Fig. 3.

Actin cytoskeleton gain of function. a. Representative confocal images of iPSC derived MGE progenitors 48 h after plating on Matrigel. (Red–βIII-tubulin; green—Actin, phalloidin). Filopodia are indicated by arrows and lamellipodia by arrowheads. Scale bar, 10 μm. b. Cumulative density curves of branch length in MGE progenitors (48 h after plating) derived from the null (grey) and CHRFAM7A KI (orange) lines. Statistical comparison was performed using the two-sample Kolmogorov–Smirnov test, not significant. c. Actin lattice change over time depicted in consecutive frames of live actin video recording in MGE progenitors derived from the null and CHRFAM7A KI lines (arrows: area of interest over time). d. Live actin imaging of MGE progenitors: representative image of growth cone surface undulations depicted by overlaying colour coded frames (Supplementary Video 1–6). e. Cell surface topology dynamic changes over time are quantified as variance in shape index in null and CHRFAM7A KI isogenic iPSC derived MGE progenitors (n = 3; independent two-tailed-T-test, the horizontal lines represent median and IQR). f. Activation of small GTPases in response to Matrigel in null (grey) and CHRFAM7A KI isogenic (orange) MGE progenitors detected by G-LISA and Rac1/CDC42 ratio (n = 3; independent two-tailed T-test. Multiple testing correction was performed by Bonferroni). g. Representative confocal images demonstrating differential staining of lamellipodia (by lamellipodin, LPD) and filopodia (by VASP) in MGE progenitors derived from the two lines.