Human Genome Project
Potential Applications
In March, 2002
Doctors successfully screened embryos for gene mutation linked to early onset Alzheimer's
JAMA, March, 2002
Basics
Inside the nucleus of every cell in the body, a complex set of genetic instructions, known as the human genome, contained on pairs of chromosomes.
Gene
A gene is a chromosomal region capable of making a functional transcript.
However
Many genes are co-expressed with their own antagonist
Thus
A genome is all the DNA in the cell, including its genes.
Errors in genes--the smallest units of heredity-- may cause or contribute to disease
The result
All diseases have a genetic component, whether inherited or resulting from the body's response to environmental stresses like viruses or toxins
Genomics
Structural genomics: to identify all the approximate 30,000 genes in human DNA
Functional genomics: to understand gene-gene interaction
Objectives
store this information in databases
Build up a genomic library
Once needed , investigators can simply go to the freezer where DNA for the physical map is stored and pick out the piece that contains the gene.
The most important question
How & Which
genes play a role in disease causation
Tools
An increasing number of gene tests are becoming available commercially
Micro-array composed of five separate array each of which has about 10,000 target
Genomic Medicine
Diagnosis
Monitoring of progress
treatment of disease
Prevention
Example
hereditary nonpolyposis colon cancer was linked to a gene located on chromosome 2.
But
The road from gene identification to effective treatments is long and full of challenges
So Why?!!!
We as Doctors must be aware about the new genetic era and its potential impacts on our specialty so as to offer our patients the most appropriate and informed care.
Implantation : the model
Repeated failure of implantation was linked to Leukemia inhibitory Factor gene (LIF)
Implantation
Micro-array analysis has shown 36 up-regulated genes and 27 down-regulated genes at the implantation site.
Reese J et al, 2001
Categorised in
genes with recognized roles in implantation,
genes with potential roles in this process
genes whose functions have yet to be defined in this event
polycystic ovary syndrome
the insulin gene called variable number tandem repeat (VNTR) gene appears to be a promising candidate
polycystic ovary syndrome
follistatin gene as a potential disease locus implicated in ovarian follicular development
polycystic ovary syndrome
CYP11a gene -encoding P450 side chain cleavage-appears to be a major susceptibility locus for steroidogenic abnormalities
Franks et al, 2001
MUC 1: a genetic link to infertility?
Women with unexplained infertility were found to have a genetic susceptibility to failure of embryo implantation due to small MUC 1 allele size.
Horne A, et al,2001
Inherited breast and ovarian cancer (BRCA 1 and 2; early-onset tumors of breasts and ovaries)
Pre-eclampsia
A polymorphism in the gene for microsomal epoxide hydrolase is associated with pre-eclampsia
Zusterzeel et al 2001
Women with the glutathione S-transferase P1b-1b genotype, which could result in lower glutathione S-transferase detoxification capacity, has been linked to higher susceptibility to preeclampsia
Zusterzeel 2000
Gynecological oncology
The increased ovarian cancer risk associated with the high-activity of human EPHX gene (epoxide hydrolase)
cystic fibrosis
three hundred affected children born each year in UK
with improvements in care and treatment, people with
cystic fibrosis can now live for up to twenty-five years,
there is no cure
PGD
Currently Available DNA-Based Gene Tests
Alpha-1-antitrypsin deficiency
myotrophic lateral sclerosis
Alzheimer's disease
Cystic fibrosis
Myotonic dystrophy
Neurofibromatosis type 1
Thalassemias
Ataxia telangiectasia
Gaucher disease
Hereditary nonpolyposis colon cancer
Charcot-Marie-Tooth
Congenital adrenal hyperplasia
Duchenne muscular dystrophy/Becker muscular dystrophy Fanconi anemia Factor V-Leiden Fragile X syndrome Hemophilia A and B Huntington's disease
Phenylketonuria
Adult Polycystic Kidney Disease
Prader Willi/Angelman syndromes
Sickle cell disease
Spinocerebellar ataxia
Spinal muscular atrophy
Tay-Sachs Disease
Gene therapy
It means modification of the genetic material of living cells
This applies to genetically determined diseases but may also expanded to diseases that occur later in life
Highly promising
Treatment
Prevention
Immunity enhancing (e.g., by adding a gene that suppresses tumor growth).
Still experimental
more technological barriers are encountered than foreseen and therefore, the clinical success up to now is limited.
Germ cell gene therapy
Germ cell gene therapy
Deposit corrective genes in the cell’s nucleus,
integrate genes into the chromosomes..
Somatic cell gene therapy
The Concept
Natural ability of viruses to enter cells through receptors
genetically altered to carry normal human DNA.
How it is prepared!!
harmful viral genes are removed and replaced with the corrective gene. (Vector)
Viruses recognize and attach to receptors (a) and work their way through, into the cell (b). Once inside, the virus discharges its contents (c). Viral genes progress through the cell and into the nucleus (d).
How to select
Depending on the specific virus, these genes may or may not integrate into the host's chromosomes.
Specific Target
Each virus is particularly adapted to use one or a few specific receptors, which limits the range of cells each one can infect.
How
Cells may be modified ex vivo for subsequent administration to patients, or may be altered in vivo by gene therapy given directly to the subject.
Familial HypercholesterolemiaA retroviral vector delivers a corrective low-density lipoprotein (LDL) receptor gene. A piece of the patient's
liver is removed, and the cells are treated with a retrovirus carrying a good copy of the gene.
Liver cells incorporating the corrective gene are implanted into the patient's liver.
It is the future
Currently, within the context of clinical trials, (FDA) has not yet approved any human gene therapy product for sale.
gene therapy for single-gene diseases will be routine and successful within years.
Role in oncology
• It has been proven that many cancers are caused by the mutation of certain genes or lack of gene function
• The introduction of those genes into cancer cells where gene function is compromised, can work to restore gene function and stop tumor progression
May be in the future
Patients with cancer may receive combination chemotherapy together with gene therapy for six cycles of treatment
Ozols 2002
Gene Therapy: Simple in Theory but Difficult in Practice
Obstacles
Safety
Short-lived nature of gene therapy
Multigene disorders
Costs
Ethics : Baby designers
Safety In a gene therapy trial for ornithine transcarboxylase deficiency (OTCD). An 18 years old boy died from multiple organ failures after starting the treatment. (? severe immune response to the adenovirus carrier)
A child successfully treated by gene therapy for X-linked severe combined immunodeficiency disease (X-SCID), known as "bubble baby syndrome." developed a leukemia-like condition.
Nonviral approach (2003)
involves the creation of an artificial lipid sphere with an aqueous core. This liposome, which carries the therapeutic DNA, is capable of passing the DNA through the target cell's membrane
potential for treating Parkinsonism
Where we stand!!
all of the current approaches to gene therapy seek to
introduce the good gene into the so-called somatic cells
of a child or an adult.
While somatic gene therapy is thought to be
appropriate, germ line gene therapy is not allowed
More Effective Pharmaceuticals
Efforts will shift toward developing a new generation of therapeutics based on genes.
How
doctors will test individual genetic profiles against panels of drugs available for a specific condition and choose the treatment with the greatest potential benefit.
antihypertensives
It is real
All will be manufactured by recombinant DNA technology just as human insulin and growth hormone are today
Stem Cells
Alzheimer’s Disease Parkinson’s Disease Various Leukemias
Hodgkin’s Lymphoma Non-Hodgkin’s Lymphomas
Heart Disease Diabetes
Multiple Sclerosis Huntington’s Disease
Osteoarthritis Coeliac Disease
Crohn’s Disease Lupus Erythematosus
Sickle Cell Anaemia Thalassemia
Blackfan Diamond Anaemia Fanconi Anaemia
Types of Stem Cells
Pluripotent Stem Cells: Can give rise to all different cell types in vitro.
Multipotent Stem Cells: Can give rise to several cell types of a tissue or organ.
Unipotent Stem Cells: consist of a single cell type only.
Sources of Stem Cells
Blastocyst embryos - pluripotent
Foetal tissues - pluripotent or multipotent
Umbilical cord blood - multipotent
Isolation of Embryonic Stem Cells
EmbryonicStem cells
Culture
Inner Cell Mass
BLASTOCYST 5-7 day old embryo
Differentiation of E.S.C.
Using particular treatment regimes, embryonic stem cells can be made to differentiate into many types of cell. This is because they are pluripotent.
EmbryonicStem Cells
Liver Cells Muscle cells Skin cells
Thank you!!