Lavender, A Chick Melanocyte Mutant with Defective Melanosome Translocation: A Possible Role for 10 nm Filaments and Microfilaments but not Microtubules

Authors

Paula Mayerson, University of Nebraska - Lincoln
John Brumbaugh, University of Nebraska - Lincoln

Date of this Version

1981

Comments

Published in J. Cell Sci. 51, 25-51 (1981). Printed in Great Britain © Company of Biologist Limited 1981. Used by permission.

Abstract

Lavender is a mutation of chick neural-crest-derived melanocytes showing dilute feather pigmentation. This defect, previously attributed to a lack or attenuation of dendrites, was found to be due to a defect in melanosome translocation. The mutant phenotype, of melanincongested perikarya and pigmentless dendrites is expressed both in vivo and in vitro. Studies with colcemid and cytochalasin B suggest that the avian melanocyte resembles a dispersing amphibian melanophore in its requirement for microfilaments but not microtubules.
Ultrastructural analysis revealed a normal complement of intracellular filaments. Microtubules, however, are scarce. Intermediate (10 nm) filaments surround and are closely associated with intracellular organelles, while microfilaments interconnect all filaments and organelles. Whole-cell centrifugation at 300 g showed that 10 nm filaments stream behind and appear to attach to mobile membrane-bound organelles including the nucleus, lipid granules and mitochondria, as well as melanosomes. It is suggested that all intracellular filaments, especially microfilaments and intermediate filaments, interconnect forming a network responsible for organelle motility.