Staccato/Unc-13-4 Controls Secretory Lysosome-mediated Lumen Fusion During Epithelial Tube anastomosis
Overview
Affiliations
A crucial yet ill-defined step during the development of tubular networks, such as the vasculature, is the formation of connections (anastomoses) between pre-existing lumenized tubes. By studying tracheal tube anastomosis in Drosophila melanogaster, we uncovered a key role of secretory lysosome-related organelle (LRO) trafficking in lumen fusion. We identified the conserved calcium-binding protein Unc-13-4/Staccato (Stac) and the GTPase Rab39 as critical regulators of this process. Stac and Rab39 accumulate on dynamic vesicles, which form exclusively in fusion tip cells, move in a dynein-dependent manner, and contain late-endosomal, lysosomal, and SNARE components characteristic of LROs. The GTPase Arl3 is necessary and sufficient for Stac LRO formation and promotes Stac-dependent intracellular fusion of juxtaposed apical plasma membranes, thereby forming a transcellular lumen. Concomitantly, calcium is released locally from ER exit sites and apical membrane-associated calcium increases. We propose that calcium-dependent focused activation of LRO exocytosis restricts lumen fusion to appropriate domains within tip cells.
The dynamics of tubulogenesis in development and disease.
Romero A, Walker B, Krneta-Stankic V, Gerner-Mauro K, Youmans L, Miller R Development. 2025; 152(3).
PMID: 39959988 PMC: 11883272. DOI: 10.1242/dev.202820.
Cell-Mediated Branch Fusion in the Drosophila Trachea.
Jiang L Results Probl Cell Differ. 2023; 71:91-100.
PMID: 37996674 DOI: 10.1007/978-3-031-37936-9_5.
Miao H, Millage M, Rollins K, Blankenship J Development. 2023; 150(16).
PMID: 37590130 PMC: 10445802. DOI: 10.1242/dev.201547.
Scholl A, Ndoja I, Dhakal N, Morante D, Ivan A, Newman D PLoS Genet. 2023; 19(1):e1010571.
PMID: 36689473 PMC: 9870157. DOI: 10.1371/journal.pgen.1010571.
Bae E, Huang P, Muller-Greven G, Hambardzumyan D, Sloan A, Nowacki A Nat Commun. 2022; 13(1):4268.
PMID: 35879332 PMC: 9314429. DOI: 10.1038/s41467-022-31981-2.