sSpi, s-spi, l(2)01068, l(2)s3547
ligand for Epidermal growth factor receptor - Egf/Tgf alpha homolog - required for the differentiation of all ommatidial cell types, with the exception of R8 - Spi is found on retinal axons that project into the lamina; this transported Spitz is required for lamina cartridge neuron differentiation
Annotated transcripts do not represent all supported alternative splices within 5' UTR.
Gene model reviewed during 5.48
2.5, 2.0 (northern blot)
230 (aa); 26 (kD)
Interacts with Star via the lumenal domain.
Proteolytic processing by Rhomboid occurs in the Golgi. Cleavage takes place within the transmembrane domain close to residue 144 and the active growth factor is released.
N-glycosylated and O-glycosylated.
Click to get a list of regulatory features (enhancers, TFBS, etc.) and gene disruptions (point mutations, indels, etc.) within or overlapping Dmel\spi using the Feature Mapper tool.
Comment: reported as head epidermis primordium
Comment: reported as head epidermis primordium
Comment: reported as dorsal/lateral sensory complexes
spi is expressed in small diploid cells located basally in the epithelium, which are likely intestinal stem cells.
Expression of spi is highest in cone cells and bristle organules (interommatidial bristle precursors), and lower in the primary pigment cells.
GBrowse - Visual display of RNA-Seq signalsView Dmel\spi 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.
spi is not required for patterning of the dorsal anterior follicular epithelium.
Area matching Drosophila EST AA201448. This EST forms a 856bp contig with ESTs AA438721 and AA247046.
rho protein appears to be an intramembrane serine protease that directly cleaves spi protein. The putative rho active site is within the membrane bilayer and the spi cleavage site is within its transmembrane domain.
Two EMS induced alleles were identified in a screen for mutations affecting commissure formation in the CNS of the embryo.
hh and spi bring about the concerted assembly of ommatidial and synaptic cartridge units, imposing the "neurocrystalline" order of the compound eye onto the post-synaptic target field. spi activity is necessary and sufficient for the differentiation of cartridge neurons in the lamina.
spi is required in follicle cells for dorsal-anterior patterning of the egg.
Epistasis tests with known dorsal/ventral patterning genes suggests that CrebA encodes a transcription factor near the end of both the dpp and spi signalling cascades to translate the corresponding extracellular signals into changes in gene expression.
In vivo culture of mutant discs from genotypes that are normally embryonic lethal demonstrates spi has no role in wing disc growth.
Facilitating the expression of spi, rho and S is the only sim-dependent contribution of the midline to patterning the ventral ectoderm, since the mutant sim ectodermal defects can be overcome by expression of secreted spi in the ectoderm. These results suggest a mechanism for generating a graded distribution of secreted spi, which may subsequently give rise to graded activation of Egfr in the ectoderm.
In salivary gland development the activity of fkh prevents the expression of duct-specific cells, and in preduct cells the spi group signalling pathway prevents the expression of gland specific markers. fkh is repressed by spi group signalling, which is strongest in the most ventral cells of the epidermis.
The spi product triggers the Egfr signaling cascade. Graded activation of the Egfr pathway may normally give rise to a repertoire of discrete cell fates in the ventral ectoderm and graded distribution of spi may be responsible for the graded activation. The rho and S products may act as modulators of Egfr signaling. Epistatic relationships suggest that rho and S may normally facilitate processing of the spi precursor.
spi is required for photoreceptor determination; mutations modify the phenotype caused by ectopic expression of rho in the eye. Mosaic analysis suggest spi produces a diffusible signal during ommatidial development. Other members of the spi group and Egfr also interact with rho, in a pattern that suggests a model in which rho can act as a mediator of a ligand-receptor interaction between spi and Egfr in the developing eye.
Required for normal development of blastoderm cells just lateral to the ventral mesodermal precursors. spi+ required in the female germ line; spi- pole cells transplanted into normal embryos produce no progeny.
Embryonic lethal. Denticle bands narrower than normal; first row often missing; reversal of polarity between anterior and posterior rows not seen; irregular fusion in midline of adjacent dentical bands. Keilin's organs missing or strongly reduced. Labrum, antennal-maxillary complex and labial sense organ reduced in size; right and left halves of head skeleton fused to produce pointed appearance. Tail region normal. Right and left halves of ventral ganglia of the central nervous system closer together than normal resulting in shorter commissures. The cells in the CNS that stain with anti-eve+ antibodies are closer together in spi- than in wild type.
spi gene product is required for the proper development of the ventralmost cuticle and the CNS midline.