PURKINJE CELL DENDRITES OF DILUTE-LETHAL MICE (MYOSIN VA NULL) ARE ABNORMAL IN F-ACTIN CONTENT.

CAPANI, F. ; ELLISMAN, M. ; MARTONE, M. ; BRIDGMAN, P. C

Congreso; Society for Neuroscience Meeting; 2001

Purkinje cell dendritic spines in dilute-lethalmice lack smooth endoplasmic reticulum. This abnormality contributes to the disruption of Purkinje cell LTD. Because myosin Va is absent from these mice, the entry and anchoring of smooth ER in the spine was thought to be directly dependent upon myosin Va motor activity. However, we now find that spines of dilute-lethalmice are also deficient in F-actin using a novel method based on the high binding affinity of phalloidin for the F-actin followed by photooxidation of diaminobenzidine by eosin. Phalloidin staining imaged by confocal or two-photon microscopy was reduced in intensity in dilute-lethalPurkinje cell spines compared to those from normal littermates. Similarly, photoconverted phalloidin staining produced greatly reduced amounts of electron dense reaction products in dilute-lethalspines. Thus, myosin Va may also modulate the polymerization state of spine actin. Reduced amounts of F-actin may contribute to decreased entry or anchoring of smooth ER in spines. Actin abnormalities in Purkinje cell spines may also contribute to other long-term changes in spine function.