PT  - JOURNAL ARTICLE
AU  - Daniela Londono Vasquez
AU  - Katherine Rodriguez-Lukey
AU  - Susanta K. Behura
AU  - Ahmed Z. Balboula
TI  - Cytoplasmic Microtubule Organizing Centers Regulate Meiotic Spindle Positioning in Mouse Oocyte
AID  - 10.1101/2020.06.25.172684
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.06.25.172684
4099  - http://biorxiv.org/content/early/2020/06/26/2020.06.25.172684.short
4100  - http://biorxiv.org/content/early/2020/06/26/2020.06.25.172684.full
AB  - During oocyte meiosis, migration of the spindle and its positioning must be tightly regulated to ensure elimination of the polar bodies and provide developmentally competent euploid eggs. Although the role of F-actin in regulating these critical processes has been studied extensively, little is known whether microtubules (MTs) participate in regulating these processes. Here, we characterize a pool of MTOCs in the oocyte that does not contribute to spindle assembly but instead remains free in the cytoplasm during metaphase I (metaphase cytoplasmic MTOCs; mcMTOCs). In contrast to spindle pole MTOCs, which primarily originate from the perinuclear region in prophase I, the mcMTOCs are found near the cortex of the oocyte. At nuclear envelope breakdown, they exhibit robust nucleation of MTs, which diminishes during polar body extrusion before returning robustly during metaphase II. The asymmetric positioning of the mcMTOCs provides the spindle with a MT-based anchor line to the cortex opposite the site of polar body extrusion. Depletion of mcMTOCs, by laser ablation, or manipulating their numbers, through inhibitors or inducers of autophagy, revealed that the mcMTOCs are required to regulate the timely migration and positioning of the spindle in meiosis. We discuss how forces exerted by F-actin in mediating movement of the spindle to the oocyte cortex are balanced by MT-mediated forces from the mcMTOCs to ensure spindle positioning.Competing Interest StatementThe authors have declared no competing interest.