Williams-Beuren, 7q11.23, Red
D7Z1, 7p11.1-q11.1, Green
The Williams-Beuren probe, labelled in red, consists of three non-overlapping clones (148kb, 144kb and 204kb), which cover much of the deletion region. The probe mix also contains a control probe for the 7 centromere (D7Z1), labelled in green.
Williams-Beuren Syndrome (WBS) is a rare neurodevelopmental disorder caused by a deletion (approximately 1.5-1.8Mb in size, containing around 28 genes) within chromosome band 7q11.231. The incidence of this syndrome is estimated at 1 in 7,500 to 20,000 live births2,3,4.
Patients display a distinctive ‘elfin’ facial appearance, connective tissue problems, supravalvular aortic stenosis (SVAS), growth retardation, renal anomalies, transient hypercalcaemia, hyperacusis and mental retardation5. Haploinsufficiency of the elastin (ELN) gene has been identified as being responsible for the SVAS6,7 but none of the other clinical features of the syndrome have been unequivocally attributed to specific genes within the WBS deleted region. These genotype-phenpotype correlations are made more difficult in WBS patients as the deletion has also been shown to have an effect on normal copy number genes that neighbour the deletion breakpoints8.
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