Reduced polyalanine-expanded Arx mutant protein in developing mouse subpallium alters Lmo1 transcriptional regulation

Hum Mol Genet. 2014 Feb 15;23(4):1084-94. doi: 10.1093/hmg/ddt503. Epub 2013 Oct 10.


Intellectual disability (ID) is a highly prevalent disorder that affects 1-3% of the population. The Aristaless-related homeobox gene (ARX) is a frequently mutated X-linked ID gene and encodes a transcription factor indispensable for proper forebrain, testis and pancreas development. Polyalanine expansions account for over half of all mutations in ARX and clinically give rise to a spectrum of ID and seizures. To understand how the polyalanine expansions cause the clinical phenotype, we studied mouse models of the two most frequent polyalanine expansion mutations (Arx((GCG)7) and Arx(432-455dup24)). Neither model showed evidence of protein aggregates; however, a marked reduction of Arx protein abundance within the developing forebrain was striking. Examining the expression of known Arx target genes, we found a more prominent loss of Lmo1 repression in Arx((GCG7)/Y) compared with Arx(432-455dup24/Y) mice at 12.5 and 14.5 dpc, stages of peak neural proliferation and neurogenesis, respectively. Once neurogenesis concludes both mutant mouse models showed similar loss of Lmo1 repression. We propose that this temporal difference in the loss of Lmo1 repression may be one of the causes accounting for the phenotypic differences identified between the Arx((GCG)7)and Arx(432-455dup24) mouse models. It is yet to be determined what effect these mutations have on ARX protein in affected males in the human setting.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Female
  • Gene Expression Regulation, Developmental*
  • Homeodomain Proteins / genetics*
  • Homeodomain Proteins / metabolism
  • Humans
  • LIM Domain Proteins / genetics*
  • LIM Domain Proteins / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Mutation
  • Neurogenesis
  • Nuclear Proteins / genetics*
  • Nuclear Proteins / metabolism
  • Peptides / genetics
  • Prosencephalon / embryology
  • Prosencephalon / metabolism
  • Telencephalon / embryology
  • Telencephalon / metabolism*
  • Transcription Factors / genetics*
  • Transcription Factors / metabolism
  • Transcription, Genetic


  • ARX protein, mouse
  • Homeodomain Proteins
  • LIM Domain Proteins
  • Lmo1 protein, mouse
  • Nuclear Proteins
  • Peptides
  • Transcription Factors
  • polyalanine