Transcript Genetic Testing

IN THE NAME OF ALLAH
THE MOST
BENEFICAL THE MOST
MERCIFUL
ASPM GENE ANALYSIS IN
PAKISTANI FAMILIES WITH
PRIMARY MICROCEPHALY MAPPED
TO MCPH5 LOCUS
By
Shamim Saleha
PhD Scholar
DEPARTMENT OF BIOTECHNOLOGY AND GENETIC ENGINEERING,
KUST
GENETIC DISEASES:
“A genetic disease is due to a faulty gene or group of genes. It
occurs when recessive and/or dominant genes are passed down
to the baby from generation to generation.”
(Genetic Diseases Forum)
• Genetic diseases are :
…
…
…
…
Congenital
Serious
Incurable
Treatable
• Paramount importance
… Family history
… Genetic counseling
• Currently about 6,000 genetic disorders known
(Wade and Nicholas, 2006)
NEUROLOGICAL INHERITED DISORDERS:
• Large group of clinically heterogeneous diseases.
(Klein, 2006)
• Over 15 Neurological disorders are known to have a genetic
cause.
(NINDS, 2009)
• Neurological disorders affect
…
…
…
…
Brain
Spinal cord
Muscles
Nerves
• Rare and poorly understood
(Hazama et al., 2009)
(NINDS, 2009 )
HUMAN INHERITED DISEASES:
• Monogenic disorders
…
…
…
…
…
disease of autosomal dominant, AD
disease of autosomal recessive, AR
disease of X-linked dominant inheritance, XD
disease of X-linked recessive inheritance, XR
disease of Y-linked inheritance
• Polygenic diseases
• Chromosomal diseases
• Somatic inherited diseases
(Valente et al., 2008)
AUTOSOMAL RECESSIVE DISEASES:
• Among genetic disorders, that are strongly associated with
consanguinity, are inherited only in autosomal recessive
manner.
(Hamamy et al., 2007)
• AR diseases may emerge worldwide in a population as the
prevalence of a deleterious gene or
when degree of
consanguinity increases.
(Campbell et al., 2009)
• In case of autosomal recessive inheritance, both parents and
two thirds of surviving offspring are mark as carriers .
(Roberts et al. 2002)
CONSANGUINITY IN WORLD:
• Only 1% :
… Western Europe
… North America
… Australasia
… Russia
• 1% to 10% :
… Iberian Peninsula
… Japan
… South America
• 20% to 50% :
… North and sub-Saharan Africa
… West, Central and South Asia
(Bittles, 2008)
CONSANGUINITY IN PAKISTAN:
• In Pakistan, approximately
…
60% of marriages are consanguineous
(Bittles, 2008)
• Daily Times reported
…
…
…
…
82.5% parents are first cousins
6.8% are blood relatives
6.3% belong to a same caste and family
only 4.4% are married out of their families.
(Khan et al.,2008)
• Practice of Consanguineous marriages
…
…
…
…
Economic
safety reasons
Ethnic groups
Religion
(Campbell et al., 2009)
GENETIC DISORDERS IN KHYBER
PAKHTOON KHWA:
• Factors that contribute to the wide prevalence of genetic
disorders, in this region, are:
… High rate of consanguinity
… Social trend to have more children until menopause
… Practice of autogamy in Pathans
… Lack of public awareness towards the early
recognition and prevention of inherited disease.
… People do not agree with medical explanations of a
genetic mode of disease inheritance
(Daily Times ,2008)
OBJECTIVES:
• To trace genetic illnesses in those affected families that posses
a pedigree records of Microcephaly
• To determine phenotypes by clinical
assessments and
genotype/phenotype correlation by genetic analysis.
• To identify and map diseased loci by genetic linkage studies.
• To find the genetic complexity or heterogeneity of
Microcephaly by mutation screening of diseased genes.
MATERIALS & METHODS:
•
•
•
•
Pedigree collection and Analysis
Blood Sampling
Human Genomic DNA Extraction
Linkage Studies by STR markers
(http://www.uia.ac.be/dnalab/hhh/)
… Amplification of DNA by polymerase chain reaction (PCR)
… Polyacrylamide gel electrophoresis
• Direct DNA sequencing
MICROCEPHALY:
MICROCEPHALY:
CLINICAL HETEROGENEITY OF
MICROCEPHALY:
• Autosomal recessive primary
microcephaly (MCPH) is disorder of
neurodevelopment.
• Individuals with MCPH phenotype
… reduced brain weight
… reduced head circumference of at least 4
SD at birth
… non progressive mental retardation of
variable degree
(Woods et al.,2005)
PREVALENCE OF MICROCEPHALY:
• More common in consanguineous populations
(Nicholas et al.,2008; Kousar et al.,2009)
• Incidence
… 1 in 10,000 in Pakistan
… 1 in 1,000,000 in Caucasian
… 1 in 30,000 in Japan
… 1 in 250,000 in Holland
… 1 in 2,000,000 in Scotland
(Nicholas et al.,2008)
(Woods et al.,2005)
(Komai et al.,1955)
(Van den Bosch,1959)
(Tomie etal.,1987)
LINKAGE STUDIES:
Disease was mapped at
MCPH5 locus, the gene in
this region, is ASPM
ASPM PEDIGREE WITH GENOTYPING DATA:
PRIMERS SEQUENCES OF ASPM:
MUTATION SCREENING:
• Common mutation in
both families
• 200 control was not
observed
• Mutation changes
nucleotide at position 5684,
results in a substitution of
lysine with arginine at
position 1985 of protein.
OUTCOMES:
• The mapping of large number of families to MCPH5
locus and identification of common mutation in
ASPM gene in families of Pakistani origin will enable
us to formulate future strategies to control and
prevent the disease to reduce the prevalence of
MCPH in Pakistan.
 genetic counseling
 prenatal diagnosis
 postnatal diagnosis
 carrier testing
Any Question
Thanks