2009 Vienna - European Society of Human Genetics

Clinical genetics and Dysmorphology
(NFNS). The major gene causing NFNS is NF1. Rarely, a mutation in
PTPN11 in addition to an NF1 mutation is present.
We present the clinical and molecular characterisation of a family displaying
both NS and NF1 features, with complete absence of neurofibromas.
To investigate the aetiology of the phenotype, mutational
analysis of NF1 was conducted, revealing a novel missense mutation
in exon 24, p.L1390F, affecting the GAP-domain. Additional RAS-
MAPK pathway genes were examined, but no additional mutations
were identified. We confirm that NF1 mutations are involved in the
aetiology of NFNS. Furthermore, based on our results and previous
studies we suggest that evaluation of the GAP-domain of NF1 should
be prioritised in NFNS.
P02.141
molecular and clinical characterization of 37 patients with
Noonan syndrome
G. Baldassarre1 , C. Rossi2 , M. Tartaglia3 , C. Carta3 , E. Banaudi1 , N. Chiesa1 ,
M. C. Silengo1 , G. B. Ferrero1 ;
1 2 Department of Pediatrics, University of Torino, Torino, Italy, Department of
Pediatrics, Laboratory of Medical Genetics, Policlinico S. Orsola, Bologna, Italy,
3Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità,
Roma, Italy.
Noonan syndrome (NS, OMIM 163950) is an autosomal dominant disorder,
with a prevalence of 1:1000-1:2500 live births, characterized
by short stature, facial and skeletal dysmorphisms, cardiovascular defects
and haematological anomalies. Missense mutations of PTPN11
gene account for approximately 50% of NS cases, while molecular
lesions of other genes of the RAS/MAPK pathway play a minor role
in the molecular pathogenesis of the disease. Twenty-nine sporadic
and 4 familial cases of NS, for a total of 37 patients, underwent molecular
analysis of the main genes of the patwhay with a total mutation
detection rate of 78.8% (26/33). In details, we found 15 sporadic and
2 familial PTPN11 (51,5%), 6 sporadic and 1 familial SOS1 (21,2%),
1 sporadic KRAS and 1 sporadic BRAF (3%) mutated cases. The two
PTPN11 familial cases were characterized by a very high intrafamilal
varability, with a surprisingly mild facial phenotype. Interestingly, we
have observed some peculiar clinical features in SOS1 patients, in
particular a prominent metopic suture in a turricephalyc cranial vault,
not observed in PTPN11 mutated NS patients. The KRAS patient presented
typical NS dysmorphisms not associated with congenital heart
defects, while the BRAF patient, in addition to the characteristic NS
phenotype, presented epilepsy, a severe mental retardation and a
Chiari type I malformation, so far reported only in 4 other cases; it
is possible to propose that the cervical-occipital anomaly resulting in
Chiari I malformation, and its variants, can be an aspect of the skeletal
dysplasia of the syndrome.
P02.142
transcriptional hallmarks of Noonan syndrome in peripheral
blood mononuclear cells
G. B. Ferrero 1 , D. Cantarella 2 , G. Baldassarre 1 , C. Isella 2 , N. Crescenzio 1 , S.
Pagliano 1 , M. Silengo 1 , E. Medico 2 ;
1 Department of Paediatrics, University of Torino, Torino, Italy, 2 Institute for Cancer
Research and Treatment, University of Torino Medical School, Torino, Italy.
Noonan syndrome (NS) is an autosomal dominant syndrome characterized
by a distinctive facial appearance, heart defects and skeletal
abnormalities, rarely associated with mental retardation or juvenile
myelomonocytic leukemia. The majority of germline mutations responsible
for this disorder are in the PTPN11 and SOS1 genes encoding
proteins of the Ras-MAPK pathway, which regulates cell proliferation,
differentiation and senescence by controlling gene expression.
To investigate the transcriptional consequences of these mutations,
we performed Global mRNA Expression Profiling (GEP) with Illumina
oligonucleotide microarrays on Peripheral Blood Mononuclear Cells
(PBMCs), a target tissue of the syndrome. In detail, we analyzed 23
samples from molecularly defined NS patients (17 with PTPN11 and
6 with SOS1 mutation), and 20 samples from age- and sex-matched
controls. Out of over 20,000 genes analyzed, 5,254 passed a statistical
filter for reliable signal detection and for not being correlated with
age, sex, or differential leucocyte count. Subsequently, t-test and signal-to-noise
ratio were used to select genes differentially expressed
between control samples and NS cases, all together or subdivided in
PTPN11 and SOS1 subgroups. Interestingly, GEP analysis highlighted
a transcriptional profile specifically associated to the mutational status
of NS samples. Both PTPN11 and SOS1 subgroups were well distinguished
from control samples, however displaying clearly distinct patterns
of gene expression, not consistent with a homogeneous generic
NS group. These data provide initial evidence of a high potential for
PBMCs GEP analysis to dissect at transcriptional level the molecular
complexity of the inherited developmental disorders of the Ras-MAPK
pathway.
P02.143
A possible role for the PtPN11 gene in sex determination
S. Jain1,2 , M. Thomas1 , J. Jessen1 , S. Keating1 , D. Chitayat1 ;
1 2 Mount Sinai Hospital, Toronto, ON, Canada, University of Toronto, Toronto,
ON, Canada.
The PTPN11 (protein tyrosine phosphatase, non-receptor type 11)
gene carries the instructions for making a protein called protein tyrosine
phosphatase, nonreceptor type 11, more commonly known as
SHP-2. SHP2 forms a subgroup of this class and is a key player in
generating signals within cells that affect cell function, division and differentiation.
Germline mutations in this gene have been known to be
associated with various diseases, including Noonan syndrome, LEOP-
ARD syndrome, and juvenile myelomonocytic leukemia (JMML). The
case presented here was diagnosed antenatally with cystic hygroma,
hydrops fetalis, bilateral club feet, ASD and a karyotype of 46XX. Termination
of pregnancy occurred at 17 weeks of gestation and autopsy
identified ambiguous genitalia and normal testes. DNA analysis for
PTPN11 showed a heterozygous C > A nucleotide change in exon 13,
which has not been previously reported. The mutation is found in a
strongly conserved domain across species.
The spectrum of PTPN11 mutations and their clinical implications are
wide-spread, explained by the ubiquitous expression of this protein. It
remains interesting that association of the gene with sex differentiation
or ambiguous genitalia has not been made previously. Our patient was
found to have a novel, likely pathogenic PTPN11 mutation. Although
the karyotype revealed a normal female genotype, the gonads were
normal testes with the external genitalia showing ambiguity. The absence
of SRY gene and the finding of a de novo, germline mutation
in the PTPN11 gene raises a possible important role for the PTPN11
gene in sex determination.
P02.144
mutation database of Noonan, costello and cardio-faciocutaneous
(cFc) syndromes
Y. Aoki, T. Niihori, T. Kobayashi, S. Kure, Y. Matsubara;
Tohoku University School of Medicine, Sendai, Japan.
Noonan syndrome, Costello syndrome and cardio-facio-cutaneous
(CFC) syndrome are autosomal dominant multiple congenital anomaly
syndromes characterized by a distinctive facial appearance, heart defects,
musculocutaneous abnormalities and mental retardation. There
has been growing evidence that these syndromes are caused by dysregulation
of the RAS/mitogen activated protein kinase (MAPK) pathway.
Noonan syndrome is caused by mutations in PTPN11, KRAS,
SOS1, or RAF1. Costello syndrome is caused by mutations in HRAS,
whereas CFC syndrome is associated with mutations in KRAS, BRAF
or MAP2K1/2. The molecules encoded by these genes in the pathway
play pivotal roles in cell proliferation, differentiation, survival and cell
death. We recently suggested that disorders with mutations of molecules
in the RAS/MAPK cascade may be comprehensively termed
“the RAS/MAPK syndromes” (Aoki et al., Hum Mutat 29(8):992-1006,
2008) . As more mutations were identified in affected patients, significant
overlaps of clinical pictures among these syndromes became
evident. It may be necessary to re-classify these syndromes according
to molecular diagnosis and re-evaluate clinical manifestations. To
this end, we launched a website including the details on the MAPK
syndromes and mutation database (http://www.medgen.med.tohoku.
ac.jp/RasMapk syndromes.html). Although the database is still in its
infancy, it would help us to overview the spectrum of mutations of various
genes and to aid genetic testing of these elusive disorders.