neuroblast & embryonic optic lobe primordium
Loss of so function results in the absence of eye field derived neuroblast lineages including P5m.
Axonal projections of the ato-expressing dorsal cluster lobular pattern appears essentially wild type in mutant brains.
In mutant larvae the R7/R8 axons project to positions in the optic anlage consistent with their dorsoventral positions in the eye disc and independent of Bolwig's nerve.
sounspecified has no effect on the period of CkIIβAnd flies.
The number of photoreceptor cells is variably reduced in the nervous system of third instar larvae. In third instar larvae completely lacking photoreceptors, mitotically active lamina precursor cells are absent.
Eyes are reduced to small groups of facets. Diacylglycerol kinase activity is very low compared to wild-type.
Cell degeneration is seen in the optic lobes, the medulla cortex and the cortex of the lobula complex in the pupa.
The number of axons in the anterior optic tract (AOT) is reduced by 35% compared to wild-type. sol1 sounspecified double mutants have a loss of up to 83% of axons in the AOT compared to wild-type.
Most flies are completely eyeless, but some individuals have a variable number of facets on one or both sides. There is extensive cell degeneration in the medulla cortex and the cortex of the lobular complex in the pupa, and axon degeneration in the inner optic chiasma. The reduction in the medulla of the optic lobe in the adult is most severe in the distal region. There is no lamina. Many neuronal cell types found in the wild-type medulla and lobular complex are also found in so mutant flies.
Transheterozygotes with eya4 are normal.
Ultrastructural analysis indicates that the sol1 and sounspecified mutations act independently on nearly exclusive subsets of axons in the AOT.
The types of neural cell present in so mutant optic lobe rudiments has been investigated.
Studies of gynandromorph flies show that the so mutation acts primarily on the eye anlagen. Cell degeneration occurs in the medulla after the axons have participated in the formation of the second optic chiasma.