Defects in imprinted gene expression at 11p15 are associated with BWS . Greater than 70% of cases are found to have alterations in DNA methylation at two distinct differentially methylated regions (DMRs) at 11p15. DMR1 is located within the telomeric domain (also known as ICR1) and controls the expression of two genes, IGF2 and H19. DMR2 is located within the centromeric domain (also known as ICR2) and controls the expression of KCNQ1, CDKN1C, SLC22A1L and the TSSC3 genes. Alterations in DNA methylation at either of these DMRs causes aberrant expression of these imprinted genes leading to Beckwith-Wiedemann Syndrome.
BWS is typically sporadic, though inheritance has also been reported in an autosomal dominant pattern, due to other mutations. No single explanation can account for the phenotypic heterogeneity seen in patients with BWS. The recurrence risk due to methylation defects is estimated to be low.
1. Weksberg R, Smith AC, Squire J, Sadowski P. Hum Mol Genet. 2003; 12: R61-68.
2. Gaston V, Le Bouc Y, Soupre V, Burglen L et al. Eur J Hum Genet. 2001; 6:409-418.
3. Coffee, B, Muralidharan, K, Highsmith, WE, Lapunzina, P, and Warren, ST. Genet. Med. 2006: 8(10): 628-634.
- Individuals with a clinical diagnosis of Beckwith-Wiedemann syndrome.
- Individuals with isolated segmental hemihyperplasia.
Detection and Reference Range
Hypomethylation of DMR2 (Lit1 gene) is expected to detect up to 60-70% of individuals with BWS.
For DMR2 (Lit1 gene), a decrease in DNA methylation of greater than two standard deviations below the mean of normal is consistent with BWS. See Coffee et al. for explanation of reference range .
Submit only 1 of the following specimen types
Preferred specimen type: Whole Blood
Type: Whole Blood
Specimen Requirements:In EDTA (purple top) or ACD (yellow top) tube:
Infants (<2 years): 2-3 ml
Children (>2 years): 3-5 ml
Older Children & Adults: 5-10 ml
Specimen Collection and Shipping: Refrigerate until time of shipment. Ship sample within 5 days of collection at room temperature with overnight delivery.
Specimen Requirements:OrageneTM Saliva Collection kit (available through EGL) used according to manufacturer instructions.
Specimen Collection and Shipping: Store sample at room temperature. Ship sample within 5 days of collection at room temperature with overnight delivery.
- Chromosome analysis (CA, CB) and array CGH is available for children with growth disorders and congenital anomalies with or without mental retardation.
- Methylation for DMR1 (H19 gene) combined with methylation for DMR2 (Lit1 gene) is offered as a separate panel when no previous studies have been performed.