European Human Genetics Conference 2007 June 16 – 19, 2007 ...

Molecular and biochemical basis of disease
Hospital Antwerp, Antwerpen, Belgium.
Andermann syndrome (OMIM 218000) or agenesis of the corpus callosum
with peripheral neuropathy (ACCPN) is an autosomal recessive
trait characterised by severe progressive motor and sensory neuropathy,
mental retardation and a variable degree of agenesis of the
corpus callosum. The disease is rare, but has a high prevalence in
the province of Quebec, Canada due to a founder effect. Up to date
five different protein-truncating mutations and one missense mutation
were found in the gene that encodes the solute carrier family 12 (potassium/chloride
transporters), member 6 (SLC12A6)(1,2).
Here we report a Turkish family with a novel homozygous truncating
mutation in SLC12A6 in 2 sibs. The patients have agenesis of the
corpus callosum and motor and sensory neuropathy consistent with
the diagnosis of Andermann syndrome. Mutation screening was performed
by sequencing analysis of all coding exons and intron/exon
boundaries of SLC12A6 (NM_133647.1). In exon 21, a 1-bp deletion
was detected at nucleotide position 2902 (c.2902delC). This mutation
is predicted to cause a frameshift and a premature stop (Arg968fsX6),
deleting the K-Cl co-transporter domain of the SLC12A6 protein. The
mutation was homozygous in both patients; the asymptomatic parents
were heterozygous for the sequence variation. This study extends the
spectrum of SLC12A6 mutations observed in patients with Andermann
syndrome.
1. Howard HC et al. Nat Genet 2002; 32(3):384-392.
2. Uyanik G et al. Neurology 2006; 66(7):1044-1048.
P0643. Exclusion of SARA2 gene in 2 families with genetic lipid
malabsorption syndrome: Anderson’s disease (or Chylomicron
Retention Disease).
M. Varret 1 , M. Parisot 2 , M. Silvain 3 , A. Grodet 4 , A. Munnich 1 , C. Boileau 1 , L.
Ferkdadji 5 , L. P. Aggerbeck 3 , J. Schmitz 6 , M. E. Samson-Bouma 7 ;
1 INSERM U781, Paris, France, 2 INSERM U781, Paris, France, 3 Centre de Génétique
Moléculaire, CNRS, Gif sur Yvette, France, 4 INSERM U773 / Université
Paris VII D Diderot, Paris, France, 5 Service d’Anatomie Pathologique, Hôpital R
Debré, Paris, France, 6 Département de Pédiatrie, Hôpital Necker-Enfants Malades,
Paris, France, 7 INSERM U773, Paris, France.
The study of naturally occurring mutations in hypocholesterolemic patients
presenting with lipid malabsorption syndrome has been useful
in identifying new target for lipid-lowering therapy. Anderson’s disease
(or Chylomicron Retention Disease), is a very rare lipid malabsorption
syndrome, usually diagnosed in early infancy, characterized by
an inability to export dietary lipids as chylomicrons due to a recessive
genetic defect in lipoprotein secretion. Recently, the molecular basis
of this defect was shown to be due to mutations in the SARA2 gene
encoding the Sar1b protein. This protein is involved in the vesicular
transport between the endoplasmic reticulum and the Golgi apparatus.
We report here 4 patients from 2 families, clearly diagnosed as
Anderson’s disease patients. They had low levels of cholesterol and
of lipid soluble vitamins. No chylomicrons were secreted after a fat
load, and alpha and betalipoproteins were 50% of normal. Endoscopy
showed a typical white stippling-like hoar frosting covering the intestinal
mucosal surface. Ultrastructural examination of intestinal biopsies
showed an accumulation of free lipid and lipoprotein-like particles, reflecting
the secretory defect. Direct sequencing of the 7 exons of the
SARA 2 gene revealed no mutation. This result thus excludes, in these
patients, SARA2 as the molecular basis of the lipoprotein secretory
defect and suggests the existence of at least another gene. Proteins
involved in the intracellular processing of chylomicron secretion would
be good candidates.
Informed written consent was obtained from all participants or from
their legal guardians (RBM 93018, CCPPRB 94002).
P0644. Two novel mutations in the AR gene in Greek patients
with complete androgen insensitivity syndrome
A. Galani 1 , C. Sofocleous 1 , F. Karahaliou 2 , A. Papathanasiou 3 , S. Kitsiou-Tzeli 1 ,
E. Kanavakis 1 , A. Kalpini-Mavrou 1 ;
1 Department of Medical Genetics, Choremeio Research Laboratory, Agia Sofia
Children’s Hospital, Athens, Greece, 2 Department of Growth and Development,
P. and A. Kyriakou Children’s Hospital, Athens, Greece, 3 Department of Endocrinology,
P. and A. Kyriakou Children’s Hospital, Athens, Greece.
Androgen Insensitivity Syndrome (AIS) is an X-linked disorder, characterized
by incomplete or absent virilization in 46XY individuals, caused
by mutations along the Androgen Receptor (AR) gene. We report on
two novel mutations, one frameshift (Gln711ArgfsX787) and one missense
(Leu881Pro) detected in two unrelated patients referred with
complete AIS. Patients 1 and 2, aged 9 and 14 years old respectively,
had a 46, XY karyotype but exhibited a complete female phenotype.
Both presented with inguinal hernia, while patient 2 also reported primary
amenorrhea. PCR reaction was performed for exons 2-8 of the
AR gene followed by direct sequencing. The Gln711ArgfsX787 mutation,
revealed in patient 1, concerns a single nucleotide deletion
(2494delA) at codon 711. This frameshift mutation results in glutamine
to arginine substitution at that position as well as in the formation of a
premature stop codon at position 787. Further molecular analysis revealed
the same mutation in patient’s mother as well as in two affected
with CAIS maternal aunts. The Leu881Pro mutation, detected in patient
2, is a single base alteration (3004 T>C) that results in leucine to
proline substitution at position 881. Molecular analysis of the patient’s
mother revealed normal alleles in her peripheral blood thus implying
that the mutation is either de novo or the result of a possible gametic
mosaicism. Both mutations are reported for the first time and provide
further evidence on the phenotypic outcome of various AR mutations.
Acknowledgements
The project is co-financed within Op. Education by the ESF (European
Social Fund) and National Resources.
P0645. G743E mutation in the androgen receptor gene detected
in a familial primary amenorrhea
R. Braham1 , S. Trimeche1 , B. Lakhal1 , H. Elghezal1 , M. Gribaa1 , F. Audran2 , C.
Sultan2 , L. Chaieb1 , A. Saad1 ;
1 2 Hopital Farhat Hached, Sousse, Tunisia, Hopital Lapeyronie, Montpellier,
France.
Androgen insensitivity syndrome (AIS) is an X-linked genetic disorder
of male sexual differentiation caused by mutations in the androgen
receptor (AR) gene. The defects of receptor function that have been
characterized fall into two categories. The first are those that disrupt
the primary sequence of the AR. The second is that which is caused by
single amino acid substitutions within the AR protein. Mutations in the
AR gene result in a wide range of AIS phenotypes.
We report here a new case of amino acid replacement G◊E at codon
743 in exon 5 within the hormone binding domain of the AR in a 17year-old
pubertal female who consulted for primary amenorrhea. She
had a family history of amenorrhea (2 aunts) but no history of ambiguous
genitalia. She had fully developed breasts, pubic hairs, and
no axillary hair (Tanner stage M4, P3, A0). External genitalia were a
normally sized clitoris, normal labia majora and minora. The following
serum levels of hormones were determined: Testosterone, 9,6 ng/
ml; estradiol, 50 pg/ml and LH, 5,6 mUI/ml. A sonogram of the pelvis
demonstrates the absence of uterus and the presence of testes in the
inguinal canal. The karyotype was 46,XY. This female phenotype with
pubic hair is defined as partial AIS.
At our knowledge, this mutation was identified in only one case led to
complete AIS. With the advent of molecular analysis of the AR gene,
it was hoped that a correlation between a molecular defect and a particular
phenotype could be established.
P0646. Analysis of molecular defects in Polish Angelman
Syndrome patients
M. Gos1,2 , A. Szpecht-Potocka1 , R. Struniawski1 , J. Polosak1 , M. Laniewski-
Wolk1 , J. Bal1 , T. Mazurczak1 ;
1 2 National Research Institute of Mother and Child, Warsaw, Poland, MSCM
Cancer Center and Institute of Oncology, Warsaw, Poland.
Angelman Syndrome (AS) is a rare neurogenetic disorder that is
caused by impaired UBE3A gene expression resulting from changes
in the parental genomic imprinting or specific mutations. Four known
types of molecular defects might be responsible for the AS: deletion
of 15q11-q13 region, paternal uniparental disomy, imprinting defects
or UBE3A mutations. The imprinting defects may result from microdeletion
of the imprinting center or somatic mosaicism. The aim of the
study was the identification of molecular defect in the patients with
clinical manifestation of AS.
Two hundred twelve patients with clinical symptoms of AS were included
in the study. First, the analysis of imprinting defect was done
with PCR-based DNA methylation analysis of PW71 and SNRPN loci
(MS-PCR). When the mosaic methylation pattern was detected, the
quantitative methylation assay (QAMA) has been performed (28 cas-
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