2009 Vienna - European Society of Human Genetics

Clinical genetics and Dysmorphology
P02.145
Noonan-syndrome-like phenotype associated with a familial
12q13 about 1.1 mb microduplication proximal to the PtPN11gene.
Rt-PcR-investigations on a large number of Noonan
syndrome patients who were found to be negative for mutations
in genes related to this disorder for similar genome aberrations.
P. M. Kroisel1 , A. C. Obenauf1 , P. Kubec2 , K. Wagner1 , M. R. Speicher1 , M.
Zenker3 , T. Schwarzbraun1 ;
1 2 Institute of Human Genetics, Graz, Austria, Department of Pediatrics, Oberwart,
Austria, 3Institute of Human Genetics, Erlangen, Germany.
Noonan-syndrome, a relatively common heterogeneous disorder (estimated
incidence of 1 in 1000 - 2500 live births) was shown to occur
due to dysregulation of the RAS-MAPK pathway. Gain-of-function mutations
in the PTPN11, KRAS, SOS1, and RAF1 genes from the RAS/
MEPK signalling pathway can be identified in about 70-80 % of individuals
with Noonan syndrome. In 40-50 % mutations of the PTPN11
gene were found to be responsible with considerable phenotype variability.
There is an overlap of phenotype features with Costello- and
CFC-syndrome, also developmental disorders of the RAS-RAF-MAPK
pathway. Recently an 8 Mb large duplication in 12q24 including the
PTPN11 gene was reported in a Noonan syndrome patient, who was
negative for mutations of the PTPN11, KRAS, SOS1 and RAF1 genes.
The conclusion that duplication of the PTPN11 gene could be responsible
was therefore put forward. Here we describe a new microduplication
of about 1.1 Mb at 12q13 identified by microarray analysis and
verified by RT-PCR in a 7 year old boy and his mother who both show
physical including facial and mental symptoms compatible with diagnosis
of Noonan syndrome. Sequencing analysis of the PTPN11 and
KRAS genes did not show a causative mutation. Interestingly a gene
of the MAP-kinase family is duplicated in these patients. Results of a
detailed investigation for genome copy alterations by RT-PCR-analysis
using primer sets for the proximal, central and distal part of this
1.1.Mb microduplication in more than 100 Noonan syndrome patients
negative for mutations in Noonan syndrome related genes will be presented.
P02.146
molecular analysis of the Noonan (-like) syndromes: overview of
7 years of DNA diagnostics in the Netherlands
H. G. Yntema1 , W. M. Nillesen1 , K. P. J. van der Donk1 , G. M. G. van de Ven-
Schobers1 , M. T. M. Schepens1 , M. C. J. Jongmans1 , C. Noordam2 , I. van der
Burgt1 ;
1 2 Department of Human Genetics, Nijmegen, The Netherlands, Department of
Pediatrics, Nijmegen, The Netherlands.
The clinically related Noonan syndrome, Cardio-Facio-Cutaneous
(CFC) syndrome, and Costello syndrome are characterised by a typical
facial appearance with hypertelorism, ptosis, down slanting palpebral
fissures, low set posteriorly rotated ears, and short neck. Other characteristic
findings include congenital heart disease, mental retardation,
and short stature. These disorders are caused by dysregulation of the
RAS/mitogen activated protein kinase (MAPK) pathway, due to mutations
in the genes PTPN11, SOS1, RAF1(Noonan syndrome), BRAF,
MAP2K1, MAP2K2 (CFC syndrome), HRAS (Costello syndrome), or
KRAS (Noonan, CFC, and Costello syndrome).
In our laboratory, PTPN11 mutation analysis has been performed in
more than 1000 index cases with a clinical suspicion of Noonan/CFC/
Costello syndrome. In 25% of patients a mutation could be identified,
up to 80% of which appeared to be de novo. In one family, homozygosity
for a PTPN11 mutation caused severe cardiac disease in two
fetuses, and lethality shortly after birth. Selective mutation analysis of
the other genes in the MAPK pathway led to a molecular diagnosis in
an additional 30% of patients.
The recent implementation of a high-throughput automated parallel
sequencing protocol of all known genes involved in Noonan/CFC/
Costello syndrome in our laboratory, has led to the identification of
novel mutations. We gained more insight in genotype/phenotype correlations,
and concluded that more Noonan (-like) genes remain to be
discovered. Furthermore, there is an urgent need for a prenatal testing
protocol, since we identified one PTPN11 and one KRAS mutation in
fetuses with polyhydramnion and increased nuchal fluid with a normal
karyotype.
P02.147
Atypical molecular findings in four patients with suggestive
Noonan-related syndromes
J. Santome Collazo 1 , A. Carcavilla 2 , A. Tabernero Garcia 1 , E. Albinana 3 , E.
Guillen Navarro 4 , A. Perez-Aytes 5 , P. Lapunzina 6 , B. Ferreiro Fernandez 1 , R.
Munoz-Pacheco Roman 1 , B. Ezquieta Zubicaray 1 ;
1 Hospital General Universitario Gregorio Maranon, Madrid, Spain, 2 Hospital Virgen
de la Salud, Toledo, Spain, 3 Hospital General de Almansa, Albacete, Spain,
4 Hospital Virgen de la Arrixaca, Murcia, Spain, 5 Hospital General Universitario
la Fe, Valencia, Spain, 6 Hospital General Universitario la Paz, Madrid, Spain.
Germline missense mutations in genes coding for different components
of the RAS/MAPK signalling cascade (PTPN11, SOS1, RAF1
and RAS) have been recognized as the cause of several phenotypically
overlapping autosomal-dominant disorders, recently referred to
as the Noonan-related Syndromes (Noonan, LEOPARD, Costello and
Cardiofaciocutaneous syndromes). Herein we describe four patients
presenting atypical findings in molecular diagnosis.
Patient #351 had suggestive facial dysmorphology, severe short stature
and bilateral cryptorchidism. DNA testing identified an in-frame
3pb-insertion in exon-7 of PTPN11 gene (p.Q255_Q256insQ). Two
other affected members of the family segregate the variant.
Patient #178 presented with facial dysmorphology and mild short stature.
PTPN11 assays were performed, revealing a 3pb-deletion in intron-12
(c.-16_-18delATG). In silico splicing simulation produced new
acceptor splice sites, thus probably affecting the correct splicing.
Patient #301 displayed craniofacial anomalies with severe short stature,
pulmonic stenosis and hypertrophic myocardiopathy, moderate
developmental delay, and severe linfatic dysplasia. PTPN11 gene
analysis revealed the presence of a de novo single-codon doublenucleotyde
substitution (p.T73L) that produces an aminoacidic change
not previously reported.
Patient #255 had typical facial phenotype, pulmonic stenosis, hypertrophic
myocardiopathy and severe feeding difficulties. Molecular diagnosis
showed a heterozygous 6pb-deletion in intron-1 5’UTR region in
HRAS gene (c.-84_-89delGGGCCT). Mutations in 5’UTR might affect
regulation of gene expression.
This study describes four patients with suggestive Noonan-related Syndromes
with atypical molecular findings. Phenotypical consequences
of all these mutations have not been proved with an in vitro analysis,
but some indirect approaches have been performed to explore the effect
of these atypical variants.
P02.148
Duplication of the Rubinstein-taybi locus at 16p13: a novel case
with overgrowth is broadening the phenotypic spectrum
S. Azzarello-Burri, A. Schinzel, A. Baumer, M. Riegel, B. Steiner;
Institute of Medical Genetics, Schwerzenbach, Switzerland.
Microduplications encompassing the Rubinstein-Taybi region at
16p13.3 lead to a rare multiple congenital anomalies/ mental retardation
syndrome. We report on a 19 years old male patient with an overgrowth
syndrome with multiple congenital anomalies and mild mental
retardation due to a 0.95 Mb duplication at 16p13.3. He presented
with a left dysplastic ear with atresia of the external auditory canal, a
preauricular tag, fused middle ear ossicles and bilateral deafness. The
dysmorphic facial features were characteristic for a long and narrow
face, deep set eyes with low position of eyebrows, prominent nasal
root and tip, lateral flaring of eyebrows, short philtrum, prominent lips,
everted upper lip and large hand and feet with broad interdigital joints.
He showed tall stature with a mild scoliosis and a marked thoracic
kyphosis. Beside the typical facial and skeletal features, overgrowth
seems to be a key feature for submicroscopic duplications of the Rubinstein-Taybi
region. Many of the clinical features of our patient fit well
with the three cases published so far; however, some are unique (in
addition, he presented ear anomalies, very distinctly advanced growth
and relatively mild developmental delay), delineating the common clinical
phenotype on one side and broadening the clinical spectrum on
the other side. From this observation, we conclude that the evaluation
of patients with overgrowth syndromes with variable degree of mental
retardation should also include the investigation for submicroscopic
chromosomal imbalances.