gilgamesh, Drosophila casein kinase 1g, is required for myosin-dependent junction strengthening and epithelial folding

Adherens junctions, which serve as the primary physical link between cells, undergo remodeling in response to tension forces to maintain tissue integrity and promote tissue shape changes. However, the in vivo mechanisms driving this process remain poorly understood. Here, we identified Gilgamesh (Gish), the conserved fly homolog of casein kinase 1g as essential for myosin-dependent junction strengthening and tissue folding during apical constriction of Drosophila mesoderm. We show that Gish is recruited to spot adherens junctions in a contractile myosin-dependent manner. During apical constriction, Gish is required for junction strengthening by promoting growth and merging of small junction puncta, as well as stabilizing junction puncta at cell edges. The junction defects in Gish-depleted mesoderm result in breakage of the tissue-scale apical actomyosin network during apical constriction, and ultimately failure in mesoderm infolding. Our data show that Gish is a mechanosensitive kinase required for the integrity of adherens junctions during apical constriction.