2008 Barcelona - European Society of Human Genetics

Molecular and biochemical basis of disease
P05.087
the GNE protein binds to alpha actinin 1
S. Amsili 1 , H. Zer 2 , S. Hinderlich 3 , M. Becker-Cohen 1 , D. G. MacArthur 4 , K. N.
North 4 , S. Mitrani-Rosenbaum 1 ;
1 Hadassah Hebrew University Medical Center, Jerusalem, Israel, 2 Hebrew
University of Jerusalem, Jerusalem, Israel, 3 Technische Fachhochschule Berlin,
Berlin, Germany, 4 The Children’s Hospital at Westmead, University of Sydney,
Sydney, Australia.
Hereditary inclusion body myopathy (HIBM) is a rare neuromuscular
disorder
caused by mutations in GNE, the key enzyme in the biosynthetic pathway
of sialic acid . While the mechanism leading from GNE mutations
to the HIBM phenotype is not yet understood, we searched for proteins
potentially interacting with GNE, which could give some insights
about novel putative biological functions of GNE in muscle . We used a
Surface Plasmon Resonance (SPR)-Biosensor based assay to search
for potential GNE interactors in anion exchanged fractions of human
skeletal muscle
primary culture cell lysate . Analysis of the positive fractions by in
vitro binding assay revealed α -actinin 1 as a potential interactor of
GNE . The direct interaction of the two proteins was assessed in vitro
by SPR-Biosensor based kinetics analysis and in a cellular environment
by a co-immunoprecipitation assay and confocal co-localization
in 293T cells. The interaction of GNE with α -actinin 1 might point to
its involvement in α-actinin mediated processes, including cytoskeleton
organization and signaling pathways . In addition these studies
illustrate for the first time the expression of the non-muscle form of α
-actinin, α -actinin 1, in mature skeletal muscle tissue, opening novel
avenues for its specific function in the sarcomere.
P05.088
NTRK , a gene involved in the enteric nervous system
development, is related to Hirschsprung disease
A. Sánchez-Mejías 1,2 , M. Ruiz-Ferrer 1,2 , R. M. Fernandez 1,2 , M. D. Mena 1,2 , M.
Lopez-Alonso 1,2 , G. Antiñolo 1,2 , S. Borrego 1,2 ;
1 Unidad de Gestión Clínica de Genética, Reproducción y Medicina Fetal, Hospitales
Universitarios Virgen del Rocío, Seville, Spain, 2 Centro de Investigación
Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Seville, Spain.
Hirschsprung disease (HSCR) is a developmental disorder characterized
by the absence of ganglion cells in the myenteric and submucosal
plexuses along a variable portion of the distal intestine, due to a
defect of neural crest neuroblasts migration process . Manifestation of
the disease has been linked to the dysfunction of 2 principal signalling
pathways involved in the enteric nervous system (ENS) formation: the
RET-GDNF and the EDN3-EDNRB receptor systems . Because of its
etiopathogenesis it results tempting to speculate that additional signalling
pathways implicated in intestinal neurodevelopment could also
be involved in HSCR . In this way, the NTF3/TrkC signalling pathway
had been shown to play an essential role in the development of the
ENS, together with the evidences showed by murine models lacking or
over-expressing NTF-3, and the differential localization of the receptor
in ganglionic versus aganglionic region of HSCR intestine suggest a
potential role for those genes in the pathogenesis of HSCR . We have
sought to evaluate the candidature of the NTRK3 gene, encoding the
TrkC receptor, as a susceptibility gene for Hirschsprung disease . Using
direct sequencing analysis and dHPLC technology we have screened
the NTRK3 coding region and the intron/exon boundaries in 143 Spanish
HSCR patients . A total of 4 previously described polymorphisms
and 12 novel sequence variants were detected . Of note, we have
detected a novel aminoacid substitution in the protein sequence in a
multiplex HSCR family . In silico studies point that structural alterations
might be introduced in the mutated protein, suggesting a pathogenic
role for Hirschsprung disease .
P05.089
Nrf2-related oxidative stress response and impaired dopamine
biosynthesis in a Pc12 cell model of Huntington’s disease
W. M. C. van Roon-Mom1 , B. A. Pepers1 , P. A. C. ‘t Hoen1 , C. A. C. M. Verwijmeren1
, J. T. den Dunnen1 , J. C. Dorsman2 , G. B. van Ommen1 ;
1 2 LUMC, Leiden, The Netherlands, Free University, Amsterdam, The Netherlands.
Huntington’s disease (HD) is a devastating disease for which currently
no therapy is available . It is a progressive autosomal dominant neuro-
degenerative disorder that is caused by a CAG repeat expansion in the
HD gene, resulting in an expansion of polyglutamines at the N-terminal
end of the encoded protein, designated huntingtin, and the accumulation
of cytoplasmic and nuclear aggregates . Not only is there a loss of
normal huntingtin function, upon expansion of the CAG repeat there is
also a gain of toxic function of the huntingtin protein and this affects a
wide range of cellular processes . To identify groups of genes that could
play a role in the pathology of Huntington’s disease, we studied mRNA
changes in an inducible PC12 model of Huntington’s disease before
and after aggregates became visible. This is the first study to show the
involvement Nrf2-responsive genes in the oxidative stress response
in HD . Oxidative stress related transcripts were altered in expression
suggesting a protective response in cells expressing mutant huntingtin
at an early stage of cellular pathology . Furthermore, there was a downregulation
of catecholamine biosynthesis resulting in lower dopamine
levels in culture . Our results further demonstrate an early impairment
of transcription, the cytoskeleton, ion channels and receptors . Given
the pathogenic impact of oxidative stress and neuroinflammation, the
Nrf2-ARE signaling pathway is an attractive therapeutic target for neurodegenerative
diseases .
P05.090
myBPc3 (myosin binding protein c) associated hypertrophic
cardiomyopathy in young maine coon cats appears to be a
recessive disease caused by the synthesis of mutated protein
M. T. Nyberg Godiksen 1 , I. A. Laursen 2 , T. Nielsen 3 , S. Granström 1 , P. Højrup 3 ,
J. Koch 1 , M. Christiansen 2 ;
1 Faculty of Life Sciences, University of Copenhagen, Frederiksberg, Denmark,
2 Department of Clinical Biochemistry, Statens Serum Institut, Copenhagen,
Denmark, 3 Department of Biochemistry and Molecular Biology, University of
Southern Denmark, Odense, Denmark.
Human hypertrophic cardiomyopathy (HCM) is a primary disorder of
the myocardium associated with sudden death, stroke and heart failure
. It is caused by mutations in genes coding for sarcomeric proteins .
HCM in the Maine Coon cat (MCO) is a good spontaneous model of
human HCM . Variants in the MyBPC3 gene, coding for myosin binding
protein-C (MYBP-C), are associated with human HCM . The mutation
A31P in MyBPC3 is associated with familial HCM in MCO and
we screened a large cohort of unrelated MCO cats to establish the
association between this mutation and feline HCM .
Two-hundred-eighty-seven MCO cats (mean age of 2 .2 years, 23 with
HCM) were genotyped for the A31P . Mutation screening was performed
by DNA sequencing . Heart proteins were extracted from two MCO cats,
separated by SDS-PAGE, the MYBP-C band was trypsin digested and
sequence variants identified by mass-spectrometry (MS).
A31P had a minor allele frequency of 0 .20 . The odds ratio for having
HCM was 10.7 (95%-cfi: 3.3 - 34.4) in homozygous cats. The presence
of MYBP-C with the A31P variant in heart tissue was verified by MS in
a homozygous MCO cat .
MyBPC3 associated HCM in MCO express itself as a recessive disease
in young cats, as a single A31P allele does not confer an increased risk
of HCM . However, the potential for late-onset of disease may cause
the significance of the genetic variant to be underestimated. The presence
of the A31P variant MYBP-C in hearts suggests that the disease
is caused by the presence of a “poisonous polypeptide” .
P05.091
myocyte function and gene defects in arrythmogenic right
ventricular dysplasia: clinical pnehotypes and open problems
for clinical genetics
N. Marziliano, M. Grasso, A. Pilotto, E. Serafini, M. Tagliani, E. Disabella, B.
De Giorgio, P. Cassini, M. Pasotti, E. Arbustini;
IRCCS Policlinico San Matteo, PAVIA, Italy.
Background . Desmosome proteins’ defects are associated with right
ventricular (fibro)-fatty replacement of myocardial tissue (Arrythmogenic
Right Ventricular Cardiomyopathy/Dysplasia, ARVC/D, MIM
#609040 and #107970) . The most investigated genes are: JUP (Junctional
Plakoglobin, 17q21), PKP2 (Plakophilin-2, 12p11), DSC2 (Desmocollin
2, 18q12 .1), and DSG2 (Desmoglein 2, 18q12 .1-q12 .2), DSP
(Desmoplakin, 6p24). We screened the five genes in a consecutive
series of 65 patients with ARVC/D fulfilling (n=3) and non-fulfilling
(n=62) McKenna et al . criteria and 55 DCM patients with arrhythmias,
two with suspected myocarditis, and one with a wrong diagnosis of