Cortical interneurons migrating on a pure substrate of N-cadherin exhibit fast synchronous centrosomal and nuclear movements and reduced ciliogenesis

Abstract

The embryonic development of the cortex involves a phase of long distance migration of interneurons born in the basal telencephalon. Interneurons first migrate tangentially and then reorient their trajectories radially to enter the developing cortex. We have shown that migrating interneurons can assemble a primary cilium, which maintains the centrosome to the plasma membrane and processes signals to control interneuron trajectory (Baudoin et al., 2012). In the developing cortex, N-cadherin is expressed by migrating interneurons and by cells in their migratory pathway. N-cadherin promotes the motility and maintains the polarity of tangentially migrating interneurons (Luccardini et al., 2013). Because N-cadherin is an important factor that regulates the migration of medial ganglionic eminence (MGE) cells in vivo, we further characterized the motility and polarity of MGE cells on a substrate that only comprises this protein. MGE cells migrating on a N-cadherin substrate were seven times faster than on a laminin substrate and two times faster than on a substrate of cortical cells. A primary cilium was much less frequently observed on MGE cells migrating on N-cadherin than on laminin. Nevertheless, the mature centriole (MC) frequently docked to the plasma membrane in MGE cells migrating on N-cadherin, suggesting that plasma membrane docking is a basic feature of the centrosome in migrating MGE cells. On the N-cadherin substrate, centrosomal and nuclear movements were remarkably synchronous and the centrosome remained near the nucleus. Interestingly, MGE cells with cadherin invalidation presented centrosomal movements no longer coordinated with nuclear movements. In summary, MGE cells migrating on a pure substrate of N-cadherin show fast, coordinated nuclear and centrosomal movements, and rarely present a primary cilium.

Topographical cues control the morphology and dynamics of migrating cortical interneurons

“…To test the role of topographical cues on cortical interneuron migration, we adapted an in vitro approach commonly used by us and others to study the migration of cortical interneurons [55][56][57][58][59]. The medial ganglionic eminence (MGE) which produces the largest number of cortical interneurons [60,61] can by dissected out and cultured as small explants either on cortical cells or on flat coated substrates [31,62]. A cardinal property of the MGE is to release cells expressing GABA and neuronal markers able to migrate a long distance away [63,64].…”

“…Fluorescent live or fixed cells can be imaged at various magnifications through the thin layer of PDMS, and immunostaining is easily performed. Before culture, the microstructured substrates were functionalized with a homogeneous coating of laminin and N-cadherin, two adhesion molecules promoting both interneuron polarization and migration [31,53,62]. On these substrates, MGE explants released polarized cells that colonized the surrounding substrate for approximately 24 hours (Fig.1B).…”

JNK signaling controls branching, nucleokinesis, and positioning of centrosomes and primary cilia in migrating cortical interneurons

“…The centrosome is tethered to the nucleus through a perinuclear cage of microtubules and acts to generate a forward pulling force on the nucleus during nucleokinesis (Bellion et al, 2005; Umeshima et al, 2007). Disruptions in centrosome motility and positioning are thought to underly nucleokinesis defects seen in other studies of neuronal migration (Luccardini et al, 2013; Luccardini et al, 2015; Silva et al, 2018; Solecki et al, 2009). Since we found significant defects in nucleokinesis in migrating MGE interneurons, we sought to determine if centrosome dynamics were also disrupted during JNK inhibition.…”

“…Two cellular mechanisms that enable interneurons to make these complex migratory decisions are leading process branching, where cortical interneurons dynamically remodel their leading processes to sense and respond to extracellular guidance cues, and nucleokinesis, where interneurons propel their cell bodies forward in the selected direction of migration (Ang et al, 2003; Bellion et al, 2005; Moya and Valdeolmillos, 2004; Nadarajah et al, 2003; Polleux et al, 2002). Moreover, proper positioning and signaling from two subcellular organelles, the centrosome and primary cilium, have been implicated in the guided migration of cortical interneurons (Higginbotham et al, 2012; Luccardini et al, 2013; Luccardini et al, 2015; Yanagida et al, 2012). Failure to coordinate these cellular and subcellular events can alter cortical interneuron migration and impair the development of cortical circuitry, which may underlie severe neurological disorders such as autism spectrum disorder, schizophrenia, and epilepsy (Hildebrandt et al, 2011; Kato and Dobyns, 2005; Meechan et al, 2012; Volk et al, 2015).…”

Topographical cuescontrol the morphology and dynamics of migrating cortical interneurons

“…Fluorescent live or fixed cells can be imaged at various magnifications through the thin layer of PDMS, and immunostaining is easily performed. Before culture, the microstructured substrates were functionalized with a homogeneous coating of laminin and Ncadherin, two adhesion molecules promoting both interneuron polarization and migration [31,54,56]. Explants from the medial ganglionic eminence (MGE), the main source of cortical interneurons, were dissected from mouse brain embryos.…”