Insertion line P{GD2208}v6661 of Letm1^GD2208 is lethal between pupal stage and fly eclosion in crosses with Scer\GAL4^ey.PH. Other insertions of Letm1^GD2208 are viable.

Expression of Letm1^GD2208 in muscle cells at all stages of development under the control of Scer\GAL4^Mef2.PU results in larvae showing reduced body size and sluggish behaviour with no climbing from the food onto the vial-walls. In addition, growth is arrested at the pupal stage. However, rare escapers (approximately 10% of all pupae) develop into adult flies. These flies are unable to fly and appear very weak and smaller than wild-type.

Expression of Letm1^GD2208 in the developing eye under the control of Scer\GAL4^ey.PH results in rough and small eyes. The ommatidial cells display structurally intact mitochondria. However, a significant number of individual ommatidia of Scer\GAL4^ey.PH>Letm1^GD2208-expressing eye discs show dramatically swollen mitochondria with an electron transparent matrix and remnant cristae, a phenotype that is never seen in wild-type eyes. The mitochondria of such individual mutant ommatidia are affected collectively, as revealed by disorganised structures of the photoreceptors within the ommatidia. This mitochondrial phenotype is not accompanied by a massive increase in the classical hallmarks of cell death, such as condensed osmophilic nuclei.

Expression of Letm1^GD2208 in the central nervous system under the control of Scer\GAL4^ey.PH results in decreased locomotion of the flies compared with controls. When the locomotor activity of adult flies expressing Scer\GAL4^elav.PU>Letm1^GD2208 is monitored, it is found that the average speed during movement is significantly reduced in the mutants compared with wild-type. The number of immobile episodes (pauses in locomotion of more than 2s) is significantly increased in the mutants compared with controls. As a consequence, the average total time spent being immobile by the mutants is notably increased in comparison with controls.

Expression of Letm1^GD2208 in neurons and synapses under the control of Scer\GAL4^n-syb.PS results in decreased locomotion of the flies compared with controls. When the locomotor activity of adult flies expressing Scer\GAL4^n-syb.PS>Letm1^GD2208 is monitored, it is found that the average speed during movement is slightly reduced in the mutants compared with wild-type. The number of immobile episodes (pauses in locomotion of more than 2s) is significantly increased in the mutants compared with controls. As a consequence, the average total time spent being immobile by the mutants is notably increased in comparison with controls.

Expression of Letm1^GD2208 in neurons and synapses under the control of Scer\GAL4^n-syb.PS results in decreased neurotransmitter release in synapses. Recordings of spontaneous and evoked synaptic activity at third instar larval neuromuscular junctions reveal that the spontaneous neurotransmitter release (i.e. the spontaneous fusion of a neurotransmitter vesicle with the presynaptic membrane) is unaffected in Scer\GAL4^n-syb.PS>Letm1^GD2208-expressing animals compared with controls. However, nerve-evoked neurotransmitter release is significantly reduced in the mutant larvae compared with wild-type, as shown by stimulating the nerve with both single pulses and with hight frequency 10 Hz stimuli. The number of neurotransmitter molecules filling each vesicle appears to be the same in control and Scer\GAL4^n-syb.PS>Letm1^GD2208-expressing animals, as indicated by the overlapping amplitude distributions of spontaneous neurotransmitter release events (or minis) in both control and mutant strains. These data indicate that expression of Letm1^GD2208 does not interfere with the number of neurotransmitter molecules per vesicle but with the number of vesicles undergoing exocytosis upon arrival of nerve action potential.

Adults expressing Letm1^GD2208 under the control of Scer\GAL4^elav.PLu (in the presence of Dcr-2^Scer\UAS.cDa to increase the efficiency of RNAi) do not show a significant defect in avoidance of noxious temperature (46[o]C) compared to control flies.

Depending on the insertion line used, expression under the control of Scer\GAL4^Mef2.PR can result in viable flies or early larval lethality.

Expression under the control of Scer\GAL4^pnr-MD237 may result in semi-lethality, depending on the insertion line used.

Expression under the control of Scer\GAL4^pnr-MD237 results in loss of bristles on the notum in 0% or 50-60% of the Scer\GAL4^pnr-MD237 expression domain, depending on the insertion line used.

Expression under the control of Scer\GAL4^pnr-MD237 results in the absence of 0% or 40-50% of the Scer\GAL4^pnr-MD237-expressing area of the notum, depending on the insertion line used.