Figure 1.

Nutritional Signals Control the Three Phases of NE Development

In all figures of the article, images are projections of several confocal sections (except if stated otherwise).

(A) Schematic drawings representing lateral views of a larval CNS from early L1 to late L3. Central brain and nerve cord neuroblasts (NBs) are represented as gray circles. In the OL, medulla NBs are represented as red circles, and neuroepithelial cells (NEs) are represented as green rectangles. Medulla NBs are smaller and also more densely packed than their central brain counterparts and form a characteristic horseshoe-shaped strip adjacent to the medial edge of the NE. 3D axis are presented as A-P, anterior-posterior; D-V, dorsal-ventral; M-L, medial-lateral.

(B–E) Pictures show larval OL during the three periods of medulla development and a frontal view of a pupal OL (130 hr). The NE is stained by E-Cadherin (E-Cad; green), NBs are marked with Mira (red), and mitotic cells are marked with PH3 (white). The dotted yellow line delineates the medulla (NE and NBs). (B) Phase 0: inactive NE. (C) Phase 1: expansion. (D) Phase 2: NE → NB conversion. (E) At midpupae, no more NE cells and NBs are detected.

(F) The NE of larvae submitted to NR conditions for 48 hr from hatching (phase 0) never initiate proliferation.

(G) The NE of larvae starved from 48 hr ALH (phase 1) to 96 hr arrests proliferation (no PH3⁺ NE cells) and does not undergo NB conversion. Yellow arrows indicate central brain NBs that are still dividing in these conditions.

(H) NR during phase 2 (from 60 to 96 hr) impacts neither on neural proliferation nor on NE → NB conversion.

(I) Schematic representation of the results obtained from the NR experiments during the three periods of medulla development (F–H).

See also Figure S1.