Scanning Human Gene Deserts for LongRange Enhancers

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Scanning Human Gene Deserts for Long-Range
Enhancers

• Nobrega, M., et al. 2003. Scanning human gene
  deserts for long-range enhancers. Science
  302413. Online URL
• lt www.sciencemag.org/cgi/conten/full/302/5644/413
  gt

2
Hypothesis

• There are regulatory sequences in gene deserts
  that are responsible for the complex expression
  of the DACH gene in humans.

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Background

• Gene Desert gene-poor region greater than 500
  kb
• 25 of human genome consists of gene deserts
• DACH gene is expressed in numerous tissues, and
  is involved in development of brain, limbs, and
  sensory organs
• DACH gene is 430 kb and is bracketed by 2 gene
  deserts 870 kb and 1330 kb
• TATA Box Part of the promoter sequence in
  transcription and is located about 10bp from the
  starting point
• Introns Must be excised from pre-mRNA to
  generate a mature mRNA that can be translated
  into a complete polypeptide

4
Experiment

• Compared DACH sequence and gene deserts to mouse
  DACH sequence
• Also compared to frog, zebrafish, and 2
  pufferfish
• Found 32 conserved sequences
• Tested to see if these 32 sequences represent
  enhancers

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Experiment Continued

• Tested 9 elements from the 2 gene deserts and
  DACHs introns
• Cloned the elements upstream of heat shock
  protein 68 minimal promoter coupled to
  ß-galactosidase
• Injected clones into fertilized mouse oocytes

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Results and Conclusions

• 7 of the 9 elements were shown to drive
  ß-galactosidase in certain tissues
• Many of these enhancers reside in gene deserts
• Shows good support that gene deserts can serve as
  reservoirs for these long range enhancers
• Size of genomic regions that are linked to the
  expression of a gene should be expanded to
  include much larger regions than originally
  believed

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