larval NMJs have fewer synaptic boutons than controls. Fas2EB112
/+ NMJs have no change in bouton number compared to controls.
Anterior follicle cells in homozygous follicle cell clones undergo normal cell shape changes during oogenesis.
adults display a rough-eye phenotype. Ommatidial photoreceptor and cone cell numbers are disrupted, and in some cases mini-clusters of ommatidia are observed.
mutant eye clones show cone cell defects, defects in photoreceptor cell number, and mini-ommatidia are observed.
mutant clones in eye disc display abnormal elav
-positive cell clusters between ommatidia which resemble R7-like photoreceptor cells. Some of the cells associated with the ectopic clusters are genotypically wild-type. No R8 photoreceptor cells are associated with the ectopic cell clusters.
Loss of function clones of Fas2EB112
in the adult notum display one or more ectopic dorsocentral bristles. other macro- and microchaetae are largely unaffected. Extra sensory organ precursor cells are observed in Fas2EB112
homozygous adults generally have normal mushroom body lobes, but occasionally have a misdirected alpha lobe. Fas2EB112
transheterozygotes do not have mushroom body lobe defects in the adult.
There are no obvious abnormalities in the timing and dynamics of the myopodia-filopodia interactions to form the synaptic contact site in Fas2EB112
/Y embryos. In these mutants, T-shaped presynaptic terminals of normal size form in the prospective synaptic site along the proximal edge of target muscle 12.
mutants exhibit amorphous and expanded tracheal tubes, where the luminal chitin does not organise correctly, in comparison to wild-type
The motor neuron that innervates DLMa has a higher number of contact points with the muscle in Fas2e76
mutants (6) than in wild type (5). The DLMa is 11% longer in Fas2e76
mutants than wild type. Investigation of adult innervation pattern in Fas2e76
mutants shows that outgrowth of secondary branches is not affected, but that branch elaboration, which occurs at 18-24 hours APF, is affected. During this stage, the average length of Fas2e76
secondary branches is increased, as is the area occupied by the higher order arbors of the secondary branches. Additionally, a higher level of secondary branches are stabilized, as shown by staining for futsch
, in Fas2e76
mutants at 24 hours APF than wild type.
mutants exhibit normal axon patterns. There are sporadic single BM axon defects, but no OP axon alterations are found.
In a Fas2EB112
mutant background, U motorneuron growth cones exhibit a wide shape that is reminiscent of aCC/RP2 pioneer growth cones.
In stage 14 Fas2EB112
mutants, the lumenal chitin in the developing dorsal trunk of the tracheal system fails to form a filamentous cable running along the tube length, as in wild-type, but instead is amorphous and fills the lumen.
homozygotes, the border follicle cells lose their polarity. Delamination of these cells is delayed, but their migration is accelerated.
Mutant embryos develop long and convoluted tracheal dorsal trunks and the apical cell surface of the dorsal trunk cells appears elongated and expanded. Tubular dilations are seen in the transverse connectives and the lumen of several tracheal branches is discontinuous.
During the first 28hr of wild-type larval life, the frequency of suprathreshold synaptic drive to aCC/RP2 increases considerably. In the absence of Fas2
, such as in Fas2EB112
, the frequency of synaptic drive to aCC/RP2 still increases during this period, although this increase is significantly less than when Fas2
is present. In Fas2EB112
mutants the number of presynaptic terminals that contact aCC remains unchanged. The ultrastructure of the presynaptic terminals at this stage is qualitatively indistinguishable from those that develop in wild-type.
The initial growth of the pioneer mushroom body (MB) axons is not disturbed in mutants. After converging at the protocerebral neuropil, the MB axons exhibit a normal medial turn and from the primordial medial lobe. When homozygous mutant clones are made in the MB, the axon projections exhibit no gross abnormalities. However dispersed axonal fascicles are seen in 23% of cases, in which axon bundles are randomly scattered throughout the axonal layers of the peduncle and lobes.
/+ embryos have normal axon guidance.
Larvae successfully hatch and begin crawling around but within hours begin to behave sluggish and uncoordinated, they ultimately stop moving and die. Synapses form and mature but in the absence of Fas2
they do not grow and then retract, the number of boutons drops to a few or zero.
Transheterozygotes with Fas2e76
exhibit missing postvertical, ocellar, vertical and orbital bristles. At 17o
C the phenotype is more penetrant with missing ocelli. Gynandromorph mosaics demonstrate hemizygous male regions fail to differentiate the postvertical, ocellar and vertical bristles and still have some orbital bristles. Ocelli are missing and the compound eye has a rough phenotype. Some macro- and microchaetes in the thorax are missing.
EM analysis of the extent of fasciculation and membrane apposition between various pairs of axons reveals normal neurite outgrowth, extension and guidance in embryos. Some aspects of selective fasciculation and axon-glia interactions appear highly abnormal, the vMP2, MP1 and FN3 pathways defasciculate. Scer\GAL4
driven expression of Fas2
can refasciculate the FN3 axons.
Transheterozygotes for Fas2EB112
are sterile. Increased branching of wing sensory axons in discs during metamorphosis. Ectopic sensory neurons are displayed in the wing.
The MP1 pathway does not form in Fas2EB112
mutant embryos: at embryonic stage 12/1 the dMP2 and MP1 growth cones do not turn posteriorly (which happens in the wild-type) but rather project laterally for a short distance. Also, the vMP2 growth cone often turns anteriorly (as in the wild-type) but already shows variability in the precise orientation of its tip. The MP1, dMP2 and vMP2 growth cones stay stalled in the same position through to stage 14 in mutant embryos, in contrast to the wild-type.