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#anterior-posterior polarity

2 public questions tagged with this topic.

C-Elegans Development-l

Which protein plays a key role in establishing anterior-posterior polarity in C. elegans?

PAR proteins are partitioning defective regulators of polarity highly conserved from nematodes to mammals. PAR-3 forms anterior cortical complex with PAR-6 and atypical PKC, anchoring CDC-42 and NMY-2 myosin. PAR-1 MARK kinase and PAR-2 occupy posterior cortex after sperm centrosome signal suppresses anterior contractility and enables posterior recruitment. Mutual exclusion maintained via phosphorylation, so PAR-1 excludes PAR-3 posteriorly and aPKC excludes PAR-1 anteriorly. PAR-3 establishes anterior identity, recruiting centrosome rotation cues and influencing segregation of MEX-5, PIE-1, P-granules, ultimately orchestrating asymmetric division, spindle orientation and embryonic axis formation.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 8: PAR proteins establishing anterior-posterior polarity in early embryo.

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Regeneration -l

Which signaling pathway regulates anterior-posterior polarity in regenerating planaria?

Anterior-posterior polarity during planarian regeneration is reset by graded Wnt/beta-catenin signaling along body axis. Posterior wounds upregulate wnt1 transcription within muscle positional control genes, leading to stabilization of beta-catenin that translocates to nucleus activating teashirt and posterior hox genes specifying tail fate. Anterior wounds instead express secreted Wnt inhibitor Notum that deacylates Wnt ligands reducing posterior activity, permitting head organizer genes prep and foxD. Hedgehog regulates wnt1 expression upstream, but core polarity determinant is Wnt/beta-catenin gradient, distinct from JAK-STAT maintaining neoblasts or Notch regulating brain patterning, governing head-tail decision.

Ref: PNAS, Petersen and Reddien 2008: Wnt/β-catenin signaling regulates A-P polarity during planarian regeneration.

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