April 16, 2013

I’m as type-A as a person can get, with my organized desk, to-do lists, and inability to roll with it (I sound dreadful, right?).  One thing that will never change is the calm I feel when I read the word “systematic” in a paper’s title or abstract.  Anything done systematically soothes me like a heartbeat soothes a newborn.  Today’s image is from a paper that uses a—you guessed it—systematic approach to understanding the roles of dynein and its many regulators in mitosis.

Dynein is a large microtubule motor complex that is important in countless cellular processes, most notably mitosis.  Like most proteins, dynein relies on numerous adaptor proteins and the dynactin complex to help localize the motor and/or activate it.  A recent paper uses siRNA screening to systematically test the roles of dynein subunits, adaptor proteins, and dynactin subunits to build a more complete picture of the roles of each protein in mitosis.  Raaijmakers and colleagues show that while some regulators are required for activation but not localization of dynein, others are required mainly for dynein localization.  Dynactin, for example, is not necessary for spindle organization, but rather serves as a dynein recruitment factor at the nuclear envelope and kinetochores.  In the images above, the mitotic spindle in a control cell is very focused at spindle poles (second row, green in merged).  When the dynein heavy chain subunit is depleted from cells (all other columns), spindles show a range of spindle pole focusing defects, including spindles lacking attachment to their poles.  Spindle microtubules are top row, red in merged; chromosomes are third row, blue in merged.

Raaijmakers, J., Tanenbaum, M., & Medema, R. (2013). Systematic dissection of dynein regulators in mitosis originally published in the Journal of Cell Biology, 201 (2), 201-215 DOI: 10.1083/jcb.201208098