TPP1 and juvenile neuronal ceroid lipofuscinosis: To test this hypothesis, we carried out a splicing assay that showed the noncoding allele, c.508+4A>G, functions as a nonessential splice site leading to aberrant splicing compared with the normal allele, which led to decreased, but not complete, abolishment of the native protein product (Figure 3C), thereby providing a biochemical basis for a molecular diagnosis of atypical TPP1-associated JNCL.