2008 Barcelona - European Society of Human Genetics

Molecular and biochemical basis of disease
Compostela, Spain.
Hereditary spastic paraparesis (HSP) is a progressive gait disorder
with spasticity of the limbs . HSP shows both clinical and genetic heterogeneity
and can be autosomal dominant (AD-HSP), autosomal
recessive or X-linked recessive . The most prevalent form of AD-HSP
involves the SPG4 locus encoding spastin, a member of the AAA family
of ATPases . The frequency of SPG4 mutations in our population is
unknown . We studied 56 patients (43 families, 33 of them Galician, 10
from other regions of Spain), most with uncomplicated forms of HSP .
The 17 exons of SPG4 and exon-intron boundaries were sequenced .
Novel mutations and sequence variations of unknown significance
were checked in 186 Galician controls. We identified six mutations,
three of them novel . The same truncating mutation was present in four
apparently unrelated pedigrees . We found four sequence variations of
unknown significance, one synonymous polymorphism and six other
sequence alterations not found in the literature or databases but unlikely
to be pathogenic (either present in controls or not co-segregating
with the phenotype when several affected family members were
available) . In summary, 9/43 families (21%) were positive for SPG4
mutations and another four families (9%) harbour sequence variations
of unknown significance. If we consider only the cases with definitive
autosomal-dominant inheritance, the frequency of SPG4 mutations
rises up to 60% in our series, confirming that SPG4 causes most of
the AD-HSP also in our community . In the cases with no mutations the
cause may be in other genes or mutations not detectable by sequencing
of the coding region .
P05.084
mutational analysis of the AcVR1 gene in italian patients with
Fibrodysplasia Ossificans Progressiva (FOP)
R. Bocciardi 1 , D. Bordo 2 , M. Di Duca 3 , F. S. Kaplan 4 , E. M. Shore 4 , M. Di Rocco
5 , R. Ravazzolo 1,6 ;
1 G. Gaslini Institute - Laboratory of Molecular Genetics, Genova, Italy, 2 National
Cancer Research Institute, Genova, Italy, 3 G. Gaslini Institute - Laboratory on
Pathophysiology of Uremia, Genova, Italy, 4 University of Pennsylvania School
of Medicine, Philadelphia, PA, United States, 5 G. Gaslini Institute - second Unit
of Pediatrics, Genova, Italy, 6 University of Genova and CEBR, Genova, Italy.
Fibrodysplasia Ossificans Progressiva (FOP, MIM 135100) is a rare
genetic disorder characterized by the presence of a congenital great
toe malformation and progressive heterotopic ossification that transforms
skeletal muscles to bone following a well-defined anatomic pattern
of progression. Heterotopic ossification begins in childhood, either
spontaneously or upon induction of stimuli such as trauma, and progresses
episodically throughout adulthood . FOP is usually sporadic,
however, some familial cases with an autosomal dominant pattern of
inheritance with variable expression have been described . Linkage
analysis in these families led to identification of ACVR1/ALK2 as the
gene responsible for FOP . All familial and sporadic cases with a classic
FOP phenotype that have been analysed are heterozygous for the
identical mutation, c .617G>A leading to R206H substitution . The only
reported exception is a recently described de novo mutation, G356R,
associated with a slowly progressing form of FOP . The ACVR1 gene
encodes the activin A type I receptor, a serine/threonine kinase receptor
for bone morphogenetic proteins (BMPs) belonging to the TGFbeta
receptor family . In this study, we report ACVR1 mutational analysis
in a group of 17 Italian FOP patients. We confirmed the presence
of the recurrent R206H substitution in 14 patients and we identified a
novel mutation (R258S) in the ACVR1 kinase domain in one patient .
We used bioinformatic tools to predict functional effects on the protein
caused by the identified mutations and constructed a 3D molecular
model of the R258S mutant in order to gain a better understanding of
the possible effects of this newly described mutation .
P05.085
Hereditary hyperferritinemia and cataract syndrome - genetic
study of a Portuguese family from the Azores
A. R. Couto 1,2 , P. Sousa 1,2 , M. Santos 1,2 , J. P. Pinheiro 1,2 , I. Dutra 1,2 , M.
Soares 1,2 , A. Palma 3 , G. Porto 2 , M. de Sousa 2 , J. Bruges Armas 1,2 ;
1 SEEBMO-HSEAH, Angra do Heroismo, Portugal, 2 IBMC-Instituto de Biologia
Molecular e Celular da Universidade do Porto, Porto, Portugal, 3 Servico Oftalmologia-HSEAH,
Angra do Heroismo, Portugal.
Hereditary hyperferritinemia cataract syndrome (HHCS) is an autosomal
dominant disorder characterised by the presence of cataracts with
markedly elevated serum ferritin levels without iron overload . Ferritin is
the major protein involved in iron storage and is composed of H and L
subunits . The translation of these subunits depends on the iron status
of the cell and is regulated by the interaction between the iron responsive
element (IRE) present in the mRNAs 5’ noncoding region and
cytoplasmic iron regulatory proteins . HHCS is caused by mutations in
the IRE of the ferritin light chain (FTL) gene .
In this study we have investigated the genetics of a three generation
Azorean kindred with typical HHCS in 3 individuals (2F;1M) . The proband
was identified, after detection of hyperferritinemia, through the
review of clinical findings and biochemical tests. Hereditary haemochromatosis
frequent mutations in the HFE, TFR2 and FPN1 gene
were screened . All participants gave informed consent before being
included in the study .
DNA was extracted from whole blood . Promoter and coding regions
of the human FTL gene were subjected to PCR amplification and sequenced
bidirectionally . Screening of HFE mutations was performed
by PCR-SSO .
The affected individuals are heterozygous for HFE mutation, H63D .
Sequencing of FTL gene in the affected individuals identified a heterozygous
mutation in position 47 relative to transcription initiation site
in the descending part of the IRE (47G>A) . None of the unaffected
individuals from the family had the referred mutation .
P05.086
Identification of eight novel mutations in German patients with
Hereditary Hemorrhagic telangiectasia (HHt) and detection of a
significant association between mutations in the ACVRL gene
and liver involvement
H. Frye-Boukhriss 1 , M. Mälzer 1 , M. Abramowicz 2 , M. J. Bahr 3 , N. von Beckerath
4 , C. Bergmann 5 , M. Caselitz 3,6 , E. Holinski-Feder 7 , P. Muschke 8 , K. Oexle 9 ,
G. Strobl-Wildemann 10 , G. Wolff 11 , E. A. El-Harith 1 , M. Stuhrmann 1 , K. Brakensiek
1 ;
1 Institut für Humangenetik, Medizinische Hochschule Hannover, Hannover, Germany,
2 Department of Genetics, Free University of Brussels, Brussels, Belgium,
3 Abteilung für Gastroenterologie, Hepatologie und Endokrinologie, Medizinische
Hochschule Hannover, Hannover, Germany, 4 1. Medizinische Klinik rechts der
Isar, Technische Universität München, München, Germany, 5 Institut für Humangenetik,
Universitätsklinikum der RWTH, Aachen, Germany, 6 Medizinische
Klinik, Klinikum Deggendorf, Deggendorf, Germany, 7 Medizinisch Genetisches
Zentrum (MGZ), München, Germany, 8 Institut für Humangenetik, Universitätsklinikum
Magdeburg, Magdeburg, Germany, 9 Institut für Humangenetik, Technische
Universität München, München, Germany, 10 Praxis Strobl-Wildemann,
Passau, Germany, 11 Institut für Humangenetik, Universität Freiburg, Freiburg,
Germany.
Background: Hereditary hemorrhagic telangiectasia (HHT), or Osler-
Weber-Rendu disease, is an autosomal dominant inherited disorder
of the vascular tissue . This genetically heterogeneous multi-systemic
dysplasia shows a wide variation in its phenotypic expression . Up to
78% of the HHT patients show hepatic arteriovenous malformations
(HAVM), but the molecular basis of liver involvement is still unknown .
In approximately 75% of the patients, mutations can be identified by
sequencing of the two known HHT genes, ACVRL1 (ALK1) and ENG .
Genotype-phenotype correlations are not yet fully defined, but previously,
we and others showed that hepatic involvement is associated
with ACVRL1 mutations, but rarely caused by mutations in the ENG
gene .
Patients and methods: In a new cohort of 18 adult HHT patients we
performed sequencing analysis of the ACVRL1 and ENG gene .
Results: Eight novel and 8 already described mutations (10 missense
mutations, 2 small in-frame deletions, 3 premature stop mutations
and 1 small frameshift deletion) were identified. Analysis of our entire
data revealed statistically significant differences in the distribution of
ACVRL1 and ENG mutations among HHT patients with and without
HAVM (p=0 .0016) .
Conclusion: Our data support the growing evidence for a significant
correlation between mutations in the ACVRL1 gene and liver involvement
in HHT, and suggest that molecular genetic testing in HHT patients
is important for prognosis with respect to liver disease .