Engrailed

Engrailed

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{Models}

Symbol: en	Flybase ID: {Flybase_ID}
Synonyms: {Name}	{GadFly}
Function: {Short_Function}	{LocusLink}
Keywords: {Keywords}	{Interactive_Fly}

{Summary}

Function/Pathway

Functions as a ‘selector’ gene (Garcia-Bellido 1975), directing posterior cells to form posterior rather that anterior pattern, and to avoid mixing with anterior cells (Morata, 1975; Lawrence, 1976; Lawrence, 1982)
Represses txn of: dpp (Sanicola et al., 1995)
En activity programs wing cells to express Hh wheras the absence of en activity programs them to respond to Hh by expressing dpp (Burke, 1999)
En function inhibits triple-row specification (Hidalgo, 1994)

Genetic interactions

Hedgehog
- Is involved in maintaining Hh expression (Tabata et al., 1992)
- In embryos homozygous for loss-of-function alleles of hh, expression of en is lost from ectodermal cells after gastrulation (DiNardo, 1988), indicating that the activity of hh, like that of wg, is also required for the maintenance of en transcription. Although ubiquitous expression of wg results in the ectopic activation of en (Noordermeer, 1992), the distribution of En protein is unaltered in heat-shocked HS-hh embryos (Ingham, 1993: Fig 2C). Thus, although necessary for the maintenance of en, expression of hh is not sufficient for its activation.
In smo clones (no Hh signaling) dpp-lacZ, Ptc and anterior En expression is inhibited, suggesting that they are direct targets for regulation by Hh signaling (Strigini, 1997)
En governs growth and patterning in both compartments by controlling the expression of the secreted proteins hedgehog and decapentaplegic as well as the response of cells to these signaling molecules (Zecca, 1995)
En programs wing cells to express hh whereas the absence of en activity programs them to respond to hh and express dpp (Zecca, 1995)
Dpp can exert a long-range organizing influence on surrounding wing tissue, specifiying anterior or posterior pattern depending on the compartmental provenance, and hence the state of en activity, of the responding cells. (Zecca, 1995)
Col is not required for the hh-induced anterior En expression (Vervoort, 1999)
in Pka-C1 mutants in the anterior compartment Col, Ptc, and En are up regulated but only at some distance away from the DV boundary (Figs. 3A-3C) (Glise, 2002)
Ectopically expressed N^intra (a dominat active form) produces a cell-autonomous down-regulation of both Col and Ptc (Fig 6C and 6D). By contrast, expression of En was not affected by Nintra expression in either the posterior compartment or the anterior compartment in response to Hh (Fig. 6E), consistent with the fact that en is normally activated in the prospective wing margin (Glise, 2002)

Physical interactions

Three identified in vitro En binding sites are found in a dpp-lacZ reporter gene (Sanicola, 1995)

Transcriptional Regulation

En becomes expressed in a narrow zone of A cells along the A/P boundary at late stages of wing disc development (Blair, 1992)
A-specific expression of en is induced by high levels of Hh signaling (Strigini, 1997) and manifests itself in the suppression of a few innervated sensory bristles at the distal tip of the wing [see figure wt on left en clone on right] (Hidalgo, 1994)

Structure

{Structure}

Location (protein and transcript)

By contrast to the other Hh targets (Col, ptc, dpp), En is activated in the central row of cells that correspond to the prospective wing margin (Fig. 3A) (Glise, 2002)

Protein Modifications and Regulation

{Modifications}

Related to

{Related to}

Mutations

Mutant clones lacking both en and invected ectopically express dpp-lacZ and ptc in the posterior compartment where dpp activity ordinarily is repressed (Sanicola, 1995)
Mutant clones in the posterior compartment lacking both en and invected have a loss of hh expression (Sanicola, 1995)
Clones of en^E cells anterior to vein 3 are normal. However, clones growing between veins 3 and 4 narrow the space between these veins and transform the margin bristles into innervated bristles, which are normally found on the margin only anterior to vein 3. This phenotype correlates with the late expression of en anterior to the compartment boundary (Blair, 1992). Thus, en is required to inhibit the formation of stout and socketted bristles—characteristic of the anterior margin—posterior to vein 3 (in cells of both anterior and posterior compartments). (Hidalgo, 1994)

Overexpression / Ectopic expression

Overexpression by a hs-en construct eliminates the dpp-lacZ stripe (Sanicola, 1995)
Tuba1>en clones in the A compartment express hh-lacZ and have donuts of dpp-lacZ around the clones and the clones have smooth boundaries (Zecca, 1995)

Reagents

{Reagents}