Tranasgenic Mice

8/11/2019 Tranasgenic Mice

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Using DNA Technology to Produce

Transgenic Animals


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Transgenic Animals: A Focuson Transgenic Mice Studies

http://www.hku.hk/biochem/tgcentre/transcentre.html
http://www.hku.hk/biochem/tgcentre/transcentre.htmlhttp://www.hku.hk/biochem/tgcentre/transcentre.html


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I. IntroductionTransgenic animals:

Animals which have been genetically engineered tocontain one or more genes from an exogenous source.

Transgenes are integrated into the genome.

Transgenes can be transmitted through the germline to progeny.

First transgenic animal produced = Founder Animal


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II. Introduction of foreign genesinto intact organisms

Procedure is basically the same regardless ofwhich animal is involved.

Integration usually occurs prior to DNAreplication in the fertilized oocyte.

Majority of transgenic animals carry the gene in all oftheir cells, including the germ cells. Transmissionto next generation requires germline integration.

Some integration events occur subsequent to DNAreplication giving rise to mosaic animals which may or

may not contain the transgene in its germline.


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III. Procedure for Producing

Transgenic Mice

Three different breeding pairs of mice arerequired.


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First Breeding Pair: Fertile male + superovulated female

Fertile male = stud (changed regularly to ensure performance)

Superovulated female = immature female induced tosuperovulate

Pregnant mares serum (=FSH) on day 1 Human Chorionic Gonadotropin (=LH) on day 3

Mated on day 3

Fertilized oocytes microinjected on day 4 with foreign DNAconstruct.

Microinjected oocytes are transferred to the oviducts ofsurrogate mothers at end of day 4.


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Second breeding pair: Sterile male + surrogate mother

Sterile male produced through vasectomy Surrogate mother must mate to be suitable recipient of

injected eggs Mated on day 3 Microinjected oocytes from first breeding pair are

transferred to oviducts on day 4 Embryos implant in uterine wall and are born 19 days later.

Southern blotting techniques confirm presence and copynumber of transgenes.


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Third breeding pair: Foster parents

Fertile male + female mated to give birth on sameday surrogate mother

Serves as foster parent if caesarian section isrequired for surrogate mother


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http://www.itba.mi.cnr .it/human_g...transgenic.html
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V. Gene Expression inTransgenic Mice

In order to discriminate the products of theinjected gene from those of an endogenouscounterpart, the injected gene must be marked insome way. Mini-genes where exons are deleted of cDNA where

introns are absent. Modification by insertion/deletion/mutagenesis of a few

nucleotides (e.g. the gain or loss of a restrictionendonuclease site). Hybrid genes where foreign epitopes are expressed on

transgenic products.


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VI. Tissue-Specific GeneExpression

Generally, if a tissue-specific gene is expressed at all, thenit is expressed appropriately, despite the fact that it hasintegrated at a different chromosomal location.


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VII. Examples of StudiesUtilizing Transgenic Mice

Pharm animals (transgenic livestock)

Bioreactors whose cells have been engineered tosynthesize marketable proteins

DNA constructs contain desired gene and appropriateregulatory sequences (tissue-specific promoters)

More economical than producing desired proteins incell culture


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Naked human Hb from pigsHuman lactoferrin in

cows milk Alpha-1-antitrypsin insheepHGH in mouse urine(uroplakin promoters)Human antibodies in mice(H and L chain tgenics hybridomas)

CfTCR in goatsTissue plasminogenactivator (TPA) in goatsHuman antithrombin III ingoatsMalaria antigens in goats(vaccine)Alpha-glucosidase inrabbits (Pompes disease


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VIII. Transgenic Pigs for theProduction of Organs for

TransplantationPig organs are rejected acutely due to the presenceof human antibodies to pig antigens.

Once human antibodies are bound to pig organs,human complement is activated and triggers thecomplement cascade and organ destruction.

Transgenic pigs with complement inhibitors have been produced and are gaining feasibility as asource of xenogeneic organs for transplantation.

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Tranasgenic Mice