Ear manipulations reveal a critical period for survival and dendritic development at the single‐cell level in Mauthner neurons

Abstract

Second-order sensory neurons are dependent on afferents from the sense organs during a critical period in development for their survival and differentiation. Past research has mostly focused on whole populations of neurons, hampering progress in understanding the mechanisms underlying these critical phases. To move toward a better understanding of the molecular and cellular basis of afferent-dependent neuronal development, we developed a new model to study the effects of ear removal on a single identifiable cell in the hindbrain of a frog, the Mauthner cell. Ear extirpation at various stages of Xenopus laevis development defines a critical period of progressively-reduced dependency of Mauthner cell survival/differentiation on the ear afferents. Furthermore, ear removal results in a progressively decreased reduction in the number of dendritic branches. Conversely, addition of an ear results in an increase in the number of dendritic branches. These results suggest that the duration of innervation and the number of inner ear afferents play a quantitative role in Mauthner cell survival/differentiation, including dendritic development.

Gene, cell, and organ multiplication drives inner ear evolution

“…Sensory neurons depend on the peripheral target for viability (Fritzsch et al, 2016) and cochlear nuclei neurons depend on innervation for viability and differentiation much like other brainstem sensory neurons (Elliott et al, 2015; Rubel and Fritzsch, 2002). Conversely, lack of parts of auditory nuclei has only a limited effect on sensory neuron viability (Maricich et al, 2009) and hair cells depend on innervation only with a long delay (Kersigo and Fritzsch, 2015).…”

Sonic hedgehog antagonists reduce size and alter patterning of the frog inner ear

“…Finally, using a newly developed imaging apparatus (Zarei et al, ), we report how mild phenotypic changes affect the swimming behavior of the tadpole, presumably through affecting the inner ear/Mauthner cell interactions mediating the fast escape response. These insights will guide follow up work assessing how disrupted ear development affects swimming behavior after grafting Vismodegib‐treated ears onto control Xenopus (Elliott et al, ,)…”

Neuroanatomical Tracing Techniques in the Ear: History, State of the Art, and Future Developments

“…Prepare tissue as whole mounts [46] or sections using various embedding techniques, including methacrylate embedding [47]. …”

“…Tissues labeled with either dextran amine or lipophilic dyes or by immunohistochemistry can be subjected to 3-dimensional (3D) reconstruction of the confocal images obtained as described in [46, 48]. …”