2008 Barcelona - European Society of Human Genetics

Molecular and biochemical basis of disease
amyloidosis .
Methods . The ARVC/D was diagnosed on McKenna et al . criteria
(1994), the DCM according to the WHO criteria. The coding and flanking
regions of the five genes were analysed by direct automated sequencing
of the heteroduplex amplicons .
Results. We identified 38 mutations in 110 index patients (24 of the
65 ARVC/D patients and 14 of the 55 DCM patients), with 4 patients
carrying double/compound heterozygous mutations and 2 carrying a
triple heterozygosity; the segregation of the gene defects with the phenotype
was confirmed in the 3 probands who fulfilled the criteria of
ARVC/D: two carried a missense and frameshift mutations and one a
frameshift mutation .
Conclusions . The recurrence of double/triple mutants raises serious
problems in molecular diagnosis and family study, especially when the
family is small and segregation cannot be assessed, in particular the
prediction of the development of the disease in young mutation carriers
. Due to the current uncertainties, healthy mutation carriers should
undergo regular clinical monitoring .
P05.092
Development of a method for the genetic screening of 537
mutations associated with hypertrophic cardiomyopathy and
analysis of a large cohort of patients
M. Hermida-Prieto 1 , L. Monserrat 2 , M. I. Rodriguez-Garcia 3 , J. Gimeno-
Blanes 4 , F. Marín-Ortuño 4 , L. Cazón 1 , I. Alvariño 1 , M. Brión 5 , A. Carracedo 5 , A.
Castro-Beiras 2 ;
1 Instituto de Ciencias de la Salud, La Coruña, Spain, 2 Complejo Hospitalario
Universitario Juan Canalejo, La Coruña, Spain, 3 Instituto de Ciencias de la
Salud - RECAVA, La Coruña, Spain, 4 Hospital Virgen de la Arrixaca, Murcia,
Spain, 5 Centro Nacional de Genotipado, nodo de Santiago de Compostela, La
Coruña, Spain.
More than 500 different mutations have been associated with the development
of hypertrophic cardiomyopathy (HCM) . However, genetic
diagnosis has not been till now a useful tool for clinicians because of
its limited availability and high cost .
Objectives: the development of a genotyping platform to identify all
the mutations that have been associated with HCM, to perform the
screening of a large cohort of patients with HCM with this platform,
and to evaluate the clinical factors associated with the presence of
mutations .
Methods: We analyzed by Massarray SNPtyping 537 mutations in 15
genes: MYH7 (224), MYBPC3 (169), TNNT2 (37) TPM1 (11), ACTC
(7), MYH6 (5), MYL2 (11), MYL3 (5), MYLK2 (1), MYO6 (1), PRKAG2
(9), TCAP (2), TNNC1 (3), TNNI3 (33) and TTN (9) in 773 consecutive
index patients with HCM .
Results: We identified 74 different mutations (MYBPC3 34, MYH7 24,
TNNT2 5, TNNI3 5, TPM1 2, TNNC1 1, MYH6 1, ACTC 1, MYLK2 1)
in 163 different patients (21%) (MYBPC3 in 98 pts, MYH7 43, TNNI3
11, TNNT2 10, ACTC 7, MYH6 6, TPM1 2, MYLK2 2, TNNC1 1)(17 patients
had 2 mutations and 1 was homozygous) . Mutations were found
in 100/392 pts from center C (26%), 37/147 from center M (25%) and
26/234 from center A (16%) .
Conclusions: Genetic screening of known mutations in HCM provides
the identification of mutations in 20 to 40% of our index patients. The
likelihood of a positive diagnosis is higher in patients with familial disease
and in patients with sudden death risk factors .
P05.093
Unusual presentation of Kelley-Seegmiller syndrome
I. Sebesta 1,2 , B. Stiburkova 1 , J. Minsk 1 , L. Dvorakova 1 , M. Hrebicek 1 , I. Rychlík 3 ,
Z. Vernerova 4 ;
1 Institute of Inherited Metabolic Disorders, Prague, Czech Republic, 2 Institute
of Clinical Biochemistry, Prague, Czech Republic, 3 2nd Department of Internal
Medicine,Third Faculty of Medicine, Prague, Czech Republic, 4 Department of
Pathology,Third Faculty of Medicine, Prague, Czech Republic.
Kelley-Seegmiller syndrome means partial deficiency of hypoxanthineguanine
phosphoribosyltransferase (HPRT), which is an X-linked genetic
defect of purine metabolism . Characteristic features are hyperuricemia,
nephrolithiasis and gout, resulting from uric acid overproduction
. Female carriers have somatic cell mosaicism of HPRT activity,
and are healthy with normal enzyme activity in erythrocytes . Only few
females suffering from gout with this disorder were described .
We report a 50 year-old woman, who did not experience neither gout,
nephrolithiasis nor hyperuricemia . She was never on allopurinol . Uric
acid was quantified by specific enzymic method and erythrocytes enzyme
with plasma purine metabolites were measured by HPLC methods
. Detailed purine biochemical investigations revealed in repeat
serum uric acid concentrations within normal limits (314±12 μmol/);
increased plasma levels of hypoxanthine:19.8 μmol/l (control values
2.5±1.0 μmol/l ) and xanthine: 7.5 μmol/l (control values 2.4±0.7 μmol/l
); HPRT activity in erythrocyte lysate was surprisingly very low: 8 .6
nmol/h/mg Hb (control values :113 ±11 nmol/h/mg Hb) . Mutation analysis
using direct sequencing revealed heterozygous form of previously
described mutation in the 3 rd exon of HPRT gene, c .215A>G (Y72C) .
Subsequent analysis showed skewed X-inactivation ratio in favour of
mutant allele (> 25:75), which could explain enzyme defect . Although
enzyme deficiency with urate overproduction (presenting as high plasma
oxypurines) is evident, the reason for normal serum urate concentrations
remains uncertain . Such results have not been reported in a
female with HPRT deficiency. In conclusion our finding shows the need
of detailed purine investigation in asymptomatic female members of
family with partial HPRT deficiency.
P05.094
Heterochromatic genes undergo epigenetic changes and escape
from silencing in icF syndrome
M. Brun1 , E. Lana1 , C. Grunau1 , A. Mégarbané2 , G. Lefranc1 , P. Sarda3 , A. De
Sario1 ;
1 2 CNRS UPR 1142, Montpellier, France, Saint-Joseph University, Beiruth, Lebanon,
3Hopital Arnaud de Villeneuve, Montpellier, France.
ICF (Immunodeficiency, Centromeric Instability, and Facial Anomalies),
is a rare autosomal-recessive disorder . Most of the ICF patients
were born from consanguineous marriages and about 60% have mutations
in the DNMT3B, a de novo DNA methyltransferase . ICF syndrome
is characterized by a marked immunodeficiency (patients tend
to have low levels of immunoglobulins); facial anomalies are a heterogeneous
trait and centromeric instability is the most typical feature of
the disease . The juxtacentromeric heterochromatin of chromosome 1,
9, and 16 is markedly undercondensed and is involved in chromosome
rearrangements and multiradiate associations . The instability correlates
with a severe hypomethylation of the classical satellites 2 and 3,
which are the major components of constitutive heterochromatin . It is
unknown how loss of DNA methylation in non-coding sequences accounts
for the multiple symptoms associated with the ICF syndrome .
Having observed that in tumor cells and cancer cell lines heterochromatic
genes become hypomethylated and escape from silencing, we
asked whether the same process is found in ICF syndrome . In this
work we showed that heterochromatic genes are strongly hypomethylated
and some of them escape from silencing in ICF cells relative to
controls . Having observed that some heterochromatic genes remain
silent, in spite of loss of methylation, we concluded that hypomethylation
is necessary but not sufficient to have transcription in heterochromatic
regions . ChIP experiments will show whether the activation of
heterochromatic genes is regulated by histone modifications. Aberrant
transcription of heterochromatic genes may contribute to some of the
symptoms that are associated with ICF syndrome .
P05.095
clinical and molecular study of SCN A-related Epilepsy in
iranian families
A. Ebrahimi 1 , H. Tonekaboni 2 , S. Zeinali 3 , M. Houshmand 1 ;
1 NIGEB, Tehran, Islamic Republic of Iran, 2 -Shahid Beheshty Medical science
University, Tehran, Islamic Republic of Iran, 3 Biotechnology Research Centre,
Pasteur Institute of Iran, Tehran, Islamic Republic of Iran.
SCN1A-related seizure disorders encompass a spectrum that ranges
from simple febrile seizures (FS) and generalized epilepsy with febrile
seizures plus (GEFS+) at the mild end to Dravet syndrome at
the severe end . The phenotype can vary even within the same family .
SCN1A-related seizure disorders are inherited in an autosomal dominant
manner . Most SCN1A-related Seizures are the result of a de novo
heterozygous mutation .The proportion of cases caused by de novo
mutations varies by phenotype .The percentage of probands with an
SCN1A-related seizure disorder and an affected parent decreases
as the severity of the phenotype in the proband increases . Material
and methods: Diagnostic classification of patients followed on Classification
and Terminology of the International League Against Epilepsy