The Transgenic Study of Mus musculus

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The Transgenic Study of Mus musculus

• by Brian Stephenson
• and Arthur Musarra

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After Implantation.

• Placenta- nutrients through blood supply and
  waste removal
• Gastrulation cells differentiate to germ layers
• Endoderm
• Ectoderm
• Mesoderm
• 21 days later birth
• 5-6 weeks following ready to breed

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Uses of Transgenic Tools

• determine the function of gene products
• characterize genetic regulatory regions
• est. links between mutant phenotypes and
  particular transcriptional units to identify a
  cloned gene
• create mouse models of human diseases

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Two Transgenic Techniques

• Nuclear Injection
• Targeted Mutagenesis

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Nuclear Injection

• Injection of foreign DNA into a pronucleus which
  is placed back into a female oviduct for
  development
• This process creates a transgenic mouse
• Transgene comes from animals, plant, microbial,
  DNA synthesis

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Limitations to Nuclear Injection

• Only add not subtract genetic material
• Cannot target insertion of DNA to specific
  genomic locations

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Targeted Mutagenesis

• Replaces current allele with a new allele of
  different function
• undifferentiated
• altered cells, known
• as embryonic stem
• cells, injected into the
• blastocoele
• This is known
• as transfection

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Targeted Mutagenesis

• Specific allele may be replaced with new allele
• These alleles may be knockout constructs

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Determining Gene Function

• Using transgenic technology geneticists showed
  that cloned SRY gene encodes male sex organs
  without a Y chromosome

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Models of Disease

• non-cancerous animal cells have a very low level
  of myc gene expression
• gene discovered in the myelocytomatosis chicken
  retrovirus
• exposure generated tumors at high levels of gene
  expression

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Models of Disease

• To test myc gene used transgenic line of
• immunoglobulin- producing B-Cells
• tissue specific promoters - mammilary gland
• general tissue promoters
• Conclusion myc gene alone does not cause cells
  to become cancerous but can work with other
  mutations to cause cancerous growth

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Models of Disease

• use targeted mutagenesis to knockout genes for
  disease models
• ex CFTR gene for human cystic fibrosis
• enables further research to be done to correct
  loss of gene functioning in animal models

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To Study Genetic Regulatory Regions

• clone DNA with gene of interest and reg. region
• exchange DNA coding sequence for reporter lacZ
  gene from E. coli
• make several different forms of transgene for
  possible regulatory regions
• Tract and compare natural gene to map regulatory
  function

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Linking Gene to Phenotype

• a study used X-ray induced mutations that deleted
  a portion of DNA on chromosome 17 and mice
  developed short tails
• linked pme75 gene to tail length
• added pme75 to transgene construct and introduced
  to short tail mutants, offspring developed normal
  tails