2008 Barcelona - European Society of Human Genetics

Clinical genetics
P01.024
molecular mechanisms underlying thalassemia intermedia in
iran
M. Neishabury 1 , A. Azarkeivan 2 , C. Oberkanins 3 , F. Esteghamat 1 , N. Amirizadeh
2 , N. Amirizadeh 2 , H. Najmabadi 1,4 ;
1 Genetics Research center University of Social Welfare and Rehabilitation
Sciences, Tehran, Islamic Republic of Iran, 2 Thalassemia Clinic and Research
Center, Iranian Blood Transfusion Organization (IBTO), Tehran, Islamic Republic
of Iran, 3 ViennaLab Diagnostics GmbH, Vienna, Austria, 4 Kariminejad and
Najmabadi Pathology and Genetics Center, Tehran, Islamic Republic of Iran.
To improve the differentiation of thalassemia intermedia from other hemoglobinopathies
in Iran, four known genetic mechanisms, including
XmnI G γ polymorphism, inheritance of mild and silent β-thalassemia
alleles, δβ deletion and coinheritance of α- and β-thalassemia, were
investigated in 52 Iranian individuals, suspected to have thalassemia
intermedia based on clinical and hematological characteristics . Betaglobin
mutations were studied using a reverse-hybridization assay and
sequencing of the total β-globin gene. The XmnI G γ polymorphism,
the Sicilian δβ deletion and four α-globin mutations (-α 3 .7 , -α 4 .2 , -- MED ,
ααα anti-3 .7 ) were studied using PCR-based techniques . The inheritance
of the XmnI G γ polymorphism with severe β-thalassemia alleles in the
homozygous or compound heterozygous state was the predominant
mechanism observed in 56 .5% of individuals . In 8 .7% of cases, this
status overlapped with the -α 3 .7 /αα genotype. The second most frequent
cause for thalassemia intermedia (15 .2%) was the inheritance
of mild β-thalassemia alleles, including IVS-I-6 (T>C), -88 (C>A) and
+113 (A>G). In 4.3% of subjects the Sicilian δβ deletion was identified.
HbS in association with β 0 -thalassemia was found in 2 .2% of
patients, who had been misdiagnosed as thalassemia intermedia . In
21.7% of cases no causative genetic alteration could be identified. Our
results reflect the diversity underlying thalassemia intermedia in Iran,
and the limitations of the applied clinical, hematological and molecular
approaches for correct diagnosis . Some of our unresolved cases
will offer an opportunity to discover additional molecular mechanisms
leading to thalassemia intermedia .
P01.025
Prenatal diagnosis of cystic fibrosis: the 18-year experience of
Brittany (western France)
I. Duguépéroux 1,2 , V. Scotet 1 , M. Audrézet 1,2 , M. Blayau 3 , P. Boisseau 4 , H. Journel
5 , P. Parent 6 , C. Férec 1,2 ;
1 INSERM U-613, Brest, France, 2 CHU - Lab Génétique Moléculaire, Brest,
France, 3 CHU - Lab Génétique Moléculaire, Rennes, France, 4 CHU - Lab Génétique
Moléculaire, Nantes, France, 5 CH - Unité Génétique Médicale, Vannes,
France, 6 CHU - Dpt Pédiatrie et Génétique Médicale, Brest, France.
Objective: This study reports 18 years of experience in prenatal diagnosis
(PD) of cystic fibrosis (CF) in a region where CF is frequent
and the uptake of PD common (Brittany, western France) . method:
All PDs made over the period 1989-2006 in women living in Brittany
were collected . Results: We recorded 268 PDs made in 1 in 4 risk
couples, plus 22 PDs directly made following the sonographic finding
of echogenic bowel . Most of the 268 PDs were done in couples
already having CF child(ren) (n=195, 72.8%). Close to one fifth followed
cascade screening (n=49, 18.3%), which identified 26 new 1 in 4
risk couples among the relatives of CF patients or of carriers identified
through newborn screening . The remaining PDs were mainly made
in couples whose 1 in 4 risk was evidenced following the diagnosis
of echogenic bowel in a previous pregnancy (n=22, 8 .2%) . Although
patients’ life expectancy has considerably improved, in our population
the great majority of couples chose pregnancy termination when PD
indicated that the fetus had CF (95 .9%) . conclusion: This study describes
the distribution of PDs according to the context in which the 1
in 4 risk was discovered and highlights the real decisions of couples as
regards pregnancy termination after a positive PD .
P01.026
Strategy for prenatal diagnosis of cystic fibrosis in Serbia
D. Radivojevic, T. Lalic, M. Djurisic, M. Guc-Scekic, M. Miskovic, V. Ivanovski;
Mother and Child Health Institute of Serbia, Belgrade, Serbia.
Cystic fibrosis is the most common autosomal recessive disease in
Caucasians,caused by more then 1500 mutations in CFTR gene .In
Serbian CF patients 21 different CF mutations were found accounting
for 82% of CF alleles .
Since 1996,we have performed 102 prenatal diagnoses for 76 couples
with 11 different genotypes .One case included twin pregnancy and another
a CF affected mother .In one family-at-risk parent was a carrier of
complex allele (two mutations in cis) .
Total of 63 families were fully informative for direct DNA analysis,which
was performed using heteroduplex analysis (PAGE),ARMS-PCR (Elucigene
tm CF 29 kit,Orchid) and DGGE analysis of PCR amplified exons
1-24 .In other 13 families,only one parental mutation was known,so prenatal
analysis was done by indirect DNA analysis (haplotype analysis
for 6 diallelic sites and one tetranucleotide repeat) .Materials used for
fetal DNA analysis were mostly CVS samples (68 cases),amniocytes
in 28 cases and fetal blood in 6 cases .Results showed that 19 fetuses
were affected,50 were carriers and 33 fetuses were healthy .
Since 2006,we have started screening for the presence of CFTR mutations
in couples with echogenic bowel detected on ultrasound investigation
during the second trimester of pregnancy .From 21 cases,in 16
only the couple was tested,and in 3 cases both parents and fetus were
tested .No positive cases were found .
If the causative mutations were identified before pregnancy,results
were given within few days,indicating that the current strategy using
a combination of methods mentioned above provide rapid and reliable
prenatal diagnosis for all families at risk in our country .
P01.027
cFtR haplotypes associated with p.s466X mutation among
iranian cF patients
R. Alibakhshi 1,2 , M. Zamani 3 , R. Kianishirazi ‎ 2 , J. Cassiman ‎ 4 , H. Cuppens 4 ;
1 Department of Biochemistry, Faculty of Medicine, Kermanshah University of
Medical Sciences(KUMS), kermanshah, Islamic Republic of Iran, 2 Division
of Medical Genetics, Reference Laboratory, Kermanshah University of Medical
‎Sciences, Kermanshah, Islamic Republic of Iran, 3 Department of Medical
Genetics, School of Medicine, Tehran University of Medical ‎Sciences, Tehran,
Islamic Republic of Iran, 4 Center for human Genetics, KULeuven, Leuven,
Belgium.
Cystic fibrosis (CF) is the most common inherited disorder in Caucasian
populations, with over 1400 mutations identified in the Cystic
Fibrosis Transmembrane conductance Regulator (CFTR) gene . We
have screened 69 Iranian CF patients, and 1 CBAVD patient for mutations
and polymorphic sites in the complete coding region, and its
exon/intron junctions, of their CFTR genes, using different methods,
such as ARMS (amplification refractory mutation system)-PCR, SSCP
(single stranded conformation polymorphism) analysis, restriction enzyme
digestion analysis, direct sequencing, and MLPA (Multiplex Ligation
mediated Probe Amplification).
Based on our work, the third most prevalent mutation in Iran was
p .S466X . It was found in 5 .7 % (8/140) of the CFTR genes from Iranian
CF patients, and was only observed in homozygous state . These 4 patients
were from Tehran, Khorasan, Hamadan and Markazi provinces .
The parents of these patients all had consanguine marriages, however
since that the mutation was present in families from different regions; it
seems to be a relative frequent mutation in Iran . This mutation is rare
worldwide, but has a frequency of 0 .5% in Serbia and Montenegro .
Interestingly, the patients with p .S466X mutation were homozygous at
some of intragenic polymorphic sites and showed similar haplotypes .
These were: IVS8 TGm and Tn (TG12-T7__TG12-T7), IVS6a (TTGA6/
TTGA6), intron 9 nt1525-61 (G/G) and exon 10 nt1540 (A/A; M470/
M470) . The polymorphisms were seen in direct sequencing .
P01.028
Identification and characterization of three CFTR gene partial
duplications
M. Legendre 1 , A. Le Floch 1 , F. Niel 1 , C. Gameiro 1 , J. Martin 1 , D. Grenet 2 , J. Derelle
3 , V. Izard 4 , C. Costa 1 , M. Goossens 1 , E. Girodon 1 ;
1 CHU Henri Mondor, Créteil, France, 2 Hôpital Foch, Pneumologie, Suresnes,
France, 3 Hôpital d’Enfants, Médecine infantile, Vandoeuvre-les-Nancy, France,
4 CHU Bicêtre, Urologie, Le Kremlin-Bicêtre, France.
Background: Cystic fibrosis and disorders related to Cystic Fibrosis
transmembrane Conductance Regulator (CFTR) pathology are mainly
due to point mutations scattered over the whole CFTR gene . Search
for large CFTR rearrangements using semi-quantitative fluorescent
multiplex (QFM) PCR assays is now part of the molecular diagnosis
and allows to identify 2% of CF alleles . Rearrangements mainly
comprise single or multiple exon deletions; duplications are rare and