TGFß homolog - EGF-R ligand - required for anterior-posterior and dorsoventral patterning of the egg and embryo - Syntaxin A1 is associated with the Golgi membrane and is required for the transportation of Grk-containing vesicles along the microtubules to their dorsal anterior destination in the oocyte
Gene model reviewed during 5.39
Gene model reviewed during 5.50
There is only one protein coding transcript and one polypeptide associated with this gene
Interacts with cni.
Click to get a list of regulatory features (enhancers, TFBS, etc.) and gene disruptions (point mutations, indels, etc.) within or overlapping Dmel\grk using the Feature Mapper tool.
grk transcripts are localized at the oocyte posterior until oogenesis stage S7 at which point they become detectable along the entire anterior cortex of the oocyte and enriched on the presumptive dorsal side. During stage 8, accumulation along the ventral-anterior cortex decreases and by stage 9, grk transcripts are confined to the dorsal -anterior region of the oocyte.
In mid-stage oocytes, grk expression is restricted to the future dorsal-anterior corner of the oocyte overlying the oocyte nucleus.
grk mRNA is primarily enriched along the oocyte dorsal cortex at oogenesis stage S9, with less mRNA adjacent to the nuclear membrane.
Transcript as detected by in situ hybridization and injection of labeled grk RNA into cultured oocytes show that at stage 8 grk transcript is localized in an anterior ring and by stage 9 the transcript has been concentrated in the dorsoanterior region of the oocyte. A less enriched concentration of grk transcript can be detected in the ventral anterior region of the oocyte. Videomicroscopy showed that this localization occurs in a 2 step process in which the transcript first moves anteriorly and then is concentrated dorsally.
Transcript is localized in the posterior of stage 6 oocytes and relocalizes to the anterior of stage 8 oocytes. Further refinement of transcript localization to the anterodorsal corner of the oocyte is observed in stage 9-10 oocytes.
grk transcripts are first detected in region 2B of the germarium. In oogenesis stages S1-S7, transcripts are predominantly found in a crescent lining the posterior end of the oocyte. During oogenesis stages S8 and S9, transcripts become localized to the dorsal-anterior corner of the oocyte nucleus. In fs(1)K10, sqd, spir, and capu mutants, grk transcripts are no longer restricted to the dorsal side of the oocyte at later stages of oogenesis but are also abundant along the anterior margin of the oocyte. In Egfr and cni mutants, the grk transcript distribution is unaffected.
Transcripts are undetectable by northern blots in grk2B6 mutant RNA or by in situ in mutant egg chambers.
grk transcripts are detected at very low levels on northern blots in grk2, grk3, and grk4 mutants. No transcripts are detected in egg chambers of these mutants.
grk begins to accumulate in the anterodorsal cortex of the oocyte in close association with the oocyte nucleus at oogenesis stage S7, where it remains through late stage 9. No protein is observed on the side of the oocyte nucleus facing the center of the oocyte.
Protein is detected in the anterodorsal corner of stage 10 oocytes.
grk protein is detected starting in early oogenesis, in germarium region 2b. Like grk transcript, grk protein localizes to the oocyte in early egg chambers, and starting at stage S8, becomes localized to the future dorsal cortex of the oocyte. At stage S10-S12, the grk protein localization differs from grk transcript localization. grk protein forms an elongated anterior-posterior stripe over about half the length of the oocyte\'s dorsal midline.
GBrowse - Visual display of RNA-Seq signalsView Dmel\grk 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.
Production of grk in the nurse cells is sufficient for axis determination in the Drosophila oocyte.
Different dorsal follicle cell fates are not determined by a grk morphogen gradient. They are specified by secondary signal amplification and refinement processes that integrate the grk signal with positive and negative feedback mechanisms generated by target genes of the Egfr pathway.
The secretion of grk requires its transmembrane region, but is not necessary for its biological activity.
Posterior localisation of grk mRNA in the early oocyte is essential for proper A/P axis formation.
grk plays a role in the development of follicular epithelium by cooperating with brn for the Egfr-dependent migration of the prefollicular cels around each nurse cell-oocyte complex. brn may help provide specificity to and/or facilitate the multiplicity of grk-Egfr functions during oogenesis.
The distribution pattern of grk protein in wild-type ovaries and in ovaries from a number of dorsal ventral patterning mutants is analysed.
grk is required for the induction of both posterior and dorsal follicle cell fates.
Mutations in grk cause a ventralized phenotype in egg and embryo. Changing grk dosage in otherwise wild type ovaries is sufficicent to alter the number of somatic follicle cells directed to the dorsal fate. The grk-Egfr signalling process plays an instructive role in oogenesis, inducing dorsal cell fates in the follicle cell epithelium and controlling the production of maternal components that will direct the embryonic dorsoventral pattern.
grk, unlike other localized cytoplasmic determinants, is not directly responsible for the establishment of cell fates along a body axis, but restricts and orients an active axis-forming process which occurs later in the follicular epithelium or in the early embryo.
Molecular analysis of grk suggests that it is the Egfr ligand functioning in the female germline in dorsoventral patterning.
Mutations at the grk locus cause defects in midoogenesis. Double mutant analysis indicates that rho acts upstream of Tl in dorsal-ventral axis formation, and the action of rho requires the grk-Egfr signaling pathway.
Germ line mosaic analysis demonstrates that the grk gene product is required in the germline for chorion patterning and embryonic patterning.
maternal-effect lethal. Wild-type allele required for normal dorsoventral pattern in the egg. In mutants, the ventral regions of the chorion and the embryo are expanded at the expense of the dorsal regions. The pattern of the chorion is altered, a second micropyle and a small patch of operculum-like material often forming at the posterior pole in extremely mutant eggs; fewer cells contribute to the dorsal appendage, which is usually shifted posteriorly, but more follicle cells contribute to the main body of the chorion. In the embryo the major increase in cell mass occurs in the mesoderm as an invagination on the ventral side during early gastrulation. Analysis of mosaic females in which germ cells and sister nurse cells are of different genotype indicate that grk mutations act only in the germ line.