2009 Vienna - European Society of Human Genetics

Molecular basis of Mendelian disorders
P12.111
Recessive congenital methaemoglobinaemia type ii: a novel
mutation in the NADH-cytochrome b5reductase gene in a
Russian patient
N. Galeeva, A. Polyakov;
Research Centre for Medical Genetics, Moscow, Russian Federation.
Hereditary methemoglobinemia is an autosomal recessive disorder is
caused by NADH-cytochrome b5 reductase (cytb5r) deficiency. Two
forms of cytb5r are known, a soluble form and a membrane-bound
form, and are localized in different cellular compartments. Hereditary
methemoglobinemia has been classified into two types, an erythrocyte
type (type I) and a generalized type (type II). Type 1 is characterized
clinically by a single symptom, cyanosis, and biochemically by a
deficiency of the red cell-soluble form of the enzyme. In type II, the
cyanosis is accompanied by neurological impairment, mental retardation
and reduced life expectancy. Type II is characterized by deficiency
the soluble and the membrane-bound forms of the enzyme in various
tissues of patients. The cytb5r gene (DIA1) is 31-kb long, contains 9
exons, and has been localized to chromosome 22q 13-qter.
We have investigated family with methemoglobulinemia type II from the
Chechen Republic of the Russian Federation. There were 5 children
in this family. First, second and fourth child was not affected. Third and
fifth child suffered from cyanosis and neurological impairment. Third
child dead at the age of four years. We have investigated fifth child at
the age of 6 month and found a novel mutation (c.339insC) in exon 5
of the gene DIA1 in homozygote. This insertion leads to appearance
premature stop codon.
P12.112
improved molecular diagnostics for patients with respiratory
chain complex deficiency
M. Biste 1 , F. Madignier 1 , P. Freisinger 2 , B. Rolinski 3 , J. Mayr 4 , M. Tesarova 5 , R.
Horvath 3 , W. Sper 4 , T. Meitinger 1 , H. Prokisch 1 ;
1 Technical University of Munich, Institute of Human Genetics, München,
Germany, 2 Technical University of Munich, Stoffwechselzentrum Kinderklinik,
München, Germany, 3 Klinikum München GmbH, Medizet-Stoffwechselzentrum,
München, Germany, 4 Universität Salzburg, Kinderklinik, Salzburg, Austria, 5 Universität
Prag, Department of Pediatrics, Prag, Czech Republic.
Aim: Isolated respiratory chain complex I (RCCI)-deficiencies are the
most common form of mitochondrial diseases (round 25%). Clinically,
the patients present a heterogeneous spectrum which can be multisystemic
(e.g. neonatal lactic acidosis, Leigh syndrome) or with distinct
symptoms (e.g. ataxia, myopathy). RCC I is composed of 45 different
subunits. The high number of genes involved is making the search for
the molecular basis of RCCI deficiency difficult. In routine diagnostics
the causal mutations can be identified in less than 10% of the pediatric
patients with RCCI-deficiency.
Methods: A high-throughput molecular genetic screen for the RCCI
encoding genes was established. 92 families with isolated RCCI-deficiency
and previous exclusion of common mtDNA mutations were
investigated by DNA melting profile analysis using an Idaho LightScanner.
To analyze genotype-phenotype correlations a clinical questionnaire
was developed based on the guidelines issued by the working
group on pediatric metabolic disorders.
Results: We have screened 59 genes coding for the subunits and assembly
factors of RCCI. Causative mutations have been identified in
16% of patients which were inconspicuous in routine diagnostics. A
single variant was identified in 30% of additional samples and in 54%
of samples no mutations have been found yet. The analysis shows
typical clinical patterns correlated with mutations in specific genes.
Conclusion: Molecular genetic diagnostics of RCCI-deficiency was improved
and prenatal diagnostics can be offered. Genotype-phenotype
correlations will enable more efficient diagnosis and allow predictions
on disease course.
P12.113
A novel mutation in the mitochondrial AtPase 8 gene in a patient
with leukodystrophy
E. Mkaouar1 , F. Kammoun2 , I. Chamkha1 , I. Hsairi2 , C. Triki2 , F. Fakhfakh1 ;
1 2 Laboratoire de genetique moleculaire humaine, Sfax, Tunisia, Service de
Neurologie Infantile, C.H.U. Hédi Chaker de Sfax,, Sfax, Tunisia.
Mitochondrial DNA defects were known to be associated with a wide
spectrum of human diseases and patients might present with a wide
range of clinical features in various combinations. In the present
study, we described a patient with a form of leukodystrophy showing
psychomotor and neurodevelopmental delay, mild hyperintensity of
posterior periventicular white matter, spastic paraplegia, generalized
clonic seizures and congenital deafness. He also suffered from a severe
tetraplegia, with central blindness and swallowing difficulty. Brain
MRI showed involvement of the interpeduncular nucleus and central
tegmental tract, white matter abnormalities and cerebellar atrophy. A
whole mitochondrial genome screening in this patient revealed the
presence of 19 reported polymorphisms and an undescribed A to G
heteroplasmic mutation at nucleotide 8411 (M16V) affecting a highly
conserved region of the mitochondrial ATPase 8 protein. This mutation
could be associated to the disease in the tested patient who belongs
to haplogroup U.
P12.114
molecular genetic exploration-diagnostic tool for chronic
granulomatous disease. case report
M. Serban 1 , M. Bataneant 1 , C. Jinca 1 , D. Mihailov 1 , M. Puiu 1 , L. Dehelean 1 , L.
Morodi 2 ;
1 University of Medicine and Pharmacy “Victor Babes” Timisoara, Romania, Timisoara,
Romania, 2 Department of Infections and Pediatric Immunology, Medical
and Health Science Center, University of Debrecen, Debrecen, Hungary.
Introduction: Chronic granulomatous disease (CGD) is a heterogeneous
congenital immunodeficiency characterized by a profound
defect in the burst of oxygen consumption. Beside the genuine CGD
there are a lot of CGD-like syndromes, therefore a molecular genetic
investigation is mandatory for a definite diagnosis, decisive for an appropriate
therapeutical decision.
Case presentation: We present the case of a 8 years old boy with a
history of recurrent episodes of fever, adenophlegmones and pulmonary
infections since the age of 3 weeks. Hepatosplenomegaly as well
as pulmonary and vertebral aspergillosis with destruction of thoracic
vertebrae D5-D7 characterized the clinical picture at admittance in
our hospital. The suspicion of X-linked CGD was confirmed by absent
respiratory burst and the presence of the genetic mutation (4. exon,
c.271C>T, p.R91X). Despite prolonged therapy, the patient continued
to present pulmonary and vertebral aspergillosis. Due to the presence
of an HLA-compatible brother, matched related PBSCT was performed
under continuous antifungal treatment. Chimerism analysis showed
complete donor chimerism of granulocytes, monocytes, NK cells and
CD19 lymphocytes and 85% and 96% donor chimerism of CD4 and
CD8 lymphocytes respectively. Respiratory burst performed showed
significant improvement. At 7 months after the HSCT, under antifungal
maintenance therapy, the patient is in good clinical condition with full
donor chimerism and significantly improved radiologic findings on the
chest x-ray.
Conclusion: Molecular genetic exploration proved the diagnosis of
CGD in our case. Its genetic marker 4 exon, c.271C>T, p.R91X was
clinically expressed in a life-threatening infection, justifying a successfully
undertaken hematopoietic stem cell transplantation.
P12.115
molecular mechanism underlining genetic defects in
incontinentia Pigmenti
M. Paciolla1 , A. Pescatore1 , F. Fusco1 , J. Gauteron2 , M. G. Miano2 , G. Courtois2
, M. V. Ursini1 ;
1Institute of Genetics and Biophysics “Adriano Buzzati Traverso” CNR, Naples,
Italy, 2INSERM U781 Hôpital Necker-Enfants Malades, Paris, France.
Incontinentia Pigmenti (IP) is an X-linked dominant genodermatosis,
lethal in male, caused by mutations in the Xq28 NEMO gene. NEMO is
the essential subunit of the kinase complex IKK, required for the activation
of NF-κB canonical pathway. The most frequent IP mutation (80%)
is a recurrent genomic exons 4-10 NEMO deletion. In addition, about
39 small mutations scattered along NEMO, have been reported.
In order to unravel molecular mechanism that underlines the alteration
of NF-κB activation in the pathology, we performed an analysis of
the NEMO mutations associated to severe forms of IP. In particular,
we demonstrated that the A323P presents an impairment of (K63-)
polyubiquitination, which resulted from a detective interaction with
TRAF6. This analysis allowed us to define the critical lysines residues
of NEMO, target of TRAF6, that are required for proper response to
multiple NF-κB activation signals, such as IL-1 and LPS. Starting from