Tastin is required for bipolar spindle assembly and centrosome integrity during mitosis

Abstract

Tastin was previously characterized as an accessory protein for cell adhesion that participates in early embryo implantation. Here, we report that tastin is also required for spindle assembly during mitosis. Tastin protein levels peaked in the G(2)/M phase and abruptly declined after cell division. Microscopy showed that tastin is primarily localized on the microtubules, centrosomes, and the mitotic spindle during the cell cycle. Tastin interacted with the dynein intermediate chain, p150(Glued), and gamma-tubulin in addition to Tctex-1 (the light chain of dynein). Overexpression of tastin led to monopolar spindle formation, whereas loss of tastin expression caused profound mitotic block and preferentially induced multipolar spindles. These multipolar spindles were generated through a loss of cohesion in mitotic centrosomes; specifically, tastin depletion caused the fragmentation of pericentrosomal material and the splitting of the centrioles at the spindle poles. Tastin depletion induced centrosome abnormalities exclusively during mitosis and required both microtubule integrity and Eg5 activity. However, tastin depletion did not disrupt the organization of spindle poles, as revealed by localization of nuclear mitotic apparatus protein (NuMA) and the p150(Glued) component of dynactin. These data indicate that the major function of tastin during mitosis is to maintain the structural and dynamic features of centrosomes, thereby contributing to spindle bipolarity.

Cep57, a NEDD1-binding pericentriolar material component, is essential for spindle pole integrity

“…Thus, the centrosome must form a strong structure that can withstand the spindle microtubule-based tensions during mitosis. The loss of centriole cohesion and PCM factors, such as astrin [4], Kizuna [5] and tastin [6], leads to centriole disengagement and PCM fragmentation. The collapse of the centrosome yields new MTOCs and multiple spindle poles.…”

The pericentriolar satellite protein CEP90 is crucial for integrity of the mitotic spindle pole

“…Depletion of centrosomal components often results in monopolar or multipolar spindles, suggesting that centrosome integrity is crucial for maintenance of spindle bipolarity (Garrett et al, 2002;Cassimeris and Morabito, 2004;Cho et al, 2006;Oshimori et al, 2006;Thein et al, 2007;Yang et al, 2008;Wu et al, 2008). In addition, motor proteins, such as HSET and dynein, contribute to the focusing of spindle microtubules into poles (Gaglio et al, 1997;Gordon et al, 2001).…”

MLL5 Maintains Genomic Integrity by Regulating the Stability of the Chromosomal Passenger Complex via a Functional Interaction with Borealin

“…5B), suggesting that MLL5 may possess CPC-independent function in regulating mitotic spindle integrity. The origin of the multipolar mitosis is very diverse, which can arise from overamplification of centrosomes, interference with microtubule dynamics or spindle integrity defects (Oshimori et al, 2006;Tsou and Stearns, 2006;Yang et al, 2008). In fact, growing volume of evidence has shown that mutations of certain oncogenes and tumor suppressors disrupt the numeral and functional integrity of centrosomes and directly result in chromosome instability (Fukasawa, 2007).…”