MIP is expressed in the digestive system of 6 dpf
. (A) Whole-mount RNA in situ hybridization (WMISH) for the Platynereis MIP precursor (red) counterstained with DAPI nuclear stain (blue). Ventral view of 6 dpf Platynereis with the image stacks corresponding to the ventral nerve cord (VNC) region not included in the maximal projection (outlined with white dashed line). White asterisks indicate background reflection from chaetae. (B, C) Close-up WMISH for the Platynereis MIP precursor (red) counterstained for acetylated tubulin (α-acTub) (white) and DAPI nuclear stain (blue). Yellow arrowheads indicate sensory dendrites of MIP-expressing cells. (B) Ventral view of the foregut. (C) Ventral view of the midgut and hindgut. (D) Dorsal view of surface representation of average MIP precursor expression domains registered to a 6 dpf nuclear stain reference template. Expression domains of alpha-amylase, legumain protease precursor, subtilisin-1, subtilisin-2 and enteropeptidase are included as digestive system markers. White arrows indicate areas of MIP expression associated with the digestive system. (E, F) Immunostaining with Platynereis MIP antibody (red) counterstained with acetylated tubulin (grey) at 6 dpf, with the image stacks corresponding to the VNC region not included in the maximum projection to show only the digestive system. (E) Ventral view of foregut. (F) Ventral view of hindgut. White asterisks indicate background reflection from spinning glands. (G-I) Schematic representation of MIP precursor expression in 6 dpf Platynereis. (G) Ventral side. (H) Dorsal side. (I)
MIP expression relative to expression of digestive system marker genes in the gut. In (A, B, E), yellow dashed lines indicate the jaws. Scale bars: 50 μM. Abbreviations: fg, foregut; mg, midgut; hg, hindgut; ant, antenna; nsp, neurosecretory plexus; adc, anterior dorsal cirrus; pp, parapodia; vnc, ventral nerve cord; ch, chaetae; ac, anal cirrus; ph, pharynx.