shrb4 homozygosity is cell lethal in the wing disc, as no clones are observed.
shrb4/shrb4 MARCM ddaC mutant clones show dendrite pruning defects at 18hr APF, compared to controls.
shrb4 mutants do not exhibit an eye phenotype.
shrb4 mutants exhibit increased dendritic branching. Mutant ddaA neurons exhibit spine-like protrusions that are much longer than on wild-type ddaA neurons.
shrb4 zygotic mutant embryos do not exhibit detectable axon guidance or fasciculation defects in central nervous system and sensory neurons. However, some DA (dendritic arborisation) neurons exhibit abnormal axonal branching.
shrb4 mutant embryos die before reaching the larval stage. At 15-16 hours after egg-laying, dorsal dendrites in shrb4 mutants exhibit multiple dorsally oriented branches, compared to wild-type dorsal dendrites, which exhibit two dorsally oriented dendrites. At 17-18 and 19-20 hours after egg-laying, dendritic arborization (DA) neurons exhibit greatly reduced dendritic fields, with lateral branches often failing to reach the adjacent segment boundaries. The average dendritic field of dorsal clusters is reduced in shrb4 mutant embryos. Dendritic growth is similarly affected in embryos with the shrb4 mutation in trans with Df(2R)Np5 or In(2LR)w45-32n.
The shape of the dendritic trees of shrb4 mutant somatic clone ddaE neurons is similar to that in wild-type, but the number of dendritic termini is increased significantly because of an increase in fine, higher-order branches. shrb4 mutant clones of ddaF and ddaB neurons exhibit similar results. shrb4 ddaC somatic clone neurons exhibit a nearly 100% increase in dendritic termini. They also exhibit a high degree of branching complexity near the cell body. Dendritic fields of shrb4 ddaC somatic clones are also reduced in size. shrb4 mutant ddaA or ddaD neurons extend longer spine-like protrusions, in comparison to wild-type.
shrb4 mutant PNS neuron clones exhibit ectopic axonal branches in 21% in cases.
Exhibits reduced lateral branches in the dorsal cluster of embryonic dendrites. The dorsal dendrites extend only a fraction of the normal length and produce a few weakly elaborating lateral branches. The dendritic field in stage 17 embryos is drastically reduced. This is seen in over 95% of embryos. Mutants show no gross defects in muscle, anterior-posterior or dorsal-ventral patterning. The number of peripheral nervous system (PNS) neurons is the same as in wild-type. es and ch neurons retain their single dendrite morphology. There is no detectable abnormality in PNS and central nervous system axons.