2008 Barcelona - European Society of Human Genetics

Molecular and biochemical basis of disease
activation capacity of the mutants in FOXL2 expressing granulosa-like
cells (KGN) . Several mutants led to a loss-of-function, while others
might induce a dominant negative effect . Interestingly, one mutant that
is located outside the FHD (S217F), proved to be hypermorphic and
to have no effect on intracellular protein distribution . Clinically this mutation
gives rise to a mild BPES phenotype, and to growth hormone
deficiency. In general, missense mutations located in the FHD lead to
a classical BPES phenotype, but cannot be correlated with the presence
of an ovarian phenotype . However, a potential predictive value
of localization and transactivation assays in the making of genotypephenotype
correlations is proposed. In conclusion, this is the first study
to demonstrate that a significant number of missense mutations in the
FHD of FOXL2 lead to mislocalization, protein aggregation and altered
transactivation, and to provide insights into the pathogenesis associated
with missense mutations of FOXL2 in human disease .
P05.053
the spectrum of GALt gene mutations in south regions of
Russia
S. Mordanov, F. Lagkueva, S. Matulevich, S. Amelina, G. Listopad, S. Kutsev;
Rostov State Medical University, Rostov-on-Don, Russian Federation.
Galactose-1-phosphate uridyltransferase (GALT) deficiency galactosemia
is clinically heterogeneous autosomal recessive disorder . Newborn
screening can identify patients with GALT deficiency galactosaemia.
The diagnosis needs to be confirmed by enzyme activity test. Unfortunately,
in many cases the results of GALT activity measurement
can be ambiguous and further molecular testing is required . More than
200 point mutations were revealed in the GALT gene, but the prevalence
of these mutations varies among ethnic groups . Classical galactosemia
newborn screening was started in Russia during 2006/2007
years . Total of 160 990 newborns were screened in South Russia and
11 patients with galactose level more than 7,2 mg/dL were revealed .
Blood samples of this patients were submitted for confirmatory testing
for classical galactosaemia . The GALT gene were sequenced in
all cases. The mutational spectrum included five missense mutations
M142L, H186Y, Q188R, K285 N, N314D . The classical galactosemia
was revealed in 4 cases with genotypes Q188R / Q188R, K285 N /
M142L, H186Y / N, K285N / N; Duarte variant was revealed in 5 cases
with genotypes Q188R / N314D, Q188R / N314D, , N314D / N314D,
N314D / N, N314D / N . In 2 cases mutations were not founded
P05.054
Novel mutations in the gap junction gene GJB2 show that
keratoderma is associated with connexin protein transport
defects
M. A. M. Van Steensel1 , E. A. de Zwart-Storm1 , P. Martin2 , M. van Geel1 ;
1 2 University of Maastricht, Maastricht, The Netherlands, University of Glasgow,
Glasgow, United Kingdom.
Mutations in the skin expressed gap junction gene GJB2 (coding for
connexin26) cause a plethora of sometimes severe skin disorders with
sensory deafness. Specific mutations are associated with distinct phenotypes
and the reasons for this strong genotype-phenotype correlation
are poorly understood . Commonly used functional parameters of
gap junction functionality, such as dye transfer and electrical conductance,
do not correlate with disease phenotype or severity . We have
now identified a number of novel mutations that are specifically associated
with palmoplantar keratoderma. Using fluorescent fusion proteins,
we show that this skin symptom may be specifically caused by protein
transport defects . What’s more, its severity is inversely correlated to
that of the transport defect . We are now working to understand the
cellular sequelae of the disturbed protein trafficking. Preliminary data
indicate that ER stress responses may be involved .
P05.055
Analysis of GJB2 gene exon 2 in Latvian patients with
nonsyndromic sensorineural hearing loss
O. Sterna 1,2 , N. Pronina 1 , I. Grinfelde 1 , S. Kuske 3 , D. Bauze 1 , R. Lugovska 1 ;
1 Medical Genetics clinic, University Children’s Hospital, Riga, Latvia, 2 Rigas
Stradins University, Riga, Latvia, 3 Latvian Childrens` Hearing centre, Riga,
Latvia.
Background: Nonsyndromic hearing impairment (NSHI) is the most
common form of deafness . Mutations in the GJB2 gene, which encodes
gap-junction beta-2 protein (connexin 26), are the main cause
of recessive NSHI. It has been identified that one particular GJB2 mutation
named 35delG is the most prevalent for the populations of the
European origin .
Materials: We obtained DNA samples from patients with prelingual
NSHI in whom syndromic forms and environmental causes of deafness
had been excluded, their relatives and individuals with hearing
loss positive family history .
Methods: DNA was extracted from whole blood . The GJB2 gene exon
2 analysis was performed using PCR, enzymatic restriction and automated
sequencing .
Results: 55 unrelated patients were screened for the GJB2 mutations .
Mutations were detected in 67 of 110 (61%) tested alleles . Four different
mutations in the GJB2 gene have been identified in Latvian
patients with NSHI: 35delG, 311-324del14, 235delC and M34T . 28 patients
(51%) are homozygous for 35delG mutation, four patients (7%)
are compound heterozygotes for 35delG and 311-324del14 mutations,
one patient (2%) has genotype 35delG/235delC and one patient (2%)
is heterozygous for M34T mutation . One heterozygous 51del12insA
mutation was detected in unaffected individual with positive family history
.
Conclusion: Our results verify the GJB2 mutations to be causative for
NSHL and confirm previous reports on the mutation distribution. Still,
the cause of hearing loss remains unclear for patients with no or single
GJB2 mutation . However, GJB2 related diagnosis cannot be excluded
until mutations in non-coding regions and adjacent GJB6 gene have
been screened .
P05.056
Role of CYP B mutations in Primary Open-Angle Glaucoma
P. López-Garrido1,2 , F. Sánchez-Sánchez1,2 , J. Escribano1,2 ;
1Genetics, Castilla-La Mancha University Medical School, Albacete, Spain,
2Cooperative Research Network on Age-Related Ocular Pathology, Visual and
Life Quality, Instituto de Salud Carlos III, Madrid, Spain.
Glaucoma is a complex and genetically heterogeneous disease characterized
by the progressive apoptotic death of retinal ganglion cells .
Primary open-angle glaucoma (POAG) is the most common form of
glaucoma, featured by an adult onset (>40 years), a gonioscopically
open angle, and a reduced outflow facility. Heterozygous mutations in
CYP1B1 gene are presented in the 4-9% POAG patients of different
populations .
Our purpose is to establish the genotype-phenotype relationship in
Spanish POAG patients carrying CYP1B1 mutations . We have analyzed
the enzymatic activity of different CYP1B1 mutations found in
these patients, in transfected HEK-293T cells . The CYP1B1 enzymatic
activity assay was carried out using ethoxyresorufin as a substrate in
a fluorimetric assay.
CYP1B1 mutations found in POAG patients show reduced enzymatic
activity, supporting that loss of function mutations may play a role in
the development of POAG .
P05.057
Analysis of secretion and processing of wild type myocilin and
myocilin-glaucoma mutants co-expressed in cell lines
J. Aroca-Aguilar 1,2 , F. Sánchez-Sánchez 1,2 , F. Martínez-Redondo 1,2 , M. Coca-
Prados 3 , J. Escribano 1,2 ;
1 Área de Genética. Facultad de Medicina /CRIB. UCLM, Albacete, Spain, 2 Cooperative
Research Network on Age-Related Ocular Pathology, Visual and Life
Quality, Instituto de Salud Carlos III, Madrid, Spain, 3 Department of Ophthalmology
and Visual Science, Yale University School of Medicine, 300 George St,
R.8100, New Haven, 06510, CT, United States.
Glaucoma is a leading cause of irreversible blindness worldwide . The
main known risk factor for this disease is an elevated intraocular pressure
(IOP), mainly caused by an increased resistance to aqueous humour
outflow. Heterozygous mutations in the olfactomedin-like domain
of the myocilin gene (MYOC) cause autosomal dominant juvenile-onset
glaucoma, and approximately 4% of all adult-onset primary openangle
glaucoma (POAG) cases . The mechanisms by which these mutations
elevate IOP and cause glaucoma are currently controversial . It
has been described that myocilin undergoes an intracellular endoproteolytic
processing by calpain II, in the middle of the polypeptide chain,
which is reduced by glaucoma-associated MYOC mutations .
To gain insight into the molecular mechanisms by which mutations in
the MYOC gene lead to glaucoma, we have analyzed, by SDS-PAGE
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