Calcium Signaling in the Cerebellar Radial Glia and Its Association with Morphological Changes during Zebrafish Development

Abstract

Radial glial cells are a distinct non-neuronal cell type that, during development, span the entire width of the brain walls of the ventricular system. They play a central role in the origin and placement of neurons, since their processes form structural scaffolds that guide and facilitate neuronal migration. Furthermore, glutamatergic signaling in the radial glia of the adult cerebellum (i.e., Bergmann glia), is crucial for precise motor coordination. Radial glial cells exhibit spontaneous calcium activity and functional coupling spread calcium waves. However, the origin of calcium activity in relation to the ontogeny of cerebellar radial glia has not been widely explored, and many questions remain unanswered regarding the role of radial glia in brain development in health and disease. In this study we used a combination of whole mount immunofluorescence and calcium imaging in transgenic (gfap-GCaMP6s) zebrafish to determine how development of calcium activity is related to morphological changes of the cerebellum. We found that the morphological changes in cerebellar radial glia are quite dynamic; the cells are remarkably larger and more elaborate in their soma size, process length and numbers after 7 days post fertilization. Spontaneous calcium events were scarce during the first 3 days of development and calcium waves appeared on day 5, which is associated with the onset of more complex morphologies of radial glia. Blockage of gap junction coupling inhibited the propagation of calcium waves, but not basal local calcium activity. This work establishes crucial clues in radial glia organization, morphology and calcium signaling during development and provides insight into its role in complex behavioral paradigms.

A Mini-Review Regarding the Modalities to Study Neurodevelopmental Disorders-Like Impairments in Zebrafish—Focussing on Neurobehavioural and Psychological Responses

“…Moreover, in Balh et al [ 69 ] study the neural circuits changes were evaluated using electrode-based imaging and calcium signaling. Calcium imaging of the zebrafish brain is yet another innovative technique assessing neural activity, recently described in a study regarding the cerebellar radial glia developmental patterns in zebrafish larvae by correlation to morphodynamic changes [ 69 ].…”

“…Moreover, in Balh et al [ 69 ] study the neural circuits changes were evaluated using electrode-based imaging and calcium signaling. Calcium imaging of the zebrafish brain is yet another innovative technique assessing neural activity, recently described in a study regarding the cerebellar radial glia developmental patterns in zebrafish larvae by correlation to morphodynamic changes [ 69 ]. Furthermore, Zylberthal and Bianco [ 70 ] reported the calcium imaging technique combined with mechanistic network modelling in zebrafish larvae to evaluate spatial and temporal network interactions in the zebrafish optic tectum in response to visual stimuli (prey-catching responses).…”

Constitutive Neurogenesis and Neuronal Plasticity in the Adult Cerebellum and Brainstem of Rainbow Trout, Oncorhynchus mykiss

“…RG cells play a central role in the origin and placement of neurons [ 15 ] because their processes form structural scaffolds that guide and facilitate neuronal migration. In addition, glutamatergic signaling in the RG of the adult cerebellum (Bergmann glia) of zebrafish is critical for precise motor coordination [ 16 ]. Studies in zebrafish have shown that RG cells exhibit spontaneous calcium activity, and functional interaction propagates calcium waves.…”

“…Studies in zebrafish have shown that RG cells exhibit spontaneous calcium activity, and functional interaction propagates calcium waves. However, the origin of calcium activity in relation to the ontogeny of cerebellar radial glia is just beginning to be explored, and results in zebrafish have elucidated important aspects of RG organization, morphology, and calcium signaling, emphasizing its role in complex behavioral paradigms [ 16 ].…”

Zebrafish as a Model for Neurological Disorders

“…Moreover, the cross-reactivity of several antibodies directed against mammalian proteins also enabled the precise characterization of the neurogenic cells in the preoptic region of the adult zebrafish hypothalamus, highlighting the strong similarities, but also the differences in the neurogenic niches between mammals and fish. Pereida-Jaramillo et al [9] used transgenic fluorescent calcium sensors to visualize in vivo the transient calcium uptakes underlying the depolarization of neurons, and the membrane currents of glial cells whose function remains poorly understood. First, a calcium sensor expressed under the control of the glial gfap promoter was instrumental in demonstrating for the first time that rostro-caudal calcium waves occur in cerebellar Bergmann glial cells starting from 5 dpf.…”