| Component | Localization | Relationship to MEX-5/6 | Function in pathway |
|---|---|---|---|
| PAR-1 kinase | Posterior cortex/cytoplasm of the zygote and posterior blastomeres | Upstream regulator; phosphorylates MEX-5/6, shifting them into faster-diffusing states in the posterior and thereby helping generate the anterior-high MEX-5/6 gradient (pqac-00000002, pqac-00000005, pqac-00000006, pqac-00000007) | Couples PAR polarity to cytoplasmic fate determinant segregation through a kinase/phosphatase diffusion-retention mechanism (pqac-00000005, pqac-00000007) |
| PP2A phosphatase | Broadly/uniformly distributed in the zygote cytoplasm | Antagonizes PAR-1 by dephosphorylating MEX-5/6, promoting slow-diffusing RNA-bound states and anterior retention (pqac-00000005, pqac-00000006, pqac-00000010) | Maintains the phosphorylation cycle that stabilizes the MEX-5/6 concentration gradient without requiring localized synthesis or degradation (pqac-00000005, pqac-00000007) |
| MEX-5/MEX-6 | Initially uniform; then enriched in anterior cytoplasm of the 1-cell embryo and inherited mainly by anterior blastomeres; later associated with posterior germline/P-granule-related compartments (pqac-00000003, pqac-00000022, pqac-00000023) | Core polarity mediators; partially redundant CCCH zinc-finger RNA-binding proteins that bind U-rich 3'UTR sequences and regulate mRNA translation, RNA turnover, protein mobility gradients, and germ plasm asymmetry (pqac-00000000, pqac-00000004, pqac-00000030, pqac-00000033) | Convert cortical polarity into asymmetric cell fate specification by promoting somatic anti-germ-plasm activity, translational activation of zif-1, recruitment of decay factors, and anterior dissolution/exclusion of germline determinants (pqac-00000000, pqac-00000004, pqac-00000013) |
| PIE-1 | Posterior-enriched cytoplasm and germline blastomeres | Downstream target opposed by MEX-5/6; MEX-5/6 increase PIE-1 mobility in the anterior and promote its post-division degradation in somatic cells through ZIF-1-dependent mechanisms (pqac-00000025, pqac-00000026, pqac-00000028, pqac-00000029) | Germline determinant whose posterior enrichment and somatic clearance help distinguish germline from soma (pqac-00000000, pqac-00000028) |
| POS-1 | Posterior cytoplasm and germline blastomeres | Opposed by MEX-5/6; MEX-5/6 help restrict POS-1 to germline by promoting ZIF-1 expression in soma and by competing for shared RNA substrates that alter POS-1 mobility (pqac-00000000, pqac-00000026, pqac-00000028) | CCCH zinc-finger cell fate determinant contributing to posterior/germline identity; must be excluded or degraded in somatic blastomeres (pqac-00000000, pqac-00000028) |
| PLK-1 | Enriched in the anterior cytoplasm/cells | Physical interactor recruited by MEX-5/6; association with polo-box domains helps generate anterior PLK-1 enrichment, and MEX-5-dependent PLK-1 activity promotes polarization of posterior determinants such as POS-1 and MEX-1 (pqac-00000001, pqac-00000025) | Promotes somatic cell-cycle features and phosphorylation-dependent segregation dynamics downstream of the MEX-5/6 gradient (pqac-00000000, pqac-00000025) |
| ZIF-1 | Expressed in somatic blastomeres where its translation is activated | Key downstream effector positively regulated at the translational level by MEX-5/6 through the zif-1 3'UTR; executes degradation of CCCH zinc-finger germline proteins in soma (pqac-00000001, pqac-00000004, pqac-00000028) | SOCS-box/E3 ubiquitin ligase substrate adaptor that clears PIE-1, POS-1, and related germ plasm proteins from somatic lineages (pqac-00000000, pqac-00000004, pqac-00000028) |
| P granules / PGL-3 condensates | Posterior cytoplasm and germline blastomeres | Indirectly antagonized by MEX-5/6; MEX-5-driven RNA competition dissolves PGL-3/RNA condensates in the anterior, while low MEX-5/6 posteriorly permits granule stability and germ plasm retention (pqac-00000014, pqac-00000015, pqac-00000017, pqac-00000019) | Membraneless germ plasm condensates whose posterior assembly/retention supports germ cell fate, whereas anterior disassembly prevents ectopic germline specification in soma (pqac-00000002, pqac-00000014, pqac-00000015) |


*Table: This table summarizes the core components of the MEX-6/MEX-5 polarity and germline-specification pathway in the early C. elegans embryo. It highlights where each component localizes, how it relates to MEX-5/6, and the specific function it serves in asymmetric cell fate regulation.*