The polarity protein Pard3 is required for centrosome positioning during neurulation

Abstract

SUMMARY Microtubules are essential regulators of cell polarity, architecture and motility. The organization of the microtubule network is context-specific. In non-polarized cells, microtubules are anchored to the centrosome and form radial arrays. In most epithelial cells, microtubules are noncentrosomal, align along the apico-basal axis and the centrosome templates a cilium. It follows that cells undergoing mesenchyme-to-epithelium transitions must reorganize their microtubule network extensively, yet little is understood about how this process is orchestrated. In particular, the pathways regulating the apical positioning of the centrosome are unknown, a central question given the role of cilia in fluid propulsion, sensation and signaling. In zebrafish, neural progenitors undergo progressive epithelialization during neurulation, and thus provide a convenient in vivo cellular context in which to address this question. We demonstrate here that the microtubule cytoskeleton gradually transitions from a radial to linear organization during neurulation and that microtubules function in conjunction with the polarity protein Pard3 to mediate centrosome positioning. Pard3 depletion results in hydrocephalus, a defect often associated with abnormal cerebrospinal fluid flow that has been linked to cilia defects. These findings thus bring to focus cellular events occurring during neurulation and reveal novel molecular mechanisms implicated in centrosome positioning.

Centrosome movements in vivo correlate with specific neurite formation downstream of LIM homeodomain transcription factor activity

“…The centrosome, through its inherent MTorganizing activity and complex protein composition (Bornens, 2002;Doxsey, 2001), as well as its associations with other cellular organelles (Badano et al, 2005), could mediate multiple processes to influence axon formation or neurite identity in multipolar cells. The Golgi apparatus, which is crucial for directional protein transport (Sütterlin and Colanzi, 2010) and is a significant source of MTs in polarized migrating cells (Efimov et al, 2007), has been shown to colocalize with the centrosome (de Anda et al, 2010;de Anda et al, 2005;Hong et al, 2010;Pouthas et al, 2008;Zmuda and Rivas, 1998). Perhaps centrosome positioning at the base of a nascent axon is important not only for creating a polarized MT network, but also for regulating selective transport and trafficking of molecules that define axon identity.…”

“…Here, we found that DN-CLIM causes apical mispositioning of the centrosome and reduces its motility. Interestingly, the centrosome not only regulates MT assembly and organization, but its position and motility are also controlled by MT dynamics (de Anda et al, 2010;Hong et al, 2010). LIM-HD activity could potentially regulate any of these processes.…”

“…During neurulation and prior to neuronal differentiation, the centrosome is apically localized in neuroepithelial cells (Hong et al, 2010), but little is known about how or whether its position changes during neuronal differentiation. We previously defined four stages of RB development: central axon initiation, which we refer to here as phase 0, and subsequent phases I-III (Andersen et al, 2011).…”

Wnt/PCP signaling controls intracellular position of MTOCs during gastrulation convergence and extension movements

“…apicalbasal polarity). In epithelia, centrosomes are typically located near the apical surface (Hay, 2005;Baum et al, 2008;Hong et al, 2010), whereas in migrating mesenchymal cells, centrosomes frequently assume a position between the leading edge and the nucleus. During zebrafish gastrulation, lateral ectoderm and mesoderm cells migrate towards the dorsal midline as a cohesive sheet or as individual cells, respectively (Solnica-Krezel, 2005).…”

Quantitative cell polarity imaging defines leader-to-follower transitions during collective migration and the key role of microtubule-dependent adherens junction formation

“…Moreover, nucleus-centrosome axes provide information on the organisation of the microtubule network, which is cell type specific (Bacallao et al, 1989;Meads and Schroer, 1995;Müsch, 2004;Brodu et al, 2010;Hong et al, 2010). It is known that microtubules regulate, and are regulated by, points of cell-cell contact (Chausovsky et al, 2000;Waterman-Storer et al, 2000;Yap and Manley, 2001;Ligon and Holzbaur, 2007), raising the possibility that microtubule network organisation is regulated at the supracellular or tissue level, as has recently been shown for the actomyosin system (Martin et al, 2009;Rauzi et al, 2010).…”