Mutations in the murine homologue of TUBB5 cause microcephaly by perturbing cell cycle progression and inducing p53-associated apoptosis

Development. 2016 Apr 1;143(7):1126-33. doi: 10.1242/dev.131516. Epub 2016 Feb 22.


Microtubules play a crucial role in the generation, migration and differentiation of nascent neurons in the developing vertebrate brain. Mutations in the constituents of microtubules, the tubulins, are known to cause an array of neurological disorders, including lissencephaly, polymicrogyria and microcephaly. In this study we explore the genetic and cellular mechanisms that cause TUBB5-associated microcephaly by exploiting two new mouse models: a conditional E401K knock-in, and a conditional knockout animal. These mice present with profound microcephaly due to a loss of upper-layer neurons that correlates with massive apoptosis and upregulation of p53. This phenotype is associated with a delay in cell cycle progression and ectopic DNA elements in progenitors, which is dependent on the dosage of functional Tubb5. Strikingly, we report ectopic Sox2-positive progenitors and defects in spindle orientation in our knock-in mouse line, which are absent in knockout animals. This work sheds light on the functional repertoire of Tubb5, reveals that the E401K mutation acts by a complex mechanism, and demonstrates that the cellular pathology driving TUBB5-associated microcephaly is cell death.

Keywords: Apoptosis; Microcephaly; Trp53; Tubulin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / genetics*
  • Brain / abnormalities
  • Brain / embryology
  • Cell Cycle / genetics*
  • Cell Differentiation
  • Disease Models, Animal
  • Embryo, Mammalian / embryology
  • Gene Knock-In Techniques
  • Magnetic Resonance Imaging
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Microcephaly / genetics*
  • Microtubules / genetics*
  • Microtubules / metabolism
  • Neural Stem Cells / cytology
  • SOXB1 Transcription Factors / metabolism
  • Spindle Apparatus / genetics
  • Stem Cells / cytology
  • Tubulin / genetics*
  • Tumor Suppressor Protein p53 / biosynthesis
  • Tumor Suppressor Protein p53 / metabolism*


  • SOXB1 Transcription Factors
  • Sox2 protein, mouse
  • TUBB5 protein, mouse
  • Tubulin
  • Tumor Suppressor Protein p53