Unlike wild-type and lace heterozygous controls, lacek05305/lace2 and lacek05305/laceU2 transheterozygous adults show a mushroom body "lost-lobe" phenotype in about half of cases; the overall dendrite organization in lacek05305/lace2 seems unaffected, as indicated by microtubule polarity (nod) and compartment identity (Apc2, DenMark, etc). Single cell analysis reveals a failure of lacek05305/lace2 mushroom body neurons to extend their axon branches dorsally, instead developing parallel horizontal branches. In lacek05305/lace2 larvae and pupae the vertical α/α' Kenyon cell lobe is already missing. Despite the missing lobe in larvae, the α/β axons and α'/β' axons still segregate into distinct horizontal lobes; there is non-segregation of the α' and β' growth cones, despite of unperturbed peduncle development; γ Kenyon cells do not seem to be affected.
lace2/lacek05305 and lacek05305/Df(3L)BSC671 larvae have significantly reduced bouton number and significantly increased bouton size at the neuromuscular junction of muscle 4, compared to controls, with no effect on the number of satellite boutons.
lacek05305/lace2 transheterozygous mutant adults present significantly decreased survival to starvation, decreased body weight, decreased adiposity in abdominal sections and decreased sizes of fat body cells and lipid droplets, but similar feeding behavior, as assessed by starvation-induced appetite, postprandial meal volume, average meal frequency and volume, and caloric intake, as compared to controls.
When raised on a standard diet, lacek05305 mutants survive to adulthood, although in reduced numbers. However, when these mutants are raised on lipid-depleted medium+cholesterol, 90% arrest as third instar larvae. This arrest is likely to be caused by the lack of dietary sphingolipid in lipid-depleted media. More than 80% of arrested lacek05305 mutant larvae remain viable for at least 10 days by which time their heterozygote siblings have pupariated. When raised on lipid-depleted medium with cholesterol, homozygous lacek05305 mutant larvae die 3 days earlier than their heterozygous siblings.
Heterozygotes have normal photoreceptor organisation.
lacek05305/lace2 adults have an average flight score of 1.41 +/- 0.063 compared to 1.62 +/- 0.14 in wild-type flies in a standard flight performance assay. The average number of dorsal longitudinal flight muscles per hemithorax is 5.94 +/- 0.030 in the mutant flies, compared to 6.00 +/- 0.00 in wild-type flies. Homozygotes show 91% lethality. Those adults that do survive have a lifespan of less than one week and have pronounced morphological defects; wings are notched and often fail to inflate, bristles are missing and the eyes are often rough with irregular ommatidia. Surviving adults have an average of 4.82 +/- 0.53 dorsal longitudinal flight muscles per hemithorax, compared to 6.00 +/- 0.00 in wild-type flies.
lacek05305/lace2 shows reduced viability. lacek05305/lace2 flies often show incision of the wing margin, and there is an ectopic crossvein. The hexagonal array of the ommatidia is disrupted, especially along the equatorial plane. The deep pseudopupil pattern is normal. In the notum, the microchaetae lack pigment and are occasionally missing, while the number of macrochaetae is variable. In the leg and antenna, bifurcation of the distal portion is rarely seen. The lethality and various adult mutant phenotypes of lacek05305/lace2 flies can be rescued by feeding with sphingosine. The adult mutant phenotypes cannot be rescued by exogenous sphingomyelin or ceramide. The wing, leg and eye-antennal discs of lacek05305/lace2 animals contain a considerably high number of dead cells. Severe malformation of the primordial wing blade is seen in the wing disc. The developing pupal eye shows loss of cells among cone cells, primary pigment cells, secondary pigment cells, tertiary pigment cells and interommatidial bristles.