Cut-like homeobox 1 and nuclear factor I/B mediate ENGRAILED2 autism spectrum disorder-associated haplotype function

Hum Mol Genet. 2012 Apr 1;21(7):1566-80. doi: 10.1093/hmg/ddr594. Epub 2011 Dec 16.

Abstract

Both common and rare variants contribute to autism spectrum disorder (ASD) risk, but few variants have been established as functional. Previously we demonstrated that an intronic haplotype (rs1861972-rs1861973 A-C) in the homeobox transcription factor ENGRAILED2 (EN2) is significantly associated with ASD. Positive association has also been reported in six additional data sets, suggesting EN2 is an ASD susceptibility gene. Additional support for this possibility requires identification of functional variants that affect EN2 regulation or activity. In this study, we demonstrate that the A-C haplotype is a transcriptional activator. Luciferase (luc) assays in mouse neuronal cultures determined that the A-C haplotype increases expression levels (50%, P < 0.01, 24 h; 250%, P < 0.0001, 72 h). Mutational analysis indicates that the A-C haplotype activator function requires both associated A and C alleles. A minimal 202-bp element is sufficient for function and also specifically binds a protein complex. Mass spectrometry identified these proteins as the transcription factors, Cut-like homeobox 1 (Cux1) and nuclear factor I/B (Nfib). Subsequent antibody supershifts and chromatin immunoprecipitations demonstrated that human CUX1 and NFIB bind the A-C haplotype. Co-transfection and knock-down experiments determined that both CUX1 and NFIB are required for the A-C haplotype activator function. These data demonstrate that the ASD-associated A-C haplotype is a transcriptional activator, and both CUX1 and NFIB mediate this activity. These results provide biochemical evidence that the ASD-associated A-C haplotype is functional, further supporting EN2 as an ASD susceptibility gene.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Animals
  • Cell Line
  • Child
  • Child Development Disorders, Pervasive / genetics*
  • Gene Expression Regulation
  • Haplotypes*
  • Homeodomain Proteins / biosynthesis
  • Homeodomain Proteins / genetics*
  • Homeodomain Proteins / metabolism*
  • Humans
  • Introns
  • Mice
  • Mice, Inbred C57BL
  • NFI Transcription Factors / metabolism*
  • Nerve Tissue Proteins / biosynthesis
  • Nerve Tissue Proteins / genetics*
  • Nuclear Proteins / metabolism*
  • Primates
  • Repressor Proteins / metabolism*
  • Transcription Factors

Substances

  • CUX1 protein, human
  • Homeodomain Proteins
  • NFI Transcription Factors
  • NFIB protein, human
  • Nerve Tissue Proteins
  • Nuclear Proteins
  • Repressor Proteins
  • Transcription Factors
  • engrailed 2 protein