2008 Barcelona - European Society of Human Genetics

Molecular and biochemical basis of disease
to this core . Additional interacting proteins assembling to the USH protein
network are candidates to be responsible for Usher syndrome,
non-syndromic hearing loss or retinal dystrophies .
Hypothesis: The protein product predicted for PDZK7 (NM_024895)
shows high homology to both harmonin and whirlin and could have a
similar function . Thus, it is a candidate member for the Usher interactome
.
Objective: The aim of the present work was to determine the existence
of interactions between PDZK7 and the proteins of the Usher
interactome: usherin, NBC3, VLGR1, cadherin 23, protocadherin 15
and SANS .
Methods: Interactions were tested by yeast two hybrid (Y2H) assays
and by co-expression and co- localization in cos-1 cells studies .
Results: No interaction was found between PDZK7 and USH proteins
.
Conclusions: The absence of interactions between PDZK7 and USH
proteins indicates that it is not part of the USH interactome .
P05.205
Assessment of hearing loss in French patients diagnosed with
pathogeneous genotypes in usherin
C. Abadie 1 , L. Larrieu 1 , D. Baux 1 , C. Blanchet 2 , S. Gerber 3 , J. Kaplan 3 , M.
Claustres 1,4 , A. Roux 1 ;
1 Laboratoire de génétique moléculaire, Inserm U827, Montpellier cedex 5,
France, 2 Centre de référence des affections génétiques sensorielles, Montpellier
cedex 5, France, 3 Inserm U393, Hôpital Necker-Enfants Malades, Paris,
France, 4 Université Montpellier I, Montpellier, France.
Usher syndrome is an autosomal recessive disorder characterised by
hearing impairment, retinitis pigmentosa (RP) and variable vestibular
dysfunction . Usher syndrome presents both genetic and clinical heterogeneity,
and is divided into 3 subtypes caused by at least 9 genes .
Usher syndrome type II (USH2) is the most frequent clinical group .
Affected patients show moderate to severe hearing loss (HL) and variable
evolution of RP . Typical USH2 audiograms have a gently downsloping
configuration from moderate in the low frequencies to severe
or profound in the high frequencies . High variability is recognised and
clinical diagnosis of USH2 can be missed suggesting that USH2 is
likely to be more frequent than estimated . USH2A is the overwhelmingly
involved gene in USH2 and encodes two isoforms of the protein
called usherin (a short isoform of 1546 residues and a long isoform of
5202 residues) .
Audiograms were collected in a french cohort of 30 patients presenting
with pathogenic genotypes in usherin . ISO 7029 norm-based calculation
was used to abolish age-related and gender bias . For a third of
these patients, audiograms could be collected over several decades
in order to assess the progression of HL . Preliminary results tend to
show a homogeneous range of hearing deficiency, either considering
the affected isoform, or the type of mutations (truncating, missense
or splice variants). However, some audiograms did not fit within the
defined range; some of them could be explained by the presence, on
one allele, of the controversial p .Cys759Phe variant .
P05.206
New mutations in VWF Gene, from mexican patients with „Von
Willebrand Disease“
R. Peñaloza, H. Benitez, V. Rojas, M. Espinosa, A. Cervantes, M. Flores, D.
Arenas, F. Salamanca;
IMSS, Mexico City, Mexico.
We analyzed exon 28 of VWF gene from 20 Mexican Mestizo index
cases with von Willebrand disease, using DNA amplification by polymerase
chain reaction and direct sequenciation using Big Dye (Applied
Biosystem, USA) . They have high frequency of blood group type
O (80%), and normal or low aPPT, VWF:Ag, VWF:RCo, and FVIII:C .
We found two novel mutations: (insT3706) and (delG4911) in patients
with VWD type 1 . Both produce an early stop with a short putative
protein. The first one corresponding to a woman with menorrhagia,
and the second one to a male with mucocutaneous bleeding to require
hospitalization . Moreover, we found other polymorphisms previously
informed . This is the second part of molecular study of VWF gene
where we informed other three new mutations, previously .
P05.207
the study of the WFs1 gene is useful in non syndromic hearing
loss, with ascending or U-shape audiometric curve
L. Jonard 1 , D. Feldmann 1 , S. Marlin 1 , C. Koval 1 , M. Louha 1 , K. Olszewski 1 , R.
Couderc 1 , H. Dollfus 2 , V. Drouin-Garraud 3 , D. Lacombe 4 , F. Fellmann 5 , C. Francannet
6 , G. Lina-Granade 7 , C. Petit 8 , F. Denoyelle 1 ;
1 AP-HP, Paris cedex 12, France, 2 Génétique médicale, Strasbourg, France,
3 Génétique clinique, Rouen, France, 4 Génétique médicale, Bordeaux, France,
5 Génétique médicale, Besançon, France, 6 Génétique clinique, Clermont-Ferrand,
France, 7 ORL Hôpital E.Herriot, Lyon, France, 8 INSERM U587, Paris,
France.
Introduction: Wolfram syndrome or DIDMOAD is characterized by the
association of diabetes, optic atrophy and hearing impairment . This
autosomal recessive syndrome is due to WFS1 gene mutations . Some
dominant mutations of the same WFS1 gene have been associated
with nonsyndromic deafness, preferentially affecting low frequencies
(DFNA6/14/38) . Unlike the Wolfram’s mutations, the dominant mutations
are essentially located in the exon 8 of the WFS1 gene .
Methods: We have analysed exon 8 of the WFS1 gene in a cohort of
64 unrelated individuals affected by nonsyndromic hearing loss (HL) .
23 individuals presented with an ascending audiometric curve and 41
presented with a U-shape curve .
Results: In four different families, we identified a heterozygous mutation:
c .923C>G (p .Ser308Cys), c .1079G>A (p .Cys360Tyr), c .2141A>G
(p .Asn714Ser) and c .2421C>A (p .Ser807Arg) . These new WFS1 variations
segregate perfectly with the HL, are missense mutations affecting
highly conserved residues, and are absent from 100 control DNA
samples .
These 4 French families are affected with isolated autosomal dominant
HL . In a same family, a mutation can cause an HL characterised by
an ascending curve or a U-shape curve, and evolution between these
two shapes has been observed . The exhaustive audiological and
clinical examination of the 17 affected patients allowed us to precise
DFNA6/14/38 phenotype .
Conclusion: The molecular screening of WFS1 gene is useful for patients
presenting with sporadic or familial non syndromic hearing loss,
with an ascending or U-shape audiometric curve . Moreover, our study
leads to clarify the spectrum of WFS1 mutations and the related phenotype
in non syndromic hearing impairment DFNA6/14/38 .
P05.208
DNA repair efficacy determines the severity of XPB associated
progeroid cockayne syndrome
J. Andressoo 1,2 , G. Weeda 3 , J. de Wit 3 , J. R. Mitchell 3 , R. B. Beems 4 , H. van
Steeg 4 , J. H. Hoeijmakers 3 , G. T. J. van der Horst 3 ;
1 Institute of Biotechnology, Helsinki, Finland, 2 Former address: Erasmus Medical
Center, Rotterdam, The Netherlands, 3 Erasmus MC, Rotterdam, The Netherlands,
4 National Institute of Public Health and Environment, Bilthoven, The
Netherlands.
Mutations in the basal transcription and nucleotide excision repair
(NER) helicase XPB associate with a mild form of the combined cancer
and premature aging syndrome xeroderma pigmentosum / Cockayne
syndrome (XPCS) . Due to the dual role of XPB and absence of animal
models, the underlying molecular mechanisms of XPB-XPCS have
remained obscure. Here, with the first Xpb mouse models we demonstrate
that severe alterations in Xpb are lethal, providing explanation to
the relative scarcity of XPB associated disease . Furthermore, we show
that knock-in mice with an XPCS-patient-derived XPB mutation mimic
the UV-sensitivity typical for XP, but fail to show CS features and age
normally . However, further ablation of DNA repair capacity by crossings
the Xpb mutant mice to other NER mutants causes appearance
of CS-like features such as premature aging and increase in cellular
sensitivity to chronic oxidative stress, demonstrating the causative
role of DNA repair defect in the onset of XPB-associated accelerated
aging . The Xpb/Xpa double mutants display a novel NER phenotype,
with intermediate severity of ageing symptoms and remarkable interanimal
variance . This large variance provides experimental evidence
to the hypothesis that stochastic DNA damage accumulation is an important
determinant of clinical variance in NER syndromes . Based on
our results, we suggest a model of NER phenotypes in which the interindividual
variation first increases and then decreases as a function of
the degree of DNA repair deficiency.