<p>This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.</p> <p>Imprinted genes exhibit silencing of one of the parental alleles during embryonic
development. In a previous study imprinted genes were found to have reduced intron
content relative to a non-imprinted control set (Hurst <italic>et al</italic>., 1996). However, due
to the small sample size, it was not possible to analyse the source of this effect.
Here, we re-investigate this observation using larger datasets of imprinted and control
(non-imprinted) genes that allow us to consider mouse and human, and maternally
and paternally silenced, imprinted genes separately. We find that, in the human and
mouse, there is reduced intron content in the maternally silenced imprinted genes
relative to a non-imprinted control set. Among imprinted genes, a strong bias is
also observed in the distribution of intronless genes, which are found exclusively
in the maternally silenced dataset. The paternally silenced dataset in the human is
not different to the control set; however, the mouse paternally silenced dataset has
more introns than the control group. A direct comparison of mouse maternally and
paternally silenced imprinted gene datasets shows that they differ significantly with
respect to a variety of intron-related parameters. We discuss a variety of possible
explanations for our observations.</p>
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Comp Funct Genomics. 2004 Dec; 5(8):572-583