Fig. 5: Twine and PLPs.

a Plot showing the length of twines observed with respect to corresponding location of emergence of twines and PLPs along the normalized cell length. Backdrop shows a cell forming multiple lateral protrusions. b Polar histogram of angle formed by twine or PLP engagement axis and a tangent to cell body (n = 84 for PLP and 123 for twines). PLPs are oriented mostly perpendicularly to cell body. c Four fiber network designs were created to interrogate cell shape (AR: aspect ratio and Circ.: circularity) driven number density of (i) twines, and (ii) PLP formation ((number of PLPs/number of attached twines) *100). Elongated cells of high aspect ratios and small circularities form maximum number of twines/cell on anisotropic and hexagonal networks, while only anisotropic networks facilitate formation of PLPs. Data are analyzed from 23 randomly selected videos for each category. d Design of fiber networks (i) crosshatch interfaced with aligned, and (ii) crosshatch networks on either side of aligned networks to demonstrate that 3D-PLPs are formed only in aligned networks (yellow arrows). On crosshatch networks cells form classicly described protrusions mostly along existing fibers. Scale bar: a 10 µm, c 10 µm, d (i) 20 µm, (ii) 50 µm.