Waardenburg Syndrome Research Articles

Inner ear anatomy in Waardenburg syndrome: Radiological assessment and comparison with normative data

ObjectiveAs patients with Waardenburg syndrome (WS) represent potential candidates for cochlear implantation, their inner ear anatomy is of high significance. There is an ongoing debate whether WS is related to any inner ear dysplasias. Our objective was to evaluate radiologically the inner ear anatomy in patients with WS and identify any temporal bone malformations. MethodsA retrospective case review was carried out in a tertiary, referral center. The high resolution computed tomography (HRCT) scans of the temporal bone from 20 patients (40 ears) with WS who were managed for deafness in a tertiary referral center from 1995 to 2012 were retrospectively examined. Measurements of 15 different inner ear dimensions, involving the cochlea, the vestibule, the semicircular canals and the internal auditory meatus, as well as measurements of the vestibular aqueduct, were performed independently by two neuroradiologists. Finally, we compared the results from the WS group with a control group consisting of 50 normal hearing subjects (100 ears) and with previously reported normative values. ResultsInner ear malformations were not found in any of the patients with WS. All measured inner ear dimensions were within the normative values compiled by our study group as well as by others. ConclusionsInner ear malformations are not characteristic for all types of WS; however, certain rare subtypes might be related to inner ear deformities. Normative cochleovestibular dimensions that can help in assessing the temporal bone anatomy are provided.

Phenotypic variability in Waardenburg syndrome resulting from a 22q12.3‐q13.1 microdeletion involving SOX10

Waardenburg syndrome (WS) is a neurocristopathy characterized by pigmentation abnormalities of the skin, hair, and iris, as well as sensorineural hearing loss. Contiguous gene deletions encompassing SOX10 are rare, which limits conclusions about genotype-phenotype correlation regarding patient prognosis and management. This study adds to the existing body of knowledge by characterizing a 2.4 Mb deletion [arr[hg19] 22q12.3-q13.1 (36467502-38878207)x1] encompassing SOX10 and 53 additional RefSeq genes in a 15-year-old female with atypical WS. The patient presented with developmental delay, profound bilateral sensorineural hearing loss, heterochromia iridis, hypotonia, and bilateral finger contractures. Published genomic and phenotypic profiles of patients with SOX10-encompassing deletions point toward several plausible candidate gene that could account for the considerable clinical heterogeneity. These studies suggest the existence of modifiers among the co-deleted, dosage-sensitive genes (e.g., MYH9) and among genes whose effect may depend on the unmasking of recessive mutations (e.g., PLA2G6). Finally, we highlight evidence illustrating extensive interconnectivity of SOX10-hypothesizing that haploinsufficiency of SOX10 may "unmask" subtler effects on expression or epistasis associated with variants in SOX10 targets (e.g., DHH), in its partners (e.g., PAX3, EGR2), and in genes with functional overlap (e.g., SOX8, SOX9).

De novo dominant mutation of SOX10 gene in a Chinese family with Waardenburg syndrome type II

ObjectiveWaardenburg syndrome is a rare genetic disorder, inherited as an autosomal dominant trait. The condition is characterized by sensorineural hearing loss and pigment disturbances of the hair, skin, and iris. The de novo mutation in the SOX10 gene, responsible for Waardenburg syndrome type II, is rarely seen. The present study aimed to identify the genetic causes of Waardenburg syndrome type II in a Chinese family. MethodsClinical and molecular evaluations were conducted in a Chinese family with Waardenburg syndrome type II. ResultsA novel SOX10 heterozygous c.259-260delCT mutation was identified. Heterozygosity was not observed in the parents and sister of the proband, indicating that the mutation has arisen de novo. The novel frameshift mutation, located in exon 3 of the SOX10 gene, disrupted normal amino acid coding from Leu87, leading to premature termination at nucleotide 396 (TGA). The high mobility group domain of SOX10 was inferred to be partially impaired. ConclusionThe novel heterozygous c.259-260delCT mutation in the SOX10 gene was considered to be the cause of Waardenburg syndrome in the proband. The clinical and genetic characterization of this family would help elucidate the genetic heterogeneity of SOX10 in Waardenburg syndrome type II. Moreover, the de novo pattern expanded the mutation data of SOX10.

Chronic constipation recognized as a sign of a SOX10 mutation in a patient with Waardenburg syndrome

Waardenburg syndrome is characterized by hearing loss, pigmentation abnormalities, dysmorphologic features, and neurological phenotypes. Waardenburg syndrome consists of four distinct subtypes, and SOX10 mutations have been identified in type II and type IV. Type IV differs from type II owing to the presence of Hirschsprung disease. We identified a de novo nonsense mutation in SOX10 (p.G39X) in a female pediatric patient with Waardenburg syndrome with heterochromia iridis, profound bilateral sensorineural hearing loss, inner ear malformations, and overall hypopigmentation of the hair without dystopia canthorum. This patient has experienced chronic constipation since she was a neonate, but anorectal manometry showed a normal anorectal reflex. Chronic constipation in this patient was likely to be a consequence of a mild intestinal disorder owing to the SOX10 mutation, and this patient was considered to have a clinical phenotype intermediate between type II and type IV of the syndrome. Chronic constipation may be recognized as indicative of a SOX10 mutation in patients with Waardenburg syndrome.

Waardenburg syndrome in childhood deafness in Cameroon

Background. Waardenburg syndrome (WS) is a rare hereditary disorder essentially characterised by deafness and pigment disorders of the eyes, hair and skin. Methods. Between October 2010 and December 2011, we identified six patients with WS during an aetiological survey of 582 deaf participants recruited in schools for the deaf and ear, nose and throat outpatient clinics in seven of the ten regions of Cameroon. Two classic characteristics of WS were used as diagnostic criteria: deafness and pigmentation abnormalities (heterochromia iridis, white forelock and depigmented skin patches). In addition, to identify dystopia canthorum, a sign of WS type I, we calculated the W -index. Results. WS comprised 1% of the whole sample, 7% of the genetic cases, and 50% of the genetic syndromic cases. All patients with WS had severe to profound congenital sensorineural and symmetrical hearing loss with flat audiograms. They also had pigment disorders of the eyes and the skin. In the absence of dystopia canthorum, they were all classified as having WS type II. The pedigree was suggestive of autosomal dominant inheritance in two cases, and the four others seemed to be de novo cases. Conclusion. The results suggest that WS type II is the most common syndromic form of hearing loss among Cameroonians. This has implications for retrospective genetic counselling and hearing tests for earlier management in affected families.

Identification and functional analysis of a novel mutation in the SOX10 gene associated with Waardenburg syndrome type IV

Waardenburg syndrome type IV (WS4) is a rare genetic disorder, characterized by auditory–pigmentary abnormalities and Hirschsprung disease. Mutations of the EDNRB gene, EDN3 gene, or SOX10 gene are responsible for WS4. In the present study, we reported a case of a Chinese patient with clinical features of WS4. In addition, the three genes mentioned above were sequenced in order to identify whether mutations are responsible for the case. We revealed a novel nonsense mutation, c.1063C>T (p.Q355*), in the last coding exon of SOX10. The same mutation was not found in three unaffected family members or 100 unrelated controls. Then, the function and mechanism of the mutation were investigated in vitro. We found both wild-type (WT) and mutant SOX10 p.Q355* were detected at the expected size and their expression levels are equivalent. The mutant protein also localized in the nucleus and retained the DNA-binding activity as WT counterpart; however, it lost its transactivation capability on the MITF promoter and acted as a dominant-negative repressor impairing function of the WT SOX10.

An Impairment of Long Distance SOX10 Regulatory Elements Underlies Isolated Hirschsprung Disease

A deletion encompassing several SOX10 enhancers was recently identified in a patient presenting with Waardenburg syndrome type 4 (WS4), which is defined as a combination of Hirschsprung disease (HSCR, intestinal aganglionosis) and WS (deafness and pigmentation defects). The expression patterns of some of the known SOX10 enhancers in animal models led to the speculation that endophenotypes of WS4 may be linked to mutations within some of these sequences. The present study investigated deletions and point mutations within four SOX10 enhancers in 144 unexplained isolated HSCR cases. One deletion and two point mutations affecting binding sites for known neural crest transcription factors were identified. In vitro functional analysis revealed that the first point mutation disrupts autoregulation by SOX10, whereas the second affects AP2a and SOX10 synergistic activity. The present findings suggest that the mutations within SOX10 enhancers contribute to isolated HSCR.

Anterior ethmoidal artery emerging anterior to bulla ethmoidalis: An abnormal anatomical variation in Waardenburg's syndrome.

In endoscopic sinus surgery, the anterior ethmoidal artery (AEA) is usually identified as it traverses obliquely across the fovea ethmoidalis, posterior to the bulla ethmoidalis and anterior to or within the ground lamella's attachment to the skull base. Injury to the AEA may result in hemorrhage, retraction of the AEA into the orbit, and a retrobulbar hematoma. The resulting increase in intraorbital pressure may threaten vision. Waardenburg's syndrome (WS) is a rare congenital, autosomal dominantly inherited disorder, distinguished by characteristic facial features, pigmentation abnormalities, and profound, congenital, sensorineural hearing loss. We present a case of AEAs located anterior to the bulla ethmoidalis in a 36-year-old male with WS and chronic rhinosinusitis. The anatomic abnormality was not obvious on a preoperative computed tomography scan and was discovered intraoperatively when the left AEA was injured, resulting in a retrobulbar hematoma. The hematoma was immediately identified and decompressed endoscopically without lasting complications. The AEA on the right was identified intraoperatively and preserved. The characteristic craniofacial features in WS were probably associated with the abnormal vascular anatomy. Endoscopic sinus surgeons should be aware of these potential anatomic anomalies in patients with abnormal craniofacial development.

Waardenburg syndrome type 4: Report of two new cases caused by SOX10 mutations in Spain

Shah-Waardenburg syndrome or Waardenburg syndrome type 4 (WS4) is a neurocristopathy characterized by the association of deafness, depigmentation and Hirschsprung disease. Three disease-causing genes have been identified so far for WS4: EDNRB, EDN3, and SOX10. SOX10 mutations, found in 45-55% of WS4 patients, are inherited in autosomal dominant way. In addition, mutations in SOX10 are also responsible for an extended syndrome involving peripheral and central neurological phenotypes, referred to as PCWH (peripheral demyelinating neuropathy, central dysmyelinating leucodystrophy, Waardenburg syndrome, Hirschsprung disease). Such mutations are mostly private, and a high intra- and inter-familial variability exists. In this report, we present a patient with WS4 and a second with PCWH due to SOX10 mutations supporting again the genetic and phenotypic heterogeneity of these syndromes. Interestingly, the WS4 family carries an insertion of 19 nucleotides in exon 5 of SOX10, which results in distinct phenotypes along three different generations: hypopigmentation in the maternal grandmother, hearing loss in the mother, and WS4 in the proband. Since mosaicism cannot explain the three different related-WS features observed in this family, we propose as the most plausible explanation the existence of additional molecular events, acting in an additive or multiplicative fashion, in genes or regulatory regions unidentified so far. On the other hand, the PCWH case was due to a de novo deletion in exon 5 of the gene. Efforts should be devoted to unravel the mechanisms underlying the intrafamilial phenotypic variability observed in the families affected, and to identify new genes responsible for the still unsolved WS4 cases.

Research progress in roles of SOX10 gene in Waardenburg syndrome

Waardenburg综合征（Waardenburg syndrome，WS）属于先天性遗传性疾病，是最常见的综合征型耳聋，又称听力一色素综合征，遗传方式主要为单基因致病的常染色体显性遗传伴不全外显。WS属神经嵴病之一，是由于神经嵴细胞（neural crest cells，NCC）发育异常而导致的一组临床症候群，主要以NCC源性黑素细胞分化缺陷致发育异常所导致的色素分布异常和耳聋为特征。荷兰眼科学家及遗传学家Waardenburg于1951年首次报道并以其名字命名该综合征。

Studies on Pathogenesis of Waardenburg Syndrome Type II and Tietz Syndrome Resulting from MITF Gene Mutations

Microphthalmia-associated transcription factor (MITF) controls melanocyte survival and differentiation through directly regulating the expression of the tyrosinase(TYR)and tyrosinase-related proteins 1 and 2(TYRP1 and TYRP2)genes.MITFmutations have been reported to result in an abnormal melanocyte development and lead to Waardenburg syndrome type 2 (WS2), characterized by variable degrees of sensorineural hearing loss and patchy regional distribution of hypopigmentation. Recently,MITFwas also indicated as a causative gene for a more severe syndrome, the Tietz Syndrome (TS), characterized by generalized hypopigmentation and complete hearing loss. However, few functional studies have been performed to compare the diseases-causing mutations. Here, we analyzed thein vitroactivity of two recent identified WS2-associated mutation (p.R217I and p.T192fsX18) and one TS-associated mutation p.N210K. The R217I MITF retained partial activity, normal DNA-binding ability and nuclear distribution, whereas the T192fsX18MITFfailed to activateTYRpromoter due to loss of DNA-binding activity, and aberrant subcellular localization. The aberrant subcellular localization of T192fsX18 MITF may be caused by deletion of a putative nuclear localization signal (NLS) at aa 213-218 (ERRRRF). Indeed, MITF with deletion of the NLS fragment failed to translocate into the nucleus and activated theTYRpromoter. Tagging this NLS to GFP promoted the green fluorescence protein (GFP) translocated into the nucleus. The surprising finding of our study is that a TS-associatedMITFmutation, N210K, showed comparablein vitroactivity as WT. Thus, the possible involvement ofMITFin TS and its underlying mechanisms still need further investigation.

Hereditary hypomelanocytoses: the role of PAX3, SOX10, MITF, SNAI2, KIT, EDN3 and EDNRB genes

Hypo- and hyperpigmentation disorders are the most severe dermatological diseases observed in patients from all over the world. These disorders can be divided into melanoses connected with disorders of melanocyte function and melanocytoses connected with melanocyte development. The article presents some hereditary hypomelanocytoses, which are caused by abnormal melanoblast development, migration and proliferation as well as by abnormal melanocyte viability and proliferation. These disorders are represented by Waardenburg syndrome, piebaldism and Tietz syndrome, and are caused by different mutations of various or the same genes. The types of mutations comprise missense and nonsense mutations, frameshifts (in-frame insertions or deletions), truncating variations, splice alterations and non-stop mutations. It has been demonstrated that mutations of the same gene may cause different hypopigmentation syndromes that may have similar phenotypes. For example, mutations of the MITF gene cause Waardenburg syndrome type 2A as well as Tietz syndrome. It has also been demonstrated that mutations of different genes may cause an identical syndrome. For example, mutations of MITF, SNAI2 and SOX10 genes are observed in Waardenburg syndrome type II and mutations of EDNRB, EDN3 and SOX10 genes are responsible for Waardenburg syndrome type IV. In turn, mutation of the KIT gene and/or heterozygous deletion of the SNAI2 gene result in piebaldism disease. The knowledge of the exact mechanisms of pigmentary disorders may be useful in the development of new therapeutic approaches to their treatment.

Genetic and Phenotypic Heterogeneity in Chinese Patients with Waardenburg Syndrome Type II

Waardenburg Syndrome (WS) is an autosomal-dominant disorder characterized by sensorineural hearing loss and pigmentary abnormalities of the eyes, hair, and skin. Microphthalmia-associated transcription factor (MITF) gene mutations account for about 15% of WS type II (WS2) cases. To date, fewer than 40 different MITF gene mutations have been identified in human WS2 patients, and few of these were of Chinese descent. In this study, we report clinical findings and mutation identification in the MITF gene of 20 Chinese WS2 patients from 14 families. A high level of clinical variability was identified. Sensorineural hearing loss (17/20, 85.0%) and heterochromia iridum (20/20, 100.0%) were the most commonly observed clinical features in Chinese WS2 patients. Five affected individuals (5/20, 25.0%) had numerous brown freckles on the face, trunk, and limb extremities. Mutation screening of the MITF gene identified five mutations: c.20A>G, c.332C>T, c.647_649delGAA, c.649A>G, and c.763C>T. The total mutational frequency of the MITF gene was 21.4% (3/14), which is significantly higher than the 15.0% observed in the fair-skinned WS2 population. Our results indicate that MITF mutations are relatively common among Chinese WS2 patients.

Sonic Hedgehog signaling pathway and regulation of inner ear development

During inner ear development, Sonic Hedgehog (Shh) signaling pathway is involved in the ventral otic identity, cell fate determination of statoacoustic ganglion neurons and hair cell development. Shh protein, secreted from floor plate, antagonizes Wnt protein from roof plate, which refines and maintains dorsoventral axial patterning in the ear. Shh, served as a mitogen during neurogenesis, directly promotes the development of spiral ganglion neuron. After Shh signaling pathway is activated, Ngn1 is freed from Tbx1 repression. As a result, Shh indirectly upregulates the expression of Ngn1, thus regulating neurogenic patterning of inner ear. In addition, Shh regulates the differentiation of hair cells by influencing cell cycle of the progenitor cells located in the cochlea. The basal-to-apical wave of Shh decline ensures the normal devel- opment pattern of hair cells. It is confirmed by a quantity of researches conducted in both animals and patients with hereditary hearing impairment that abnormal Shh signaling results in aberrant transcription of target genes, disturbance of the proper development of inner ear, and human hearing impairment. In humans, diseases accompanied by hearing disorders caused by abnormal Shh signaling include Greig cephalopolysyndactyly syndrome (GCPS), Pallister-Hall syndrome (PHS), Waardenburg syndrome (WS) and medulloblastoma, etc. This review would provide a theoretical basis for further study of molecular mechanisms and clinical use of inner ear development.

Waardenburg Syndrome

A 58-year-old woman with asthma presented to our hospital after 5 days of coughing and worsening dyspnea. Besides wheezing and mild respiratory distress, physical examination revealed complete heterochromia (a right brown eye and a vivid blue left eye) and dystopia canthorum (lateral displacement of inner canthus of the eyes) (Figure). She had had different colored eyes since birth and has been dyeing her hair since she was 18, because it had become entirely white. The first-born of her three sons had blue eyes and the second one had congenital deafness, white hair, and a blue eye. Her youngest son and her husband did not have any apparent abnormality. The patient told us her deaf son had received a diagnosis of Waardenburg syndrome within his first year of life. She was discharged with no symptoms. Waardenburg syndrome is a group of genetic conditions that can produce sensorineural hearing loss, changes in pigmentation of the hair, skin, and eyes, craniofacial alterations, musculoskeletal limb abnormalities, and Hirschsprung disease.1Pingault V. Ente D. Dastot-Le Moal F. et al.Review and update of mutations causing Waardenburg syndrome.Hum Mutat. 2010; 31: 391-406Crossref PubMed Scopus (422) Google Scholar, 2Ur Rehman H. Heterochromia.CMAJ. 2008; 179: 447-448Crossref PubMed Scopus (8) Google Scholar It accounts for 1% to 3% of all cases of congenital deafness and is usually inherited in an autosomal dominant pattern.1Pingault V. Ente D. Dastot-Le Moal F. et al.Review and update of mutations causing Waardenburg syndrome.Hum Mutat. 2010; 31: 391-406Crossref PubMed Scopus (422) Google Scholar The features of Waardenburg syndrome differ among patients, even among people in the same family, as happened in our case. Mutations in any of the 6 genes involved in this entity disrupt the normal development of melanocytes, leading to atypical pigmentation and various degrees of hearing loss. Although most instances of iris heterochromia are sporadic and have no associated underlying abnormalities,2Ur Rehman H. Heterochromia.CMAJ. 2008; 179: 447-448Crossref PubMed Scopus (8) Google Scholar the present case is a reminder that congenital heterochromia can also occur. In this regard, physical examination plays a conspicuous role in diagnosing Waardenburg syndrome and other inborn pigmentary disorders.

Waardenburg Syndrome: Iris and Choroidal Hypopigmentation

Waardenburg syndrome typically manifests with congenital iris pigmentary abnormalities, but careful inspection can reveal additional posterior uveal pigmentary abnormalities. To demonstrate iris and choroidal hypopigmentation in patients with Waardenburg syndrome. Retrospective review of 7 patients referred for evaluation of presumed ocular melanocytosis. To describe the clinical and imaging features of the anterior and posterior uvea. In all patients, the diagnosis of Waardenburg syndrome was established. The nonocular features included white forelock in 4 of 7 (57%), tubular nose in 5 of 6 (83%), and small nasal alae in 5 of 6 (83%) patients. In 2 patients, a hearing deficit was documented on audiology testing. Family history of Waardenburg syndrome was elicited in 5 of 7 (71%) patients. Ocular features (7 patients) included telecanthus in 5 (71%), synophrys in 2 (29%), iris hypopigmentation in 5 (71%), and choroidal hypopigmentation in 5 (71%) patients. No patient had muscle contractures or Hirschsprung disease. Visual acuity was 20/20 to 20/50 in all patients. Iris hypopigmentation in 8 eyes was sector in 6 (75%) and diffuse (complete) in 2 (25%). Choroidal hypopigmentation in 9 eyes (100%) showed a sector pattern in 6 (67%) and a diffuse pattern in 3 (33%). Anterior segment optical coherence tomography revealed the hypopigmented iris to be thinner and with shallower crypts than the normal iris. Posterior segment optical coherence tomography showed a normal retina in all patients, but the subfoveal choroid in the hypopigmented region was slightly thinner (mean, 197 μm) compared with the opposite normal choroid (243 μm). Fundus autofluorescence demonstrated mild hyperautofluorescence (scleral unmasking) in hypopigmented choroid and no lipofuscin abnormality. Waardenburg syndrome manifests hypopigmentation of the iris and choroid with imaging features showing a slight reduction in the thickness of the affected tissue.

Audiological outcomes of cochlear implantation in Waardenburg Syndrome.

Summary Introduction: The most relevant clinical symptom in Waardenburg syndrome is profound bilateral sensorioneural hearing loss. Aim: To characterize and describe hearing outcomes after cochlear implantation in patients with Waardenburg syndrome to improve preoperative expectations. Method: This was an observational and retrospective study of a series of cases. Children who were diagnosed with Waardenburg syndrome and who received a multichannel cochlear implant between March 1999 and July 2012 were included in the study. Intraoperative neural response telemetry, hearing evaluation, speech perception, and speech production data before and after surgery were assessed. Results: During this period, 806 patients received a cochlear implant and 10 of these (1.2%) were diagnosed with Waardenburg syndrome. Eight of the children received a Nucleus 24® implant and 1 child and 1 adult received a DigiSonic SP implant. The mean age at implantation was 44 months among the children. The average duration of use of a cochlear implant at the time of the study was 43 months. Intraoperative neural responses were present in all cases. Patients who could use the speech processor effectively had a pure tone average of 31 dB in free-field conditions. In addition, the MUSS and MAIS questionnaires revealed improvements in speech perception and production. Four patients did not have a good outcome, which might have been associated with ineffective use of the speech processor. Conclusion: Despite the heterogeneity of the group, patients with Waardenburg syndrome who received cochlear implants were found to have hearing thresholds that allowed access to speech sounds. However, patients who received early intervention and rehabilitation showed better evolution of auditory perception.

Congenital Cytomegalovirus Is the Second Most Frequent Cause of Bilateral Hearing Loss in Young French Children

In children with congenital cytomegalovirus (cCMV), greater than 50% of symptomatic newborns and 8.5% to 18% of asymptomatic newborns will have hearing loss, either present at birth or delayed in onset. This prospective study was undertaken to evaluate the extent of cCMV among causes of hearing loss in French children younger than 3 years and to assess their characteristics in relation to cCMV status. Children younger than 3 years with hearing loss were prospectively enrolled. Cytomegalovirus polymerase chain reaction (PCR) assays were performed on dried blood spots from these children’s Guthrie cards and considered positive when CMV presence was confirmed. Brain computed tomography (CT) or magnetic resonance imaging and temporal bone CT scans were obtained. Normal hearing, mild loss, moderate loss, severe loss, and profound loss were defined when the child was able to hear a stimulus of 0 to 20, 21 to 40, 41 to 70, 71 to 90, and 91 dB or greater, respectively. Results of genetic analysis of the connexin 26 (GJB2) and connexin 30 (GJB2) genes were recorded. The prevalence of cCMV infection was estimated together with its 95% confidence interval. Of 114 eligible children, 100 with bilateral hearing loss were enrolled at a median age of 15 months and included in the analysis. Hearing loss in the best ear was not recorded for 2 children and was mild in 1 child, moderate in 22 children, severe in 16, and profound in 59. Results of brain and temporal bone imaging were available for 77 children and genetic analysis of the GJB2 and GJB2 genes for 55 children. Cytomegalovirus PCR was positive in 8 children, and cCMV infection prevalence was 8.0% (95% confidence interval, 2.7%–13.3%). Prevalence of cCMV was 13.7% (n = 8) in the 59 children with profound bilateral hearing loss, a significant association (P = 0.02). Children with cCMV were significantly more likely to have delayed development (P = 0.027) and abnormalities on the brain CT scan (P = 0.0005). Two of the 8 children with cCMV had at least 1 other risk factor for hearing loss, including neonatal intensive care unit stays or familial history of hearing loss. None of the 8 children with cCMV were born prematurely, but 4 had a small birth weight for their gestational age, and 1 child had microcephaly. In 2 children, the diagnosis of cCMV infection had been made before inclusion in the study. For the other 6 children, the diagnosis of cCMV was made retrospectively because of the positive CMV PCR result. In 61 patients (71.8%), the origin of hearing loss was genetic. Mutations of GJB2 and/or GJB2 genes were found in 22 patients (25.9%). In 1 patient (1.2%), hearing loss was due to a mutation in the otoferlin gene. In 13 patients (15.3%), a syndromic origin included Waardenburg syndrome, Usher syndrome, Angelman disease, mucopolysaccharidosis, and another metabolic disease. In 8 patients (9.4%), a malformation was found in the temporal bone on CT scan that was considered genetic. A genetic origin also was highly probable in 10 with a history of 1 family member with hearing loss before age 40 years and consanguineous parents in 7. Prematurity was the cause of hearing loss in 6 children (7.1%). Congenital CMV was present in 8 (9.4%) of the 85 patients with a complete workup and was the second most common individual cause of bilateral hearing loss after connexin mutations. The prevalence of cCMV indicates only the proportion of cCMV among French children with bilateral hearing loss and not the prevalence of cCMV in the total population of children with hearing loss. Because universal neonatal hearing screening is underway in France, it may be possible to diagnose cCMV in infants with confirmed hearing loss and to implement early intervention with antiviral treatment.

Genetic Analyses of a Three Generation Family Segregating Hirschsprung Disease and Iris Heterochromia

We present the genetic analyses conducted on a three-generation family (14 individuals) with three members affected with isolated-Hirschsprung disease (HSCR) and one with HSCR and heterochromia iridum (syndromic-HSCR), a phenotype reminiscent of Waardenburg-Shah syndrome (WS4). WS4 is characterized by pigmentary abnormalities of the skin, eyes and/or hair, sensorineural deafness and HSCR. None of the members had sensorineural deafness. The family was screened for copy number variations (CNVs) using Illumina-HumanOmni2.5-Beadchip and for coding sequence mutations in WS4 genes (EDN3, EDNRB, or SOX10) and in the main HSCR gene (RET). Confocal microscopy and immunoblotting were used to assess the functional impact of the mutations. A heterozygous A/G transition in EDNRB was identified in 4 affected and 3 unaffected individuals. While in EDNRB isoforms 1 and 2 (cellular receptor) the transition results in the abolishment of translation initiation (M1V), in isoform 3 (only in the cytosol) the replacement occurs at Met91 (M91V) and is predicted benign. Another heterozygous transition (c.-248G/A; -predicted to affect translation efficiency-) in the 5′-untranslated region of EDN3 (EDNRB ligand) was detected in all affected individuals but not in healthy carriers of the EDNRB mutation. Also, a de novo CNVs encompassing DACH1 was identified in the patient with heterochromia iridum and HSCRSince the EDNRB and EDN3 variants only coexist in affected individuals, HSCR could be due to the joint effect of mutations in genes of the same pathway. Iris heterochromia could be due to an independent genetic event and would account for the additional phenotype within the family.

MITF mutations associated with pigment deficiency syndromes and melanoma have different effects on protein function

The basic-helix-loop-helix-leucine zipper (bHLHZip) protein MITF (microphthalmia-associated transcription factor) is a master regulator of melanocyte development. Mutations in the MITF have been found in patients with the dominantly inherited hypopigmentation and deafness syndromes Waardenburg syndrome type 2A (WS2A) and Tietz syndrome (TS). Additionally, both somatic and germline mutations have been found in MITF in melanoma patients. Here, we characterize the DNA-binding and transcription activation properties of 24 MITF mutations found in WS2A, TS and melanoma patients. We show that most of the WS2A and TS mutations fail to bind DNA and activate expression from melanocyte-specific promoters. Some of the mutations, especially R203K and S298P, exhibit normal activity and may represent neutral variants. Mutations found in melanomas showed normal DNA-binding and minor variations in transcription activation properties; some showed increased potential to form colonies. Our results provide molecular insights into how mutations in a single gene can lead to such different phenotypes.