The University of Texas Health Science Center researchers said they've discovered the mechanism by which the protein MED12 ensures correct neuronal gene expression. Mutations associated with X-linked mental retardation are known to disrupt the function of the protein.

"We found that MED12 directs a histone-modifying enzyme to mark neuronal genes with a repressive signal and, further, that X-linked mental retardation-causing mutations in MED12 disrupt this repression function, leading to the inappropriate expression of neuronal genes," lead author Thomas Boyer said in statement.

Boyer said the findings, published in the journal Molecular Cell, "suggest a possible epigenetic basis to define the role of MED12 in the origin of X-linked mental retardation through altered neuronal development."