Clinical and genetic investigation of families with Waardenburg syndrome type 2

Abstract

Objective:To investigate the clinical chacteration and molecular pathology of Waardenburg syndrome type 2 in seven families, and provide genetic diagnosis and hereditary counseling for family members. Method:Clinical data of seven families with WS2（14 patients）were collected. Peripheral blood samples of the probands and related family members were collected and genomic DNA was extracted. The coding sequences of microphthalmia associated transcription factor (MITF), sex-determining region Y-box 10(SOX10), snail family zinc finger 2 (SNAI2) and endothelin receptor type B（EDNRB）were analyzed by polymerase chain reaction and DNA sequencing. Then the raw data was analyzed. Result:The most common manifestations of WS2 are sensorineural hearing loss(10/14,71.4%), freckle(7/14, 50.0%)，heterochromia iridis(6/14, 42.9%) and premature greying(5/14,35.7%). All the deafness phenotype is congenital, bilateral profound sensorineural hearing loss. Freckles phenotype is different from cutaneous pigment abnormalities of WS in Westerners. The heterozygous mutation, c.328C>T in exon 3 of the MITF gene was detected in the proband and all patients of pedigree 2. However, no pathological mutation of the relevant genes (SOX10,SNAI2 and EDNRB) was detected in other pedigrees. Conclusion:There are obvious variations in clinical features of WS, while freckles may be a special subtype of cutaneous pigment disturbances. The MITF gene mutation, R110X,is therefore considered the disease causing mutation in pedigree WS02.However, there are novel disease causing genes or copy number variations in Waardenburg syndrome type 2, which require further research.