2009 Vienna - European Society of Human Genetics

Molecular basis of Mendelian disorders
further clarify the proportion of FTLD and AD cases attributable to mutations
in these genes, the frequency of the mutations in a Portuguese
clinical series of familial FTLD and familial AD patients referred to our
laboratory for genetic testing between 2005 and 2009 was evaluated.
Fourteen patients were genetically tested only for AD, 60 only for FTLD
and 53 for both diseases with PCR and direct sequence analysis.
Eleven different mutations have been identified in 14 out of the 127
patients: two known and one novel missense mutation in the MAPT
gene and four novel PGRN mutations. Three of these PGRN mutations
caused frameshift while one resulted in abnormal splicing as
demonstrated with RT-PCR. Functional tests in cell lines are still running.
Two known mutations in PSEN1 gene and one known mutation
in PSEN2 were also found.
According to the initial clinical diagnosis mutation frequency in MAPT
and PGRN were in the lower range of those described in other studies.
The five novel mutations found in MAPT and PGRN suggest that
both genes should be tested routinely in patients presenting clinically
with FTLD.
P12.016
molecular spectrum of androgen receptor gene alterations in
Belgian patients.
S. J. A. Van Dooren1 , R. Vijzelaar2 , S. Seneca1 , M. De Rycke1 , I. Liebaers1 , W.
Lissens1 ;
1 2 Centre for Medical Genetics, UZ Brussel, Brussels, Belgium, MRC Holland,
Amsterdam, The Netherlands.
Alterations throughout the androgen receptor (AR) gene influence
male reproductive development and function and are associated with
androgen insensitivity syndrome (AIS), a disease with a prominent genotypic-phenotypic
heterogeneity.
We determined the AR gene sequence in 21 patients. Ten patients
were suspicious of AIS. 4/6 with known 46,XY karyotype had complete
AIS (CAIS) and 1/6 had premature amenorrhea. The presence of
an Y-chromosome was confirmed in 2 patients by AR-MLPA, whereas
karyotypes remained unknown for 2 AIS patients.
Three nonsense mutations were discovered at codons 353, 829 and
831 respectively, and a 4bp duplication c.2227_2230dupATGG were
found to induce a premature stopcodon at codon 769. Two missense
mutations at codon 700 and 860 were detected within the AR ligand
binding domain. Suspicion of AR-gene or -exon deletion in 2 patients,
was corroborated by AR-MLPA, demonstrating the importance of confirmation
methodology. For the remaining 6 patients (few clinical and/
or karyotype information was available and) no AR-alterations were
found. Carrier status was confirmed in 5 investigated relatives of some
of the index cases.
Our study has revealed a number of previously undescribed amino
acid alterations presumingly causing impairment of the AR protein
function.
Our findings demonstrate that AR sequencing and MLPA are important
tools to support the clinical diagnosis and counseling of AIS. Moreover,
the AIS genetic testing may be used for prenatal diagnosis and pre-implantation
genetic diagnosis, for which the CAG-repeat in exon 1 can
be used as marker.
P12.017
tRAF6 dependent EDARADD ubiquitination is necessary for NF-
KB activation and is impaired in Anhidrotic ectodermal dysplasia
E. Bal1 , C. Cluzeau1 , N. Chassaing2 , G. Courtois1 , A. Munnich1 , P. Calvas2 , A.
Smahi1 ;
1 2 INSERM U781, hôpital Necker, Paris 15ème, France, Service de Génétique
Médicale, Hopital Purpan, CHU Toulouse, France.
Anhidrotic ectodermal dysplasia (EDA) is a disorder characterized by
sparse hair, abnormal or missing teeth and inability to sweat. EDA has
been ascribed to at least three genes encoding ectodysplasin (EDA1),
EDA-receptor (EDAR) and EDAR associated death domain (EDAR-
ADD). Ectodysplasin bind to its receptor, EDAR which in turn recruit
EDARADD to activate NF-κB downstream signalling pathway. EDAR/
NF-κB signalling is necessary to skin appendages develomentdevelopment.
Through a yeast two-hybrid screening of keratinocytes cDNA library,
using EDARADD as a bait, we have isolated TAB2 as a partner of
EDARADD and demonstrated the involvement of TAB2/TRAF6/TAK1
complex in EDAR/NF-κB NF-KB signalling pathway. TRAF6 is as an
E3 ubiquitin ligase which plays a key role in skin appendages formation.
Indeed, TRAF6-deficient mice showed a similar phenotype to
mouse homologous EDA. We have demonstrated that EDARADD interact
with TRAF6 via the EDARADD death domain. In addition, we
have demonstrated that EDARADD is ubiquitinated and that this ubiquitination
is dependent on TRAF6 activity and involve probably lysine
63 ubiquitin chains. We have identified a novel mutation in EDARADD
(c.402-407del ; p.Thr135-Val136 del) responsible for a sever autosomal
recessive form of EDA which abolished NF-κB activity. Interestingly
this mutation impaired EDARADD ubiquitination but not the interaction
with TRAF6. Together, our studies showed that EDARADD ubiquitination
is required for the ectodysplasin-induced NF-κB activation.
P12.018
Combined indirect strategy for efficient genetic diagnosis of
autosomal recessive retinitis pigmentosa
D. Cantalapiedra1 , A. Ávila-Fernández1 , M. A. López-Martínez1 , C. L. Aúz-Alexandre1
, E. Vallespin1 , M. García-Hoyos1 , R. Riveiro-Álvarez1 , J. Aguirre-Lambán1
, M. Cortón2 , M. J. Brión2,3 , Á. Carracedo2,3 , C. Ayuso1 ;
1Genetics department, Fundación Jiménez Díáz - CIBERER, Madrid,
Spain, 2Grupo de Medicina Xenómica, Universidad de Santiago de
Compostela, 
CIBERER, Santiago de Compostela, Spain, 3Fundación Pública
Galega de Medicina Xenomica, Complexo Hospitalario Universitario de Santiago,
Santiago de Compostela, Spain.
Autosomal Recessive Retinitis Pigmentosa (arRP) is a retinal dystrophy
characterised by its high degree of genetic and allelic heterogeneity,
which makes its molecular diagnosis difficult and tedious. In an
effort to significantly reduce the workload, sixteen arRP genes were
studied in 199 Spanish families (83 arRP and 116 sporadic cases or
sRP) with STR and SNP genetic markers, and were also screened for
mutations with a genotyping microarray. Cosegregation and homozygosity
analysis were performed after the genotyping process.
The overall power to rule out genes of both the STR and SNP methods
is very similar, with an average of 11.17 genes (69.82%) and 11.54
genes (72.14%) respectively, taking only into account those families
with 2 or more affected genotyped individuals. Twice as many homozygosity
alerts were obtained with SNPs, but the ones in common with
the STR analysis matched the mutated genes in all 4 fully-characterised
control families.
Our study allows discarding many genes and prioritising the mutational
screening of the remaining ones, based on homozygosity. Both indirect
approaches give similar results when discarding genes. A diagnostic
method for arRP and sRP families is proposed, which maximises the
probability of reaching a successful molecular diagnosis for each family,
making a more rational and cost-effective use of resources by
means of computer automation and the combined use of STRs and
SNPs.
P12.019
Genetic diagnosis of Ataxia telangectasia and role of
mitochondria on it
M. Houshmand, M. Rouhi Moghadam;
Genetic department, Special medical center, Tehran, Islamic Republic of Iran.
Ataxia telangiectasia (AT) is an autosomal recessive disorder..Although
the preferred method is the direct mutation analysis of the ATM
gene,the large size of the ATM gene with 63 exons and the large number
of possible mutations in patients considerably limit efficiency of
mutation analysis as a diagnostic choice.Indirect molecular diagnosis
using ATM-related molecular markers facilitates prenatal diagnosis of
AT children. In ½Q1_ this study, four molecular markers: D11S2179,
D11S1787, D11S535, D11S1343 are genotyped in 19 unrelated families
from different regions of Iran. . Amplified products by PCR method
were separated using denaturing PAGE gels. In all families, segregation
of alleles was according to Mendelian inheritance, and affected
chromosomes were distinguishable from unaffected ones. All carriers
and affected patients were diagnosed accurately. Thus, this method is
effectively useful in prenatal diagnosis of AT.
We also investigated mt-DNA deletions and haplogroups in AT patients.
In this study, 24 Iranian patients suffering from AT and 100 normal controls
were examined. mt-DNA examined by 6 primers for existence of
mitochondrial deletions. We also amplified and sequenced the mtDNA
HVS-I by standard sequencing techniques. mtDNA deletions were observed
in 54.1% (13/24) of patients (8.9 kb deletion in all samples,