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Fig. 5 | BMC Developmental Biology

Fig. 5

From: The asymmetric cell division machinery in the spiral-cleaving egg and embryo of the marine annelid Platynereis dumerilii

Fig. 5

ACD components that convey apical associated polarity cues. Schematic drawings illustrating proposed mechanisms establishing apical/basal cell polarity derived from previous studies in C. elegans and Drosophila. a-d Dynamic interactions establishing apical Crumbs complex. a aPKC phosphorylates Par3 weakening Par3 bond with aPar complex. Crumbs outcompetes phosphorylated Par3. Unphosphorylated Par3 binds PTEN increasing PIP2 in apical domain. b Par3 recruits Pals1 to apical membrane where aPKC phosphorylates Par3, weakening association of Par3 to Pals1. Pals1 outcompetes aPKC-Par6-Cdc42 complex with Crumbs. c PatJ and Lin7 are recruited to Pals1 to stabilize Crumbs complex. Par3 reestablishes itself with aPKC-Par6-Cdc42 complex. d aPar complex interacts with Afadin to recruit Echinoid to lateral domain. Likewise, aPAR complex also interacts with p120/α/β-catenin complex to establish immature AJs with N-Cadherin. Afadin and p120/α/β-catenin adaptors link extracellular domain proteins Echinoid and N-Cadherin to actin cytoskeleton. Establishment of Crumbs complex stabilizes apical domain and defines lateral domain. e Transcriptional profiles of Crumbs complex components, early stages of P. dumerilii based on RNA-seq: x-axis—time in hours post fertilization (hpf), y-axis— median level of transcripts in fragments per kilobase per million reads (FPKM) (Additional file 5). Transcript levels for crumbs, patj, and pals1 show high expression at 2 hpf. lin7 exhibits elevated zygotic transcription in early cleavage stages. For error bars see Additional file 11

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