Figure 6. Qualitative expression analysis of alternative Lrrk2 mRNA transcripts.

RNA samples from different brain regions and organs were analysed by RT-PCR using a primer combination that amplifies Lrrk2 transcripts between exon 4 and exon 9 (A). Note that there is – beside the band of the endogenous Lrrk2 (ex.4–9) – an additional lower band visible in all samples analysed representing a mRNA where exon 5 is spliced out (ex.5 skipped) (B). The same primers were used to analyse RNA samples from primary neuronal cultures (i.e. neurons, microglia and astrocytes) (C). Interestingly, the band representing the splice variant without exon 5 (E5 skipped) was dominantly expressed in samples from astrocytes, while the band for the endogenous transcript (E4–E9) was almost completely missing in these cells. (D) RNA samples were analysed by RT-PCR using primers that amplify Lrrk2 transcripts between exon 39 (E39) and an alternative exon 42a (ex.42a). Note that the alternative exon 42a is present in all samples analysed (ex.39–42a). (E) The same primers were used to analyse RNA samples from primary neuronal cultures (i.e. neurons, microglia and astrocytes). Interestingly, the alternative exon 42a could not be amplified from primary microglia cDNA. (F) Relative expression level as measured by quantitative RT-PCR with primers and probes specific for either the endogenous Lrrk2 transcript (full-length Lrrk2), or for the alternative Lrrk2 mRNA transcripts with skipped exon 5 (ex.5 skipped). The relative expression is depicted as a ratio between endogenous Lrrk2 transcript and the alternative product on a logarithmic scale. (G) Accordingly for the alternative Lrrk2 mRNA transcript ending in the alternative exon 42a (alt.ex.42), the relative expression level have been determined by quantitative RT-PCR with specific primers and probes for the alternative product and normalized to the expression of the endogenous Lrrk2 transcript (full-length Lrrk2).