Steroid hormone induction of temporal gene expression in Drosophila brain neuroblasts generates neuronal and glial diversity
- Howard Hughes Medical Institute, University of Oregon, United States
Figures
Figure 1 with 2 supplements
Identification of temporally expressed proteins in larval type II neuroblasts.
(A–E) Cas and Svp are expressed from 24–36 hr (A,C,E) but not at 48 hr (B,D,E). Neuroblasts, outlined. (F–K) Early factors. Chinmo, Imp, and Lin-28:GFP (Lin-28) are detected in neuroblasts at 48 hr …
Figure 1—figure supplement 1
TU-tagging to identify temporally expressed genes in type II neuroblasts and their progeny.
(A) Type II neuroblast lineage schematic, showing young or old neuroblast progeny markers. (B) Expression of HA:UPRT specifically in type II neuroblasts and their progeny. Scale bar, 50 μm. (C) Heat …
Figure 1—figure supplement 2
Broad-Z1 but not Broad-Z3 is expressed in type II neuroblasts.
(A) Broad-Z1 (magenta) is detected in type II neuroblasts (dashed circle) at 96 hr. (B) Broad-Z3 (magenta) is not detected in type II neuroblasts (dashed circle) at 96 hr. In all panels, type II …
Figure 2
Ecdysone hormone is required for the early-to-late temporal factor transition.
(A–E) Control ecdts/deficiency larvae at 18°C show normal temporal factor expression in type II neuroblasts (circled): the early factors Chinmo and Imp are off at 72 hr (A–B) and the late factors …
Figure 3
Ecdysone hormone activates neuroblast expression of Chinmo and Broad in isolated brain cultures.
(A–B) Isolated larval brains cultured with added 20-hydroxy-ecdysone (+20 HE) from 48–72 hr show normal down-regulation of the early factor Chinmo (A) and activation of the late factor Broad (B). (C–…
Figure 4 with 1 supplement
Ecdysone receptor expression and function.
(A–B) EcR-B1 is first detected at ~56 hr in most type II neuroblasts. (C–F) EcR-B1 expression is ecdysone-independent. (C–D) EcR-B1 is activated normally in ecdts mutants at both permissive (18°C) …
Figure 4—figure supplement 1
Ecdysone receptor isoform expression in type II neuroblasts.
(A) EcR-B1 (magenta) is detected in type II neuroblasts (dashed circle) at 96 hr; n > 10. See also Figure 4A,B. (B) EcR-A (magenta) is not detected in type II neuroblasts (dashed circle) at 96 hr; n …
Figure 5 with 1 supplement
Seven-up activates expression of the Ecdysone receptor in type II neuroblasts.
(A–F) svp mutant MARCM clones (GFP+, green and outlined) induced at 0–4 hr and assayed at 96 hr for the indicated factors. (G) Quantification (red, svp mutant clone; black, wild type UAS-FLP …
Figure 5—figure supplement 1
Cas is not required to activate Svp expression, and Svp is not required to terminate Cas expression.
cas mutant clones induced during embryogenesis show normal Seven-up expression at 36 hr. svp mutant clones induced during 0–4 hr show normal loss of Cas expression at 72 hr. In all panels, type II …
Figure 6 with 1 supplement
Syncrip and Imp function downstream of the Ecdysone receptor in type II neuroblasts.
(A–C) Imp mutants (impG0072 / impG0072) and Syncrip mutants (Syncrip f03775/ deficiency) show normal expression of EcR in type II neuroblasts: off at 48 hr and on at 72 hr. (D) Imp mutants (ImpG0072 …
Figure 6—figure supplement 1
Chinmo and Broad have mutually exclusive expression in neuroblasts and neurons.
(A) Chinmo is expressed in type II neuroblasts (dashed circle) and adjacent neuronal progeny at 48 hr, whereas Broad is not detected. (B) Broad is expressed in type II neuroblasts (dashed circle) …
Figure 7
Late temporal transcription factors specify neuronal and glial identity.
(A,B) Wild type or (C,D) EcRDN brains at 0 hr after puparium formation. The inset shows GFP+ cells permanently marking the type II neuroblast lineage (wor-gal4 ase-gal80 UAS-FLP …
Figure 8 with 1 supplement
Ecdysone is required for early to late temporal factor transition in type I neuroblasts.
(A–C) Control brains (ecd-ts/deficiency at 18°C) at the indicated timepoint. (A–C) Normal down-regulation of the early factor Chinmo and activation of the late factors Broad and E93. (E–G) …
Figure 8—figure supplement 1
Syncrip is expressed in a subset of central brain neuroblasts at 36 hr and 48 hr.
(A,B) Syncrip is detected in ~10 central brain neuroblasts at 36 hr and 48 hr. Maximum intensity projection of entire brain lobes. Anterior up. (C) Quantification.
Figure 9
Model showing hormonal regulation of early to late temporal transitions in central brain larval neuroblasts.
Summary of regulatory interactions driving larval neuroblast early-to-late temporal factor expression. Arrows indicate positive regulation; ‘T’ indicates negative regulation; dashed bars indicate …
Videos
Video 1
Explanted larval brain cultured in vitro from 48–72 hr with added 20-hydroxy-ecdysone.
Two type II neuroblasts are shown expressing wor-gal4 ase-gal80 UAS-myr:GFP (see Materials and methods). Still panels from video shown in Figure 3E, and cell cycle times quantified in Figure 3G.
Video 2
Explanted larval brain cultured in vitro from 48–72 hr without 20-hydroxy-ecdysone.
Two type II neuroblasts are shown expressing wor-gal4 ase-gal80 UAS-myr:GFP (see Materials and methods). Still panels from video shown in Figure 3F, and cell cycle times quantified in Figure 3G.
