During Brain Development Final Destinations for Neurons and Glia Get Separated from Germinal Niches

Transcription

1 During Brain Development Final Destinations for Neurons and Glia Get Separated from Germinal Niches

2 Progenitors are Contained within Unique Domains and Tangentially Fixed. EMBRYO ADULT

3 Migratory Behavior Varies According to Region

4 LGE

5 MGE

6 Radial Migration

7 Radial Glia Guided Migration Takes Young Neurons directly from the VZ to the Cortical Plate Guided by the Processes of Radial Glia; Maintains Topological Maps from thevz to the Cortical Plate Birth Migration Differentiation

8 Sequential Addition of Neurons During Development Desai and McConnell Development 127, (2000)

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10 Radial Glial Fibers as Guides for Neuronal Migration Rakic, 1972

11 Protomap Hypothesis Rakic, 1988

12 Radial Glia Guided Migration Continues in the Adult Brain of some Vertebrate Species

13 13

14 Marin and Rubenstein Ann Rev Neurosci (2003)

15 Initiation, Adhesion, Locomotion, Termination Marin and Rubenstein Ann Rev Neurosci (2003)

16 Gap Junctions (Elias and Kriegstein, TINS, 2008)

17 Asymmetrical Cx expression in bifurcated migrating neurons Cx43 Vimentin - radial glia Tuj1 - neurons Cx26 Vimentin - radial glia Tuj1 - neurons

18 Gap junction adhesions in radial migration 1) Gap junctions are necessary for neuronal migration. 2) Gap junction adhesions, but not channels, are necessary and sufficient to rescue the shrna induced migration defect. 3) Gap junctions can provide adhesion in cortical cells and interact with the actin cytoskeleton. 4) Gap junction adhesions act dynamically in migrating neurons to stabilize the leading processes and aid in the translocation of the nucleus. Elias and Kriegstein, Nature, 2008

19 Tangential Migration MGE migration SVZ-OB migration

20 MGE migration

21 Expression of LacZ by the Dlx5/6-Enhancer in the Embryonic Telencephalon: Shows Migration of Cells From the Subpallium (Subcortex) to the Pallium (Cortex) Text From John

22 Dlx1/2 Mutants Have A Block In Tangen9al Migra9on From The Basal Ganglia To The Cortex Anderson et al., 1997

23 MGE

24 Ultrasound Guided Transplantation Wichterle et al. Development 2001

25 A Remarkable Journey: MGE progenitors invading cortex in vivo Wichterle et al. Development 2001

26 MGE cells: source of GABAergic Cortical Interneurons Wichterle et al. Development 2001

27 Routes on Interneuron Migration from MGE into Cortex

28 Stereotyped dynamic behavior of tangentially migrating interneurons Martini, F. J. et al. Development 2009;136:41-50

29 Gad65-GFP E12.5, E13.5 Leading process branching is common to many neurons in the developing brain. (A-D) Serial sections through the brain (A,B) and spinal cord (D) of Gad65-Gfp embryos at E12.5 (D) and E13.5 (A,B). In Gad65-Gfp embryos, Gfp expression is restricted to GABAergic neurons, some of which have typical morphologies of migrating cells. The schematic drawinsg in C depict the approximate localization of sections (A,B,D). (E-H) High-magnification images of cells migrating in the developing cortex (E), thalamus (F), midbrain reticular formation (G) and ventral spinal cord (H). All these cells display similar morphologies characterized by the presence of a branched leading process (arrowheads). H, hippocampus; Dh, dorsal horn of the spinal cord; dth, dorsal thalamus; dra, dorsal raphe nucleus; FP, floor plate; GP, globus pallidus; Hyp, hippothalamus; NCx, neocortex; NLL, nucleus of the lateral lemniscus; RF, reticular formation; RP, roof plate; Rt, reticular nucleus; SC, superior colliculus; Str, striatum; LC, locus coeruleus; Vh, ventral horn of the spinal cord. Scale bars: 300 µm in A,B,D; 10 µm in E-H

30 Gfp electroporated; MGE cells migration involves bifurcated leading processes. Why? Movie 1. Migratory dynamics of a tangentially migrating interneuron. Migration of an E13.5 Gfp-electroporated interneuron migrating from the subpallium to the cortex in a slice culture. Images were acquired every 15 minutes. The total duration of the movie is 7:25 hours. The movie shows successive translocations of the nucleus along one of the branches of the leading process from one bifurcation point to the next one.

31 dsred electroporated; Cells following relatively straight paths make branches with relatively small angles. Movie 3. Branch dynamics in migrating neurons following relatively constant trajectories. Interneurons were imaged while migrating through the subpallium after 12 hours of electroporating the MGE of a E13.5 slice with

32 Gad65-GFP; Changing directions involves making new branches and necleokinesis into the angled branch. Movie 4. Branch dynamics in migrating neurons rapidly changing direction. An E16.5 Gad65-Gfp interneuron migrating through the cortical plate in a slice culture. Images were

33 Branch dynamics during tangential migration Martini, F. J. et al. Development 2009;136:41-50 Fig. 2. Branch dynamics during tangential migration. (A) A telencephalic slice from an E16.5 Gad65-Gfp embryo. GABAergic cells are observed in green in the different regions in which migration was studied: subpallium (lateral ganglionic eminence, LGE), cortical subventricular zone (SVZ) and cortical plate (CP). Owing to the massive accumulation of migrating neurons in the subpallium, analysis of neurons migrating through the LGE was performed in slice cultures in which the MGE was electroporated with Gfp or dsred (as in Fig. 1). (B-D) Representative images of the morphology of cells migrating through the LGE (B), SVZ (C) or CP (D). (B'-D')

34 Branch dynamics during Neuregulin 1 (Nrg1) induced chemotaxis Martini, F. J. et al. Development 2009;136:41-50 Fig. 3. Branch dynamics during Nrg1-induced chemotaxis. (A-A'') Images of a dsred-electroporated slice perfused with a micropipette containing recombinant EGF domain from Nrg1 (13 nm) and Alexa 488 (green channel). To induce drastic changes in direction, cortical interneurons (red channel) migrating through the LGE were confronted with the micropipette at an angle that is perpendicular to their normal trajectory. (B-B') Schematic representation of the trajectory change followed by the cell shown in C. White arrow indicates the micropipette. (C) Representative time-lapse sequences of a migrating cell that developed drastic trajectory changes in response to the chemoattractant. The cell generates a new leading process toward the pipette immediately before changing its trajectory (t=1:35). The angle generated before the most significant change in direction is the largest made by the neuron during this sequence (C). The cell chose the branch oriented towards the chemoattractant to continue migration. The gradient is also visualized in red owing to laser cross-contamination. (C'-C'') Drawings illustrate the morphology of the cell shown in C. Diagrams in C'' depict the movement of this cell. New branches are shown in green; chosen branch is tipped with a red arrowhead. The numbers indicate the angle formed by the branches.

35 Tangential Migration of Local Circuit Neurons: GABA & ACh Marin and Rubenstein, Nature Neuroscience Reviews, 2001

36 Selective Guidance of different sub-populations of MGE cells Marin et al. Science 2001

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38 GABA+ Potassium-Chloride Cotransporter (KCC2) = You Have Arrived Bortone and Polleux, 2009 Neuron

39 Telencephalic Interneurons Multiple interneuron subtypes in cortex, OB and striatum. Most contains GABA (gamma-aminobutyric acid). GABA interneurons can be further subdivided: - Ca++ binding proteins(calbindin, calretinin and parvalbumin) - neuropeptides (eg, neuropeptide Y). Not all interneurons are GABAergic: - dopamine - acetylcholine Not all GABA neurons are interneurons.

40 Tangential Migration SVZ-OB migration

41 Routes on Interneuron Migration from MGE into Cortex

42 Lois and Alvarez-Buylla PNAS Lois and Alvarez-Buylla, Science 1994

43 Chain Migration Lois, García-Verdugo and Alvarez-Buylla, Science 1996

44 The Adult Brain Contains an Extensive Network of Pathways for Chain Migration Wichterle et al. Neuron 1998

45 The Adult Brain Contains an Extensive Network of Pathways for Chain Migration cc NC SVZa M RMS Doetsch and Alvarez-Buylla PNAS. 1996

46 B SVZ Astrocyte C Amplifying Precursor A OB Interneurons B1 B2 A C E Doetsch et al, J. Neurosci Doetsch et al, Cell 1999

47 How do Cells Orient Over Such Large Territory?

48 Chemorepulsion guides SVZ neuroblasts? Wu, W., Wong, K., Chen, J., Jiang, Z., Dupuis, S., Wu, J.Y. and Rao, Y. Directional guidance of neuronal migration in the olfactory system by the protein Slit. Nature 400: , Hu, H. Chemorepulsion of neuronal migration by Slit2 in the developing mammalian forebrain. Neuron 23: , 1999.

49 Telling Direction of Migration Retrovirus encoding alkaline phosphatase (AP) Chain of neuroblasts (PSA-NCAM+) (Wichterle et al., 1997)

50 Map of Cell migration directions in the SVZ cell migration choroid plexus olfactory bulb RMS wall adhesion

51 Mapping the direction of CSF flow

52 Q: Is the CSF flow required for directional cell migration? Cell migration parallels the CSF flow cell migration cilia beating /CSF flow olfactory bulb choroid plexus site of wall adhesion RMS third ventricle

53 The Tg737orpk mice have small olfactory bulbs Volume of granule cell layer (mm3) Tg737 +/ Tg737orpk /orpk

54 The Tg737orpk mutant has defective ependymal cilia Tg737 +/+ Tg737 orpk/orpk NoelMurcia

55 The Tg737 orpk mutation disrupts normal network formation of migrating neuroblasts in SVZ Tg737 +/+ Tg737 orpk/orpk

56 slit1+/+;slit2+/+ slit1-/-;slit2-/- Slit proteins are required for repulsion of neurblasts by choroid plexus in collagen gel culture CP +/+ SVZ +/+ CP -/- SVZ +/+

57 cell migration olfactory bulb ectopic choroid plexus? choroid plexus Rostral migratory stream third ventricle

58 Ectopic CP GFP+ SVZ cells Ectopic choroid plexus inhibits migration of grafted SVZ cells into the olfactory bulb Control Choroid plexus-grafted Number of GFP+ cells in OB 5 days after transplantation (n=4) (n=5)

59 Slit proteins are partially involved in the repulsive activity of choroid plexus in vivo normal wild-type CP mutant CP

60 Slit2 protein secreted into CSF can reach SVZ and forms a concentration gradient

61 Sawamoto et al, Science 2006

62 Why Such a long Migration?

63 NSCs are: heterogeneous and restricted in potential organized in different domains NSC potential is: maintained during postnatal development determined by a cellautonomous mechanism

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