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

Molecular and biochemical basis of disease
copy of the CFTR gene with a cystic fibrosis mutation in the other copy
is the most common cause of CBAVD in Persian population.
P0679. Molecular genetic diagnostics of celiac sprue from frozen
biopsy material and significance of multi-disciplinal cooperation
J. Simova, D. Markova, J. Dvorackova, I. Urbanovska, M. Cegan, D. Konvalinka;
CGB laboratory Ltd, Ostrava, Czech Republic.
Celiac disease (CD) is a multi-factorial disease characterised by a
lifelong abnormal immune response showing the features of an autoimmune
reaction to gluten, causing morphological changes in the
intestinal mucosa to occur in sensitive individuals. CD manifests itself
through various atypical symptoms and can be masked by a symptomatology
leading to a diagnosis of another disease. Prevalence range
from 1/200-1/300 individuals. The disease is closely associated with
HLA class II alleles. About 95 % of the persons with CD possess HLA
class II alleles DQA1*0501 and DQB1*0201/202 (coding heterodimer
DQ2) and DRB1*04 (in close relation with heterodimer DQ8).
The diagnostics of CD is currently based on assessment of clinical
symptoms, serologic tests, histological and enzymohistochemical examinations
of the duodena mucosa. The spectrum of diagnostic approaches
at our laboratory is supplemented with a molecular detection
of selected risk HLA alleles, which may substantially contribute
particularly to the differential diagnostics of infiltrative type CD (type
1 according to the Marsh´s modified classification), which occurs both
in CD-diagnose patients being on a gluten-free diet, CD-manifest relatives
(,,potential CD“) and Duhring-dermatitis-herpetiformis-diagnose
patients. The presence of risk HLA alleles was determined using the
PCR method.
The cooperation between pathologists and molecular geneticists substantially
contributes to vindicating the clinical diagnosis of CD, particularly
in cases unclear in histological terms as well as in potential
and latent forms of the disease. It makes possible to find other risk
individuals among the relatives of CD patients. The absence of these
examinations may result in a diagnostic unclearness.
P0680. Expression of Centa2 during early heart development:
a new candidate gene for the onset of cardiovascular
malformations
M. Venturin 1 , S. Brunelli 2,3 , G. Gaudenzi 4 , F. Cotelli 4 , P. Riva 1 ;
1 Department of Biology and Genetics for Medical Sciences, Medical Faculty,
University of Milan, Milan, Italy, 2 Stem Cell Research Institute, H. San Raffaele
Scientific Institute, Milan, Italy, 3 Department of Experimental Medicine, University
of Milano-Bicocca, Milan, Italy, 4 Department of Biology, University of Milan,
Milan, Italy.
We previously showed that cardiovascular malformations (CVMs), including
pulmonic stenosis, septal and valve defects, have a higher incidence
in patients (pts) with NF1 microdeletion syndrome, compared
to classical NF1 pts, likely owing to 17q11.2 region haploinsufficiency.
RT-PCR and Northern blot analysis of 9 genes within the NF1 deleted
region showed that Centa2, Suz12 and C17orf40 are expressed in human
fetal and mouse embryonic heart. In situ hybridization on mouse
whole embryos and sections allowed us to asses their expression pattern
during development. Centa2 was expressed in encephalon, gut,
otic vesicles, developing limbs and heart; in particular, a strong hybridization
signal was detected in heart at 9-9.5 dpc, when the heart tube
begins to loop and endocardial cushions, primordia of the valve leaflets
and membranous septa are forming; Centa2 expression in heart
continued until the last stage analyzed (15 dpc). Suz12 was found in
encephalon, pharyngeal arches and developing limbs, with a weak signal
in heart at 10 dpc. C17orf40 was expressed in otic vesicles, pharyngeal
arches and limbs, but not in heart. Preliminary results following
RT-PCR and in situ hybridization experiments on zebrafish showed
expression of Centa2 in adult heart.
These findings suggest that Centa2 might be involved in heart development
and in CVMs onset. Expression studies of Centa2 will be
extended to zebrafish embryos and immunohystochemistry with anti-
Centa2 antibodies on mouse sections will be performed to provide
further evidence on the involvement of Centa2 in heart development
and CVMs.
P0681. Clinical phenotype in a Portuguese patient with a
deletion of the entire coding region of the connexin 32 gene
R. Cerqueira1 , L. Lameiras1 , H. Gabriel1 , L. Negrão2 , A. Matos2 , P. Tavares1 , A.
R. Fernandes1 ;
1 2 CGC Centro Genética Clínica, Porto, Portugal, Serviço de Neurologia, Hospitais
da Universidade de Coimbra, Coimbra, Portugal.
X-linked Charcot-Marie-Tooth disease (CMTX) is a peripheral nerve
disorder that has been linked to mutations in the connexin 32 (Cx32)
gene (GJB1). Cx32 works as a gap junction protein found in myelinated
peripheral nerve and mutations in the protein are predicted to
interfere with the formation of functional channel in a dominant negative
manner. The majority of GJB1 mutations are missense mutations,
while a minority is nonsense mutations or small deletions. CMTX is
characterized by a moderate to severe motor and sensory neuropathy
in affected males, and usually mild to no symptoms in carrier females.
Here we report an 18 year old Portuguese male patient, with walking
difficulties, prominent muscular atrophy of muscles below the knee,
lower limbs with ‘invert champagne bottle’ appearance and with steppage
gait, associated with a deletion that, at least, eliminates the
Cx32 gene entire coding sequence. A few families with deletions of
the GJB1 gene have recently been reported [1,2]. This rare mutation
is described for the first time in a CMTX Portuguese patient. As in the
previous reported cases, the CMTX clinical phenotype of this patient is
similar to the ones associated with missense or nonsense mutations in
this gene. However, he has a complete absence of the Cx32 gene and,
therefore, a model of dominant negative inactivation of the function of
other gap junction does not apply, at least in this case.
[1] Nakagawa M. et al, J Neurol Sci. 2001, 185: 31-7
[2] Takashima H. et al, Acta Neurol Scand. 2003, 107:31-7
P0682. Mitochondrial Coupling Defect in Fibroblasts from
Patients with Mfn2-Related Charcot-Marie-Tooth Type 2a
D. Bonneau 1,2 , D. Loiseau 1,2 , A. Chevrollier 1,3 , C. Verny 4 , V. Guillet 1 , M. Poux 1 ,
Y. Malthièry 1,2 , P. Amati-Bonneau 1,2 , P. Reynier 1,2 ;
1 INSERM, U694, Angers, France, 2 Dept de Biochimie et Génétique, CHU,
Angers, France, 3 Dept de Biochimie et Génétique, Angers, France, 4 Dept de
Neurologie, CHU, Angers, France.
The mitofusin 2 gene (mfn2) encodes a dynamin GTPase, located
in the outer mitochondrial membrane, which is involved both in the
maintenance of the mitochondrial network and in the modulation of
cellular energy balance. Mutations of mfn2 may account for at least a
third of the cases of Charcot-Marie-Tooth disease type 2A (CMT2A).
In this study, we investigate mitochondrial cellular bioenergetics in
MFN2-related CMT2A. Methods: mitochondrial network morphology
and metabolism were studied in cultures of skin fibroblasts obtained
from four CMT2A patients harboring novel missense mutations of the
MFN2 gene. We studied intracellular reactive oxygen species, mitochondrial
membrane potential (ΔΨm), respiratory parameters, rate of
mitochondrial ATP synthesis and ATP/O ratio. Results and interpretation:
No alteration of the morphology of the mitochondrial network was
observed. In contrast, the mitochondrial energetic metabolism was
greatly altered in the fibroblasts from patients with MFN2 mutations.
We found a significant coupling defect leading to reduced OXPHOS
efficacy (reduction of ATP/O). However, this uncoupling did not lead
to a deficiency in ATP production since it was compensated by an increase
in the basal respiration. In other words, the ATP production was
maintained, although at a higher energetic cost. A 30% decrease of
the ΔΨm was also observed in fibroblasts patients as a direct consequence
of impaired mitochondrial coupling. These results suggest that
the sharply reduced efficacy of oxidative phosphorylation in MFN2related
CMT2A may contribute to the pathophysiology of the axonal
neuropathy.
P0683. Duplication of the Xq28 region including GDI and FLNA,
but not MECP2, in a family with moderate MR and ataxia
H. Van Esch1 , J. Vandewalle2 , E. Pijkels1 , P. Marynen2 , J. Fryns1 , G. Froyen2 ;
1 2 Center for Human Genetics, Leuven, Belgium, Center for Human Genetics
- Human Genome Laboratory - VIB, Leuven, Belgium.
The advent of new techniques such as array-CGH and MLPA has
led to the characterization of several new cryptic microdeletions and
duplications as the cause of mental retardation syndromes (MR). By
high resolution chromosome X specific array-CGH, we identified small
duplications of the MECP2 locus as the underlying cause of a distinct
1