PubMed · 13345135
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F LEPAGE, L LEMERRE, A DUPAY. [Amniotic embolism].. https://pubmed.ncbi.nlm.nih.gov/13345135/
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Dorsal closure in the fruit fly Drosophila melanogaster is a complex morphogenetic process, driven by sequential signaling cascades and involving multiple forces, which contribute to cell movements and rearrangements as well as to changes in cell shape. During closure, lateral epidermal cells elongate along the dorsoventral axis and subsequently spread dorsally to cover the embryonic dorsal surface. Amnioserosal cells, which are the original occupants of the most dorsal position in the developing embryo, constrict during closure; thus, the increase in epidermal surface area is accommodated by a reduction in the amnioserosal surface area. Several of the epidermal requirements for closure have been established in functional assays. In contrast, amnioserosal requirements for closure have remained elusive, in part because laser ablation and clonal approaches are limited to only subsets of amnioserosal cells. Here, we report our use of the UAS-GAL4 system to target expression of the cell autonomous toxin Ricin-A to all cells of the amnioserosa. We show that ablation of the amnioserosa leads to clear defects in dorsal closure and, thus, directly demonstrate a role for the amnioserosa in dorsal closure. We also show that DJNK (Drosophila Jun N-terminal kinase) signaling, an epidermal trigger of closure, is unaffected by amnioserosal ablation. These data, together with our demonstration that amnioserosal ablated and Dpp signaling mutant embryos exhibit shared loss-of-function phenotypes, point to a requirement for the amnioserosa in dorsal closure that is downstream of Dpp, perhaps as part of a paracrine response to this signaling cascade.
Chronic ocular surface disorders, which can result in severe functional impairment, have been viewed for decades as untreatable diseases. In 1995, the reintroduction of amniotic membrane transplantation (AMT), either alone or associated with limbal stem cell transplantation, has offered new hope of using tissue and cell therapy strategies to repair ocular surface disorders. Amniotic membrane (AM) has been found to exert its effects by acting as a substrate for the growth of ocular surface epithelia, by suppressing inflammation and scarring and by serving as an anti-microbial barrier. Moreover, AM has recently been used as a substrate for ex vivo expansion of corneal epithelial cells for ocular surface reconstruction. Notwithstanding the substantial agreement among Authors regarding its clinical efficacy, there are still many uncertainties regarding the fate of grafted AM and consequently the mechanisms through which it exerts its long-term effects. Further studies including controlled clinical trials with numerous cases are required to understand which ocular surface conditions are certain to benefit from AM transplantation and how its mechanical properties interact with the mediators produced to favor ocular surface reconstruction.
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