KLC4 shapes axon arbors during development and mediates adult behavior

Abstract

Development of elaborate and polarized neuronal morphology requires precisely regulated transport of cellular cargos by motor proteins such as kinesin-1. Kinesin-1 has numerous cellular cargos which must be delivered to unique neuronal compartments. The process by which this motor selectively transports and delivers cargo to regulate neuronal morphogenesis is poorly understood, although the cargo-binding kinesin light chain (KLC) subunits contribute to specificity. Our work implicates one such subunit, KLC4, as an essential regulator of axon branching and arborization pattern of sensory neurons during development. Using live imaging approaches in klc4 mutant zebrafish, we show that KLC4 is required for stabilization of nascent axon branches, proper microtubule (MT) dynamics, and endosomal transport. Furthermore, KLC4 is required for proper tiling of peripheral axon arbors: in klc4 mutants, peripheral axons showed abnormal fasciculation, a behavior characteristic of central axons. This result suggests that KLC4 patterns axonal compartments and helps establish molecular differences between central and peripheral axons. Finally, we find that klc4 mutant larva are hypersensitive to touch and adults show anxiety-like behavior in a novel tank test, implicating klc4 as a new gene involved in stress response circuits.

Spatiotemporal dynamics of sensory neuron and Merkel-cell remodeling are decoupled during epidermal homeostasis

“…Future studies with finer temporal precision are needed to test whether these protrusions aid in recruiting afferent terminals to form kylikes. Live-cell imaging of zebrafish embryos has also been used to study development of peripheral axon arbors in Rohon Beard cells, a population of gentle-touch neurons that transiently exist during development and are responsible for initiating escape responses (Clarke et al, 1984; Haynes et al, 2022). Recent work has shown that peripheral arborization of Rohon Beard cells depends on kinesin light chain 4 (Haynes et al, 2022), which regulates binding between cellular cargo and kinesin motors (Morfini et al, 2016).…”

“…Live-cell imaging of zebrafish embryos has also been used to study development of peripheral axon arbors in Rohon Beard cells, a population of gentle-touch neurons that transiently exist during development and are responsible for initiating escape responses (Clarke et al, 1984; Haynes et al, 2022). Recent work has shown that peripheral arborization of Rohon Beard cells depends on kinesin light chain 4 (Haynes et al, 2022), which regulates binding between cellular cargo and kinesin motors (Morfini et al, 2016). In the absence of KLC4, new branches initiate but do not properly separate from sister branches, which ultimately results in abnormal axon fasciculation (Haynes et al, 2022).…”

“…Indeed, both Aβ afferents and Merkel cells express Bmpr1a and Bmpr2, which mediate BMP4 signaling (Miyazono et al, 2010). The tangled morphology of afferents in animals lacking Merkel cells also resembled the phenotype of peripheral axons in zebrafish that harbor mutations in kinesin light chain 4; indeed, kinesin light chain 4 is expressed in sensory neurons so it is possible that this cargo transport pathway gets disrupted or overloaded since terminal branches are not able to fully mature in the absence of their target cells (Haynes et al, 2022). Furthermore, Merkel-cell afferents express the neurotrophin receptor NTrk3 (TrkC) and NT3 is necessary for postnatal maintenance of both Merkel cells and their axons (Airaksinen et al, 1996) and could govern the ongoing plasticity that we observed.…”

“…Recent work has shown that peripheral arborization of Rohon Beard cells depends on kinesin light chain 4 (Haynes et al, 2022), which regulates binding between cellular cargo and kinesin motors (Morfini et al, 2016). In the absence of KLC4, new branches initiate but do not properly separate from sister branches, which ultimately results in abnormal axon fasciculation (Haynes et al, 2022). This disorganized phenotype is reminiscent of the hyperbranched and tangled afferents from mice lacking Merkel cells.…”

How neurons maintain their axons long-term: an integrated view of axon biology and pathology

“…(iii) KIFBP mutations are disruptive to axonal MT bundles and cause Goldberg-Shprintzen syndrome (‘GOSHS’ in Supplementary Table S1 A ; Lyons et al, 2008 ; Hirst et al, 2017 ; Chang et al, 2019 ). (iv) KLC mutations are linked to HSP/SPG and SPOAN ( Supplementary Table S1 A ; Bayrakli et al, 2015 ; Melo et al, 2015 ; Fu et al, 2021 ; Gümüşderelioğlu et al, 2023 ) and to excessive axon branching in zebrafish ( Haynes et al, 2022 ).…”