Drosophila Neurotrophins Reveal a Common Mechanism for Nervous System Formation
Figure 7
DNT1 Enables Motor-Axon Targeting
(A) Projections of motor neurons to the embryonic muscles.
(B) Altered DNT1 function results in an increase in ISNb/d misrouting phenotypes. In wild type, there are three stereotypic projections (I, II, and III). Two phenotypes were observed in all genotypes with comparable frequency: “fan” of multiple thin projections originating from II, and “loss” of one or more projections. Misrouting phenotypes, including concomitant effects in two or more projections (e.g., misrouting in two projections, or misrouting in one plus loss of another), are found with higher frequency in experimental genotypes (some examples drawn).
(C–H) ISNb/d motor neuron targeting at muscles 7, 6, 13, and 12 visualised with FasII antibodies (brown) in stage 17: (C) wild-type embryos; (D) DNT141/Df(3L)ED4342 transheterozygote mutants; (E) DNT141 mutants; (F and G) upon targeted RNAi to the muscle: (F) 24BGAL4 > pWCysknotRNAi;DfED4342 and (G) 24BGAL4 > pro-RNAi;DfED4342; (H) upon expression of Cysknot3′tail at the muscle (24BGAL4 > UASCysknot3′tail). GOF, gain of function; LOF, loss of function; mr, misrouting; wt, wild type.
(I–L) SN projections: (I) wild type; (J) DNT141/Df(3L)ED4342; (K) 24BGAL4 > pro-RNAi;DfED4342; (L) 24BGAL4 > UASCysknot3-tail. Arrowheads point to projections or misroutings, asterisks to missing projections. Dorsal is up, anterior to the left.
(M and N) Quantification of ISNb/d and SN phenotypes: misrouting and effects in two or more projections are shown in brown and for controls in blue. Triple asterisks (***) indicate p < 0.001, double asterisks (**) indicate p < 0.01, and a single asterisk (*) indicates p < 0.05. Black asterisks are comparisons to wild type, red asterisks to controls. Numbers over graphs indicate number of hemisegments. For statistics tests and p-values, see Text S1.