2009 Vienna - European Society of Human Genetics

Molecular basis of Mendelian disorders
Pathology, University of utah, Salt Lake City, UT, United States.
Alport syndrome (AS) is a progressive renal disease with cochlear and
ocular involvement that progresses to end stage renal disease (ESRD)
in young adults although milder cases have been described. The majority
of AS cases is X-linked (XLAS) and caused by mutations in the
COL4A5 gene. The COL4A5 contains 51 exons with more than 400
mutations reported throughout the gene. We present here a comprehensive
molecular testing for XLAS using several technologies and an
algorithm that maintains good sensitivity while limiting cost.
For adult onset XLAS, we developed an assay identifying the three
most common adult type XLAS mutations in the US; C1564S, L1649R,
and R1677Q.
For molecular diagnostic testing of individuals with unknown mutations
we developed a DNA sequencing assay to identify point mutations and
small deletions and insertions.
Additionally, a Multiplex-Ligation Probe dependant Amplification assay
(MLPA) and Nimblegen’s Chromosome X Tiling array were evaluated
to detect complete or partial (exonic level) deletions and duplications
in COL4A5.
We developed a public online searchable data base that contains 446
entries from the literature. In this repository, 88% of the mutations are
point mutations and small deletions or duplications and 12% are large
rearrangements (deletions and duplications at the exonic level).
Using different technologies to analyze different types of mutations,
our laboratory has validated a comprehensive test for XLAS that includes
the development of a large mutation data base.
P12.012
screening of COL A in Hellenic families from Greece and
cyprus with X-linked Alport syndrome
P. Demosthenous1 , K. Voskarides1 , E. Dafnis2 , K. Stylianou2 , A. Pierides3 , E.
Alexopoulos4 , E. Liakou4 , P. Giamalis4 , I. Tzanakis5 , E. Georgaki6 , C. Stavrou7 ,
C. Deltas1 ;
1University of Cyprus, Department of Biological Sciences, Nicosia, Cyprus,
2 3 University of Crete, Department of Nephrology, Heraklion, Greece, Ippokrateion
Hospital, Department of Nephrology, Nicosia, Cyprus, 4Aristotle University
of Thesalloniki, Faculty of Medicine, Nephrology Clinic, Thesalloniki, Greece,
5General Hospital of Chania, Department of Nephrology, Chania, Greece,
6Agia Sophia Childrens Hospital, Department of Pediatric Nephrology, Athens,
Greece, 7Royal Artemis Medical Center, Pafos, Cyprus.
Alport syndrome (AS) is a hereditary disease of basement membranes
that manifests clinically as a progressive nephropathy variably associated
with sensorineural deafness and ocular abnormalities. The most
frequent form of AS is the X-linked one (~85%) due to mutations in
COL4A5 gene. To date, more than 400 different mutations have been
identified in the COL4A5 gene, with “private” point mutations being
the most. We detected and studied for the first time in Greece and
Cyprus - clinically and molecularly - 11 families with AS. Patients of
these families showed some of the main characteristic features of Alport
syndrome, including hematuria, proteinuria, chronic renal failure
and hearing problems. In some of these families, characteristic AS biopsy
was available. X-linked AS was inferred in 9 of these families and
COL4A5 mutation screening was undertaken based on either linkage
analysis results or clinical features only. Direct sequencing of the 51
exons of COL4A5 gene was performed by the use of an ABI PRISM
3130 Genetic Analyzer. We identified three novel mutations in three
of the families, E228X, P628L, 3075delT and one known mutation in
two of the families, G624D. Interestingly, the two Greek families carrying
G624D mutation have a common haplotype flanking the COL4A5
gene, suggesting a founder effect. In addition, male patients in these
families have a later manifestation of the disease. Our results will
highly contribute in pre-symptomatic and prenatal diagnosis in these
families and will add to the international effort being made for genotype
- phenotype correlation in X-linked AS.
P12.013
Identification of a ALMS mutation in a spanish patient with
Alström syndrome
T. Piñeiro-Gallego1 , I. Pereiro1 , E. Vallespín2 , C. Ayuso2 , D. Valverde1 ;
1 2 Departamento de Bioquímica, Genética e Inmunología, Vigo, Spain, Servicio
de Genética. Fundación Jiménez-Díaz, Madrid, Spain.
Alström syndrome (AS, MIM #203800) is a rare autosomal recessive
disorder caused by mutations in ALMS1 gene (chromosome 2p13). It
is a multiorganic disorder characterized by cone-rod dystrophy, childhood
obesity, progressive bilateral sensorineural hearing loss, insulin
resistance and type 2 diabetes mellitus. Dilated cardiomyopathy occurs
in more than 62% of patients. Pulmonary involvement and hepatic,
renal and urological dysfunction are frequently observed.
ALMS1 gene consists of 23 exons and encodes a novel protein whose
function still remains unclear. However, the ALMS1 protein is widely
expressed, and localises to basal bodies of ciliated cells and centrosomes
playing a possible role in intracellular trafficking.
We present the case of a girl from a Spanish family. She was referred
with nystagmus, obesity, progressive sensorineural hearing loss and
short stature. The patient also presented benign acanthosis nigricans,
endocrine hypothyroidism and several ophthalmologic findings. Fundus
examination showed numerous pigmentary spicules and a diminished
caliber on the retinal vasculature. She also presented strabismus
and poor visual acuity. Electroretinogram (ERG) and visual evoked potencials
(VEP) showed no response.
The identification of the mutation was performed amplifying the exons
10 and 16 by PCR, which was followed by direct DNA sequencing.
The patient showed a homozygous deletion in exon 16, c.10790_
10791delTG that causes a premature termination codon at amino
acid 3600 (p.V3597fsX3600) of ALMS1 and truncation of the protein.
In conclusion, one mutation in the ALMS1 gene causative for AS has
been reported, proving that mutational screening is a useful tool in the
molecular diagnostic of AS.
P12.014
Early-onset Alzheimer’s disease due to novel mutation in PSEN
gene? - case report
S. Walczysková 1 , V. Engelmannová 2 , E. Šilhánová 1 ;
1 Faculty Hospital of Ostrava, Department of Medical Genetics, Ostrava, Czech
Republic, 2 University of Ostrava, Faculty of Health Studies, Ostrava, Czech
Republic.
Patients with an inherited form of Alzheimer’s disease (AD) carry
mutations in the presenilin genes (PSEN1, PSEN2) or the amyloid
precursor protein gene (APP). These disease-linked mutations result
in increased production of the longer form of amyloid-beta, the main
component of amyloid deposits found in brains of AD patients. Presenilins
are postulated to regulate APP-processing through their effects
on gamma-secretase, the APP-cleaving enzyme.
We present a 67-year-old woman with family history of dementia, who
developed AD in her forties.
DNA was isolated from peripheral blood leukocytes. Intronic primers
were used to amplify and to sequence exons 3-12 of the PSEN1,
PSEN2 genes and exons 16, 17 of the APP gene. APOE status was
determined. Blood samples of family members were not available for
testing, therefore co-segregation of the novel mutation and phenotype
in the affected family was not performed. 100 elderly healthy subjects
(aged>65) were tested for p.P69A substitution using PCR-ARMS.
Using sequencing analysis we found a novel mutation (p.P69A) in exon
5 of the PSEN2 gene. This mutation is not found in AD&FTDM Database,
2009. No p.P69A mutation was found in the healthy subjects.
The absence of the p.P69A mutation in 100 healthy subjects suggests
that the mutation is not a ,,silent“ polymorphism. The pathologic consequences
are uncertain and needs further investigation.
In conclusion, we present a 67-year-old woman, who developed AD in
her forties. We found a novel mutation (p.P69A) in the PSEN2 gene,
these was not found in the control group. The pathologic consequences
needs further investigation.
P12.015
Molecular genetical findings of familial Alzheimer´s disease and
familial frontotemporal lobar degeneration in a patient cohort in
Portugal - description of five novel mutations
G. Miltenberger-Miltenyi1 , S. I. Pereira2 ;
1 2 Institute of Molecular Medicine, Lisbon, Portugal, GenoMed Diagnostics of
Molecular Medicine, Lisbon, Portugal.
We studied 127 unrelated patients (aged 64±10 years) with Alzheimer’s
disease (AD) and frontotemporal lobar degeneration (FTLD) for
mutations in the amyloid precursor protein gene (APP), presenilin 1
gene (PSEN1), presenilin 2 gene (PSEN2), microtubule associated
protein tau gene (MAPT) and progranulin (PGRN) genes. Until now
only 44 mutations in MAPT and 64 in PGRN have been described. To