2009 Vienna - European Society of Human Genetics

Molecular and biochemical basis of disease
P16.19
Genetic screening of long Qt syndrome (LQts) in sweden
A. Norberg 1 , K. Cederqvist 1 , J. Jonasson 1 , B. Jonsson 1 , A. Rydberg 2,3 , S. Jensen
4,3 , E. Stattin 1,3 ;
1 Clinical Genetics, Umeå, Sweden, 2 Barn- och ungdomskliniken, Umeå, Sweden,
3 Center for Cardiovascular Genetics, Umeå, Sweden, 4 Hjärtcentrum,
Umeå, Sweden.
Background: Long QT syndrome (LQTS) is a hereditary cardiac disease
characterized by prolongation of the QT interval on ECG and
presence of syncope, seizures, and sudden death. The most common
genes implicated in LQTS are the cardiac ion channel subunits
KCNQ1, KCNH2, SCN5A, KCNE1 and KCNE2, accounting for about
70% of the identified mutations in patients with a clinical diagnosis.
The symptoms are very variable in LQTS patients, and genotype influences
the clinical course.
Objective: This study aims to report the spectrum of LQTS mutations
in Sweden, as well as genotype-phenotype correlations. Knowledge of
founder mutations or certain subdiagnostic criteria for different mutations
will facilitate the molecular genetic analysis, thereby reducing the
turn-around time and cost.
Methods: Twohundred consecutive, unrelated patients referred for
LQTS genetic testing will be evaluated. Coding sequences and splice
sites of the five genes, as well as alternate transcript exon 1B of KCNQ1
and KCNH2, will be screened for genomic variants by denaturing highperformance
liquid chromatography (dHPLC) and DNA sequencing.
Furthermore, multiplex ligation-dependent probe amplification (MLPA)
will be performed in all patients to detect large deletions or duplications.
Selected patients will also be screened for mutations in RYR2,
a gene known to be involved in the clinically overlapping disease catecholaminergic
polymorphic ventricular tachycardia (CPVT1).
Results: So far, a total number of 180 probands have been included
in the study. Preliminary results have identified two common founder
mutations, as well as other mutations in about 63% of the patients,
whereas double mutations seem to be rare.
P16.20
scN5A mutations in Brugada syndrome spanish patients
E. Coto Garcia 1 , M. Garcia-Castro 1 , J. R. Reguero 2 , V. Alvarez 1 ;
1 Genetica-Huca, Oviedo, Spain, 2 Cardiología-Huca, Oviedo, Spain.
Brugada syndrome (BS) is characterized by cardiac ST-segment
abnormalities and a high risk of ventricular arrhythmias and sudden
death. Age at diagnosis ranges from 2 days to 85 years. BS is
diagnosed based on clinical findings, and SCN5A (α-subunit of the
sodium channel), is the only gene currently known to be associated
with Brugada syndrome. Sequencing of SCN5A identified mutations
in approximately 25% of individuals with BS. Mutation carriers are frequently
asymptomatic, even at advanced ages. The identification of
asymptomatic mutation carriers enables the use of preventive measures
to avoid ventricular arrhythmias. Most of the SCN5A mutations
are private, and the 26 coding exons should be analysed to define the
mutational status of BS patients.
We sequenced this gene in 25 BS patients from the region of Asturias
(Northern Spain) (81% male; mean age at diagnosis, 41±14
years, range 17-66). The 26 coding exons were PCR-amplified and
sequenced using BigDye chemistry in an ABI3130 system. All the variants
found in the patients were also screened in 200 healthy population
controls, using SSCA and DHPLC.
We found 17 SCNA5 variants, and 13 were also found in the controls,
thus being DNA polymorphisms. Four were putative mutations, found
only in one patient and none of the controls: three missense changes
(Ala2Thr; Ala739Thr; Val134Ile) and a splicing mutation (IVS18 -1G>A,
intron 18).
We found relatives of these patients who were mutation carriers, some
of them symptomatic. We discussed these findings, in particular the
genetic counseling of SCN5A mutation carriers.
P16.21
A novel alpha-tropomyosin mutation in a large family with
dilated cardiomyopathy
J. B. A. van de Meerakker 1 , I. Christiaans 2 , P. Barnett 1 , R. H. Lekanne
Deprez 2 , A. Ilgun 1 , M. M. A. M. Mannens 3 , A. F. M. Moorman 1 , A. A. M. Wilde 1 ,
A. V. Postma 1 ;
1 Heart Failure Research Center, Academic Medical Center, Amsterdam, The
Netherlands, 2 Department of clinical genetics, Academic Medical Center, Amsterdam,
The Netherlands, 3 Department of clinical genetics, Academic Medical
Center, Amsterdam, The Netherlands.
Dilated cardiomyopathy (DCM) is characterized by dilatation and
systolic contractile dysfunction of the left and/or right ventricle and
consequently by an impaired systolic function. The origin of DCM is
heterogeneous but genetic transmission of the disease accounts for
10-35% of cases. We present a large three-generation family in which
DCM inherits as an autosomal dominant trait. Six family members
have DCM, with the age of diagnosis ranging from five months to 52
years. The youngest one was initially diagnosed with non-compaction
cardiomyopathy (NCCM) and died at the age of five. Three additional
young children died of suspected heart problems. We mapped the
phenotype of this family to chromosome 15 and subsequently identified
a missense mutation in alpha-tropomyosin (TPM1), leading to a
p.D84N amino acid substitution. Tropomyosins are sarcomeric, thin
filament proteins that play fundamental, structural and regulatory roles
in skeletal and cardiac muscle cells. The far majority of mutations in
TPM1 are associated with hypertrophic cardiomyopathy (HCM) and
few with DCM. Our mutation has not been described before and was
not detected in 400 control chromosomes. It co-segregates with all
clinically affected family members, and is predicted, using existing
atomic and protein models, to weaken the binding of tropomyosin to
actin. In conclusion, DCM causing mutations in TPM1 are associated
with a divers phenotype including also lethal, early onset forms. The
screening of patients and families with these forms of DCM for TPM1
is therefore warranted.
P16.22
investigation of human mitochondrial DNA in iranian
Hypertrophic cardiomyopathy (Hcm) patients
H. Aryan, M. Houshmand;
Special Medical Center, Tehran, Islamic Republic of Iran.
Mitochondrial (mt) DNA defects, both deletions and tRNA point mutations,
have been associated with cardiomyopathies. The aim of the
study was to determine the mtDNA mutations in Hypertrophic cardiomyopathy
(HCM) Iranian patients.
Hypertrophic cardiomyopathy (HCM) is widely accepted as a pluricausal
or multifactorial disease. Because of the linkage between energy metabolism
in the mitochondria and cardiac muscle contraction, it is reasonable
to assume that mitochondrial abnormalities may be responsible
for some forms of HCM. We analysed the whole mitochondrial genome
in a series of 31 patients with HCM for alterations and compared the
findings with those of 30 control subjects. A total of X sequence changes
could be identified. These sequence changes were distributed among
the whole mitochondrial DNA (mtDNA). An increased number of novel
missense mutations could be detected nearly in all genes encoding for
protein subunits in HCM patients subjects. Four mutations were found
that are unpublished. The c.4384T>C in tRNA glutamin, c.9063A>G in
AtPase6, c.2071 T>C, c.3170C>A, in noncoding MTRNA2 16S. Also
33 polymorphisms were identified in this study which had not been published
in the MitoMap database. The c.16189T>C mutation in the D-loop
region that is associated with susceptibility to DCM could be detected in
3% of patients as well as in 0% of controls. Furthermore, mtDNA mutations
may play an important role in pathogenesis of cardiac arrest which
has remained unexplained for long.
P16.23
severe hypertrophic cardiomyopathy in adults and children:
similar gene mutations for a wide spectrum of clinical
manifestations
C. Simon 1 , L. Pezzoli 2 , D. Marchetti 2 , A. Iacovoni 1 , D. Barachetti 2 , A. R. Lincesso
2 , S. Pentiricci 1 , P. Ferrazzi 1 , M. Iascone 2 ;
1 Dipartimento Cardiovascolare, Ospedali Riuniti, Bergamo, Italy, 2 Genetica
Molecolare – USSD Lab Genetica Medica, Ospedali Riuniti, Bergamo, Italy.
HCM is a myocardial disease characterized by huge phenotypic and
genotypic heterogeneity. Affecting 1 in 500 individuals, it’s the most
common cause of sudden death in young athletes. HCM is caused
by mutations in at least 13 genes, most commonly MYH7 (β-myosin
heavy chain) and MYBPC3 (myosin-binding protein C). We analysed
these genes in 105 patients: 41 with HCM diagnosed before 18 years
of age (group A: mean age, 7 years) and 64 adults (group B: mean
age, 52 years). From 2001 to 2006 the analysis was performed by