Eng, spermatheca, en1, spt
transcription factor - homeodomain - engrailed class - segment polarity gene - involved in compartment identity and boundary formation - positively regulates the and negatively regulates the Hedgehog targets and
Gene model reviewed during 5.49
Two monoclonal antibodies were generated against en (and also recognize inv), designated 4D9 and 4F11. 4D9 is directed to an engrailed specific region of the homeodomain, and recognizes en protien in several different species, but does not cross react with other homeodomain proteins.
Phosphorylated. Phosphorylation may directly or allosterically modify its function.
Click to get a list of regulatory features (enhancers, TFBS, etc.) and gene disruptions (point mutations, indels, etc.) within or overlapping Dmel\en using the Feature Mapper tool.
Comment: reported as procephalic ectoderm primordium
Comment: reported as procephalic ectoderm primordium
Comment: reported as procephalic ectoderm primordium
Comment: reported as head epidermis primordium
Comment: reported as head epidermis primordium
en is expressed in posterior midline glia but not in anterior midline glia in stage 12 embryos. After its early pair rule and segment polarity expression patterns in early embryos, en expression becomes more expansive. At stage 10, en expression along with run expression divides the midline into four regions, anterior (runt[+], en[-]), middle (runt[-], en[-]), posterior (runt[-], en[+]), and extreme posterior (runt[-], en[-]). At stage 10, en is expressed in 2 midline cells. A second, late phase of en expression was activated in the extreme posterior runt[-] en[-] cells that, in combination with the early en[+] cells, generated a single posterior en[+] region containing around eight cells. By the end of stage 11, en is expressed in all posterior midline glia. These en[+] cells give rise to the posterior midline glia, MP4-6, and the median neuroblast.
Expression pattern inferred from unspecified enhancer trap line.
The en protein is localized to the nucleus, but becomes diffuse during mitosis.
en protein is expressed in 14 stripes beginning at embryonic stage 8. After stage 11, expression does not overlap with that of ci. en protein expression in the wing disc also does not overlap with that of ci
en protein is expressed in a two cell wide row of cells anterior to the segment boundaries of each segment. Expression in the posterior row of cells decreases as a groove forms at the segment boundary.
The en protein is expressed in a specified subset of neuroblasts in embryonic stages 8-11. (see also FBrf 42042)
Delayed changes in en expression were observed in response to ectopic eve expression in evehs.PS embryos. Four different expression patterns were observed depending on the timing of ectopic eve protein induction.
en expression was observed sequentially in 5 "centers" anterior to the mandibular segment starting at embryonic stage 8. These are the "en antennal stripe", the "en head spot", the "en intercalary spot", the "en expression in the anterior dorsal hemispheres" and the "en expression in the clypeolabrum". Later two of the spots split, generating the "en antennal spot" and the "en secondary head spot". The migration of these en-expressing cells was followed throughout embryonic development.
en expression is diminished in wg and arm mutants. An allelic series was described for each with with increasingly severe segment polarity phenotypes and earlier and more severe loss of en expression. The segmental stripes decay with a similar asymmetric pattern in wg and arm mutants.
en protein is expressed in stripes in the posterior region of each segment in the developing embryo, the detection of en expression in the even numbered stripes slighted preceeds the detection of odd numbered stripes.
en protein is expressed in stripes in the posterior region of each segment in the developing embryo. Detection of en expression in the even-numbered stripes slightly preceeds detection in odd-numbered stripes.
GBrowse - Visual display of RNA-Seq signalsView Dmel\en in GBrowse 2
Please Note This section lists cDNAs and ESTs that fall within the genomic extent of the gene model, which may include cDNAs and ESTs of genes within introns, or of overlapping genes. Please see GBrowse for alignment of the cDNAs and ESTs to the gene model.
For each fully sequenced cDNA the DGRC maintains various forms of the cDNA (e.g tagged or untagged) in several different host vectors for subsequent cloning and expression in Drosophila and Drosophila cell lines.
The highly divergent mosquito engrailed protein Agam\en is able to substitute for en protein during all stages of development. Agam\en expression by enhancer-trapping is precise enough to restore viability to en mutants.
Ectopic expression of en prior to neuronal specification can misroute axons, whereas en has no major effect when ectopically expressed in neurons only. Therefore, the action of en on axonal pathfinding occurs at early stages, before neuronal cell fate is established.
A 139bp minimal pairing sensitive element (PSE) from en regulatory DNA has been defined. This element mediates Pairing Sensitive Silencing (PSS). The PSE includes 8 protein binding sites at least 5 of which are important for pairing sensitive silencing. One of these is for pho protein, and another has the GAGAG sequence known to be bound by Trl and psq proteins.
wg mutant embryos have residual mirror-symmetric pattern due to an en-dependent signal specifying anterior denticle fates. The en-dependent signal acts unidirectionally and wg activity imposes the asymmetry.
Three EMS induced en alleles were identified in a screen for mutations affecting commissure formation in the CNS of the embryo.
When en is removed from Posterior cells, they transform into the Anterior cells of the same parasegment, rather than Anterior cells of the same segment.
In the developing abdomen the state of en, whether off or on, determines whether a cell is of Anterior or Posterior type. en acts in the Anterior compartment, where it is induced by hh gene product, in a narrow band of cells, which has crossed the Anterior/Posterior compartment boundary. en causes these cells to form a special type of cuticle.
Cell affinities in the adult abdomen depend on en : cells of the P compartment have affinities that are distinct from A cells.
In solution the en homeodomain binds to a DNA molecule containing a single TAAT sequence in an analogous manner to that observed in the X-ray co-crystal structure. en also binds to a more complex site, having overlapping TAAT sequences, in more than one orientation.
Interactions between en and polyhomeotic are required to maintain the anterior-posterior boundary and posterior cell fate in the wing.
Segment polarity gene expression is necessary for the survival of specific rows of epidermal cells.
en promotes the development of the dorsolateral fat body, midgut visceral mesoderm and somatic gonads while it suppresses development of somatic muscles, heart and ventral fat body. There is a balance between fat body and somatic gonadal precursor (SGP) development with tin, wg and en driving cells in the primary clusters towards SGP development and srp driving them towards fat body development.
Genes known to be expressed in compartment-specific manner in discs are expressed in analogous patterns in each primordia.
Adjacent and conserved ftz and cofactor binding sites within the en intron enhancer are necessary and sufficient for transcriptional activation. The cofactor sites can be specifically bound by ftz-f1, and the ftz homeodomain and ftz-f1 bind cooperatively in vitro.
en is one of a class of genes with TATA-less promoters that have the conserved DPE sequence.
Amino acids in the N-terminal arm of the homeodomain, as well as at position 54 of the homeodomain, control the DNA binding specificity of the homeodomain.
Despite the absence of a syncytium in C.floridanum embryos monoclonal antibodies to en, Ubx and abd-A demonstrate their cognate proteins are expressed in a conserved pattern in the post-gastrulation stages of development. The expression of the eve cognate protein is not completely conserved and lacks a pair rule phase to its expression.
en is post-translationally modified by casein kinase II (CK-II). The targets for CK-II phosphorylation in vitro are serine residues 394, 397, 401 and 402, and phosphorylation by CK-II stimulates DNA binding.
Maintenance but not initiation of en gene expression in the embryo requires trx, which is also required to maintain stable long-term expression of the homeotic genes throughout development. trx is required for normal en expression in the wing imaginal disc. trx-dependent loss of en expression in the dorsal fat body is correlated with female sterility.
en has a dual role in wing development: a general role in patterning the appendage, achieved through the activation of secreted proteins like hh and dpp, and a more specific one, determining posterior identity, in which the inv gene may be implicated.
The organisation of the tail region of the embryo is documented from studies of cuticular markers enabling a more direct comparison between homologous structures on the embryo and larval cuticle.
Clonal analysis supports the view that dpp is a direct target of repression by en, and that en defines the posterior extent of the dpp stripe in the wing imaginal disc. The en-hh-ptc regulatory loop that is responsible for segmental expression of wg in the embryo is reused in imaginal disks to create a stripe of dpp expression along the A/P compartment boundary.
en both directs the posterior compartment pathway and creates the compartment border in wing development.
en governs growth and patterning in both anterior and posterior wing compartments by controlling the expression of the hh and dpp products as well as the response of the cells to them. en activity programs wing cells to express hh whereas the absence of en activity programs them to respond to hh by expressing dpp. Consequently, posterior cells secrete hh product and induce a stripe of neighboring anterior cells across the compartment boundary to secrete dpp.
en is required for patterning of the posterior wing margin, specifically to inhibit the formation of stout and socketed bristles (characteristic of the anterior wing margin) posterior to wing vein 3. en participates, presumably indirectly, in cell-cell interactions.
Three pairing sensitive (PS) sites map to a 1.6kb fragment of en. PS sites of en can suppress expression of a linked marker gene (w) carried in P-elements, dependent on the presence of two copies of the P-element in proximity in the genome.
Comparisons of early development to that in other insects have revealed conservation of some aspects of development, as well as differences that may explain variations in early patterning events.
Wild type activity of five segment polarity genes, wg, ptc, en, nkd and hh, can account for most of the ventral pattern elements in the embryo. wg is required for naked cuticle. wg generates the diversity of cell types within the segment but each specific cell identity depends on the activity of ptc, en, nkd and hh.
en is a specific repressor of activated transcription, and may act via a different mechanism than eve, perhaps by interfering with interactions between transcriptional activators and the general transcription machinery. A minimum repression domain of 55 residues, rich in alanine, can function when fused to a heterologous DNA binding domain. Unlike the repression domains of eve and Kr, the en repression domain is moderately charged.
The positioning of en stripes in the embryo is largely determined by the actions of negative regulators: run is required to limit the domains of en-expression in odd-numbered parasegments, while odd is required to limit the domains of en-expression in even-numbered parasegments. Activation of en at the anterior margins of the parasegments requires repression of run and odd by eve.
The BRE region of Ubx includes binding sites for hb, ftz, tll, en and twi. The binding of their products and the interplay between them is responsible for generating the expression pattern directed by the BRE.
Choice of cell fate made by en expressing cells in embryonic parasegments is mediated by wg, in a function distinct from its early role in maintaining en expression. en expressing cells respond differently to wg at different stages of development:early wg stabilizes the subdivision of the body axis by maintaining en expression, whereas later input generates cell-type diversity.
en alleles fall into four classes, all recessive. Class 1: en1 (See en1 allele record for full description). Viable hemizygous and homozygous; fertile. Longitudinal cleft extends from rear border of scutellum forward, may be reduced to median nick or posterior flattening of scutellum. Wings larger, broader and thin textured with spatulate end; venation and distribution of sensilla abnormal in posterior wing compartment. Variable duplication of anterior triple row bristles on posterior margin; alula reduced, with costal-like bristles. Clones of en1 cells of posterior compartment origin fail to respect anterior-posterior compartment border in wing disc as do mwh1 clones in wing discs of en1 homozygotes. en1 abnormalities are associated with posterior compartment structures only, except for scutellar cleft. Not suppressed by su(Hw)1. Class 2: Lethal alleles with normal cytology. Embryonic lethal. Anterior margin of each segment defective. Pair rule defects in naked cuticle of T1, T3, A2, A4, A6, A8 result in pair-wise fusion of adjacent segments. Autonomous effects in adult cuticular clones observed in posterior compartment of proboscis, thorax, abdomen and genitalia. The en1/"enlethal" heterozygote characterized by wing abnormalities only; disruption of anterior crossvein, gap in vein IV and occasional socketted bristles on posterior margin. Class 3: Deficiencies and lethal alleles with inversion or translocation breakpoints. Embryonic lethal. Embryonic segment defects slight and variable. Alleles of this class in heterozygous combination witn en1 produce adults more extreme than en1. For example, in en1/en2, legs are truncated, the tarsi reduced to densely bristled stumps; wings are greatly enlarged and spatulate with greater disruption of veins IV and V; higher penetrance of socketed bristles along the posterior margin. Extreme scutellar cleft. Class 4: Non-lethal alleles with breakpoints. Hemizygous viable, embryos normal. Heterozygous with other allele classes, variable gaps in wing veins IV and V. Variable reductions or deletions in male and female genitalia. Scutellum may also be affected.
Embryos mutant for two or more Pc-group genes (Pc, Scm, Pcl, Psc, Asx, E(Pc), E(z), ph-d, pho and esc) show strong ectopic en expression, but only weak derepression occurs if embryo is mutant at only one of the Pc group genes. This effect is independent of the function of en itself, and wg. Expression of en in esc mutant embryos is almost normal, suggesting that esc may function in a pathway different from the other genes in the group.
Expression pattern of hh coincides with that of en in the epidermis. Though initially independent of en, hh expression later becomes en-dependent. In the absence of ptc function, wg expression, which is normally en-dependent, no longer requires en.
en expression pattern in the embryonic head strengthens the hypothesis that the clypeolabrum evolved from the fusion of paired labral appendages.
en expression becomes independent of wg extracellular influence and relies on positive autoregulation. Autoregulation is transient so does not supply a mechanism for determination of the en-cell fate.
In transfection assays en is an active transcriptional repressor. Active repression is distinct from the effects of passive homeodomain-containing proteins which repress when competing with activators for binding sites and activate when competing with en. Active repression activity maps outside the en homeodomain and this activity can be transferred to a heterologous DNA binding domain.
When a fragment of en DNA extending from -2.4kb to +0.8kb is included in the CaSpeR vector the eye colour of transformants often behaves anomalously, half of the homozygotes have a lighter eye colour than the heterozygotes and a quarter have the same eye colour as the heterozygotes. This occurred at many different insertion sites whether the upstream en fragment is directly adjacent to w+mC or when it is 1kb away. The suppression of eye colour is dependent on the proximity of the two copies of the transposon, either in cis or trans. The protein that mediates this phenomenon is probably not a homeodomain-containing protein as deletion of the homeodomain binding sites results in suppression of w expression.
en mutants exhibit variable pair rule fusions and segment polarity reversals.
The crystal structure of a complex containing the en homeodomain and a duplex DNA site has been determined.
The en1/"enlethal" heterozygote characterized by wing abnormalities only; in some combinations complementation is complete or nearly so.
A transient expression assay has been employed to investigate the potential of homeobox genes to function as transcriptional activators.
A monoclonal antibody (MAb4D9) reacts specifically to en proteins in a variety of species. An ancestral function of en may have been in neurogenesis and its other functions in arthropods may represent a more recent addition.
The expression of en protein in Drosophila, grasshopper and crayfish has been compared.
Genetic analysis demonstrates that en is dispensable for efficient homeotic gene expression in the visceral mesoderm.
Striped en expression during post-blastoderm development is controlled by a cis-regulatory programme distinct from that controlling the establishment of expression at the cellular blastoderm stage.
en protein isolated from cultured cells and embryos is post-translationally modified.
Heat shock induced en gene expression causes pattern defects similar to those in embryos lacking en gene product. The sensitivity to heat shock is only during the cellular blastoderm and early gastrulation periods when the en protein localises into segmentally reiterated stripes and represents only a small portion of the normal period of en gene expression.
en is expressed in the posterior (but not the anterior) compartments of the embryo and larva.
"enlethal" alleles show no maternal effect.
At 29oC, duplication of anterior compartment bristles in mirror-image symmetry in the posterior compartment of second antennal segment occurs.
The gene is named "engrailed", a heraldic term from the middle-age french "engraile", literally "dented by hail", after the mutant phenotype of a notch in the scutellum.