Tracing the genetics of neurological disease to the mutation-directed addition of single hydrogen bonds

Mutations causative of neurological and neurodegenerative disease can occur in coding regions that specify protein domains of low sequence complexity. These autosomal dominant mutations can be idiosyncratic in their recurrent appearance at the same amino acid. Here we report studies of recurrent mutations in proline residues located within low complexity (LC) domains associated with the neurofilament light chain protein, the microtubule-associated tau protein, and the heterogeneous nuclear RNPA2 protein. All such mutations manifest their effects by directing formation of variant proteins endowed with the addition of a single, main chain hydrogen bond specified by the variant amino acid replacing proline. Here we show that methylation of the peptide backbone nitrogen atom associated with these variant amino acids eliminates the aberrant hydrogen bond and restores normal protein function.