2009 Vienna - European Society of Human Genetics

Clinical genetics and Dysmorphology
P02.187
Genetic Heterogeneity in Rett syndrome: molecular and clinical
characterization of Females Heterozygous for Deleterious
mutations in CDKL and FOXG
L. Lambert 1 , C. Nemos 2 , D. Amsallem 3 , C. Francannet 4 , F. Giuliano 5 , B. Doray 6 ,
A. Roubertie 7 , A. Goldenberg 8 , B. Delobel 9 , V. Layet 10 , M. N´Guyen 11 , A. Saunier
2 , F. Verneau 2 , P. Jonveaux 2 , C. Philippe 2 ;
1 Service de Médecine Infantile I, Centre Hospitalier et Universitaire, Vandoeuvre
les Nancy, France, 2 Laboratoire de Génétique, Centre Hospitalier et Universitaire,
Vandoeuvre les Nancy, France, 3 Service de Neuropédiatrie, Hôpital St
Jacques, Besançon, France, 4 Service de Génétique Médicale, CHU Hôtel-Dieu,
Clermont-Ferrand, France, 5 Service de Génétique Médicale, CHU Hôpital l’Archet,
Nice, France, 6 Service de Cytogénétique, CHU Hôpital de Hautepierre,
Strasbourg, France, 7 Service de Neuropédiatrie, CHU Hôpital Guy de Chauliac,
Toulouse, France, 8 Unité de Génétique Clinique, CHU Hôpital C. Nicolle,
Rouen, France, 9 Centre de Génétique Chromosomique, Hôpital St Vincent de
Paul, Lille, France, 10 Unité de Génétique, Hôpital Flaubert, Le Havre, France,
11 Département de Pédiatrie, CHU, Grenoble, France.
The CDKL5 and FOXG1 genes have been implicated in the molecular
etiology of variant forms of Rett syndrome. We screened the CDKL5
gene in a cohort of 167 patients with early-onset seizures and 10 girls
with Aicardi syndrome. The screening was negative for all males as
well as for females with Aicardi syndrome, excluding the CDKL5 gene
as a candidate for this neurodevelopmental disorder. We found 11 additional
de novo mutations in CDKL5 in female patients with a high
mutation rate (28%) in females with early-onset seizures and infantile
spasms. In addition, we screened the entire coding sequence of
FOXG1B in a cohort of 35 female patients with a classical or congenital
form of RTT and 6 males with neonatal epileptic encephalopathies
or RTT-like phenotypes. We found two female patients to be heterozygous
for nonsense mutations resulting in truncated FoxG1 transcription
factors. One patient is affected by a classic form of RTT, whereas
the other patient presents with a congenital variant of RTT. These findings
give additional support to the genetic heterogeneity in RTT, and
help to delineate the clinical spectrum in the phenotypes associated
with FOXG1 and CDKL5 mutated alleles.
P02.188
A novel p. Arg970X mutation in the last exon of the cDKL5 gene
resulting in a female with Rett syndrome-like features and mild
seizure disorder
S. Psoni 1 , P. J. Willems 2 , E. Kanavakis 1 , A. Mavrou 1 , H. Frissyra 1 , J. Traeger-
Synodinos 1 , C. Sofokleous 1 , P. Makrythanassis 3 , S. Kitsiou-Tzeli 1 ;
1 Choremio Research Laboratory, Athens, Greece, 2 GENDIA (GENetic DIAgnostic
Network), Antwerp, Belgium, 3 Department of Genetic Medicine and Development,
Faculty of Medicine, University of Geneva, Geneva, Switzerland.
Introduction: Mutations in the CDKL5 (Cyclin-Dependent Kinase-like
5) gene in Xp22 are associated with therapy-resistant seizures and
atypical Rett Syndrome (RS) features in early infancy along with severe
mental retardation. RS is a serious neurodevelopmental disorder
caused by mutations in the MECP2 gene in Xq28. In its classic form
RS mainly affects females who after a relatively normal development
during the first six months of life develop a wide spectrum of symptoms.
Several atypical forms of RS also exist, such as the Hanefeld variant
with early-onset convulsions, suggesting the implication of other genes
in the RS phenotype.
Material-Methods: We herein report a 14-year-old female with a RSlike
clinical picture, severe mental retardation, and well-controlled seizures.
Results: MECP2 gene testing was negative, but subsequent
sequencing of the CDKL5 gene revealed a novel p.Arg970X (c. 2908
C>T) mutation in the last exon. The truncated protein only misses a
small portion of the terminus, which might explain the less severe phenotype.
Conclusion: The study of the CDKL5-mutated variable phenotypes as
the one presented here, may possibly contribute to the elucidation of
the CDKL5 and MECP2-associated overlapping molecular and clinical
pathways.
P02.189
Epileptic encephalopathy in a girl with an interstitial deletion of
Xp22 comprising promoter and exon 1 of the CDKL gene
Y. Fichou1 , N. Bahi-Buisson2 , B. Girard3 , J. Nectoux1 , A. Gautier4 , Y. Saillour1 ,
K. Poirier1 , J. Chelly1 , T. Bienvenu1 ;
1Université Paris Descartes, Institut Cochin, CNRS (UMR8103), Paris, France,
2Service de Neuropédiatrie, Hôpital Necker-Enfants-Malades, Paris, France,
3Laboratoire de Biochimie et Genetique Moleculaire, Hôpital Cochin, Paris,
France, 4Service de Neuropédiatrie, CHU de Nantes, Nantes, France.
We report a two-year-old girl with early onset seizures variant of Rett
syndrome with a deletion at Xp22 detected by multiplex ligation-dependent
probe amplification (MLPA) technique. This patient presented
with tonic seizures at seven days of life. Subsequently, she developed
infantile spasms at three months and finally refractory myoclonic epilepsy.
She demonstrated severe encephalopathy with hypotonia, deceleration
of head growth, with eye gaze but limited eye pursuit, no
language, limited hand use, and intermittent hand stereotypies. This
combination of clinical features, suggestive of early onset variant of
Rett syndrome led us to screen the CDKL5 gene. In a first step, screening
of the whole coding sequence of the CDKL5 gene revealed no
point mutations. In a second step, we searched gross rearrangements
by MLPA and identified a microdeletion affecting both the promoter and
exon 1 in CDKL5. Subsequent analysis on a Nimblegen HD2 microarray
confirmed a deletion of approximately 300 kb at Xp22, including
the BEND2, SCML2 and CDKL5 genes. In conclusion, our report suggests
that searching for large rearrangements in CDKL5 should be
considered in girls with early onset seizures and Rett-like features.
P02.190
mEcP2 mutations in Bulgarian Rett syndrome patients
T. Todorov1 , A. Todorova1 , R. Tincheva2 , D. Avdjieva2 , V. Mitev1 ;
1Department of Chemistry and Biochemistry, Medical University, Sofia, Bulgaria,
2Department of Pediatrics, Medical University, Sofia, Bulgaria.
Rett syndrome (RTT) is a progressive neurodevelopmental disorder
that occurs almost exclusively in females. It is characterized by arrested
development between 6 and 18 months of age (with apparent
normal development before that). The main clinical symptoms are: regression
of acquired skills, loss of speech, stereotypical movements of
the hands, microcephaly, seizures, and mental retardation. The typical
form of RTT is caused by X-linked dominant mutation in the gene encoding
methyl-CpG-binding protein-2 (MECP2).
In total 21 female patients clinically suspected to be affected by classical
RTT were referred to our laboratory for genetic analysis of MECP2
gene. The MECP2 gene was screened for mutations by PCR/direct
sequencing.
In one patient the karyotype analysis showed abnormal result -
46,XX,del(X)(p1.22).
Five of the affected girls (23,8%) were proved to have mutations in
MECP2 gene: c.473C->T, p.Thr158Met; c.808C->T, p. Arg270X (detected
in two unrelated patients); c.880C->T, p.Arg294X; c.1157_
1200del44, p.Leu386fs. The detected mutations were all de novo.
All of our genetically proved cases were very severely affected: total
loss of speech is present in all cases, severe mental retardation, stereotypical
hand movements are present, walking without help is impossible,
seizures are invariably found in the presented girls.
Two of our patients were additionally tested for Angelman Syndrome
(AS) by Methylation Sensitive PCR analysis; 5 girls were screened for
mutations along the Cycline-dependent kinase-like 5 (CDKL5) gene
and 10 were analysed by MECP2 MLPA Kit for large deletions/duplications
detection. These additional genetic tests revealed no genetic
changes in analyzed patients.
P02.191
mouse models of mecP2 disorders share gene expression
changes in the cerebellum and hypothalamus
S. Ben-Shachar1,2 , M. Chahrour2 , C. Thaller2 , C. A. Shaw2 , H. Y. Zoghbi2 ;
1 2 Tel-Aviv Sourasky Medical Center, Tel-Aviv, Israel, Baylor College of Medicine,
Houston, TX, United States.
A group of postnatal neurodevelopmental disorders collectively referred
to as MeCP2 disorders are caused by aberrations in the gene
encoding methyl-CpG-binding protein 2 (MECP2). Loss of MeCP2
function causes Rett syndrome (RTT), whereas increased copy number
of the gene causes MECP2 duplication or triplication syndromes.