Rbfox1l is expressed in restricted populations of neurons in the adult zebrafish dorsal telencephalon and cerebellum, while Rbfox2 is expressed broadly throughout the brain. (A) Schematic of adult zebrafish brain (lateral view) with plane of section indicated for respective data panels B–M’. Asterisks indicate dorsal (*) and ventral (**) regions of sections imaged in (J-M′). (B–E) Rbfox1l expression in the adult zebrafish olfactory bulb and telencephalon (coronal sections, rostral to caudal). (F–I) Rbfox2 expression in the adult zebrafish olfactory bulb and telencephalon (on alternating sections to facilitate comparison with Rbfox1l) (coronal sections, rostral to caudal). (J-K′) Rbfox1l expression in the adult zebrafish midbrain, cerebellum, and medulla oblongata. *(D) and **(V) indicate dorsal and ventral regions of section imaged, respectively. (L-M′) Rbfox2 expression in the adult zebrafish midbrain, cerebellum, and medulla oblongata (on alternating sections to facilitate comparison with Rbfox1l) (coronal sections, rostral to caudal). Abbreviations: Medulla Ob., Medulla Oblongata. Scale bar for B-M′ is 300 μm.

 Rbfox1l is expressed in a specific population of dorsal telencephalic neurons in adult zebrafish. (A) Schematic of adult zebrafish brain indicating plane of section through the mid-caudal telencephalon (lateral view). Region of section corresponding to dorsal telencephalon is indicated by asterisk (*), while region of section corresponding to ventral telencephalon is indicated by a double-asterisk (**). (B-B″) Rbfox1l is expressed in a restricted population of neurons within the adult zebrafish dorsal telencephalon (pallium); coronal section showing dorsal telencephalon (*Dorsal). Dorsal telencephalic sub-regions are delineated by the dotted blue lines, as approximated based on previous studies (Ganz et al., 2015; Mueller et al., 2011; Northcutt, 2011; von Trotha et al., 2014). Rbfox1l-positive cells likely span Dm and Dc regions. (C-C″) Rbfox1l expression is largely absent in the ventral telencephalon (sub-pallium); same coronal section as in (B-B″) but showing ventral telencephalon (**Ventral). Approximate boundary between dorsal and ventral telencephalon is indicated by dotted white line. (D-D″) Higher magnification view of dorsal telencephalic Rbfox1l-positive neurons (coronal section). Abbreviations: Dm, medial zone of the dorsal telencephalon; Dc, central zone of the dorsal telencephalon; Dl, lateral zone of the dorsal telencephalon; Dp, posterior zone of the dorsal telencephalon; Vd, dorsal nucleus of the ventral telencephalon; Vv, ventral nucleus of the ventral telencephalon. Scale bar in B, C is 150 μm, and in D is 30 μm.

Rbfox1l-positive dorsal telencephalic neurons likely span Dm and Dc regions. (A) Schematic of adult zebrafish brain indicating plane of section through the mid-caudal telencephalon (lateral view). (B-B″) Coronal section of adult zebrafish dorsal telencephalon co-labeled for Parvalbumin7, which labels the Dc and Dl regions (red), and Rbfox1l (green). Dotted blue lines delineating the boundaries of Parvalbuminexpression approximate the telencephalic sub-regions, Dm, Dc, and Dl. Dp region is Parvalbumin7-negative. Rbfox1l-expressing neurons (green) are located largely within the Dc region, but also span the border into the Dm region. A small cluster of Rbfox1l-positive neurons within the Dm are indicated by a dotted blue circle (B″). (C-C″) Higher magnification view of boxed region in (B″). Parvalbumin7 is expressed in many neuronal fibers within the Dc region. Some Rbfox1l-positive neurons are clearly located within the Dc region (light blue arrowheads), while others are located near the border between Dc and Dm (white arrowheads). Abbreviations: Dm, medial zone of the dorsal telencephalon; Dc, central zone of the dorsal telencephalon; Dl, lateral zone of the dorsal telencephalon; Dp, posterior zone of the dorsal telencephalon. Scale bar in B is 150 μm and in C is 30 μm.

 Rbfox2 is expressed broadly in a majority of neurons within the adult zebrafish telencephalon. (A) Schematic of adult zebrafish brain indicating plane of section through the mid-caudal telencephalon (lateral view). Region of section corresponding to dorsal telencephalon is indicated by asterisk (*), while region of section corresponding to ventral telencephalon is indicated by a double-asterisk (**). (B-B″) Rbfox2 is expressed broadly in neurons throughout the adult zebrafish dorsal telencephalon (pallium); staining was performed on alternating coronal sections to those in Fig. 2 to facilitate comparison with Rbfox1l. Approximate pallial subdivisions are indicated by dotted blue lines. (C-C″) Rbfox2 is expressed in neurons of the ventral telencephalon (sub-pallium); coronal section. Approximate boundary between dorsal and ventral telencephalon is indicated by dotted white line. (D-D″) Higher magnification view of neurons spanning Dm and Dc regions (coronal section). Abbreviations: Dm, medial zone of the dorsal telencephalon; Dc, central zone of the dorsal telencephalon; Dl, lateral zone of the dorsal telencephalon; Dp, posterior zone of the dorsal telencephalon; Vd, dorsal nucleus of the ventral telencephalon; Vv, ventral nucleus of the ventral telencephalon. Scale bar in B, C is 150 μm, and in D is 30 μm.

Rbfox2 is expressed broadly in a majority of neurons within the diencephalon and midbrain. (A) Schematic of adult zebrafish brain indicating plane of section through the midbrain and diencephalon (lateral view). (B-B″) Rbfox2 is expressed broadly in a majority of neurons within the midbrain optic tectum (TeO; dotted blue line delineates the optic tectum); medial view. Rbfox2 expression is also detected in the torus longitudinalis (TL); coronal section. (C-C″) Rbfox2 is also expressed broadly in neurons of the lateral optic tectum (dotted blue line delineates the optic tectum); coronal section. (D-D″) Higher magnification view of Rbfox2 and HuC/D expression in the TeO shows that Rbfox2 is expressed in a majority of TeO neurons in the periventricular gray zone (PGZ); coronal section. (E-E″) Rbfox2 is expressed broadly within the diencephalon, including in the torus lateralis (TLa) and hypothalamus (H); coronal section. Abbreviations: TeO, optic tectum; Va, valvula cerebelli; TL, torus longitudinalis; TLa, torus lateralis; H, hypothalamus. Scale bar in B, C, E is 150 μm, and in D is 30 μm.

Rbfox1l and Rbfox2 are expressed in the Purkinje cell layer of the cerebellum. (A) Schematic of adult zebrafish brain indicating plane of section through the cerebellum (lateral view). (B-B″) Rbfox1l is expressed in the Purkinje cell layer (PCL) of the cerebellum (CCe, corpus cerebelli); coronal section. (C-C″) Higher magnification view showing Rbfox1l expression in a subset of neurons in the PCL, within the cytoplasm and dendrites of these cells that extend into the molecular layer (ML). (D-D″) Rbfox2 is expressed broadly in the cerebellum, in neurons of the granule cell layer (GCL) and in the PCL; coronal section. (E-E″) Higher magnification view showing Rbfox2 expression in PCL neurons; coronal section. Abbreviations: CCe, corpus cerebelli; ML, molecular layer; PCL, Purkinje cell layer; GCL, granule cell layer. Scale bar in B, D is 150 μm, and in C, E is 30 μm.

Rbfox1l and Rbfox2 are expressed in Parvalbumin7-positive Purkinje cells of the cerebellum. (A-A″) Rbfox1l and Parvalbumin7 colocalize in the Purkinje cell layer (PCL) of the cerebellum. (B-B″) Higher magnification view of boxed regions in (A-A″) showing overlap of Rbfox1l and Parvalbumin7 in the PCL. PCL is located immediately above dotted white line. (C-C″) Rbfox2 and Parvalbumin7 colocalize in the Purkinje cell layer (PCL) of the cerebellum. (D-D″) Higher magnification view of boxed region in (C-C″) showing overlap of Rbfox2 and Parvalbumin7 in the PCL. PCL is located immediately above dotted white line. Abbreviations: ML, molecular layer; PCL, Purkinje cell layer; GCL, granule cell layer. Scale bar in A, C is 150 μm, and in B, D is 30 μm.