Mutations in somePolycomb group genes ofDrosophila interfere with regulation of segmentation genes

McKeon, Joanie; Slade, E.; Sinclair, Donald A. R.; Cheng, Niansheng; Couling, Mitchell; Brock, Hugh W.

doi:10.1007/bf00583898

Cited by 39 publications

(20 citation statements)

References 48 publications

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“…The en gene, like Ubx, is negatively autoregulated in imaginal discs (Guillén et al, 1995;Simmonds et al, 1995;Tabata et al, 1995) and is also regulated by Pc-group proteins (Busturia and Morata, 1988;Moazed and O'Farrel, 1992;McKeon et al, 1994). There is a PRE in the en gene located upstream its transcription start site (Kassis et al, 1991;Kassis, 1994) and transcription through this PRE has been reported (Schmitt et al, 2005).…”

Section: Research Articlementioning

confidence: 99%

Polycomb-dependentUltrabithoraxHox gene silencing induced by high Ultrabithorax levels inDrosophila

et al. 2008

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The Ultrabithorax (Ubx) gene of Drosophilaspecifies the third thoracic and first abdominal segments. Ubxexpression is controlled by several mechanisms, including negative regulation by its own product. We show here that if Ubx expression levels are inappropriately elevated, overriding the auto-regulatory control, a permanent repression of Ubx is established. This continuous repression becomes independent of the presence of exogenous Ubx and leads to the paradoxical result that an excess of Ubx results in a phenotype of Ubx loss. The mechanism of permanent repression depends on Polycomb-group genes. Absence of endogenous Ubxtranscription when Ubx levels are highly elevated probably activates Polycomb complexes on a Polycomb response element located in the Ubx major intron. This, in turn, brings about permanent repression of Ubx transcription. Similar results are obtained with the gene engrailed, showing that this mechanism of permanent repression may be a general one for genes with negative auto-regulation when levels of expression are transitorily elevated.

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Section: Research Articlementioning

confidence: 99%

Polycomb-dependentUltrabithoraxHox gene silencing induced by high Ultrabithorax levels inDrosophila

et al. 2008

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“…The ph gene was first characterized as one of the Drosophila Pc-G genes, which encode transcriptional repressors required for maintaining the spatial pattern of homeotic gene expression during embryonic and larval development (Christen and Bienz, 1994;McKeon et al, 1994;Soto et al, 1995). ph has additional functions during development, since it has also been implicated in restriction of anterior compartment expression of engrailed and hedgehog in the wing imaginal disc (Maschat et al, 1998;Maurange and Paro, 2002).…”

Section: Requirements For the Polycomb Group In Oogenesismentioning

confidence: 99%

polyhomeoticis required for somatic cell proliferation and differentiation during ovarian follicle formation inDrosophila

et al. 2004

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The polyhomeotic (ph) gene of Drosophila is a member of the Polycomb group (Pc-G) genes, which are required for maintenance of a repressed state of homeotic gene transcription, which stabilizes cell identity throughout development. The ph gene was recovered in the course of a gain-of-function screen aimed at identifying genes with a role during ovarian follicle formation in Drosophila, a process that involves coordinated proliferation and differentiation of two cell lineages, somatic and germline. Subsequent analysis revealed that ph loss-of-function mutations lead to production of follicles with greater or fewer than the normal number of germ cells associated with reduced proliferation of somatic prefollicular cells, abnormal prefollicular cell encapsulation of germline cysts and an excess of both interfollicular stalk cells and polar cells. Clonal analysis showed that ph function for follicle formation resides specifically in somatic cells and not in the germline. This is thus the first time that a role has been shown for a Pc-G gene during Drosophila folliculogenesis. In addition, we tested mutations in a number of other Pc-G genes, and two of them, Sex combs extra (Sce) and Sex comb on midleg (Scm), also displayed ovarian defects similar to those observed for ph. Our results provide a new model system, the Drosophila ovary, in which the function of Pc-G genes, distinct from that of control of homeotic gene expression, can be explored.

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“…Some PcG genes are known to be required for the maintenance of kni expression domains in the embryo (McKeon et al, 1994;Pelegri and Lehmann, 1994;Saget et al, 1998). It is also likely that some trxG genes or other complexes of trxG proteins, such as the Ash2 complex (Papoulas et al, 1998), may interact with repressor sequences necessary to keep kni expression in an off state beyond L2.…”

Section: Ash2 Complex Maintains Kni In An Off Statementioning

confidence: 99%

Activation and repression activities ofash2inDrosophilawing imaginal discs

2004

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Polycomb (PcG) and trithorax (trxG) group genes are chromatin regulators involved in the maintenance of developmental decisions. Although their function as transcriptional regulators of homeotic genes has been well documented, little is known about their effect on other target genes or their role in other developmental processes. In this study, we have used the patterning of veins and interveins in the wing as a model with which to understand the function of the trxG gene ash2 (absent, small or homeotic discs 2). We show that ash2 is required to sustain the activation of the intervein-promoting genes net and blistered (bs) and to repress rhomboid(rho), a component of the EGF receptor (Egfr) pathway. Moreover, loss-of-function phenotypes of the Egfr pathway are suppressed by ash2 mutants, while gain-of-function phenotypes are enhanced. Our results also show that ash2 acts as a repressor of the vein L2-organising gene knirps (kni), whose expression is upregulated throughout the whole wing imaginal disc in ash2 mutants and mitotic clones. Furthermore, ash2-mediated inhibition of kni is independent of spalt-major and spalt-related. Together, these experiments indicate that ash2 plays a role in two processes during wing development: (1)maintaining intervein cell fate, either by activation of intervein genes or inhibition of vein differentiation genes; and (2) keeping kni in an off state in tissues beyond the L2 vein. We propose that the Ash2 complex provides a molecular framework for a mechanism required to maintain cellular identities in the wing development.

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Mutations in somePolycomb group genes ofDrosophila interfere with regulation of segmentation genes

Cited by 39 publications

References 48 publications

Polycomb-dependentUltrabithoraxHox gene silencing induced by high Ultrabithorax levels inDrosophila

Polycomb-dependentUltrabithoraxHox gene silencing induced by high Ultrabithorax levels inDrosophila

polyhomeoticis required for somatic cell proliferation and differentiation during ovarian follicle formation inDrosophila

Activation and repression activities ofash2inDrosophilawing imaginal discs

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