The vesicular acetylcholine transporter is required for neuromuscular development and function.
The vesicular acetylcholine (ACh) transporter (VAChT) mediates ACh storage by synaptic vesicles. However, the VAChT-independent release of ACh is believed to be important during development. Here we generated VAChT knockout mice and tested the physiological relevance of the VAChT-independent release of ACh. Homozygous VAChT knockout mice died shortly after birth, indicating that VAChT-mediated storage of ACh is essential for life. Indeed, synaptosomes obtained from brains of homozygous knockouts were incapable of releasing ACh in response to depolarization. Surprisingly, electrophysiological recordings at the skeletal-neuromuscular junction show that VAChT knockout mice present spontaneous miniature end-plate potentials with reduced amplitude and frequency, which are likely the result of a passive transport of ACh into synaptic vesicles. Interestingly, VAChT knockouts exhibit substantial increases in amounts of choline acetyltransferase, high-affinity choline transporter, and ACh. However, the development of the neuromuscular junction in these mice is severely affected. Mutant VAChT mice show increases in motoneuron and nerve terminal numbers. End plates are large, nerves exhibit abnormal sprouting, and muscle is necrotic. The abnormalities are similar to those of mice that cannot synthesize ACh due to a lack of choline acetyltransferase. Our results indicate that VAChT is essential to the normal development of motor neurons and the release of ACh.
de Castro
Braulio M
BM
Molecular Brain Research Group, Robarts Research Institute, University of Western Ontario, P.O. Box 5015, 100 Perth Drive, London, Ontario N6A 5K8, Canada.
De Jaeger
Xavier
X
Martins-Silva
Cristina
C
Lima
Ricardo D F
RD
Amaral
Ernani
E
Menezes
Cristiane
C
Lima
Patricia
P
Neves
Cintia M L
CM
Pires
Rita G
RG
Gould
Thomas W
TW
Welch
Ian
I
Kushmerick
Christopher
C
Guatimosim
Cristina
C
Izquierdo
Ivan
I
Cammarota
Martin
M
Rylett
R Jane
RJ
Gomez
Marcus V
MV
Caron
Marc G
MG
Oppenheim
Ronald W
RW
Prado
Marco A M
MA
Prado
Vania F
VF
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004622:Embryo, Mammalian / Q000196:embryology / Q000378:metabolism; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009046:Motor Neurons / Q000378:metabolism*; D024510:Muscle Development; D018482:Muscle, Skeletal / Q000196:embryology / Q000378:metabolism*; D009469:Neuromuscular Junction / Q000196:embryology / Q000254:growth & development* / Q000378:metabolism*; D013572:Synaptic Vesicles / Q000378:metabolism; D050494:Vesicular Acetylcholine Transport Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
D050494:Vesicular Acetylcholine Transport Proteins; D000109:Acetylcholine