Nuclear positioning: mechanisms and functions.

The nucleus is the largest organelle in the cell and its position is dynamically controlled in space and time, although the functional significance of this dynamic regulation is not always clear. Nuclear movements are mediated by the cytoskeleton which transmits pushing or pulling forces onto the nuclear envelope. Recent studies have shed light on the mechanisms regulating nuclear positioning inside the cell. While microtubules have been known for a long time to be key players in nuclear positioning, the actin and cytoplasmic intermediate filament cytoskeletons have been implicated in this function more recently and various molecular links between the nuclear envelope and cytoplasmic elements have been identified. In this review, we summarize the recent advances in our understanding of the molecular mechanisms involved in the regulation of nuclear localization in various animal cells and give an overview of the evidence suggesting a crucial role of nuclear positioning in cell polarity and physiology and the consequences of nuclear mispositioning in human pathologies.