2008 Barcelona - European Society of Human Genetics

Cytogenetics
P01.369
three novel mutations in FRmD7 in X-linked congenital motor
nystagmus in Russian families
S. Gudzenko1 , V. Fedotov2 , R. Zinchenko1 , A. Polyakov1 ;
1 2 Research Centre for Medical Genetics, Moscow, Russian Federation, Regional
Clinical Diagnostic Centre, Voronezh, Russian Federation.
X-linked congenital motor nystagmus is a common inherited oculomotor
disorder characterized by repetitive uncontrollable ocular oscillations,
unassociated with a number of ocular or neurological diseases with
onset typically at birth . The loci for X-linked CMN have been mapped
to Xp11 .3-p11 .4 and Xq26-q27 (NYS1) . Three more loci have been
described for autosomal-recessive and autosomal-dominant form of
CMN without any gene identification. The molecular characterization
of NYS1 has been solved by Tarpey et al., who identified mutations in
FRMD7, a gene with unknown function .
The aim of our research was searching for FRMD7 mutations in three
Russian families with X-linked CMN, who had already shown the linkage
with Xq26-q27 locus . Sequencing analysis of all exons and intronexon
junctions of FRMD7 was performed in affected males from these
families. We identified three novel, previously unreported mutations in
FRMD7: missense mutation c . 47T>C (Phe16Ser), nonsense mutation
c . 1524G>A (Trp508Stop) and small deletion c . 1492delT . Thus the
results of our study confirm the role of FRMD7 in the pathogenesis of
X-linked CMN .
P01.370
Diagnostic and prognostic implications of nuclear and
mitochondrial mutations in couples opting for ARt
R. Dada, R. Kumar, M. B. Shamsi, S. Venkatesh;
Laboratory for Molecular Reproduction and Genetics, Dept. of Anatomy, AIl
India Institute of Medical Sciences, New Delhi, India.
Microdeletion on the long arm of the Y chromosome and mutations
in mitochondrial genes regulating oxidative phosphorylation may severely
impair spermatogenesis Thus it was planned to analyze cases
(n = 580) with idiopathic male infertility opted for ART by cytogenetic,
Yq microdeletion and mitochondrial mutation analysis .
In cytogenetically normal cases microdeletion analysis was done using
EAA guidelines. Mitochondrial genome was amplified and sequenced
using a set of 24 primers in 33 OAT cases . The mutations were compared
in blood and sperm DNA . 8 .2% and 10 .1% cases harboured
Yq microdeletion in blood and semen respectively . Results of mitochondrial
mutation analysis showed G to A transition in ND4 gene at
nucleotide position 11719 in sperm DNA of 19 cases and only in 14
cases from blood DNA . Though this is a non-synonymous change, the
amino acid remains the same . The polymorphism A750G, A4769G and
A8860G was found in all the semen as well blood DNA of the cases but
only in 12 controls . A750G, A4769G are non-synonymous changes but
A8860G polymorphism in ATPase 6 gene changes amino acid threonine
to alanine .
As majority of these infertile couples opt for ART/ICSI, it is very important
to distinguish cases with Yq microdeletions and mitochondrial
mutations as former are iatrogenically transmitted to the offspring
through these techniques . Thus a thorough genetic analysis is a must
in all infertile couples to provide comprehensive counseling and most
adapted therapeutics .
P02. Cytogenetics
P02.001
screening for subtelomeric aberrations using multiplex ligation
dependent probe amplification (MLPA)
D. Gomez, M. Fernandez, L. Aparicio, F. Cuevillas, H. Vidiella, E. Cusó, J. V.
Martinez, C. Mordillo;
Balagué Center S.A., Hospitalet de Llobregat, Spain.
Subtelomeric rearrangements are believed to be a common cause of
mental retardation. New molecular techniques allow their identification,
their frequency and significance are still unknown.
METHODS: We screened 30 patients with idiopathic mental retardation
and/or phenotypic malformations making use of the multiplex ligation-dependent
probe amplification (MLPA, SALSA kits P036D and
P070) . The parents of those patients with subtelomeric aberrations
were also tested for the origin (see table 1) . All rearrangements were
confirmed by FISH or by the SALSA MLPA KIT P096-MR2.
RESULTS: We identified a total of 7 subtelomeric aberrations (23,3%).
Four were deletions, two were duplications and one case showed one
deletion and one duplication (See table 1) .
Table 1 .
Case MLPA aberration Confirmation Origin
1 del 4p
+ Wolf-Hirschhorn with P096 KIT
- FISH with WHSC1 probe
de novo
2 del 20p FISH in process unknown
3 del 4p
+ Wolf-Hirschhorn with P096 KIT
+ FISH with WHSC1 probe
de novo
4 del 1p + FISH 1p36 de novo
5 dup Xq/Yq FISH in process unknown
6
del Xq/Yq, dup
Xp/Yp
46,X, der(Y)
FISH in process
de novo
7 dup Xp/Yp MLPA positive in mother and
brother
maternal
CONCLUSIONS: The high frequency of subtelomeric aberrations detected confirmed
the important role played by these rearrangements in the aetiology of Mental retardation.
De novo aberrations are likely related to the clinical presentation
of the patient while inherited aberrations probably are not the cause
of the patient phenotype . MLPA has demonstrated to be a very useful
method that can be offered to all mentally retarded patients in order to
approach to genetic diagnosis .
P02.002
Unusual 17p subtelomeric micro-duplication
S. Garcia-Minaur 1 , C. Serra 1,2 , I. Cusco 2 , A. Plaja 1 , L. Pérez Jurado 1,2 ;
1 Programa de Medicina Molecular y Genetica, Hospital Vall d´Hebron, Barcelona,
Spain, 2 Unidad de Genetica, Universidad Pompeu Fabra, U-735 CIBERER,
Barcelona, Spain.
We report a 5 ½ year-old girl with developmental delay, microcephaly,
cardiomyopathy and distinctive facial features . Additional brain MRI
findings include a hypoplastic corpus callosum and enlarged cisterna
magna . Standard karyotype was normal . MLPA assay with commercial
probe kits to detect subtelomeric rearrangements identified a de novo
17p micro-duplication . Microarray analysis with a custom made chip,
which contains 1905 BAC clones covering subtelomeric and pericentromeric
regions of each chromosome and regions related to known
syndromes, confirmed the presence of a duplication of > 6.2 Mb confined
to 17p13. Interestingly, the duplicated fragment is not continuous
but interrupted by a 0 .45-1 .1 Mb segment that is not duplicated,
suggesting a more complex rearrangement, possibly mediated by a
balanced rearrangement in one of the parents . Although partial 17p
trisomy has been found in association with other rearrangements, to
our knowledge only one other case has been reported with a 17p13
duplication exclusively and clinical features overlapping those of our
patient . Further studies on this child and her parents are currently under
way and the results will be presented .
P02.003
subtelomeric study of 109 patients with developmental delay,
dysmorphy and/or congenital anomalies of unexplained etiology
- case presentations
M. Krajewska-Walasek, A. Gutkowska, A. Marczak, M. Gajdulewicz, K. Spodar,
A. Jezela-Stanek, M. Kugaudo, M. Bialecka, K. Chrzanowska, E. Popowska;
The Children’s Memorial Health Institute, Warsaw, Poland.
Background: Subtelomeric chromosome aberrations are acknowledged
as one of the significant causes of mental retardation (MR).
Their prevalence is about 5 .2%, ranging from 0 to 16% (depending
on the preselection criteria and the expertise of the examining clinician)
. Because of either their small size and/or similarity of involved
segments, these aberrations are undetectable by conventional binding
techniques . Hence, they can be screened for by other methods, most
frequently by FISH with a complete set of subtelomeric probes or by
multiplex ligation-dependent probe amplification (MLPA). We report
the diagnostic yield in a series of 109 patients with an unexplained
combination of mental retardation with dysmorphy and/or congenital
anomalies .
Methods: Patients were evaluated for subtelomeric rearrangements
using commercially available total subtelomeric FISH (TS) . All had
normal results of GTG-banded chromosomes at the 550-band level
and were referred for TS based on clinical indications suggestive for
0