Genomic sequencing and mRNA expression of the ΔK170 mutant allele. (A) Sanger sequencing validates segregation with disease of a 3-bp deletion in the ACD gene, encoding the protein TPP1. The deletion (c.499_501del; p.Lys170del) was detected in the proband, mother, and maternal grandmother. The deletion was not present in the father and maternal grandfather. (B) RT-PCR of a 400-bp region across the ΔK170 region of TPP1 (left). RNA was isolated from fibroblasts of the proband (ΔK170) and the cell line HCT116 as a positive control for WT TPP1 expression (WT). Plasmids encoding WT or ΔK170 TPP1 sequence (pWT and pΔK170) were amplified as positive controls. XmnI digestion of the PCR products from the left panel (right). WT sequence is digested into 2 pieces of 212 and 188 bp, whereas the ΔK170 sequence remains uncut.