2009 Vienna - European Society of Human Genetics

Molecular basis of Mendelian disorders
de Biologia, Universitat de Barcelona, CIBERER, IBUB, Barcelona, Spain.
Gaucher disease is an autosomal recessive disorder. It is characterized
by the accumulation of glucosylceramide in lysosomes of the
mononuclear phagocyte system, attributable to glucocerebrosidase
(GBA; EC3.2.1.45) deficiency. The main consequences of this disease
are hepatosplenomegaly, skeletal lesions and, sometimes, neurological
manifestations. It has been shown that at sub-inhibitory concentrations,
several competitive inhibitors act as chemical chaperones by
inducing protein stabilization and increasing enzymatic activity. We
have tested the chaperone effect of two iminosugars, N-(n-nonyl)-deoxynojirimycin
(NN-DNJ) and N-(n-butyl)-deoxynojirimycin (NB-DNJ),
and four aminocyclitols with distinct degrees of lipophilicity on mutated
GBAs. The analyses were performed on COS-7 cells transfected with
ten different mutant GBA cDNAs and on patient fibroblasts with diverse
genotypes. We have shown an increase in the activity of GBA with NN-
DNJ, NB-DNJ and aminocyclitol 1 in stably transfected cell lines for
some of the mutations and with NN-DNJ and aminocyclitol 4 in some of
the patients’ fibroblasts. These promising results on specific mutations
validate the use of chemical chaperones as a therapeutic approach
for Gaucher disease. However, the development and analysis of new
compounds is required. As a next step, we are currently analysing the
abnormal intracellular trafficking of mutant glucocerebrosidases by immunohistochemical
techniques and confocal microscopy. The cells are
being treated with the compounds that showed to have a chaperone
effect (NN-DNJ, NB-DNJ, aminocyclitol 1 and aminocyclitol 4), in order
to analyse if the enzymes from treated cells can reach the lysosomes.
P12.068
Generalized Atrophic Benign Epidermolysis Bullosa (GABEB),
caused by a new COL A truncatious mutation in a tunisian
patient
L. Adala 1 , M. Gribaa 1 , I. Ben Charfeddine 1 , O. Mamai 1 , A. Mili 1 , T. Ben Lazreg 1 ,
M. Denguezli 2 , J. Lacour 3 , A. Saad 1 ;
1 Laboratoire de Cytogénétique, de Génétique Moléculaire et de Biologie de la
Reproduction Humaines.CHU Farhat HACHED, Sousse, Tunisia, 2 Service de
Dermatologie et de Vénérologie.CHU Farhat HACHED, Sousse, Tunisia, 3 Service
de Dermatologie. Hôpital Archet 2, Nice, France.
Generalized Atrophic Benign Epidermolysis Bullosa, GABEB (OMIM#
226650), is a nonlethal variant of junctional epidermolysis bullosa with
autosomal recessive inheritance pattern. Clinically, it is characterized
by blistering of the skin since birth, atrophy of the affected skin, dystrophic
nails, dental anomalies and alopecia. The pathogenesis of this
disorder is generally caused by mutations affecting the BPAG2/CO-
L17A1 gene encoding hemidesmosomal transmembrane protein; the
180 KDa bullous pemphigoid antigen (BP180), also known as type
XVII collagen.In this study we describe a Tunisian GABEB patient
clinically EB affected who showed an absence of expression of BP180
at the dermal-epidermal junction revealed by immunohistochemical
staining analyses using antibodies against the type XVII collagen. The
COL17A1 gene sequencing has revealed a homozygous C458X mutation
in exon 17 of this gene responsible of the disease. The parents’
sequencing shows a heterozygous state of this mutation.
P12.069
GJB2 mutations in macedonian patients with non-syndromic
hearing loss
E. Sukarova Stefanovska 1 , M. Davceva-Cakar 2 , A. Momirovska 3,4 , G. D. Efremov
1 ;
1 Research Center for Genetic Engineering and Biotechnology, Macedonian
Academy of Sciences and Arts, Skopje, Macedonia, The Former Yugoslav
Republic of, 2 Audiology Center, Clinic for Otorhinolaryngology, Medical faculty,
Skopje, Macedonia, The Former Yugoslav Republic of, 3 Adrialab-Synlab,
Polyclinic for laboratory medicine, Skopje, Macedonia, The Former Yugoslav
Republic of, 4 Association of deaf and hard of hearing, Skopje, Macedonia, The
Former Yugoslav Republic of.
Hearing impairment is one of the most common sensory-neural disorders
with the incidence of profound deafness in one per 1,000 births.
Mutations in the GJB2 and GJB6 genes for DFNB1 locus (13q12) are
responsible for about half of all cases of autosomal recessive prelingual
hearing loss. Among them 35delG mutation accounts for approximately
70% of all GJB2 mutant alleles in most European populations.
The aim of the study was to evaluate the frequency and type of mutations
in GJB2 gene, as well as the frequency of GJB6 deletion among
Macedonian patients with non-syndromic hearing loss (NSHL). We
have analyzed 33 patients with prelingual NSHL.
SSCP analysis following by direct sequencing in fragments where altered
electrophoretic mobility was assigned was used for detection of
mutations in GJB2 gene, while specific PCR using two sets of primers
were used for (GJB6-D13S1830)del screening.
In 12 out of 33 patients (36.4%) mutations in GJB2 gene were found.
Among 22 mutated chromosomes, 15 (68.2%) carried 35delG mutation.
Other common mutations Trp24Stop, Val37Ile and Arg127His, with a
frequency of 6.06%, 3.0% and 1.5%, respectively, were found. (GJB6-
D13S1830)del mutation was not found in our group of patients.
Since high mutation rate was observed in GJB2 gene in NSHL patients,
testing should be performed as a routine screening in cases
with prelingual deafness.
P12.070
screening of mutations in mYOc, cYP1B1 and OPtN in spanish
families with glaucoma and ocular hypertension
E. Borràs1 , I. Hernan1 , E. Millá2,3 , S. Duch3 , M. Carballo1 , M. Gamundi1 ;
1 2 Hospital de Terrassa, Terrassa, Spain, Hospital Clínic de Barcelona, Barcelona,
Spain, 3Institut Comtal d’Oftalmologia, Barcelona, Spain.
Glaucoma is a heterogeneous group of optic neuropathies and represents
the second most prevalent cause of blindness worldwide, projected
to affect more than 60 million people by 2010. The purpose of
this study was the identification of MYOC, CYP1B1 and OPTN mutations
in a Spanish population affected by different clinical forms of familial
glaucoma or ocular hypertension, in order to determine the best
therapeutic approach.
Clinical studies were performed with ophthalmologic examination that
included pachymetry-corrected intraocular pressure applanation tonometry
and optical coherence tomography or Heidelberg retinal tomography.
Mutation detection was performed in 202 individuals from
84 families with a positive family history of glaucoma. Screening of mutations
in the MYOC gene in index patients revealed three previously
reported mutations (Gln368Stop, Val426Phe and Ala427Thr) and one
novel mutation (Glu218Lys). We performed CYP1B1 mutation analysis
in index patients affected by primary congenital glaucoma, and six
previously reported mutations were detected, namely Gly61Glu, His-
354fs, Arg368His, Thr403fs, Asp449fs and Arg469Trp. OPTN mutation
screening is currently being performed and up to now we have not
found any mutation associated to glaucoma.
We also present phenotype-genotype correlation in relatives of patients
with mutation in any of the analyzed genes. The genetic analysis
helps us to provide a more accurate visual prognosis as well as appropriate
genetic counselling.
P12.071
molecular, hematological aspects in HbH disease
H. Bagherian, S. Abdi, P. Fouladi, F. Rahiminezhad, M. Feizpour, R. Vahidi, S.
Forughi, M. Heidari, S. Zenali;
Dr Zenali Lab, Tehran, Islamic Republic of Iran.
Background: H disease is caused by deletion or inactivation of three
alpha-globin genes, People with H disease usually have moderate
anaemia, but are generally thought to be asymptomatic. Some H disease
patients require transfusions, and there are non deletional forms
of Hb H.Here we describe hematologic feature of cases with Hb H
disease.
Material and Methods: In this study we have defined the molecular
basis and the clinical phenotype with the alpha-globin genotype in 18
Iranian patients with HbH disease. HbH disease was diagnosed according
to abnormal red cell morphology including hypochromia, HbH
inclusion and persistence of HbH in Hb electrophoresis.
Result: The most molecular defect was the deletional most commonly
the (--/-alpha 3.7) genotype. In this study, 15 were deletional forms of
Hb H (--/-alpha) who had not received any blood transfusion and three
patients had the nondeletional type of hemoglobin H disease (--/alpha
alpha T ) with transfusion-dependent Hb H disease. Mean MCV and
MCH for deletional were 58.04 ± 4.31fl and 17.5 ± 1.2 pg respectively
(range from 46.6 to 64.9 for MCV and 14.3to 19.6 for MCH). HbH was
elevated significantly in all cases (mean value 9.3±5% ranging from
1.2-19.6%). HbH levels are usually higher in non deletional than in deletional,
(P value