RT Journal Article
SR Electronic
T1 Spectrum of novel mutations found in Waardenburg syndrome types 1 and 2: implications for molecular genetic diagnostics
JF BMJ Open
JO BMJ Open
FD British Medical Journal Publishing Group
SP e001917
DO 10.1136/bmjopen-2012-001917
VO 3
IS 3
A1 Gabriele Wildhardt
A1 Birgit Zirn
A1 Luitgard M Graul-Neumann
A1 Juliane Wechtenbruch
A1 Markus Suckfüll
A1 Annegret Buske
A1 Axel Bohring
A1 Christian Kubisch
A1 Stefanie Vogt
A1 Gertrud Strobl-Wildemann
A1 Marie Greally
A1 Oliver Bartsch
A1 Daniela Steinberger
YR 2013
UL http://bmjopen.bmj.com/content/3/3/e001917.abstract
AB Objectives Till date, mutations in the genes PAX3 and MITF have been described in Waardenburg syndrome (WS), which is clinically characterised by congenital hearing loss and pigmentation anomalies. Our study intended to determine the frequency of mutations and deletions in these genes, to assess the clinical phenotype in detail and to identify rational priorities for molecular genetic diagnostics procedures. Design Prospective analysis. Patients 19 Caucasian patients with typical features of WS underwent stepwise investigation of PAX3 and MITF. When point mutations and small insertions/deletions were excluded by direct sequencing, copy number analysis by multiplex ligation-dependent probe amplification was performed to detect larger deletions and duplications. Clinical data and photographs were collected to facilitate genotype–phenotype analyses. Setting All analyses were performed in a large German laboratory specialised in genetic diagnostics. Results 15 novel and 4 previously published heterozygous mutations in PAX3 and MITF were identified. Of these, six were large deletions or duplications that were only detectable by copy number analysis. All patients with PAX3 mutations had typical phenotype of WS with dystopia canthorum (WS1), whereas patients with MITF gene mutations presented without dystopia canthorum (WS2). In addition, one patient with bilateral hearing loss and blue eyes with iris stroma dysplasia had a de novo missense mutation (p.Arg217Ile) in MITF. MITF 3-bp deletions at amino acid position 217 have previously been described in patients with Tietz syndrome (TS), a clinical entity with hearing loss and generalised hypopigmentation. Conclusions On the basis of these findings, we conclude that sequencing and copy number analysis of both PAX3 and MITF have to be recommended in the routine molecular diagnostic setting for patients, WS1 and WS2. Furthermore, our genotype–phenotype analyses indicate that WS2 and TS correspond to a clinical spectrum that is influenced by MITF mutation type and position.