chinmo is a functional effector of the JAK/STAT pathway that regulates eye development, tumor formation, and stem cell self-renewal in Drosophila - PubMed (original) (raw)

chinmo is a functional effector of the JAK/STAT pathway that regulates eye development, tumor formation, and stem cell self-renewal in Drosophila

Maria Sol Flaherty et al. Dev Cell. 2010.

Abstract

The Drosophila STAT transcription factor Stat92E regulates diverse functions, including organ development and stem cell self-renewal. However, the Stat92E functional effectors that mediate these processes are largely unknown. Here we show that chinmo is a cell-autonomous, downstream mediator of Stat92E that shares numerous functions with this protein. Loss of either gene results in malformed eyes and head capsules due to defects in eye progenitor cells. Hyperactivation of Stat92E or misexpression of Chinmo results in blood cell tumors. Both proteins are expressed in germline (GSCs) and cyst stem cells (CySCs) in the testis. While Stat92E is required for the self-renewal of both populations, chinmo is only required in CySCs, indicating that Stat92E regulates self-renewal in different stem cells through independent effectors. Like hyperactivated Stat92E, Chinmo misexpression in CySCs is sufficient to maintain GSCs nonautonomously. Chinmo is therefore a key effector of JAK/STAT signaling in a variety of developmental and pathological contexts.

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Conflict of interest statement

The authors state no conflict of interests.

Figures

Figure 1. chinmo is autonomously regulated by JAK/STAT pathway activity

(A) chinmo mRNA is upregulated in cells anterior to the furrow in a third instar GMR-upd eye disc. (B) chinmo mRNA is absent at this stage in a wildtype (WT) eye disc. (C) Activity of the JAK/STAT pathway, as assessed by the 10xSTAT-dGFP transcriptional reporter, is not detected in a mid-third instar WT eye disc (arrows). (D,E) chinmo mRNA is expressed in a second instar eye disc, like 10xSTAT-dGFP. (F–F”) Expression of chinmo-lacZ (red) is autonomously lost in Stat92E clones, which lack GFP (pink arrowheads). (G) chinmo mRNA (black) is autonomously increased in a hop flip-out clone (hop FO) (red outline). (H–H”) Chinmo protein (red) is increased in hop FO clones (arrowheads). The furrow is marked by a green arrowhead in A–C,F,G. Dorsal is up and anterior to the left. (I) A dorsal view of a WT adult Drosophila head. (J,K) Animals with Stat92E− M+ clones in the eye-antennal disc exhibit small eyes, excess head cuticle, and are frequently headless. (L,M) Animals carrying chinmo− M+ clones also exhibit these phenotypes. Arrow points to an adult with only a rudimentary head (K,M). (N) Ser-LacZ expression (magenta) in a WT eye-antennal disc. Eyegone (Eyg) is green. (O,P) Ser-lacZ is ectopically expressed in the antennal disc in mosaic Stat92E (O’, arrowheads) or chinmo (P’, arrowheads) clones. Clones lack GFP in O,P.

Figure 2. Mis-expression of chinmo causes melanotic tumors

(A–C) Melanotic tumors are present in third instar larvae harboring hop (B, arrow) or chinmo (C, arrow) mis-expressing clones but not in WT (A). (D) In the lymph gland, Chinmo (red) is present in some MZ prohemocytes and some CZ hemocytes. E,E’ are close-ups of D. (F) Chinmo is present in mature hemocytes in the eye disc. (G) Schematic diagram of Chinmo expression in the lymph gland. In the MZ, some cells with blue nuclei (DNA) lack Chinmo while those with red nuclei express Chinmo. In the CZ, some Hml+ (green) cells lack Chinmo, but most express both Hml and Chinmo. In the CZ, some cells lack Hml but express Chinmo. Hml>gfp (green); DNA (blue) in D–F.

Figure 3. Stabilized Stat92E and Chinmo are present in GSCs and CySCs

(A) In a WT testis Stat92E protein (red) is stabilized in GSCs, CySCs and early cyst cells (red, green, and blue arrowheads, respectively). CySCs and early cyst cells are Tj+ (blue). (B) Chinmo is expressed in a Tj− GSC, in a Tj+ CySC and in a Tj+ early cyst cell (red, green and blue arrowheads, respectively). (C) There is an increased number of GSCs (red) and CySCs (blue) in a nos>upd testis. (D-D’’’) Chinmo (blue) is upregulated in a nos>upd testis. In D’-D’’’ a yellow arrowhead indicates a Tj+ CySC that expresses Chinmo and a white one points to a Chinmo+ Vasa+ GSC. Fas3 is green in A,B and an * marks the Hub in A–C. Vasa is red and Tj is green in D. (E) Schematic of the Drosophila testis. See text for details.

Figure 4. chinmo is required autonomously for the self-renewal of CySCs

(A,B) Vasa+ GSCs mutant for chinmo (A’,A’’, red arrowheads) and Zfh1+ CySCs mutant for chinmo (B’,B’’, green arrowhead) can be detected next to the Hub at 2 days pci. (C,D) At 7 days pci, _chinmo_− Vasa+ GSCs can be found next to the Hub (C’,C’’, red arrowhead). At this time point no _chinmo_− Tj+ CySCs can be found in the niche (C,D). Late cyst cells lacking chinmo are found far from the niche at 7 days pci (D’,D’’, blue arrowheads). In A–D chinmo clones are GFP+ and Vasa is red. Zfh1 is blue in A,B and Tj is blue in C,D. An * marks the Hub.

Figure 5. Sustained chinmo expression results in expansion of GSCs and CySCs

(A) In a WT testis, only stem cells at the apical tip fluoresce when stained with Hoechst 33342 (arrowhead). (B) In an eyaA3>chinmo testis DNA-bright cells accumulate throughout the testis (arrowhead). (C) In a WT testis, activated Stat92E (red) is found in GSCs and CySCs in contact with the Hub (bracket), as well as in early cyst cells. (D) In an eyaA3>chinmo testis, stabilized Stat92E is expressed in the same pattern as in WT (bracket). Tj is blue in C,D. (E) In a WT testis, Tj+ CySCs and early cyst cells are only found at the apical tip of the testis (E”, bracket). (F) In an eyaA3>chinmo testis, Tj+ somatic cells are found throughout the testis (F-F”, brackets). 1B1 (green), Vasa (red) and Tj (blue) in E,F. (G) In a WT testis, Zfh1 (green) is expressed highly in CySCs and at lower levels in early cyst cells. Both cell types express Tj (blue). (H) However, in an eyaA3>chinmo testis, Zfh1+ CySCs and early cyst cells are found throughout the testis. In G,H green arrowheads mark CySCs and green arrows mark early cyst cells. Vasa (red) and Tj (blue) in H. (I) In a wild type testis esg-lacZ (green) is restricted to GSCs and GBs (I-I”, brackets). (J) In an eyaA3>chinmo testis, esg-lacZ positive cells are expanded throughout the testis (J-J”, brackets). Vasa (red) and Tj (blue) in I,J. An * marks the Hub.

Figure 6. chinmo does not act through zfh1 to promote the self-renewal of CySCs

(A-A’’’) Zfh1 (red) is not reduced in Tj+ CySCs/early cyst cells lacking chinmo (arrowheads). (B-B’’’) Chinmo (red) is not diminished in Tj+ CySCs/early cyst cells lacking zfh1 (arrowheads). Clones lack GFP expression in A,B. (C-C’’’) chinmo MARCM clones over-expressing zfh1 do not restore CySC characteristics to the clones. Only Zfh1−, Tj− GSCs mutant for chinmo were found close to the niche, pink arrowheads. Clones express GFP and Zfh1 in C. An * marks the Hub in A–C. (D) Schematic of the Chinmo protein and its putative mammalian homolog ZFP509. (E) A model of the autonomous requirement of activated Stat92E for self-renewal in GSCs and CySCs and autonomous requirement of Chinmo and Zfh1 in CySC self-renewal (left CySC (blue cell)). This is also a model of the non-autonomous expansion of CySCs and GSCs caused by hyperactivated JAK, misexpression of chinmo or of zfh1 in CySCs/early cyst cells (right CySC). STATP indicates activated Stat92E. See text for details.

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chinmo is a functional effector of the JAK/STAT pathway that regulates eye development, tumor formation, and stem cell self-renewal in Drosophila - PubMed (original) (raw)