Mutations in MFSD8/CLN7 are a frequent cause of variant-late infantile neuronal ceroid lipofuscinosis

The neuronal ceroid lipofuscinoses (NCL) are a group of genetically heterogeneous neurodegenerative disorders. The recent identification of the MFSD8/CLN7 gene in a variant-late infantile form of NCL (v-LINCL) in affected children from Turkey prompted us to examine the relative frequency of variants in this gene in Italian patients with v-LINCL. We identified nine children harboring 11 different mutations in MFSD8/CLN7. Ten mutations were novel and included three nonsense (p.Arg35Stop, p.Glu381Stop, p.Arg482Stop), four missense (p.Met1Thr, p.Gly52Arg, p.Thr294Lys, p.Pro447Leu), two splice site mutations (c.863+3_4insT, c.863+1G>C), and a 17-bp deletion predicting a frameshift and premature protein truncation (c.627_643del17/p.Met209IlefsX3). The clinical phenotype, which was similar to that of the Turkish v-LINCL cases, was not influenced by type and location of the mutation nor the length of the predicted residual gene product. As well as identifying novel variants in MFSD8/CLN7, this study contributes to a better molecular characterization of Italian NCL cases, and will facilitate medical genetic counseling in such families. The existence of a subset of v-LINCL cases without mutations in any of the known NCL genes suggests further genetic heterogeneity.