title: In vivo imaging of cell behaviors and F-actin reveals LIM-HD transcription factor regulation of peripheral versus central sensory axon development.
abstract: BACKGROUND
  Development of specific neuronal morphology requires precise control over cell motility processes, including axon formation, outgrowth and branching. Dynamic remodeling of the filamentous actin (F-actin) cytoskeleton is critical for these processes; however, little is known about the mechanisms controlling motile axon behaviors and F-actin dynamics in vivo. Neuronal structure is specified in part by intrinsic transcription factor activity, yet the molecular and cellular steps between transcription and axon behavior are not well understood. Zebrafish Rohon-Beard (RB) sensory neurons have a unique morphology, with central axons that extend in the spinal cord and a peripheral axon that innervates the skin. LIM homeodomain (LIM-HD) transcription factor activity is required for formation of peripheral RB axons. To understand how neuronal morphogenesis is controlled in vivo and how LIM-HD transcription factor activity differentially regulates peripheral versus central axons, we used live imaging of axon behavior and F-actin distribution in vivo.
  
  
  RESULTS
  We used an F-actin biosensor containing the actin-binding domain of utrophin to characterize actin rearrangements during specific developmental processes in vivo, including axon initiation, consolidation and branching. We found that peripheral axons initiate from a specific cellular compartment and that F-actin accumulation and protrusive activity precede peripheral axon initiation. Moreover, disruption of LIM-HD transcriptional activity has different effects on the motility of peripheral versus central axons; it inhibits peripheral axon initiation, growth and branching, while increasing the growth rate of central axons. Our imaging revealed that LIM-HD transcription factor activity is not required for F-actin based protrusive activity or F-actin accumulation during peripheral axon initiation, but can affect positioning of F-actin accumulation and axon formation.
  
  
  CONCLUSIONS
  Our ability to image the dynamics of F-actin distribution during neuronal morphogenesis in vivo is unprecedented, and our experiments provide insight into the regulation of cell motility as neurons develop in the intact embryo. We identify specific motile cell behaviors affected by LIM-HD transcription factor activity and reveal how transcription factors differentially control the formation and growth of two axons from the same neuron.
authors: Genetics Training Program, University of Wisconsin, 1117 W, Johnson Street, Madison, WI 53706, USA.
authors: Erica F
authors: EF
authors: Andersen
authors: Namrata S
authors: NS
authors: Asuri
authors: Mary C
authors: MC
authors: Halloran
references: Nat Cell Biol. 2007 Dec;9(12):1347-59
references: 18026093
references: Cold Spring Harb Perspect Biol. 2010 Apr;2(4):a001925
references: 20452947
references: Neuron. 2001 May;30(2):423-36
references: 11395004
references: Gene Expr Patterns. 2002 Nov;2(1-2):137-43
references: 12617852
references: Nat Neurosci. 2001 Nov;4(11):1093-101
references: 11593233
references: J Neurosci. 1996 Jul 15;16(14):4389-401
references: 8699250
references: Mol Biol Cell. 2008 Apr;19(4):1485-98
references: 18234839
references: J Vis Exp. 2010 Feb 03;(36):
references: 20130524
references: Development. 2011 Jan;138(2):183-95
references: 21177340
references: J Neurosci. 2004 Mar 24;24(12):3002-12
references: 15044539
references: PLoS Biol. 2005 Aug;3(8):e272
references: 16026180
references: Nat Rev Mol Cell Biol. 2009 May;10(5):332-43
references: 19373241
references: Cell. 2003 Jul 25;114(2):229-39
references: 12887924
references: Mech Dev. 2003 Feb;120(2):211-8
references: 12559493
references: Proc Natl Acad Sci U S A. 2009 Sep 29;106(39):16847-52
references: 19805384
references: Neuroscientist. 2003 Oct;9(5):343-53
references: 14580119
references: J Cell Biol. 1994 Dec;127(6 Pt 1):1693-701
references: 7798321
references: J Cell Biol. 1989 May;108(5):1737-49
references: 2654140
references: Curr Opin Neurobiol. 2008 Feb;18(1):36-43
references: 18524570
references: Methods Cell Biol. 2004;77:201-22
references: 15602913
references: Cold Spring Harb Perspect Biol. 2011 Mar 01;3(3):
references: 21106647
references: Nat Rev Neurosci. 2002 Sep;3(9):694-704
references: 12209118
references: Development. 2008 May;135(10):1833-41
references: 18417618
references: J Neurosci. 2003 Oct 22;23(29):9479-90
references: 14573527
references: Bioessays. 2010 Nov;32(11):977-85
references: 20827677
references: J Neurobiol. 2006 Jul;66(8):847-67
references: 16673385
references: Dev Neurobiol. 2011 Mar;71(3):201-20
references: 21308993
references: Dev Biol. 2008 Dec 15;324(2):236-44
references: 18926812
references: J Neurosci. 1994 Oct;14(10):5872-84
references: 7931550
references: Neuron. 2003 May 22;38(4):581-96
references: 12765610
references: Development. 2004 Aug;131(15):3705-15
references: 15229183
references: Dev Dyn. 2006 Jan;235(1):213-24
references: 16261616
references: Cold Spring Harb Perspect Biol. 2009 Sep;1(3):a001644
references: 20066106
references: J Neurosci. 2010 Sep 8;30(36):12185-97
references: 20826681
references: J Neurosci. 2005 Nov 9;25(45):10556-63
references: 16280593
references: Nat Rev Neurosci. 2007 Mar;8(3):194-205
references: 17311006
references: Cell. 2003 Sep 5;114(5):545-57
references: 13678579
references: Dev Dyn. 2007 Nov;236(11):3088-99
references: 17937395
references: J Neurosci. 2001 Dec 15;21(24):9782-91
references: 11739586
references: Nature. 1999 Sep 2;401(6748):69-73
references: 10485706
references: J Physiol. 1984 Mar;348:511-25
references: 6201612
references: Curr Biol. 2009 Aug 25;19(16):1389-95
references: 19631537
references: Trends Neurosci. 2000 Nov;23(11):557-65
references: 11074265
references: Annu Rev Cell Dev Biol. 2002;18:601-35
references: 12142283
references: J Comp Neurol. 1990 Dec 15;302(3):603-16
references: 1702120
references: Dev Dyn. 1995 Jul;203(3):253-310
references: 8589427
references: Neural Dev. 2008 Feb 20;3:6
references: 18289389
references: Dev Cell. 2010 Feb 16;18(2):226-36
references: 20159593
references: J Neurobiol. 2005 Jan;62(1):134-47
references: 15452851
references: Cell. 2005 Nov 4;123(3):477-91
references: 16269338
references: Mech Dev. 2002 Sep;117(1-2):75-85
references: 12204249
references: Dev Biol. 2000 May 15;221(2):308-20
references: 10790328
references: J Neurosci. 1996 Feb 15;16(4):1450-9
references: 8778296
references: Development. 1987 Sep;101(1):123-33
references: 3449363
references: Trends Cell Biol. 2008 Dec;18(12):597-603
references: 18951796
references: Cell. 2004 Nov 12;119(4):567-78
references: 15537545
references: J Neurosci. 2001 Dec 15;21(24):9757-69
references: 11739584
references: Cell. 2000 Jul 21;102(2):161-73
references: 10943837
references: EMBO J. 2009 Feb 4;28(3):248-60
references: 19096364
references: Neuron. 1988 Dec;1(10):901-10
references: 3272157
references: Dev Dyn. 2007 Nov;236(11):3077-87
references: 17948311
references: Dev Dyn. 2011 Jan;240(1):9-22
references: 21108318
references: Curr Biol. 2005 May 10;15(9):804-14
references: 15886097
references: Nat Cell Biol. 2009 Jan;11(1):71-7
references: 19060892
references: J Comp Neurol. 1990 Dec 15;302(3):617-28
references: 2262604
references: Development. 1996 Sep;122(9):2611-21
references: 8787736
references: Neuron. 2003 Oct 9;40(2):209-27
references: 14556705
references: Cell Motil Cytoskeleton. 2007 Nov;64(11):822-32
references: 17685442
references: Nat Neurosci. 2006 Apr;9(4):511-8
references: 16520734
references: J Neurosci. 2008 Jun 4;28(23):5910-9
references: 18524895
references: J Neurosci. 1998 Oct 1;18(19):7930-40
references: 9742160
references: Mol Biol Cell. 2008 Apr;19(4):1561-74
references: 18256280
references: J Neurosci. 1999 May 15;19(10):3860-73
references: 10234018
references: J Neurosci. 2006 Mar 29;26(13):3604-14
references: 16571769
references: Nat Neurosci. 2006 Oct;9(10):1274-83
references: 16964253
references: Proc Natl Acad Sci U S A. 2009 Oct 20;106(42):18016-21
references: 19805191
references: Dev Neurobiol. 2010 Jul;70(8):565-88
references: 20506164
references: Nat Rev Neurosci. 2007 May;8(5):331-40
references: 17453014