Title: Membrane bending proteins affect radial migration in embryonic mouse cortex
Legend: (a) Representation of the Double UP overexpression plasmid construct used in these experiments. Neurons that are transfected with only the Double UP plasmid express mNeon-green (Cre(-) cell). When limited amounts of Cre are co-transfected into about half the neurons, these neurons express mScarlet (mNeon-green is excised) and unlabeled CIP4 or FBP17 (Cre(+) cell). (b) Schematic of experimental design and quantitation procedure. (c, e, g) Representative images of empty Double UP (c), Double UP + CIP4 (e), and Double UP + FBP17 (g) four days after electroporation at E14.5 (E14.5àE18.5). CP= cortical plate, SP/IZ= subplate/intermediate zone, SVZ= subventricular zone, ST= striatum, V= lateral ventricle. Scale bar 100µm. (d, f, h) Dot plots of migration of green and magenta cells. Each dot represents the cumulative mean distance from the top of the cortical plate for all labeled neurons in a single coronal brain section. Connected dots indicate measurements were made in the same coronal section. Black diamonds and bars represent cumulative mean ± SEM. All p values are from a weighted, paired t-test (two-tailed). (d) 7 brains, mNeon: mean 295±45µm, 1316 cells, mScarlet: 310±42µm, 1055 cells. (f) 5 brains, Control: 258±19µm, 987 cells, CIP4: 386±9µm, 999 cells. (h) 9 brains, Control: 213±20µm, 2058 cells, FBP17: 297±21µm, 1724 cells. All values mean±SEM. (b) Created in BioRender. English, L. (2024) BioRender.com/u35d157
Citation: English, L. A., Taylor, R. J., Cameron, C. J., Broker, E. A., & Dent, E. W. (2024). F-BAR proteins CIP4 and FBP17 function in cortical neuron radial migration and process outgrowth. bioRxiv : the preprint server for biology, 2024.10.25.620310. https://doi.org/10.1101/2024.10.25.620310
Abstract: Neurite initiation from newly born neurons is a critical step in neuronal differentiation and migration. Neuronal migration in the developing cortex is accompanied by dynamic extension and retraction of neurites as neurons progress through bipolar and multipolar states. However, there is a relative lack of understanding regarding how the dynamic extension and retraction of neurites is regulated during neuronal migration. In recent work we have shown that CIP4, a member of the F-BAR family of membrane bending proteins, inhibits cortical neurite formation in culture, while family member FBP17 induces premature neurite outgrowth. These results beg the question of how CIP4 and FBP17 function in radial neuron migration and differentiation in vivo, including the timing and manner of neurite extension and retraction. Indeed, the regulation of neurite outgrowth is essential for the transitions between bipolar and multipolar states during radial migration. To examine the effects of modulating expression of CIP4 and FBP17 in vivo, we used in utero electroporation, in combination with our published Double UP technique, to compare knockdown or overexpression cells with control cells within the same mouse tissue of either sex. We show that either knockdown or overexpression of CIP4 and FBP17 results in the marked disruption of radial neuron migration by modulating neuronal morphology and neurite outgrowth, consistent with our findings in culture. Our results demonstrate that the F-BAR proteins CIP4 and FBP17 are essential for proper radial migration in the developing cortex and thus play a key role in cortical development.
Investigator: Erik W. Dent, PhD
About the Lab: The Dent Lab uses molecular, genetic, biochemical and immunocytochemical methods to focus on exploiting high-resolution, live-cell imaging of neurons. All cells in the body constantly undergo dynamic changes in shape and require rapid changes in their entire array of proteins, lipids and nucleic acids. Neurons are somewhat unique in that they often form very polarized structures, with both highly arborized dendrites and a long axon that undergo extensive branching and arborization as well. The lab specializes in total internal reflection fluorescence microscopy (TIRFM) to study the development and plasticity of neurons in culture. We also use widefield and scanning confocal microscopy, and are beginning to implement super-resolution microscopy (STED and SIM) for our studies.