Fig. 1

Pedigree of the described NP-C case, partial electropherograms (forward strands) of exons 8 and 18 of NPC1, and haplotype analysis of family members using the three informative intragenic markers. Sanger automated DNA sequencing of the entire coding sequence of NPC1 in the proband (II-2) revealed the heterozygous compound genotype, c.[1042C > T];[2780C > T] or p.[Arg348*];[Ala927Val] (reference NPC1 sequence: NM_000271.4). This result was confirmed using a second genomic DNA blood sample from II-2. To determine allelic segregation, we directly examined both pathogenic variants in leukocyte-derived genomic DNA obtained from the proband’s parents (I-1 and I-2) and healthy sibling (II-1). Obligate carrier status was confirmed in I-2, who was heterozygous for the NPC1 c.2780C > T or p.(Ala927Val) (exon 18) variant, and II-1 was found to be an obligate carrier for the NPC1 c.1042C > T or p.(Arg348*) (exon 8) variant. We assume the latter variant is of paternal origin, but it was not detected by automated bidirectional sequencing of total blood leukocyte-derived genomic DNA from I-1. Paternity testing through DNA profiling clearly confirmed the paternity of both siblings (data not shown). Our haplotype analysis failed to identify a common paternal haplotype for this mutation, although it did suggest the presence of a paternal recombination event (rec?). However, our molecular findings are consistent with the presence of paternal germline mosaicism for the c.1042C > T or p.(Arg348*) pathogenic variant. WT: wild-type NPC1 allele