Limits...
Molecules and mechanisms that regulate multipolar migration in the intermediate zone.

Cooper JA - Front Cell Neurosci (2014)

Bottom Line: This reorientation implies the existence of directional signals in the IZ that are ignored during the multipolar stage but sensed after axonogenesis.Other signals are implicated in starting multipolar migration and triggering axon outgrowth.Here we review the molecules and mechanisms that regulate multipolar migration, and also discuss how multipolar migration affects the orderly arrangement of neurons in layers and columns in the developing neocortex.

View Article: PubMed Central - PubMed

Affiliation: Fred Hutchinson Cancer Research Center, Division of Basic Sciences Seattle, Washington, USA.

ABSTRACT
Most neurons migrate with an elongated, "bipolar" morphology, extending a long leading process that explores the environment. However, when immature projection neurons enter the intermediate zone (IZ) of the neocortex they become "multipolar". Multipolar cells extend and retract cytoplasmic processes in different directions and move erratically-sideways, up and down. Multipolar cells extend axons while they are in the lower half of the IZ. Remarkably, the cells then resume radial migration: they reorient their centrosome and Golgi apparatus towards the pia, transform back to bipolar morphology, and commence locomotion along radial glia (RG) fibers. This reorientation implies the existence of directional signals in the IZ that are ignored during the multipolar stage but sensed after axonogenesis. In vivo genetic manipulation has implicated a variety of candidate directional signals, cell surface receptors, and signaling pathways, that may be involved in polarizing multipolar cells and stabilizing a pia-directed leading process for radial migration. Other signals are implicated in starting multipolar migration and triggering axon outgrowth. Here we review the molecules and mechanisms that regulate multipolar migration, and also discuss how multipolar migration affects the orderly arrangement of neurons in layers and columns in the developing neocortex.

No MeSH data available.


Different timing of intermediate zone exit influences cortical lamination Neurons spend variable times migrating in the intermediate zone (IZ). Postmitotic neurons derived directly from radial glia (i.e., radial glia daughters, RGD) spend approximately 2 days in the IZ before entering the cortical plate (CP). Intermediate progenitors (IP) divide to create intermediate progenitor daughters (IPDs), for a total time of approximately 5 days in the IZ. As a result RGD born on day 0 (RGD1) arrive at the top of the CP 2–3 days before IPDs whose mother IP also left the VZ on day 0. As a result the IPDs layer above RGD1, and co-layer with RGD2, born 2 days later. If neuron fate is fixed at the last RG division, then this would cause mixing of neurons of different fates in the same layer.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4231986&req=5

Figure 4: Different timing of intermediate zone exit influences cortical lamination Neurons spend variable times migrating in the intermediate zone (IZ). Postmitotic neurons derived directly from radial glia (i.e., radial glia daughters, RGD) spend approximately 2 days in the IZ before entering the cortical plate (CP). Intermediate progenitors (IP) divide to create intermediate progenitor daughters (IPDs), for a total time of approximately 5 days in the IZ. As a result RGD born on day 0 (RGD1) arrive at the top of the CP 2–3 days before IPDs whose mother IP also left the VZ on day 0. As a result the IPDs layer above RGD1, and co-layer with RGD2, born 2 days later. If neuron fate is fixed at the last RG division, then this would cause mixing of neurons of different fates in the same layer.

Mentions: Time-lapse recordings and birthdating studies indicate that MP migration lasts for at least a day in the mouse, but the timing is very heterogeneous (Noctor et al., 2004; Westerlund et al., 2011). Neurons that spend longer in the MP phase are expected to arrive later at the top of the CP than neurons that travel more rapidly. This means they will enter higher cortical layers. Since neuron fate is thought to be fixed at the last division of the RG progenitor, different transit times are expected to blur the discrete layering of neuronal subtypes that characterizes the mature cortex (Molyneaux et al., 2007; Figure 4). It remains unclear whether or how the varied timing of MP migration is compensated at other stages of development.


Molecules and mechanisms that regulate multipolar migration in the intermediate zone.

Cooper JA - Front Cell Neurosci (2014)

Different timing of intermediate zone exit influences cortical lamination Neurons spend variable times migrating in the intermediate zone (IZ). Postmitotic neurons derived directly from radial glia (i.e., radial glia daughters, RGD) spend approximately 2 days in the IZ before entering the cortical plate (CP). Intermediate progenitors (IP) divide to create intermediate progenitor daughters (IPDs), for a total time of approximately 5 days in the IZ. As a result RGD born on day 0 (RGD1) arrive at the top of the CP 2–3 days before IPDs whose mother IP also left the VZ on day 0. As a result the IPDs layer above RGD1, and co-layer with RGD2, born 2 days later. If neuron fate is fixed at the last RG division, then this would cause mixing of neurons of different fates in the same layer.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4231986&req=5

Figure 4: Different timing of intermediate zone exit influences cortical lamination Neurons spend variable times migrating in the intermediate zone (IZ). Postmitotic neurons derived directly from radial glia (i.e., radial glia daughters, RGD) spend approximately 2 days in the IZ before entering the cortical plate (CP). Intermediate progenitors (IP) divide to create intermediate progenitor daughters (IPDs), for a total time of approximately 5 days in the IZ. As a result RGD born on day 0 (RGD1) arrive at the top of the CP 2–3 days before IPDs whose mother IP also left the VZ on day 0. As a result the IPDs layer above RGD1, and co-layer with RGD2, born 2 days later. If neuron fate is fixed at the last RG division, then this would cause mixing of neurons of different fates in the same layer.
Mentions: Time-lapse recordings and birthdating studies indicate that MP migration lasts for at least a day in the mouse, but the timing is very heterogeneous (Noctor et al., 2004; Westerlund et al., 2011). Neurons that spend longer in the MP phase are expected to arrive later at the top of the CP than neurons that travel more rapidly. This means they will enter higher cortical layers. Since neuron fate is thought to be fixed at the last division of the RG progenitor, different transit times are expected to blur the discrete layering of neuronal subtypes that characterizes the mature cortex (Molyneaux et al., 2007; Figure 4). It remains unclear whether or how the varied timing of MP migration is compensated at other stages of development.

Bottom Line: This reorientation implies the existence of directional signals in the IZ that are ignored during the multipolar stage but sensed after axonogenesis.Other signals are implicated in starting multipolar migration and triggering axon outgrowth.Here we review the molecules and mechanisms that regulate multipolar migration, and also discuss how multipolar migration affects the orderly arrangement of neurons in layers and columns in the developing neocortex.

View Article: PubMed Central - PubMed

Affiliation: Fred Hutchinson Cancer Research Center, Division of Basic Sciences Seattle, Washington, USA.

ABSTRACT
Most neurons migrate with an elongated, "bipolar" morphology, extending a long leading process that explores the environment. However, when immature projection neurons enter the intermediate zone (IZ) of the neocortex they become "multipolar". Multipolar cells extend and retract cytoplasmic processes in different directions and move erratically-sideways, up and down. Multipolar cells extend axons while they are in the lower half of the IZ. Remarkably, the cells then resume radial migration: they reorient their centrosome and Golgi apparatus towards the pia, transform back to bipolar morphology, and commence locomotion along radial glia (RG) fibers. This reorientation implies the existence of directional signals in the IZ that are ignored during the multipolar stage but sensed after axonogenesis. In vivo genetic manipulation has implicated a variety of candidate directional signals, cell surface receptors, and signaling pathways, that may be involved in polarizing multipolar cells and stabilizing a pia-directed leading process for radial migration. Other signals are implicated in starting multipolar migration and triggering axon outgrowth. Here we review the molecules and mechanisms that regulate multipolar migration, and also discuss how multipolar migration affects the orderly arrangement of neurons in layers and columns in the developing neocortex.

No MeSH data available.