Supplementary Material for: Alternative Transcripts of <i>Dclk</i>1 and <i>Dclk</i>2 and Their Expression in <i>Doublecortin</i> Knockout Mice

The <i>doublecortin</i> (<i>DCX</i>) gene, mutated in X-linked human lissencephaly, has 2 close paralogs, <i>doublecortin-like kinase</i> 1 and 2 (<i>Dclk</i>1 and 2). In this study we attempted to better understand the dramatic differences between human and mouse DCX/Dcx-deficient phenotypes, focusing on the <i>Dclk</i> genes which are likely to compensate for Dcx function in the mouse. Using sequence database screens, Northern blot analyses and in situ hybridization experiments, we characterized the developmental transcripts of <i>Dclk</i>1 and 2, questioning their conservation between mouse and human, and their similarity to <i>Dcx</i>. Like <i>Dcx</i>, <i>Dcx</i>-like transcripts of the <i>Dclk</i>1 gene are expressed in postmitotic neurons in the developing cortex. No changes of expression were observed at the RNA level for these transcripts in <i>Dcx</i> knockout mice. However, a minor change in expression at the protein level was detected. The <i>Dclk</i>2 gene is less well characterized than <i>Dclk1 </i>andwe show here that it is expressed both in proliferating cells and postmitotic neurons, with a notably strong expression in the ventral telencephalon. No major differences in <i>Dclk</i>2 expression at the RNA and protein levels were identified comparing <i>Dcx</i> knockout and wild-type brains. We also analyzed <i>Dclk</i>1 and 2 expression in the hippocampal CA3 region which, unlike the neocortex, is abnormal in <i>Dcx</i> knockout mice. Interestingly, each transcript was expressed in CA3 neurons, including in the heterotopic pyramidal layer of <i>Dcx</i> knockout animals, but is presumably not able to compensate for a lack of <i>Dcx</i>. These results, in addition to characterizing the transcript diversity of an important family of genes, should facilitate further studies of compensation in <i>Dcx</i>-deficient mice.