndrome is characterized by skeletal, ophthalmologic, craniofacial, and auditory abnormalities. Hearing loss is among the main manifestations reported in this disorder being observed in approximately 80% of affected individuals.The present study aims to describe the audiologic characteristics of three members of a family with Marshall syndrome and also serves as a review of the literature.

STUDY DESIGN

Family study.

SETTING

Tertiary care otology and skull base center.

PATIENTS

We report the audiologic findings in a family with Marshall syndrome consisting of a mother and her son and daughter.

INTERVENTION(S)

The audiologic evaluation included tympanometry, acoustic reflexes testing, auditory brainstem response, transient otoacoustic emissions, pure-tone audiometry, speech audiometry in quiet, and conditioned play audiometry. These methods were applied according to the age of the patients. In addition, we provide a review of the English-language literature in an attempt to clarify the auditory phenotype of this syndrome.

RESULTS

All 3 affected individuals had heterozygous c.3816+1G>A mutation in the splicing donor site of intron 50 of the COL11A1 gene. All three patients in our study had bilateral sensorineural hearing loss. Hearing impairment ranged from mild to moderate in the daughter, moderate in the son, and from mild to moderate in their mother.

CONCLUSION

The majority of individuals with Marshall syndrome present early-onset bilateral sensorineural hearing loss. Hearing impairment is usually detected in early childhood, progresses gradually, and becomes stable in late adulthood, with a severity ranging from mild to severe.

Stickler syndrome: exploring prophylaxis for retinal detachment

PURPOSE OF REVIEW

The literature regarding prophylactic treatment of rhegmatogenous retinal detachment in Stickler syndrome remains controversial. We review major published clinical studies and offer a critical analysis of this subject.

SUMMARY

Stickler syndrome is a systemic collagenopathy affecting multiple organ systems including the eye, ear, and skeleton. Stickler syndrome is probably the most common cause of genetically determined pediatric rhegmatogenous retinal detachment. Congenital developmental anomalies constitute over half rhegmatogenous detachments (RRD) in patients less than 10 years. The majority are caused by hereditary vitreoretinopathies associated with Stickler syndrome. Sixty percent of patients with Stickler syndrome develop RRD's over their lifetime with possible severe visual loss and subsequent lifelong morbidity. In view of these complications, some have emphasized the importance of prophylactic laser treatment to the retina of patients with Stickler syndrome to reduce the occurrence of and/or prevent future rhegmatogenous retinal detachment, but there appears to be insufficient data to support the absolute benefit of such prophylactic treatment. Guidelines regarding the age at prophylactic treatment as well as type and frequency of intervention are scarce and would benefit from additional clinical investigations.

Understanding chondrodysplasia (cho): A comprehensive review of cho as an animal model of birth defects, disorders, and molecular mechanisms

BACKGROUND

The mutant chondrodysplasia (cho) is a cartilage-targeting disorder in C57BL mice that results in dwarfing and other malformations stemming from this collagenopathy. Clarke Fraser made the discovery of the mutation accidentally in the early 1960s during the thalidomide tragedy.

METHODS

For this review we identified key research on cho as since its discovery. Relevant data were compiled to make a comprehensive review that details discoveries associated with the cho mutation, that describes the associated phenotypes and molecular mechanisms, and that provides a discussion surrounding its current clinical relevance.

RESULTS

Mechanistically, cho acts by hindering chondrogenesis and endochondral bone formation. The phenotype results from a 1-nt deletion in the gene encoding the alpha 1 chain of type XI collagen. For more than half a century, researchers have studied the pathogenesis of the cho mutation in relation to a variety of mouse models of human birth defects and disease. These studies have resulted in several discoveries linking cho with such human disorders as dwarfism, tracheal stenosis, cleft palate, pulmonary hypoplasia, and osteoarthritis (OA).

CONCLUSION

The study of cho has led to numerous advances in understanding human birth defects, congenital disorders, and adult human disease. The most recent studies have suggested a role for the TGF-Beta, HtrA1, Ddr2, and Mmp-13 pathway in the degradation of articular cartilage and the development of OA in cho/+ mice. We have shown that the anti-hypertension drug Losartan is a TGF-Beta blocker that could be used to treat OA in Stickler syndrome, and thereby rescue the WT phenotype.

Auditory phenotype in Stickler syndrome: results of audiometric analysis in 20 patients

Hearing loss in Stickler syndrome has received little attention due to the often more disabling ocular, orofacial and skeletal manifestations. Estimates suggest a global prevalence of sensorineural hearing loss (SNHL) ranging from 50 % to about 100 % though, depending on the underlying Stickler genotype. By performing extensive audiometric analysis in Stickler patients, we aimed to further elucidate the auditory phenotype. Twenty molecularly confirmed Stickler patients (age 10-62 year), of whom sixteen with type 1 Stickler syndrome (COL2A1 mutation) and four with type 2 Stickler syndrome (COL11A1 mutation) underwent an otological questionnaire, clinical examination, pure tone and speech audiometry, tympanometry and otoacoustic emission testing. Cross-sectional and longitudinal regression analysis of the audiograms was performed to assess progression. In type 1 Stickler syndrome, 75 % demonstrated hearing loss, predominantly in the high frequencies. No significant progression beyond presbyacusis was observed. All type 2 Stickler patients exhibited mild-to-moderate low- and mid-frequency SNHL and moderate-to-severe high-frequency SNHL. In both types, hearing loss was observed in childhood. Otoacoustic emissions were only detectable in 7/40 ears and had very low amplitudes, even in frequency bands with normal hearing on pure tone audiometry. Type 1 Stickler syndrome is characterized by a mild high-frequency SNHL, emerging in childhood and non-progressive. Absent otoacoustic emissions are a frequent finding. Patients with type 2 Stickler syndrome exhibit early-onset moderate SNHL affecting all frequencies with a sloping audiogram. Taking into account the visual impairment in many patients, we recommend regular auditory follow-up in patients with Stickler syndrome, especially in childhood.

Hearing impairment in Stickler syndrome: a systematic review

Background

Stickler syndrome is a connective tissue disorder characterized by ocular, skeletal, orofacial and auditory defects. It is caused by mutations in different collagen genes, namely COL2A1, COL11A1 and COL11A2 (autosomal dominant inheritance), and COL9A1 and COL9A2 (autosomal recessive inheritance). The auditory phenotype in Stickler syndrome is inconsistently reported. Therefore we performed a systematic review of the literature to give an up-to-date overview of hearing loss in Stickler syndrome, and correlated it with the genotype.

Methods

English-language literature was reviewed through searches of PubMed and Web of Science, in order to find relevant articles describing auditory features in Stickler patients, along with genotype. Prevalences of hearing loss are calculated and correlated with the different affected genes and type of mutation.

Results

313 patients (102 families) individually described in 46 articles were included. Hearing loss was found in 62.9%, mostly mild to moderate when reported. Hearing impairment was predominantly sensorineural (67.8%). Conductive (14.1%) and mixed (18.1%) hearing loss was primarily found in young patients or patients with a palatal defect. Overall, mutations in COL11A1 (82.5%) and COL11A2 (94.1%) seem to be more frequently associated with hearing impairment than mutations in COL2A1 (52.2%).

Conclusions

Hearing impairment in patients with Stickler syndrome is common. Sensorineural hearing loss predominates, but also conductive hearing loss, especially in children and patients with a palatal defect, may occur. The distinct disease-causing collagen genes are associated with a different prevalence of hearing impairment, but still large phenotypic variation exists. Regular auditory follow-up is strongly advised, particularly because many Stickler patients are visually impaired.

Audiological findings in otospondylomegaepiphyseal dysplasia (OSMED) associated with a novel mutation in COL11A2

The aim of the study was to assess the audiological findings of a 4-year-old child with a homozygous COL11A2 mutation and to point out the role of continuous follow-ups in children with craniofacial syndromes after the newborn hearing screening. A 4-year-old boy with otospondylomegaepiphyseal dysplasia (OSMED) was followed up after birth for hearing loss. Transient Otoacoustic Emissions (TEOAEs), Distortion Product Otoacoustic Emissions (DPOAEs), Automated and Clinical Auditory Brainstem Response (AABR and ABR) measurements, Visual Reinforcement Audiometry, immitansmetric measurements and hearing threshold measurements were performed for audiological evaluation. The patient developed sensorineural hearing loss at 11 months of age while his hearing was normal at birth. Because of auditory-verbal training with hearing aids started at 20 months of age, he now has normal verbal communication with his peers. This study clearly demonstrates that hearing loss develops in infancy in patients with OSMED and underscores the importance of continued hearing screening beyond newborn period for early intervention of hearing impairment and communication problems.

A novel retinoic acid-response element requires an enhancer element mediator for transcriptional activation

The Col11a2 gene codes for alpha2(XI), a subunit of type XI collagen that is a critical component of the cartilage extracellular matrix. The 5' regulatory region of Col11a2 was subjected to deletional analysis to detect any regulatory element in addition to the two known chondrocyte-specific enhancer elements B/C and D/E. Deletion of the region from -342 to -242 bp reduced transcriptional activity to less than 50% of wild-type, but the sequence showed no independent ability to increase transcription from a minimal promoter. When cloned downstream of the D/E enhancer, however, a subsection of the sequence nearly doubled transcriptional activity and produced an additional 3-fold activation in response to RA (retinoic acid). A 6-bp direct repeat, separated by 4 bp (a DR-4 element) near the 5'-end of this region, was found to be essential for its activity, and was further shown to bind the RA X receptor beta in electrophoretic mobility-shift assays. The present study has revealed a novel RA-response element in Col11a2 that does not interact directly with the promoter, but instead requires the D/E enhancer to mediate transcriptional activation. Proteins bound at the enhancer, therefore, would be expected to affect the transcriptional response to RA. Such a system of regulation, particularly if found to be operating in other cartilage genes, could explain the conflicting responses RA produces in chondrocytes under different experimental conditions.

Stickler syndrome type I and Stapes ankylosis

OBJECTIVE

To report a successful stapedectomy for stapedial fixation in a patient with Stickler syndrome type I (COL2A1).

SETTING

University Hospital Department for Otology, Pathology, Ophthalmology and Clinical Genetics.

STUDY DESIGN

A clinical and genetic evaluation of a mother and daughter focusing mainly on the otological, ophthalmological, histological and genetical aspects.

INTERVENTION

A stapedectomy was performed successfully.

RESULTS

Hearing impairment improved after stapedectomy. Postoperatively a shift in high-frequency threshold wa seen related to the stapedectomy. A new mutation in COL2A1 gene was dectected.

CONCLUSION

Stapedial fixation can be the cause of hearing impairment in Stickler syndrome type I (COL2A1). The hearing impairment can be improved by stapes surgery.

Alport syndrome: HLA association and kidney graft outcome

Alport syndrome (AS) is a genetic disease of type IV collagen involving non-homogeneous patterns of inheritance characterized clinically by the presence of progressive haematuric nephritis leading to end-stage renal disease (ESRD), hearing loss and/or ophthalmologic abnormalities. The aim of this study was to investigate, in a cohort of AS patients who had undergone a kidney graft (KG) or who were still on a waiting list for a KG, (a) whether there is a correlation between AS and HLA antigen expression, and (b) long-term graft outcome in transplant patients. The AS cohort was represented by 34 ESRD patients, of whom 25 received a KG and the remaining nine were still on a waiting list. AS transplant patients represented 2.78% of 899 first KGs performed at our centre (Transplantation Department at S. Martino Hospital, Genoa) between 1983 and 2002. Grafts were procured from cadaveric donors in 18 cases and from living, related donors in seven cases. All AS transplant patients had a post-transplant follow-up period of at least 12 months. Results showed that: (i) the frequency of the HLA-DRB1*16 antigen was significantly increased in the whole AS cohort as compared to 128 healthy subjects (HS) (corrected P-value 0.0026; relative risk 7.20) as well as to 232 non-AS ESRD patients on a waiting list for KG (corrected P-values 0.0156; relative risk 4.67); (ii) 5- and 10-year graft survivals in the AS transplant patients were 80 and 73%, respectively, and did not differ from those of a control group represented by 25 non-AS KG recipients matched for sex, age, number of HLA mismatches and immunosuppressive treatment. Increased frequency of HLA-DRB1*16 in AS patients may reflect a linkage disequilibrium with genes coding for collagen synthesis.

Auditory function associated with Col11a1 haploinsufficiency in chondrodysplasia (cho) mice

Heterozygosity for mutations in the fibrillar collagen gene COL11A1 causes sensorineural hearing loss in patients with Stickler syndrome or Marshall syndrome. Chondrodysplasia (cho) is a functional null allele of Col11a1 that causes lethal chondrodysplasia in cho/cho newborn mice, and osteoarthritis in cho/+ heterozygotes. To determine if Col11a1 haploinsufficiency causes hearing loss in cho/+ mice, auditory brainstem response (ABR) thresholds were measured at 2, 4, 6, 8 and 10 months of age. There was no difference in ABR thresholds for click and tone burst stimuli between cho/+ and +/+ mice at all ages. In contrast to the conclusion of a previous report, our results indicate that Col11a1 haploinsufficiency does not cause significant hearing loss on the C57BL/6 strain background. We conclude that Stickler syndrome and Marshall syndrome mutations in COL11A1 cause hearing loss via dominant negative effects upon wild-type fibrillar collagen polypeptides in the extracellular matrices of the cochlea.