Asymmetric cell division is essential to generate cellular diversity. In many animal cells, the cleavage plane lies perpendicular to the mitotic spindle, and it is the spindle positioning that dictates the size of the daughter cells. Although some properties of spindle positioning are conserved between distantly related model species and different cell types, little is known of the evolutionary...

Adducin-1 moonlights at the mitotic spindle A n actin-binding protein helps shape the mitotic spindle, Chan et al. report. Researchers long thought that actin and microtubules performed different tasks during mitosis. They believed that micro tubules formed the mitotic spindle that pulls chromosomes apart, whereas actin joined with myosin to produce the contractile furrow that separates the mot...

Size specification of macromolecular assemblies in the cytoplasm is poorly understood [1]. In principle, assemblies could scale with cell size or use intrinsic mechanisms. For the mitotic spindle, scaling with cell size is expected, because the function of this assembly is to physically move sister chromatids into the center of nascent daughter cells. Eggs of Xenopus laevis are among the larges...

Faithful chromosome segregation, during meiosis, is of critical importance to prevent aneuploidy in the resulting embryo. In mammalian oocytes, the segregation of homologous chromosomes takes place with the spindle located at the cell's periphery. The spindle is often assembled close to the centre of the cell, which necessitates the actin network for spindle transport to the cell cortex. In thi...

Early development of many animals is characterized by rapid cleavages that dramatically decrease cell size, but how the mitotic spindle adapts to changing cell dimensions is not understood. To identify mechanisms that scale the spindle during Xenopus laevis embryogenesis, we established an in vitro system using cytoplasmic extracts prepared from embryos that recapitulates in vivo spindle size d...

We describe the case of a 70-year-old man with unicentric grade 1 epitheloid hemangioendothelioma (EH) of the bone that favourably responded to intravenous pamidronate as a single agent. After 6 years of follow-up, the patient was in complete remisssion. We suggest that use of bisphosphonates should be considered in the treatment of osteolytic EH.

Mitotic spindle orientation is crucial for symmetric vs asymmetric cell division and depends on astral microtubules. Here, we show that distinct subpopulations of astral microtubules exist, which have differential functions in regulating spindle orientation and division symmetry. Specifically, in polarized stem cells of developing mouse neocortex, astral microtubules reaching the apical and bas...

Analysis of benign and malignant mouse skin tumors had previouslyshown that amplification of a mutant H-ras alÃ-eleor loss of the normal alÃ-elewas generally seen only in high grade or spindle cell tumors. The normal:mutant ras gene dosage has been studied directly by polymerase chain reaction amplification of DNA derived from paraffin sections of carcinomas of defined histolÃ3gica!types. Some ...

Spindle alignment is the process in which the two spindle poles are directed toward preselected and opposite cell ends. In budding yeast, the APC-related molecule Kar9 is required for proper alignment of the spindle with the mother-bud axis. We find that Kar9 localizes to the prospective daughter cell spindle pole. Kar9 is transferred from the pole to cytoplasmic microtubules, which are then gu...