Article Figures & Data
Figures
- Figure 1.
Neuronal diversity in the mammalian spinal cord. A, Morphogen gradients acting along the dorsoventral axis of the neural tube generate progenitor domains that give rise to the major neuronal classes in the spinal cord, which are further subdivided into more diverse subtypes. RP, roof plate; FP, floor plate; Shh, Sonic hedgehog; Bmp, bone morphogenetic proteins. B, Along the rostrocaudal axis of the spinal cord, Hox proteins further diversify MNs. For example, at rostral levels of the spinal cord (cervical–brachial), Hox5 proteins control the development of phrenic (PMC) neurons while a network of ∼20 Hox proteins establishes limb-innervating (LMC) MN identities. C, Distinct subsets of cholinergic V0 neurons target either LMC or PMC neurons. The mechanisms that distinguish locomotor (V0C-L) from respiratory (V0C-R) V0C neurons and dictate their selective targeting are currently unknown.
- Figure 2.
Terminal selectors of MN identity in C. elegans. A, Eight cardinal classes of MNs are in the C. elegans ventral nerve cord, six are cholinergic, and two are GABAergic. Seven classes (DA, DB, VA, VB, AS, DD, VD) control locomotion, whereas VC neurons control egg laying. B, UNC-3/EBF functions as a terminal selector of cholinergic MN identity in five cholinergic classes (DA, DB, VA, VB, AS). UNC-3/EBF collaborates with LIN-39/HOX to coactivate scores of MN terminal identity genes. The DNA-binding site of UNC-3 is adapted from Li et al. (2020). C, UNC-30/PITX functions as a terminal selector of GABAergic MN identity in two GABAergic classes (DD, VD). UNC-30/PITX collaborates with LIN-39/HOX to coactivate scores of MN terminal identity genes (Feng et al., 2020). The DNA-binding site of UNC-30 is adapted from Cinar et al. (2005).
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- Article
- Abstract
- Introduction
- Early Steps in Vertebrate MN Specification and Connectivity
- Conserved Mechanisms of MN Maintenance
- Functional Organization of Motor Circuits in Vertebrates
- Distinct Spinal Interneuron Functions in Locomotor and Respiratory Control in Mammals
- Mechanisms of Motor Circuit Wiring and Synaptic Specificity in Vertebrates
- Mechanisms of Motor Circuit Wiring and Synaptic Specificity in Invertebrates
- Motor Circuits across Evolution
- Closing Remarks
- Footnotes
- References
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