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Product summary

  • Technology FISH
  • Application Cytogenetics & rare disease
  • Areas of interest Constitutional
  • Region 7p21.1 / 7q11.23
  • Label    
  • Product No. LPU 024 (10 tests)
    LPU 024-S (5 tests)
  • Intended use In vitro diagnostic. This product is intended to be used on Carnoy’s solution (3:1 methanol/acetic acid) fixed peripheral blood samples.

Chromomaps

Overview

Probe specification

  • TWIST1, 7p21.1, Red
  • WBSCR, 7q11.23, Green

The TWIST1 probe is 179kb, labelled in red and covers a region including the entire TWIST1 gene and flanking DNA. The Williams-Beuren region probe, labelled in green, consists of three non-overlapping clones (148kb, 144kb and 204kb), which cover much of the deletion region.

 

Probe information

Saethre-Chotzen syndrome is a rare, congenital, autosomal dominant disorder characterised by craniofacial and limb abnormalities1.

The incidence of this syndrome is estimated to be 1 in 25,000-50,000 live births, though due to the phenotype often being very mild, it is possible that the syndrome is under diagnosed1. The identification of TWIST1 (a basic helix-loop-helix transcription factor on chromosome band 7p21.1) as a causative gene2,3 has proved invaluable for the diagnosis of this phenotypically variable disorder1.

Williams-Beuren Syndrome (WBS) is a rare neurodevelopmental disorder caused by a deletion (approx. 1.5-1.8Mb in size, containing around 28 genes6) within chromosome band 7q11.234. The incidence of this syndrome is estimated at 1 in 7,500 to 20,000 live births5,6.

Patients display a distinctive ‘elfin’ facial appearance, connective tissue problems, SupravalVular Aortic Stenosis (SVAS), growth retardation, renal anomalies, transient hypercalcaemia, hyperacusis and mental retardation7. Haploinsufficiency or hemizygosity of the elastin (ELN) gene has been identified as being responsible for the SVAS8,9 but none of the other clinical features of the syndrome have been unequivocally attributed to specific genes within the WBS deleted region. These genotype-phenotype 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 breakpoints10.

The Saethre-Chotzen/Williams-Beuren Combination contains a red probe that covers the TWIST1 gene for Saethre-Chotzen syndrome and a green probe covering the area around the ELN gene in the Williams-Beuren syndrome deleted region. 

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References

  1. Orphanet ♯ ORPHA794: www.orpha.net
  2. Howard TD et al., Nat Genet 1997;15:36-41
  3. El Ghouzzi V et al., Nat Genet 1997;15:42-6
  4. Francke U et al., Hum Mol Genet 1999;8:1947-54
  5. Stromme et al., J. Child. Neurol 2002;17:269-71
  6. OMIM ♯194050. www.omim.org/194050
  7. Pober BR and Dykens EM. Child Adolesc Psychiatr ClinNorth Am 1996;5:929-43
  8. Li DY et al., Hum Mol Genet 1997;6:1021-8
  9. Tassabehji M et al., Hum Mol Genet 1997;6:1029-36
  10. Merla et al., Am J Hum Genet 2006; 79:332-341

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