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. 2014 Jan 15;28(2):121–126. doi: 10.1101/gad.230599.113

Figure 4.

Figure 4.

CNEP-1 suppresses ER sheet formation in the vicinity of the nuclear envelope. (A) Inverted contrast fluorescence confocal images of interphase embryos expressing the ER lumen marker GFP∷SP12. Bar, 10 μm. (B) Transmission electron micrographs of ultrathin cross-sections of high-pressure-frozen control and cnep-1Δ embryos. Magnified images of the boxed regions are paired with micrographs pseudocolored to highlight the location of the nuclear envelope (dark red) and ER sheets (red). Bars, 900 nm. (C) Model for spatial regulation of phospholipid synthesis by CNEP-1. In control embryos, the CNEP-1 complex activates lipin to limit the amount of PI on nuclear membranes and ER membranes in the vicinity of the nucleus (green nuclear envelope/ER membranes contain PC and PE with limited PI). In cnep-1Δ embryos, lipin is less active at the nuclear envelope, and PI levels are higher (orange nuclear envelope/ER membranes contain PC, PE, and PI). Increased PI levels lead to ectopic ER sheets in the vicinity of the nucleus that encase the nuclear envelope following mitotic permeabilization and inhibit its subsequent disassembly.