ISSN 10227954, Russian Journal of Genetics, 2013, Vol. 49, No. 9, pp. 982–983. © Pleiades Publishing, Inc., 2013.
Published in Russian in Genetika, 2013, Vol. 49, No. 9, pp. 1126–1128.
982
1
INTRODUCTION
Spinal muscular atrophy (SMA) is caused by the
degeneration of
α
motor neurons of the spinal cord
anterior horns, leading to progressive atrophy of prox
imal muscles, paralysis, respiratory failure, and infant
death. With an incidence of 1/6000 to 1/10000 and a
carrier frequency of 1/25 to 1/50 in different popula
tions, SMA is the secondmostfrequent autosomal
recessive disease in Europe [1, 2]. The SMAdeter
mining gene is called the “survival motor neuron”
gene (
SMN
) and it is located on chromosomal region
5q13.
SMN1
gene is presented in two functional cop
ies,
SMN1
and
SMN2
, which differ by only five nucle
otide exchanges [3, 4]. The vast majority of patients
with SMA (85–98%) carry a deletion of the exon 7 of
SMN1
[3]. As the
SMN1
and
SMN2
exons differ by
two transitions, a standard PCR combined with the
restriction fragment length polymorphism technique
are widely used in the diagnostics of SMA [5, 6]. How
ever, this approach does not allow the detection of
SMN1
gene in heterozygous carriers. In our previous
study we have developed an easy and reliable analysis
of deletion in exon 7
SMN1
gene based on SYBR
Green RealTime qPCR [7]. To ascertain the feasibil
ity of population screening for spinal muscular atro
phy, here we have used this technique and established
the incidence of heterozygous carries of the exon 7
SMN1
deletion in Ukrainian population.
MATERIALS AND METHODS
Blood samples were collected at the ISIDA clinic
(www.isida.ua) from 370 unrelated female patients
1
The article was translated by the authors.
with no family history of SMA. The participants were
involved in the voluntary programs of genetic testing
and information consent was obtained from all of them.
Blood samples were also ollected from 10 spouses of the
heterozygous carriers of the exon 7
SMN1
deletion.
DNA was purified from frozen blood using phenol
chloroform extraction [8]. DNA concentration was
measured using ND1000 spectrophotometer (Nano
Drop, USA). The copy number analysis of exon 7
SMN1
gene was performed using the SYBR Green
RealTime qPCR assay specific for the single nucle
otide change in exon 7 (c.840 C>T) as previously
described [7]. The relative gene copy number (
2
–
ΔΔ
Ct
ratio) of samples was estimated using a
2
–
ΔΔ
Ct
method
(the Livak method) [9]. According to the previously
obtained results of the assay validation, the normalized
copy number range for the heterozygous mutation
carrier (1 copy) was considered as
0.475 ± 0.091
and
for the normal (2 copies) DNA sample
0.909 ± 0.068
.
RESULTS AND DISCUSSION
We have screened 370 individuals from the general
population in Ukraine. Twelve heterozygous carriers
of the exon 7
SMN1
gene deletion were identified. The
frequency of SMA carriers estimated in this study is 1
in 31 individuals (3.24%). A comparison of our data
with those obtained on other ethnical groups is shown
in table.
The African American and Hispanic groups from
USA have significantly lower frequency among the
populations presented in the table. The highest fre
quency of exon 7
SMN1
gene heterozygous deletion
was observed in the Iranian population, which could
be attributed to the high consanguinity rate in this
Spinal Muscular Atrophy Carrier Frequency in Ukraine
1
O. Soloviov, N. Hryschenko, and L. Livshits
Department of Human Genomics, Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine,
Kiev, 03680 Ukraine
email: livshits@imbg.org.ua
Received January 31, 2013
Abstract
—Background. Spinal muscular atrophy (SMA) is a common autosomal recessive neuromuscular
disorder with the frequency of carriers in a number of ethnical groups ranging from 1/50 to 1/25. However,
the prevalence of SMA for population of Ukraine remains to be established. Methods. For the analysis of
deletion in exon 7
SMN1
gene in SYBR Green RealTime qPCR assay specific for the single nucleotide
change in exon 7 (c.840 C>T) was used. Results. Using SYBR Green qPCR assay, the incidence of the exon
7
SMN1
deletion was established among 370 unrelated individuals without family history of SMA. The carrier
frequency for this group of Ukrainians was estimated as 3.24% (1/31). Conclusions. The results of our study
showing the high prevalence of carriers warrant the importance of population screening for SMA in Ukraine.
DOI: 10.1134/S1022795413080140
SHORT COMMUNICATIONS
@Phil_Robichaud
@deepthiw
@JoseServera