Trk2b plays a role in migration of the zebrafish lateral line primordium (PLLP) and axons.

Lateral line of 72 hpf nTrk2b morphants on the background of SqET33-mi23/SqET33-mi60 cross expressing GFP in the lateral line axons and support cells of neuromasts. A—5-mm-nTrk2b-MO (0.3 pmol); B—nTrk2b-morphant (weak phenotype); C—nTrk2b-morphant (strong phenotype). Neuromasts are indicated by the white arrows and the termini of the lateral line nerves by blue arrows.

Trk2b is required for coordinated migration of the primordium and lateral line axons.

Compound transgenic SqET33-mi23/SqKR21 embryos expressing GFP in the lateral line axons and KillerRed in the lateral line primordium and neuromasts. A–C—5-mm-nTrk2b-MO (0.3 pmol): A—30 hpf, B—36 hpf, C—primordium at 36 hpf; D–F—nTrk2b-morphant with the weak phenotype: D—30 hpf, E—36 hpf, F—primordium at 36 hpf; G–I—nTrk2b-morphant with the strong phenotype: G—36 hpf, H—primordium at 36 hpf, I—lateral line axons at 48 hpf. The primordium leading edges are indicated by white arrows and the termini of the lateral line nerves by blue arrows.

BDNF plays a role in differentiation of the zebrafish lateral line mechanoreceptors.

Lateral line development of 48 hpf zebrafish embryos injected with mRNA encoding different forms of BDNF. A–B—SqET20 transgenic embryo expressing GFP in the mantle cells of neuromasts, mechanoreceptors are stained with DASPEI: A—control, B—mature BDNF mRNA (100 pg); C–D—compound SqET33-mi23/SqET33-mi60 transgenic embryos, expressing GFP in the lateral line nerve and support cells of neuromasts, mechanmoreceptors are stained with DASPEI: C—control, D—mature BDNF mRNA (100 pg); E–G—SqET4 line, expressing GFP in mechanoreceptors of neuromasts: E—control, F—BDNF precursor mRNA (100 pg), G—mature BDNF mRNA (100 pg).