gene therapy Flashcards
(55 cards)
what is gene therapy
delivery of genentic material into a patients cells as a drug to treat diseases associated with genetic mutation/changes in gene expression
how can a gene mutation lead to disease (4)
- mutation in the promotor: increase or decrease in mRNA
- mutation in coding sequence: creation of different protein but this may be harmless
- mutation in splice site: production of incorrectly spliced mRNA (removal of introns)
- mutation in regulatory element: increase or decrease in protein production
what is the effetc of a mutation in coding sequence (exon)
can result in a different amino acid being incormpeated into the protein sequence leading to the formation of a mutant protein. This can be harmful or harmless
give an example of a disease where there is a mutation in the coding sequence and the resulting phenotype
sickle cell. there is a mutation in both copies of the beta-globin gene. It is autosomal recessive . Hemoglobin S forms instead of haemoglobin A - s is cresent shaped - impared transportation of oxygen. mutation is GAG to GTG - leads to glutamic acid instead of valine at position 6 in protein
define autosomal recessive
both parents need to be carrying the gene and pass it onto the child
what is a frameshift mutation
where deletion of substitution occurs in multiples of 3 (codon)
what is a nonsense mutation and what is the result
premature termination codon = truncated protein
what is the effect of a mutation in the promotor region
this leads to changes in gene expression. The binding of the transcripton factor will be varied due to a different site. It will be recognised differently. This will effect gene expressn
what is the effect of a mutation in the control element
This is where a mutation leads to changes in the regulation of expression by splicing trans-acting factors (Regulatory proteins that control gene expression).
what are trans acting factors
Regulatory proteins that control gene expression. They bind to DNA to influence transcription of genes
whta must gene therapy be able to do
target the correct cells, act for long enough whilst not compromising cell funtion
what is the therpy Glybera used for
treats rare metabolic diseases that causes pancreatitis, LPLD (
Lipoprotein lipase deficiency)
works via the delivery of the LPL gene
what are some of the challanges of glybera
delivery to correct target cell, maintenence of delivered gene in target cell, high cost of drug development.
it is only suitable for diseases that are caused by reduced production of a protein product. We therefore cant achieve a precise level of expression of a delivered gene so it is only useful if the level of expression does not matter
describe ex vivo gene delivery
take the target cells out of the patient. introduce the gene and then return them to the patient. allows precose targeting and increased efficiency
describe in vivi gene delivery
Introduce the gene directly into the patient into the target tissue. eg aerosol delivery if target is lungs
describe the differences in viral vs non viral delivery
viral delivery leads to more effieicnt uptake than non viral. There is higher selectivity for specific cell types and the effect can persist in cells for much longer. However there is higher risk of immune response, and there is a limit on the size of the gene that can be incorporated compared to non-viral
why may viral delivery be used
target and attach to specific cells
transport genetic material directly to nucleus and maintenance as DNA
Sustained expression of genetic material over time
what type of viruses are used for viral delivery
adeno-associated virus, DNA virus, lentiviruses, retroviruses
what are lentuviruses
A type of retrovirus. these are highly modified viruses such as HIV, They allow incorpration of a delivered gene into the host genome and therefore genetic expression is maintained during cellular activity. They can integrate into both dividing and non-dividing cells
what is AAV (viral delivery)
non-pathogeic, low immunogenicist. they cna infect dividing and non-dividing cells. They cannot replicate without the use of helper viruses. They are very small so the size of the gene is limited
what is CAR-T immunotherapy
form of adoptive cell transfer. T cells are taken from a patient and genome is engineered to produce chimeric antigen receptors - recognise antigens on cancer cells. return these cells to patients and allow then to multiply and kill cancer cells.
what are some of the key issues associated with CAR-T therapy
- cytokine storm can occur
- solid tumour - harder to target
describe how gene therpy has been used for heamophillia
- blood clotting disorder caused by lack of clotting factors. x linked recessive inheritance
- Gene therapy for hemophilia involves delivering a functional F8 or F9 gene to hepatocytes using adeno-associated virus (AAV) vectors. This single infusion enables endogenous production of factor VIII (FVIII) or FIX protein, reducing bleeding in patients.
what is genome editing
modification of genomic DNA
