Concomitantly, class II (ddaB) and class III (ddaA/ddaF) neurons are removed via apoptosis ( Williams and Truman, 2005). In the PNS, class I (ddaD/E) and class IV (ddaC) neurons, a subset of dorsal dendrite arborization (da) neurons, prune their larval dendrite arbors without affecting their axonal branches and subsequently regrow the adult-specific dendrites before eclosion ( Kuo et al., 2005 Williams and Truman, 2005). In the CNS, mushroom body γ neurons eliminate their larval axons and dendrites, and later re-extend their neurites to form adult-specific circuits ( Lee et al., 1999). Two stereotyped pruning events occur in the central nervous system (CNS) or the peripheral nervous system (PNS) ( Yu and Schuldiner, 2014). In holometabolous insects, such as Drosophila, the nervous system undergoes dramatic remodeling to establish an adult-specific nervous system during metamorphosis: a transitional stage from larva to adult ( Kanamori et al., 2015a Truman, 1990). A typical example is stereotyped removal of axonal branches in layer 5 cortical neurons at an early postnatal stage in rats ( Stanfield et al., 1982). In vertebrates, neurons first develop exuberant connections with many targets at embryonic stages and eliminate improper ones postnatally to establish functional connectivity ( Schuldiner and Yaron, 2015). Pruning is a highly conserved process during the development of nervous systems in both vertebrates and invertebrates. One of such strategies is pruning that eliminates unnecessary neurites and connections, without causing neuronal death at a later developmental stage ( Luo and O'Leary, 2005 Yaniv and Schuldiner, 2016 Yu and Schuldiner, 2014). Finally, our data reveal that ER-to-Golgi transport promotes endocytosis and downregulation of the cell-adhesion molecule Neuroglian and thereby dendrite pruning.ĭuring animal development, neurons generate excessive cellular processes and connections at an earlier stage, and subsequently achieve accurate wiring via several regressive strategies ( Schuldiner and Yaron, 2015). Moreover, we show that two GTPases, Rab1 and Sar1, which are known to regulate ER-to-Golgi transport, are essential for dendrite pruning of ddaC neurons. Yip1 and Yif1 colocalize on ER/Golgi and are required for the integrity of Golgi apparatus and outposts. Yif1 forms a protein complex with Yip1 in S2 cells and ddaC neurons. We further identify that the Yif1-binding partner Yip1 is also crucial for dendrite pruning. We show that Yif1 is required for dendrite pruning of ddaC neurons but not for apoptosis of ddaF neurons. Here, in a clonal screen, we have identified Yif1, an uncharacterized Drosophila homolog of Yif1p that is known to be a regulator of ER-to-Golgi transport in yeast. However, the important role of endoplasmic reticulum (ER)-to-Golgi transport in dendrite pruning remains unknown. In Drosophila, ddaC sensory neurons specifically prune their larval dendrites with intact axons during metamorphosis. Pruning that selectively removes unnecessary neurites without causing neuronal death is essential for sculpting the mature nervous system during development.
0 kommentar(er)
