Development and dynamics of cell polarity at a glance

Abstract

Cells exhibit morphological and molecular asymmetries that are broadly categorized as cell polarity. The cell polarity established in early embryos prefigures the macroscopic anatomical asymmetries characteristic of adult animals. For example, eggs and early embryos have polarized distributions of RNAs and proteins that generate global anterior/posterior and dorsal/ventral axes. The molecular programs that polarize embryos are subsequently reused in multiple contexts. Epithelial cells require apical/basal polarity to establish their barrier function. Migrating cells polarize in the direction of movement, creating distinct leading and trailing structures. Asymmetrically dividing stem cells partition different molecules between themselves and their daughter cells. Cell polarity can develop de novo, be maintained through rounds of cell division and be dynamically remodeled. In this Cell Science at a Glance review and poster, we describe molecular asymmetries that underlie cell polarity in several cellular contexts. We highlight multiple developmental systems that first establish cell/developmental polarity, and then maintain it. Our poster showcases repeated use of the Par, Scribble and Crumbs polarity complexes, which drive the development of cell polarity in many cell types and organisms. We then briefly discuss the diverse and dynamic changes in cell polarity that occur during cell migration, asymmetric cell division and in planar polarized tissues.

Upsetting the Balance: When Viruses Manipulate Cell Polarity Control

“…It is not clear whether SARS-CoV requires the E/PALS interaction for virus entry, but the interaction may contribute to virus budding. The importance of the Crumbs complex [245,246] in the control of polarity is shown clearly here; the mislocalization of just one Crm component completely disrupting the epithelial integrity, which may, in turn, be one cause of the particularly severe pathology of SARS.…”

The Stem Cell Division Theory of Cancer

“…The differential partitioning of 11 cell fate determinants (e.g., transcription factors and mRNAs) between the daughter cells is known to induce changes in cell behavior and fate [82][83][84][85][86]. Errors in the distribution of cell fate determinants can disrupt the balance between symmetric and asymmetric cell division [82,83,87,88], which can lead to the accumulation of cell divisions in stem cells (Figure 2). Cell division can also lead to failures to restore physical interactions with other tissue components.…”

“…It also comprises chemical and physical signals acting on the stem cell (e.g., hormones, growth factors, cytokines, signals from the nervous system, and local mechanical and electrical signals) [117][118][119]. It also includes the extracellular levels of nutrients (macronutrients and micronutrients), oxygen, protons (pH) and other ions (e.g., Na + and K + ), because stem cell behavior and fate is influenced by physiological changes in these parameters [88][89][90][91][92][93][94]96,[120][121][122][123][124]. The stem cell environment also includes any cell from any part of the body that produces any signal, cell, or non-cellular component controlling stem cell behavior or fate [47].…”

“…Importantly, numerous investigations have shown that ELF-EMFs can stimulate the division of stem cells and promote tissue regeneration [34,[186][187][188][189][190][191][192]. In addition, cell migration is regulated by physiological electric currents [123,[193][194][195], and ELF-EMFs are known to induce electric currents that can alter cell migration [34,88,191,192,[196][197][198]. Exposure to ELF-EMFs may therefore disrupt the migration of HSCs and alter their fate.…”

“…HSCs might reach an abnormal location more permissive for cell division upon disturbance by ELF-EMFs. Disruption of tissue polarity by ELF-EMFs may also alter the balance between symmetric and asymmetric cell division in stem cells [88,199]; this can lead to changes in stem cell fates that can promote the accumulation of cell divisions in stem cells (Figure 2). Although the precise mechanism by which ELF-EMFs increase the risk of childhood leukemia remains to be elucidated, evidence indicates that ELF-EMFs may promote the accumulation of cell divisions in HSCs through a direct or indirect mitogenic effect.…”