Transcript Muscle Spindle Development

Muscle Spindles in Literature
Papers with the MeSH term “Muscle Spindle” in the last 50 years.
Morphology (TEM)
Outer Capsule 
Intrafusal Fibers
Primary Ending 
Peri-axial Space
 Inner Capsule
Scale bar 5μm
Journal of Electron Microscopy 50(1): 65-72 (2001)
Central Pathway
Somatosensory Cortex
VPL Nucleus of Thalamus
Medial Lemniscus
Cuneate/Gracile Nucleus
Cuneate/Gracile Fascicle
Dorsal Root Ganglion
Mouse Embryonic Days
E13.5
E14.5
E15.5
E16.5
E18.5
http://www.mouseatlas.org/data/mouse/devstages
Neurotrophin Background
The Nobel Prize in
Physiology or Medicine 1986
Dr. Victor Hamburger’s Lab
Dr. Levi-Montalcini came from neurology – Transplanted mouse tumors to chick embryos
 outgrowth of certain nerve fibers.
Dr. Stanley Cohen was from biochemistry – Observed that the glands of mice contain
even more NGF.
trkC Regulation
Neurogenin-2
(Basic Helix Loop Helix)
Brn3a turns on Runx3, Runx3 binds to a promoter
region upstream of trkC, regulating its expression.
?
D. Levanon, D. Bettoun, C. Harris-Cerruti, E. Woolf, V.
Negreanu, R. Eilam, Y. Bernstein, D. Goldenberg, C. Xiao, M.
Fliegauf. EMBO J. 21 (2002), pp. 3454–3463.
Brn3a
Runx3
trkC
Muscle Spindle Development 1
Chen HH, Hippenmeyer S, Arber S, Frank E. Development of the monosynaptic
stretch reflex circuit. Curr Opin Neurobiol. 2003 Feb;13(1):96-102.
Muscle Spindle Development 2
Chen HH, Frank E. Development and specification of muscle
sensory neurons. Curr Opin Neurobiol. 1999 Aug;9(4):405-9.
S. Hippenmeyer, N.A. Shneider, C. Birchmeier, S. Burden, T.M. Jessell and S. Arber, A role
for Neuregulin I signaling in muscle spindle differentiation. Neuron 36 (2002), pp. 1035–1049.
Knockout Experiments
trkC Knockout
Liebl DJ, Tessarollo L, Palko ME, and Parada LF (1997) Absence of sensory neurons prior to
target innervation in BDNF, NT-3 & TrkC deficient embryonic mice. J Neurosci 17:9113-9121.
NT-3 Knockout
Wright DE, Zhou L, Kucera J, Snider WD. Intro of a NT-3 transgene into muscle selectively
rescues proprioceptive neurons in mice lacking end. NT-3. Neuron 1997 Sep;19(3): 503-17.
Nrg-1 Knockout
S. Hippenmeyer, N.A. Shneider, C. Birchmeier, S. Burden, T.M. Jessell and S. Arber, A role for
Neuregulin I signaling in muscle spindle differentiation. Neuron 36 (2002), pp. 1035–1049.
erbB2 Knockout
Leu M, Bellmunt E, Schwander M, Farinas I, Brenner HR, Muller U. Erbb2 regulates neuromuscular synapse formation and is essential for muscle spindle development. Dev 2003 Jun;
130(11) :2291-301.
EGR3 Knockout
Chen HH, Tourtellotte WG, Frank E. Muscle Spindle-Derived NT-3 Regulates Synaptic Connectivity between Muscle Sensory and Motor Neurons. J. Neuro, May 2002, 22(9): 3512-3519
ERM Knockout
ER81 Knockout
Arber S, Ladle DR, Lin JH, Frank E, Jessell TM. ETS gene Er81 controls the formation of
functional connections between group Ia sensory afferents and MN. Cell. 2000 101 (5): 485-98.
PEA3 Knockout
Ladle DR, Frank E. The role of the ETS gene PEA3 in the development of motor and sensory
neurons. Physiol Behav. 2002 Dec;77(4-5):571-6.
Prior Development Experiments
-Proprioceptors require TrkC and NT3, cutaneous require TrkA and NGF (Klein 1994) – Experiment looked
at trkC deficient mouse. No Ia afferents and movement defects
-NT3 is expressed by mesenchyme surrounding the DRG, motoneurons, developing embryonic muscles
(this is likely the only source that matters)
-It appears that NT3 does more than just keep the nerve alive, but also acts to attract the growing axon to
the muscle in-vivo (Tucker 2001), and in-vitro (Ming 1997)
-TFs expressed selectively by intrafusal muscle fibers even at early developmental stages
oZinc-finger TF  Egr3
oEts TFs  Pea3 and Erm
oThe expression of these TFs is usually controlled by Nrg1/ErbB
-Nrg1 (Ig Isoform) expressed by TrkC neurons (Hippenmeyer 2002)
-ErbB2 is expressed by intrafusal muscle fibers and the connective tissue surrounding MSpindles
(Andrechek 2002)
-Even in ErbB2 knockouts, or Nrg1 knockouts – afferents still contact individual myotubes (Hippenmeyer
2002)
Support - Primary Ending Function
Quick DC.
Acute lesion of the intrafusal muscle of muscle spindles: ultrastructural and
electrophysiological consequences. J Neurosci. 1986 Jul;6(7):2097-105.
• Experiments were performed to functionally separate the neural and muscular
elements in muscle spindles.
• Cat muscle spindles were dissected free in vitro and were transected on both
sides of the sensory nerve endings  acute lesion of the intrafusal muscle
fibers, spared sensory endings.
• Within 45 min, the intrafusal muscle fibers degenerated to the condition in
which there were no myofilaments left in the sensory zone and the muscle fiber
membrane had begun to disintegrate.
• During this degeneration period, and afterward, the sensory nerve fibers
continued to fire action potentials.
• Overall, the results indicate that the nerve endings have an intrinsic
capability to function as sensory receptors in the absence of a muscle
substrate.
Trk Signaling 1
Trk Signaling 2
Full Text CONB – Trk Receptors
Adapter proteins are colored orange, kinases pink, small G proteins green, and transcription factors blue. APS, adaptor molecule
containing PH and SH2 domains; CHK, Csk homologue kinase; MEK, MAPK/ERK; P, serine/threonine (filled, phosphorylated); SNT,
suc-1-associated neurotrophic factor target.
Trk Signaling 3
Full Text
Muscle Development
http://www.ens-lyon.fr/LBMC/schaeffer/pres-uk.htm
Neuromuscular Junction
• erbB2 and erbB4 are enriched in the depths of the secondary junctional folds on
the postsynaptic muscle membrane.
• erbB3 at the NMJ was concentrated at presynaptic terminal Schwann cells.
• Neuregulin was localized to the axon terminal, secondary folds, and terminal
Schwann cells, where it was in a position to signal through erbB receptors.
• MuSK was concentrated in the postsynaptic primary gutter region where it was
codistributed with AChRs.
• Agrin was present at the axon terminal and in the basal lamina associated with
the primary gutter region, but not in the secondary junctional folds.
• The differential distributions of the neuregulin and agrin signaling pathways argue
against neuregulin and erbB receptors being localized to the NMJ via direct
interactions with either agrin or MuSK.
http://www.jneurosci.org/cgi/content/full/20/23/8762
Is NT3 sufficient for a muscle spindle afferent to elaborate its endings?
Aim 1 – Rationale (More)
Scale bar, 10 µm
Ming G Lohof AM Zheng JQ. Acute morphogenic and chemotropic effects of neurotrophins
on cultured embryonic Xenopus spinal neurons. J. Neurosci. 17, 7860-7871 (1997)
http://www.jneurosci.org/cgi/content/full/17/20/7860
Is NT3 sufficient for a muscle spindle afferent to elaborate its endings?
Aim 1 - Rationale
E13.5 DRG Axons – Same day in culture grow towards NT-3 beads.
100 μm
350 μm
150 μm
NT3 beads: 10–100 μg/ml
Genc B, Ozdinler PH, Mendoza AE, Erzurumlu RS. NeurotrophinChemoattractant
Aim 1 – Rationale (More)
Hours :
100 μm
Mouse DRG and Spinal Cord E10
• Beads soaked in 10 ug/ml BDNF
• Hours after beads were applied
• White arrow points to center of
bead
Nerve grew toward a bead (30° away) :
De novo growth toward a bead :
Nerve contacted the nerve and stopped :
Nerve which contacted encircled bead :
(n = 111)
ug/ml
100
10
1
83%
17%
92%
25%
NT3
4/6
37/43
3/3
Nature Neuroscience 4, 29 - 37 (2001)
Aim 1 Method – Cell Line Options
Human Embryonic Kidney
Chinese Hamster
Ovary
CHO
HEK
•A non-muscle cell to test the connections of proprioceptive afferents.
•This cell would be stably transfected with murine NT3
•Expression monitored using staining and fixation, or ELISA.
•The cell types above are relatively stable and easy to passage.
Aim 1 Method – DRG Preparation
• These mice are euthanatized and approximately 10 of their DRGs are removed
under a microscope.
• The DRGs are dissociated with an enzyme cocktail which includes Trypsin,
Elastase, DNase, and Collagenase.
• Dissociated DRGs are then plated at ~100 cells/mm2 in multi-well plates with
coverglass on the floor.
• The cover glasses should be pre-coated with poly-D-lysine and laminin.
• The culture should occur in the presence of serum-free media but with the
addition of NGF and NT3 for the first day.
• On subsequent days, the media should have only NT3 to select for trkC+
neurons.
• At all times after plating, the neurons should be kept in 37°C incubators at 5%
CO2.
Aim 1 Method – Stable Cell Lines
•Prepare an expression vector with neomycin resistance.
•Transfect cells and kill non-transfected cells by adding neomycin to the culture
medium.
•Plate the transfected cells onto a 96 well plate, with approximately 3 cells per well.
•Mark wells that have just a single cell in them, these wells represent a monoclonal
colony. Allow these cells to divide for several weeks.
•Check the expression level of the cells, and pick the best expressing clones.
•This could be done either by staining the cells with a marker for the protein, or by
doing an ELISA, or by co-expressing GFP.
•The best expressing clones can be grown up and be used to express NT3
constitutively at a known level of expression.
Aim 3 Methods - Setup
- On Cell Recording
- Giga Ohm Seal
- Record from Cell Body
- Control to depolarize cells using
High KCL Ringer Solution
Aim 3 Methods - Ion Distribution
What Concentration of KCL will depolarize the cell?  140 mM should do the trick.
Ca+ = 2mM
Na+
= 145mM
Cl- = 110mM
K+ = 5mM
Na+
K+ = 140mM
= 10mM
Cl- = 30mM
Ca+ = 1μM