 Instead, PABPN1 is involved in the polyadenylation of mRNA precursors.Mutations in PABPN1 that cause this disorder, result when the protein has an extended polyalanine tract (12-17 alanines long vs. the expected amount of 10).The extra alanines cause PABPN1 to aggregate and form clumps within muscles because they are not able to be broken down.