|Feature type||allele||Associated gene||Dmel\sei|
|Also Known As||seits1|
|Map ( GBrowse )|
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|Nature of the Allele|
|Mutations Mapped to the Genome|
|Associated Sequence Data|
|Nature of the lesion|
Amino acid replacement: K282. K282 lies before the first membrane-spanning segment.
Amino acid replacement: K282@. Resulting protein completely lacks the hydrophobic core that forms the transmembrane channel.
|Phenotype Manifest In|
neuromuscular junction & synapse
Intracellular recordings from mutant dorsal longitudinal muscles show bursts of spontaneous activity at 37[o]C.
sei/sei 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. sei 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 sei 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) sei 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 sei mutants. These mutants also exhibit a decrease in primary bouton number.
sei 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.
|NOT Enhancer of|
|Phenotype Manifest In|
dao[b4] sei/dao[g1] sei double mutants show the same time to paralysis on shifting to the restrictive temperature as either single mutant.
When compared with single mutants, the combined mutational effects of sei/slo are not simply additive, with a further enhancement of some slo, but not sei phenotypes. Satellite abundance is less extreme in sei/slo double mutants compared to sei mutants. There is a slight, but not significant, reduction in the numbers of both types B and M satellites. In contrast, the numbers of type M (but not type B) satellites and mature boutons are significantly greater in double mutants compared to slo single mutants.
sei ; Syt4[BA1] double mutants exhibit no significant change in bouton number between 25[o]c and 31[o]C.
|Complementation & Rescue Data|
|Stocks ( 0 )|
|Notes on Origin|
Reduced level of saxitoxin binding in head membrane extracts and a decreased sodium current density in cultured embryonic neurons.
|External Crossreferences & Linkouts|
|Synonyms & Secondary IDs ( 4 )|
|Secondary FlyBase IDs|
|References ( 19 )|