GENETIC
HETEROGENEITY OF THE B-GLOBIN GENE IN PESHAWAR KHYBER PAKHTUNKHWA PAKISTAN: A
PILOT STUDY
By
Muhammad Adil (M.Phil.
Scholar, Department of Biochemistry, UCSS, AWKUM)
Thalassemia
is an inherited condition affecting the blood. Thalassemia is one of the major
health problems worldwide. It is an autosomal recessive blood disorder, caused
by DNA mutations that affect the synthesis of the globin protein. Hemoglobin in
red blood cells serves the purpose of oxygen and carbon dioxide transport to
all parts of the body. The patient who has thalassemia is not able to make
enough hemoglobin and become anemic. Deficiency of hemoglobin results in
reduced supply of oxygen to organs and become starved for oxygen and unable to
perform normal body functions. Thalassemia is mainly grouped in two types;
Alpha (α) thalassemia and Beta (β) thalassemia. Extensive research in this
field have identified more the more than 200 different mutations on the α and β
globin genes. Geographically these mutations are categorized based on ethnicity
and racial origin. Thalassemia commonly found in malarial, tropic and
sub-tropic region of Mediterranean countries, the Middle East, Transcaucasia,
central Asian, the South and South east Asian countries.
Thalassemia is genetic disorder and is transmitted
from parents to their offspring’s. If both parents are thalassemia carrier then
there is 25% chance in each pregnancy that the child will inherit thalassemia,
50% chance that the child will be heterozygous for thalassemia and 25% percent
chance that the child will be normal. If one of the parent is thalassemia
carrier and one parent is normal having the capability to produce normal
hemoglobin then there is no chance of thalassemia in offspring but 50% chance
of normal pregnancies and 50% percent chance of pregnancies producing carrier
children. In thalassemia patients becomes anemic due to the decreased
production of hemoglobin by red blood cells. Other symptoms include pale skin,
weakness, Fatigue, splenomegaly, jaundice and sometimes bones deformation. This
abnormal hemoglobin although carries oxygen to all parts of the body, but are
not able to release oxygen easily therefore the organs become starved for
oxygen and the individual become anemic.
Pakistan
being an under developed country and having close
social and cultural values and continuous consanguineous marriages are
constantly at high risk of genetic disorders.
Consanguineous marriages account around 40% of thalassemia in Pakistan.
Approximately 9.8 million carriers are estimated in total population of
Pakistan with a carrier rate of 5–7%. In Pakistan forty thousand children are
effect from thalassemia and about 5-9 thousands are added annually in a total
of 200 million populations. The main causes of thalassemia in Pakistan are
consanguineous marriages, high fertility rate, high birth rate, illiteracy,
childhood marriages and lack of awareness about genetic disorders. In Pakistan
thalassemia is most commonly prevailed in tribal belt and Khyber Pakhtunkhwa,
but their concentration is also high in rural areas of Baluchistan, Sindh and
Punjab provinces. In Pakistan as compared to a-thalassemia, β thalassemia is
the most common disorder showing a wide range of heterogeneity.
In
this case study, β-thalassemia patients’ blood samples were analyzed to find
out the frequency of mutations in the population of the district Peshawar,
Khyber Pakhtunkhwa. Amplification Refractory Mutation System (ARMS) based PCR
were performed for known mutations from blood samples to investigate the
prevalence of β-thalassemia mutations. The present study focused on these six
common mutations and ARMS-PCR analysis was performed. Moreover, five mutations
FSC-8/9 (+G), IVS-1-1 (G-T), IVS-1-5 (G-C), CD 41/42 (-TTCT), and CD15 (G-A)
have been be detected in the district Peshawar region. The prevalence of each
mutation in district Peshawar is summarized in table 1.
Table 1:
Homozygous mutant allele frequency of different β-thalassemia mutation in
district Peshawar
Serial No.
|
Mutation
|
Homozygous
|
Percentage
|
1
|
FSC
8/9, (+G)
|
10
|
43.5%
|
2
|
IVS-I-5,
(G-C)
|
9
|
39.2%
|
3
|
CD
41/42, (-TTCT)
|
2
|
8.7%
|
4
|
IVS-I-1,
(G-T)
|
1
|
4.3%
|
5
|
CD-15,
(G-A)
|
1
|
4.3%
|
6
|
FSC-5,
(-CT)
|
0
|
0.0%
|
To educate people about genetic disorders, Genetic counselors
require to organize regular public seminars, workshops to highlight the
significance of genetic testing and carrier screening. A pediatric genetic
counselor is responsible for counseling the families’ having genetic disorders.
The information provided by genetic counselor is aimed to help the affected
families in making decisions, which helps in controlling genetic disorders.
These decisions include various options such as birth control, mate selection
and pre-natal testing. Prenatal screening is mainly concern to control and
prevent the birth of new babies having risk of thalassemia major. This approach
requires carrier screening of the parents with increased risk of thalassemia.
As we are all aware of the fact that genetic disorders cannot be cured, earlier
patients with β-thalassemia major were treated only with continuous blood
transfusions. Nowadays, beside blood transfusions iron chelating therapy is
combined to reduce iron load. Bone marrow transplantation is available but it’s
very expensive and to find a suitable donor is also very challenging. Some
medicines such as Hydroxyurea have also shown promising results on transfusion
dependent β-thalassemia patients.
To significantly control the rate of
thalassemia by comprehensive programs like public
awareness, genetic counseling, carrier screening, pre-natal diagnosis, controlling
the birth rate from the thalassemia affected or thalassemia carrier’s parents.
To completely eradicated thalassemia it is highly recommended to adopting
genetic screening certificate a pre-requisite before marriage and careful
screening of pregnancies at risk are monitored.
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