Epigenetic changes during neuronal differentiation contribute to neuro-specific alternative splicing patterns

IGNACIO E. SCHOR; ANA FISZBEIN; ALBERTO KORNBLIHTT

Iguazú

Simposio; Gene Expression and RNA Processing; 2011

ICGEB - ANPCYT - CONICET

Alternative splicing is coupled to transcription, with changes in transcriptional elongation properties resulting in different splicing outcomes. Our previous work shows an example of how intragenic chromatin modulation can affect alternative splicing: depolarization of the membrane potential of neuronal cells triggers an increase in intragenic H3 acetylation along the NCAM gene, which results in skipping of the alternative exon 18 (E18) from the mature mRNA. Other results from our group have shown that induction of an intragenic repressive chromatin conformation results in more inclusion of an alternative exon associated with less processivity of the RNA pol II. Using the NCAM E18 exon as a model, we found evidence that neuronal differentiation of N2a cells causes, contrary to what is seen after depolarization, intragenic increase in repressive histone modifications (H3K9me2 and H3K27me3) which correlates with enhanced E18 inclusion. Also, differentiation-induced inclusion can be reversed by treatment with DNA and histone methyltransferases inhibitors. The same association between repressive histone marks and increased inclusion of alternative exons is seen for the fibronectin gene. Also, by combining available ChIP-seq and splicing microarray data we were able a new gene (Tcf7l2) with apparent chromatin-dependent regulation of alternative splicing during neuronal differentiation. As predicted, the increase of the neuro-specific isoform of Tcf7l2 is also prevented by inhibiting DNA methylation. This leads to a model where intragenic chromatin can be physiologically modulated in both directions (repressive/permissive) with functional consequences to coupled alternative splicing.