NuMA is required for proper spindle assembly and chromosome alignment in prometaphase.
BACKGROUND
NuMA is a protein that has been previously shown to play a role in focusing microtubules at the mitotic spindle poles. However, most previous work relies on experimental methods that might cause dominant side effects on spindle formation, such as microinjection of antibodies, overexpression of mutant protein, or immunodepletion of NuMA-containing protein complexes.


RESULTS
To circumvent these technical problems, we performed siRNA experiments in which we depleted the majority of NuMA in human cultured cells. Depleted mitotic cells show a prolonged duration of prometaphase, with spindle pole defects and with unattached, unaligned chromosomes.


CONCLUSIONS
Our data confirm that NuMA is important for spindle pole formation, and for cohesion of centrosome-derived microtubules with the bulk of spindle microtubules. Our findings of NuMA-dependent defects in chromosome alignment suggest that NuMA is involved in stabilizing kinetochore fibres.
Haren
Laurence
L
Wellcome Trust Centre for Cell Biology, University of Edinburgh, King's Buildings, Edinburgh EH9 3JR, UK. laurence.haren@istmt.cnrs.fr
Gnadt
Nicole
N
Wright
Michel
M
Merdes
Andreas
A