TY - JOUR TI - R7 photoreceptor axon targeting depends on the relative levels of lost and found expression in R7 and its synaptic partners AU - Douthit, Jessica AU - Hairston, Ariel AU - Lee, Gina AU - Morrison, Carolyn A AU - Holguera, Isabel AU - Treisman, Jessica E A2 - Mason, Carol A A2 - Banerjee, Utpal A2 - Suzuki, Takashi VL - 10 PY - 2021 DA - 2021/05/18 SP - e65895 C1 - eLife 2021;10:e65895 DO - 10.7554/eLife.65895 UR - https://doi.org/10.7554/eLife.65895 AB - As neural circuits form, growing processes select the correct synaptic partners through interactions between cell surface proteins. The presence of such proteins on two neuronal processes may lead to either adhesion or repulsion; however, the consequences of mismatched expression have rarely been explored. Here, we show that the Drosophila CUB-LDL protein Lost and found (Loaf) is required in the UV-sensitive R7 photoreceptor for normal axon targeting only when Loaf is also present in its synaptic partners. Although targeting occurs normally in loaf mutant animals, removing loaf from photoreceptors or expressing it in their postsynaptic neurons Tm5a/b or Dm9 in a loaf mutant causes mistargeting of R7 axons. Loaf localizes primarily to intracellular vesicles including endosomes. We propose that Loaf regulates the trafficking or function of one or more cell surface proteins, and an excess of these proteins on the synaptic partners of R7 prevents the formation of stable connections. KW - photoreceptor KW - synapse KW - endosome KW - axon targeting KW - matching JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -