Genetic Testing

RaeAnna Illman, John Hurlburt, Duane Goehring, Kim Silvernale

Gene Therapy

• Gene Therapy is delivering replacement genes to correct the problem at it’s source.

Three Phases of Treatment Evolution

• Treating the gene to cure a disease is still not the norm despite HGP advances

•Replacement of missing proteins with material from donors.

•Obtaining pure proteins using recombinant DNA technology.

•Deliver replacement genes

Gene Therapy

• With recent advances, gene therapy has now moved to the treatment of common diseases.

• Gene therapy began by treating complex, uncommon, and inherited diseases.

3 Models for Gene Therapy:

• In-vivo

•Ex-vivo

•In-situ

Germline and Somatic Therapies

• Germline gene therapy alters the DNA of a gamete or fertilized ovum.

• Somatic gene therapy corrects only the cells that an illness affects.

• Picorray therapy places “artificial” genes on a microchip

Methods of Delivery

• Physical – microinjection, particle bombardment, electroporation.

• Chemical – liposomes which secure genetic cargo and can penetrate plasma membranes.

• Biological- Vectors; remove the virus from its membrane and put in its place corrective genes. (very flexible)

Proteins

• Gene therapy uses proteins that are missing to treat the phenotype

• This has mitigated issues with ADA deficiency and white blood cell problems

• A lasting treatment is the alteration of Progenitor cells which make up one in roughly a billion bone marrow cells.

• Potential problems:• Mutations remain in the genotype• Not a dynamic fix which will last throughout the germline• Although the protein is fixed, the gene remains mutated

Setbacks to Gene Therapy

• The body may reject the foreign or altered genes.• Unused amino acids let off a nitrogen gas which mixed

with hydrogen to form ammonia that goes into the bloodstream and then into the brain.

• Method of Transportation = inject unaffected genes into a dead virus which will replicate multiple times and fill the gaps created by affected genes.

• Gene therapies became difficult to continue after so many failures.

• New laws are passed to keep them from repeating

Canavan Disease

• Because no treatment exists, canavan disease made it a unique case study for gene therapy

• It’s a neurological disease, so brain scans make the progress much easier and safer to track

• Treatment must be constant and timely.

Genetic Testing

• 2 basic steps:

• 1) identifying the condition

• 2) taking action against the mutant genes.

Newborn Screening• Genetic counseling involves pedigrees and

helps in weighing the options of how to conceive

• Testing is not expensive because testing for certain disorders in the metabolism requires a simple blood test

Genetic Counseling

• 2 major reasons:

• 1) prenatal counseling

• 2) a disease in the family.

• It is a “shared deliberation and decision making between the counselor and the client.”

• Confidentiality and “duty to warn” relatives is debated

Great Promise

• There is more of a need now for medical genetics due to the rare orphan diseases.

• The more physicians find out about these diseases, the better chance of new treatments for them.

• Gene therapy progress has been painstakingly slow.

• The delivered genes do not always go where intended.

• New gene defects.

• Ways to correct many of the disease Revealed a complexity to genome structure.

Minor setbacks...

In conclusion...

• Although there are draw backs, gene therapy is working. 

• Patients with muscular dystrophy, cystic fibrosis, and SCID have cells that accepted and expressed therapeutic genes. 

• The challenge is find the right vector to deliver a sustained, targeted, and safe genetic correction.

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[15] Limb Girdle Muscular Dystrophy Type 1A. (2006, December ). Retrieved March 2, 2008, from stompy2.tripod.com/md.html