Timothy M. Gomez, PhD – Slide of the Week

Timothy M. Gomez, PhD – Slide of the Week

Title: Substrata Elasticity Influences Neuronal Morphogenesis in a Neuronal-type Specific Manner in Two-Dimensional Cultures

Legend: (A–D) Low-magnification confocal images of iPSC-derived hMN neurospheres cultured on soft (0.5 kPa), intermediate (4 kPa), and rigid (25 kPa and 50 kPa) LN-coated PAA gels, and immunolabeled for acetylated tubulin (magenta) and F-actin (phalloidin, green). Note longer processes on rigid substrata compared with soft and intermediate. (E) hMN neurite lengths were measured on increasing PAA gel rigidities (0.5–125 kPa). Due to the density of neurites extending from neurospheres, the ten longest neurites were measured for this analysis and compared between experimental groups. hMNs extend greater neurite lengths on progressively more rigid substrata up to 25 kPa and fitted linear regression lines showed strong goodness of fit (R2 = 0.8952) and are significantly more sloped (p < 0.001) compared with hFB neurons (below). nR40 neurites from n = 4 experiments from n = 2 differentiations for each condition.

Citation: Nichol, R. H., 4th, Catlett, T. S., Onesto, M. M., Hollender, D., & Gómez, T. M. (2019). Environmental Elasticity Regulates Cell-type Specific RHOA Signaling and Neuritogenesis of Human Neurons. Stem cell reports, 13(6), 1006–1021. https://doi.org/10.1016/j.stemcr.2019.10.008

Abstract: The microenvironment of developing neurons is a dynamic landscape of both chemical and mechanical cues that regulate cell proliferation, differentiation, migration, and axon extension. While the regulatory roles of chemical ligands in neuronal morphogenesis have been described, little is known about how mechanical forces influence neurite development. Here, we tested how substratum elasticity regulates neurite development of human forebrain (hFB) neurons and human motor neurons (hMNs), two populations of neurons that naturally extend axons into distinct elastic environments. Using polyacrylamide and collagen hydrogels of varying compliance, we find that hMNs preferred rigid conditions that approximate the elasticity of muscle, whereas hFB neurons preferred softer conditions that approximate brain tissue elasticity. More stable leading-edge protrusions, increased peripheral adhesions, and elevated RHOA signaling of hMN growth cones contributed to faster neurite outgrowth on rigid substrata. Our data suggest that RHOA balances contractile and adhesive forces in response to substratum elasticity.

About the Lab: The Gomez laboratory focuses on the intracellular mechanisms that regulate growth cone motility and behavior. Growth cones are sensory-motor specializations at the tips of all growing axons and dendrites that detect and transduce extracellular cues into guided outgrowth. Great advances have been made in recent years in our understanding of the factors that contribute to guided axon extension. Many new classes of ligands and their receptors have been discovered and we are beginning to appreciate how growth cones integrate multiple extracellular stimuli and convert those signals into stereotyped behaviors.

Investigator: Timothy M. Gomez, PhD

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