Waardenburg syndrome type II: phenotypic findings and diagnostic criteria

Clinical Insights Into Waardenburg-Shah Syndrome: A Case Series and Literature Review

Researching Waardenburg syndrome (WS) underscores its rarity and complex symptomatology, presenting as a congenital disorder predominantly inherited in an autosomal dominant pattern. It exhibits incomplete penetrance, which results in a wide range of clinical manifestations, with variable phenotypic presentations within the same family as well. The most commonly found features are facial abnormalities, hypopigmentation of the skin, heterochromia iridis, and conductive deafness. Adding to the eccentricities of this syndrome are its four subtypes, each presenting with its specific clinical features, which helps in delineating the subtype. A mutated paired box 3 (PAX3​​​​​) gene manifests as type 1 Waardenburg, which is characterized by sideways displacement of the inner angles of the eyes (i.e., dystopia canthorum), widely spaced eyes, congenital sensorineural hearing impairment, and patchy pigmentation of the iris, skin, and hair. Due to insufficient research, it has been difficult to isolate all the genetic mutations responsible for type 2, but its phenotype is very similar to type 1 with minor differences. Type 3 is characterized by musculoskeletal abnormalities. Waardenburg-Shah syndrome (type 4), which is associated with Hirschsprung disease, is the rarest subtype and is caused by genetic mutations in the endothelin receptor type B (EDNRB), endothelin-3 (EDN3), or sex-determining region Y (SRY) box 10 (SOX10) gene. We present a case series of this unique subtype that presented with a typical history of constipation due to Hirschsprung disease and had phenotypic manifestations of white forelock, heterochromia iridis, and bilateral sensorineural hearing loss (SNHL). In parallel with a positive 1° family history of a white forelock, we reflect on the fundamentals of this unique syndrome, as well as its management protocols, highlighting the importance of genetic counseling and cultivation of a high index of suspicion for its diagnosis.

Waardenburg syndrome type 2 with a de novo variant of the SOX10 gene: a case report

BACKGROUND

Waardenburg syndrome type 2 (WS2) has been reported to be a rare hereditary disorder, which is distinguished by vivid blue eyes, varying degrees of hearing impairment, and abnormal pigment deposition in the skin and hair. Variants in the sex-determining region Y-box containing gene 10 (SOXl0) gene may cause congenital deafness and have been demonstrated to be important during the development of WS2.

METHODS

Complete clinical data of the proband and her family members (her parents and 2 sisters) was collected and physical examinations were performed in the hospital. The laboratory examination including hemoglobin, Coomb's test, urine protein, ENA, autoimmune hepatitis-related autoantibodies and ultrasonography were all conducted. We obtained the peripheral blood samples from all the participants and performed whole exome sequencing and sanger sequencing validation.

RESULTS

The present study identified a family of 5 members, and only the proband exhibited typical WS2. Beyond the characteristics of WS2, the proband also manifested absence of puberty. The proband and her younger sister manifested systemic lupus erythematosus (SLE). Whole exome sequencing revealed a de novo variant in the SOX10 gene. The variant c.175 C > T was located in exon 2 of the SOX10 gene, which is anticipated to result in early termination of protein translation.

CONCLUSION

The present study is the first to report a case of both WS2 and SLE, and the present findings may provide a new insight into WS2.

Waardenburg Syndrome Type 2 in Paediatrics: A Case Highlighting Diagnostic Complexities and the Efficacy of Cochlear Implantation

Waardenburg Syndrome Type 2 (WS2) is a rare hereditary condition with a low prevalence, characterized by abnormalities in both auditory function and pigmentation. We present a case of a 2-year-old female child who exhibited reduced vocalizations, delayed speech development, and distinctive heterochromic irides. Initial auditory assessments revealed bilateral severe to profound hearing loss. Subsequent MRI findings confirmed bilateral aplasia of the posterior semicircular canals, consistent with a diagnosis of Waardenburg syndrome type 2. While standard treatments using bilateral Behind-The-Ear (BTE) power hearing aids yielded only modest improvements, cochlear implantation significantly enhanced auditory perception and speech abilities within 18 months. This report underscores the diagnostic intricacies of WS2 and highlights the profound benefits of cochlear implantation in addressing associated auditory challenges.

Loss of Pax3 causes reduction of melanocytes in the developing mouse cochlea

Cochlear melanocytes are intermediate cells in the stria vascularis that generate endocochlear potentials required for auditory function. Human PAX3 mutations cause Waardenburg syndrome and abnormalities of skin and retinal melanocytes, manifested as congenital hearing loss (~ 70%) and hypopigmentation of skin, hair and eyes. However, the underlying mechanism of hearing loss remains unclear. Cochlear melanocytes in the stria vascularis originated from Pax3-traced melanoblasts and Plp1-traced Schwann cell precursors, both of which derive from neural crest cells. Here, using a Pax3-Cre knock-in mouse that allows lineage tracing of Pax3-expressing cells and disruption of Pax3, we found that Pax3 deficiency causes foreshortened cochlea, malformed vestibular apparatus, and neural tube defects. Lineage tracing and in situ hybridization show that Pax3+ derivatives contribute to S100+, Kir4.1+ and Dct+ melanocytes (intermediate cells) in the developing stria vascularis, all of which are significantly diminished in Pax3 mutant animals. Taken together, these results suggest that Pax3 is required for the development of neural crest cell-derived cochlear melanocytes, whose absence may contribute to congenital hearing loss of Waardenburg syndrome in humans.

Modeling of pigmentation disorders associated with MITF mutation in Waardenburg syndrome revealed an impaired melanogenesis pathway in iPS-derived melanocytes

Waardenburg Syndrome (WS) is a rare genetic disorder that leads to congenital hearing loss and pigmentation defects. Microphthalmia-associated transcription factor (MITF) is one of its significant pathogenic genes. Despite the comprehensive investigation in animal models, the pathogenic mechanism is still poorly described in humans due to difficulties accessing embryonic tissues. In this work, we used induced pluripotent stem cells derived from a WS patient carrying a heterozygous mutation in the MITF gene c.626A>T (p.His209Leu), and differentiated toward melanocyte lineage, which is the most affected cell type involved in WS. Compared with the wild-type cell line, the MITFmut cell line showed a reduced expression of the characteristic melanocyte-related genes and a lesser proportion of mature, fully pigmented melanosomes. The transcriptome analysis also revealed widespread gene expression changes at the melanocyte stage in the MITFmut cell line. The differentially expressed genes were enriched in melanogenesis and cell proliferation-related pathways. Interestingly, ion transport-related genes also showed a significant difference in MITFmut -induced melanocytes, indicating that the MITF mutant may lead to the dysfunction of potassium channels and transporters produced by intermediate cells in the cochlea, further causing the associated phenotype of deafness. Altogether, our study provides valuable insights into how MITF mutation affects WS patients, which might result in defective melanocyte development and the related phenotype based on the patient-derived iPSC model.

Waardenburg Syndrome: The Contribution of Next-Generation Sequencing to the Identification of Novel Causative Variants

Waardenburg syndrome (WS) is characterized by hearing loss and pigmentary abnormalities of the eyes, hair, and skin. The condition is genetically heterogeneous, and is classified into four clinical types differentiated by the presence of dystopia canthorum in type 1 and its absence in type 2. Additionally, limb musculoskeletal abnormalities and Hirschsprung disease differentiate types 3 and 4, respectively. Genes PAX3, MITF, SOX10, KITLG, EDNRB, and EDN3 are already known to be associated with WS. In WS, a certain degree of molecularly undetected patients remains, especially in type 2. This study aims to pinpoint causative variants using different NGS approaches in a cohort of 26 Brazilian probands with possible/probable diagnosis of WS1 (8) or WS2 (18). DNA from the patients was first analyzed by exome sequencing. Seven of these families were submitted to trio analysis. For inconclusive cases, we applied a targeted NGS panel targeting WS/neurocristopathies genes. Causative variants were detected in 20 of the 26 probands analyzed, these being five in PAX3, eight in MITF, two in SOX10, four in EDNRB, and one in ACTG1 (type 2 Baraitser-Winter syndrome, BWS2). In conclusion, in our cohort of patients, the detection rate of the causative variant was 77%, confirming the superior detection power of NGS in genetically heterogeneous diseases.

Pax3 deficiency diminishes melanocytes in the developing mouse cochlea

Cochlear melanocytes are intermediate cells in the stria vascularis that generate endocochlear potentials required for auditory function. Human PAX3 mutations cause Waardenburg syndrome and abnormalities of melanocytes, manifested as congenital hearing loss and hypopigmentation of skin, hair and eyes. However, the underlying mechanism of hearing loss remains unclear. During development, cochlear melanocytes in the stria vascularis are dually derived from Pax3-Cre+ melanoblasts migrating from neuroepithelial cells including neural crest cells and Plp1+ Schwann cell precursors originated from also neural crest cells, differentiating in a basal-apical manner. Here, using a Pax3-Cre mouse line, we found that Pax3 deficiency causes foreshortened cochlea, malformed vestibular apparatus, and neural tube defects. Lineage tracing and in situ hybridization show that Pax3-Cre derivatives contribute to S100+ , Kir4.1+ and Dct+ melanocytes (intermediate cells) in the developing stria vascularis, all significantly diminished in Pax3 mutant animals. Taken together, these results suggest that Pax3 is required for the development of neural crest cell-derived cochlear melanocytes, whose absence may contribute to congenital hearing loss of Waardenburg syndrome in human.

A comprehensive genotype-phenotype evaluation of eight Chinese probands with Waardenburg syndrome

Background

Waardenburg syndrome (WS) is the most common form of syndromic deafness with phenotypic and genetic heterogeneity in the Chinese population. This study aimed to clarify the clinical characteristics and the genetic cause in eight Chinese WS families (including three familial and five sporadic cases). Further genotype–phenotype relationships were also investigated.

Methods

All probands underwent screening for the known WS-related genes including PAX3, SOX10, MITF, EDNRB, EDN3, and SNAI2 using next-generation sequencing to identify disease-causing genes. Further validation using Sanger sequencing was performed. Relevant findings for the associated genotype–phenotype from previous literature were retrospectively analyzed.

Result

Disease-causing variants were detected in all eight probands by molecular genetic analysis of the WS genes (SOX10(NM_006941.4): c.544_557del, c.553 C > T, c.762delA, c.336G > A; MITF(NM_000248.3): c.626 A > T; PAX3(NM_181459.4): c.838delG, c.452-2 A > G, c.214 A > G). Six mutations (SOX10:c.553 C > T, c.544_557del, c.762delA; PAX3: c.838delG, c.214 A > G; MITF:c.626 A > T) were first reported. Clinical evaluation revealed prominent phenotypic variability in these WS patients. Twelve WS1 cases and five WS2 cases were diagnosed in total. Two probands with SOX10 mutations developed progressive changes in iris color with age, returning from pale blue at birth to normal tan. Additionally, one proband had a renal malformation (horseshoe kidneys).All cases were first described as WS cases. Congenital inner ear malformations were more common, and semicircular malformations were exclusively observed in probands with SOX10 mutations. Unilateral hearing loss occurred more often in cases with PAX3 mutations.

Conclusion

Our findings helped illuminate the phenotypic and genotypic spectrum of WS in Chinese populations and could contribute to better genetic counseling of WS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01379-6.

Genetic insights, disease mechanisms, and biological therapeutics for Waardenburg syndrome

Waardenburg syndrome (WS), also known as auditory-pigmentary syndrome, is the most common cause of syndromic hearing loss (HL), which accounts for approximately 2-5% of all patients with congenital hearing loss. WS is classified into four subtypes depending on the clinical phenotypes. Currently, pathogenic mutations of PAX3, MITF, SOX10, EDN3, EDNRB or SNAI2 are associated with different subtypes of WS. Although supportive techniques like hearing aids, cochlear implants, or other assistive listening devices can alleviate the HL symptom, there is no cure for WS to date. Recently major progress has been achieved in preclinical studies of genetic HL in animal models, including gene delivery and stem cell replacement therapies. This review focuses on the current understandings of pathogenic mechanisms and potential biological therapeutic approaches for HL in WS, providing strategies and directions for implementing WS biological therapies, as well as possible problems to be faced, in the future.

Hearing characteristics and cochlear implant effects in children with Waardenburg syndrome: a case series

BACKGROUND

Waardenburg syndrome (WS) has high clinical and genetic heterogeneity. We aimed to investigate the clinical characteristics of children with WS, and to analyze the effect of cochlear implantation in children with WS who had severe sensorineural hearing loss.

METHODS

The clinical characteristics of children with WS diagnosed and treated in the past 5 years in the Department of Otolaryngology, Shanghai Children's Hospital were retrospectively analyzed. The 5 WS cases, including 2 males and 3 females, had bilateral severe sensorineural hearing loss. Cochlear implantation was performed between 8 and 21 months old. Audiology tests were conducted, including otoacoustic emissions (OAEs), auditory brainstem response (ABR), and multiple auditory steady-state evoked responses (ASSR). Preoperative computerized tomography (CT) and magnetic resonance imaging (MRI) were performed to evaluate the development of the inner ear and brain. All WS cases were evaluated for hearing and speech abilities before cochlear implantation and at 1 month, 6 months, 12 months, and 24 months after implantation.

RESULTS

Among the 5 cases, 3 were WS1, 1 was WS2, and 1 was WS4. All 5 cases received cochlear implantation, and postoperative CT showed that the implant position was good. The infant toddler meaningful auditory integration scale (IT-MAIS) and meaningful use of speech scale (MUSS) scores of all cases increased with hearing age, and IT-MAIS scores were lower than those of normal hearing children of the same age.

CONCLUSIONS

Children with WS usually have hearing loss. In WS cases with severe sensorineural hearing loss, early cochlear implantation can achieve better hearing and speech development.

Waardenburg syndrome type 2A in a large Iranian family with a novel MITF gene mutation

BACKGROUND

The characteristics of Waardenburg syndrome (WS) as a scarce heritable disorder are sensorineural hearing loss and deficits of pigmentation in the skin, hair, and eye. Here, clinical features and detection of the mutation in the MITF gene of WS2 patients are reported in a sizable Iranian family.

METHODS

A man aged 28-years represented with symptoms of mild unilateral hearing loss (right ear), complete heterochromia iridis, premature graying prior to 30 years of age, and synophrys. In this research, there was a sizable family in Iran comprising three generations with seven WS patients and two healthy members. Whole exome sequencing was applied for proband for the identification of the candidate genetic mutations associated with the disease. The detected mutation in proband and investigated family members was validated by PCR-Sanger sequencing.

RESULTS

A novel heterozygous mutation, NM_198159.3:c.1026dup p.(Asn343Glufs*27), in exon 9 of the MITF gene co-segregated with WS2 in the affected family members. The variant was forecasted as a disease-causing variant by the Mutation Taster. According to the UniProt database, this variant has been located in basic helix-loop-helix (bHLH) domain of the protein with critical role in DNA binding.

CONCLUSIONS

A frameshift was caused by a nucleotide insertion, c.1026dup, in exon 9 of the MITF gene. This mutation is able to induce an early termination, resulting in forming a truncated protein capable of affecting the normal function of the MITF protein. Helpful information is provided through an exactly described mutations involved in WS to clarify the molecular cause of clinical characteristics of WS and have a contribution to better genetic counseling of WS patients.

A Model of Waardenburg Syndrome Using Patient-Derived iPSCs With a SOX10 Mutation Displays Compromised Maturation and Function of the Neural Crest That Involves Inner Ear Development

Waardenburg syndrome (WS) is an autosomal dominant inherited disorder that is characterized by sensorineural hearing loss and abnormal pigmentation. SOX10 is one of its main pathogenicity genes. The generation of patient-specific induced pluripotent stem cells (iPSCs) is an efficient means to investigate the mechanisms of inherited human disease. In our work, we set up an iPSC line derived from a WS patient with SOX10 mutation and differentiated into neural crest cells (NCCs), a key cell type involved in inner ear development. Compared with control-derived iPSCs, the SOX10 mutant iPSCs showed significantly decreased efficiency of development and differentiation potential at the stage of NCCs. After that, we carried out high-throughput RNA-seq and evaluated the transcriptional misregulation at every stage. Transcriptome analysis of differentiated NCCs showed widespread gene expression alterations, and the differentially expressed genes (DEGs) were enriched in gene ontology terms of neuron migration, skeletal system development, and multicellular organism development, indicating that SOX10 has a pivotal part in the differentiation of NCCs. It's worth noting that, a significant enrichment among the nominal DEGs for genes implicated in inner ear development was found, as well as several genes connected to the inner ear morphogenesis. Based on the protein-protein interaction network, we chose four candidate genes that could be regulated by SOX10 in inner ear development, namely, BMP2, LGR5, GBX2, and GATA3. In conclusion, SOX10 deficiency in this WS subject had a significant impact on the gene expression patterns throughout NCC development in the iPSC model. The DEGs most significantly enriched in inner ear development and morphogenesis may assist in identifying the underlying basis for the inner ear malformation in subjects with WS.

Clinical manifestations and novel pathogenic variants in SOX10 in eight Danish probands with Waardenburg syndrome

The SRY-related HMG box gene 10 (SOX10), located on 22q13.1, encodes a member of the SOX family of transcription factors involved in the regulation of embryonic development and in the determination of cell fate and differentiation. SOX10 is one of the six causal genes for Waardenburg syndrome, which is a dominantly inherited auditory-pigmentary disorder characterized by sensorineural hearing impairment and abnormal pigmentation of the hair, skin and iris. Waardenburg syndrome is categorized into four subtypes based on clinical features (WS1-WS4). Here we present eight families (eleven patients) harboring pathogenic variants in SOX10. The patients displayed both allelic and clinical variability: bilateral profound hearing impairment (11/11), malformations of the semicircular canals (5/11), motor skill developmental delay (5/11), pigmentary defects (3/11) and Hirschsprung's disease (3/11) were some of the clinical manifestations observed. The patients demonstrate a spectrum of pathogenic SOX10 variants, of which six were novel (c.267del, c.299_300insA, c.335T >C, c.366_376del, c.1160_1179dup, and exon 3-4 deletion), and two were previously reported (c.336G>A and c.422T>C). Six of the variants occurred de novo whereas two were dominantly inherited. The pathogenic SOX10 variants presented here add novel information to the allelic variability of Waardenburg syndrome and illustrate the considerable clinical heterogeneity.

Corpus callosotomy for drug-resistant epilepsy in a pediatric patient with Waardenburg syndrome Type I

Background:

Waardenburg syndrome (WS) is caused by autosomal dominant mutations. Since the coexistence of epilepsy and WS type I is rare, the detailed clinical features and treatment of epilepsy, including surgery, have not been fully reported for these patients. We report the first case of an individual with WS type I, who underwent corpus callosotomy (CC) for drug-resistant epilepsy and obtained good seizure outcomes.

Case Description:

A boy was diagnosed as having WS type I and developmental delay based on characteristic symptoms and a family history of hearing loss. He underwent cochlear implantation at 18 months of age. At 4 years of age, he developed epileptic seizures with a semiology of drop attack. Electroencephalography (EEG) showed bilateral synchronous high-amplitude spikes and wave bursts, dominant in the right hemisphere. Based on the multimodality examinations, we considered that ictal discharges propagated from the entire right hemisphere to the left, resulting in synchronous discharge and a clinical drop attack; therefore, CC was indicated. At 9 years of age, he underwent a front 2/3^rd CC. At 1 year, the patient became seizure free, and interictal EEG showed less frequent and lower amplitude spike and wave bursts than before.

Conclusion:

When patients with WS Type I and cognitive impairment show drug-resistant epilepsy, clinicians should consider a presurgical evaluation.

Four mutations in MITF, SOX10 and PAX3 genes were identified as genetic causes of waardenburg syndrome in four unrelated Iranian patients: case report

Background

Waardenburg syndrome (WS) is a rare genetic disorder. The purpose of this study was to investigate clinical and molecular characteristics of WS in four probands from four different Iranian families.

Case presentation

The first patient was a 1-year-old symptomatic boy with congenital hearing loss and heterochromia iridis with a blue segment in his left iris. The second case was a 1.5-year-old symptomatic girl who manifested congenital profound hearing loss, brilliant blue eyes, and skin hypopigmentation on the abdominal region at birth time. The third patient was an 8-month-old symptomatic boy with developmental delay, mild atrophy, hypotonia, brilliant blue eyes, skin hypopigmentation on her hand and foot, Hirschsprung disease, and congenital profound hearing loss; the fourth patient was a 4-year-old symptomatic boy who showed dystopia canthorum, broad nasal root, synophrys, skin hypopigmentation on her hand and abdomen, brilliant blue eyes, and congenital profound hearing loss. Whole exome sequencing (WES) was used for each proband to identify the underlying genetic factor. Sanger sequencing was performed for validation of the identified mutations in probands and the available family members. A novel heterozygous frameshift mutation, c.996delT (p.K334Sfs*15), on exon 8 of the MITF gene was identified in the patient of the first family diagnosed with WS2A. Two novel de novo heterozygous mutations including a missense mutation, c.950G > A (p.R317K), on exon 8 of the MITF gene, and a frameshift mutation, c.684delC (p.E229Sfs*57), on the exon 3 of the SOX10 gene were detected in patients of the second and third families with WS2A and PCWH (Peripheral demyelinating neuropathy, Central dysmyelinating leukodystrophy, Waardenburg syndrome, Hirschsprung disease), respectively. A previously reported heterozygous frameshift mutation, c.1024_1040del AGCACGATTCCTTCCAA, (p.S342Pfs*62), on exon 7 of the PAX3 gene was identified in the patient of the fourth family with WS1.

Conclusions

An exact description of the mutations responsible for WS provides useful information to explain the molecular cause of clinical features of WS and contributes to better genetic counseling of WS patients and their families.

Establishment of an iPSC line (CSUXHi003-A) from a patient with Waardenburg syndrome type Ⅱ caused by a MITF mutation

Waardenburg syndrome (WS) is a genetic disorder characterized by sensorineural deafness. It has a variable presentation of pigmentation defects. Here, we generated an induced pluripotent stem cell (iPSC) line using episomal plasmid vectors from the fibroblasts of a 4-year-old boy affected with WS type II, caused by a novel mutation in microphthalmia-associated transcription factor (MITF) (NM_000248.3: exon6:c.626A>T). The patient-specific iPSC line (CSUXHi003-A) carrying the same MITF mutation showed normal karyotype, expressed pluripotent markers, and presented differentiation capacity in vitro. It may be a useful tool for in vitro modeling of WS.

Novel SOX10 Mutations in Waardenburg Syndrome: Functional Characterization and Genotype-Phenotype Analysis

Waardenburg syndrome (WS) is a prevalent hearing loss syndrome, concomitant with focal skin pigmentation abnormalities, blue iris, and other abnormalities of neural crest-derived cells, including Hirschsprung’s disease. WS is clinically and genetically heterogeneous and it is classified into four major types WS type I, II, III, and IV (WS1, WS2, WS3, and WS4). WS1 and WS3 have the presence of dystopia canthorum, while WS3 also has upper limb anomalies. WS2 and WS4 do not have the dystopia canthorum, but the presence of Hirschsprung’s disease indicates WS4. There is a more severe subtype of WS4 with peripheral nerve and/or central nervous system involvement, namely peripheral demyelinating neuropathy, central dysmyelinating leukodystrophy, WS, and Hirschsprung’s disease or PCW/PCWH. We characterized the genetic defects underlying WS2, WS4, and the WS4-PCW/PCWH) using Sanger and whole-exome sequencing and cytogenomic microarray in seven patients from six unrelated families, including two with WS2 and five with WS4. We also performed multiple functional studies and analyzed genotype–phenotype correlations. The cohort included a relatively high frequency (80%) of individuals with neurological variants of WS4. Six novel SOX10 mutations were identified, including c.89C > A (p.Ser30^∗), c.207_8 delCG (p.Cys71Hisfs^∗62), c.479T > C (p.Leu160Pro), c.1379 delA (p.Tyr460Leufs^∗42), c.425G > C (p.Trp142Ser), and a 20-nucleotide insertion, c.1155_1174dupGCCCCACTATGGCTCAGCCT (p.Phe392Cysfs^∗117). All pathogenic variants were de novo. The results of reporter assays, western blotting, immunofluorescence, and molecular modeling supported the deleterious effects of the identified mutations and their correlations with phenotypic severity. The prediction of genotype–phenotype correlation and functional pathology, and dominant negative effect vs. haploinsufficiency in SOX10-related WS were influenced not only by site (first two vs. last coding exons) and type of mutation (missense vs. truncation/frameshift), but also by the protein expression level, molecular weight, and amino acid content of the altered protein. This in vitro analysis of SOX10 mutations thus provides a deeper understanding of the mechanisms resulting in specific WS subtypes and allows better prediction of the phenotypic manifestations, though it may not be always applicable to in vivo findings without further investigations.

Targeted next-generation sequencing identified a novel variant of SOX10 in a Chinese family with Waardenburg syndrome type 2

Objective

Waardenburg syndrome type 2 (WS2) is an autosomal dominant syndrome, characterized by bright blue eyes, hearing loss, and depigmented patches of hair and skin. It exhibits high phenotypic and genetic heterogeneity. We explored the molecular etiology in a Chinese family with WS2.

Methods

We recruited a three-generation family with three affected members. Medical history was obtained from all family members who underwent detailed physical examinations and audiology tests. Genomic DNA was extracted from peripheral blood of each individual, and 139 candidate genes associated with hearing loss were sequenced using Illumina HiSeq 2000 (Illumina Inc., San Diego, CA, USA) and verified by Sanger sequencing.

Results

Genetic evaluation revealed a novel nonsense heterozygous variant, NM_006941.4: c.342G>A (p.Trp114Ter) in exon 2 of the SOX10 gene in the three affected patients; no unaffected family member carried the variation. We did not detect the variation in 500 Chinese individuals with normal hearing or in 122 unrelated Chinese families with hearing loss, suggesting that it was specific to our patients.

Conclusions

We identified a novel heterozygous nonsense variation in a family with syndromic hearing loss and WS2. Our findings expand the pathogenic spectrum and strengthen the clinical diagnostic role of SOX10 in patients with WS2.

Waardenburg Syndrome Type-II in Twin Siblings: An Unusual Audio-Pigmentary Disorder

Waardenburg syndrome (WS) is an interesting inherited audio-pigmentary disorder. The syndrome shows no gender, racial, or ethnic predilection. This unique disorder is characterized by pigmentary abnormalities, deafness, and neural crest-derived tissue defect. WS can be recognized by some specific clinical features that appear after birth; not all affected individuals possess all the clinical features. It has four clinical sub types based on the mutant gene and characteristic morphology. These morphological features are broad nasal root, white forelock, the difference in the colour of eyes, congenital leukoderma, and sensorineural deafness. We report an interesting case of WS in twin boys who fulfill the criteria of WS-II. Our cases have four major criteria (white forelock, heterochromia, sensorineural hearing loss, first degree relative with WS), and 1 minor criterion to establish the diagnosis of WS-II. Most clinical features of WS-II except sensorineural deafness are benign and do not need any intervention but severe deafness can be a serious problem. The current report is unique and is a rare case of WS in twin infants. We present this case for its rarity, relative paucity of literature, and also to emphasize the clinical presentation of this extremely rare disease in twins.

Ophthalmological features and treatments in five cases of Waardenburg syndrome

The present study aimed to investigate the ocular characteristics and treatment of Waardenburg syndrome (WS). A total of five patients with Waardenburg syndrome from our hospital, aged between 1 and 8 years, were included in the present study. The clinical data of these patients were analyzed, and the ocular manifestations and treatments were described. The general manifestations included hearing loss (1/5), broad high nasal root (2/5) and hypoplasia of alae nasi (2/5). Ophthalmological evaluations revealed ptosis (1/5), strabismus 1 (1/5), synophrys (2/5), telecanthus (5/5), iris hypopigmentation (5/5), high intraocular pressure (1/5) and choroidal hypopigmentation (1/5). For patients with characteristic external eye abnormalities, including ptosis, ocular plastic surgery was performed. For patients with only symptoms of iris heterochromia, no special treatment was required. The findings from the present study suggest that patients with WS may have several characteristic ocular manifestations. Abnormalities in the eyelid can be corrected by ocular plastic surgery, which is beneficial to children's physical and mental development.

MITF Is Mutated in Type 1 Waardenburg Syndrome With Unusual Phenotype

BACKGROUND

Waardenburg syndrome (WS) is a rare disorder characterized by varying combinations of sensorineural hearing loss and abnormal pigmentation of the hair and skin. WS is classified into four subtypes (WS1-WS4) based on additional symptoms. Dystopia canthorum is a hallmark of WS type 1. There are two genes linked to WS type 1, including PAX3 and EDNRB.

OBJECTIVE

This study aimed to investigate the genetic etiology of WS type 1 in a pair of twins from China with profound hearing loss, blond hair and eyebrows, dystopia canthorum, and brown irides.

METHODS

The target capture sequencing and Whole-exome sequencing were performed to detect mutations in WS-related genes.

RESULTS

A novel de novo frameshift mutation, p.L341Rfs*18 in MITF was identified in the twins. Hearing thresholds showed substantial improvements following cochlear implantation with a pure-tone average of 30 dB in free-field conditions.

CONCLUSIONS

The study showed the new genotype-phenotype correlations of MITF to WS type 1. Further molecular analysis is necessary to reappraise the current classification on WS.

A rare case of Waardenburg syndrome with unilateral hearing loss caused by nonsense variant c.772C>T (p.Arg259*) in the MITF gene in Yakut patient from the Eastern Siberia (Sakha Republic, Russia)

Waardenburg syndrome (WS) is an orphan genetic disease with autosomal dominant pattern of inheritance characterised by varying degrees of hearing loss accompanied by skin, hair and iris pigmentation abnormalities. Four types of WS differing in phenotypic characteristics are now described. We performed a Sanger sequencing of coding regions of genes PAX3, MITF, SOX10 and SNAI2 in the patient with WS from a Yakut family living in the Sakha Republic. No changes were found in the PAX3, SOX10 and SNAI2 coding regions while a previously reported heterozygous transition c.772C>T (p.Arg259*) in exon 8 of the MITF gene was found in this patient. This patient presents rare phenotype of WS type 2: congenital unilateral hearing loss, unilateral heterochromia of irises, and absence of skin/hair depigmentation and dystopia canthorum. Audiological variability in WS type 2, caused by the c.772C>T (p.Arg259*) variant in the MITF gene, outlines the importance of molecular analysis and careful genotype-phenotype comparisons in order to optimally inform patients about the risk of hearing loss. The results of this study confirm the association of pathogenic variants in the MITF gene with WS type 2 and expanded data on the variability of audiological features of the WS.

[Screening for ocular involvement in deaf children]

L'association de la surdité aux troubles visuels est fréquente. Ces troubles vont de simple anomalie de la réfraction jusqu'à la maladie grave qui peut constituer un handicap. D'où l'intérêt d'un dépistage précoce. L'objectif de cette étude est de montrer l'importance de la collaboration multidisciplinaire et la nécessité de l'examen ophtalmologique chez chaque enfant présentant une surdité à travers cette étude prospective. Il s'agit d'une étude prospective monocentrique colligeant 200 enfants suivis pour hypoacousie de janvier 2014 à janvier 2015. Chaque enfant a bénéficié d'un examen ophtalmologique complet; examen ORL; et un examen général. Cent cinquante-cinq dossiers ont été colligés. Une atteinte oculaire était constatée chez 47 patients soit 30,4% des enfants. Elle est bilatérale chez 45patients. Les principales étiologies étaient syndromiques (syndrome d'Usher (8cas), syndrome de Waardenbourg (5 cas), syndrome d'Alport (3 cas), syndrome de Wolfram (2 cas), syndrome de Goldenar (3 cas), syndrome de Cogan (3 cas), syndrome de Fracheschetti (1 cas), syndrome de Charge (1 cas), syndrome otomandibulaire (1 cas), syndrome de Stickler (1 cas), syndrome d'Alstrom (1 cas), syndrome de Refsum (1 cas), syndrome de Susac (1 cas) et KID syndrome (1 cas)). Le dépistage de l'atteinte oculaire a permis de raccourcir le délai d'attente pour implant cochléaire de 9 mois à 3 mois. Les atteintes oculo auditives sont très nombreuses du fait de la similitude embryologique et cellulaire de ces deux organes, notamment la rétine et l'oreille interne. Le diagnostic de ces atteintes est facilité par l'existence d'une dysmorphie faciale, en revanche, il reste difficile lorsqu'il existe que les atteintes neurosensorielles visuelles et auditives. La précocité du diagnostic des atteintes oculo auditives permet un meilleur développement psychomoteur et une insertion sociale optimale. Donc la prise en charge pluridisciplinaire précoce est nécessaire afin de permettre la meilleure rééducation psychomotrice, orthophonique et visuelle.

Expert specification of the ACMG/AMP variant interpretation guidelines for genetic hearing loss

Due to the high genetic heterogeneity of hearing loss (HL), current clinical testing includes sequencing large numbers of genes, which often yields a significant number of novel variants. Therefore, the standardization of variant interpretation is crucial to provide consistent and accurate diagnoses. The Hearing Loss Variant Curation Expert Panel was created within the Clinical Genome Resource to provide expert guidance for standardized genomic interpretation in the context of HL. As one of its major tasks, our Expert Panel has adapted the American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) guidelines for the interpretation of sequence variants in HL genes. Here, we provide a comprehensive illustration of the newly specified ACMG/AMP HL rules. Three rules remained unchanged, four rules were removed, and the remaining 21 rules were specified. These rules were further validated and refined using a pilot set of 51 variants assessed by curators and disease experts. Of the 51 variants evaluated in the pilot, 37% (19/51) changed category based upon application of the expert panel specified rules and/or aggregation of evidence across laboratories. These HL-specific ACMG/AMP rules will help standardize variant interpretation, ultimately leading to better care for individuals with HL.

New Genotypes and Phenotypes in Patients with 3 Subtypes of Waardenburg Syndrome Identified by Diagnostic Next-Generation Sequencing

Background

Waardenburg syndrome (WS) is one of the most common forms of syndromic deafness with heterogeneity of loci and alleles and variable expressivity of clinical features.

Methods

The technology of single-nucleotide variants (SNV) and copy number variation (CNV) detection was developed to investigate the genotype spectrum of WS in a Chinese population.

Results

Ninety WS patients and 24 additional family members were recruited for the study. Fourteen mutations had not been previously reported, including c.808C>G, c.117C>A, c.152T>G, c.803G>T, c.793-3T >G, and c.801delT on PAX3; c.642_650delAAG on MITF; c.122G>T and c.127C>T on SOX10; c.230C>G and c.365C>T on SNAI2; and c.481A>G, c.1018C>G, and c.1015C>T on EDNRB. Three CNVs were de novo and first reported in our study. Five EDNRB variants were associated with WS type 1 in the heterozygous state for the first time, with a detection rate of 22.2%. Freckles occur only in WS type 2. Yellow hair, amblyopia, congenital ptosis, narrow palpebral fissures, and pigmentation spots are rare and unique symptoms in WS patients from China.

Conclusions

EDNRB should be considered as another prevalent pathogenic gene in WS type 1. Our study expanded the genotype and phenotype spectrum of WS, and diagnostic next-generation sequencing is promising for WS.

A non-coding regulatory variant in the 5'-region of the MITF gene is associated with white-spotted coat in Brown Swiss cattle

Recently, the Swiss breeding association reported an increasing number of white-spotted cattle in the Brown Swiss breed, which is normally solid brown coloured. A total of 60 Brown Swiss cattle with variably sized white abdominal spots, facial markings and depigmented claws were collected for this study. A genome-wide association study using 40k SNP genotypes of 20 cases and 1619 controls enabled us to identify an associated genome region on chromosome 22 containing the MITF gene, encoding the melanogenesis associated transcription factor. Variants at the MITF locus have been reported before to be associated with white or white-spotted phenotypes in other species such as horses, dogs and mice. Whole-genome sequencing of a single white-spotted cow and subsequent genotyping of 172 Brown Swiss cattle revealed two significantly associated completely linked single nucleotide variants (rs722765315 and rs719139527). Both variants are located in the 5'-regulatory region of the bovine MITF gene, and comparative sequence analysis showed that the variant rs722765315, located 139 kb upstream of the transcription start site of the bovine melanocyte-specific MITF transcript, is situated in a multi-species conserved sequence element which is supposed to be regulatory important. Therefore, we hypothesize that rs722765315 represents the most likely causative variant for the white-spotting phenotype observed in Brown Swiss cattle. Presence of the mutant allele in a heterozygous or homozygous state supports a dominant mode of inheritance with incomplete penetrance and results in a variable extent of coat colour depigmentation.

A novel PAX3 mutation in a Korean patient with Waardenburg syndrome type 1 and unilateral branch retinal vein and artery occlusion: a case report

Background

Waardenburg syndrome (WS) is a very rare genetic disorder affecting the neural crest cells. Coexistence of branch retinal vein occlusion (BRVO) and branch retinal artery occlusion (BRAO) in the same eye is also a rare finding. Here we report a case of WS type 1 that was confirmed by a novel mutation with the finding of unilateral BRVO and BRAO.

Case presentation

A 36-year-old, white-haired Korean man presented with a complaint of loss of vision in the inferior visual field of his right eye and hearing loss. He had telecanthus with a medial eyebrow and a hypochromic left iris. Funduscopy showed an ischemic change at the posterior pole in the right eye with sparing of the foveal center as well as retinal hemorrhages and white patches along the superotemporal arcade. Fundus angiography revealed the presence of both BRVO and BRAO, and optical coherence tomography showed thickening and opacification of the retinal layers corresponding to the ischemic area. A blood workup revealed hyperhomocysteinemia and the presence of antiphospholipid antibodies; both are suggestive as the cause of the BRVO and BRAO. Single nucleotide polymorphism analysis confirmed a novel PAX3 mutation at 2q35 (c.91–95 ACTCC deletion causing a frameshift). These findings confirmed a diagnosis of WS type 1.

Conclusions

WS is a heterogeneous inherited disorder of the neural crest cells that causes pigment abnormalities and sensorineural hearing loss. This is the first report of unilateral BRVO and BRAO in a patient with WS. Furthermore, the PAX3 mutation identified in this patient has not been reported previously.

First report of Klein-Waardenburg Syndrome in Iran and a novel pathogenic splice site variant in PAX3 gene

OBJECTIVES

Waardenburg Syndrome (WS) as a congenital auditory-pigmentary syndrome is a clinically and genetically heterogeneous disorder. Based upon clinical manifestations, it can be classified into four types. Loss of function mutations in PAX3 gene cause WS1 and WS3 (Klein-Waardenburg syndrome). While WS2 and WS4 have locus heterogeneity with multiple causative genes. Here we report a novel splice site variant in a pedigree with multiple affected members. Based on diagnostic criteria, three of them are associated with WS3. The remained patients classified as type 1.

METHODS

PCR amplification and Sanger sequencing were performed for all exons and all exon-intron boundaries of PAX3 (NM_181,459) gene of the proband. Then available symptomatic and asymptomatic members were screened for the detected variant. Interpretation and classification of the variant were done based on the current guidelines.

RESULTS

We identified a novel heterozygous splice site variant (c.586+2T > C) in donor site of intron 4 of PAX3 gene in our proband. Moreover, this variant was co-segregated with the disease in other available five affected members. Also, the detected variant was not detected in any of the investigated asymptomatic members. This variant was classified as a pathogenic variant.

CONCLUSIONS

This study shows significant intra-familial clinical heterogeneity and absence of phenotype-genotype correlation in a pedigree with Waardenburg Syndrome. However, severity of phenotypes and additional symptoms in the patients can be related to alternative splicing and different levels of PAX3 gene expression. Detailed evaluation of more cases can shed light on this and case-reports are valuable traffic sign in the road. This article is the first report of Waardenburg syndrome type 3 in Iran.

Neurocristopathies: New insights 150 years after the neural crest discovery

The neural crest (NC) is a transient, multipotent and migratory cell population that generates an astonishingly diverse array of cell types during vertebrate development. These cells, which originate from the ectoderm in a region lateral to the neural plate in the neural fold, give rise to neurons, glia, melanocytes, chondrocytes, smooth muscle cells, odontoblasts and neuroendocrine cells, among others. Neurocristopathies (NCP) are a class of pathologies occurring in vertebrates, especially in humans that result from the abnormal specification, migration, differentiation or death of neural crest cells during embryonic development. Various pigment, skin, thyroid and hearing disorders, craniofacial and heart abnormalities, malfunctions of the digestive tract and tumors can also be considered as neurocristopathies. In this review we revisit the current classification and propose a new way to classify NCP based on the embryonic origin of the affected tissues, on recent findings regarding the molecular mechanisms that drive NC formation, and on the increased complexity of current molecular embryology techniques.

A Comprehensive Genetic and Clinical Evaluation of Waardenburg Syndrome Type II in a Set of Iranian Patients

Waardenburg syndrome (WS) is a neurocristopathy with an autosomal dominant mode of inheritance, and considerable clinical and genetic heterogeneity. WS type II is the most common type of WS in many populations presenting with sensorineural hearing impairment, heterochromia iridis, hypoplastic blue eye, and pigmentary abnormalities of the hair and skin. To date, mutations of MITF, SOX10, and SNAI2 have been implicated in the pathogenesis of WS2. Although different pathogenic mutations have been reported in many ethnic groups, the data on Iranian WS2 patients is insufficient. 31 WS2 patients, including 22 men and 9 women from 14 families were included. Waardenburg consortium guidelines were employed for WS2 diagnosis. WS2 patients underwent screening for MITF, SOX10, and SNAI2 mutations using direct sequencing and MLPA analysis. Clinical evaluation revealed prominent phenotypic variability in Iranian WS2 patients. Sensorineural hearing impairment and heterochromia iridis were the most common features (67% and 45%, respectively), whereas anosmia was the least frequent phenotype. Molecular analysis revealed a de novo heterozygous c.640C>T (p.R214X) in MITF and a de novo heterozygous SOX10 gross deletion in the study population. Our data help illuminate the phenotypic and genotypic spectrum of WS2 in an Iranian series of patients, and could have implications for the genetic counseling of WS in Iran.

Syndromic Hearing Loss: A Brief Review of Common Presentations and Genetics

Congenital hearing loss is one of the most common birth defects worldwide, with around 1 in 500 people experiencing some form of severe hearing loss. While over 400 different syndromes involving hearing loss have been described, it is important to be familiar with a wide range of syndromes involving hearing loss so an early diagnosis can be made and early intervention can be pursued to maximize functional hearing and speech-language development in the setting of verbal communication. This review aims to describe the presentation and genetics for some of the most frequently occurring syndromes involving hearing loss, including neurofibromatosis type 2, branchio-oto-renal syndrome, Treacher Collins syndrome, Stickler syndrome, Waardenburg syndrome, Pendred syndrome, Jervell and Lange-Nielsen syndrome, Usher syndromes, Refsum disease, Alport syndrome, MELAS, and MERRF.

Germinal mosaicism of PAX3 mutation caused Waardenburg syndrome type I

OBJECTIVES

Waardenburg syndrome mutations are most often recurrent or de novo. The rate of familial recurrence is low and families with several affected children are extremely rare. In this study, we aimed to clarify the underlying hereditary cause of Waardenburg syndrome type I in two siblings in a Chinese family, with a mother affected by prelingual mild hearing loss and a father who was negative for clinical symptoms of Waardenburg syndrome and had a normal hearing threshold.

METHODS

Complete characteristic features of the family members were recorded and genetic sequencing and parent-child relationship analyses were performed.

RESULTS

The two probands were found to share double mutations in the PAX3/GJB2 genes that caused concurrent hearing loss in Waardenburg syndrome type I. Their mother carried the GJB2 c.109G > A homozygous mutation; however, neither the novel PAX3 c.592delG mutation, nor the Waardenburg syndrome phenotype, was observed in either parent.

CONCLUSION

These previously unreported digenic mutations in PAX3/GJB2 resulted in deafness associated with Waardenburg syndrome type I in this family. To our knowledge, this is the first report describing germinal mosaicism in Waardenburg syndrome. This concept is important because it complicates genetic counseling of this family regarding the risk of recurrence of the mutations in subsequent pregnancies.

Creation of miniature pig model of human Waardenburg syndrome type 2A by ENU mutagenesis

Human Waardenburg syndrome 2A (WS2A) is a dominant hearing loss (HL) syndrome caused by mutations in the microphthalmia-associated transcription factor (MITF) gene. In mouse models with MITF mutations, WS2A is transmitted in a recessive pattern, which limits the study of hearing loss (HL) pathology. In the current study, we performed ENU (ethylnitrosourea) mutagenesis that resulted in substituting a conserved lysine with a serine (p. L247S) in the DNA-binding domain of the MITF gene to generate a novel miniature pig model of WS2A. The heterozygous mutant pig (MITF ^+/L247S) exhibits a dominant form of profound HL and hypopigmentation in skin, hair, and iris, accompanied by degeneration of stria vascularis (SV), fused hair cells, and the absence of endocochlear potential, which indicate the pathology of human WS2A. Besides hypopigmentation and bilateral HL, the homozygous mutant pig (MITF ^L247S/L247S) and CRISPR/Cas9-mediated MITF bi-allelic knockout pigs both exhibited anophthalmia. Three WS2 patients carrying MITF mutations adjacent to the corresponding region were also identified. The pig models resemble the clinical symptom and molecular pathology of human WS2A patients perfectly, which will provide new clues for better understanding the etiology and development of novel treatment strategies for human HL.

Identification of a Novel De Novo Heterozygous Deletion in the SOX10 Gene in Waardenburg Syndrome Type II Using Next-Generation Sequencing

OBJECTIVES

Waardenburg syndrome (WS) is a rare autosomal dominant disorder associated with pigmentation abnormalities and sensorineural hearing loss. In this study, we investigated the genetic cause of WSII in a patient and evaluated the reliability of the targeted next-generation exome sequencing method for the genetic diagnosis of WS.

METHODS

Clinical evaluations were conducted on the patient and targeted next-generation sequencing (NGS) was used to identify the candidate genes responsible for WSII. Multiplex ligation-dependent probe amplification (MLPA) and real-time quantitative polymerase chain reaction (qPCR) were performed to confirm the targeted NGS results.

RESULTS

Targeted NGS detected the entire deletion of the coding sequence (CDS) of the SOX10 gene in the WSII patient. MLPA results indicated that all exons of the SOX10 heterozygous deletion were detected; no aberrant copy number in the PAX3 and microphthalmia-associated transcription factor (MITF) genes was found. Real-time qPCR results identified the mutation as a de novo heterozygous deletion.

CONCLUSIONS

This is the first report of using a targeted NGS method for WS candidate gene sequencing; its accuracy was verified by using the MLPA and qPCR methods. Our research provides a valuable method for the genetic diagnosis of WS.

A Novel Pathogenic Variant in the MITF Gene Segregating with a Unique Spectrum of Ocular Findings in an Extended Iranian Waardenburg Syndrome Kindred

Waardenburg syndrome (WS) is a rare genetic disorder characterized by abnormal pigmentation of the hair, skin, and iris as well as sensorineural hearing loss. WS is subdivided into 4 major types (WS1-4), where WS2 is characterized by the absence of dystopia canthorum. This study was launched to investigate clinical and molecular characteristics of WS in an extended Iranian WS2 family. A comprehensive clinical investigation was performed. Peripheral blood samples were collected and genomic DNA was extracted. Affected members of the family were studied for possible mutations within the SOX10, MITF, and SNAI2 genes. Six WS2 individuals affected from a large Iranian WS2 kindred were enrolled. All affected members carried the novel substitution c.877C>T at exon 9 in the MITF gene, which resulted in p.Arg293* at the protein level. None of the healthy members and also of 50 ethnically matched controls had this variant. In addition, a spectrum of unique ocular findings, including nystagmus, chorioretinal degeneration, optic disc hypoplasia, astigmatism, and myopia, was segregated with the mutant allele in the pedigree. Our data provide insight into the genotypic and phenotypic spectrum of WS2 in an Iranian family and could further expand the spectrum of MITF mutations and have implications for genetic counseling on WS in Iran.

EDNRB mutations cause Waardenburg syndrome type II in the heterozygous state

Waardenburg syndrome (WS) is a genetic disorder characterized by sensorineural hearing loss and pigmentation anomalies. The clinical definition of four WS types is based on additional features due to defects in structures mostly arising from the neural crest, with type I and type II being the most frequent. While type I is tightly associated to PAX3 mutations, WS type II (WS2) remains partly enigmatic with mutations in known genes (MITF, SOX10) accounting for only 30% of the cases. We performed exome sequencing in a WS2 index case and identified a heterozygous missense variation in EDNRB. Interestingly, homozygous (and very rare heterozygous) EDNRB mutations are already described in type IV WS (i.e., in association with Hirschsprung disease [HD]) and heterozygous mutations in isolated HD. Screening of a WS2 cohort led to the identification of an overall of six heterozygous EDNRB variations. Clinical phenotypes, pedigrees and molecular segregation investigations unraveled a dominant mode of inheritance with incomplete penetrance. In parallel, cellular and functional studies showed that each of the mutations impairs the subcellular localization of the receptor or induces a defective downstream signaling pathway. Based on our results, we now estimate EDNRB mutations to be responsible for 5%-6% of WS2.

Variations in Multiple Syndromic Deafness Genes Mimic Non-syndromic Hearing Loss

The genetics of both syndromic (SHL) and non-syndromic hearing loss (NSHL) is characterized by a high degree of genetic heterogeneity. We analyzed whole exome sequencing data of 102 unrelated probands with apparently NSHL without a causative variant in known NSHL genes. We detected five causative variants in different SHL genes (SOX10, MITF, PTPN11, CHD7, and KMT2D) in five (4.9%) probands. Clinical re-evaluation of these probands shows that some of them have subtle syndromic findings, while none of them meets clinical criteria for the diagnosis of the associated syndrome (Waardenburg (SOX10 and MITF), Kallmann (CHD7 and SOX10), Noonan/LEOPARD (PTPN11), CHARGE (CHD7), or Kabuki (KMT2D). This study demonstrates that individuals who are evaluated for NSHL can have pathogenic variants in SHL genes that are not usually considered for etiologic studies.

Waardenburg syndrome type II in a Chinese patient caused by a novel nonsense mutation in the SOX10 gene

OBJECTIVE

Waardenburg syndrome is a congenital genetic disorder. It is the most common type of syndromic hearing impairment with highly genetic heterogeneity and proved to be related by 6 genes as follows: PAX3, MITF, SNAI2, EDN3, EDNRB and SOX10. This article aims to identify the genetic causes of a Chinese WS child patient.

METHODS

A Chinese WS child was collected for clinical data collection by questionnaire survey. DNA samples of proband and his parents were extracted from peripheral blood samples. Six candidate genes were sequenced by the Trusight One sequencing panel on the illumina NextSeq 500 platform.

RESULTS

A novel nonsense heterozygous mutation was found in the coding region of exon 2 in the SOX10 gene of proband. The novel nonsense heterozygous mutation could cause the replacement of the 55th lysine codon by stop codon (484T > C, C142R) and further more possibly cause terminating the protein translation in advance. However, both proband's parents had no mutation of genes above mentioned.

CONCLUSION

The gene mutation of SOX10 [NM_006941.3 c.163A > T] is a novel nonsense mutation. No record of this mutation has been found in dbSNP, HGMD, 1000 Genomes Project, ClinVar and ESP6500 databases. It meets the condition of PS2 of strong evidence in 2015 ACMG Standards and Guidelines.

Application of a New Genetic Deafness Microarray for Detecting Mutations in the Deaf in China

Objective

The aim of this study was to evaluate the GoldenGate microarray as a diagnostic tool and to elucidate the contribution of the genes on this array to the development of both nonsyndromic and syndromic sensorineural hearing loss in China.

Methods

We developed a microarray to detect 240 mutations underlying syndromic and nonsyndromic sensorineural hearing loss. The microarray was then used for analysis of 382 patients with nonsyndromic sensorineural hearing loss (including 15 patients with enlarged vestibular aqueduct syndrome), 21 patients with Waardenburg syndrome, and 60 unrelated controls. Subsequently, we analyzed the sensitivity, specificity, and reproducibility of this new approach after Sanger sequencing-based verification, and also determined the contribution of the genes on this array to the development of distinct hearing disorders.

Results

The sensitivity and specificity of the microarray chip were 98.73% and 98.34%, respectively. Genetic defects were identified in 61.26% of the patients with nonsyndromic sensorineural hearing loss, and 9 causative genes were identified. The molecular etiology was confirmed in 19.05% and 46.67% of the patients with Waardenburg syndrome and enlarged vestibular aqueduct syndrome, respectively.

Conclusion

Our new mutation-based microarray comprises an accurate and comprehensive genetic tool for the detection of sensorineural hearing loss. This microarray-based detection method could serve as a first-pass screening (before next-generation-sequencing screening) for deafness-causing mutations in China.

Clinical and genetic investigation of families with type II Waardenburg syndrome

The present study aimed to investigate the molecular pathology of Waardenburg syndrome type II in three families, in order to provide genetic diagnosis and hereditary counseling for family members. Relevant clinical examinations were conducted on the probands of the three pedigrees. Peripheral blood samples of the probands and related family members were collected and genomic DNA was extracted. The coding sequences of paired box 3 (PAX3), microphthalmia-associated transcription factor (MITF), sex-determining region Y-box 10 (SOX10) and snail family zinc finger 2 (SNAI2) were analyzed by polymerase chain reaction and DNA sequencing. The heterozygous mutation, c.649_651delAGA in exon 7 of the MITF gene was detected in the proband and all patients of pedigree 1; however, no pathological mutation of the relevant genes (MITF, SNAI2, SOX10 or PAX3) was detected in pedigrees 2 and 3. The heterozygous mutation c.649_651delAGA in exon 7 of the MITF gene is therefore considered the disease-causing mutation in pedigree 1. However, there are novel disease-causing genes in Waardenburg syndrome type II, which require further research.

Outcomes and benefits of pediatric cochlear implantation in children with additional disabilities: a review and report of family influences on outcomes

The number of children with hearing loss with additional disabilities receiving cochlear implantation has increased dramatically over the past decade. However, little is known about their auditory and speech and language development following implantation. The purpose of this review is to evaluate the effects of cochlear implantation on the most common genetic and developmental disorders in children with hearing loss. Benefits of cochlear implantation for children with autism spectrum disorder, developmental delay, CHARGE syndrome, cerebral palsy, learning disorders, Usher syndrome, Waardenburg syndrome, and attention deficit/hyperactivity disorder are reviewed. Our review indicates that children with hearing loss and additional disabilities benefit from cochlear implantation, especially when implanted early. Thus, early interventions seem as important for these children as for deaf children without additional disabilities. Comparisons of outcomes across these disabilities indicate that children with little to no cognitive impairment (eg, Waardenburg sydrome, attention deficit hyperactivity disorder) have better outcomes than those with greater deficits in intellectual functioning (eg, autism, CHARGE syndrome). In addition, parents of children with hearing loss and additional disabilities report higher levels of parenting stress and greater child behavior problems than those without comorbid diagnoses. However, these parents are as sensitive when interacting with their children as parents with typically developing children using cochlear implantation. Given these results, it is critical to evaluate these children's developmental milestones to provide early implantation and intervention, appropriately counsel families regarding realistic expectations for the implant, and facilitate family adaptation.

Genetic counseling for a three-generation Chinese family with Waardenburg syndrome type II associated with a rare SOX10 mutation

OBJECTIVE

Waardenburg syndrome is clinically and genetically heterogeneous. The SOX10 mutation related with Waardenburg syndrome type II is rare in Chinese. This study aimed to uncover the genetic causes of Waardenburg syndrome type II in a three-generation family to improve genetic counseling.

METHODS

Complete clinical and molecular evaluations were conducted in a three-generation Han Chinese family with Waardenburg syndrome type II. Targeted genetic counseling was provided to this family.

RESULTS

We identified a rare heterozygous dominant mutation c.621C>A (p.Y207X) in SOX10 gene in this family. The premature termination codon occurs in exon 4, 27 residues downstream of the carboxyl end of the high mobility group box. Bioinformatics prediction suggested this variant to be disease-causing, probably due to nonsense-mediated mRNA decay. Useful genetic counseling was given to the family for prenatal guidance.

CONCLUSION

Identification of a rare dominant heterozygous SOX10 mutation c.621C>A in this family provided an efficient way to understand the causes of Waardenburg syndrome type II and improved genetic counseling.

CHOROIDAL MELANOMA IN A PATIENT WITH WAARDENBURG SYNDROME

PURPOSE

To report a case of choroidal malignant melanoma in a patient with Waardenburg syndrome and bilateral choroidal pigmentary abnormalities.

METHODS

Clinical examination and multimodal imaging of the case.

RESULTS

A 45-year-old woman presented with asymptomatic flat choroidal pigmentation abnormalities in both eyes. A choroidal lesion was identified in the inferotemporal periphery of the left eye arising from an area of hyperpigmentation; ultrasonography findings were consistent with a choroidal melanoma. The patient endorsed a personal and family history of premature graying of hair and was identified to have dystopia canthorum consistent with the diagnosis of Waardenburg syndrome.

CONCLUSION

The authors present the first reported case of concurrent Waardenburg syndrome and choroidal malignant melanoma. This cooccurrence may suggest that the relative hyperpigmented regions in affected fundi may be abnormal and should be monitored closely for the development of choroidal melanoma.

Clinical manifestations of Waardenburg syndrome in a male adolescent in Mali, West Africa

Waardenburg syndrome (WS) is a genetic disorder of which there are four distinct types. These four types are differentiated by the physical defects which they produce. Presented here is the case of a 13-year-old boy with WS Type I who was observed and physically assessed in Mali, West Africa in 1969. His physical findings included a bright blue coloring to the irises of the eyes, profound sensorineural deafness, mutism, dystopia canthorum (lateral displacement of the inner canthi of the eyes), broad nasal root, bushy eyebrows, and scaphoid deformities of the supraorbital portions of the frontal bone. Because family members were not available for interviews or physical examinations, it was not possible to determine if this patient was suffering from a congenital form of the disorder or from a spontaneous mutation. Given the patient's then location in a remote rural area of Mali where electricity was absent, it was not possible to perform additional diagnostic tests. The patient described here is the first with WS in Mali, West Africa to have been medically observed and evaluated and later documented in the medical literature. A second case of the syndrome in Mali was described in the medical literature in 2011 in an 18-month-old infant who did not have sensorineural hearing loss, but who did have a bilateral cleft lip. An historical overview of WS is presented along with details concerning the characteristics of the four types of the disorder.