2009 Vienna - European Society of Human Genetics
2009 Vienna - European Society of Human Genetics
2009 Vienna - European Society of Human Genetics
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Molecular and biochemical basis <strong>of</strong> disease<br />
P16.36<br />
A novel connexin32 mutation cause X-linked charcot-marietooth<br />
disease in Belarus family<br />
T. Asadchuk, K. Mosse, N. Rumyantseva;<br />
National Center <strong>of</strong> Research and Applied Medicine «Mother and Child», Minsk,<br />
Belarus.<br />
The CMT1X is X-linked type <strong>of</strong> Charcot-Marie-Tooth disease, an inherited<br />
demyelinating neuropathy, associated with mutations in Cx32<br />
gene (GJB1) coding for the gap junction protein, connexin 32. The<br />
majority <strong>of</strong> GJB1 mutations are missense mutations.<br />
We report a family with asymptomatic mother and her two affected<br />
sons from different marriage. Males have severe motor and sensory<br />
neuropathy with walking difficulties, steppage gait, prominent muscular<br />
atrophy <strong>of</strong> muscles below the knee, distal weakness, sensory loss,<br />
and decreased tendon reflexes. The symptoms are revealed in their<br />
hands as well. Both brothers have shown clinical signs by the age <strong>of</strong><br />
10-11 years.<br />
At the first stage CMT1A was excluded by QF-PCR analysis <strong>of</strong> duplication<br />
in 17p11.2 region. Then direct DNA sequencing analysis <strong>of</strong> Cx32<br />
gene revealed a novel exon 2 (part 1) mutation identified in all three<br />
samples. Mutation c.149C>G in E1 extracellular domain resulted in a<br />
serine at codon 50 being replaced by cysteine (Ser50Cys). This substitution<br />
was not detected in healthy members <strong>of</strong> the family.<br />
For only 10% mutations in the GJB1 gene, family history <strong>of</strong> CMT1X<br />
disease is documented so far. New mutation is associated with severe<br />
phenotype and it’s analysis is crucial for CMT1X diagnosis and genetic<br />
counseling for probands and their relatives.<br />
P16.37<br />
A novel mutation in mFN2 gene in a patient with cmt type 2A<br />
M. T. Akbari1,2 , S. Zare Karizi2 , H. Nemat- Farahzadi2 , G. A. Shahidi3 , M. Karimipoor4<br />
;<br />
1Department <strong>of</strong> Medical <strong>Genetics</strong>, Tarbiat Modares University, Tehran, Islamic<br />
Republic <strong>of</strong> Iran, 2Tehran Medical <strong>Genetics</strong> Laboratory, Tehran, Islamic Republic<br />
<strong>of</strong> Iran, 3Iran Medical Sciences University, Tehran, Islamic Republic <strong>of</strong> Iran,<br />
44- Biotechnology Research Center , Pasteur Institute <strong>of</strong> Iran, Tehran, Islamic<br />
Republic <strong>of</strong> Iran.<br />
Charcot-Marie-tooth neuropathies (CMT) are a group <strong>of</strong> genetically<br />
heterogeneous disease <strong>of</strong> the peripheral nervous system. Ten different<br />
genes have so far been identified causing various subtypes <strong>of</strong><br />
CMT type 2. Mutations in the mit<strong>of</strong>usin 2 (MFN2) gene have been<br />
related to the axonal type <strong>of</strong> CMT2A. CMT2A is inherited in an autosomal<br />
dominant manner. The clinical phenotype is known to be severe<br />
and symptoms develop early. MFN2 gene encodes a mitochondrial<br />
GTPase protein. Here we report a MFN2 mutation in a CMT Iranian<br />
patient with late onset and mild phenotype. These features differ from<br />
what was expected. All exons <strong>of</strong> MFN2 gene were screened by direct<br />
sequencing and a de novo novel missense mutation was detected.<br />
This missense mutation, c.1574 A>G (N525S), is in exon 13 and the<br />
amino acid is located in the region between the transmembrane domain<br />
and the first coiled coil region <strong>of</strong> the polypeptide chain. To date,<br />
most <strong>of</strong> the mutations reported in MFN2 gene were missense mutations<br />
and most <strong>of</strong> them were located in the GTPase domain and the<br />
region linking the GTPase domain and the first coiled coil region.<br />
The effect <strong>of</strong> this mutation and the consequent amino acid change on<br />
the stability <strong>of</strong> the mit<strong>of</strong>usion 2 protein was studied by using Mupro<br />
(www.mupro.proteomics.ics.uci.edu) online s<strong>of</strong>tware, which predicted<br />
that this mutation decreases the structural stability by 94 % score.<br />
However, we feel further work; either functional or modeling studies<br />
are required to establish the actual effect <strong>of</strong> this mutation.<br />
P16.38<br />
mutation spectrum and genotype phenotype correlation for<br />
dynamin 2 gene in autosomal dominant centronuclear myopathy<br />
: from neonatal to adult forms.<br />
E. Schaefer 1 , C. R. Pierson 2 , A. Toussaint 3 , E. Taylor DeChene 2 , C. Poirson 3 ,<br />
C. Kretz 3 , A. Nicot 3 , J. Boehm 3 , N. Dondaine 1 , L. Bomme-Ousager 4 , V. Drouin-<br />
Garraud 5 , A. Echaniz-Laguna 6 , C. Jern 7 , H. Karasoy 8 , A. Krause 9 , B. Leheup 10 ,<br />
J. Melki 11 , L. Merlini 12 , A. Urtizberea 13 , C. Wallgren-Petterson 14 , E. Zanoteli 15 , J.<br />
Mandel 1,3 , A. Beggs 2 , J. Laporte 3 , V. Biancalana 1 ;<br />
1 Laboratoire Diagnostic Génétique et EA3949. Faculté de Médecine - CHRU,<br />
Strasbourg, France, 2 <strong>Genetics</strong> Division, Children’s Hospital Boston, Harvard<br />
Medical School, Boston, ME, United States, 3 IGBMC, Illkirch, France, 4 Odense<br />
University Hospital, Odense, Denmark, 5 Unité de Génétique Clinique, CHU<br />
Charles Nicolle, Rouen, France, 6 Département de Neurologie, Hôpital Civil,<br />
Strasbourg, France, 7 Sahlgrenska University Hospital/Östra, Göteborg, Sweden,<br />
8 Department <strong>of</strong> Neurology Ege, University Medical School Hospital, Izmir,<br />
Turkey, 9 National Health Laboratory Service (NHLS) & University <strong>of</strong> the Witwatersrand,<br />
Joannesburg, South Africa, 10 Unité de Génétique Clinique, CHU<br />
Brabois, Nancy, France, 11 Department <strong>of</strong> <strong>Human</strong> Gentics, Head, Hadassah<br />
University Hospital, Jerusalem, Israel, 12 Muscle Unit, Medical <strong>Genetics</strong>, University<br />
Ferrara, Ferrara, Italy, 13 Centre de Référence Maladies Neuromusculaires,<br />
APHP, Hôpital Marin d’Hendaye, Hendaye, France, 14 University <strong>of</strong> Helsinki and<br />
The Folkhälsan Institute <strong>of</strong> Gentics, Helsinki, Finland, 15 NIFESP-EPM, Sao<br />
Paulo, Brazil.<br />
Centronuclear (myotubular) myopathies (CNM) are characterized by<br />
muscle weakness and abnormal centralization <strong>of</strong> nuclei in muscle fibres.<br />
The severe neonatal X-linked form is due to mutations in the<br />
MTM1 gene. Mutations in the amphiphysin2 (BIN1) gene have been<br />
identified in autosomal recessive cases with childhood onset and moderate<br />
severity.<br />
Mutations in the Middle domain and in the Pleckstrin Homology (PH)<br />
domain <strong>of</strong> dynamin2 (DNM2) have been found in patients with autosomal<br />
dominant inheritance. Adulthood onset and mild severity are the<br />
common features in the majority <strong>of</strong> mutations. However some mutations<br />
are associated with neonatal onset. Whereas many mutations<br />
are localised in PH domain, this domain has also been found mutated<br />
in patients with dominant Charcot-Marie-Tooth neuropathy.<br />
We sequenced the DNM2 gene in 70 families with CNM, including 13<br />
families with dominant inheritance. We found mutations in 10 families<br />
with dominant inheritance and in 24 sporadic cases. These mutations<br />
included 21 missense in the Middle domain, 11 missense and 1 splice<br />
site deletion in the PH domain.<br />
These results confirm that a DNM2 defect is the main cause <strong>of</strong> adulthood<br />
form <strong>of</strong> CNM, but is also a significant cause <strong>of</strong> neonatal onset<br />
CNM, as we found 9 cases with this form mutated in exons 8 or 16 (de<br />
novo). Our study, concerning 34 new families, confirms the variability<br />
in onset and severity and supports a screening strategy based on hot<br />
spot mutations and genotype phenotype correlation.<br />
We will present the functional connections between the 3 known proteins<br />
mutated in CNM.<br />
P16.39<br />
Merosin-deficient congenital muscular dystrophy (MDC1A) in<br />
Russian patients.<br />
T. B. Tiburkova, O. A. Schagina, E. L. Dadaly, G. E. Rudenskaya, A. V.<br />
Polyakov;<br />
Research Centre for Medical <strong>Genetics</strong>, Moscow, Russian Federation.<br />
MDC1A (MIM 607855) is a severe autosomal recessive disorder<br />
caused by LAMA2 mutations. The gene encodes alpha-2 chain <strong>of</strong><br />
laminin, or else merosin. LAMA2 mutations produce complete or, less<br />
<strong>of</strong>ten, partial merosin deficiency. In <strong>European</strong> populations, MDC1A<br />
amounts to 30-50% <strong>of</strong> all congenital muscular dystrophies cases. DNA<br />
diagnostics <strong>of</strong> MDC1A is complicated by the gene large size and absence<br />
<strong>of</strong> major mutations. Though, by now, about 100 LAMA2 mutations<br />
were registered in MDC1A patients. Immunohistochemical detection<br />
<strong>of</strong> merosin in muscles is another diagnostic possibility. Four<br />
unrelated Russian patients with MDC1A presentation were examined<br />
for LAMA2 mutations by direct sequencing <strong>of</strong> all coding exons including<br />
exon-introns boundaries. In two patients, four mutations were detected.<br />
The genotypes were c.3829C>T/ c.7536delC, and c.5422C>T/<br />
c.7701delTinsGTGTCCCTAGGTGTCCCTA, two <strong>of</strong> the mutations are<br />
novel. The phenotypes were typical for ‘classic’ MDC1A, i.e. congenital<br />
muscular weakness with hypotonia, areflexia, and early contractures,<br />
high CPK level (700-1300 U/l), EMG signs <strong>of</strong> muscle lesion with concomitant<br />
hypomyelinating polyneuropathy, unspecific dystrophic pattern<br />
on muscle biopsy, and characteristic periventricular white matter<br />
abnormality on MRI. On follow-up to 4-6 years, the patients never<br />
walked and were severely disabled physically but showed no clinical<br />
signs <strong>of</strong> cerebral involvement. Two patients in whom mutations were<br />
not found may have extensive deletions undetectable by routine methods.<br />
These families need immunohistochemical MDC1A confirmation<br />
after which indirect DNA prenatal testing with STR-markers for 6q22q23<br />
region could be performed.