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

Genetic analysis, linkage, and association
that carrying of particular mtDNA haplogroup may have some impact
on energetic processes and may be a predisposition factor for arterial
hypertension and its complications. The work was supported by partial
support of Russian Foundation for Basic research (RFBR) grants 04-
04-48792, 04-04-48732, 06-04-08326.
P1033. Mitochondrial DNA depletion syndrome
S. Seneca 1 , I. Liebaers 1 , L. Van Haute 1 , R. Van Coster 2 , J. Smet 2 , G. Van
Goethem 3 , A. Löfgren 4 , J. Jaeken 5 , M. Nassogne 6 , B. François 7 , L. Diogo 8 , W.
Lissens 1 , A. Meulemans 1 , L. De Meirleir 9 ;
1 UZ Brussel, Center for Medical Genetics, Brussels, Belgium, 2 UGent, Pediatric
Neurology & Metabolism, Ghent, Belgium, 3 University of Antwerp, Department
of Neurology and Neuromuscular Reference Center, Antwerp, Belgium, 4 University
of Antwerp, Department of Molecular Genetics-VIB, Antwerp, Belgium,
5 University of Leuven, Department of Pediatrics, Leuven, Belgium, 6 Saint-Luc
Academic Hospital, Departments of Pediatrics, Brussels, Belgium, 7 Clinique de
l’Espérance, Pinocchio Centre, Montegnée, Belgium, 8 Hospital Pediatrico, Unidade
de Doenças Metabolicas, Coimbra, Portugal, 9 UZ Brussel, Department of
Pediatric Neurology, Brussels, Belgium.
The mitochondrial genome (mt) is a small (16.5kb) DNA molecule that
is normally present in multiple copies in individual mitochondria. MtDNA
depletion syndrome (MDDS) is a recently recognized disorder involving
a quantitative defect of mtDNA, that is inherited in an autosomalrecessive
mode. The patients are born after an uneventful pregnancy
and often normal at birth, but deteriorate in the neonatal period or early
childhood. There are two main clinical presentations : myopathic and
hepatocerebral. In the first group children usually present with devasting
myopathy and neurological abnormalities. In the second condition
patients suffer from early progressive hepatic failure with hypotonia,
hypoglycaemia, lactic acidosis and progressive neurodegeneration as
described in Alpers syndrome. We used real-time PCR techniques to
quantify the level of mtDNA in fibroblast, blood, and muscle or liver tissue
of patients suspected clinically and on the basis of the biochemical
data. Of all patients clinical presentation of MDDS, mtDNA depletion
was documented in ten. Molecular analysis of known nuclear mutant
genes was undertaken and the exons of the TK2, DGUOK and polG
genes were sequenced. In two patients DGUOK gene mutations were
revealed, while in four other patients recessive polG mutations were
seen. It is known that mutations in these genes count only for a fraction
of MDDS cases. Recently mutations in two other nuclear genes,
SUCLA and MPV17, segregating with mtDNA depletion were identified
in patients with MDDS.
P1034. Myosin IXB: Initial evidence for association to multiple
sclerosis in Finnish MS study sample
A. Kemppinen 1,2 , M. Daly 3 , A. Palotie 4 , J. Saarela 1,2 , L. Peltonen 1,2 ;
1 Dept of Molecular Medicine, National Public Health Institute, Helsinki, Finland,
2 Research Program in Molecular Medicine at Biomedicum Helsinki, Helsinki,
Finland, 3 Medical and Population Genetics Program, Broad Institute of MIT
and Harvard, Cambridge, MA, United States, 4 Finnish Genome Center, Univ of
Helsinki, Helsinki, Finland.
Multiple sclerosis (MS) is a chronic inflammatory disease with a distinct
autoimmune component affecting the myelin of CNS. Our group
has previously identified MS-associated allelic haplotypes of the gene
encoding protein kinase C alpha (PRKCA) in Finnish and Canadian
populations. In vitro evidence suggests that PRKCA is a downstream
target of RhoA in a pathway regulating blood brain barrier permeability.
In this pathway, RhoA is regulated by myosin IX class proteins,
of which MYO9B was recently associated with two autoimmune diseases,
celiac disease and inflammatory bowel disease.
We genotyped 21 single nucleotide polymorphisms (SNPs), covering
the MYO9B gene, in the nationwide collection of 970 Finnish MS families.
Two SNPs (rs17533945 and rs12986130), located 22 kb apart
in introns 2 and 10, provided evidence for linkage (Pseudomarker,
Linkage p-values 0,0004 and 0,001, respectively). rs12986130 also
showed evidence for association assuming linkage in a set of families
stratified based on the PRKCA haplotype (Pseudomarker LD assuming
Linkage p-value 0,001; Gamete competition p-value 0,002).
The results lend support to our hypotheses that PRKCA and MYO9B
may operate in the same biological pathway, potentially relevant for
the disease pathogenesis of MS. The replication effort is ongoing in
217 MS trios and 3000 case-control samples from Denmark, Sweden
and Norway.
P1035. Sequencing: a time consuming but robust highway to
multifactorial diseases associated polymorphisms
I. Cournu-Rebeix1 , M. C. Babron2 , E. Genin2 , L. Guillot-Noël1 , F. Clerget-Darpoux2
, B. Fontaine1,3 ;
1 2 INSERM UMRS546, Paris, France, INSERM UMRS535, Villejuif, France,
3Univ P et M Curie, Paris, France.
The HapMap project has characterized sets of Single Nucleotide polymorphisms
(SNPs) to be picked for disease association studies. However,
divergence of opinion still exists on how to optimise the selection
of markers to capture the genetic variation underlying complex traits.
Cytokine gene polymorphisms are known to influence susceptibility
and disease course of many autoimmune diseases. Interleukin 4 (IL4),
Interleukin 13 (IL13) and their receptor (IL4R) have been partially investigated
as candidate genes for MS by linkage and association studies
with contradictory results.
In order to perform an exhaustive investigation of Il4-IL13 cluster and
IL4R gene polymorphisms in susceptibility to MS we sequenced the
complete region of each gene (promoter, exons and introns), in collaboration
with the National Center of Sequencing (Evry, France) in
128 MS trio families.
Among the 145 SNPs within the IL13-IL4 cluster, 63 were newly identified
by our study. Note that 54 previously reported SNPs were monomorphic
in our sample. Using pairwise linkage disequilibrium (LD) we
determined that 93 SNPs would need to be genotyped to represent
the 145 SNPs with r2=0.8. Concerning IL4R gene, 71 sites were newly
identified, 44 previously reported are not polymorphic in our sample,
leading to a total of 157 SNPs which can be tagged by 74 SNPs.
Comparison with the tags proposed by HapMap is in progress. Preliminary
results show that at least 10 of the 43 common SNPs of the
IL13-IL4 cluster would not have been tagged if markers were selected
based on the HapMap CEU data.
P1036. Investigation of the IL4-IL13/IL4R pathway in French
Multiple Sclerosis patients
M. C. Babron 1,2 , E. Génin 1,2 , I. Cournu-Rebeix 3,4 , H. Perdry 1,2 , F. Clerget-Darpoux
1,2 , B. Fontaine 3,5 ;
1 INSERM U535, Villejuif, France, 2 Univ Paris Sud, Villejuif, France, 3 INSERM
U546, Paris, France, 4 Univ Pierre et Marie Curie 6, Paris, France, 5 Fédération
de Neurologie- Hop de la Pitié-Salpêtrière, Paris, France.
Multiple Sclerosis (MS) is a multifactorial disease, in which genetic
and environmental factors intervene. Apart from HLA, little is known
on the other genetic factors involved. Two genome scans [Broadley et
al, 2001; Babron et al, 2004] suggested the presence of a risk factor in
the chromosomal region 5q31. The location of the IL4 and IL13 genes,
coding for cytokines involved in the immune response, in this region
makes them good candidates for susceptibility to MS. Previous studies
on type I diabetes, another autoimmune disease have suggested
interactions between IL4/IL13 and their receptor IL4R [Bugawan et al,
2003].
We investigated the role of this pathway in a sample of 124 French
trios (an affected child and his two parents). Sequencing of all the individuals
allowed identification of a total of 249 SNPS. Among them,
14, 23 and 86 for IL13, IL4 and IL4R, respectively, had a minor allele
frequency greater than 1%. None of these, taken individually, showed
significant association with MS.
However, in multifactorial diseases such as MS, combinations of two
or more variants in the same pathway may be involved. Thus, as proposed
by Jannot et al [2003], we investigated combinations of two
variants, one in IL4 or IL13 and one in IL4R. Among the 3219 combinations
tested, 12 were significant at the nominal 1% level, and were
more significant than each SNP analysed separately. These combinations
will need to be tested in independent samples for replication.
We thank REFGENSEP for data sharing and ARSEP for funding.
P1037. A Multiple Imputation approach to test the role of
the CD28-CTLA4-ICOS gene cluster in Multiple Sclerosis
susceptibility
P. Croiseau 1,2 , M. Alizadeh 3 , M. Babron 2,1 , F. Clerget-Darpoux 2,1 , G. Semana 3 ,
E. Génin 2,1 ;
1 Univ Paris-Sud, UMR-S535, Villejuif, F-94817, France, 2 INSERM, Villejuif, F-
94817, France, 3 UPRES EA 1257, Faculté de médecine, Rennes, France.
Genes involved in Multiple Sclerosis (MS) are difficult to identify because
of their small effect and their possible interaction with other
2