Fig. 2.

pros^long isoform is expressed in larval brains and is specifically transcribed in larval neurons. (A) Diagram showing annotated pros transcript isoforms and the position of smFISH (pros long intron, pros and pros long UTR) and northern blot probes (grey bars). (B) Northern blot confirms the existence of multiple pros mRNA isoforms at 6 kb, 9 kb and 21 kb (red arrows) in the larval CNS. The 21 kb isoform corresponds to pros transcript with 15 kb 3′ UTR. E, embryo; L, larval CNS. (C) Costaining with pros exon and pros long UTR smFISH and Pros IF shows that pros^long RNA is detected only in neurons. In the NB (white dotted outline), or the GMCs (pink dotted outline), pros exon is detected without pros long UTR. Pros protein is upregulated in cells expressing pros^long. (D) pros long intron probe only recognises the nascent transcripts of the pros^long isoform. pros long intron is detected exclusively in neurons, and not in the NB (white dotted outline) or GMCs (pink dotted outline). Scale bars: 10 µm.