2008 Barcelona - European Society of Human Genetics

Molecular and biochemical basis of disease
P05.062
Duplication of exons 1 to 22 of the F gene: a new mechanism
related to multiple copies of the intron 22 int22h sequence?
C. Costa 1,2 , E. Bieth 3 , P. Boisseau 4 , S. Letourneau 1 , F. Dastot 1,2 , E. Girodon-
Boulandet 1,2 , M. Goossens 1,2 ;
1 AP-HP, Groupe Henri Mondor-Albert Chenevier, Laboratoire de Génétique Moléculaire,
Créteil, France, 2 INSERM U841, Département de Génétique, équipe
11, Université Paris 12, Créteil, France, 3 Hôpital Purpan, Laboratoire de Génétique
Médicale, Toulouse, France, 4 CHU Hotel Dieu, Service de Génétique
Médicale, Laboratoire de Génétique Moléculaire, Nantes, France.
Interspersed repeats account for 56% of the euchromatic X chromosome
sequence, compared with a genome average of 45% . Intrachromosomal
duplications are estimated to account for 2 .59% of the X
chromosome while interchromosomal duplications account for a very
small fraction 0 .24% of the X chromosome . Among these duplications
are well-described cases that are associated with genomic disorders .
Some disorders may result from rearrangements involving duplicated
sequences in Xq28, such as in haemophilia A . In severe haemophilia A,
mutations are frequently the results of inversions between a sequence
in intron 22 (int22h-1) of the F8 gene and one of two more distally
located copies (int22h-2, int22h-3) described to be in the same orientation.
Recently a novel finding from analysis of the DNA sequence
of the human X chromosome (Ross et al, Nature 2005) has revealed
that the two distal copies are in opposite orientations . Recombination
should then produce deletion or duplication rather than inversion . A
deletion consistent with this prediction has been reported in a family
in which carrier females are affected by a high spontaneous-abortion
rate in pregnancy. We report here the first case of duplication of exons
1 to 22 in a carrier female in a family were none haemophiliac patient
was available . The duplication was detected by MP-LC (Multiplex Liquid
chromatography) and confirmed by MLPA. We believe this new
rearrangement could be linked to the multiple copies of the intron 22
sequences and would confirm the hypothesis that recombination could
produce duplication .
P05.063
A comparison of quantitative real time PcR (Q-Rt-PcR) and
Multiple Ligation-Dependent Probe Amplification (MLPA) for
molecular diagnosis of deletions in cases of severe haemophilia
A
A. Venceslá, M. Baena, M. J. Barceló, J. Juan, L. Alias, M. Cornet, M.
Domenech, P. Gallano, M. Baiget, E. F. Tizzano;
Hospital Sant Pau, Barcelona, Spain.
Haemophilia A (HA) is an X-linked bleeding disorder caused by mutations
in coagulation factor VIII. The identification of HA carriers is an
essential part of genetic counselling . Large rearrangements frequently
occur within the F8 gene in severe haemophiliacs . These include the
intron22 inversion (40-45%) the intron1 inversion (2-5%) and gross
deletions encompassing one or more exons (5-10%) . Although gross
deletions are readily detectable in males, the identification of heterozygosity
in possible carriers of these families constitutes a challenge .
To identify a deleted allele over the background of the normal allele in
these carriers, we previously set up a Q-RT-PCR method employing
LightCycler technology . A comparison was performed with the recently
described MLPA P178 FVIII probemix that contains probes for each
of the 26 exons of the F8 gene . We studied patients with deletions in
exon 13, in exons 23-25, in exon 15 and in exons 1-22 . Carrier and
non-carrier females from these families previously defined by quantitative
or marker analysis were also tested . MLPA results in HA patients
revealed the absence of the peak in the corresponding exon(s) . There
was a complete correlation with results in the carrier group (one copy
of the corresponding exon(s) by Q-RT-PCR and 40- 55% of reduced
relative peak area in MLPA) and also in the non carrier group (two
copies and 85-100% of peak area) . MLPA may be incorporated into
routine molecular diagnosis of severe HA after screening of inversions .
Supported by Fundació Catalana d´Hemofilia, CIBERER, Real Fundación
Victoria Eugenia.
P05.064
investigation of human mitochondrial DNA in iranian
Hypertrophic cardiomyopathy (Hcm) patients
M. Montazeri 1 , M. Houshmand 1 , E. V. Zaklyazminskaya 2 ;
1 NRCGEB, Tehran, Islamic Republic of Iran, 2 Russian Research Center of
Medical Genetics Laboratory of DNA Research, Mosque, Russian Federation.
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 .
P05.065
investigation of 69 common mutations in MYH gene in iranian
population with hypertrophic cardiomyopathy
M. Montazeri1 , M. Houshmand1 , M. Ghani Kakhki1 , G. Estahbanati2 , M. M.
Peyghambari3 , E. V. Zaklyazminskaya4 ;
1 2 nrcgeb, Tehran, Islamic Republic of Iran, Iran University of Medical Sciences
Shaheed Rajaie Cardiovascular Medical Center, Tehran, Iran, Tehran, Islamic
Republic of Iran, 3Iran University of Medical Sciences Shaheed Rajaie Cardiovascular
Medical Center, Tehran, Iran., Tehran, Islamic Republic of Iran,
4Russian Research Center of Medical Genetics Laboratory of DNA Research,
Moscow, Russia., Moscow, Russian Federation.
Hypertrophic cardiomyopathy is characterized by hypertrophy of
ventricles and intrventricular septum . Patients could develop serious
complications including heart failure, arrhythmias and sudden death .
Familial hypertrophic cardiomyopathy is a single gene disorder and
has autosomal dominant inheritance . In this study we focused on
exons 13-15 and 19-21 of MYH7 gene and introns located between
them, which contain hotspots for so called “malignant mutations” that
increase sudden cardiac death risk . Methods: Fifty unrelated Iranian
patients with hypertrophic cardiomyopathy were selected sequentially
and informed written consent was obtained from them . Exons 13-15
and 19-21 of MYH7 gene and their related introns were amplified by
polymerase chain reaction . Then PCR products were sequenced . Results:
Mutations were detected in fourteen (28%) of the patients . We
didn’t find any malignant mutation, but three mutations were found in
targeted exons . One of them, A10419C (N444T) in exon 14, may be
a novel mutation .
P05.066
A novel mitochondrial DNA tRNAile (m.4322dupc) mutation
associated with idiopathic dilated cardiomyopathy
S. Mahjoub 1 , D. Sternberg 2 , R. Boussaada 3 , S. Filaut 2 , F. Guemira 4 , R. Mechmech
3 , C. Jardel 2 , S. Ben Arab 1 ;
1 Faculté de Médecine de Tunis, Tunis, Tunisia, 2 Fédération de génétique-UF
Cardio et Myogénétique , Hôpital Pitié-salpétrière, Paris, France, 3 Hôpital La
Rabta, Tunis, Tunisia, 4 Hôpital Salah Azaiez, Tunis, Tunisia.
Dilated cardiomyopathy (DCM) is a heart muscle disease characterized
by cardiac dilatation and impaired contraction of the left ventricle
(LV) or both ventricles . The age at disease onset is highly variable,
ranging from early childhood to late adulthood . Only 50% of patients
with DCM survive >5 years after diagnosis . Approximately 20% to 25%
of cases seem to have a genetic component . DCM can be transmit-