transcription factor - bHLH - Hairy/E(spl) class - during embryogenesis it participates as a primary pair-rule gene in the establishment of segments - in the larval stage it functions negatively in determining the pattern of sensory bristles on the adult fly.
Gene model reviewed during 5.46
Transcription repression requires formation of a complex with a corepressor protein (Groucho). Interacts with gro (via WPRW motif) and Topors.
Ubiquitinated by Topors.
Has a particular type of basic domain (presence of a helix-interrupting proline) that binds to the N-box (CACNAG), rather than the canonical E-box (CANNTG).
The C-terminal WRPW motif is a transcriptional repression domain necessary for the interaction with Groucho, a transcriptional corepressor recruited to specific target DNA by Hairy-related proteins.
Click to get a list of regulatory features (enhancers, TFBS, etc.) and gene disruptions (point mutations, indels, etc.) within or overlapping Dmel\h using the Feature Mapper tool.
Expression was examined at four phases of embryonic stage 5. The striped pattern becomes visible in phase 1 (0-5'), all stripes except stripe 7 are expressed during phase 2 (5-17'), and their spacing and expression levels become largely uniform by phase 3 (17-30'). The stripes initially appear less clearly separated and more graded.
Transient expression of h transcript is observed in the salivary gland placode prior to invagination in late embryos.
Expression of h protein is observed in a rising gradient anterior to the morphogenetic furrow.
h protein stripes are first visible in embryos at cycle 14. The first stripes to appear are 1, 2, 3 and 7. Stripes 4 and 6 are fused to 3 and 7 when first detected. The seven stripes are not of equal width. The first two stripes are consistently broader than stripes 3, 5, 6, and 7, and stripe 4 is the weakest. The h stripes decay at the onset of gastrulation and germ band extension. h expression is also observed in a head patch between 80-95% egg length. h staining in the head persists through germ band elongation. By stage 9, the patch has migrated to the clypeolabrum, including the primordium of the labral tooth. h expression in the proctodeum begins at stage 9 and continues until about stage 16. At about stage 10, expression initiates in the stomodeum and in tracheal pit primordia and ceases in trachea by the onset of germ band retraction. During germ band retraction (stage 11) expression occurs throughout the mesoderm in both the somatic and visceral layers and persists until stage 14. Expression in the hindgut and anal plates begins around stage 14 and persists until stage 16.
GBrowse - Visual display of RNA-Seq signalsView Dmel\h 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.
Identified as a candidate gene for hypoxia-specific selection (via an experimental evolution paradigm) that is also differentially expressed between control and hypoxia-adapted larvae.
The h RNA localisation signal modulates the kinetics of cytoplasmic mRNA transport.
The regulation of h expression along the dorsal/ventral (D/V) axis of the developing leg adjacent to the anterior/posterior (A/P) compartment boundary requires input from both D/V and A/P patterning mechanisms.
Candidate gene for quantitative trait (QTL) locus determining bristle number.
Zygotic activation of h stripe 6 expression is preceded by activation in response to maternal cad activity, activation does not depend exclusively on the zygotic activity of kni as thought previously. cad and kni activities cooperate in a non-synergistic manner to activate h stripe 6 transcription. Absence of kni does not cause lack of h stripe 6 activation but delays the appearance of the stripe. Activation of the stripe depends on a minimal number of activator binding sites that are scattered throughout the stripe 6 element.
Identification: Enhancer trap expression pattern survey for loci expressed in the ring gland.
CtBP is a protein component of h-mediated repression, identified in a yeast interaction screen. CtBP interacts specifically and directly with a small, previously uncharacterised C-terminal region of h.
Fusion genes containing h binding sites suggest h is a silencer, which can repress upstream activators over a distance of at least 1kb. h mediates dominant repression and can silence multiple enhancers in a modular promoter.
The WRPW motif (the repressor domain) maps to the carboxy terminal of h-related proteins and is both necessary and sufficient to form protein-protein interactions with gro. gro is able to repress transcription when directly bound to DNA in the absence of binding to h-related proteins.
Mutations show strong interactions with high and low selection lines, abdominal and sternopleural bristle numbers are affected. Results suggest h is a candidate for bristle number quantitative trait loci (QTL) in natural populations or is in the same genetic pathway.
emc and h are expressed ahead of the morphogenetic furrow and are not required for photoreceptor cell determination. In emc- h- clones the morphogenetic furrow and differentiated eye field advance up to eight ommatidial rows ahead of adjacent wild type tissue. Results indicate that the morphogenetic furrow and neuronal differentiation are negatively regulated by a combination of anteriorly expressed HLH regulatory proteins, emc and h function together to regulate timing of furrow progression and photoreceptor development.
Transcriptional repression by the h/E(spl) family of bHLH proteins involves two separable mechanisms: repression of specific transcriptional activators, such as sc, through the bHLH and orange domains and repression of other activators via interaction of the C-terminal WRPW motif with corepressors, such as the gro protein.
A 900bp ac promoter fragment can be activated by binding of activators to three E-boxes and repressed via binding of h. The repression domain of h has mapped to a region containing the carboxyl terminus of the protein, this region is both necessary and sufficient for the repression of the ac promoter.
Expression of stripes in the blastoderm embryo can be generated by a two-step mode which involves regulatory interactions among the primary pair-rule genes h and run. Expression of h stripes 3 and 4 is directed by a common cis-acting element that results in an initial broad band of gene expression covering three stripe equivalents. Subsequently this expression domain is split by repression in the forthcoming interstripe region, a process mediated by a separate cis-acting element that responds to run activity.
Regulatory sequences critical for the expression of h stripes 5 and 6 have been difined. The posterior stripe boundaries are established by gap protein repressors unique to each stripe. The anterior boundaries of both stripe 5 and 6 are set by Kr. Both stripe enhancers have binding sites for Kr protein. h stripe 6 is critically dependent upon kni for activation, whereas stripe 5 requires a combination of activating proteins, gap and non-gap.
h binds to DNA, preferably at a noncanonical site, and has a novel DNA binding activity. Mutation of a single h binding site in ac blocks h mediated repression of ac transcription in culture cells and creates ectopic sensory hair organs in vivo. Results indicate that h represses sensory organ formation by directly repressing transcription of the ac gene.
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.
h is a sequence specific DNA-binding protein and transcriptional repressor. In vivo ac is a direct downstream target of h regulation. Direct repression of ac by h plays an essential role in pattern formation in the CNS.
Ectopic ttk expression causes complete or near complete repression of ftz and significant repression of eve, odd, h and runt.
Expression of prd depends on activation by gap gene hb, Kr, kni and gt products. Primary pair rule gene products act primarily in subsequent modulation rather than activation of prd stripes. Factors activating prd expression in the pair rule mode interact with those activating it along the dorso-ventral axis.
A molecular comparison of h expression and regulation in D.virilis and D.melanogaster reveals a high degree of conservation. The results of this and mutant analysis suggests that Kr and gt products establish the anterior and posterior borders of h stripe 5, respectively, through spatial repression.
Promoter analysis of h define the requirements for expression of individual stripes during embryogenesis. The two anterior-most expression domains appear to be dispensable for head morphogenesis and embryonic viability. h can affect patterning outside its apparent stripe domains, supporting the idea that it can act as a local morphogen.
Regulation of the h and ac expression patterns partitions the leg epidermis into striped zones that correspond to the pattern of longitudinal rows of leg bristles.
Enhancer trap lines were used to follow the development of ectopic sensillar precursors in wings of h and Hairy-wing ac mutants: ectopic sensilla appear correlated with ectopic achaete and scute expression. Results suggest that both h and ac act to induce the formation of temporally and spatially distinct phase of sensillar development.
Of all the HLH superfamily members, the h protein has the highest degree of similarity to the E(spl)HLH proteins.
On basis of ectopic eve expression experiments, it has been suggested that h is an indirect target of eve: h is down-regulated as an indirect response to ectopic eve expression.
Mutant analysis suggests that h is active in the wing in larval-adult metamorphosis with transcription pattern dependent upon position along the proximal-distal axis of polarity.
Apical localization of pair-rule transcripts restricts lateral protein diffusion allowing pair-rule proteins to define sharp boundaries and precise spatial domains.
Negative regulator that suppresses sensory neurogenesis by selectively repressing ac and sc gene expression in different spatial domains and at different developmental stages. Overexpression of h during pupal development has no effect on normal sense organ development. Where h expression is high ac expression is absent, h suppresses ac expression via a feedback mechanism on ac and sc activity and suppresses sensory organ formation. The interactions may involve specific dimerization reactions between different combinations of helix-loop-helix proteins.
DNA sequence analysis reveals four E box binding sites, for the binding of hetero-oligomeric complexes composed of da or AS-C proteins, in the first 877 bp of the ac upstream region. Electrophoretic mobility shift assays demonstrate that the emc protein can specifically antagonise DNA binding of the da/AS-C complexes in vitro in a dose-dependent manner, h and E(spl) proteins fail to exhibit this inhibitory effect.
The regulation of striped h expression in the early embryo has been studied.
Ectopic expression of h prevents initiation of Sxl expression by interfering with X chromosome counting.
Injection of protein synthesis inhibitors into early embryos induces expression of h mRNA in virtually all regions of the embryo.
The development of the eve and ftz stripes in h-, run-, eve- and en- embryos demonstrates that individual cells are allocated to parasegments with respect to the anterior margins of the eve and ftz stripes.
Genetic analysis demonstrates that h is dispensable for efficient homeotic gene expression in the visceral mesoderm.
An increase of ac doses in h- homozygous flies produces an increase in microchaetae density on the notum and wing. Above a maximum dose more doses of ac cause a reduction in microchaetae density in the notum but increase on the wing.
The pair-rule gene hairy regulates the development of alternate segments in the embryo as well as the spatial expression of another pair-rule gene fushi tarazu (Holmgren, 1984; Carroll et al., 1988; Rushlow et al., 1989). A later phenotypic expression of hairy, the adult bristle pattern, is established during larval and pupal stages (Nusslein-Volhard and Wieschaus, 1980; Ingham, Howard and Ish-Horowicz, 1985; Ingham et al., 1985). In the embryo, h mutations delete the posterior part of each odd-numbered segment, weak alleles deleting less than a whole segment and strong alleles deleting regions greater than one segment. In mutant adults, extra microchaetae are found along wing veins, L2 more so than L4 or 5 and on wing membrane; also on dorsal and ventral scutellum and top of head. Extra sensilla present on longitudinal wing veins in a gradient in which sensilla are concentrated proximally and hairs distally; intermediate structures found in the middle (Spivey and Thompson, 1984). Extra acrostichal row on either side of midline between dorsocentral bristles (Claxton, 1971); also occupy thin arch of cuticle connecting ventral scutellum and pleurae. Microchaetae found on mesopleurae (mean of 13 in males and 20 in females versus none in wild type) and pteropleurae (Murphy, 1972). Used by Garcia-Bellido and Ferrus (1975) to provide cuticular markers on pleurae for fate mapping. Additional hair-forming cells present in 19-hr pupa (Lees and Waddington, 1942). Autonomous expression in clones produced prior to the last eight hr of larval life; clones produced during the last eight hr before pupation exhibit normal phenotype; attributable to perdurance of wild-type gene product (Garcia-Bellido and Merriam, 1971). Reduced ac+ function as in ac3 or ac3/+ suppresses h phenotype; extra doses of ac+ enhance h expression and can render h partially dominant (Sturtevant, 1969; Botas, del Prado and Garcia-Bellido, EMBO J. 1: 307-10). Three doses of h+ suppress Hw (Botas, et al.). h expression also enhanced by combination with rearrangements that place the ac-sc region in juxtaposition with substantial quantities of heterochromatin (Green, 1960). Interactions with sc alleles detailed by Sturtevant (1969). h2 less severe than and partially complements h1 (Sturtevant, 1969). As with ci+, expression of h+ may be altered in the direction of h by rearrangements with breakpoints in the vicinity of the h locus (Dubinin and Sidorov, 1934); see also Jeffery, 1979. Unlike the ci case, however, rearranged h chromosomes do not show evidence of altered gene action (Stern, 1944).