Temporal and tissue specific gene expression patterns of the zebrafish kinesin-1 heavy chain family, kif5s, during development

Abstract

Homo- and heterodimers of Kif5 proteins form the motor domain of Kinesin-1, a major plus-end directed microtubule motor. Kif5s have been implicated in the intracellular transport of organelles, vesicles, proteins, and RNAs in many cell types. There are three mammalian KIF5s. KIF5A and KIF5C proteins are strictly neural in mouse whereas, KIF5B is ubiquitously expressed. Mouse knockouts indicate crucial roles for KIF5 in development and human mutations in KIF5A lead to the neurodegenerative disease Hereditary Spastic Paraplegia. However, the developmental functions and the extent to which individual kif5 functions overlap have not been elucidated. Zebrafish possess five kif5 genes: kif5Aa, kif5Ab, kif5Ba, kif5Bb, and kif5C. Here we report their tissue specific expression patterns in embryonic and larval stages. Specifically, we find that kif5As are strictly zygotic and exhibit neural-specific expression. In contrast, kif5Bs exhibit strong maternal contribution and are ubiquitously expressed. Lastly, kif5C exhibits weak maternal expression followed by enrichment in neural populations. In addition, kif5s show distinct expression domains in the larval retina.

Fig. 1

Vertebrate Kif5 protein comparison. (A) Schematic of the protein domains of a Kif5 dimer. (B) Conservation of amino acid sequence between zebrafish, mouse, and human Kif5s. (C) Phylogenetic relationship between zebrafish, mouse, and human Kif5 proteins. Orthologs are shown in the same color (Kif5A, brown; Kif5B, red; Kif5C, blue) and paralogs are denoted with an asterisk (*). The length of the branches represents the degree of change between the sequences. M, Motor domain; NL, Neck linker; NCC, Neck coiled-coil; H1, Hinge 1; CC1, Coiled-coil 1; H2, Hinge 2; CC2, Coiled-coil 2; T, Tail.

Fig. 2

Graphs indicate the probability (y-axis) of a paired coiled coil fold occurring at a given amino acid position (x-axis) for each of the zebrafish Kif5s. Brown arrowheads denote Kif5A-specific non-coiled coil region within CC2, brown bracket denotes Kif5Ab-specific divergent region of CC1, and black arrows denote Kif5Ab-specific divergent region of CC2.

Fig. 3

(A) Temporal analysis of zebrafish kif5s during development by RT-PCR. (B) RT-PCR analysis of zebrafish kif5 tissue and organ specific expression. Asterisk (*) indicates faint bands present. NRT, no reverse transcriptase.

Fig. 4

kif5 expression during early zebrafish development. Maternal expression of kif5s was apparent in cleavage stage for kif5Ba, kif5Bb, and kif5C, but not kif5Aa (A–D). Expression of kif5s at sphere (E–H), shield (I–L), bud (M–P), 15 somite (Q–T), and 19 somite (U–X) stages. Arrowheads indicate trigeminal ganglion and arrows indicate otic placode. All images are lateral views. For A–L, An=Animal pole, Vg=vegetal pole. For M–X, A=Anterior, P=Posterior, V=Ventral, D=Dorsal. Dashed line represents border between notochord and spinal cord. fb, forebrain; mb, midbrain; hb, hindbrain; ey, eye.

Fig. 5

Expression of kif5s at 24hpf and 36hpf. (A–E) Lateral views of whole mount in situs at 24hpf. kif5Aa, kif5Ab, and kif5C were detected in the telencephalon (te), diencephalon (di), and hindbrain (hb). kif5Aa and kif5C were also detected in the tegmentum (tg), epiphysis (ep), and spinal cord (sc). kif5Ba and kif5Bb were ubiquitously expressed. (F, G) Dorsal view of flat mounts at 24hpf. kif5Aa and kif5C were detected in the midbrain-hindbrain boundary (MHB) and trigeminal ganglia (TGg). kif5Aa was also detected in the posterior lateral line ganglia (PLLg) while kif5C was more broadly expressed in other tissues. (H, I) Dorsal view of flat mounts at 36hpf. Anterior is to the left, dorsal to the top for A–E. Anterior is to the left for F–I. MHB, midbrain-hindbrain boundary.

Fig. 6

Expression of kif5s at 48hpf and 96hpf. (A,C,E,G,I) Lateral views of whole mount in situs at 48hpf. kif5Aa, kif5Ab, and kif5C were detected throughout the central nervous system while kif5Bb and kif5Bb were ubiquitously expressed. (B,D,F,H,J) Lateral views of whole mount in situs at 96hpf. kif5Aa, kif5Ab, and kif5C continued to be expressed in the central nervous system. kif5Ba and kif5Bb were ubiquitously expressed and showed robust expression in the digestive tract (dt). A=Anterior, P=Posterior, V=Ventral, D=Dorsal. fb, forebrain; mb, midbrain; hb, hindbrain; n, nose; ey, eye.

Fig. 7

(A–E) Expression of kif5s in the retina at 96hpf. White brackets show the expression domain of each individual kif5. (F) Diagram of zebrafish retinal organization. (G) Table summarizes the relative abundance of each individual kif5 across the retinal layers.