Submission Date

5-4-2026

Document Type

Paper- Restricted to Campus Access

Department

Biology

Adviser

Rebecca Lyczak

Committee Member

Denise Finney

Committee Member

Elizabeth Bain

Department Chair

Denise Finney

Project Description

Caenorhabditis elegans serve as an exemplary model organism for understanding the mechanisms coordinating centrosome maturation with cell cycle progression during early embryogenesis. Proper timing of these events is essential for accurate spindle assembly and polarity establishment, yet the mechanism(s) linking them remain incompletely understood. The aminopeptidase PAM-1 is required for normal centrosome behavior, and pam-1 mutants exhibit premature centrosome maturation, polarity defects, and delays in mitotic progression, among additional defects. Because PAM-1 also influences CDK-1 activation, I asked whether pam-1 phenotypes arise from disrupted cell cycle timing, centrosome intrinsic defects, or both, and whether these abnormalities can be rescued by reducing WEE-1.3 activity, a negative regulator of CDK-1. To address this, I quantified centrosome maturation and mitotic timing across wildtype, pam-1, and pam-1;wee-1.3(lz5) embryos. pam-1 mutants displayed premature tubulin enlargement, a phenotype fully rescued by WEE-1.3 suppression, indicating a CDK-1-dependent timing defect. In contrast, premature spindle formation before rotation persisted in the suppressor strain, revealing a CDK-1 independent requirement for PAM-1. Mitotic timing analysis revealed that the prolonged interval from pronuclear envelope breakdown (PNEBD) to spindle alignment in pam-1 embryos was fully restored to wildtype duration by WEE-1.3 suppression, whereas the extended PNEBD-cytokinesis interval was only partially rescued. Early pronuclear events, measured as the cortical contraction-PNEBD interval, showed no significant differences among all three strains. Together, these findings demonstrate that PAM-1 regulates centrosome maturation and mitotic timing through both CDK-1-dependent and centrosome intrinsic pathways. WEE-1.3 suppression selectively restores synchrony between centrosome maturation and the cell cycle, revealing distinct mechanistic origins for the diverse defects expressed in pam-1 mutants.

Comments

Funding for part of this research was provided by the National Institutes of Health grant (ID: 2R15GM110614-03).

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