Genetic screening & gene therapy


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Genetic screening & gene therapy

  1. 1. GENETIC SCREENING & GENE THERAPY<br />Genetic screening &<br /> Gene therapy<br />Dr. Dinesh T<br />Junior resident,<br />Department of Physiology, <br />JIPMER<br />Dr sclerodinesh<br />
  2. 2. Introduction<br />
  3. 3.
  4. 4. History<br />Technology to detect and treat inborn diseases - 1961. <br />1972 Friedmann and Roblin authored a paper in Science titled "Gene therapy for human genetic disease?“<br />The late 1980's, an international team of scientists began the project to map the human genome.<br />September 14, 1990 - first approved gene therapy case in the United States took place.<br />
  5. 5. 1992 - Doctor Claudio Bordignon, Milan, Italy performed the first procedure of gene therapy using hematopoietic stem cells.<br />1995 DNA testing in forensic cases gains fame in the O.J. Simpson trial.<br /> 2002 - first successful gene therapy treatment for adenosine deaminase-deficiency (SCID)<br />2003 – at University of California, Los Angeles research team inserted genes into the brain using liposome coated in a polymer called polyethylene glycol<br />
  6. 6. 2006 - Preston Nix from the University of Pennsylvania School of Medicine reported on VRX496, a gene-based immunotherapy for the treatment of human immunodeficiency virus (HIV) that uses a lentiviral vector for delivery of an antisense gene against the HIV envelope <br />2007 – Moorfields Eye Hospital and University College London's Institute of Ophthalmology announced the world's first gene therapy trial for inherited retinal disease <br />2008 there were more than 1,200 clinically applicable genetic tests available.<br />
  7. 7. Genetic screening<br />
  8. 8. What is genetic screening?<br />The newest and most sophisticated of the techniques used to test for genetic disorders. <br />One of the fastest moving fields in medical science.<br />A technique to determine the genotype or phenotype of an organism.<br />Determines risk of having or passing on a genetic disorder.<br />
  9. 9. Genetic screening<br />Genetic screening is often used to detect faulty or <br /> abnormal genes in an organism<br />Can detect some genes related to an increasedrisk of cancer<br />Can detect some genes known to cause geneticdisorders<br />
  10. 10. Genetic tests <br /> The analysis of chromosomes (DNA), proteins, and certain metabolites in order to detect heritable disease-related genotypes, mutations, phenotypes, or karyotype for clinical purposes.<br />
  11. 11. Gene tests (also called DNA-based tests), in a broader sense<br />Direct examination of the DNA molecule <br />Biochemical tests for such gene products as enzymes and other proteins<br />Microscopic examination of stained or fluorescent chromosomes<br />
  12. 12. Genetic tests <br />Who can order?<br />What are the samples needed?<br />How to interpret the tests?<br />What are all the risks?<br />Ethical considerations?<br />
  13. 13. Types of screening tests<br /><ul><li> Carrier screening
  14. 14. Prenatal diagnostic testing
  15. 15. Newborn screening
  16. 16. Pre symptomatic testing for predicting adult-onset </li></ul> disorders such as Huntington's disease<br /><ul><li> Pre symptomatic testing for estimating the risk of </li></ul> developing Adult-onset cancers and Alzheimer's disease.<br /><ul><li> Conformational diagnosis of a symptomatic individual
  17. 17. Pre implantation genetic diagnosis
  18. 18. Forensic/ identity testing
  19. 19. Research
  20. 20. Pharmacogenomics </li></li></ul><li>
  21. 21. Genetic screening<br />Adult Polycystic Kidney Disease <br />Alpha-1-antitrypsin deficiency <br />Amyotrophic lateral sclerosis <br />Alzheimer's disease<br />Ataxia telangiectasia<br />Central Core Disease<br />Charcot-Marie-Tooth disease<br />Congenital adrenal hyperplasia <br />Cystic fibrosis <br />Duchenne muscular dystrophy/Becker muscular dystrophy <br />Dystonia<br />Emanuel Syndrome<br />Fanconianemia, group C <br />Factor V-Leiden <br />Fragile X syndrome <br />Gaucher disease <br />Hereditary Hemochromatosis<br />Huntington's disease <br />Hereditary nonpolyposis colon cancer<br />Hemophilia A and B <br />Inherited breast and ovarian cancer<br />Marfan Syndrome<br />Mucopolysaccharidosi<br />Myotonic dystrophy <br />Neurofibromatosis type 1 <br />Phenylketonuria<br />Polycystic Kidney Disease<br />PraderWilli/Angelman syndromes <br />Sickle cell disease <br />Spinocerebellar ataxia, type <br />Spinal muscular atrophy <br />Tay-Sachs Disease <br />Thalassemias<br />Timothy Syndrome Galactosemia<br />
  22. 22. Methods for prenatal screening<br />
  23. 23. Indications for prenatal diagnosis<br /><ul><li> Abnormal results in prenatal screening
  24. 24. Previous child with a chromosome abnormality </li></ul> (probability of translocation carrier in parents)<br /><ul><li> Family history of a chromosome abnormality
  25. 25. Family history of a single gene disorder
  26. 26. Family history of neural tube defect or other </li></ul> congenital abnormalities<br />
  27. 27. Newborn Screening Tests:<br />Maple Syrup Urine Disease<br />Congenital Adrenal Hyperplasia<br />Congenital Hypothyroidism<br />Glactosemia<br />Biotinidase Deficiency<br />Homocystinuria<br />Phylketonuria (PKU)<br />Sickle cell and Other Hemoglobinopathies<br />
  28. 28. Pre implantation Genetic Diagnosis (PGD)<br />Pre implantation Genetic Diagnosis (PGD) uses in vitro fertilisation (IVF) to create embryos.<br />Tests one or two cells from each embryo for a specific genetic abnormality.<br />Identifies unaffected embryos for transfer to the uterus.<br />The approach through PGD assists couples at risk of an inherited disorder to avoid the birth of an affected child without going through selective pregnancy termination.<br />
  29. 29. Pros and cones of gene testing <br /><ul><li> To clarify a diagnosis and direct a physician
  30. 30. To avoid having children with devastating diseases
  31. 31. Identify people at high risk
  32. 32. Provide doctors with a simple diagnostic test
  33. 33. Transforming it from a usually fatal condition to a treatable one
  34. 34. Possibility of laboratory errors
  35. 35. Potential for provoking anxiety, and risks for discrimination</li></ul> social stigmatization could outweigh the benefits of testing<br />
  36. 36. Genetic counseling <br />
  37. 37. Genetic counseling <br /><ul><li> The process by which patients or relatives, at risk of an inherited disorder, are advised of the consequences and nature of the disorder, the probability of developing or transmitting it,
  38. 38. This complex process can be seen from diagnostic (the actual estimation of risk) and supportive aspects. </li></li></ul><li>When can we do counseling? <br /><ul><li>Conception (i.e. when one or two of the parents are </li></ul> carriers of a certain trait)<br /><ul><li>During pregnancy (i.e. if an abnormality is noted on an </li></ul> ultrasound or if the woman will be over 35 at delivery)<br /><ul><li>After birth (if a birth defect is seen)
  39. 39. During childhood (i.e. if the child has developmental </li></ul> delay)<br /><ul><li>During adulthood (for adult onset genetic conditions </li></ul> such as Huntington’s disease or hereditary cancer <br /> syndromes). <br />
  40. 40. <ul><li>The couple should be counselled by a genetic counsellor to inform them of the test results and the risks to the foetus.
  41. 41. Providing the options open to them in management and family planning in order to prevent, avoid or ameliorate it.
  42. 42. Autonomy of decision is crucial.
  43. 43. The ethical, legal, and religious issues should be respected.</li></li></ul><li>Direct-to-Consumer (DTC) genetic testing<br /><ul><li> A type of genetic test that is accessible directly to </li></ul> the consumer without having to go through a <br /> health care professional.<br /><ul><li> A variety of DTC tests, ranging from testing for </li></ul> breast cancer alleles to mutations linked to cystic <br /> fibrosis. <br /><ul><li> Benefits of DTC testing are the accessibility of </li></ul> tests to consumers, promotion of proactive <br /> healthcare and the privacy of genetic information.<br /><ul><li>Risks of DTC testing are the lack of governmental </li></ul> regulation and the potential misinterpretation of <br /> genetic information.<br />
  44. 44. Gene therapy<br />
  45. 45. Gene therapy is the replacement of faulty genes.<br />Introduction of functional <br />genetic material into target<br />cells to replace or <br />supplement defective <br />genes, or to modify target <br />cells so as to achieve <br />therapeutic goals.<br />
  46. 46. In theory it is possible to transform either somatic cells (most cells of the body) or cells of the germ line (such as sperm cells,ova, and their stem cell precursors). <br />
  47. 47. <ul><li>All gene therapy so far in people has been directed at somatic cells.
  48. 48. Germ line engineering in humans remains only a highly controversial prospect. </li></li></ul><li> For the introduced gene to be transmitted normally to offspring, it needs not only to be inserted into the cell, but also to be incorporated into the chromosomes by genetic recombination<br />
  49. 49. Somatic Cell Therapy<br />This is when a gene is introduced into a<br />patient to help them recover from a <br />disease.<br />
  50. 50. Germ Line Therapy<br />Changes are made to genes that will affect <br />subsequent generations.<br />
  51. 51. Applications of Gene Therapy<br />Radical cure of single gene diseases e.g.<br /> cystic fibrosis, haemoglobinopathies.<br />Amelioration of diseases with or without a genetic component e.g. malignancies, neurodegenerative diseases, infectious diseases.<br />
  52. 52. Gene therapy concerns <br />
  53. 53. Vectors in gene therapy:<br />Non-viral methods <br />Viruses <br />Adeno-associated viruses <br />Retroviruses <br />Oligonucleotides <br />Hybrid methods <br />Lipoplexes and polyplexes<br />Adenoviruses <br />Naked DNA <br />Envelope protein pseudotyping of viral vectors <br />
  54. 54.
  55. 55. Gene therapy using an adenovirus vector.<br />A new gene is inserted into an adenovirus vector, <br />which is used to introduce the modified DNA into a <br />human cell. If the treatment is successful, the new <br />gene will make a functional protein. <br />
  56. 56. Non viral vectors<br />Un complexed plasmid DNA <br />DNA coated gold particles<br />Liposomes<br />DNA – protein conjugates<br />
  57. 57. Modes of introducing genetic material<br />
  58. 58. Un complexed Plasmid DNA<br />Purified DNA or mRNA injected directly<br /> into tissues<br /> Injected into muscle and skin<br />• Utility in immunization/ vaccination against<br /> Infectious diseases<br /> • Ectopic synthesis of therapeutic proteins<br /> as erythropoietin.<br />
  59. 59. DNA coated Gold particles<br /><ul><li> Plasmid DNA + Gold particles ( 1 micron india)
  60. 60. “shot” into cells using electric spark or</li></ul> pressurized gas – “gene gun”<br /><ul><li> Epidermis
  61. 61. Skin tumours (melanomas)
  62. 62. Gene mediated immunization</li></li></ul><li>Liposomes<br />• DNA surrounded by hydrophobic molecules<br />• Anionic – given i.v. Targets reticuloendothelial cells of liver<br />• Cationic – transgene expression in most tissues if given in afferent blood supply<br />• Intra airway injection or aerosol to target -lung epithelium<br />
  63. 63. DNA- Protein conjugates<br />• Cell- specific DNA delivery systems<br />• Utilize unique cell surface receptors on<br />target cells<br />• Chemical cross linking methods used<br />
  64. 64. Methods <br /><ul><li> A normal gene may be inserted into a nonspecific location </li></ul> within the genome to replace a nonfunctional gene. <br /><ul><li> An abnormal gene could be swapped for a normal gene </li></ul> through homologous recombination. <br /><ul><li>The abnormal gene could be repaired through selective </li></ul> reverse mutation, which returns the gene to its normal <br /> function. <br /><ul><li>The regulation (the degree to which a gene is turned on or off) </li></ul> of a particular gene could be altered. <br />
  65. 65. Gene Transfer techniques<br />• In vivo<br />Suspension containing vector is injected<br />directly into the patient either systemically (i.v.)<br />or directly into target tissue (e.g. malignant<br />tumour)<br />• Ex vivo<br />Target cells (stem cells,myoblasts,fibroblasts<br />etc) removed from the patient, treated with<br />vector and injected back into the patient<br />
  66. 66.
  67. 67.
  68. 68.
  69. 69. Spectrum of gene expression<br />Gene replacement for single gene disorders<br />Gene repair<br />Gene inactivation<br />Ectopic synthesis of therapeutic proteins<br />Cancer gene therapy<br />
  70. 70. A) Immunodeficiency Disorders<br /> Adenosine Deaminase Deficiency<br /> X- linked SCID<br /> Chronic Granulomatous disease<br />B) Liver Disease<br />Familial Hypercholesterolemia<br />Haemophilia A<br />Target diseases <br />
  71. 71. Hemoglobinopathies<br />D) Lung Diseases<br /> • Cystic Fibrosis<br />• α- 1 Antitrypsin Deficiency<br />E) Skeletal Muscle<br /> • Duchene Muscular Dystrophy<br /> • Limb Girdle Muscular Dystrophy<br />
  72. 72. Challenges<br /><ul><li>Short-lived nature of gene therapy
  73. 73. Difficult to treat multi gene or multi factorial disease
  74. 74. Inserting gene into correct cells.
  75. 75. Controlling gene expression. Possibility of over expression
  76. 76. Damage to the host gene
  77. 77. Acquirement of virulence
  78. 78. Chance of inducing a tumour (insertional mutagenesis) </li></li></ul><li>Conclusion <br />
  79. 79. Thank u all….<br />