Mutant flies show rapid paralysis in response to acute heat stress.
sei1 mutant flies are paralysed at elevated temperatures.
Intracellular recordings from mutant dorsal longitudinal muscles show bursts of spontaneous activity at 37[o]C.
sei1/sei2 mutants display abundant small boutons, termed 'satellites', budding from the larger primary boutons along the branch axis. Such aberrant outgrowth is found at both type Ib and Is neuromuscular junctions in different muscles, e.g. 6/7 and 4. Upon closer examination, two distinct types of satellites are observed, one without a clear constriction between satellites and primary boutons, resembling yeast budding (type B satellites) and the other with a short but clear constriction or 'neck' (type M satellites). Type M satellites are more abundant than type B satellites in these mutants. There is also an overall increase in synaptic bouton number and terminal branching in these mutants.
sei1 mutants display significantly enhanced branching patterns along with a robust increase in mature bouton numbers, indicating that sei mutants do not fully prevent type M satellites from entering the successive growth steps.
Exposure to high temperatures (29[o]C) for 2 hours during development fails to induce significant morphological changes in synaptic growth in sei1 mutants. However, numbers of both B- and M-type satellites are drastically reduced after 5 hours of high temperature. Wild-type synapses do not exhibit this behaviour.
Chronic high temperature treated (>5 hours) sei1 mutants exhibit an unusual population of terminal branches consisting of thin strings of type M (and occasionally type B) satellites that are absent in controls. These unusual terminal branches contribute to the increased branching complexity in sei1 mutants. These mutants also exhibit a decrease in primary bouton number.
sei1 mutants display a 60% increase in bouton number at 31[o]C compared with 25[o]C.
sei1 flies do not show a significantly shortened lifespan. At day 37, these flies exhibit sporadic vacuoles throughout the central nervous system. Exposing these mutants to 40oC for 3 minutes results in seizures that last for up to a minute followed by paralysis. The severity of the phenotype progresses with age and daily exposure to the restrictive temperature.
sei1 mutants show behavioral convulsions after brief exposure to elevated temperature.
The courtship song parameters interpulse interval, cycles per pulse, interpulse frequency and amplitude of sound are normal in homozygous males at 25oC.
Substantial enhancement of spontaneous neural activity.
Heat induced expression of seihs.PW in adults is sufficient to restore normal locomotor function.
Homozygous larvae raised at the restrictive temperature (37oC for 6 hours/day from late embryogenesis through to third larval instar) show an increased frequency of ectopic neuromuscular synapses. Embryos raised at 18oC or 34oC show an increased frequency of immature filopodial contacts on muscle fibres 6 and 7 ("collateral sprouts") compared to wild-type embryos raised at the same temperature.
The delivery of an electrical buzz (50-400 msec) to the brain has no significant effect on sei1 mutant flies.
Spontaneous dorsal longitudinal muscle responses increase in frequency as the temperature is increased.
At temperatures >40oC, sei2 causes spontaneous activity in recordings from dorsal longitudinal flight muscles, to appear coincidentally with the heat-induced paralysis.
sei2 is semidominant in this respect and behavior of hyperploid adults exhibits dose dependence: sei2/sei2/+ flies become paralyzed, at 40oC, slightly less rapidly than homozygous mutants; sei2/+/+ paralyzed more slowly than sei2/+ but faster than wild-type.
Recordings of action potentials in the adult giant-fiber pathway reveal no decrement in sei2 at 40oC.