title: The PAM-1 aminopeptidase regulates centrosome positioning to ensure anterior-posterior axis specification in one-cell C. elegans embryos.
abstract: In the one-cell Caenorhabditis elegans embryo, the anterior-posterior (A-P) axis is established when the sperm donated centrosome contacts the posterior cortex. While this contact appears to be essential for axis polarization, little is known about the mechanisms governing centrosome positioning during this process. pam-1 encodes a puromycin sensitive aminopeptidase that regulates centrosome positioning in the early embryo. Previously we showed that pam-1 mutants fail to polarize the A-P axis. Here we show that PAM-1 can be found in mature sperm and in cytoplasm throughout early embryogenesis where it concentrates around mitotic centrosomes and chromosomes. We provide further evidence that PAM-1 acts early in the polarization process by showing that PAR-1 and PAR-6 do not localize appropriately in pam-1 mutants. Additionally, we tested the hypothesis that PAM-1's role in polarity establishment is to ensure centrosome contact with the posterior cortex. We inactivated the microtubule motor dynein, DHC-1, in pam-1 mutants, in an attempt to prevent centrosome movement from the cortex and restore anterior-posterior polarity. When this was done, the aberrant centrosome movements of pam-1 mutants were not observed and anterior-posterior polarity was properly established, with proper localization of cortical and cytoplasmic determinants. We conclude that PAM-1's role in axis polarization is to prevent premature movement of the centrosome from the posterior cortex, ensuring proper axis establishment in the embryo.
authors.affiliation: Department of Biology, Ursinus College, Collegeville, PA 19426, USA.
authors.forename: Samantha M
authors.initials: SM
authors.lastname: Fortin
authors.forename: Sara L
authors.initials: SL
authors.lastname: Marshall
authors.forename: Eva C
authors.initials: EC
authors.lastname: Jaeger
authors.forename: Pauline E
authors.initials: PE
authors.lastname: Greene
authors.forename: Lauren K
authors.initials: LK
authors.lastname: Brady
authors.forename: R Elwyn
authors.initials: RE
authors.lastname: Isaac
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Schrandt
authors.forename: Darren R
authors.initials: DR
authors.lastname: Brooks
authors.forename: Rebecca
authors.initials: R
authors.lastname: Lyczak
mesh_terms: D000626:Aminopeptidases / Q000378:metabolism*; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics; D002477:Cells; D022082:Cellular Structures; D018385:Centrosome; D003593:Cytoplasm; D019422:Dietary Sucrose; D004398:Dyneins; D005526:Food, Formulated; D008297:Male; D008870:Microtubules; D013094:Spermatozoa
chemical_list: D019422:Dietary Sucrose; C082131:Ensure formulated food; D000626:Aminopeptidases; C025579:enkephalin degrading enzyme; D004398:Dyneins