transcription factor - homeodomain - Antp class - HoxA3, HoxB3 and HoxD3 homolog - DV polarity - The absence of the amnioserosa in mutants might cause the germ band to be twisted and thrown into folds during an abortive elongation process
Gene model reviewed during 5.49
Gene model reviewed during 5.50
There is only one protein coding transcript and one polypeptide associated with this gene
353 (aa); 39 (kD predicted)
Click to get a list of regulatory features (enhancers, TFBS, etc.) and gene disruptions (point mutations, indels, etc.) within or overlapping Dmel\zen using the Feature Mapper tool.
Comment: reported as procephalic ectoderm anlage in statu nascendi
Comment: reported as procephalic ectoderm anlage in statu nascendi
Reporter constructs with deletions of 1.6 kb of zen upstream region driving lacZ expression demonstrate that a ventral repression element lies at about -1.2 to -1.4.
Northern analysis of RNA from 0-24 hour embryos indicate that zen transcript is expressed in early embryos, and that expression peaks at 2-3 hours of embryogenesis. Using radioactive in situ hybridization, zen expression is detected in the dorsal surface and the anterior and posterior poles of embryonic cycle 14 embryos. By gastrulation, zen expression is restricted to the dorsal surface. During germ band elongation, zen transcript is detected in the amnioserosa and a region of the dorsal ectoderm corresponding to the presumptive optic lobe, and in a subset of pole cells within the posterior midgut invagination.
The zen-RA transcripts are detected along the dorsal surface in embryos following the formation of the syncytial blastoderm. Following gastrulation, the expression of zen-RA is limited to a 5-6 cell wide stripe along the dorsal surface, and is not detected in the posterior 20% of the embryo.
GBrowse - Visual display of RNA-Seq signalsView Dmel\zen in GBrowse 2
Please Note FlyBase no longer curates genomic clone accessions so this list may not be complete
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.
Source for identity of: zen CG1046
DNApol-α180 and mus209 are negatively regulated by zen protein. This repression is mediated by the DRE (DNA replication-related element) sites in the DNApol-α180 and mus209 promoters. The amount of Dref is reduced in transfected Kc cells expressing zen, suggesting that zen represses expression of DNA replication-related genes by reducing the amount of Dref.
A minimal 110bp Ventral Repression Element silencer in the zen promoter contains two dl binding sites as well as binding sites for additional nuclear factors present in early embryos. Mutations in the latter convert the minimal VRE into an enhancer, mediating transcriptional activation in ventral regions in response to dl.
dl binding sites from the zen promoter can mediate transcriptional activation of a heterologous promoter, but not repression. T-rich sequences close to the dl binding sites in the silencer region of the zen promoter are conserved between D.melanogaster, D.virilis and D.pseudoobscura.pseudoobscura.
The homologs of Antp, ftz, Scr, Dfd, Ama, bcd, zen, pb and lab, but not zen2 are all present in D.pseudoobscura.pseudoobscura, in the same linear order and similarly spaced along the chromosome as in D.melanogaster.
Comparative analysis of the homeobox sequences reveals the subdivision of the Antp-type homeobox genes into three classes early in metazoan evolution, one includes Abd-B, the second includes abd-A, Ubx, Antp, Scr, Dfd and ftz, and the third includes zen, zen2, pb and lab.
zen alleles display relative phenotypic strengths, this may be correlated to the progressive loss of dorsal pattern elements in the ventralised mutants.
zen expression assayed in embryos from females expressing dl-lacZ fusion proteins compared to wild type dl. Consistant with degree of dorsalization, domain of zen expression is expanded laterally.
dl binding site domain exchange experiments, using Ecol\lacZ reporter gene constructs, between the zen and twi promoters demonstrate that dl is intrinsically an activator and that repression requires additional factors present in the distal region of the zen promoter, the VR.
The zygotically acting DV genes repress ac expression within specific DV domains.
dl is a sequence specific DNA binding protein that may mediate long range repression by interacting with the distal regions of the zen promoter.
Mutations in zygotic dorsal class gene zen do not interact with RpII140wimp.
zen has altered pattern of expression in ventralized and lateralized embryos. In dorsalized embryos zen expression refines at stage 5. Polar expression of zen requires genes of the terminal group. zen is required for the normal ontogeny of the zen pattern and fating of the amnioserosa.
Mutations result in loss of several dorsally derived embryonic structures, disruption of germ band extension and disruption of head involution. Optic lobe and the amnioserosa are most sensitive to loss of zen+ activity. Analysis of a temperature sensitive allele demonstrates the time of zen function is from 2--4 hours of embryogenesis.
Involved in the regulatory hierarchy responsible for the asymmetric distribution and function of zygotic regulatory gene products along the DV axis of early embryos.
The zen promoter shows a two-tier organization: distal sequences mediate its initial response to maternal factors, whereas proximal sequences are responsible for the refinement of the pattern in older embryos. The distal element has the property of a silencer (or anti-enhancer). The proximal element may interact with factors that may be modulated by a cell-cell communication pathway.
A transient expression assay has been employed to investigate the potential of homeobox genes to function as transcriptional activators.
P element mediated transformation experiments demonstrate that zen alone can provide zen+ gene function. This suggests that the neighbouring zen2 gene may be dispensable.
Null mutations result in embryonic lethality and the loss of several dorsally derived embryonic structures, including the amnioserosa, optic lobe and dorsal ridge. These animals also fail to fully extend their germ bands and go through the process of head involution. Hypomorphic mutations result in the absence of dorsal structures but do undergo normal gastrulation movements. A temperature-sensitive allele has been used to define the time of zen+ action between 2 and 4 hours of embryogenesis, just prior to and overlapping the earliest observable morphogenic defects. X-ray induced somatic clones have further shown that zen+ function is unnecessary for postembryonic development. The RNA product of zen is first detected at about 2 hours of development during the eleventh to twelfth cell cycle of the syncytial blastoderm. At this early stage the RNA is found on the dorsal surface of the embryo extending around the anterior and posterior poles. As cellularization proceeds and the early events of gastrulation begin, the RNA becomes restricted to a mid-dorsal stripe of cells. These cells have been fate mapped and give rise to the amnioserosa and the lobes in the dorsal posterior of the embryonic head, i.e., the structures absent in zen- animals. The time of appearance of zen RNA also correlates nicely with the temperature-sensitive-period data obtained using the conditional allele. Antisera to the zen protein product has been used to follow its accumulation pattern and this analysis agrees with and expands the in situ results. The protein is located in the nuclei of cells expressing the gene and at cellular blastoderm is found in a mid-dorsal stripe seven cells wide and seventy cells in length. During gastrulation these cells eventually give rise to the amnioserosa, the optic lobe and dorsal ridge; these structures continue to show zen protein accumulation until the end of germ-band extension at about 4 to 6 hours of development. This end point also correlates well with the end of the temperature-sensitive period of the conditional allele. The spatial pattern of zen expression has been shown to be dependent on the products of several of the maternally expressed genes which specify the anterior-posterior and dorsal-ventral polarity of the embryo, and zen would appear to lie near the end of the axis-determining pathway.
The name for the locus derives from the characteristic 'wrinkled' appearance of the germ band seen in the SEM at the time of normal germ-band retraction.