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1.  Diabetic Dead-in-Bed Syndrome: A Possible Link to a Cardiac Ion Channelopathy 
Case Reports in Medicine  2014;2014:647252.
Sudden unexpected nocturnal death among patients with diabetes occurs approximately ten times more commonly than in the general population. Malignant ventricular arrhythmia due to Brugada syndrome has been postulated as a cause, since a glucose-insulin bolus can unmask the Brugada electrocardiographic signature in genetically predisposed individuals. In this report we present a 16-year-old male with insulin-dependent diabetes who died suddenly at night. His diabetes had been well controlled, without significant hypoglycaemia. At autopsy, he had a full stomach and a glucose level of 7 mmol/L in vitreous humor, excluding hypoglycaemia. Genetic analysis of autopsy DNA revealed a missense mutation, c.370A>G (p.Ile124Val), in the GPD1L gene. A parent carried the same mutation and has QT prolongation. Mutations in this gene have been linked to Brugada syndrome and sudden infant death. The patient may have died from a ventricular arrhythmia, secondary to occult Brugada syndrome, triggered by a full stomach and insulin. The data suggest that molecular autopsies are warranted to investigate other cases of the diabetic dead-in-bed syndrome.
PMCID: PMC3970469  PMID: 24715918
2.  Biophysical Properties of 9 KCNQ1 Mutations Associated with Long QT Syndrome (LQTS) 
Inherited long QT syndrome (LQTS) is characterized by prolonged QT interval on the EKG, syncope and sudden death due to ventricular arrhythmia. Causative mutations occur mostly in cardiac potassium and sodium channel subunit genes. Confidence in mutation pathogenicity is usually reached through family genotype-phenotype tracking, control population studies, molecular modelling and phylogenetic alignments, however, biophysical testing offers a higher degree of validating evidence.
Methods and Results
By using in-vitro electrophysiological testing of transfected mutant and wild-type LQTS constructs into Chinese Hamster Ovary cells, we investigated the biophysical properties of 9 KCNQ1 missense mutations (A46T, T265I, F269S, A302V, G316E, F339S, R360G, H455Y, and S546L) identified in a New Zealand based LQTS screening programme. We demonstrate through electrophysiology and molecular modeling that seven of the missense mutations have profound pathological dominant negative loss-of-function properties confirming their likely disease-causing nature. This supports the use of these mutations in diagnostic family screening. Two mutations (A46T, T265I) show suggestive evidence of pathogenicity within the experimental limits of biophysical testing, indicating that these variants are disease-causing via delayed or fast activation kinetics. Further investigation of the A46T family has revealed an inconsistent co-segregation of the variant with the clinical phenotype.
Electrophysiological characterisation should be used to validate LQTS pathogenicity of novel missense channelopathies. When such results are inconclusive, great care should be taken with genetic counselling and screening of such families, and alternative disease causing mechanisms should be considered.
PMCID: PMC2748886  PMID: 19808498
Long QT; Mutations; Arrhythmia; Ion Channels; Sudden Cardiac Death
3.  Long QT molecular autopsy in sudden infant death syndrome 
Archives of Disease in Childhood  2014;99(7):635-640.
To describe experience of long QT (LQT) molecular autopsy in sudden infant death syndrome (SIDS).
Descriptive audit from two distinct periods: (1) A prospective, population-based series between 2006 and 2008 (‘unselected’). (2) Before and after 2006–2008, with testing guided by a cardiac genetic service (‘selected’). LQT genes 1, 2, 3, 5, 6 and 7 were sequenced. Next of kin were offered cardiac evaluation.
New Zealand.
102 SIDS cases.
Main outcome measures
Detection of genetic variants.
Maori 49 (47%), and Pacific island 24 (23%), infants were over-represented. Risk factors were common; bed sharing was reported in 49%. Rare genetic variants were commoner within the selected than unselected populations (5 of 31 infants (16%) vs 3 of 71 infants (4%) p < 0.05). In the selected population two infants had variants of definite or probable pathogenicity (KCNQ1, E146K; KCNH2, R1047L), two had novel variants of possible pathogenicity in SCN5A (I795F, F1522Y) and one had R1193Q in SCN5A, of doubtful pathogenicity. R1193Q was also the only variant in the three cases from the unselected population and occurred as a second variant with R1047L. Engaging families proved challenging. Only 3 of 8 (38%) variant-positive cases and 18 of 94 (19%) of variant-negative families participated in cardiac/genetic screening.
LQT molecular autopsy has a very low diagnostic yield among unselected SIDS cases where risk factors are common. Diagnostic yield can be higher with case selection. Engagement of the family prior to genetic testing is essential to counsel for the possible uncertainty of the results and to permit family genotype-phenotype cosegregation studies.
PMCID: PMC4078670  PMID: 24596401
SIDS; Genetics; long QT Syndrome; Molecular Autopsy

Results 1-3 (3)