2008 Barcelona - European Society of Human Genetics

Molecular and biochemical basis of disease
4 HUDERF, Hôpital Des Enfants Reine Fabiola, Brussels, Belgium, 5 Centre de
Génétique de Bruxelles, Free University of Brussels, Brussels, Belgium, 6 Department
of Ophthalmology, Ghent University Hospital, Ghent, Belgium.
LCA is genetically highly heterogeneous with the involvement of large
disease genes, which hamper genetic testing . The purpose of this
study was to determine the prevalence of mutations in 6 common LCA
genes in 108 LCA patients, mainly of Belgian origin, in order to optimize
a genetic screening strategy for LCA .
First, LCA chip screening revealed a mutation in 23% of all patients .
Second, direct sequencing of AIPL1, CRB1, CRX, GUCY2D, and
RPE65 revealed causal mutations in 4 .6% . Third, we performed targeted
mutation analysis of the CEP290 mutation c .2991+1655A>G .
We found this mutation in both homozygous (2/108) and heterozygous
(16/108) state. A second mutation was identified through sequencing
of the total coding region . Subsequently, the remaining patients were
screened for 4 additional recurrent CEP290 mutations . p .Lys1575X
was found in 3 .7% and c .[3310-1G>A;3310C>A] in 0 .9%, demonstrating
that c .2991+1655A>G is not present in all CEP290-related LCA
cases. A second mutation was identified in 3 cases; cDNA sequencing
is ongoing in the other ones . Finally, sequencing of the total coding
region of CEP290 is being performed in the remaining 39 cases . So
far, this revealed a homozygous mutation in one case .
In conclusion, we found mutations in 50% of all patients (22% in
CEP290; 15% in CRB1; 6% in RPE65; 3% in AIPL1; 2% in CRX and
2% in GUCY2D) . A combined genetic testing strategy consisting of
LCA chip analysis and targeted mutation screening of 5 recurrent
CEP290 mutations, represented an efficient first-pass screening, revealing
causal mutations in 44 .4% of our LCA population .
P05.114
Genetic study of tunisian patients with Leigh syndrome:
presence of the t8993G mutation in the mt-AtP6 gene and 2
new mutations in the mt-ND2 and mt-AtP8 genes
E. Mkaouar-Rebai 1 , W. Chaari 2 , S. Younes 3 , R. Bousoffara 2 , M. Sfar 2 , N. Belguith
1 , C. Triki 4 , F. Fakhfakh 1 ;
1 Laboratoire de Génétique Moléculaire Humaine. Faculté de Médecine, Sfax,
Tunisia, 2 Service de Pédiatrie. Hôpital Taher Sfar., Mahdia, Tunisia, 3 Service
de Neurologie. Hôpital Taher Sfar., Mahdia, Tunisia, 4 Service de Neurologie,
C.H.U. Habib Bourguiba de Sfax., Sfax, Tunisia.
Leigh syndrome (LS) is a genetically heterogeneous, neurodegenerative
disorder that predominantly affects children in early infancy or
childhood and leads to death within months or years . This disorder is
characterized by necrotic lesions in the brainstem, basal ganglia, and
thalamus . The symptoms are variable, but in most cases include psychomotor
retardation, optic atrophy, ataxia, dystonia, failure to thrive,
vomiting, seizures, and respiratory failure . Mutations causing Leigh
syndrome have been found in both mitochondrial and nuclear DNA .
Most of the described mitochondrial mutations were in ND3 and ND5
and a few ones were in ND6 and ND4 . In addition, there are single
case reports of mutations in synthetic genes such as tRNA Trp and
tRNA Lys genes . In the present study, we carried out a systematic sequence
analysis of mitochondrially encoded complex I subunits: ND2,
ND3, ND4, ND5 and ND6 in 16 Tunisian patients with Leigh syndrome .
We also performed a sequence analysis of the mitochondrial ATPase
6, tRNA Val , tRNA Leu(UUR) , tRNA Trp and tRNA Lys genes in these patients .
Mitochondrial DNA sequencing of these genes revealed the presence
of the T8993G mutation in the ATPase 6 gene in 1 patient belonging to
a Tunisian family with Maternally Inherited Leigh Syndrome (MILS) . In
this family, we also found 3 new mutations responsible for aminoacid
changes in a highly conserved region of the MT-ATP 6 protein . In addition,
we detected 60 known polymorphisms, 19 new nucleotide variants
and 2 novel mutations in 2 patients with Leigh syndrome in the
ND2 and in the ATPase 8 gene .
P05.115
A novel mutation of the lipoprotein lipase gene associated with
childhood hypertriglyceridaemia
S. Kalkan 1 , A. Alpman 2 , E. A. Arikan 2 , H. Akin 2 , M. Coker 1 , F. Ozkinay 2 ;
1 Ege University Medical Faculty, Department of Pediatrics, Subdivision of Metabolic
Disorders, Izmir, Turkey, 2 Ege University Medical Faculty, Department of
Medical Genetics, Izmir, Turkey.
Familial LPL deficiency is a rare autosomal recessive disorder that
affects about 1/1 .000 .000 children . Patients with classical lipoprotein
lipase deficiency present in the first several months of life with masked
hypertriglyceridaemia, often ranging between 5000 to 10 .000 mg/dl .
Hypertriglyceridaemia caused by decreased or absent Lipoprotein
lipase (LPL) activity is associated with increased blood lipoproteins .
LPL plays a functional role in regulation of the lipoproteins . To date,
approximately 140 mutations have been identified within LPL gene in
human genome . Most of the mutations are located within the coding
region of this gene . We performed DNA sequencing of 9 exonic regions
of LPL gene including promotor region of 10 patients with hypertriglyceridaemia
. We detected one novel homozygous missense mutation
that alters aminoacid at position 221 (I221T) . The homozygous mutation
causes the substitution of Isoleucine to Threonine at codon 221 in
exon 5. We evaluated the characteristic of patients, laboratory findings
and associated disorders. Treatment of patients with LPL deficiency
is difficult. Therefore, detection of mutations might be useful for better
therapy and prenatal diagnosis of the patients .
P05.116
Detecion and characterization of large rearrangements in the
SLC A gene in Lysinuric Protein intolerance patients
M. Font-Llitjós 1,2 , B. Rodríguez-Santiago 3,4 , M. Espino 1 , S. Mañas 1 , R. Sillué 1,2 ,
L. A. Pérez-Jurado 3,4 , M. Palacín 5,6 , V. Nunes 1,6 ;
1 IDIBELL, L’Hospitalet de Llobregat, Spain, 2 CIBERER-U730, Barcelona, Spain,
3 Universitat Pompeu Fabra, Barcelona, Spain, 4 CIBERER-U735, Barcelona,
Spain, 5 Parc Científic de Barcelona, Barcelona, Spain, 6 Universitat de Barcelona,
Barcelona, Spain.
Lysinuric protein intolerance (LPI) or hyperdibasic aminoaciduria type
2 (OMIM 222700) is a rare autosomal inherited disease, caused by defective
cationic amino acid transport 4F2hc/y + LAT-1 at the basolateral
membrane of epithelial cells in the intestine and kidney . LPI is a multisystemic
disease with a variety of clinical symptoms, such as osteoporosis,
hypotonia, growth delay, pulmonar insufficiency, or renal insufficiency.
LPI is diagnosed by the presence of excessive urine excretion
of dibasic amino acids, especially lysine, and by their poor intestinal
absorption that leads to low plasma levels of dibasic amino acids . The
SLC7A7 gene, which encodes the y + LAT-1 protein, is mutated in LPI
patients . Mutation analysis of the two promoters and all exons of the
SLC7A7 gene was performed in ten patients from nine unrelated LPI
families from different ethnic backgrounds . Point mutation screening
was performed by exon direct sequencing and a new multiplex ligation
probe amplification (MLPA) assay was set up for large rearrangement
analysis . Eleven SLC7A7 specific-mutations were identified in these
patients . Two out of seven novel mutations were large rearrangements
of the SLC7A7 gene .
This work was supported by The Spanish Ministry of Education and Science
(SAF2003-08940-01/02 and BFU2006-14600-C02-01/02/BMC),
The European Union (EUGINDAT; LSHM-CT-2003-502852), the Generalitat
de Catalunya (2006 SGR00018 and 2005 SGR00947) .
P05.117
Our methodical process of identification of Malignant
hyperthermia causal RYR1 mutations
I. Valášková1,2 , E. Flodrová1 , Š. Prášilová1 , P. Kuglík1,3 ;
1 2 University Hospital, Dept. of Medical Genetics, Brno, Czech Republic, Masaryk
University, Faculty of Medicine, Dept. of Biology, Brno, Czech Republic,
3Masaryk University, Faculty of Science, Dpt. of Experimental Biology, Brno,
Czech Republic.
Our work is focused on performing of an efective and relative inexpansive
molecular genetic diagnostic assay of malignit hyperthermia
(MH), life-threatening and frequently fatal disorder triggered by commonly
used anesthetics . Susceptibility to MH (MHS), dominantly inherited
predisposition to MH, is diagnosed by using an invasive diagnostic
test on excised muscle bundles, the in vitro contracture test (IVCT) . An
alternative diagnostic test to IVCT is mutation analysis of the ryanodine
receptor (RYR1) gene . RYR1 is an essential component of the calcium
homeostasis of muscles in mammals . Defects in the RYR1 gene in
humans (19q13 .1) are associated with MH . Until now, 29 RYR1 mutations
causing MH have been listed by European MH Group . A detection
of MH causative RYR1 mutations can be used as predictive
genetic testing. Our aim is to develop sufficient, effective and fast mutation-detection
procedures aimed at direct detection of MH causative
RYR1 mutations . To date we established molecular diagnostic assays
to detect RYR1 mutations using screening metods . Sequencing the