2008 Barcelona - European Society of Human Genetics

Clinical genetics
sition was identified in the exon3. This change predicts the Asn58Asp
substitution in family NS-X, and affects the N-SH2 domain of SHP-2 .
Patients with PTPN11 disease related mutations had characteristic
phenotypes: a proband from NS-VI family presented short stature,
dysmorphic facial features and atrial septal defect; a proband from NS-
X family had short stature, pulmonary valve stenosis and dysmorphic
facial features . Future studies involving clinical and genetic investigations
are necessary to correlate genotype-phenotype expression . Supported
by Estonian Science Foundation grant GARMP6573 .
P01.187
PtPN11 gene analysis in a sample of mexican patients with
Noonan syndrome
C. N. Gonzalez-Huerta 1 , L. M. Gonzalez-Huerta 2 , S. Cuevas-Covarrubias 3 ;
1 Instituto Nacional de Rehabilitacion, Mexico DF, Mexico, 2 Hospital General
de Mexico, Mexico DF, Mexico, 3 Hospital General de Mexico, Facultad de Medicina,
UNAM, Mexico DF, Mexico.
Noonan syndrome (NS) is a dysmorphic syndrome characterized by
hypertelorism, low-set posteriorly rotated ears, short stature, a short
neck with webbing or redundancy of skin, cardiac anomalies, epicanthic
folds and motor delay . NS may occur on a sporadic basis, with a
predominance of paternal origin, or in an autosomal dominant inheritance
with a predominance of maternal transmission . NS is clinically
similar to the Turner syndrome . More than 50% of patients with NS
have mutations in the PTPN11 gene . Most of the mutations are recurrent
and cluster in exons 3, 8 and 13 . All the PTPN11 missense mutations
are present in the interacting regions of the amino N-SH2 domain
and the phosphotyrosine phosphatase (PTP) domains . It seems that
gain-of-function changes are responsible of the phenotype observed
in NS . In the present study we analyzed the PTPN11 gene in a group
of 10 patients with diagnosis of NS . DNA genomic from leukocytes
was extracted with conventional methods . All exons of the PTPN11
were amplified and sequenced trough polimerase chain reaction and
DNA sequencing analyzes . We detected a low frequency of mutations
in the PNP11 gene in the patients; most patients showed a normal sequence
of the PNP11 gene . These data indicate that probably PNP11
gene mutations are not the most frequent cause of NS in Mexican
population .
P01.188
Diverse driving forces underlie the occurrence of invariant
PTPN mutations in Noonan and LEOPARD syndromes
S. Martinelli 1 , P. Torreri 1 , M. Tinti 2 , L. Stella 2 , G. Bocchinfuso 2 , E. Flex 1 , A. Grottesi
3 , S. Delle Vigne 1 , M. Ceccarini 1 , A. Palleschi 2 , G. Cesareni 2 , L. Castagnoli 2 ,
T. C. Petrucci 1 , B. D. Gelb 4 , M. Tartaglia 1 ;
1 Istituto Superiore di Sanità, Rome, Italy, 2 Università “Tor Vergata”, Rome,
Italy, 3 Consortium for the Application of Super-Computing for Universities and
Research, Rome, Italy, 4 Mount Sinai School of Medicine, New York, NY, United
States.
Missense PTPN11 mutations cause Noonan and LEOPARD syndromes
(NS and LS), two developmental disorders with pleiomorphic
phenotypes . PTPN11 encodes SHP2, an SH2 domain-containing
protein tyrosine phosphatase functioning as a signal transducer .
Generally, different substitutions of a particular amino acid residue
are observed in these diseases, indicating that the crucial factor is
the residue being replaced . For a few codons, only one substitution
is observed, suggesting the possibility of specific roles for the residue
introduced . We analyzed the biochemical behavior and ligand-binding
properties of all possible substitutions arising from single-base
changes affecting codons 42, 139, 279, 282 and 468 to investigate the
mechanisms underlying the invariant occurrence of the T42A, E139D
and I282V substitutions in NS and the Y279C and T468M changes in
LS . Our data demonstrate that the isoleucine-to-valine change at codon
282 is the only substitution at that position perturbing the stability
of SHP2’s closed conformation without impairing catalysis, while the
threonine-to-alanine change at codon 42, but not other substitutions of
that residue, promotes increased phosphopeptide binding affinity. The
recognition specificity of the C-SH2 domain bearing the E139D substitution
differed substantially from its wild type counterpart acquiring
binding properties similar to those observed for the N-SH2 domain, revealing
a novel mechanism of SHP2’s functional dysregulation . Finally,
while functional selection does not seem to occur for the substitutions
at codons 279 and 468, we point to deamination of the methylated
cytosine at nucleotide 1403 as the driving factor leading to the high
prevalence of the T468M change in LS .
P01.189
Diagnostic tests for costello syndrome and cardio-faciocutaneous
syndrome - two years service experience.
J. A. Shorto 1 , B. Kerr 2 , B. Tang 3 , R. Elles 1 ;
1 Regional Molecular Genetics Service, Manchester, United Kingdom, 2 Clinical
Genetics Service, Manchester, United Kingdom, 3 Academic Unit of Medical
Genetics and Regional Genetics Service, Manchester, United Kingdom.
Costello and Cardio-Facio-Cutaneous (CFC) syndromes are autosomal
dominant multiple congenital abnormalities with phenotypic overlaps
to Noonan syndrome . The main difference with respect to their
management is an increased tumour risk in Costello syndrome (approximately
17%) .
Costello syndrome is associated with mutations in HRAS (82-92%),
the majority of the mutations identified to date are in codons 12 and 13.
No other disease causing genes have been identified. All five coding
exons of HRAS are screened by bi-directional fluorescent sequencing
.
So far four genes have been identified in CFC syndrome; BRAF (37-
78% patients), KRAS, MEK1 and MEK2. We use bi-directional fluorescent
sequencing to screen BRAF (exons 6, 11, 12, 13, 14, 15 and
16), KRAS (all five coding exons), MEK1 (exons 2 and 3) and MEK2
(exons 2 and 3) .
We have been offering a diagnostic service for both Costello syndrome
and CFC syndrome for 2 years, since June 2006 . So far 125
patients with a likely diagnosis of either Costello or CFC syndrome
have been referred to us . We detected 26 pathogenic mutations in 101
patients tested for HRAS mutations . In the cohort of 71 patients tested
for CFC syndrome we detected 19 pathogenic mutations (BRAF=14,
KRAS=2, MEK1=3) and a further seven that are likely to be pathogenic
(BRAF=4, KRAS=2, MEK2=1) . We tested both parents of 14 patients
with a known pathogenic mutation and 2 patients with a likely pathogenic
mutation, in all cases the mutation was shown to be de novo .
P01.190
complex Approach to Diagnostics and Data Analysis for
Neurofibromatosis type 1
T. Marikova1 , A. Krepelova1 , S. Bendova1 , B. Petrak1 , M. Kaluzova1 , M. Zakova2
, L. Novakova2 , O. Stepankova2 ;
1 2 2nd Medical School, Prague 5 - Motol, Czech Republic, Czech Technical
University, Prague, Czech Republic.
The Neurofibromatosis type 1 (NF1) is one of the most common single
gene diseases (the expected incidence is 1:3000) .
There was implemented a database of 300 records of patients suffering
from NF1 in the Institute of Biology and Medical Genetics 2nd Medical
School, Charles University in Prague .
The complex investigation methodology in the patients with a NF1 has
been verified. The DNA bank for these patients was created containing
150 DNA samples . We have implemented reliable molecular genetic
diagnostics of the NF1 gene using MLPA and DHPLC methods .We
have investigated 39 families and detected causal mutation of the NF1
gene in 26 patients, from which 13 mutations were not been previously
detected . Last year, we have implemented high resolution melt analysis
(HRM) as an effective tool for the mutation scanning of the NF1
gene with sensitivity comparable with the DHPLC method .
The clinical, neurological, neurophysiological, and biochemical data
of patients have been analyzed in detail by support of artificial intelligence
methods .
The patient records are stored in the form of text files. Their content
has to be converted into a database format to analyze them by available
machine learning techniques . The pilot data analysis will be summarized
.
supported by projects AV-CR-1ET 101210513 and GAUK 62007
P01.191
Neurofibromatosis type 1 in adulthood: clinical analysis of a 80
patients cohort
F. Natacci 1 , G. Melloni 1 , M. F. Bedeschi 1 , E. Vismara 2 , G. Tadini 3 , M. Moggio 4 ,
M. Caroli 5 , C. Lamperti 4 , M. Sciacco 4 , M. Brambilla 6 , L. Trespidi 7 , A. Costa 8 , F.
Viola 2 , D. Bianchessi 9 , G. Finocchiaro 9 , P. Riva 10 , L. Larizza 11 , F. Lalatta 1 ;
1 Clinical Genetics Unit, Fondazione IRCCS, Ospedale Maggiore Policlinico,
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