In this paper Angela Kita and Zac Swider tackled a longstanding question in cell biology: Does F-actin play a role in mitotic spindle assembly? Despite numerous attempts over the past 50 years, convincing evidence for spindle-associated F-actin filaments has been largely lacking. To address this question, Angela developed and rigorously tested a fixation protocol with the goal of preserving both actin filaments and microtubules. Angela showed that not only do actin filaments pervade the mitotic spindle, they are present in distinct populations throughout the entire cell cycle (seen below). Meanwhile Zac took a live imaging approach, which revealed that the actin filaments detected in fixed samples actually consist of two populations of F-actin: A relatively stable population that appears to be mechanically coupled to the spindle itself, and a population of dynamic F-actin cables that rapidly polymerize from the cell cortex and target the spindle poles (also seen below). Together these results show that the participation of actin filaments in mitotic spindle assembly is far more extensive than commonly believed. We hypothesize that these populations may be involved in spindle positioning and/or mitotic progression. . For more details read the whole paper here: pdf
