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

Molecular and biochemical basis of disease
P0774. IRF gene’s nucleotide sequence changes in patients
with nonsyndromic orofacial clefting from Lithuania
A. Morkūnienė 1,2 , L. Ambrozaitytė 1 , A. Utkus 1,2 , V. Kučinskas 1,2 ;
1 Vilnius University, Faculty of Medicine, Department of Human and Medical
Genetics, Vilnius, Lithuania, 2 Centre for Medical Genetics, Vilnius University
Hospital Santariškių Klinikos, Vilnius, Lithuania.
The hunt for the causes of nonsyndromic orofacial clefing (NS-OFC)
is extremely complex, involving multiple techniques that have been
used to identify numerous candidate genes in which disruption results
in increased risk of clefting. In recent years, a number of independent
groups have targeted for investigation the involvement of IRF6 (interferon
regulatory factor 6 gene). IRF6 is related to syndromic OFC - Van
der Woude syndrome.
Our study was aimed to investigate whether mutations in the IRF6
gene contribute to NS-OFC in the population of Lithuania.
Patients with NS-OFCs from Lithuania were tested for nucleotide sequence
changes in the IRF6 gene (206 patients). DNA fragments covering
exonic parts of the IRF6 gene were PCR-amplified and direct
sequenced.
23 different nucleotide sequence changes were revealed in the IRF6
gene by comparison of sequencing results with reference DNA sequences
of the genes. Scanning IRF6 gene resulted in ten novel
nucleotide sequence variants. Out of them, four were missense mutations
(p.S212I, p.L295P, p. Q340K, p.R400L), which, together with the
p.A61G mutation found in the case of Van der Woude syndrome, might
be related to the NS-OFC phenotype in the population of Lithuania.
Our study highlights the IRF6 gene sequence variability and supports
the hypothesis that variation in this gene contributes to NS-OFC phenotype
encouraging further investigations to test if IRF6 gene mutations
identified in the individuals from Lithuania are rare alleles causative
for NS-OFC.
P0775. The R176C amino-acid change in hemojuvelin as a
novel haemochromatosis mutation: phenotypic and functionanl
evidences
C. Ka 1 , G. Le Gac 1 , E. Letocart 1 , I. Gourlaouen 1 , L. Bryckaert 1 , B. Martin 2 , C.
Ferec 1 ;
1 Inserm, U613; Univ Bretagne Occidentale; Etablissement Français du Sang,
Brest, F-29200, France, 2 Etablissement Français du Sang, Niort, F-79000,
France.
Background: Juvenile haemochromatosis (JH) is an early-onset autosomal
recessive condition of iron metabolism caused by mutations in
either the hemojuvelin (HJV) or the hepcidin-encoding gene (HAMP).
The two JH gene products are implicated in a same physiologic process,
where hepcidin controls iron flow into plasma and hemojuvelin
enhances hepcidin expression at the transcriptional level via the classical
bone morphogenetic protein (BMP) cell signalling pathway. Aim
of the study and results: In this study, we report a novel missense
HJV mutation that leads to the replacement of arginine by a cysteine
residue at position 176 (R176C). We associate homozygosity for this
novel mutation with the iron overload phenotype observed in a 17year-old
girl. We also show that the HJV 176C mutated protein fails
to up-regulate the hepcidin promoter activity. Lastly, we suggest that,
due to its nature and position, the R176C amino-acid change prevents
an autocatalytic cleavage that normally occurs during HJV intracellular
processing. Conclusion: Our results definitively demonstrate that the
R176C substitution is a novel HJV loss-of-function mutation. They also
highlight that rapid advances in comprehension of the HJV intracellular
processing and function have paved the way for functional characterizations.
P0776. Early age at onset is the major clinical feature in
Parkinson disease related to PARK2 gene mutations
C. Cazeneuve 1 , C. San 1 , E. Lohmann 2 , S. Lesage 2 , E. Leguern 1,2 , A. Durr 3,2 , A.
Brice 4,2 , the Parkinson Disease Genetics Group;
1 Dpt of Genetics, Neurogenetics laboratory, Hospital Pitié-Salpêtrière, Paris,
France, 2 Institut National de la Santé et de la Recherche Médicale Unit U679,
Hospital Pitié-Salpêtrière, Paris, France, 3 Dpt of Genetics, Clinical Genetics,
Paris, France, 4 Dpt of Genetics, Hospital Pitié-Salpêtrière, Paris, France.
Autosomal recessive juvenile Parkinson disease (JPD) is characterized
by rigidity, bradykinesia, rest tremor, age at onset before 40 years,
good response to levodopa treatment, and slowly progressive disease.
Mutations in the parkin gene (PARK2) are the major genetic cause of
20
JPD.
To refine the clinical characteristics of the PARK2-associated JPD,
we investigated 77 patients referred to our diagnostic lab for PARK2
analysis.
Searching for point mutations by sequencing and for large rearrangements
by Multiplex Ligation-dependent Probe Amplification (MLPA kits
P051/P052, MRC-Holland) gave the following results:
Number
of PARK2
mutations
Presence of LRRK2
p.Gly2019Ser
mutation (detected
by the MLPA kits)
Number
of patients
Type of PARK2
mutations (P: point
mutation,
R: rearrangement)
2 no 15 19 R + 11P
Age at onset
: mean ±
2SD (range)
in years
24 ± 11
(17-35)
Molecular
diagnosis
of JPD
1 no 2 2 P (35-51) no
0 no 55
1 yes 2 2 P
36 ± 21
(3-53)
(43-not
available)
0 yes 3 37-54 no
The distribution of PARK2 genotypes (2, 1 or 0 mutation) differed dramatically
from Hardy-Weinberg equilibrium, strongly suggesting that,
for most patients with no identified PARK2 mutation, the phenotype is
independent from PARK2 gene rather than due to mutation in PARK2
unexplored regions.
Onset of disease was younger than 36 years in all the patients with
2 PARK2 mutations. However, PARK2-related JPD was established
in only 40% of patients with age at onset less than 36 years old. The
LRRK2 G2019S mutation was found in cases significantly older than
parkin cases. Patients presenting with 2 PARK2 mutations were clinically
indistinguishable from the others, according to the frequency
of rigidity, bradykinesia, tremor, positive response to levodopa, and
asymmetric onset.
Altogether, these results show that early age at onset is the major clinical
criteria for PARK2 molecular diagnosis of Parkinson disease.
P0777. Lamellar ichtyosis caused by TGM1 DNA mutation in a
Family from Azerbaijan
E. G. Okuneva, N. N. Vasserman, A. V. Polyakov;
Medical Genetics Research Center, Moscow, Russian Federation.
A case of autosomal recessive lamellar ichthyosis in two newborn
male sibs from consanguineous Azerbaijan family is presented. The
parents of the children are the first cousins. The first child was born in
the 34-th week of the pregnancy and died on the third day. The second
child was born in 37-th week and died on the first day. Both of them
had got the same clinical sign : tight shiny covering, described as collodion
membrane and erythroderma. During the first hour of life the
membrane is disrupted. They had got severe ectropion and eclabiun
too. There is no any biological material from the sibs, but the pariens
is caused by heterozygous mutations in 3-d exon of TGM1 gene P.142
Arg>His. The mutation of TGM1 gene is known to be responsible for
phenotypes of lamellar ichthyosis.
P0778. Spectrum of NPHP6 (CEP290) Mutations in Leber
Congenital Amaurosis and Delineation of the Associated
Phenotype
I. Perrault 1 , N. Delphin 1 , S. Hanein 1 , S. Gerber 1 , J. Dufier 2 , O. Roche 2 , H. Dollfus
3 , A. Munnich 4 , J. Kaplan 4 , J. Rozet 4 ;
1 Unité de Recherches Génétique et Epigénétique des Maladies Métaboliques,
Neurosensorielles et du Développement, INSERM U781, Paris, France, 2 Service
d’Ophtalmologie, Hôpital Necker, Paris, France, 3 Service de Génétique
Médicale, Hôpital Haute-Pierre, Strasbourg, France, 4 Unité de Recherches
Génétique et Epigénétique des Maladies Métaboliques, Neurosensorielles et
du Développement, INSERM U781, PARIS, France.
Mutations in the NPHP6 gene were shown to account for Joubert syndrome
and Senior-Loken syndrome as well as Leber congenital amaurosis
(LCA). All reported patients affected with LCA carried an intronic
mutation resulting in an aberrantly spliced transcript and low levels of
wild-type transcript that was believed to explain the absence of cerebellar
and renal involvement in LCA patients. The aim of the present
study was to give the survey of NPHP6 mutations in our series.
192 unrelated LCA cases were screened for mutations. The natural
history and ophthalmologic data were reviewed for all patients har-
yes
no
no