Uncoupling neocortical neuron fate and migration via a Let-7-RBX2 axis.

Area of Science:

• Neuroscience
• Developmental Biology
• Molecular Biology

Background:

• Neuronal fate and migration are crucial for central nervous system development.
• In the mammalian neocortex, projection neurons (PNs) exhibit layer-specific positioning based on birth timing.
• The independent or coordinated regulation of neuronal fate and migration remains an open question.

Purpose of the Study:

• To investigate the role of microRNA let-7 in regulating projection neuron migration and positioning.
• To determine the molecular mechanisms by which let-7 influences neuronal positioning.
• To elucidate whether let-7 coordinates neuronal fate and migration.

Main Methods:

• Analysis of let-7's regulatory role in PN migration and positioning.
• Identification of let-7 targets using sequence analysis and functional assays.
• Investigation of RBX2 as a direct target of let-7.
• Assessment of Reelin/DAB1 signaling pathway modulation.
• Experimental manipulation of RBX2 levels in the context of let-7 overexpression.

Main Results:

• Let-7 directly targets RBX2, a component of the E3 ubiquitin ligase CRL5, in the 3'UTR.
• Let-7 reduces RBX2 translation, diminishing CRL5 activity and promoting PN migration.
• Restoring RBX2 levels rescues PN positioning in let-7 overexpressing cells without affecting neuronal fate.
• Let-7 enhances PN migration by increasing speed and duration.

Conclusions:

• Let-7 coordinates neuronal fate specification and migration through distinct molecular pathways.
• The let-7/RBX2 axis is critical for the proper laminar positioning of late-born PNs in the neocortex.
• These findings provide insights into the molecular mechanisms governing neuronal migration and brain development.