Use of the newborn screening card to define cause of death in a 12-year-old diagnosed with epilepsy

Post-mortem investigation of sudden death in young people frequently reveals no overt cause for the death. Full investigation is hampered if tissue or blood is not retained for DNA analysis. We report a post mortem molecular diagnosis of long QT syndrome in a 12-year-old boy diagnosed with epilepsy who died suddenly playing sport. The DNA was extracted from an archived blood spot on his newborn screening ('Guthrie') card, which had been taken from him at 6 days of age. A missense mutation was detected in exon 5 of the KCNQ1 gene; R243C (835C > T), associated with long QT type 1. The same mutation was found in the mother (who now takes effective preventative therapy), but not in the sib who has now been reassured that she is not at risk of sudden death.

Detection of sequence variations in the adenomatous polyposis coli (APC) gene using denaturing high-performance liquid chromatography

We have evaluated the usefulness of denaturing high performance liquid chromatography (dHPLC) for scanning the adenomatous polyposis coli (APC) gene for point mutations, small deletions, and insertions. Our assay consists of 28 sets of primers to amplify the 15 exons of the APC gene. All PCR reactions were amplified simultaneously using the same reaction conditions in a 96-well format and then analyzed by dHPLC, using empirically determined optimum temperatures for partial fragment denaturation. Previously studied DNA specimens from 47 familial adenomatous polyposis (FAP) patients were analyzed by dHPLC and all mutations were correctly identified and confirmed by sequence analysis. This approach identified a single-base substitution in exon 6 and a 2-bp insertion in exon 15 that initially had not been detected by single-strand conformational polymorphism (SSCP) analysis. A novel mutation in exon 15 of the APC gene, 2065delG (codon 689) that had previously been undetected by the protein truncation test (PTT) was also identified by dHPLC. We present our validation studies of dHPLC technology for APC gene analysis in terms of sensitivity and specificity and compare it to current standard scanning technologies including PTT, SSCP, and conformational sensitive gel electrophoresis (CSGE).

Compound heterozygosity at the FMR1 gene

Individuals affected with Fragile X syndrome are usually characterized at the DNA level by the presence of at least 200 CGG repeats in the 5' untranslated region of the FMR1 gene; this number of repeats is defined as a full mutation. Repeats that number 50-200 usually define those with premutations and are termed unaffected carriers. We report here a compound heterozygous female who carried CGG repeats in the FMR1 gene that fall within the premutation and full mutation ranges. The former appears to have been inherited from the father, whereas the latter is an expansion of the premutation carried by the proband's mother. Therefore, the offspring of the proband will carry a significant risk of being affected with Fragile X syndrome, and the paternal uncle and any cousins should be counselled for being at risk for this syndrome.