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!!