Linking Cell Polarity to Cortical Development and Malformations

Cell polarity refers to the asymmetric distribution of signaling molecules, cellular organelles, and cytoskeleton in a cell. Neural progenitors and neurons are highly polarized cells in which the cell membrane and cytoplasmic components are compartmentalized into distinct functional domains in response to internal and external cues that coordinate polarity and behavior during development and disease. In neural progenitor cells, polarity has a prominent impact on cell shape and coordinate several processes such as adhesion, division, and fate determination. Polarity also accompanies a neuron from the beginning until the end of its life. It is essential for development and later functionality of neuronal circuitries. During development, polarity governs transitions between multipolar and bipolar during migration of postmitotic neurons, and directs the specification and directional growth of axons. Once reaching final positions in cortical layers, neurons form dendrites which become compartmentalized to ensure proper establishment of neuronal connections and signaling. Changes in neuronal polarity induce signaling cascades that regulate cytoskeletal changes, as well as mRNA, protein, and vesicle trafficking, required for synapses to form and function. Hence, defects in establishing and maintaining cell polarity are associated with several neural disorders such as microcephaly, lissencephaly, schizophrenia, autism, and epilepsy. In this review we summarize the role of polarity genes in cortical development and emphasize the relationship between polarity dysfunctions and cortical malformations.

[Bardet-Biedl syndrome: cilia and obesity - from genes to integrative approaches]

The primary cilium is a specialized organelle, present at the surface of most eukaryotic cells, whose main function is to detect, integrate and transmit intra- and extra-cellular signals. Its dysfunction usually results in a group of severe clinical manifestations nowadays termed ciliopathies. The latter can be of syndromic nature with multi-organ dysfunctions and can also be associated with a morbid obese phenotype, like it is the case in the iconic ciliopathy, the Bardet Biedl syndrome (BBS). This review will discuss the contribution of the unique context offered by the emblematic BBS for understanding the mechanisms leading to obesity via the involvement of the primary cilium together with identification of novel molecular players and signaling pathways it has helped to highlight. In the current context of translational medicine and system biology, this article will also discuss the potential benefits and challenges posed by these techniques via multi-level approaches to better dissect the underlying mechanisms leading to the complex condition of obesity.