hNPC Division Patterns in Neurosphere Cultures.
(A) A symmetrically-dividing RG completely retracts its processes (B) and divides symmetrically on a plane approximately perpendicular to the RG’s major axis (C) to produce two MCs (D). (E) An asymmetrically-dividing RG does not fully retract its process but does evacuate the process cytoplasm (F) and divides along a plane approximately parallel with the major axis producing a MC and RG daughter (H). (I) RG divisions constitute 37% of all divisions, MCs 63% and neurons 0%. Out of all observed divisions 87% were symmetric and 13% asymmetric. Only RGs divided asymmetrically while both RGs and MCs divided symmetrically. Neurons were only generated through the symmetric division of MCs and never as a direct result of RG division.