Gene deserts bear fruit Regulatory elements identified in noncoding genomic sequences By
Cathy Holding
The evidence that "junk" DNA contains highly conserved sequences that have a regulatory function is
mounting: their genetic and (controversial) commercial value had been guessed at as long ago as
1989. In the October 17 Science, Marcelo Nobrega and colleagues at the US Department of Energy Joint
Genome Institute examined the "gene deserts" flanking the human DACH gene and report that they
contain several important enhancer functions that have been conserved across species in over a
billion years of parallel evolution (Science, 302:413, October 17, 2003).
Nobrega et al. compared human DACH flanking sequences with mouse genomic DNA and by combining
additional genome comparison information from distantly related vertebrates such as frog, zebrafish,
and pufferfish, narrowed the number of conserved sequences from 1098 to 32. Nine of these were
cloned upstream of the mouse heat shock protein 68 minimal promoter driving beta-galactosidase
expression. These were used to create transgenic mice whose subsequent development revealed enhancer
effects of the elements consistent with DACH endogenous gene expression. Genes flanking the DACH
orthologues vary with species, but the adjacent gene deserts were found to be maintained.
"The size of genomic regions believed to be functionally linked to a particular gene may need to be
expanded to take into account the possibility of essential regulatory sequences acting over near-
megabase distances," conclude the authors.
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Kind Regards, Robert Karl Stonjek.