Defective craniofacial development and brain function in a mouse model for depletion of intracellular inositol synthesis

J Biol Chem. 2014 Apr 11;289(15):10785-96. doi: 10.1074/jbc.M113.536706. Epub 2014 Feb 19.

Abstract

myo-Inositol is an essential biomolecule that is synthesized by myo-inositol monophosphatase (IMPase) from inositol monophosphate species. The enzymatic activity of IMPase is inhibited by lithium, a drug used for the treatment of mood swings seen in bipolar disorder. Therefore, myo-inositol is thought to have an important role in the mechanism of bipolar disorder, although the details remain elusive. We screened an ethyl nitrosourea mutant mouse library for IMPase gene (Impa) mutations and identified an Impa1 T95K missense mutation. The mutant protein possessed undetectable enzymatic activity. Homozygotes died perinatally, and E18.5 embryos exhibited striking developmental defects, including hypoplasia of the mandible and asymmetric fusion of ribs to the sternum. Perinatal lethality and morphological defects in homozygotes were rescued by dietary myo-inositol. Rescued homozygotes raised on normal drinking water after weaning exhibited a hyper-locomotive trait and prolonged circadian periods, as reported in rodents treated with lithium. Our mice should be advantageous, compared with those generated by the conventional gene knock-out strategy, because they carry minimal genomic damage, e.g. a point mutation. In conclusion, our results reveal critical roles for intracellular myo-inositol synthesis in craniofacial development and the maintenance of proper brain function. Furthermore, this mouse model for cellular inositol depletion could be beneficial for understanding the molecular mechanisms underlying the clinical effect of lithium and myo-inositol-mediated skeletal development.

Keywords: Bone; Brain; Circadian Rhythms; Craniofacial Development; Inositol Phosphates; Mouse Genetics; Mutagenesis; Neurodevelopment; Phosphatase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Behavior, Animal
  • Bipolar Disorder / drug therapy
  • Brain / metabolism*
  • Brain Diseases / drug therapy
  • Circadian Rhythm
  • Disease Models, Animal
  • Ethylnitrosourea / chemistry
  • Female
  • Gene Library
  • Genotype
  • Homozygote
  • Humans
  • Inositol / biosynthesis*
  • Lithium / pharmacology*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Molecular Sequence Data
  • Mutagenesis
  • Mutation
  • Mutation, Missense
  • Phosphoric Monoester Hydrolases / genetics
  • Phosphoric Monoester Hydrolases / metabolism*
  • Recombinant Proteins / metabolism
  • Sequence Homology, Amino Acid
  • Time Factors

Substances

  • Recombinant Proteins
  • Inositol
  • Lithium
  • Phosphoric Monoester Hydrolases
  • myo-inositol-1 (or 4)-monophosphatase
  • Ethylnitrosourea