Four novel mutations of the ATP2C1 gene in Chinese patients are associated with familial benign chronic pemphigus

Identification of 2 Novel Mutations in ATP2C1 Gene in Hailey-Hailey Disease and a Literature Review of Variations in a Chinese Han Population

Background

Hailey-Hailey disease (HHD) is a rare autosomal dominant skin condition. The ATP2C1 gene was identified as the defective gene in HHD. To date, 166 pathogenic mutations in ATP2C1 have been observed worldwide. The aim of this study was to identify variations in HHD and summarize the features of the mutations identified in China.

Material/Methods

We examined 2 familial and 2 sporadic cases of HHD. Genomic DNA polymerase chain reaction and direct sequencing of the ATP2C1 were performed from HHD patients, unaffected family members, and 200 healthy individuals. We also searched the published literature for data about the ATP2C1 gene using PubMed and the Chinese Biological Medicine Database.

Results

We detected 3 heterozygous mutations, including 2 novel frameshift mutations (c.819insA (273LfsX) and c.1264insTAGATGG (421LfsX)) and 1 recurrent nonsense mutation (c.115C>T (R39X)). To the best of our knowledge, 90 different mutations (including our current results) have been reported in China, all of which occurred in the Chinese Han population.

Conclusions

Our data may add to the existing list of ATP2C1 mutations and provide new insight into genetic variants of HHD in China.

Four novel ATP2C1 mutations in Chinese patients with Hailey-Hailey disease

Hailey-Hailey disease (HHD) is a kind of autosomal dominant dermatosis. The ATP2C1 gene has been identified as the pathogenic gene of HHD since 2000. In this study, direct DNA sequencing was used to identify ATP2C1 gene mutations in four Chinese families and two sporadic cases with HHD. The entire coding and flanking intronic sequences of ATP2C1 were screened for mutations and five heterozygous mutations of the ATP2C1 gene were detected in the four pedigrees and two sporadic cases with HHD. Four of them were novel, including three frame-shift mutations (c.1330delC, c.888_889insT, c.478_479insA) and one nonsense mutation (c.1720C>T). These data added new variants to the database of ATP2C1 mutations associated with HHD.

ATP2C1 gene mutations in Hailey-Hailey disease and possible roles of SPCA1 isoforms in membrane trafficking

ATP2C1 gene codes for the secretory pathway Ca(2+)/Mn(2+)-ATPase pump type 1 (SPCA1) localizing at the golgi apparatus. Mutations on the human ATP2C1 gene, causing decreased levels of the SPCA1 expression, have been identified as the cause of the Hailey-Hailey disease, a rare skin disorder. In the last few years, several mutations have been described, and here we summarize how they are distributed along the gene and how missense mutations affect protein expression. SPCA1 is expressed in four different isoforms through alternative splicing of the ATP2C1 gene and none of these isoforms is differentially affected by any of these mutations. However, a better understanding of the tissue specific expression of the isoforms, their localization along the secretory pathway, their specific binding partners and the role of the C-terminal tail making isoforms different from each other, will be future goals of the research in this field.

Hailey-Hailey disease: investigation of a possible compensatory SERCA2 up-regulation and analysis of SPCA1, p63, and IRF6 expression

Hailey-Hailey disease (HHD) is caused by heterozygous mutations in the ATP2C1 gene, encoding the secretory pathway Ca(2+) ATPase1 (SPCA1). SPCA1 and sarco/endoplasmic reticulum Ca(2+) ATPase2 (SERCA2) encoded by ATP2A2 are two essential calcium pumps needed for Ca(2+) homeostasis maintenance in keratinocytes. ATP2A2 mutations cause another hereditary skin disorder, Darier's disease (DD). Previously, the compensatory expression of SPCA1 for SERCA2 insufficiency in DD was demonstrated, but it is not known whether a similar compensatory mechanism exists in HHD. Additionally, little is known about the role of p63 and interferon regulatory factor 6 (IRF6), two important regulatory factors involved in keratinocyte proliferation and differentiation, in HHD. Here, we used the skin biopsy samples from patients with HHD and human primary keratinocytes transfected with ATP2C1 siRNA to search for potential pathogenic mechanisms in HHD. We observed normal SERCA2 levels, but reduced p63, and increased IRF6 levels in HHD epidermal tissues and SPCA1-deficient keratinocytes. This suggests that there is no compensatory mechanism by SERCA2 for the SPCA1 deficiency in HHD. Moreover, the abnormal expression of p63 and IRF6 appears to be related to SPCA1 haploinsufficiency, with down-regulation of p63 probably resulting from IRF6 overexpression in HHD. We speculate that a novel pathogenic mechanism involving SPCA1, p63, and IRF6 may play a role in the skin lesions occurring in HHD.