(A) Distinct intracellular lumen, lined by ectopic brush-border and adjacent terminal web, thus, a typical microvillus inclusion (arrow) inside a PIP5K1C-KO cell. Arrowheads mark lysosomes. (B) Spherical intracellular mass of tangled microvilli associated with ectopic terminal web (arrow) inside a GALNT2-KO cell. Double arrowheads mark enlarged late endocytic organelles. (C) Paracellular, basolateral spot of densely packed microvilli plus associated ectopic terminal web (arrow) in polarized TM9SF4-KO-cell culture. (D) Numerous, slightly bent microvilli facing widened intercellular space (arrows) in polarized ANO8-KO cell culture. (E) Paracellular microvillar spot with adjacent ectopic terminal web (arrow) and associated cell junctions (double arrows) in polarized TMEM110-KO cell culture. Arrowheads mark lysosomes, double arrowhead marks poorly structured late endocytic organelles. (A–E) Scale = 1 µm.