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

Prenatal diagnosis
P0443. The risk of cystic fibrosis with prenatally detected
hyperechogenic bowel in Belarus population
N. Mosse, L. Savenko, E. Shepelevich, K. Mosse;
Scientific-Practical Center “Mother and Child”, Minsk, Belarus.
Hyperechogenic fetal bowel is prenatally detected by ultrasound during
the second trimester of pregnancy in 0.1-1.8% of fetuses. It has
been described to be associated with severe diseases, notably cystic
fibrosis (CF). The incidence of CF in Belarus is 1:8000 newborns,
much less than in West Europe. The aim of our study was to determine
the risk of CF in a prospective study of 70 fetuses with hyperechogenic
fetal bowel detected during the 2005-2006 years period
in our Center. Fetal cells and parental DNA were screened for CFTR
mutations. Two steps screening protocol was used. In the first step
the most frequent mutations in Belarus CF patients - dF508 (61.6%);
CFTRdele2,3(21kb) (6.8%) and 2184delA (4.1%), were analyzed in
one multiplex PCR reaction. When one mutation had been detected, a
direct sequencing strategy was applied. We found 6 affected fetuses,
which gave us an 8.6% risk of CF when a digestive tract anomaly
is observed at routine ultrasound examination. Mutations, associated
with pancreatic insufficient CF, were the most frequent. In 6 CF cases
5 dF508 and 3 CFTRdele2,3(21kb) mutations were identified. The high
incidence of CFTRdele2,3(21kb) can be explained by the more severe
gastrointestinal expression of the disease in compound deletion carriers.
Our results confirm that fetal bowel anomalies indicate a risk of
severe cystic fibrosis and justify careful CFTR gene analysis.
P0444. Newborn screening for cystic fibrosis in the Czech
Republic: observation of lower incidence of the disease
M. Balascakova 1 , A. Holubova 1 , V. Skalicka 2 , V. Vavrova 2 , D. Zemkova 2 , P.
Kracmar 3 , T. Piskackova 1 , F. Votava 3 , M. Macek Jr. 1 ;
1 Department of Biology and Medical Genetics, Charles University - Faculty
Hospital Motol, Prague, Czech Republic, 2 Department of Pediatrics, Charles
University - Faculty Hospital Motol, Prague, Czech Republic, 3 Department
of Pediatrics, Charles University - Faculty Hospital Kral. Vinohrady, Prague,
Czech Republic.
An early diagnosis of cystic fibrois (CF) is considered as a favourable
prognostic factor. Unless meconium ileus is present at birth, CF is could
be often misdiagnosed. Increase of the age at diagnosis (ADG) in our
country due to devolution of health care (prior to 1998 /median 0.58
years/; 1999-2005 /1.2 years/; p = 0.036) led us to initiate a pilot CF
newborn screening project (NBS; two tier IRT/DNA; II/2005-XI/2006)
covering ~62% of all newborns. Concentration of IRT was measured in
76,438 Guthrie cards and its level above the arbitrary cut off (75ng/ml)
was found in 799 cases (1.05%). Positive cases were examined using
a population specific CFTR mutation panel (~ 84% detection rate). In
total, 12 CF patients were identified and the median ADG was 37 days
(range 26-54). Interestingly, we also diagnosed previously unrecognised
CF in 3 older sibs. 53 ,,IRT positive“ newborns, that had only
1 CFTR allele, were subjected to follow-up sweat testing. Thus far,
45 cases were negative (ie. unaffected heterozygotes), while in one
instance a borderline result indicated long-term monitoring. When using
NBS data alone the incidence of CF was 1: 6,369, compared to the
previously epidemiologically established value of 1:2,700. However,
when respective prenatal diagnosis (PND) data from within study period
were taken into account incidence increased to 1:3,900. Overall,
our study proved that NBS is an efficacious tool for uniform diagnosis
of CF and that its incidence could be lower due to systematic PND during
the last decade. Supported by VZFNM00064203
P0445. Results of cytogenetical analysis of 1194 chordocenteses
M. Burek, L. Letica, R. Lasan, H. Ljubic, D. Muzinic, D. Begovic;
Division of Genetics and Metabolism, Department of Pediatrics, University
Hospital Centre, Zagreb, Croatia.
1194 chordocenteses were analyzed cytogenetically in a period of 22
years, using cytogenetical GTG-banding method. Indications for chordocenteses
were late weeks of pregnancy (ultrasound markers, parents
carrieres of reciprocal translocation, age, …) and amniocenteses
confirming.
From total number of 1194 chordocenteses, 88 (7,37 %) were karyotypically
determined as pathologic: 63 (71,5 %) numerical aberrations
and 25 (28,4 %) structural aberrations. The most frequent numerical
aberrations were trisomie of chromosome 21 (21/63; 33.3 %) and trisomie
of chromosome 18 (20/63; 31.7 %).
Pathology in amniocenteses were confirmed with almost 100 % accuracy
with chordocenteses. Considering other indications for chordocentesis,
most pathologic karyotypes were confirmed at ultrasound
markers indication (45/60; 75%).
P0446. Towards noninvasive prenatal diagnosis (NIPD) of
trisomy 21 Down syndrome
R. W. Old, F. Crea, W. M. Puszyk, M. A. Hulten;
University of Warwick, Coventry, United Kingdom.
The development of non-invasive prenatal diagnosis (NIPD) of trisomy
21 Down Syndrome based on a maternal blood sample rather than the
invasive procedures chorionic villus sampling or amniocentesis, is a
long-term goal in reproductive care. Copy number counting of cell-free
fetal DNA (cffDNA) sequences in maternal plasma presents a greater
challenge than NIPD based upon detecting paternal sequences in
cffDNA, already clinically feasible for X-linked disorders and RhD genotyping.
One approach for identification of fetal DNA exploits differences
in DNA methylation between maternal and cffDNA (the majority
of which originates from placental syncytiotrophoblasts).
We describe the first identification and characterisation of a panel of
chromosome 21-specific sequences (and reference sequences on
other autosomes) that are differentially methylated between peripheral
blood and placental tissue, DNA sequences which thus constitute candidate
biomarkers for NIPD of trisomy 21 Down Syndrome.
To select DNA sequences to be screened for differential methylation
between these tissues, we adopted three strategies (1) searching public
databases for highly differentially expressed genes, (2) choosing
‘random’ promoter regions, and (3) choosing ‘random’ non-promoter
regions. We screened these regions by methylation-specific restriction
enzymatic and bisulfite-conversion assays, and hence identified
a number of differentially methylated sequences located at 21q22.3
(AIRE, CLDN14, and ERG genes), at 1q32.1 (CD48 gene and FAIM3
gene), at 2p14 (ARHGAP25 gene) and at 12.24 (SELPLG gene). Clinical
evaluation of the sensitivity and specificity for NIPD of trsiomy 21
Down syndrome is underway.
This work has been supported by the EC NoE SAFE no LSHB-CT-
2004-503243.
P0447. Detection of median values of PAPP-A protein and free
beta hCG in serum samples of pregnant women in north-west of
Iran.
S. Mohaddes;
Medical Genetics Unit, Tabriz University of Medical Sciences, Tabriz, Islamic
Republic of Iran.
Pregnancy-associated plasma protein A and the beta subunit of human
chorionic gonadotrophin are well established markers used in
combination with nuchal translucency to screen the pregnancies for
Down syndrome and trisomy 18 in first trimester. However their median
values are different according to the ethnic origin. In the present
study the median values of free beta hCG and PAPP-A protein
were obtained in the population of pregnant women of North-West of
Iran, using serum samples prepared from 846 pregnancies at 11 th -13 th
weeks of gestation. The results were also compared to those of similar
findings on other ethnic origins. A significant difference was observed
between the median values calculated in the present study and those
reported for Asian and Caucasian ethinics. Our results indicate that
employing the median values, present in available risk calculation soft
wares for screening purposes, will result in underestimation of Down
syndrome and trisomy 18.
P0448. Evaluation of indications of prenatally diagnosed Down
syndrome cases between 2000-2006 years
F. Ozkinay 1 , S. Numanoglu 2 , A. Aykut 1 , S. Unlubay 1 , C. Gunduz 2 , O. Cogulu 1 ,
A. Vahabi 3 , D. Ercal 4 , C. Ozkinay 3 ;
1 Department of Pediatrics, Subdivision of Genetics and Teratology, Ege University,
Faculty of Medicine, Izmir, Turkey, 2 Ege University, Faculty of Medicine,
Department of Medical Biology, Izmir, Turkey, 3 Ege University, Faculty of Medicine,
Department of Medical Genetics, Izmir, Turkey, 4 Dokuz Eylul University,
Faculty of Medicine, Department of Pediatrics, Izmir, Turkey.
Down syndrome (DS) is the most commonly recognized genetic cause
of mental retardation. The risk of trisomy 21 is mostly related to advanced
maternal age. Our study aimed to determine the correlation
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