11Pres - Human Gene Therapy • Different types of gene...

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Unformatted text preview: Human Gene Therapy • Different types of gene therapy • Gene addition versus gene replacement • Use of viral vectors for gene addition • First human gene therapy: severe combined immunode¡ciency (SCID) • Other attempts at somatic human gene therapy • Induced Pluripotent Stem Cells • Genetic modi¡cation of non-human mammals • Germ line gene therapy for humans? In a typical gene therapy, a viral vector is used to insert a foreign gene (“transgene”) into the genome of the targeted cell. August Weismann (1834-1914) was a descriptive and experimental embryologist until he lost his eye sight and became a theoretical biologist. He is best known for his concept of the germ line. The Germ Line Concept The germ line is a continuous lineage of cells that are capable of forming eggs or sperm. Germ line cells are potentially immortal, connecting individuals of successive generations in an uninterrupted chain. The other cells – collectively called soma- will die, having served as temporary caretakers of the germ line. Human Gene Therapy • Different types of gene therapy • Gene addition versus gene replacement • Use of viral vectors for gene addition • First human gene therapy: severe combined immunode¡ciency (SCID) • Other attempts at somatic human gene therapy • Induced Pluripotent Stem Cells • Genetic modi¡cation of non-human mammals • Germ line gene therapy for humans? Gene Addition vs. Gene Replacement Method for generating transgenic mice by microinjecting the cloned transgene into one pronucleus of a fertilized egg. From Kalthoff (2001) Supersized mouse (left) raised from an egg injected with a transgene for rat growth hormone. The mouse grew to twice the size of his uninjected litter mate (right). After Cummings (2006) Crossing Over Crossing over during meiosis produces chromosomes with new combinations of genetic alleles in gametes. Human chromosome 9 is shown. B, O: Genetic alleles for blood antigens B and O (no antigen). N: Mutant allele (dominant) of gene controlling nail-patella syndrome. n: Wild-type allele (recessive) of same gene. Homologous Recombination Traced with a Selectable Marker Embryonic stem (ES) cells are exposed to an engineered transgene, which replaces part of the resident target gene by homologous recombination. The neo R gene is used as a selectable marker to isolate transformed ES cells. In the strategy shown, a resident gene is inactivated (“knocked out”). Similarly, an additional gene can be “knocked in”, or a mutant gene can be replaced with its wild- type allele. From Kalthoff (2001) Gene replacement by homologous recombination Futuristic cell replacement therapy using isogenic, genetically repaired stem cells....
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This note was uploaded on 09/15/2010 for the course BIO 346 taught by Professor Kalthoff during the Spring '07 term at University of Texas.

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11Pres - Human Gene Therapy • Different types of gene...

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