|Feature type||allele||Associated gene||Dmel\scrib|
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|Nature of the Allele|
|Mutations Mapped to the Genome|
|Associated Sequence Data|
|Nature of the lesion|
|Phenotype Manifest In|
Homozygous scribunspecified mutant clones in the larval eye imaginal discs form benign lesions in the adult eye. Clonal areas in such eyes appear undifferentiated and disorganised. Neuronal differentiation is severely impaired in scribunspecified mutant clones. Homozygous scribunspecified mutant clones in the eye imaginal disc grow into sizable clones of disorganised appearance and do not express neuronal markers, indicating their failure to differentiate. Homozygous scribunspecified mutant clones contribute only 12.4% of the eye-antennal imaginal disc, while wild-type clones of the same size contribute 41.2%. Consistently, the number of apoptotic cells in the clonal fraction is significantly increased (16.6% in the mutant compared to 2% in wild-type).
The cells in the larval fat body are more rounded than normal.
Embryos that are maternally and zygotically mutant for scrib produce a corrugated cuticular surface that is riddled with holes. The embryos proceed normally through precellular development and the epithelial blastoderm forms as in wild type. After gastrulation however, the organisation of the ectodermal epithelium is disrupted as cells lose their columnar shape and planar arrangement. These defects become progressively more severe as development proceeds. The epidermis of late embryos is frequently interrupted and consists of groups of irregular rounded cells that are separating from one another. Most of the epidermis is organised into multilayered strips or tubes of cells that have lost contact with the underlying tissue.
Clones of follicle cells homozygous for scribunspecified become round and multilayered with polarity defects (in contrast to the regular monolayered follicle epithelium seen in wild type). These epithelial defects are cell autonomous. Most homozygotes hatch and survive into late larval stages.
|Phenotype Manifest In|
Expression of hepAct.Scer\UAS in scribunspecified mutant clones under the control of Scer\GAL4Act5C.PI suppressed the scribunspecified phenotype to revert to an essentially wild-type appearance, without the marked lesions resulting from scrib-deficient tissue. Significantly, these phenotypically rescued eyes do not contain any clonal cells, suggesting that JNK activity (increased by expression of hep) counteracts the outgrowth of scribunspecified tissue or causes the removal of the mutant cells. These eyes are the same size as wild-type. Downregulation of JNK signaling in clones of scribunspecified mutant tissue by overexpression of bskK53R.Scer\UAS suppresses apoptosis (from 16.6% to wild-type levels of 25%) and increases the overgrowth of the tissue, even compared to wild-type, resulting in scribunspecified bskK53R.Scer\UAS clones contributing over 70% of the tissue in third instar eye imaginal discs. Clones of eye imaginal discs that express phlScer\UAS.F179 autonomously (under the control of Scer\GAL4Act5C.PI) in scribunspecified clones grow into massive and invasive tumours during larval stages, resulting in 80% of animals not pupating and dying as giant larvae. Expression of hepAct.Scer\UAS in eye imaginal disc clones that express phlScer\UAS.F179 (under the control of Scer\GAL4Act5C.PI) and scribunspecified results in adult eyes with massive overgrowth. The heads are significantly bigger and the retina of these mutants are dramatically larger than that of a wild-type eye. In many cases, the retina is folded and bunched to accommodate the surfeit of tissue. These severely hyperplastic eye structures are well patterned and show a distinctive ommatidial organisation. The tumourous overgrowth is induced non-autonomously in the wild-type cells surrounding the hepAct.Scer\UAS phlScer\UAS.F179 (both under the control of Scer\GAL4Act5C.PI) scribunspecified cells.
Marked clones in the eye disc expressing Ras85DV12.Scer\UAS under the control of Scer\GAL4Act5C.PI and which are also homozygous for scribunspecified show metastatic behaviour; third instar larvae carrying these marked clones have large primary tumours in the head and also have small groups of cells floating in the hemolymph and other distant sites. The majority of ectopic tumour cells spread from the primary tumour onto the ventral nerve cord (VNC), eventually enveloping it and also spread into the first and second leg discs and tracheal vasculature at a lower frequency. The mutant cells can invade the inside of the VNC and the leading edge of the cells has a morphology common to actively migrating cells. The basement membrane has many points of discontinuity in eye discs containing clones which are homozygous for scribunspecified and which are expressing Ras85DV12.Scer\UAS under the control of Scer\GAL4Act5C.PI, and mutant cells spread from these areas. The metastatic behaviour seen in marked clones in the eye disc which are homozygous for scribunspecified and are also expressing Ras85DV12.Scer\UAS under the control of Scer\GAL4Act5C.PI is suppressed if they are co-expressing scribScer\UAS.cBa.
Homozygous embryos that are also heterozygous for dlg1unspecified die before hatching, with defects evident in dorsal closure. Embryos lacking zygotic scrib and l(2)gl function die exhibiting phenotypes that are similar to the absence of maternal and zygotic scrib or l(2)gl function. The imaginal disc phenotype of scribunspecified hypomorphic larvae is enhanced by heterozygosity for l(2)glunspecified.
|Complementation & Rescue Data|
|Stocks ( 0 )|
|Notes on Origin|
|External Crossreferences & Linkouts|
|Synonyms & Secondary IDs ( 1 )|
|Secondary FlyBase IDs|
|References ( 7 )|