Figure 7. Podocalyxin increases cell-cell spacing.

(A) Schematic of optical tweezers experiment. Steps are shown top to bottom. Cells are depicted as green spheres. (B) Quantification of gap widths measured with optical tweezers in control or PODXL^−/− cells. Three distinct subclones are shown (average ± s.e.m., n ≥ 7 cells per subclone, p = 4.39 × 10⁻¹⁷). (C) Top gene ontology terms, (D) differentially expressed genes, and (E) upstream regulators in PODXL^−/− hPSCs, relative to isogenic controls. Data were obtained from three separate experiments (different days), each including 2–3 cell lines of each genotype. (F) Schematic of podocalyxin function. In the absence of podocalyxin, podocytes remain closely apposed and form lateral junctions through which urine cannot be filtered (left). During CLS maturation (right), podocalyxin-coated microvilli (green) form on the apical and lateral surfaces of podocytes. Sialic acid residues (negative charges) on podocalyxin act as an anti-adhesive, separating cell membranes and promoting basal migration of junctional complexes (red) to basal slits, through which urine is filtered. (G) Zoom-in of podocyte cell surfaces in close contact, showing the application of Coulomb’s law. (H) Table of parameters for the estimation of surface area and microvillus charge for each membrane, with (I) accompanying charge calculation for two membranes containing ten podocalyxin molecules per microvillus.