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Caenorhabditis elegans flamingo cadherin fmi-1 regulates GABAergic neuronal development
Elvis Huarcaya Najarro1, Lianna Wong, Mei Zhen
1Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045, USA.
Abstract:
In a genetic screen for regulators of synaptic morphology, we identified the single Caenorhabditis elegans flamingo-like cadherin fmi-1. The fmi-1 mutants exhibit defective axon pathfinding, reduced synapse number, aberrant synapse size and morphology, as well as an abnormal accumulation of synaptic vesicles at nonsynaptic regions. Although FMI-1 is primarily expressed in the nervous system, it is not expressed in the ventral D-type (VD) GABAergic motorneurons, which are defective in fmi-1 mutants. The axon and synaptic defects of VD neurons could be rescued when fmi-1 was expressed exclusively in non-VD neighboring neurons, suggesting a cell nonautonomous action of FMI-1. FMI-1 protein that lacked its intracellular domain still retained its ability to rescue the vesicle accumulation defects of GABAergic motorneurons, indicating that the extracellular domain was sufficient for this function of FMI-1 in GABAergic neuromuscular junction development. Mutations in cdh-4, a Fat-like cadherin, cause similar defects in GABAergic motorneurons. The cdh-4 is expressed by the VD neurons and seems to function in the same genetic pathway as fmi-1 to regulate GABAergic neuron development. Thus, fmi-1 and cdh-4 cadherins might act together to regulate synapse development and axon pathfinding.
Insights
The study identifies flamingo cadherin FMI-1 as crucial for Caenorhabditis elegans neuron development. FMI-1 acts non-autonomously, with its extracellular domain regulating synaptic vesicle distribution and working with CDH-4.
Area of Science:
- Neuroscience
- Developmental Biology
- Genetics
Background:
- Synaptic morphology and function are critical for nervous system operation.
- Cadherins are cell adhesion molecules involved in various developmental processes.
- Regulators of synaptic development are essential for understanding neural circuit formation.
Purpose of the Study:
- To identify novel regulators of synaptic morphology in Caenorhabditis elegans.
- To elucidate the function and mechanism of the flamingo-like cadherin FMI-1 in neuronal development.
- To investigate the interaction between FMI-1 and other cadherins, such as CDH-4, in GABAergic neuron development.
Main Methods:
- Genetic screening in Caenorhabditis elegans to identify mutants with defects in synaptic morphology.
- Analysis of axon pathfinding, synapse number, size, and morphology in FMI-1 mutants.
- Investigating cell-autonomous versus cell non-autonomous functions of FMI-1 through targeted expression.
- Assessing the role of FMI-1's intracellular and extracellular domains in rescuing synaptic defects.
- Comparing FMI-1 phenotypes with those of CDH-4 mutants and analyzing their genetic interactions.
Main Results:
- The Caenorhabditis elegans flamingo-like cadherin FMI-1 was identified as a regulator of synaptic morphology.
- FMI-1 mutants displayed defects in axon pathfinding, synapse number, size, and vesicle accumulation.
- FMI-1 functions cell non-autonomously, with its extracellular domain sufficient for rescuing GABAergic motor neuron defects.
- Mutations in the Fat-like cadherin CDH-4 caused similar defects and appear to function in the same pathway as FMI-1.
- FMI-1 and CDH-4 may act together to regulate synapse development and axon pathfinding.
Conclusions:
- FMI-1 is a critical regulator of axon pathfinding and synapse development in Caenorhabditis elegans.
- The extracellular domain of FMI-1 plays a key role in regulating synaptic vesicle distribution at the neuromuscular junction.
- FMI-1 and CDH-4 function in a common genetic pathway to control GABAergic neuron development, highlighting a collaborative role for these cadherins.
