Desmosomes are major cell adhesion junctions, particularly prominent in the epidermis and cardiac tissue and are important for the rigidity and strength of the cells. The desmosome consists of several proteins, of which desmoplakin is the most abundant. Here, we describe the first recessive human mutation, 7901delG, in the desmoplakin gene which causes a generalized striate keratoderma particularly affecting the palmoplantar epidermis, woolly hair and a dilated left ventricular cardiomyopathy. A number of the patients with this syndromic disorder suffer heart failure in their teenage years, resulting in early morbidity. All tested affected members of three families from Ecuador were homozygous for this mutation which produces a premature stop codon leading to a truncated desmoplakin protein missing the C domain of the tail region. Histology of the skin revealed large intercellular spaces and clustering of desmosomes at the infrequent sites of keratinocyte adhesion. Immunohistochemistry of skin from the patients showed a perinuclear localization of keratin in suprabasal keratinocytes, suggesting a collapsed intermediate filament network. This study demonstrates the importance of desmoplakin in the attachment of intermediate filaments to the desmosome. In contrast to null Desmoplakin mice which die in early development, the truncated protein due to the homozygous 7901delG mutation in humans is not embryonic lethal. This suggests that the tail domain of desmoplakin is not required for establishing tissue architecture during development.

Esophageal squamous cell carcinoma (ESCC) is the predominant form of esophageal cancer in Japan. Smoking and drinking alcohol are environmental risk factors for ESCC, whereas single nucleotide polymorphisms in ADH1B and ALDH2, which increase harmful intermediates produced by drinking alcohol, are genetic risk factors. We conducted a large-scale genomic analysis of ESCCs from patients in Japan to determine the mutational landscape of this cancer. We performed whole-exome sequence analysis of tumor and nontumor esophageal tissues collected from 144 patients with ESCC who underwent surgery at 5 hospitals in Japan. We also performed single-nucleotide polymorphism array-based copy number profile and germline genotype analyses of polymorphisms in ADH1B and ALDH2. Polymorphisms in CYP2A6, which increase harmful effects of smoking, were analyzed. Functions of TET2 mutants were evaluated in KYSE410 and HEK293FT cells. A high proportion of mutations in the 144 tumor samples were C to T substitution in CpG dinucleotides (called the CpG signature) and C to G/T substitutions with a flanking 5′ thymine (called the APOBEC signature). Based on mutational signatures, patients were assigned to 3 groups, which associated with environmental (drinking and smoking) and genetic (polymorphisms in ALDH2 and CYP2A6) factors. Many tumors contained mutations in genes that regulate the cell cycle (TP53, CCND1, CDKN2A, FBXW7); epigenetic processes (MLL2, EP300, CREBBP, TET2); and the NOTCH (NOTCH1, NOTCH3), WNT (FAT1, YAP1, AJUBA) and receptor-tyrosine kinase−phosphoinositide 3-kinase signaling pathways (PIK3CA, EGFR, ERBB2). Mutations in EP300 and TET2 correlated with shorter survival times, and mutations in ZNF750 associated with an increased number of mutations of the APOBEC signature. Expression of mutant forms of TET2 did not increase cellular levels of 5-hydroxymethylcytosine in HEK293FT cells, whereas knockdown of TET2 increased the invasive activity of KYSE410 ESCC cells. Computational analyses associated the mutations in NFE2L2 we identified with transcriptional activation of its target genes. We associated environmental and genetic factors with base substitution patterns of somatic mutations and provide a registry of genes and pathways that are disrupted in ESCCs. These findings might be used to design specific treatments for patients with esophageal squamous cancers.