The following transheterozygotes show small amounts of adult escapers, depending on culture conditions: spinΔ2b/spinE14.1, spinΔ29/spinΔ2b, spinΔ31/spinΔ2b, spinΔ86/spinΔ2b and spinΔ2b/spinΔ2b. Adult escapers exhibit progressive locomotor defects, such as difficulty in righting after a fall. These defects worsen during the days after emergence and result in death within 5-12 days. The escapers appear morphologically normal except for a subtle, completely penetrant extra wing vein phenotype.
Oocytes produced from spinΔ2b germline clones show dramatically enlarged carbohydrate-containing β spheres in the ooplasm, while protein-containing α spheres are similar in size to wild-type oocytes.
The larval NMJ of both spinE14.1/spinΔ2b and spin11F5/spinΔ2b mutants contain abnormal ultrastructural membrane compartments in the cytoplasm of bnch mutant boutons that are not present in wild-type controls. The excitatory junctional potentials (EJPs) produced by abdominal muscles in 1mM ca2+ from spinE14.1/spinΔ2b and spin11F5/spinΔ2b mutants are not significantly different from those produced by wild-type, indicating that exocytosis is not affected in mutants. When motor neurons from the mutants are repetitively stimulated at 10Hz, the amplitude of the EJP measured from spinE14.1/spinΔ2b and spin11F5/spinΔ2b mutants declines to 55-60% of the original response after 10 minutes, while no such decline is observed for wild-type animals. Additionally, spinE14.1/spinΔ2b mutant boutons show a significant decrease in the uptake of FM1-43 dye compared with controls. These results indicate that the mutants have a defect in synaptic vesicle endocytosis.
Mosaic spinΔ2b eyes show no obvious rough eye phenotypes.
Mutation is lethal at the pharate pupal stage. Heterozygotes and spinΔ2b/Df(2R)Jp4 hemizygotes show a significant increase in bouton number at the larval neuromuscular junction (assayed at muscles 6/7 in hemisegment A3) compared to wild type. Average bouton size spinΔ2b/Df(2R)Jp4 animals is not significantly different from wild type. Quantal content at the neuromuscular junction is decreased by approximately 50% compared to wild type in spinΔ2b/Df(2R)Jp4 animals. Quantal size is unaffected.