|Feature type||allele||Associated gene||Dmel\sn|
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|Nature of the Allele|
|Mutations Mapped to the Genome|
|Associated Sequence Data|
|Nature of the lesion|
0.3kb deletion from 1184bp to 1475bp of the wild-type sequence. This deletion is in the 5' end of the gene, and the coding region is intact.
0.3 kb deletion in -0.9 to 0.0 kb; coordinates according to Roiha, Rubin and O'Hare (1988)
|Carried on aberration|
|Phenotype Manifest In|
microchaeta & actin filament
The number and density of spiked protrusions on the dendrites of class III ldaB neurons is reduced in mutant third instar larvae compared to wild type, while the total branch length of the dendritic tree is normal. The fraction of spiked protrusions that exceed 10 μm in length is increased in the mutant larvae.
Neurons cultured from sn/sn brains have a distinctive abnormal morphology. Axons curl, creating a filagree pattern. Filamentous axon distribution within these neurons is abnormal.
The wing hairs of sn3 mutants show a 12-14% reduction in length compared to wild-type hairs. Few actin bundles are present in transverse or longitudinal sections taken through sn3 hairs; rather, the actin filaments are present in an almost diffuse cortical layer.
The bristles of sn3 mutants are twisted; bristles can twist either to the right, to the left, or first in one direction and then the other. These mutant bristles have large gaps between flutes, reflecting abnormal distribution of the actin bundles. Apart from where twisting occurs, the curvature of sn3 bristles is similar to wild type. Additionally, sn3 mutant bristles lie flat over the surface of the thorax, instead of pointing away from the thorax, as in wild type.
sn3 adults exhibit bent and twisted bristles of normal length. This phenotype is more pronounced in macrochaetes than microchaetes. Each macrochaete flute is not equally spaced nor equal in size and is twisted. Particularly in the lower half of the bristle, a honeycomb of short ridges 5-10υm in length is found, most of which is connected to a major longitudinal ridge. Overall, the ridges and valleys have a collective longitudinal orientation and continuous ridges of over 50υm in length and are common on most bristles, especially near the tip.
The longitudinal actin bundles of wild-type bristle cells are composed of a hexagonally-packed array of actin filaments that form a triangular shape at the plasma membrane. sn3 mutants lack the fascin cross-bridges that usually form between actin filaments within a bundle. The longitudinal bundles of sn3 bristle cells contain fewer filaments than wild type; these filaments are liquid ordered not hexagonally-packed. These defects cause the bundles to form a rectangular shape that does not extend as far into the cytoplasm as the wild-type triangular bundle.
The arista laterals are shorter than normal and weakly curved in mutant flies.
Actin bundles in the bristles of heterozygous flies are comparable in number and size to wild type and the area occupied by the filaments is not significantly different from wild type. The filaments are hexagonally packed. The bristles are the same length as in wild-type flies. Bristles of homozygotes are shorter than wild type.
Strong bristle phenotype.
Mutation causes a severe denticle phenotype. Denticles tend to be smaller and have thinner hooks than wild-type denticles. They are also less orderly along each row and sometimes have a floppy appearance.
Macrochaetae are bent, gnarled, twisted and considerably shorter than in wild-type flies. Microchaetae are often irregularly bent, and are shorter and less rigid than in wild-type flies. The ridges and valleys on the surface of the microchaetae are distorted. Actin bundles within the bristle cells are smaller and flatter than normal, and the filaments within them are disordered.
Bristles are gnarled due to disrupted actin filament bundles.
Extreme bristle phenotype.
Extreme bristle phenotype, female fertile.
class 3 - female fertile with gnarled macrochaetae and kinky microchaetae
|NOT Enhancer of|
|NOT Suppressor of|
|Phenotype Manifest In|
|NOT Enhanced by|
|NOT suppressed by|
|NOT Enhancer of|
|NOT Suppressor of|
ebo sn double mutants exhibit differences in the appearance of the ellipsoid and fan-shaped bodies, compared to wild-type and exhibit behavioral defects as found in ebo single mutants. The ellipsoid body defect is clearly visible in 100% of the animals but is more variable, ranging from just open at the bottom, to totally dissociated into two lumps of neuropil. No correlation is observed between the severity of the structural and behavioral defects in ebo sn gynandromorphs. Of those gynandromorphs in which the central complex can be distinguished, roughly half exhibit abnormal ellipsoid bodies and behavioral defects. Mutant yaw torque activity and torque spike frequency is found in about 39% and 64% of ebo sn gynandromorphs.
The denticles of m1, sn3 mutants show splitting in addition to the defects seen in either single mutant. sn3, m1, f36a triple mutants have small, highly misshapen denticles that are more affected than those of m1, f36a or m1, sn3 double mutants. sn3, m1, f36a; shaV15 and sn3, m1, f36a; WASp3 quadruple mutants show further impairment to denticle formation compared to sn3, m1, f36a triple mutants, with mutants exhibiting regions of naked cuticle where denticles lie in wild-type animals. The dorsal hairs on the abdominal segments of sn3, m1, f36a triple mutants are severly reduced in size, and in some cases, hairs are abrogated leaving abnormal naked regions. This phenotype is more severe in sn3, m1, f36a; WASp3 quadruple mutants and is even more severe in sn3, m1, f36a; shaV15 mutants in which most dorsal hairs are absent, leaving naked cuticle.
sn3, f36a double mutants have bristles that are short, like f36a mutants, and twisted, like sn3 mutants.
In f36a sn3 double mutants, bristle ridges of length more than 10υm (45% of wild-type length) are not found. Instead, a variety of short ridges 3-10υm in length are found. Some of these are parallel to the longitudinal axis of the bristle, whereas others are perpendicular or oblique. These ridges are seldom connected to one another but terminate freely on the surface.
In f36a, sn3 double mutants, bristle cells contain tiny rafts of membrane-attached actin filament clusters, which consist of a monolayer of filament. This is a more extreme phenotype than that observed with either of the single mutants. When these f36a, sn3 mutant cells are treated with jasplakinolide, large clusters of actin filaments appear internally, most of which run parallel to the longitudinal axis of the bristle. These clusters have an irregular shape and have a liquid ordered packing of filaments, instead of wild-type hexagonal packing.
sn3 f36a double mutants have ocellar bristles which are shorter and have a smaller volume than normal.
The arista lateral phenotype of sn3 f36a double mutants is not substantially stronger than either single mutant. Double mutant arista laterals are thinner than wild type. At a low frequency, branched laterals are seen. The mutant laterals start to extend at the normal time, but their rate of extension is slower than normal.
|Complementation & Rescue Data|
|Not rescued by|
Scer\GAL4[hs.PB]-driven expression of sn[Scer\UAS.P\T.T:Avic\GFP-EGFP] fully rescues the gnarled bristle phenotype exhibited by sn mutants. Scer\GAL4[hs.PB]-driven expression of sn[S52A.Scer\UAS.P\T.T:Avic\GFP-EGFP] fully rescues the gnarled bristle phenotype exhibited by sn mutants. Scer\GAL4[hs.PB]-driven expression of sn[S52E.Scer\UAS.P\T.T:Avic\GFP-EGFP] fails to rescue the gnarled bristle phenotype exhibited by sn mutants.
|Stocks ( 89 )|
|Notes on Origin|
Mohr, 11th June 1922.
|External Crossreferences & Linkouts|
|Synonyms & Secondary IDs ( 1 )|
|Secondary FlyBase IDs|
|References ( 34 )|
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|Recent research papers ( 2 )|