Curated Optogenetic Publication Database

Abstract: Embryonic myeloid (EM) cells are the first immune-cell population to emerge during development and must disperse throughout the embryo to act as the first line of defence against infection. Although EM cells migrate directionally toward wounds, how they navigate through unwounded tissues during early colonization remains unclear. Here we show that EM cell dispersion in Xenopus embryos is driven, at least in part, by cell-on-cell migration, an important yet underappreciated phenomenon, guided by dynamic tissue flows. We have established a new ex vivo EM cell migration system that allows for live imaging, computational analyses and optogenetic manipulation. We find that local ectodermal tissue flows repolarize EM cell protrusions and bias their directional migration. Disrupting these flows, both ex vivo and in vivo, either genetically or mechanically, impairs EM cell dispersion. Our findings reveal that mechanical cues generated by surrounding tissue flows coordinate immune-cell migration during development, highlighting an overlooked mechanism by which collective tissue dynamics guide individual cell behaviour.

Abstract: Regulation of cancer cells by their environment contributes to tumorigenesis and drug response, though the extent to which the oncogenic state can alter a cell's perception of its environment is not clear. Prior studies found that EML4-ALK, a receptor tyrosine kinase (RTK) fusion oncoprotein, suppresses transmembrane receptor signaling through EGFR. Moreover, suppression was reversed with targeted ALK inhibition, thereby promoting survival and drug tolerance. Here we tested whether such modulation of EGFR was common among other RTK fusions, which collectively are found in ∼5% of all cancers. Using live- and fixed-cell microscopy in isogenic and patient-derived cell lines, we found that a wide variety of RTK fusions suppress transmembrane EGFR and sequester essential adaptor proteins in the cytoplasm, as evidenced by the localization of endogenous Grb2. Targeted therapies rapidly released Grb2 from sequestration and potentiated EGFR. Synthetic optogenetic analogs of RTK fusions confirmed that cytoplasmic sequestration of Grb2 was sufficient to suppress perception of extracellular EGF and could do so without driving signaling from the synthetic fusion itself, demonstrating that fusion signaling and suppression of EGFR could be functionally decoupled. Our study uncovers that a large number of RTK fusions simultaneously act as both activators and suppressors of signaling, the mechanisms of which could be exploited for new biomimetic therapies that enhance cell killing and suppress drug tolerance.

Abstract: Drug resistance remains a challenge for targeted therapy of cancers driven by EML4-ALK and related fusion oncogenes. EML4-ALK forms cytoplasmic protein condensates, which result from networks of interactions between oncogene and adapter protein multimers. While these assemblies are associated with oncogenic signaling, their role in drug response is unclear. Here, we use optogenetics and live-cell imaging to find that EML4-ALK assemblies suppress transmembrane receptor tyrosine kinase (RTK) signaling by sequestering RTK adapter proteins including GRB2 and SOS1. Furthermore, ALK inhibition, while suppressing oncogenic signaling, simultaneously releases the sequestered adapters and thereby resensitizes RTK signaling. Resensitized RTKs promote rapid and pulsatile ERK reactivation that originates from paracrine ligands shed by dying cells. Reactivated ERK signaling promotes cell survival, which can be counteracted by combination therapies that block paracrine signaling. Our results identify a regulatory role for RTK fusion assemblies and uncover a mechanism of tolerance to targeted therapies.