2008 Barcelona - European Society of Human Genetics

Molecular and biochemical basis of disease
P06.130
Association of the RET proto-oncogene to intestinal Neuronal
Dysplasia type B
R. M. Fernandez 1,2 , M. Ruiz-Ferrer 1,2 , A. Sánchez-Mejías 1,2 , M. López-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 defined by the absence of intramural
ganglia of Meissner and Auerbach along variable lengths of the gastrointestinal
tract . Intestinal neuronal dysplasia type B (INDB) is characterized
by the malformation of the parasympathetic submucous plexus
of the gut . It seems to exist a connection between these two enteric
nervous system abnormalities, supported by the fact that HSCR often
includes a region of INDB-like character proximal to the aganglionic
segment . Because of the major role played by the RET proto-oncogene
in HSCR, we sought to determine if this gene was also related to
INDB, by both a mutational screening in a series of patients, and the
evaluation of its polymorphisms/haplotypes as susceptibility factors for
this disease . We have used dHPLC techniques to screen the RET coding
region in 23 patients presenting with INDB, and 30 patients with a
combined HSCR+INDB phenotype . In addition, a total of 11 RET SNPs
were strategically selected and genotyped by using Taqman technology
. Distribution of such SNPs, as well as of the haplotypes generated
by their combinations, was compared among the different groups
of patients (INDB, HSCR+INDB, HSCR) and controls . As a result we
have demonstrated the involvement of RET in the pathogenesis of intestinal
neuronal dysplasia B, although by different molecular mechanisms
to those leading to Hirschsprung disease . Further investigation
is warranted in order to elucidate those precise mechanisms and to
clarify therefore the genetic nature of INDB .
P06.131
First Dutch founder mutation in Hereditary spastic Paraplegia
W. A. G. van Zelst-Stams 1,2 , S. G. M. Frints 1,2 , M. Gerards 1,2 , E. L. C. Jongen 1,2 ,
R. G. Janssen 1 , C. E. M. de Die-Smulders 1,2 , C. T. R. M. Schrander-Stumpel 1,2 ,
H. J. Smeets 1,2 ;
1 department of clinical genetics, university hospital Maastricht, Maastricht, The
Netherlands, 2 The Netherlands Research Institute GROW, Maastricht University,
Maastricht, The Netherlands.
Hereditary spastic paraplegia (HSP) is characterized by clinical and
molecular heterogeneity . In autosomal dominant (AD) spastic paraplegia
(SPG), SPASTIN (SPG4) and ATLASTIN (SPG3A) gene defects
account for approximately 40% and 10%, respectively .
We performed parametric linkage analysis, using the Affymetrix 10K
SNP array, to identify the SPG locus in a ten-generation Dutch pedigree
. A maximum LOD score of 5 .03 was obtained at the SPG31 locus
(2p11-p12) . Mutation analysis of the receptor expression-enhancing
protein 1 gene (REEP1) was performed in 10 additional AD SPG
families from the South-East part of the Netherlands . A truncating four
basepair deletion in exon six (c .537_540delCGGC p .Ser179ArgfsX43)
was identified which co-segregated with the disorder in the large linked
family and in two other small unrelated families, suggesting a founder
effect in our region. A founder effect was confirmed by haplotype
analysis using polymorphic markers surrounding REEP1. The clinical
features within these families ranged from normal to severe spasticity
of legs and the age of onset varied from birth till >75 years of age .
There was an inverse correlation between age at onset and severity
and progression of symptoms . Further functional studies are needed
to identify a major modifier in REEP1 affected families.
In conclusion, we identified a founder REEP1 mutation in 27% (3/11)
of the AD pure SPG families investigated in the South-East part of the
Netherlands . Thus REEP1 gene defects in HSP seem at least as common
as ATLASTIN (SPG3A) .
P06.132
Quantitative trait locus mapping in complex human pedigrees
with interpopulation origin
G. R. Svischeva;
Institute of Cytology and Genetics, Novosibirsk, Russian Federation.
We perfected the variance-components method for quantitative trait
locus (QTL) analysis of complex human pedigrees descended from
interpopulation crosses between outbred parental lines with different
QTL allele frequencies in each population . Furthermore, dominance
and inbreeding are allowed for . The updated method is based on the
decomposition of trait variance into components with the consideration
of the genetic effect conditioned by interpopulation origin and inbreeding
of individuals . To estimate model parameters, namely additive and
dominant effects, and the allelic frequencies of the QTL analysed, and
also to define the QTL positions on a chromosome with respect to genotyped
markers, we used the maximum-likelihood method . To detect
linkage between the QTL and the markers we propose statistics with
a noncentral chi-square distribution that provides the possibility to deduce
analytical expressions for the power of the method and therefore,
to estimate the pedigree’s size required for 80% power . The method
works for arbitrarily structured pedigrees and uses the phenotypic
values and the marker information for each individual of the pedigree
under observation as initial data and can be valuable for fine mapping
purposes . The power of the method is increased if the QTL effects conditioned
by interpopulation origin and inbreeding are enhanced .
P06.133
clinical and genetic investigation of three kindreds with familial
hyperparathyroidism
G. Masi, L. Barzon, M. Iacobone, A. Porzionato, V. Macchi, G. Palù;
University of Padova, Padova, Italy.
We investigated three Italian kindreds referred to our Surgery Unit for
familial hyperparathyroidism . One kindred was diagnosed as affected
by hyperparathyroidism-jaw tumor syndrome (HPT-JT), due to the occurrence
of a maxillary ossifying fibroma, the other two kindreds were
defined as familial isolated hyperparathyroidism (FIHP) because of the
occurrence of hyperparathyroidism without other syndromic manifestations
. Clinical investigation demonstrated that all kindreds shared
other clinical features besides hyperparathyroidism, i .e ., high frequency
of uterine polyposis and thyroid neoplasms . Since germline HRPT2
mutations are detected in HPT-JT kindreds, but also in 7% of FIHP kindreds,
we tested patients for HRPT2 mutations and performed immunohistochemical
analysis of parafibromin, encoded by HRPT2, in all
available tumor tissues . Germline HRPT2 inactivating mutations were
identified in the HPT-JT kindred and in both FIHP kindreds. A HRPT2
somatic mutation was also demonstrated in a parathyroid adenoma
from a FIHP patient, in agreement with HRPT2 tumor-suppressor role .
Moreover, loss of nuclear parafibromin expression was demonstrated
in all parathyroid tumors, at variance with findings in biopsies from normal
parathyroid glands . In addition, immunohistochemistry performed
on a HPT-JT-related uterine polyp did not show any nuclear anti-parafibromin
reactivity, as compared with five sporadic polyps in which almost
all stromal cells exhibited nuclear parafibromin immunostaining.
Overall, our results indicate that FIHP and HPT-JT associated with
HRPT2 mutations do not to have a distinct genetic signature, but may
represent variants of the same genetic disease. Loss of parafibromin
expression in polyps supports the pathogenetic role for parafibromin in
uterine polyposis associated with this syndrome .
P06.134
investigation the role of -344c>t polymorphism in cYP11B2
gene among Bulgarian hypertensive patients
R. Saraeva 1 , J. Matrozova 2 , R. Bogeska 1 , I. Kremensky 1 , S. Zacharieva 2 , R.
Kaneva 1 ;
1 Molecular Medicine Center, Medical University of Sofia, Sofia, Bulgaria, 2 University
Hospital of Endocrinology “Akad. Ivan Pentchev”, Sofia, Bulgaria.
Background: The renin-angiotensin-aldosterone system is often investigated
in relation to the pathogenesis of essential hypertension . The
mineralocorticoid hormone aldosterone plays an important role in blood
pressure homeostasis . A key factor for its synthesis is the enzyme aldosterone
synthase, encoded by CYP11B2 gene . The -344C>T polymorphism
in the 5’ regulatory region of the CYP11B2, which disrupts a
putative binding site for the steroidogenic factor 1, was reported to be
associated with aldosterone excess and hypertension .
Objective: Our aim was to investigate the role of functional -344C>T
polymorphism in the promoter region of CYP11B2 gene in the manifestation
of hypertension, using case-control study design .
Methods: We included 185 Bulgarian hypertensive patients and normontensive
control group . The -344C>T polymorphism was genotyped
by RCR-RFLP method using HaeIII restrictase .
Results: The genotype and allele frequencies for -344C>T variant in