European Human Genetics Conference 2007 June 16 – 19, 2007 ...

Molecular and biochemical basis of disease
Faculty of Medicine, University of Szeged, Szeged, Hungary.
Objectives: Genetic origin is important in the development of hypertrophic
cardiomyopathy (HCM) which is characterized by myocardial
hypertrophy and rhythm disorders. The third most common mutated
gene leading to HCM is the troponin-T (TNNT2) gene with an incidence
of 2%. Our aim was to analyze mutations of the TNNT2 gene in
children and young adults.
Patients and methods: DNA was isolated from peripheral blood of 26
patients followed by PCR (TNNT2 gene, exons 8,11,14,15,16). Mutation
analysis was performed using dHPLC and positive chromatograms
were sequenced.
Results: One mutation was found in the patient cohort (3,8%). It is a
novel mutation, a deletion of a glutamic acid in exon 11, at one of the
amino acid positions between 165-168. This mutation has not been
published in the literature so far. The patient is a 19 year-old girl, who
had endured aborted sudden cardiac death (SCD) twice, so implantation
of an implantable cardioverter defibrillator was necessary. Family
screening revealed that the patient’s mother also had HCM. Her
disease was characterised by mild septal hypertrophy, pronounced
fibrosis and an uncommon restrictive diastolic dysfunction. She had
suffered malignant arrhythmias several times and died of progressive
heart failure at the age of 30. In another patient, two polymorphisms
were found in intron 14 (base 18497C>G, base 18585C>T).
Conclusion: We have identified a novel TNNT2 gene mutation which
resulted in malignant ventricular arrhythmias and aborted SCD despite
a mild myocardial hypertrophy. The phenotype was consistent with the
previous data of TNNT2 gene mutations causing HCM published in the
literature earlier.
P0770. An A8296G mutation in mitochondrial tRNA Lys gene in a
patient with epilepsy; Pathogen or rare polymorphism?!
M. Ataei 1 , A. Ahadi 2 , M. Shafa Shariat Panahi 1 , M. Houshmand 1 , M. Sadeghizadeh
2 , K. Gharagozli 3 ;
1 National Institute for Genetic Engineering and Biotechnology(NIGEB), Tehran,
Islamic Republic of Iran, 2 Tarbiat Modaress University, Tehran, Islamic Republic
of Iran, 3 Shahid Beheshti University of Medical Science, Tehran, Islamic Republic
of Iran.
Mitochondrial DNA (mtDNA) mutations are important cause of human
diseases. A homoplasmic A8296G mutation was detected in a 24yr-old
man with idiopathic generalized epilepsy. He experienced his first seizure
at age 13. He suffers from deafness. His seizures begin suddenly
and without warning. He loses consciousness and experiences typical
generalized tonic or tonic-clonic seizures listing 1-5 minute each. The
A8296G mutation in the mitochondrial DNA tRNA Lys gene has been
associated with severe mitochondrial diseases in a number of reports.
The pathogenesis of this mutation or its association with a specific
disease is unclear. This mutation has been reported alone as well as
together with other mutations in trials in mtDNA. As in this case the
mutation was homoplasmic and there were no clinical finding in other
family members, we suggest that this mutation is rare polymorphism
or it acts as pathogen in combination with other mutations inside or
outside of the tRNA Lys.
P0771. Evaluation of MLPA in routine diagnostics for the
detection of subtelomeric rearrangements in 1040 patients with
idiopathic mental retardation
S. Drunat, A. Delahaye, A. Aboura, J. Rousseau, A. Verloes;
Robert Debré Hospital, APHP, Paris, France.
We screened 1041 patients with idiopathic Mental Retardation for subtelomeric
aberrations by a multi-step strategy consisting in 1) analysis
with the P036 MLPA kit assay, 2) confirmation with the P070 kit, 3)
verification by conventional FISH analysis.
79 rearrangements were detected by the P036 kit (7.6%). 48 (61%) of
them were confirmed by the P070 probes panel. 30 of this confirmed
rearrangements were verified by FISH analysis and 10 are still under
cytogenetic investigations.
Then, we focused on discrepancies between the P036 and P070 or,
MLPA and FISH results.
From the 31 rearrangements detected by the P036 kit, 13 could not
be found in a second experiment with the same kit, showing nonreproducibility
of the technique in about 1% of cases. When the 2
kits mapped the same locus and gave different results (11/31), the
imbalance detected was considered as a false positive reflecting the
20
sensitivity of the probe to a polymorphism. From the 48 imbalances
detected by the P036 kit and confirmed by P070, 7 were not verified
by FISH analysis. From the 7 FISH/MLPA and 7 P036/P070 discrepancies,
6 imbalances were detected in one parent of the patient and
therefore were not considered to be phenotype related. Real time PCR
was performed on the 8 discordant samples left. Aberrant copy number
detected by quantitative PCR confirmed MLPA analysis against
FISH findings for 6 of them.
MLPA is a sensitive, cost-effective technique for screening mentally retarded
patients which results must be validate by another cytogenetic
or molecular method.
P0772. Molecular Diagnosis of Immunodeficiencies Syndromes
A. Mori1 , R. Gershoni-Baruch1,2 ;
1 2 Institute of Human Genetics, Haifa, Israel, the Bruce Rappoport Faculty of
Medicine, Technion-Institute of Technology, Haifa, Israel.
Fourteen children with primary immunodeficiency diseases were investigated.
Clinical and family history data was recorded. A molecular
investigation, tailored to match the clinical diagnosis, was devised
for each patient independently. Five candidate genes, namely, BTK,
ITGB2, SLC35C1, UNG and WASP were screened in a multistep analysis,
including, PCR, RFLPs, DHPLC (denaturating high performance
liquid chromatography) and sequencing technology. Altogether, eleven
mutations were identified in ten patients, including five new unreported
mutations and six previously described.
Missense mutations detected in patients with LADI and LADII were
restricted to conserved sequences, in line with those previously reported.
A deletion encompassing two exons in BTK, no doubt disrupting
the structure of the protein caused a mild disease in our patient
with XLA but was otherwise lethal to other family members who died in
infancy. Two splicing mutations, which majorly disrupt the protein, were
identified in two WAS patients. In two of the four patients in whom no
mutations were detected, the diagnosis of HIGM syndrome was subsequently
revised. Genotype-phenotype correlation analyses in our
patients support several concepts. The notion that genetic diseases
and the immune response in particular, involve a complex interplay
between environmental and genetic factors is sustained. The mutations
contributing to LADI and LADII were restricted to conserved regions
thereby implicating that variations located in other regions do not
cause a disease. The view that the WAS phenotype, which may vary
from isolated thrombocytopenia to severe classic lethal immunodeficiency
is “mutation” dependent is confirmed.
P0773. The functional polymorphism -703T/C in the promoter
of the human IL gene is associated with atopic and non-atopic
bronchial asthma, but not with atopic dermatitis
M. Freidin 1 , E. Bragina 1 , O. Fedorova 2 , E. Nemerov 2 , L. Ogorodova 2 , V.
Puzyrev 1 ;
1 Institute of Medical Genetics, Siberian Branch of Russian Academy of Medical
Sciences, Tomsk, Russian Federation, 2 Siberian State Medical University,
Tomsk, Russian Federation.
Analysis of association between -703T/C polymorphism in promoter
of IL5 gene and atopic bronchial asthma (BA), non-atopic BA, and
atopic dermatitis (AD) was carried out by case-control study. It was
shown that -703C allele is associated with overexpression of the IL5
gene, probably, because of moving off the binding site for negative
regulator CLOX and therefore may predispose to atopic disease. Using
logistic regression analysis we found significant association of the
-703C allele both with atopic and non-atopic BA (p