The Golgi Outpost Protein TPPP Nucleates Microtubules and Is Critical for Myelination

Cell. 2019 Sep 19;179(1):132-146.e14. doi: 10.1016/j.cell.2019.08.025. Epub 2019 Sep 12.

Abstract

Oligodendrocytes extend elaborate microtubule arbors that contact up to 50 axon segments per cell, then spiral around myelin sheaths, penetrating from outer to inner layers. However, how they establish this complex cytoarchitecture is unclear. Here, we show that oligodendrocytes contain Golgi outposts, an organelle that can function as an acentrosomal microtubule-organizing center (MTOC). We identify a specific marker for Golgi outposts-TPPP (tubulin polymerization promoting protein)-that we use to purify this organelle and characterize its proteome. In in vitro cell-free assays, recombinant TPPP nucleates microtubules. Primary oligodendrocytes from Tppp knockout (KO) mice have aberrant microtubule branching, mixed microtubule polarity, and shorter myelin sheaths when cultured on 3-dimensional (3D) microfibers. Tppp KO mice exhibit hypomyelination with shorter, thinner myelin sheaths and motor coordination deficits. Together, our data demonstrate that microtubule nucleation outside the cell body at Golgi outposts by TPPP is critical for elongation of the myelin sheath.

Keywords: Golgi outpost; TPPP; branching; mass spectrometry; microtubule; myelin; nucleation; oligodendrocyte.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Animals, Newborn
  • Axons / metabolism
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell-Free System / metabolism
  • Cells, Cultured
  • Escherichia coli / metabolism
  • Gene Knockdown Techniques
  • Golgi Apparatus / metabolism*
  • Humans
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Microtubule-Organizing Center / metabolism
  • Microtubules / metabolism*
  • Myelin Sheath / metabolism*
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism*
  • Oligodendrocyte Precursor Cells / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Tubulin / metabolism

Substances

  • Carrier Proteins
  • Nerve Tissue Proteins
  • TPPP protein, human
  • TPPP protein, mouse
  • TPPP protein, rat
  • Tubulin