Mid1/anillin and the spatial regulation of cytokinesis in fission yeast.

Cell division is a critical and irreversible step in the cell cycle. The strategies that cells follow to regulate the position of the division plane must take into account the global geometry of the cell as well as position of the genetic material to ensure its accurate segregation into daughter cells of a given cell shape and size. Along the years, research on Schizosaccharomyces pombe, a well-recognized model organism for cell division studies has allowed a detailed molecular understanding of the spatial mechanisms regulating cytokinesis. Division plane position in this unicellular rod-shaped organism, which divides by the assembly and constriction of a medially placed actomyosin ring, largely depends on the anillin-like protein Mid1. Therefore, the major pathways controlling the position of the division plane converge on Mid1. In this review, we make an overview of the studies that have deciphered how Mid1 localization and scaffolding activities are controlled over the cell cycle to ensure the symmetrical division of fission yeast cells. These studies have revealed new mechanisms generating spatial information based on nuclear shuttling of the division plane factor Mid1 and on the establishment of cortical inhibitory gradients of the cell polarity kinase Pom1.