Nuclei in the synaptic region of multinucleated skeletal myofibers are transcriptionally distinct, since acetylcholine receptor genes are transcribed at a high rate by these nuclei, but not by nuclei elsewhere in the myofiber. Although this spatially restricted transcription pattern is presumably imposed by the motor nerve, the continuous presence of the nerve is not required, since synapse-specific transcription persists after denervation. These results suggest either that a transcriptional signal persists at synaptic sites after nerve terminals have degenerated, or that a transcriptional pattern in the myofiber, once established, is stable in the absence of a nerve-derived signal. To distinguish between these possibilities, we denervated muscle and damaged the myofibers and specialized cells located near synaptic sites, and then studied transcription of an acetylcholine receptor gene in myofibers that regenerated in their original basal lamina sheaths, but remained denervated. We show that synapse-specific transcription is re-induced in these regenerated myofibers, and we conclude that a signal for synapse-specific transcription is stably maintained in the synaptic basal lamina.

REFERENCES

Bader
D.
(
1981
)
Density and distribution of-bungarotoxin binding sites in postsynaptic structures of regenerated rat skeletal muscle.
J. Cell Biol
88
,
338
345
Birks
R.
,
Katz
B.
,
Miledi
R.
(
1960
)
Physiological and structural changes at the amphibian myoneural junction, in the course of nerve degeneration.
J. Physiol. (Lond.)
150
,
145
168
Brenner
H.-R.
,
Witzemann
V.
,
Sakmann
B.
(
1990
)
Imprinting of acetylcholine receptor messenger RNA accumulation in mammalian neuromuscular synapses.
Nature
344
,
544
547
Burden
S. J.
,
Sargent
P. B.
,
McMahan
U. J.
(
1979
)
Acetylcholine receptors in regenerating muscle accumulate at original synaptic sites in the absence of the nerve.
J. Cell Biol
82
,
412
425
Campanelli
J. T.
,
Hoch
W.
,
Rupp
F.
,
Kreiner
T.
,
Scheller
R. H.
(
1991
)
Agrin mediates cell contact-induced acetylcholine receptor clustering.
Cell
67
,
909
916
Chapron
J.
,
Koenig
J.
(
1989
)
In vitro synaptic maturation.
Neurosci. Lett
106
,
19
22
Connor
E. A.
,
McMahan
U. J.
(
1987
)
Cell accumulation in the junctional region of denervated muscle.
J. Cell Biol
104
,
109
120
Fambrough
D. M.
(
1979
)
Control of acetylcholine receptors in skeletal muscle.
Physiol. Rev
59
,
165
226
Fontaine
B.
,
Changeux
J. P.
(
1989
)
Localization of nicotinic acetylcholine receptor a-subunit transcripts during myogenesis and motor endplate development in the chick.
J. Cell Biol
108
,
1025
1037
Gatchalian
C. L.
,
Schachner
M.
,
Sanes
J. R.
(
1989
)
Fibroblasts that proliferate near denervated synaptic sites in skeletal muscle synthesize the adhesive molecules tenascin (J1), N-CAM, fibronectin, and a heparan sulfate proteglycan.
J. Cell Biol
108
,
1873
1890
Godfrey
E. W.
,
Nitkin
R. M.
,
Wallace
B. G.
,
Rubin
L. L.
,
McMahan
U. J.
(
1984
)
Components of Torpedo electric organ and muscle that cause aggregation of acetylcholine receptors on culture muscle cells.
J. Cell Biol
99
,
615
627
Goldman
D.
,
Staple
J.
(
1989
)
Spatial and temporal expression of acetylcholine receptor mRNAs in innervated and denervated rat soleus muscle.
Neuron
3
,
219
228
Goldman
D.
,
Carlson
B. M.
,
Staple
J.
(
1991
)
Induction of adult-type nicotinic acetylcholine receptor gene expression in noninnervated regenerating muscle.
Neuron
7
,
649
658
Hunter
D. D.
,
Shah
V.
,
Merlie
J. P.
,
Sanes
J. R.
(
1989
)
A laminin-like adhesive protein concentrated in the synaptic cleft of the neuromuscular junction.
Nature
338
,
229
234
Karnovsky
M. J.
(
1964
)
The localization of cholinesterase activity in rat cardiac muscle by electron microscopy.
J. Cell Biol
23
,
217
232
Klarsfeld
A.
,
Bessereau
J.-L.
,
Salmon
A.-M.
,
Triller
A.
,
Babinet
C.
,
Changeux
J.-P.
(
1991
)
An acetylcholine receptor a-subunit promoter conferring preferential synaptic expression in muscle of transgenic mice.
EMBO J
10
,
625
632
Ko
P. K.
,
Anderson
M. J.
,
Cohen
M. W.
(
1977
)
Denervated skeletal muscle fibers develop discrete patches of high acetylcholine receptor density.
Science
196
,
540
542
Magill-Solc
C.
,
McMahan
U. J.
(
1988
)
Motor neurons contain agrin-like molecules.
J. Cell Biol
107
,
1825
1833
Marshall
L. M.
,
Sanes
J. R.
,
McMahan
U. J.
(
1977
)
Reinnervation of original synaptic sites on muscle fiber basement membrane after disrpution of muscle cells.
Proc. Natl. Acad. Sci. USA
74
,
3073
3077
McMahan
U. J.
,
Sanes
J. R.
,
Marshall
L. M.
(
1978
)
Cholinesterase is associated with the basal lamina at the neuromuscular junction.
Nature
271
,
172
174
McMahan
U. J.
,
Slater
C. R.
(
1984
)
The influence of basal lamina on the accumulation of acetylcholine receptors at synaptic sites in regenerating muscles.
J. Cell Biol
98
,
1453
1473
Merlie
J. P.
,
Sanes
J. R.
(
1985
)
Concentration of acetylcholine receptor mRNA in synaptic regions of adult muscle fibers.
Nature
317
,
66
68
Nitkin
R. M.
,
Smith
M. A.
,
Magill
C.
,
Fallon
J. R.
,
Yao
Y. M.
,
Wallace
B. G.
,
McMahan
U. J.
(
1987
)
Identification of agrin, a synaptic organizing protein from Torpedo electric organ.
J. Cell Biol
105
,
2471
2478
Reist
N. E.
,
Magill
C.
,
McMahan
U. J.
(
1987
)
Agrin-like molecules at synaptic sites in normal, denervated, and damaged skeletal muscles.
J. Cell Biol
105
,
2457
2469
Rich
M.
,
Lichtman
J. W.
(
1989
)
Motor nerve terminal loss from degenerating muscle fibers.
Neuron
3
,
677
688
Sanes
J. R.
(
1983
)
Roles of extracellular matrix in neural development.
Ann. Rev. Physiol
45
,
581
600
Sanes
J. R.
,
Engvall
E.
,
Butkowski
R.
,
Hunter
D. D.
(
1990
)
Molecular heterogeneity of basal laminae: isoforms of laminin and collagen IV at the neuromuscular junction and elsewhere.
J. Cell Biol
111
,
1685
1699
Sanes
J. R.
,
Johnson
Y. R.
,
Kotzbauer
P. T.
,
Mudd
J.
,
Hanley
T.
,
Martinou
J. C.
,
Merlie
J. P.
(
1991
)
Selective expression of an acetylcholine receptor-lacZ transgene in synaptic nuclei of adult muscle fibers.
Development
113
,
1181
1191
Sanes
J. R.
,
Marshall
L. M.
,
McMahan
U. J.
(
1978
)
Reinnervation of muscle fiber basal lamina after removal of myofibers.
Differentiation of regenerating axons at original synaptic sites. J. Cell Biol
78
,
176
198
Simon
A. M.
,
Hoppe
P.
,
Burden
S. J.
(
1992
)
Spatial restriction of AChR gene expression to subsynaptic nuclei.
Development
114
,
545
553
Swenarchuk
L. E.
,
Champaneria
S.
,
Anderson
M. J.
(
1990
)
Induction of a specialized muscle basal lamina at chimaeric synapses in culture.
Development
110
,
51
61
Vracko
R.
(
1974
)
Basal lamina scaffold: anatomy and significance for maintenance of orderly tissue structure.
Am. J. Pathol
77
,
314
338
Weis
J.
,
Fine
S. M.
,
David
C.
,
Savarirayan
S.
,
Sanes
J. R.
(
1991
)
Integration site-dependent expression of a transgene reveals specialized features of cells associated with neuromuscular junctions.
J. Cell Biol
113
,
1385
1397
Witzemann
V.
,
Barg
B.
,
Criado
M.
,
Stein
E.
,
Sakmann
B.
(
1989
)
Developmental regulation of five subunit specific mRNAs encoding acetylcholine receptor subtypes in rat muscle.
FEBS Lett
242
,
419
424
Witzemann
V.
,
Brenner
H.-R.
,
Sakmann
B.
(
1991
)
Neural factors regulate AChR subunit mRNAs at rat neuromuscular synapses.
J. Cell Biol
114
,
125
141
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