Innexin 3, a New Gene Required for Dorsal Closure in Drosophila Embryo

Abstract

BackgroundDorsal closure is a morphogenetic event that occurs during mid-embryogenesis in many insects including Drosophila, during which the ectoderm migrates on the extraembryonic amnioserosa to seal the embryo dorsally. The contribution of the ectoderm in this event has been known for a long time. However, amnioserosa tension and contractibility have recently been shown also to be instrumental to the closure. A critical pre-requisite for dorsal closure is integrity of these tissues that in part is mediated by cell-cell junctions and cell adhesion. In this regard, mutations impairing junction formation and/or adhesion lead to dorsal closure. However, no role for the gap junction proteins Innexins has so far been described.Results and DiscussionHere, we show that Innexin 1, 2 and 3, are present in the ectoderm but also in the amnioserosa in plaques consistent with gap junctions. However, only the loss of Inx3 leads to dorsal closure defects that are completely rescued by overexpression of inx3::GFP in the whole embryo. Loss of Inx3 leads to the destabilisation of Inx1, Inx2 and DE-cadherin at the plasma membrane, suggesting that these four proteins form a complex. Accordingly, in addition to the known interaction of Inx2 with DE-cadherin, we show that Inx3 can bind to DE-cadherin. Furthermore, Inx3-GFP overexpression recruits DE-cadherin from its wildtype plasma membrane domain to typical Innexin plaques, strengthening the notion that they form a complex. Finally, we show that Inx3 stability is directly dependent on tissue tension. Taken together, we propose that Inx3 is a critical factor for dorsal closure and that it mediates the stability of Inx1, 2 and DE-cadherin by forming a complex.

The molecular and immunochemical expression of innexins in the yellow fever mosquito, Aedes aegypti: Insights into putative life stage- and tissue-specific functions of gap junctions

“…In arthropods, the physiological roles of GJ have not yet been fully elucidated, but they appear to play important roles in development, reproduction, and epithelial physiology. In Drosophila melanogaster, innexin 1 ( ogre ) is critical to the development of retinal neurons (Curtin et al 2002), and innexin 3 is necessary for dorsal closure in embryogenesis (Giuliani et al, 2013). Moreover, innexin 4 ( zero population growth or zpg ) is involved with functional gonad formation in males of both D. melanogaster flies and Anopheles gambiae mosquitoes (Magnusson et al, 2011; Tazuke et al, 2002), and is necessary for early germ cell differentiation in female D. melanogaster (Gilboa et al, 2003).…”

Autocrine insulin pathway signaling regulates actin dynamics in cell wound repair

“…3D-F', 3L-N; Video 2). Gp150 encodes a transmembrane glycoprotein that regulates Notch signaling during normal eye development in Drosophila [57], whereas Inx3 encodes a gap junction protein involved in morphogenesis and nervous system development [58,59]. Thor encodes a translation inhibitor functioning downstream of insulin signaling that is sensitive to reactive oxygen species [60].…”

Innexin7a forms junctions that stabilize the basal membrane during cellularization of the blastoderm in Tribolium castaneum

“…It is also possible that Inx7a primes and stabilizes the formation of heteromeric gap junctions with other Innexins. This has been proposed for Drosophila Inx3 in an Inx1-Inx2-Inx3 complex in the amnioserosa, as the sole loss of Inx3 leads to a strong dorsal closure phenotype, in contrast to the individual loss of Inx1 or Inx2 (Giuliani et al, 2013).…”