Figure 6. Dscam[TM1] and [TM2] Exhibit Similar Biochemical Properties and Cellular Functions When They Are Localized in the Same Subcellular Compartment.

(A and B) Dock preferentially interacts with endogenous Dscam[TM2] in vivo. (A) Brain lysates of larvae with global iso-tagging of [TM1]::HA or [TM2]::V5 were immunoprecipitated by anti-HA or V5 beads, respectively, and immunoblotted with an anti-Dscam antibody that recognizes both [TM1] and [TM2] and an anti-Dock antibody. This experiment was repeated twice. (B) Brain lysates of larvae that expressed [TM1]::GFP or [TM2]::GFP through the endogenous Dscam promoter were immunoprecipitated by an anti-GFP antibody. The immunoprecipitates were immunoblotted with anti-GFP and anti-Dock antibodies. This experiment was repeated three times.

(C–F) Dscam[TM2] requires Dock to promote presynaptic terminal growth. Shown are representative images of A4–A6. Overexpressing a Dscam[TM2]::GFP transgene significantly promotes axonal growth in C4 da neurons (C) & (D). Although the loss of dock does not affect C4 da axon terminals (E), it completely abolishes the overgrowth caused by Dscam[TM2]::GFP overexpression (F).

(G) Quantification of the number of C4 da axon connectives.

(H) Dock binds to [TM1] and [TM2] in similar affinity in cultured S2 cells. Lysates of S2 cells expressing mCD8::GFP, Dscam[TM1]::GFP or [TM2]::GFP were immunoprecipitated with an anti-GFP antibody. Inputs and immunoprecipitates were blotted by anti-GFP and anti-Dock antibodies. This experiment was repeated three times.

(I–K) Transgenic Dscam[TM1] requires Dock to promote presynaptic terminal growth. Compared with WT (I), overexpressing [TM1]::GFP transgene significantly promotes axonal growth in C4 da neurons (J), which is completely abolished by loss of dock (K).

(L) Quantification of the number of C4 da axon connectives from A4–A6.

See also Figure S6.