Pan-neural Prospero terminates cell proliferation during Drosophila neurogenesis - PubMed (original) (raw)

. 2000 Jan 15;14(2):147-51.

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Pan-neural Prospero terminates cell proliferation during Drosophila neurogenesis

L Li et al. Genes Dev. 2000.

Abstract

Organogenesis requires coordination between developmental specific regulators and genes governing cell proliferation. Here we show that Drosophila prospero encodes a critical regulator of the transition from mitotically active cells to terminal differentiated neurons. Loss of pros results in aberrant expression of multiple cell-cycle regulatory genes and ectopic mitotic activity. In contrast, ectopic pros expression causes transcriptional suppression of multiple cell-cycle regulatory genes and premature termination of cell division. pros activity, hence, provides a critical regulatory link between neuronal lineage development and transcriptional regulation of cell cycle regulatory genes.

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Figures

Figure 1

Figure 1

Increased mitotic activity in the CNS of pros mutant embryos. Mitotic activity in wild type (A,C,E) and homozygous pros mutant (B,D,F) embryos. (A, B) S-phase-specific expression of Histone 1a RNA in the ventral cord of stage-16 wild-type (A) and homozygous pros mutant (B) embryos. (C,D) BrdU incorporation (green) in stage-15 wild-type (C) and pros mutant (D) embryos. Double labeling of embryos with mouse anti-Pros (red) was used to identify homozygous pros mutant embryos. (E,F) Expression of the M-phase-specific marker phospho Histone H3 (red) in the ventral cords of wild-type (E) and pros mutant (F) embryos. For identification of pros mutant embryos based on their axonal defects, embryos in E and F are double labeled with axon-specific monoclonal antibody BP102 (green). All three cell-cycle markers show a dramatic increase expression in pros mutant embryos (B,D,F) when compared with wild-type embryos (A,C,E). (G,H) Detection of apoptotic cell death using TUNEL assay. (G) TUNEL assay pattern in the ventral cord of a wild-type, stage-16 embryo. (H) The ventral cord of a prosJO13 mutant, stage-16 embryo shows a substantially increased number of labeled cells in TUNEL assay.

Figure 2

Figure 2

Loss of pros function is associated with ectopic RNA expression of cell-cycle regulatory genes. RNA expression of cycA, cycE, and stg during late embryogenesis of wild-type (A,C,E,) and homozygous pros mutant (B,D,F,) embryos. (A,B) cycA RNA expression in stage-16, wild-type (A) and pros mutant (B) embryos. (C,D) cycE RNA expression in the ventral cord of stage-16, wild-type (C) and pros mutant (D) embryos. (E,F) stg RNA expression in wild-type (E) and pros mutant (F) embryo.

Figure 3

Figure 3

Ectopic Pros expression suppresses cell proliferation. (A,B) CNS of wild-type (A) and Kruppel (Kr)–Gal4/UAS-Pros (B) stage-15 embryos stained with anti-HRP. (B) Ectopic expression of Pros within the Kr-domain results in thinning and disruptions of the ventral cord (asterisks). (C–K) Ectopic Pros suppresses mitotic activity. (C,E) Wild-type embryos. (D,F–K) Kr-Gal4/UAS-Pros embryos. These embryos express high levels of Pros protein within the Kruppel domain (labeled in red in panels G,H,I,K). (C,D) RNA expression of the S-phase-specific Histone 1a transcript in wild-type embryo (C) and an embryo with ectopic Pros expression in the Kr-domain (D). Histone 1a RNA expression is suppressed in segments with ectopic Pros expression. (E,F) BrdU incorporation in wild-type (E) and Kr–Gal4/UAS–Pros (F) embryos. (E) Wild-type embryo with a normal pattern of BrdU incorporation. (F–H) A Kr–Gal4/UAS–Pros embryo that has been double-labeled for BrdU incorporation (F; green) and Pros expression (G; red). (H) A merge of F and G. Ectopic expression of Pros results in strong suppression of BrdU incorporation. (I–K) Dorsal region of a stage-12 Kr–Gal4/UAS–Pros embryo double labeled with anti-Pros (red) and the M-phase marker anti-phospho Histone H3 (green). (I) Pros expression at the posterior border of the Kr-domain. (J) Phospho-Histone H3 expression is visible in cells that have entered M-phase. (K) Composite image of I and J. Only limited overlap, as indicated by yellow labeling, is evident between cells expressing the M-phase marker (red) and cells with ectopic Pros expression (green). Most of the double-labeled cells are located in the border region of ectopic Pros expression, which has lower levels of ectopic Pros.

Figure 4

Figure 4

Ectopic Pros suppresses the RNA expression of critical cell-cycle regulatory genes. (A) Kr–Gal4/UAS–Pros embryo labeled with anti-Pros. High levels of ectopic Pros are expressed in the Kruppel domain, marked by arrows. (B–G) RNA expression of cycA (B), cycE (C, lateral view; D, dorsal view), E2F (E), RBF (F), and stg (G). A strong reduction, or complete absence, of RNA expression of these cell-cycle regulatory genes is evident in regions with ectopic Pros expression (arrows). (H) RNA expression of the enhancer trap line cycA03946_–_lacZ reporter gene in a Kr–Gal4/UAS–Pros embryo. A strong reduction in lacZ RNA levels is evident in central region of the embryo expressing ectopic Pros. (I–N) Ectopic Pros expression does not result in a general suppression of gene expression. Ectopic expression of Pros (I,L) does not result in suppression of runt (J,K) or hunchback (M,N) expression. White arrows in panels I–N mark the borders of the central region with ectopic Pros expression.

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