Fig. 3

Alternative splicing of exon 38b determines soma-dendritic transport of SORL1 transcripts. a RT-PCR using primers in exon 38b and 40 (E38b–E40) revealed the presence of the additional splicing event with skipping of exon 39 downstream the novel 38b cassette. b Schematic of BaseScope probe design for targeting SORL1-38b transcripts containing (E38bE39, blue) or excluding exon 39 (E38bE40, red). c Representative image of BaseScope Duplex using the probes E38bE39 (blue) and E38bE40 (red) shows that exon 39 is not responsible for soma retention. Scale bar, 20 μm. d Junction-spanning reads in human brain regions confirm the existence of two SORL1-38b transcripts from inclusion or exclusion of exon 39. Numbers represent the relative frequency of SORL1-38b reads among all SORL1 reads (%). e BaseScope analysis using probes E38E38b and E38E39 shows the presence of extra-somatic SORL1-38b transcripts in different human brain areas. Signals for E38E39 that represent SORL1-fl are predominantly located in the neuronal soma. Ento ctx entorhinal cortex, Hip hippocampus, DG dentate gyrus. Scale bar, 50 μm. f Immunostaining of human cerebellum with an antibody raised against the cytoplasmic tail (SORLA-cyt) of SORLA-fl reveals that the full-length protein is mainly located to the soma of PCs. Staining with antibodies against the luminal part of SORLA (SORLA-lum; LR11, 5387) shows labeling of soma as well as dendrites of PCs (indicated with arrowheads)