The expression pattern of sept3, sept5a and sept5b in 1–4 dpf zebrafish larvae in a lateral view. Sept3, sept5a and sept5b expression is shown by ISH, the blue color indicates the cells expressing the mRNA of each septin. The expression of sept3 is shown in 1 dpf (A), 2 dpf (D), 3 dpf (G) and 4 dpf (J) zebrafish larvae. Sept5a expression is shown in 1 dpf (B), 2 dpf (E), 3 dpf (H) and 4 dpf (K) larvae. Zebrafish larvae 1–4 dpf stained with the sept5b probe are shown in (C,F,I,L). The telencephalon (Tel), habenula (Ha), diencephalon (Dic), the zona limitans intrathalamica (ZLI), cerebellum (Ce), tectum (TeO), eye, the spinal cord (Sc) as well as the hindbrain (H) are labeled. The border between hindbrain and spinal cord is marked by a dashed line. The midbrain-hindbrain boundary (MHB) is labeled (black arrowhead).

The expression pattern of sept3, sept5a and sept5b in 1–4 dpf zebrafish larvae in a dorsal view. Sept3, sept5a and sept5b expression is shown by ISH, the blue color indicates the cells expressing the mRNA of each septin. The expression of sept3 is shown in 1 dpf (A), 2 dpf (D), 3 dpf (G) and 4 dpf (J) zebrafish larvae. Sept5a expression is shown in 1 dpf (B), 2 dpf (E), 3 dpf (H) and 4 dpf (K) larvae. Zebrafish larvae 1–4 dpf stained with the sept5b probe are shown in (C,F,I,L). The eye, spinal cord (Sc) and hindbrain (H) are marked. The border between hindbrain and spinal cord is marked by a dashed line. Ventricular zones (white arrowhead) and the MHB (black arrowhead) are labeled.

Transverse sections through 2 dpf zebrafish larvae stained with ISH probes against sept3, sept5a and sept5b. 2 dpf zebrafish larvae were stained for sept3 (A,B,G,H,M,N,S,T,Y,Z), sept5a (C,D,I,J,O,P,U,V,Ä,Ö) and sept5b (E,F,K,L,Q,R,W,X,Ü,ß), embedded in epon, and cut in 8 μm thick section. The schemes (modified from Mueller and Wullimann, 2015) are showing the sagittal views of a 2 dpf zebrafish brain with indicated section planes. For better orientation the ISH sections were counterstained with Hoechst (A,G,M,S,Y,C,I,O,U,Ä,E,K,Q,W,Ü). Septin expression is indicated by the blue color (B,H,N,T,Z,D,J,P,V,Ö,F,L,R,X,ß). The retina (R), tectum opticum (TeO), tegmentum (T), preoptic region (Po), thalamus (Th), hypothalamus (Ht), medulla oblongata (Mo), cerebella plate (CeP), MHB and otic capsule (Oc), are marked. The ventricles are indicated with white arrowheads. Schemes for better orientation are modified from Mueller and Wullimann (2015) 2 dpf schemes.

Transverse sections through 4 dpf zebrafish larvae stained with ISH probes against sept3, sept5a and sept5b. 2 dpf zebrafish larvae were stained for sept3 (A,B,G,H,M,N,S,T), sept5a (C,D,I,J,O,P,U,V) and sept5b (E,F,K,L,Q,R,W,X), embedded in epon, and cut in 8 μm thick section. For better orientation, the ISH sections were counterstained with Hoechst (A,G,M,S,C,I,O,U,E,K,Q,W). Septin expression is indicated by the blue color (B,H,N,T,D,J,P,V,F,L,R,X). The tectum (TeO), preoptic region (Po), thalamus (Th), hypothalamus (Ht), cerebellum (Ce), the medulla oblongata (Mo) and the otic capsules (Oc), are marked. Additionally the migrated posterior tubercular area (M2) and the posterior tuberculum (Pt) are annotated. In the eye, the retinal ganglion cell layer (Rgl), the inner and outer nuclear layer (Inl and Onl), as well as the inner and outer plexiform layer (Ipl and Opl) are shown. The ventricles are indicated with white arrowheads. Schemes for better orientation with indicated section planes are modified from Mueller and Wullimann (2015) 5 dpf schemes, as these are structurally very close to the here shown 4 dpf sections.

Single confocal section trough 2 dpf zebrafish larvae stained with ISH probes against sept3 (A), sept5a (B), and sept5b (C) from a dorsal view. The larvae were additionally stained with an antibody against Proliferating Cell Nuclear Antigen (PCNA; A1,B1,C1). All three septins (magenta) are mostly not expressed in proliferating cells (green, A2,B2,C2).

Expression of sept3, sept5a and sept5b in adult zebrafish brains. The expression pattern of sept3 (A1–A6), sept5a (B1–B6) and sept5b (C1–C6) in adult brain sections are shown. The schemes (1–6) show corresponding sections from the zebrafish brain atlas (modified from Wullimann et al., 1996). Abbreviations can be found in Table 1. The anterior tuberal nucleus (ATN) is indicated in (C₂). The sept3 and sept5b positive layer in the TeO is labeld with black arrowheads. The inlays in (A'₄,B'₄,C'₄,A'₆,B'₆,C'₆) are showing magnified views of the boxed regions.

Expression of sept3, sept5a and sept5b in substructures of the adult zebrafish brain. The expression pattern of sept3 (A1–A5), sept5a (B1–B5), and sept5b (C1–C5) is shown in sagittal sections of adult brains. The regions of the brain are indicated in the scheme (1–5). In the telencephalon (1) sept3, sept5a and sept5b are expressed in dorsal telencephalic areas (Dm, Dc and Dp) and ventral telencephalic areas (Vd and Vv). Septins are expressed in a stream in the Vd region (outlined by dotted line). Additionally, sept3, sept5a and sept5b is expressed in the Ob. The sept3 and sept5b positive layer in the TeO is labeld with black arrowheads (A2,C2). In the cerebellum (3,5) sept3, sept5a and sept5b is expressed in the LCa, and in the region of the purkinje cell layer (PCL). Sept3 is additionally expressed in the CCe. Furthermore, hypothalamic sagittal section are shown (4). Abbreviations can be found in Table 1. To identify dopaminergic cells, ISH stained brains (magenta) against sept3 (D), sept5a (E), and sept5b (F) were counterstained with an antibody against tyrosine hydroxylase (TH, green in D1,E1,F1) and analyzed with a confocal microscope and merged (D2,E2,F2). Pictures in (D–F) are maximum projections of confocal slices through adult sagittal brain sections. Scale bars 200 μm.