Complex epigenetic regulation of Engrailed-2 (EN-2) homeobox gene in the autism cerebellum

Abstract

The elucidation of epigenetic alterations in the autism brain has potential to provide new insights into the molecular mechanisms underlying abnormal gene expression in this disorder. Given strong evidence that engrailed-2 (EN-2) is a developmentally expressed gene relevant to cerebellar abnormalities and autism, the epigenetic evaluation of this candidate gene was undertaken in 26 case and control post-mortem cerebellar samples. Assessments included global DNA methylation, EN-2 promoter methylation, EN-2 gene expression and EN-2 protein levels. Chromatin immunoprecipitation was used to evaluate trimethylation status of histone H3 lysine 27 (H3K27) associated with gene downregulation and histone H3 lysine 4 (H3K4) associated with gene activation. The results revealed an unusual pattern of global and EN-2 promoter region DNA hypermethylation accompanied by significant increases in EN-2 gene expression and protein levels. Consistent with EN-2 overexpression, histone H3K27 trimethylation mark in the EN-2 promoter was significantly decreased in the autism samples relative to matched controls. Supporting a link between reduced histone H3K27 trimethylation and increased EN-2 gene expression, the mean level of histone H3K4 trimethylation was elevated in the autism cerebellar samples. Together, these results suggest that the normal EN-2 downregulation that signals Purkinje cell maturation during late prenatal and early-postnatal development may not have occurred in some individuals with autism and that the postnatal persistence of EN-2 overexpression may contribute to autism cerebellar abnormalities.

An epigenetic view of developmental diseases: new targets, new therapies

“…[34] Increased histone H3K4 trimethylation and decreased histone H3K27 trimethylation are observed in the engrailed-2(EN-2) homeobox gene in the autism samples, which is a gene relevant to cerebellar abnormalities and autism. [35] Recent studies have found that many ASD associated genes, for example, oxytocin receptor gene (OXTR), Glutamate decarboxylase 1 (GAD1), and Engrailed-2 (EN2), exhibited altered DNA methylation and demethylation status. [35][36][37] During neuronal development of human, DhMRs (differentially hydroxymethylated regions) well overlap with FMR1 regulated genes, and autism related genes.…”

“…[35] Recent studies have found that many ASD associated genes, for example, oxytocin receptor gene (OXTR), Glutamate decarboxylase 1 (GAD1), and Engrailed-2 (EN2), exhibited altered DNA methylation and demethylation status. [35][36][37] During neuronal development of human, DhMRs (differentially hydroxymethylated regions) well overlap with FMR1 regulated genes, and autism related genes. [38] Interestingly, Tet1 expression increases in autistic brain of human and increased enrichment of 5hmC at the promoters of RELN and GAD1 is associated with autism.…”

The Genetic and Epigenetic Basis Involved in the Pathophysiology of ASD: Therapeutic Implications

“…• Methylation level of specific genes in nonsyndromic ASD: The postmortem brain tissues from ASD patients show increased DNA methylation within the genes of: oxytocin receptor (OXTR) [163], RORA [164], Engrailed-2 (EN2) homeobox gene [165], Reelin (RELN) [166], and BCL2 gene [167].…”

Intracellular Pathways Associated with the Etiology of Autism

“…Engrailed homeobox 2 (EN2) is a homeobox gene that is critical to the development of the midbrain and cerebellum [49]. It regulates the combined processes of cell division, differentiation and organ development.…”