Heterogeneous mutations of the ATP2C1 gene causing Hailey-Hailey disease in Hong Kong Chinese

Two novel mutations in the ATP2C1 gene found in Japanese patients with Hailey-Hailey disease

Hailey-Hailey disease (HHD) is an autosomal dominant genodermatosis and the defective gene in HHD is ATP2C1, which encodes secretory pathway Ca²⁺ /Mn²⁺ ATPase type 1 (SPCA1). Here we report four Japanese HHD patients showing three kinds of mutations with premature termination codons in the ATP2C1 gene, including two novel ones. Patient 1 was a 39-year-old man with a novel heterozygous mutation, c.664dup in exon 8 (p.N215Kfs*26). Patient 2 was a 33-year-old man (the younger brother of patient 1) with the same mutation as patient 1. Patient 3 was a 55-year-old man with a previously reported heterozygous mutation, c.519dup in exon 7 (p.R174Tfs*4). Patient 4 was a 33-year-old woman with a novel heterozygous mutation, c.2640del in exon 27 (p.L881Ffs*10). The clinical characteristics of our four cases varied in disease severity and the response to treatment. The present cases enrich the database of mutational analysis for HHD.

Ending diagnostic odyssey using clinical whole-exome sequencing (CWES)

Objectives

Most rare diseases are genetic diseases. Due to the diversity of rare diseases and the high likelihood of patients with rare diseases to be undiagnosed or misdiagnosed, it is not unusual that these patients undergo a long diagnostic odyssey before they receive a definitive diagnosis. This situation presents a clear need to set up a dedicated clinical service to end the diagnostic odyssey of patients with rare diseases.

Methods

Therefore, in 2014, we started an Undiagnosed Diseases Program in Hong Kong with the aim of ending the diagnostic odyssey of patients and families with rare diseases by clinical whole-exome sequencing (CWES), who have not received a definitive diagnosis after extensive investigation.

Results

In this program, we have shown that genetic diseases diagnosed by CWES were different from that using traditional approaches indicating that CWES is an essential tool to diagnose rare diseases and ending diagnostic odysseys. In addition, we identified several novel genes responsible for monogenic diseases. These include the TOP2B gene for autism spectrum disorder, the DTYMK gene for severe cerebral atrophy, the KIF13A gene for a new mosaic ectodermal syndrome associated with hypomelanosis of Ito, and the CDC25B gene for a new syndrome of cardiomyopathy and endocrinopathy.

Conclusions

With the incorporation of CWES in an Undiagnosed Diseases Program, we have ended diagnostic odysseys of patients with rare diseases in Hong Kong in the past 7 years. In this program, we have shown that CWES is an essential tool to end diagnostic odysseys. With the declining cost of next-generation sequencers and reagents, CWES set-ups are now affordable for clinical laboratories. Indeed, owing to the increasing availability of CWES and treatment modalities for rare diseases, precedence can be given to both common and rare medical conditions.

Two Novel Variants and One Previously Reported Variant in the ATP2C1 Gene in Chinese Hailey-Hailey Disease Patients

Hailey-Hailey disease (HHD) is a rare autosomal dominant genodermatosis. It is characterized clinically by recurrent erosions, blisters and erythematous plaques at the sites of friction and intertriginous areas. The pathogenic gene of HHD was reported to be the ATPase calcium-transporting type 2C member 1 gene (ATP2C1). In this study, genomic DNA polymerase chain reaction (PCR) and direct sequencing of ATP2C1 were performed from 3 Chinese pedigrees and 4 sporadic cases of HHD. We detected 3 heterozygous mutations, including 2 novel mutations (c.1673_1674insGTTG and c.2225A>G) and 1 recurrent nonsense mutation (c.1402C>T; NM_014382.4). The ATP2C1 gene was also screened in the asymptomatic members of pedigrees. Our results would further expand the mutation spectrum of the ATP2C1 gene and be helpful in the genetic counseling of patients with HHD.

Whole exome sequencing improves mutation detection in Hailey-Hailey disease

Hailey-Hailey disease (HHD) is an autosomal dominant monogenic disease that is defective in the ATP2C1 gene. In previous studies, Sanger sequencing was the main method applied to detect mutations in HHD patients, and no mutations in the ATP2C1 gene were found in 12-55% of those reported. The aim of our study was to carry out whole exome sequencing (WES) for the HHD patients in whom efforts to identify mutations by Sanger sequencing had failed, and to find a new pathogenic gene. WES was performed using genomic DNA from 13 HHD patients and 364 in-house healthy controls. Potential pathogenic mutations were subsequently validated by Sanger sequencing. As a result, eight mutations in the ATP2C1 gene were identified using WES. In the remaining five patients, we found one mutation in the ATP2A2 gene which was the causal gene of Darier's disease. Four patients had no detectable mutations in ATP2C1 and the other ATPase genes. Together with our previous study in 2019, the total mutation rate was calculated to be 47/52 (90.4%). These findings demonstrate that WES is capable of improving the mutation detection sensitivity in HHD compared with Sanger sequencing.

Novel and recurrent variants of ATP2C1 identified in patients with Hailey-Hailey disease

Hailey-Hailey disease (HHD) is a rare, late-onset autosomal dominant genodermatosis characterized by blisters, vesicular lesions, crusted erosions, and erythematous scaly plaques predominantly in intertriginous regions. HHD is caused by ATP2C1 mutations. About 180 distinct mutations have been identified so far; however, data of only few cases from Central Europe are available. The aim was to analyze the ATP2C1 gene in a cohort of Polish HHD patients. A group of 18 patients was enrolled in the study based on specific clinical symptoms. Mutations were detected using Sanger or next generation sequencing. In silico analysis was performed by prediction algorisms and dynamic structural modeling. In two cases, mRNA analysis was performed to confirm aberrant splicing. We detected 13 different mutations, including 8 novel, 2 recurrent (p.Gly850Ter and c.325-3 T > G), and 6 sporadic (c.423-1G > T, c.899 + 1G > A, p.Leu539Pro, p.Thr808TyrfsTer16, p.Gln855Arg and a complex allele: c.[1610C > G;1741 + 3A > G]). In silico analysis shows that all novel missense variants are pathogenic or likely pathogenic. We confirmed pathogenic status for two novel variants c.325-3 T > G and c.[1610C > G;1741 + 3A > G] by mRNA analysis. Our results broaden the knowledge about genetic heterogeneity in Central European patients with ATP2C1 mutations and also give further evidence that careful and multifactorial evaluation of variant pathogenicity status is essential.

Factors in the disease severity of ATP1A3 mutations: Impairment, misfolding, and allele competition

Dominant mutations of ATP1A3, a neuronal Na,K-ATPase α subunit isoform, cause neurological disorders with an exceptionally wide range of severity. Several new mutations and their phenotypes are reported here (p.Asp366His, p.Asp742Tyr, p.Asp743His, p.Leu924Pro, and a VUS, p.Arg463Cys). Mutations associated with mild or severe phenotypes [rapid-onset dystonia-parkinsonism (RDP), alternating hemiplegia of childhood (AHC), or early infantile epileptic encephalopathy (EIEE)] were expressed in HEK-293 cells. Paradoxically, the severity of human symptoms did not correlate with whether there was enough residual activity to support cell survival. We hypothesized that distinct cellular consequences may result not only from pump inactivation but also from protein misfolding. Biosynthesis was investigated in four tetracycline-inducible isogenic cell lines representing different human phenotypes. Two cell biological complications were found. First, there was impaired trafficking of αβ complex to Golgi apparatus and plasma membrane, as well as changes in cell morphology, for two mutations that produced microcephaly or regions of brain atrophy in patients. Second, there was competition between exogenous mutant ATP1A3 (α3) and endogenous ATP1A1 (α1) so that their sum was constant. This predicts that in patients, the ratio of normal to mutant ATP1A3 proteins will vary when misfolding occurs. At the two extremes, the results suggest that a heterozygous mutation that only impairs Na,K-ATPase activity will produce relatively mild disease, while one that activates the unfolded protein response could produce severe disease and may result in death of neurons independently of ion pump inactivation.

A Case of Hailey-Hailey Disease Managed With Oral Magnesium Citrate and High-Dose Vitamin D3

Hailey-Hailey disease, or benign familial pemphigus, is a rare blistering disease originally described in 1939. The disease is due to an autosomal dominant mutation in the ATP2C1 gene on chromosome 3, which encodes for an adenosine triphosphate–dependent calcium pump in the Golgi apparatus whose function is to maintain intercellular calcium homeostasis. Common treatments for Hailey-Hailey disease involve calcineurin inhibitors, topical corticosteroids, topical or systemic antibiotics, topical antifungals, ablative lasers, or botulin toxin. In this case report, we highlight a unique case of Hailey-Hailey disease that was resistant to many conventional therapies and ultimately managed with oral magnesium citrate and high-dose vitamin D3.

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.

The role of the ATP2C1 gene in Hailey-Hailey disease

Hailey-Hailey disease (HHD) is a rare autosomal dominant acantholytic dermatosis, characterized by a chronic course of repeated and exacerbated skin lesions in friction regions. The pathogenic gene of HHD was reported to be the ATPase calcium-transporting type 2C member 1 gene (ATP2C1) located on chromosome 3q21-q24. Its function is to maintain normal intracellular concentrations of Ca2+/Mn2+ by transporting Ca2+/Mn2+ into the Golgi apparatus. ATP2C1 gene mutations are reportedly responsible for abnormal cytosolic Ca2+/Mn2+ levels and the clinical manifestations of HHD. Environmental factors and genetic modifiers may also affect the clinical variability of HHD. This article aims to critically discuss the clinical and pathological features of HHD, differential diagnoses, and genetic and functional studies of the ATP2C1 gene in HHD. Further understanding the role of the ATP2C1 gene in the pathogenesis of HHD by genetic, molecular, and animal studies may contribute to a better clinical diagnosis and provide new strategies for the treatment and prevention of HHD.

Mendelian Disorders of Cornification Caused by Defects in Intracellular Calcium Pumps: Mutation Update and Database for Variants in ATP2A2 and ATP2C1 Associated with Darier Disease and Hailey-Hailey Disease

The two disorders of cornification associated with mutations in genes coding for intracellular calcium pumps are Darier disease (DD) and Hailey-Hailey disease (HHD). DD is caused by mutations in the ATP2A2 gene, whereas the ATP2C1 gene is associated with HHD. Both are inherited as autosomal-dominant traits. DD is mainly defined by warty papules in seborrheic and flexural areas, whereas the major symptoms of HHD are vesicles and erosions in flexural skin. Both phenotypes are highly variable. In 12%-40% of DD patients and 12%-55% of HHD patients, no mutations in ATP2A2 or ATP2C1 are found. We provide a comprehensive review of clinical variability in DD and HHD and a review of all reported mutations in ATP2A2 and ATP2C1. Having the entire spectrum of ATP2A2 and ATP2C1 variants allows us to address the question of a genotype-phenotype correlation, which has not been settled unequivocally in DD and HHD. We created a database for all mutations in ATP2A2 and ATP2C1 using the Leiden Open Variation Database (LOVD v3.0), for variants reported in the literature and future inclusions. This data may be of use as a reference tool in further research on treatment of DD and 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.