Biology subjects

Masino, M. A.

Publications and source records attributed to Masino, M. A..

3 recordsLinked to original sources

bioRxiv2025

Refinement of locomotor activity is developmentally regulated by dopaminergic signaling in larval zebrafish

The refinement of gross motor skills, such as locomotion, during development is conserved across vertebrate species. Our previous work demonstrated, in larval zebrafish, that dopaminergic signaling through the dopamine D2-like family of receptors, specifically the dopamine 4 receptor subtype, was necessary for the developmental transformation of behaviorally relevant locomotor activity from an immature to a mature pattern between 3- and 4-days post-fertilization. In this study, we used a complement of tools, including electrophysiology, pharmacology, in vivo calcium imaging, liquid chromatography-mass spectrometry, and quantitative reverse transcription polymerase chain reaction to characterize the functional and molecular mechanisms responsible for this dopaminergic-mediated refinement of spinal locomotor activity. The results demonstrate that the dopamine 4 receptor subtype is both present and functional in, at least, a subset of immature larvae. Further, gene expression of all D2-like receptor subtypes, levels of dopamine, and activity of diencephalic dopaminergic neurons are significantly greater in mature larvae compared to immature larvae. The integration of these results provides evidence for the developmental role of dopaminergic signaling, specifically the dopamine receptor 4 subtype, in the refinement of locomotor activity in vertebrates. Significance StatementThroughout life, all vertebrates acquire and improve gross motor skills. This is particularly evident in the locomotor system where motor output is initially coarse and becomes progressively more refined during development. Previously, we demonstrated that dopaminergic signaling was a factor in the developmental refinement of locomotor activity. However, an understanding of the molecular and functional mechanisms underlying the dopaminergic-mediated refinement of spinal locomotor activity remains elusive. This study demonstrates, in larval zebrafish, that increased expression of all D2-like dopamine receptor subtypes, levels of dopamine, and activity of diencephalic dopaminergic neurons correlate with the refinement of locomotor activity.

neuroscience↗

bioRxiv2021

V3 Interneurons Regulate Locomotor Vigor by Recruitment of Spinal Motor Neurons During Fictive Swimming in Larval Zebrafish

Survival for vertebrate animals is dependent on the ability to successfully find food, locate a mate, and avoid predation. Each of these behaviors requires motor control, which is set by a combination of kinematic properties. For example, the frequency and amplitude of motor output combine in a multiplicative manner to determine features of locomotion such as distance traveled, speed, force (thrust), and vigor. Although there is a good understanding of how different populations of excitatory spinal interneurons establish locomotor frequency, there is a less thorough mechanistic understanding for how locomotor amplitude is established. Recent evidence indicates that locomotor amplitude is regulated in part by a subset of functionally and morphologically distinct V2a excitatory spinal interneurons (type II, non-bursting) in larval and adult zebrafish. Here we provide direct evidence, for the first time, that most V3 interneurons (V3-INs), which are a developmentally and genetically defined population of ventromedial glutamatergic spinal neurons, are active during fictive swimming. We also show that elimination of the spinal V3-IN population reduces the proportion of active MNs during fictive swimming but does not alter the range of locomotor frequencies produced. These data are consistent with V3-INs providing excitatory drive to spinal motor neurons and contributing to the production of locomotor amplitude, but not frequency, during swimming in larval zebrafish. SIGNIFICANCE STATEMENTCurrently, there is a limited understanding about the cellular and spinal network properties that produce locomotor amplitude, defined as limb displacement in limbed animals or tail-bend in non-limbed animals during locomotion. Here we show, directly for the first time in a vertebrate, that V3 interneurons (V3-INs) in zebrafish larvae are active during in vivo fictive locomotion, and that targeted ablation of the spinal V3-IN population reduces the proportion of active motoneurons during fictive swimming. Importantly, ablation of V3-INs does not affect locomotor frequency (speed), which clarifies their role in motor control rather than rhythm generation. Thus, we propose that the V3-IN population is a source of excitation in the vertebrate locomotor neural circuitry that regulates locomotor amplitude independently of speed.

neuroscience↗

bioRxiv2019

L-type voltage-gated calcium channel agonists improve hearing loss and modify ribbon synapse morphology in the zebrafish model of Usher Syndrome Type 1

Usher Syndrome (USH) is the most common cause of human deaf/blindness. The zebrafish myo7aa-/- mutant, faithfully models USH1; homozygous zebrafish are deaf and exhibit circular swimming. We hypothesized that hair cell morphology would differ in myo7aa-/- mutants compared to wild type. We also tested the hypothesis that agonists of L-type voltage-gated calcium channels would alter ribbon synapse morphology and behavior of zebrafish myo7aa-/- mutants. We discovered that myo7aa-/- zebrafish have fewer glutamatergic vesicles tethered to hair cell ribbon synapses, yet maintain a comparable ribbon area. We identified that myo7aa-/- mutants have fewer total active hair cells, fewer total CTBP2 expressing puncta, and an altered distribution of CTBP2 puncta compared to wildtype. We also identified that myo7aa-/- mutants have fewer active post-synaptic cells and fewer total MAGUK puncta, compared to wildtype. Behaviorally, myo7aa-/- mutant fish have abnormal swimming as measured by larger absolute smooth orientations and have little to no acoustic startle. Treatment with L-type voltage-gated calcium channel agonists altered the abnormal cell and behavioral phenotypes toward wildtype. Our data supports that L-type voltage-gated calcium channel agonists induce morphological changes at the ribbon synapse--in both the number of tethered vesicles and the distribution of CTBP2 puncta, shifts swimming behavior towards wildtype swimming and improves acoustic startle response. Summary StatementWe identified that the hair cell biology and behavior of the myo7aa-/- mutant differs from wildtype and this difference can be rescued using L-type voltage-gated calcium channel agonists.

neuroscience↗