Identification of the lz4 Suppressor of pam-1 and its Role in Polarity Establishment in Single-cell C. elegans Embryos
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In the nematode Caenorhabditis elegans, cell polarity in the single-cell embryo is indicative of anterior-posterior (AP) axis formation, which is essential for future functional potential. AP axis polarization is initiated by the sperm-donated centrosome contacting the posterior cortex of the embryo resulting in a destabilization of the actomyosin cytoskeleton and eventually polarity establishment. If the centrosome prematurely departs from the posterior cortex, it causes a disruption in PAR protein localization, thus hindering AP axis formation. PAM-1, a puromycin-sensitive aminopeptidase, reinforces two redundant polarization establishment pathways through prolonged centrosome contact with the posterior cortex. pam-1 mutants lack a functional PAM-1 protein, and exhibit a series of abnormalities in polarity landmarks culminating in the failure to properly polarize. Our lab has identified seven suppressor mutations, (lz1-7) of pam-1, which partially rescue the pam-1 phenotype. We have hypothesized that lz4 is a bypass or downstream suppressor of pam-1 and that centrosome dynamics in lz4 strains would resemble wild-type. To establish the relationship of lz4, pam-1 and their targets, I investigated the previously proposed gene identity of lz4, Y48G1C.10, and created a new strain, US127, to investigate lz4 suppression using confocal microscopy. RNAi, and DNA sequencing demonstrated that Y48 was not lz4¸ but I have proposed a new candidate gene, mppa-1, from the same chromosomal region. Analysis of US127 revealed that its centrosome-cortex contact duration was no different from pam-1, and is thus inconsistent with our hypothesis by acting instead through some other mechanism or pathway.
Stephens, Dylan, "Identification of the lz4 Suppressor of pam-1 and its Role in Polarity Establishment in Single-cell C. elegans Embryos" (2017). Biology Honors Papers. 14.