Sec3 exocyst component knockdown inhibits axonal formation and cortical neuronal migration during brain cortex development

• Published in: Journal of neurochemistry 2022-01, Vol.160 (2), p.203-217
• Main Authors: Bustos Plonka, Florentyna, Sosa, Lucas J., Quiroga, Santiago
• Format: Article
• Language: English
• Subjects: Animals; Cell body; Cell culture; Cell Differentiation - physiology; Cell migration; Cell Movement - physiology; Cerebral cortex; Cerebral Cortex - embryology; Cerebral Cortex - metabolism; Dendrites; Differentiation; Electroporation; exocyst complex; Exocytosis; Growth cones; Hippocampus; in utero electroporation; Membrane fusion; Membranes; Mice; Morphology; Neocortex; Neural stem cells; Neurogenesis - physiology; neuronal migration; neuronal polarity; Neurons; Neurons - cytology; Neurons - metabolism; Plasma membranes; Polarity; Polarization; Progenitor cells; Proteins; Sec3; Vesicle fusion; Vesicular Transport Proteins - metabolism
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/jnc.15554

Neurons are the largest known cells, with complex and highly polarized morphologies and consist of a cell body (soma), several dendrites, and a single axon. The establishment of polarity necessitates initial axonal outgrowth in concomitance with the addition of new membrane to the axon's plasmalemma. Axolemmal expansion occurs by exocytosis of plasmalemmal precursor vesicles primarily at the neuronal growth cone membrane. The multiprotein exocyst complex drives spatial location and specificity of vesicle fusion at plasma membrane. However, the specific participation of its different proteins on neuronal differentiation has not been fully established. In the present work we analyzed the role of Sec3, a prominent exocyst complex protein on neuronal differentiation. Using mice hippocampal primary cultures, we determined that Sec3 is expressed in neurons at early stages prior to neuronal polarization. Furthermore, we determined that silencing of Sec3 in mice hippocampal neurons in culture precluded polarization. Moreover, using in utero electroporation experiments, we determined that Sec3 knockdown affected cortical neurons migration and morphology during neocortex formation. Our results demonstrate that the exocyst complex protein Sec3 plays an important role in axon formation in neuronal differentiation and the migration of neuronal progenitors during cortex development. In this paper, we analized the roles of the exocyst complex protein Sec3 on neuronal differentiation and polarization. Our results in hipocampal pyramidal neurons in culture indicated that Sec3 expression is essential in the regulation of initial axonal outgrowth driven by the polarized insertion of IGF‐1 receptors to the plasmalemma of the future axon. Neurons transfected with a shRNA to Sec3 remained arrested in stage 2 of differentiation. Loss of function experiments by in utero electroporation of cortical neurons showed that Sec3 is necessary for cell migration and the polarity switch required for neuronal polarization in situ.