Alternative Splicing of a Novel Inducible Exon Diversifies the CASK Guanylate Kinase Domain

Figure 1

Identification of a highly conserved, responsive exon of the mouse CASK transcript. (a) RNA samples used for RT-PCR validation of splicing pattern changes were derived from cortical cultures following mock treatment (lanes M) or stimulation with high KCl (lanes K). Additional samples were supplemented with MK801 and APV to attenuate the splicing response (lanes Kx). Gel panels illustrate the exon included (*) and skipped (**) products amplified by primers specific for the flanking exons of GRIN1 E19 (left panel), CASK E24a (middle panel), and MAPT E12 (right panel). Numbers at bottom of gel panels represent the % exon inclusion (%EI) values for each lane. The schematics above summarize the observed changes in exon inclusion for E19 and E24a and the unresponsive exon-skipping pattern of E12. Graph at right shows the change in exon inclusion (ΔEI) values for E19 and E24a as a function of stimulation with (white bars, +) and without (grey bars, −) MK801 and AP5. (b) The exon-intron structure of the mouse CASK gene is shown using the exon-numbering scheme from the Ensembl CASK-001 transcript; corresponding protein domains (color-coded) are shown above. The position of E24a (white box) as identified in this study is shown. (c) Expanded region shows the sequence conservation of E24a (Multiz Alignment) and its position in the context of the full-length intron 24. Exon/intron sizes (base pairs) are indicated in parentheses. Note that the sequence of mouse E24a corresponds to coordinates 12,688,825–12,688,945 on the X chromosome from UCSC Genome Browser, 2006 genome assembly. Arrows indicate primers used for the RT-PCR analysis of (a). (d) The confirmed sequence of E24a (uppercase) and adjacent 5′ and 3′-splice sites (underscored) are shown. Colons indicate exon/intron boundaries.