DAAMEx68 mutant larvae develop small muscles, as compared to controls.
The ISNb nerve terminals in DAAMEx68 mutant embryos often show guidance defects and premature terminations, as compared to controls.
The larval neuromuscular junctions at muscles 4 and 6/7 in DAAMEx68 hemizygous males are significantly smaller, display significantly fewer synaptic boutons and significantly fewer synaptic vesicles, but do not show actin organization defects nor obvious active zone or T-bar defects, as compared to controls; the enervated muscles, however, do not show significant size defects, as compared to controls. DAAMEx68 heterozygous females, however, do not show defects in synaptic bouton number compared to controls.
The larval muscle 4 neuromuscular junctions in DAAMEx68 hemizygous males expressing DAAMUAS.cMb under the control of Scer\GAL4btl.PS larvae show fragmented/absent presynaptic microtubules bundles and 'bouton fusion', as compared to controls. Synaptic transmission across this junction show a significant decrease in evoked excitatory junction current amplitude, but do not show significant changes in evoked excitatory junction current frequency or in miniature excitatory junction current amplitude, as compared to controls.
The tracheal dorsal trunk of DAAMEx68 homozygous stage 17 embryos exhibit heterogeneous patterns of hardly detected taenidial folds and thin F-actin bundles with stretches of perpendicular structures followed by stretches of parallel structures when compared to controls.
Single cell DAAMEx68 mutant mushroom body clones in a DAAMEx68/+ mutant background display a wild type morphology with a single bifurcated axon.
DAAMEx68 mutant neuroblast clones in a DAAMEx68/+ mutant background display abnormal axonal morphology in the mushroom bodies.
The body size and somatic musculature of early DAAMEx68 third instar larvae appear normal, but late third instar larvae (100 hours after egg laying) are shorter than normal and have slight muscle defects (muscles are smaller than normal, some myofibres are split and their general organisation is looser than in wild type). Muscle VL3 is reduced in both length and width, due to both sarcomere shortening and a reduction in sarcomere numbers.
Motility of mutant early third instar larvae is normal, but mutant late third instar larvae have significantly reduced motility compared to wild type.
Cultured primary neurons derived from DAAMEx1/DAAMEx68 embryos show a significant reduction in the number of filopodia compared to control neurons.
DAAMEx68 homozygous mutant embryos display subtle defects in the neuropile, such as thinning of or gaps in the connectives (in 1.5% of embryos), or partial lack of the lateral most Fas2 positive tract. DAAMEx68 maternal and zygotic mutant embryos fail to cellularise properly.
DAAMEx68/DAAMEx1 mutant embryos (in which both maternal and zygotic functions are impaired) show severe CNS phenotypes. Thirty-four percent of these embryos exhibit severe morphological aberrations, some with completely disorganized nerve cords. Another 35% display frequent breaks in connectives and commissures, misrouted axons, or failures in commissure separation and, in extreme cases, an almost complete lack of axon bundles. There do not appear to be differences in neuron numbers between DAAMEx68/DAAMEx1 and wild-type embryos, suggesting that the CNS phenotypes are caused by defects in neurite growth rather than aberrant lineage formation. Axonal growth defects are seen before stages 12 and 13, indicating cell death/degeneration is not involved.
Primary neuronal cultures developed from DAAMEx68/DAAMEx1 or DAAMEx68 homozygous mutant embryos are able to develop axons of similar length as their wild-type counterparts. However, filopodia of mutant neurons are reduced in number by 62% and in length by 26%.
DAAMEx68 mutant larvae display severe trachea defects, including the collapse and flattening of the tracheal tubes in both the main airways and the side branches. Tracheal tubes of DAAMEx68 mutant larvae fail to secrete such a highly ordered cuticle as that observed in wild-type larvae. Although some local order is visible, short and curvy apical ridges that rarely run perpendicular to the tube axis can be observed throughout the tracheal system.
DAAMEx68/Df(1)AD11 transheterozygotes show the same strong larval tracheal phenotype as DAAMEx68 homozygotes.
In contrast to the actin organization found in wild-type tracheal cells, in DAAMEx68 mutants this organization is completely abolished. The overall level of apical F-actin is not reduced in the DAAMEx68 mutant tracheal cells but the actin bundles display abnormal morphology and fail to be organized into parallel running actin rings under the apical surface of the cells. Although the global actin organization is severely impaired , local order can often be detected in small patches within a cell. The cuticle pattern of DAAMEx68 mutants displays a similar phenotype.