Misexpression of fra::roboScer\UAS.FR.T:Hsap\MYC in the contralateral eagle (eg) neurons under the control of Scer\GAL4eg-Mz360 prevents the posterior subset of eg axons, but not the anterior, from crossing the midline.
Expression of fra::roboScer\UAS.FR.T:Hsap\MYC with Scer\GAL4Cha.7.4 leads to a severe depletion or absence of cholinergic axons in the commissures, efficiently displacing cholinergic axon terminals out of the dorsal motor neuropile. Under these conditions contact of motorneuron dendrites with cholinergic interneuron terminals is severely reduced and potentially absent at 18.5 hours after egg laying, unlike in the wild-type; yet the overall organisation of the neuropile, including the distribution of Fas2-positive tracts, is not affected. Dendritic intermediate (MN-LL1) and lateral (MN-DA3) territories also remain distinct, though they appear more variable compared to controls.
Expression of fra::roboScer\UAS.FR.T:Hsap\MYC driven by Scer\GAL4elav.PLu does not lead to a significant reduction in commissural axon thickness.
Expression of fra::roboScer\UAS.FR.T:Hsap\MYC when driven by Scer\GAL4unspecified, causes a loss of commissure phenotype.
Scer\GAL4elav.PLu driven expression in the nervous system generates animals with commissures that are significantly thinner than wild-type. These flies are viable and fertile and can be used to cross with each other generating embryos expressing higher levels of fra::roboScer\UAS.FR.T:Hsap\MYC. The progeny of these crosses show phenotypes ranging from wild-type to completely commissureless, the strength of which correlates strongly with the level of expression. In higher expressing lines, defects in motor neuron innervation are also seen. There is a dramatic reduction in innervation (78%, n=155) of muscles 7 and 6 by motorneuron RP3 (which is part of the intersegmental nerve b - ISNb). ISNb also displays other defects, predominantly bypass and stalls. In contrast to fra and Netrin mutants the ISN never crosses the segment border nor fasciculates with the ISN in the adjacent segment. The transverse nerve (TN) fails to form over muscles 7 and 6; both branches (the LBD and the TMN axons) stall and do not enter the region of the ventral muscles (75%, n=148).
fra::robo1UAS.FR.Tag:MYC/Scer\GAL4elav.PLu is a suppressor of abnormal neuroanatomy | embryonic stage 16 phenotype of robo1unspecified
Scer\GAL4ap-md544/fra::robo1UAS.FR.Tag:MYC is a suppressor of abnormal neuroanatomy | embryonic stage 16 phenotype of robo1unspecified
Scer\GAL4unspecified, fra::robo1UAS.FR.Tag:MYC has symmetrical commissure phenotype, suppressible by enaGC1
Scer\GAL4elav.PLu, fra::robo1UAS.FR.Tag:MYC has symmetrical commissure phenotype, suppressible by Df(1)NP5
Scer\GAL4elav.PLu, fra::robo1UAS.FR.Tag:MYC has symmetrical commissure phenotype, suppressible by commUAS.cKa/Scer\GAL4elav.PLu
Scer\GAL4elav.PLu, fra::robo1UAS.FR.Tag:MYC has symmetrical commissure phenotype, non-suppressible by fraGA957
fra::robo1UAS.FR.Tag:MYC/Scer\GAL4elav.PLu is a suppressor of larval longitudinal connective | embryonic stage 16 phenotype of robo1unspecified
fra::robo1UAS.FR.Tag:MYC/Scer\GAL4elav.PLu is a suppressor of commissure | embryonic stage 16 phenotype of robo1unspecified
Scer\GAL4ap-md544/fra::robo1UAS.FR.Tag:MYC is a suppressor of larval longitudinal connective | embryonic stage 16 phenotype of robo1unspecified
Scer\GAL4ap-md544/fra::robo1UAS.FR.Tag:MYC is a suppressor of commissure | embryonic stage 16 phenotype of robo1unspecified
Pan-neuronal expression of fra::roboScer\UAS.FR.T:Hsap\MYC under the control of Scer\GAL4elav.PLu partially suppresses the midline crossing phenotype seen in robounspecified mutants. Many of the most medial ipsilateral axons still cross the midline.
Expression of fra::roboScer\UAS.FR.T:Hsap\MYC in the ap neurons under the control of Scer\GAL4ap-md544 partially rescues the midline crossing phenotype seen in robounspecified mutants. Some segments have ap axon tracts on both sides of the midline.
Co-expression of PakScer\UAS.T:Myr1 and fra::roboScer\UAS.FR.T:Hsap\MYC under the control of Scer\GAL4elav.PLu leads to a striking reduction in commissural axon thickness.
When two copies of P{UAS-fra-robo-Myc} expressed under the control of Scer\GAL4elav.PLu are combined with Df(1)NP5 (which removes both NetA and NetB), a suppression of the P{UAS-fra-robo-Myc} phenotype is seen. In combination with fraGA957 however, no suppression is seen. When both commScer\UAS.cKa and fra::roboScer\UAS.FR.T:Hsap\MYC are both expressed in all neurons by Scer\GAL4elav.PLu, suppression of the fra::roboScer\UAS.FR.T:Hsap\MYC phenotype is seen with some significant commissure formation in greater than 60% of segments (n+29 animals).
