Waardenburg syndrome (WS) is a highly clinically and genetically heterogeneous disease. The core disease phenotypes of WS are sensorineuronal hearing loss and pigmentary disturbance, which are usually caused by the absence of neural crest cell-derived melanocytes. At present, four subtypes of WS have been defined, which are caused by seven genes. Waardenburg syndrome type 2 (WS2) is one of the most common forms. Two genes, MITF and SOX10, have been found to be responsible for majority of WS2.
In this study, we performed a clinical longitudinal follow-up and mutation screening for a Chinese family with Waardenburg syndrome type II.
A diversity of clinical manifestations was observed in this WS2 family. In addition to the congenital hearing loss of most affected family members, progressive hearing loss was also found in some WS2 patients. A nonsense mutation of c.328C>T (p.R110X) in MITF was identified in all affected family members. This mutation results in a truncated MITF protein, which is considered to be a disease-causing mutation.
These findings offer a better understanding of the spectrum of MITF mutations and highlight the necessity of continuous hearing assessment in WS patients.

The purpose of this study is to profile the clinical and genetic features of Japanese Waardenburg syndrome (WS) patients and validate the W index. Sixteen Japanese WS families with congenital sensorineural hearing loss were included in the study. The inner canthal, interpupillary, and outer canthal distances (ICD, IPD, and OCD) were measured for all patients, and patients were screened for presence of PAX3, MITF, SOX10, and EDNRB mutations. The WS patients were clinically classified under the current W index as follows: 13 families with WS1, 2 families with WS2, and 1 family with WS4. In the 13 WS1 families, genetic tests found PAX3 mutations in 5 families, MITF mutations in 4 families, SOX10 mutations in 3 families, and EDNRB mutations in 1 family. 61% of clinically classified WS1 patients under the current W index conflicted with the genetic classification, which implies W index is not appropriate for Japanese population. Resetting the threshold of W index or novel index formulated with ethnicity matched samples is necessary for clinical classification which is consistent with genetic classification for WS patients with distinct ethnicity.

OBJECTIVE: To explore the pathogenetic mechanism of a family affected with Waardenburg syndrome.
METHODS: Clinical data of the family was collected. Potential mutation of the MITF, SOX10 and SNAI2 genes were screened. Plasmids for wild type (WT) and mutant MITF proteins were constructed to determine their exogenous expression and subcellular distribution by Western blotting and immunofluorescence assay, respectively.
RESULTS: A heterozygous c.763C>T (p.R255X) mutation was detected in exon 8 of the MITF gene in the proband and all other patients from the family. No pathological mutation of the SOX10 and SNAI2 genes was detected. The DNA sequences of plasmids of MITFwild and mutant MITFR255X were confirmed. Both proteins were detected with the expected size. WT MITF protein only localized in the nucleus, whereas R255X protein showed aberrant localization in the nucleus as well as the cytoplasm.
CONCLUSIONS: The c.763C>T mutation of the MITF gene probably underlies the disease in this family. The mutation can affect the subcellular distribution of MITF proteins in vitro, which may shed light on the molecular mechanism of Waardenburg syndrome caused by mutations of the MITF gene.

OBJECTIVE: To explore the molecular etiology of two pedigrees affected with type II Waardenburg syndrome (WS2) and to provide genetic diagnosis and counseling.
METHODS: Blood samples were collected from the proband and his family members. Following extraction of genomic DNA, the coding sequences of PAX3, MITF, SOX10 and SNAI2 genes were amplified with PCR and subjected to DNA sequencing to detect potential mutations.
RESULTS: A heterozygous deletional mutation c.649_651delAGA in exon 7 of the MITF gene has been identified in all patients from the first family, while no mutation was found in the other WS2 related genes including PAX3, MITF, SOX10 and SNAI2.
CONCLUSIONS: The heterozygous deletion mutation c.649_651delAGA in exon 7 of the MITF gene probably underlies the disease in the first family. It is expected that other genes may also underlie WS2.

Waardenburg syndrome is an autosomal dominant disorder with an incidence of 1 in 40,000 that manifests with sensorineural deafness, pigmentation defects of the skin, hair and iris and various defects of neural crest-derived tissues. This genetically heterogeneous disease accounts for >2 % of the congenitally deaf population. Mutations in the EDN3, EDNRB, MITF, PAX3, SNAI2, and SOX10 genes can cause Waardenburg syndrome. We here report a case of 12 year old female who presented with chief complaint of decreased hearing in both ears and had clinical features consistent with Waardenburg syndrome. She had a distinct white forelock of hair in the midline along with striking bilateral blue iris. Also a white depigmented patch was present on the right forearm. Both eyes had bright red fundal reflex with choroidal depigmentation. Her younger brother, the second case in this study, had similar blue eyes, white forelock of hair, depigmented skin patch and choroidal depigmentation but with normal hearing. Their father had a history of premature graying of hair. All the primary care physicians coming across a child with blue eyes and white forelock of hair should get the child\'s hearing tested at the first instance, if not already tested. An early diagnosis and improvement of hearing impairment with timely intervention are the most important for psychological and intellectual development of children with Waardenburg syndrome.

Craniofacial morphology is highly heritable, but little is known about which genetic variants influence normal facial variation in the general population. We aimed to identify genetic variants associated with normal facial variation in a population-based cohort of 15-year-olds from the Avon Longitudinal Study of Parents and Children. 3D high-resolution images were obtained with two laser scanners, these were merged and aligned, and 22 landmarks were identified and their x, y, and z coordinates used to generate 54 3D distances reflecting facial features. 14 principal components (PCs) were also generated from the landmark locations. We carried out genome-wide association analyses of these distances and PCs in 2,185 adolescents and attempted to replicate any significant associations in a further 1,622 participants. In the discovery analysis no associations were observed with the PCs, but we identified four associations with the distances, and one of these, the association between rs7559271 in PAX3 and the nasion to midendocanthion distance (n-men), was replicated (p = 4 × 10(-7)). In a combined analysis, each G allele of rs7559271 was associated with an increase in n-men distance of 0.39 mm (p = 4 × 10(-16)), explaining 1.3% of the variance. Independent associations were observed in both the z (nasion prominence) and y (nasion height) dimensions (p = 9 × 10(-9) and p = 9 × 10(-10), respectively), suggesting that the locus primarily influences growth in the yz plane. Rare variants in PAX3 are known to cause Waardenburg syndrome, which involves deafness, pigmentary abnormalities, and facial characteristics including a broad nasal bridge. Our findings show that common variants within this gene also influence normal craniofacial development.

OBJECTIVE: The spontaneous mouse mutant Dominant megacolon (Dom) represents the model of the Waardenburg-Hirschsprung\'s disease, a syndromic pathology, characterized by the association of pigmentation defects (PD), deafness, and Hirschsprung\'s disease (HD). The defect in Dom mouse is caused by a spontaneous mutation of the gene encoding the Sry-related transcription factor Sox10. This mutation affects several aspects of neural crest development leading to combined enteric innervation and pigmentation defects, both in mouse and human. The purpose of this report is to define, by enzymo-histochemical techniques routinely used for the diagnosis of human Hirschsprung\'s disease (AChE, LDH, NADPH-diaphorase), the innervative patterns of the affected gut.
METHODS: Fifty-four siblings of Heterozygous Dom/+ mice underwent autopsy and were genotyped by direct sequencing of polymerase chain reaction (PCR) products for Sox10 mutations. The enteric nervous system of all the mice was studied by histochemical techniques indicated above.
RESULTS: Genotyping showed that 43 mice were Dom/+ and 11 were Wild type +/+. Wild-type +/+ mice were used as control. The correspondence between genotype and at least 1 phenotypic aspect (PD or dysganglionosis) was present in 93% of cases (41 of 43). Among the Dom/+ mice, dysganglionosis was present in 79% of cases and PD in 90% of cases. Moreover, among Dom/+ mice, excluding those whose mantle was not evaluated as dead just after birth, PD and dysganglionosis (complete phenotype) were present in 68% of cases.
CONCLUSIONS: The histochemical methods that we used proved to be useful for identification of different aganglionic (AG), hypoganglionic (HG), and normoganglionic segments of Dom/+ mouse gut studied in longitudinal sections. Unlike humans, control mice (Wild type +/+) presented a rich component of AChE nerve fibers, whereas Dom/+ mice with dysganglionosis presented a decrease in AChE-positive nerve fibers. These data confirm the variable phenotypic penetrance in heterozygous mice. Because dysganglionosis in this animal model (Dom/+) was evident in 79% of cases (AG or HG), we concluded that Dom mice could represent important models for further experimental studies.

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