Biology subjects

Bello-Rojas, S.

Publications and source records attributed to Bello-Rojas, S..

3 recordsLinked to original sources

bioRxiv2026

Spinal V2a neurons support locomotor propagation via long-range connectivity

The spinal cord contains a diverse set of neurons whose activity is vital for motor control. Despite the importance of these spinal interneurons in network models of locomotion, their circuitry remains poorly understood. We quantified the synaptic output of V2a (vsx2+) interneurons, a glutamatergic population implicated in control of locomotor speed, rhythm generation, and recovery from injury, using the larval zebrafish. Surprisingly, we found that the majority of monosynaptic output from V2a neurons occurs onto motor and premotor targets at long ranges, in contrast to models that posit V2a neurons as the source of recurrent local excitation. Focal loss of V2a neurons impairs long-range propagation of locomotor output, but not local rhythm generation, in accordance with their long-range connectivity. Our results position V2a neurons as major mediators of locomotor propagation and long-range coordination in the spinal cord.

neuroscience↗

bioRxiv2022

Clonally related, Notch-differentiated spinal neurons integrate into distinct circuits

Shared lineage has diverse effects on patterns of neuronal connectivity. In mammalian cortex, excitatory sister neurons assemble into shared microcircuits, whereas throughout the Drosophila nervous system, Notch-differentiated sister neurons diverge into distinct circuits. Notch-differentiated sister neurons have been observed in vertebrate spinal cord and cerebellum, but whether they integrate into shared or distinct circuits remains unknown. Here we evaluate the connectivity between sister V2a/b neurons in the zebrafish spinal cord. Using an in vivo labeling approach, we identified pairs of sister V2a/b neurons born from individual Vsx1+ progenitors and observed that they have similar axonal trajectories and proximal somata. However, paired whole-cell electrophysiology and optogenetics revealed that sister V2a/b neurons receive input from distinct presynaptic sources, do not communicate with each other, and connect to largely distinct targets. These results resemble the divergent connectivity in Drosophila and represent the first evidence of Notch-differentiated circuit integration in a vertebrate system.

neuroscience↗

bioRxiv2019

Central and peripheral innervation patterns of defined axial motor units in larval zebrafish

Spinal motor neurons and the peripheral muscle fibers they innervate form discrete motor units that execute movements of varying force and speed. Subsets of spinal motor neurons also exhibit axon collaterals that influence motor output centrally. Here, we have used in vivo imaging to anatomically characterize the central and peripheral innervation patterns of axial motor units in larval zebrafish. Using early born primary motor neurons and their division of epaxial and hypaxial muscle into four distinct quadrants as a reference, we define three distinct types of later born secondary motor units. The largest are m-type units, which innervate deeper fast-twitch muscle fibers via medial nerves. Next in size are ms-type secondaries, which innervate superficial fast-twitch and slow fibers via medial and septal nerves, followed by s-type units, which exclusively innervate superficial slow muscle fibers via septal nerves. All types of secondaries innervate up to four axial quadrants. Central axon collaterals are found in subsets of primaries based on soma position and predominantly in secondary fast-twitch units (m, ms) with increasing likelihood based on number of quadrants innervated. Collaterals are labeled by synaptophysin-tagged fluorescent proteins, but not PSD95, consistent with their output function. Also, PSD95 dendrite labeling reveals that larger motor units receive more excitatory synaptic input. Collaterals are largely restricted to the neuropil, however perisomatic connections are observed between motor units. These observations suggest that recurrent interactions are dominated by motor neurons recruited during stronger movements and set the stage for functional investigations of recurrent motor circuitry in larval zebrafish.

neuroscience↗