Exression of sept8aand sept8b in embryonic and early larvae zebrafish revealed by RNA in situ hybridization.

1–4 dpf zebrafish are shown in dorsal and lateral views. Head structures are enlarged in the right-hand panels. A – H: sept8a expression was primarily detectable in ventral body regions at 1 dpf and additionally in single brain structures at 2 dpf. At 3 dpf and 4 dpf sept8a expression was detectable in the gill arches and the brain. I – P: sept8b transcripts were also detectable in ventral regions as well as in cells above the yolk extension (black arrowheads) at 2 dpf. sept8b showed a specific distribution in the midbrain and hindbrain of 2–4 dpf zebrafish. See list for abbreviations. The boxed area in J is enlarged in the inset image. The dotted line in K marks the level of the transverse section shown in the inset image. Scale bars: Whole mounts: 500μm Head structures: 200μm Insets: 50μm.

Spatiotemporal development of the sept8b expression pattern in the developing zebrafish brain.

Expression of sept8b is shown at 48 hpf (A), 52 hpf (B) and 60 hpf (C) as well as at 72 hpf (D) and 96 hpf (E). sept8b expression in the developing brain was detectable as consecutive appearing bilateral pairs of cells at 48–60 hpf. The symmetric pattern started to converge from the posterior at 72 hpf to form a triangular shape. Scale bar: 100μ.

sept8a expression in the CNS of 2 dpf zebrafish.

Images of transverse epon sections of 2 dpf zebrafish stained for sept8amRNA and counterstained with Hoechst33258 (B – H). Section levels and angle are displayed in the schematic drawing (A). sept8a expression was weakly detectable in cells in the entire brain (B – H), as well as in the retina (C – E) and the lens (C, D). Strong sept8a expression was observed in two large nuclei (arrowheads) close to the SR (G). See list for abbreviations. Brain schemes were modified from Müller and Wullimann (2016). Scale bars: B – H: 100μm Insets: 25μm.

sept8a expression in the CNS of 4 dpf zebrafish.

Transverse epon sections of 4 dpf zebrafish labeled for sept8a transcripts and counterstained with Hoechst33258 (B – H). Level and angle of sections are displayed in the brain scheme (A). Note that the illustrated scheme displays the structure of a 5 dpf zebrafish brain and, thus, can only be used for rough orientation. sept8a expression was detectable in cells in the forebrain and midbrain. sept8a expressing cells were further concentrated in the INL (B – D), at border regions of the TeO above the CeP (E, F) and in the EG (F). Two discrete regions showing strong sept8a expression (indicated by arrowheads) were located close to the SR (G). See list for abbreviations. Brain schemes were modified from Müller and Wullimann (2016). Scale bars: B – H: 100μm; Insets: 25μm.

sept8b expression in the CNS of 2 dpf zebrafish.

sept8b expression in the CNS of 4 dpf zebrafish.

Images of transverse epon sections of 4 dpf zebrafish after labelling of sept8b transcripts via RNA in situ hybridization, counterstained with Hoechst33258 (B – H). Levels and angle of sections are illustrated schematically in the drawing (A). Note that the illustrated scheme displays the structure of a 5 dpf zebrafish brain and, thus, can only be used for rough orientation. sept8b transcripts could be detected in ventricular cells of the forebrain and midbrain (B – D), the Va and at border regions between TeO and CeP (E, F), in cells of the RL (G, H) as well as in accumulations of cells in the H (E) and the EG (H) and in single cells close to the SR (G). See list for abbreviations. Brain schemes were modified from Müller and Wullimann (2016). Scale bars: B – H: 100μm.

Expression of sept8a and sept8b in the adult zebrafish brain.

Schemes in the left panel display the corresponding sections from the zebrafish atlas. The expression patterns of sept8a (A1 – A6) and sept8b (B1 – B6) revealed large overlaps throughout the entire brain. However, sept8a was uniquely expressed in the DIL, CM (A3, A4), PL, NLL, NLV (A4) and CCe (A5). sept8b revealed a scattered expression in the TeO (B2 – B4), TL (B3, B4), DON, CON and MON (B5 – B6) as well as a ventricular preference. The ventricles (TelV, LR, RV and TeV) are indicated in addition to the described expression pattern in the text. See list for abbreviations. Brain schemes were modified from Wullimann et al. (1996). Scale bar: 200μm.

Sense controls of RNA in situ hybridization against sept8a and sept8b.

Whole mount images of the sense controls for sept8a (A – H) and sept8b (I – P) RNA in situ hybridization. Background signal was visible only in the PiCL and in a small streak across the head. Scale bars: A – P: 500μm.