Figure 3. Proliferation patterns of Drosophila larval CNS lineages using twin-spot MARCM.

The pan-neuronal driver, GAL4-C155, was used to survey proliferation patterns of Drosophila larval CNS lineages. Twin-spot MARCM clones were induced at a low frequency to simplify the lineage analysis at Drosophila central brain (a-i, l, o and r) and VNC (j, k, m, n, p and q). Like GAL4-OK107, GAL4-C155 can faithfully label two-cell + multi-cellular Nb clones (a, d and g) in MB lineages, which validates the use of GAL4-C155 to probe the overall proliferation patterns of Drosophila CNS lineages. Three types of twin-spot MARCM clones were classified based on the cell number of their associated sister clones. The first class, like MB clones, consists of two-cell + multi-cellular Nb clones (b, e, h, j, m and p) that indicate the familiar production of two progeny by a GMC division. The second class of clones has single-cell + multi-cellular Nb clones (c, f, i, k, n and q) that resemble lineages in which only one daughter cell from the GMC division survives. The lineage identity of [p] and [q] resembles the previously described VNC lineage 13 and lineage 20, respectively ²⁷. The third class is represented by 8-12 cells + large multi-cellular Nb clones (l, o and r) and resemble the recently described PAN lineages in which each transit-amplifying precursor produces multiple GMCs through a limited run of self-renewing asymmetric division.