2009 Vienna - European Society of Human Genetics

Molecular basis of Mendelian disorders
common form of the disease, and is caused by a deficiency in the
cytosolic protein phosphomannomutase (EC 5.4.2.8, PMM 2). The aim
of this work has been the functional analysis of 12 missense changes
identified in a cohort of Spanish patients in order to provide clues to understand
the phenotype-genotype correlation and to investigate new
therapeutic approaches. First we have studied the PMM2 protein stability
and gene expression in the fibroblast cell lines. All fibroblasts cell
lines presented lower amount of PMM2 mutant protein while no effect
on mRNA stability was detected. The prokaryotic in vitro studies have
demonstrated that all new changes are disease-causing mutations and
have revealed the presence of null mutations (R123Q, R141H, F157S,
P184T, F207S and D209G), mutations with residual activity ranging
between 44-54% (L32R, T118S, T237M and P113L) and mutations
with residual activity ranging between 16-21% (D65Y and V44A). Most
of the patients are functional hemyzygous for a null mutation and a
mutation with intermediate residual activity -usually associated with a
moderate form of the disease- or with a mutation with higher residual
activity usually associated with a milder clinical phenotype. The protein
stability assays identified at least six changes (V44A, D65Y, F157S,
P184T, F207S and T237M) with decreased amount of immunorreactive
PMM2 protein and decreased half life compared to wild type,
opening up therapeutic possibilities by pharmacological chaperones in
several of our cohort of patients.
P12.029
HLA polymorphism in celiac disease Romanian children
O. N. Belei 1 , I. Simedrea 1 , L. Tamas 2 , C. Daescu 1 , T. Marcovici 1 , F. Antonie 3 , G.
Brad 3 , D. Mihailov 4 ;
1 First Pediatric Clinic, University of Medicine and Pharmacy “Victor Babes”,
Timisoara, Romania, 2 Biochemistry Departement, University of Medicine and
Pharmacy “Victor Babes”, Timisoara, Romania, 3 Emergency Children Hospital
Louis Turcanu, Timisoara, Romania, 4 Third Pediatric Clinic, University of Medicine
and Pharmacy “Victor Babes”, Timisoara, Romania.
Introduction: Celiac disease (CD) is an immune-mediated enteropathy
caused by a permanent sensitivity to gluten in genetically susceptible
individuals (DQ2 or DQ8 HLA haplotype). Objective: To correlate the
clinical forms of CD with villous injury severity, IgA anti-tissue transglutaminase
(tTG) antibodies serum level and DQ2 / DQ8 haplotype.
Material and Methods: We recruited 2 lots: lot 1 - 24 children diagnosed
with CD by mass screening in subjects associating risk factors
and lot 2 - 24 healthy controls matched with sex and age. HLA DQ2
and DQ8 alleles were typed by PCR-SSP, IgA tTG assessment was
made using ELISA and villous injury was classified using Marsh score.
Results: From 24 CD patients, 15 associated atypical or silent form
of disease and only 9 associated the typical form. Haplotype analysis
showed that the main combination observed was DQ2 in cis conformation
(DQA1*0501 and DQB1*0201 alleles) in 14 patients from lot
1 and in one subject from lot 2. We found a strong correlation between
IgA tTG serum level and villous injury degree (p=0,03), but there
was no statistically significant correlation between the clinical forms
of disease, Marsh score and the distribution of the different alleles (p
= 0,07). Conclusion: We confirmed in this study the high frequency
of DQ2 haplotype in CD patients. Presence of HLA DQ2 or DQ8 is
mandatory but not sufficient for developing gluten enteropathy. HLA
polymorphism seems to have no impact on clinical forms of CD.
1
P12.030
A large family with spinocerebellar ataxia type 6 in iran: a
clinical and genetic study
R. Vazifehmand Roodposhtie 1 , H. Shimazaki 2 , V. Reza 3 , H. Hassan 3 , K.
Reza 4 , S. Sassan 3 , H. Shamsodin 5 , A. Fatemeh 4 , Y. Ouyang 2 , J. Honda 6 , I.
Nakano 6 , Y. Takiyama 2 ;
1 Shahid Beheshti Medical University, Tehran, Islamic Republic of Iran, 2 Jichi
Medical University, Neurology, Jichi, Japan, 3 Shaheed Beheshti University of
Medical Sciences and Health Services, Department of Anatomical Sciences,
Tehran, Islamic Republic of Iran, 4 The Social Welfare and Rehabilitation Sciences
University, Genetic Research Center, Tehran, Islamic Republic of Iran,
5 Qom University of Medical Sciences, Department of Neurological Sciences,
Tehran, Islamic Republic of Iran, 6 Jichi Medical University, Department of Neurology,
Jichi, Japan.
The authors describe a large Iranian family with autosomal dominant
cerebellar
ataxia, which included 14 patients in four generations. We examined
seven patients who
had expanded CAG repeats in the CACNA1A gene with repeat instability
(24 and 25
repeats). Although all patients showed cerebellar ataxia, each patient
exhibited peripheral
neuropathy or spasticity indicating intrafamilial phenotypic variability.
This is the first
report of SCA6 in Iran, and suggests the worldwide distribution of
SCA6.Key words: Spinocerebellar ataxia , SCA6 , Autosomal Dominant
, Iran
P12.031
somatic and germline mosaicism in a carrier of a large deletion
at Xp21 locus leading to chronic granulomatous disease and mc
leod syndrome
C. Kannengiesser 1,2 , N. Mahlaoui 3 , D. Henry 1 , E. Al Ageeli 1 , S. Quentin 4,5 , D.
Moshous 3 , M. de Blois 6 , A. Auvrignon 7 , f. Monceaux 8 , S. Perdereaux 8 , S. Briault
9 , M. Gougerot-Pocidalo 10,2 , B. Grandchamp 1,2 ;
1 AP-HP, Bichat, génétique, Paris, France, 2 Université Paris Diderot U773,
France, 3 AP-HP, Necker, Immunologie, Paris, France, 4 AP-HP, Plate forme
génomique IUH Saint Louis, Paris, France, 5 Université Paris Diderot, Paris,
France, 6 AP-HP, Necker, Cytogénétique, Paris, France, 7 AP-HP, Trousseau,
hématologie oncologie pédiatrique, Paris, France, 8 CHR Orléans, Pédiatrie, Orléans,
France, 9 CHR Orléans, cytogénétique, Orléans, France, 10 AP-HP, Bichat,
immunologie hématologie, Paris, France.
The proband is a boy who presented when he was three months old
with a granulomatous lymphadenitis. Nitroblue tetrazolium reduction
assay (NBT test) was consistent with the diagnosis of chronic granulomatous
disease (CGD), a immunodeficiency disease resulting from
mutation in genes encoding the subunits of NADPH oxidase complex :
CYBA, CYBB, NCF1 and NCF2 (Online Mendelian Inheritance in man
MIM#s 233690, 306400, 233700, 233710). Western blot analysis of
the NADPH oxidase subunits revealed absence of expression of GP-
91phox encoded by CYBB (Xp21). The patient had also acanthocytosis
suggesting a McLeod syndrome that is caused by a mutation in XK
locus also at Xp21. We hypothesized a contiguous gene deletion for
XK and CYBB. We confirmed the presence of a large deletion of 1.8Mb
of CYBB by CGH array and characterized precisely the breakpoints by
sequencing a PCR fragment generated using primers from each side
of the deletion. Using quantitative PCR at the CYBB locus and the
specific PCR amplification of the deleted X chromosome, we showed
that the mother had a somatic mosaicism and that an half sister of the
proband was a carrier of the deletion. Segregation analysis of microsatellite
markers in this family (including 3 additional half brothers of
the proband) revealed that the deletion was either present or absent
on the same X-chromosomal region inherited from the mother, thus
indicating a germline mosaicism. We provide here molecular evidence
for the occurrence of somatic and germline mosaicism in a carrier of
CGD and McLeod syndrome.
P12.032
chiari malformation type i: Linkage to chromosome 16p13.3 in a
large spanish kindred
E. Cuenca-Leon 1 , A. Urbizu 1 , S. Boronat 1 , E. Solana 2 , T. Vendrell 3 , E.
Vázquez 4 , M. Poca 2 , A. Macaya 1 ;
1 Grup de Recerca en Neurologia Infantil, Institut de Recerca Vall d’Hebron,
Barcelona, Spain, 2 Servei de Neurocirurgia, Hospital Universitari Vall d’Hebron,
Barcelona, Spain, 3 Unitat de Genètica Clínica, Hospital Universitari Vall
d’Hebron, Barcelona, Spain, 4 Institut de Diagnòstic per la Imatge, Hospital
Universitari Vall d’Hebron, Barcelona, Spain.
Background: Chiari malformation type I (CMI) is a mesodermal anomaly
that may cause severe and progressive neurological deficits. The
main feature is the ectopia of the cerebellar tonsils which are downwardly
displaced through the foramen magnum. Familial aggregation,
twin studies and cosegregation with known genetic syndromes support
that at least in a subset of CMI patients there is a substantial genetic
contribution, but up to date no genetic loci or genes have been convincingly
linked to CMI.
Objective: To map the disease-causing gene in a large Spanish kindred
with Chiari malformation type I (CMI) with a mendelian pattern
of inheritance.
Methods: DNA samples from 31 family members were obtained.