novel - assembles germ plasm - a anterior/posterior determinant regulating embryonic development - RNA plays multiple noncoding roles to support oogenesis and maintain integrity of the germline/soma distinction.
Gene model reviewed during 5.47
Gene model reviewed during 6.04
Overlaps non-coding gene lncRNA:osk .
Gene model reviewed during 6.27
None of the polypeptides share 100% sequence identity.
Interacts with smaug (smg).
Click to get a list of regulatory features (enhancers, TFBS, etc.) and gene disruptions (point mutations, indels, etc.) within or overlapping Dmel\osk using the Feature Mapper tool.
Endogenous osk mRNA was visualized using molecular beacons. The in vivo dynamic behavior of osk was imaged over the entire oocyte in stage 7 to 10 oocytes, capturing the dynamics of osk from its nuclear export to localization at the posterior of the oocyte. osk mRNA is present in particles distince from stau protein for part of its transport and stable associates with stau protein near the posterior pole. osk mRNA oligomerizes as hundreds of copies forming large particles, which are necessary for long-range transport and localization.
osk expression at embryonic stages 1-4 is localized to the posterior pole of the embryo.
osk mRNA is initially concentrated in the oocyte and becomes localized to the posterior pole. It persists at the posterior pole through oogenesis and through the cleavage stages of embryogenesis.
From the earliest stages in oogenesis, osk RNA is enriched in the cell that will become the oocyte but is also present in nurse cells. At the early stages, osk RNA is distributed throughout the oocyte. By stage S8, enrichment at the anterior and posterior poles of the oocyte are apparent. After stage S9, and throughout early embryogenesis, osk RNA is strictly localized to the posterior pole. By the cellular blastoderm stage, osk RNA is no longer detected by in situ hybridization.
osk transcripts are first detected in the most mature regions of the germarium where they are present in all of the dividing cells. In stages S1-S6, osk RNA is present throughout the nurse cell-oocyte complex but is concentrated in the cell that will be the oocyte. During stages S8 and S9, osk RNA becomes localized to a cap at the posterior pole of the oocyte. After the striking posterior localization has occurred, osk transcripts accumulate to high levels in the nurse cells. In embryos, osk transcripts are localized to the posterior pole. They begin to disappear from the posterior pole by nuclear division 6 or 7 and very little localized osk RNA remains after the 9th nuclear division.
In stage 10 oocytes, vas protein, osk protein, and stau protein colocalize at the posterior pole. In early embryos, vas protein and osk protein localize to the polar granules but stau protein does not colocalize with them. It is present in a thin crescent apposed closely to the posterior cortex and disappears before the pole cell stage. A GFP-Vas fusion protein was used to determine the vas protein distribution.
GBrowse - Visual display of RNA-Seq signalsView Dmel\osk 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.
osk RNA dimerization loop base-pairing promotes co-assembly of RNA molecules. The presence of a palindromic sequence in the dimerization loop is not essential for posterior localization of full-length spliced RNA molecules.
Translation of localised osk mRNA is activated specifically through a discrete element located at the 5' end of the osk transcript. This element is only active at the posterior pole of the embryo and is only required when the transcript is repressed through the Bruno-response element (BRE), suggesting that it functions as a derepressor.
In a sample of 79 genes with multiple introns, 33 showed significant heterogeneity in G+C content among introns of the same gene and significant positive correspondence between the intron and the third codon position G+C content within genes. These results are consistent with selection adding against preferred codons at the start of genes.
Studies of fluorescently labelled osk RNA injected into wild type or mutant embryos reveal that microtubule-dependent cytoplasmic flows could contribute to the long range transport of osk RNA, whereas microtubule independent processes could mediate short-range transport.
Transport and early localisation activities of fs(1)K10, bcd and osk mRNAs are remarkably similar to each other suggesting the mRNAs interact with a common set of microtubule based motor proteins and associated factors.
One readily detectable protein with an apparent molecular weight of 80kD binds specifically to the nos mRNA 3' untranslated region (3'UTR), the protein is called aret. Binding assays demonstrate aret response elements (BRE) exist in the A, B and C region of osk 3' UTR. aret is required for preventing translation of osk mRNA prior to its localisation at the posterior pole of the oocyte.
Targeting of osk to the posterior pole involves two steps of spatial restriction, cytoskeleton-dependent localisation of the mRNA and localisation-dependent translation. Two isoforms of osk protein are produced by alternative start codon usage, the short isoform has full osk activity. When osk RNA is localised accumulation of osk protein requires the functions of vas and tud, as well as osk itself, suggesting a positive feedback mechanism in the induction of pole plasm by osk.
Microtubules are required for osk mRNA localisation in nurse cells and in the posterior oocyte.
Gene functions that are not required for the localisation of osk RNA affect the stability or perhaps translational initiation of osk protein. The osk 3'UTR can confer translational repression on a heterologous coding sequence and results suggest that osk RNA localisation is regulated by osk translation and the mechanism responsible operates through the osk 3' UTR. Full length osk protein functions to maintain osk RNA localisation and therefore support a positive feedback model.
The stau product associates specifically with both osk and bcd mRNAs to mediate their localizations, but at two distinct stages of development. stau protein is required to anchor bcd mRNA at the anterior of the egg, and is transported with osk mRNA during oogenesis.
Mutations of Pka-C1 cause similar mislocalisations of bcd and osk RNAs to those observed from N mutations. Mutations also severely disrupt the organisation of microtubules at the posterior of the oocyte at the time of bcd and osk localisation.
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.
A PCR based assay has been used to determine whether the encoded mRNAs exhibit changes in poly(A) status upon translational activation.
Different elements within the osk 3' untranslated region are necessary for distinct steps in the mRNA localization process: early movement into the oocyte, accumulation at the anterior margin of the oocyte, and localization to the posterior pole.
Mislocalisation of osk mRNA to the anterior of the oocyte is sufficient to direct formation of an abdomen and of functional germ cells at an ectopic site. Only vas and tud are essential for osk-induced pole cell and abdomen formation. The dosage of osk determines the final amount of components recruited and ultimately controls the number of pole cells formed.
Overexpression of osk leads to higher levels of osk mRNA that is both correctly localised to the posterior pole and unlocalised. Consequently nos is activated ectopically causing extensive shifts in body patterning. Germ cell formation is also affected, this can be enhanced by genetically decreasing nos activity.
osk is required for the correct positioning of nos product in the embryo.
Cloning and molecular characterization of osk reveals that osk mRNA is concentrated in the oocyte throughout most of oogenesis and it is specifically localized to the posterior pole soon after the oocyte begins to visibly differentiate. Full length or nearly full length osk protein is required to maintain the posterior localization of osk mRNA.
osk is required for the localization of the posterior signal.
Mutations in maternal anterior class gene osk do not interact with RpII140wimp.
osk expression patterns were investigated in egl embryos to determine the relationship between osk and egl.
Mature follicles are immunologically stained for asymmetric distribution of ecdysteroid-related antigen. During late oogenesis localisation of the antigen changes dramatically suggesting the antigen plays a role in early embryogenesis and, perhaps, in pattern formation.
In osk mutant females vas synthesis appears normal but the vas protein is not localized.
osk plays a role in polar granule formation.
An investigation of the role of gap genes in expression from Ubx and Antp promoters in the blastoderm embryo reveals that a unique combination of gap genes and pair rule genes is required for their initial activation.
Homozygous females normally viable and fecund; homozygous males fertile. Embryos produced by homozygous females lack pole plasm and fail to produce pole cells; abdominal region remains unsegmented and eventually dies. Temperature-sensitive period for the germ-line effect is the last six hours of oogenesis and for abdominal development the last twelve to fourteen hours (osk8). Homozygous osk germ cells autonomous in pole cell transplants. Polar cytoplasm from unfertilized eggs or normal embryos capable of rescuing pole cell formation if injected at the posterior extremity of the early embryo and abdominal segmentation, to the extent of producing viable but sterile adults, if injected into the posterior half of preblastoderm embryos. Embryos produced by homozygous BicD; osk females are indistinguishable from those produced by osk alone suggesting that osk+ product is required for the formation of bicaudal embryos; also required for the early anterior-posterior gradient of hb expression (Tautz, 1988).