Hailey-Hailey disease maps to a 5 cM interval on chromosome 3q21-q24

The Pathogenic Mechanism of the ATP2C1 p.Ala109_Gln120del Mutation in Hailey-Hailey Disease

Background

Hailey-Hailey disease (HHD) is an autosomal dominant cutaneous disorder that manifests as repeated blisters and erosions on flexural or intertriginous skin areas. The calcium-transporting ATPase type 2C member 1 gene (ATP2C1) encodes the secretory pathway Ca²⁺/Mn²⁺-ATPase 1 (SPCA1), whose deficiency is responsible for HHD. An ATP2C1 splice-site mutation (c.325-2A>G, p.Ala109_Gln120del) was previously identified in a Han Chinese family with HHD.

Methods

In this study, the identified ATP2C1 splice-site mutation (c.325-2A>G, p.Ala109_Gln120del) was investigated in transfected human embryonic kidney 293 cells to analyze its pathogenic mechanism in HHD patients by using cycloheximide chase assay, CCK8 assay and in silico modeling of SPCA1 mutant.

Results

Cycloheximide chase assay showed that the degradation rate of the SPCA1 mutant was not obviously faster than that of the normal SPCA1. CCK8 assay showed that cell proliferation rates in the wild-type, A109_Q120del, and empty vector control groups all decreased in the gradient Mn²⁺ solutions in a dose-dependent manner. The cell proliferation rate in the wild-type was lower than that in the A109_Q120del and empty vector control (both P < 0.01), indicating overexpression of normal SPCA1 may rather induce Golgi stress, and even cell death. The cell proliferation rate in the A109_Q120del was lower than that in the empty vector control (P < 0.01), indicating that overexpression of the mutated SPCA1 may decrease its detoxification capability. Three-dimensional (3D) structure model of SPCA1 built by SWISS-MODEL and PyMOL showed that absence of the 12 amino acids from p.Ala109 to p.Gln120 in the SPCA1 mutant can cause obviously shortened transmembrane 2, which may affect correct localization of SPCA1 on the Golgi.

Conclusion

These results demonstrate that the ATP2C1 mutation (c.325-2A>G, p.Ala109_Gln120del) may cause impaired SPCA1 capability to detoxify Mn²⁺ and abnormal SPCA1 structure, which reveals a new side for the pathogenesis of HHD.

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.

A novel splice-site mutation in the ATP2C1 gene of a Chinese family with Hailey-Hailey disease

Hailey-Hailey disease (HHD), also known as familial benign chronic pemphigus, is an autosomal dominant genodermatosis. It is characterized by erosions, blisters and erythematous plaques at sites of friction or intertriginous areas. The pathogenic gene of HHD has been revealed as the ATPase secretory pathway Ca²⁺ transporting 1 gene ( ATP2C1), which encodes the protein, secretory pathway Ca ²⁺/Mn ²⁺-ATPase 1 (SPCA1). ATP2C1 gene mutations are responsible for HHD by resulting in abnormal Ca ²⁺ homeostasis in the skin and giving rise to acantholysis, a characteristic pathology of HHD. In this study, a four-generation family containing three HHD sufferers was recruited. Direct sequencing of the ATP2C1 gene was performed in the proband and other available family members. Reverse-transcriptase polymerase chain reaction analysis was conducted to show the potential variant effect on ATP2C1 splicing. A novel heterozygous c.325-2A>G transition at the splice acceptor site of intron 4 in the ATP2C1 gene was identified, and it co-segregated with the disease in this family. The mutation resulted in exon 5 skipping and an in-frame deletion of 12 amino acids (p.Ala109_Gln120del) in SPCA1. This splice-site mutation may be responsible for HHD in this family. This study would further expand the mutation spectrum of the ATP2C1 gene and may be helpful in the genetic counseling and prenatal diagnosis of HHD.

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.

The genetics of human skin disease

The skin is composed of a variety of cell types expressing specific molecules and possessing different properties that facilitate the complex interactions and intercellular communication essential for maintaining the structural integrity of the skin. Importantly, a single mutation in one of these molecules can disrupt the entire organization and function of these essential networks, leading to cell separation, blistering, and other striking phenotypes observed in inherited skin diseases. Over the past several decades, the genetic basis of many monogenic skin diseases has been elucidated using classical genetic techniques. Importantly, the findings from these studies has shed light onto the many classes of molecules and essential genetic as well as molecular interactions that lend the skin its rigid, yet flexible properties. With the advent of the human genome project, next-generation sequencing techniques, as well as several other recently developed methods, tremendous progress has been made in dissecting the genetic architecture of complex, non-Mendelian skin diseases.

Acantholytic dermatosis of the crural folds with ATP2C1 mutation is a possible variant of Hailey-Hailey Disease

BACKGROUND

We describe a patient with acantholytic dermatosis of the crural folds (ADCF) that was misdiagnosed and treated as condyloma acuminata for 13 years. After many skin biopsies consistently showed epidermal acantholysis and negative human papillomavirus serotyping excluded condyloma acuminata, a diagnosis of ADCF was considered most likely.

OBJECTIVE AND CONCLUSION

Acitretin effectively suppressed the symptomatic hyperkeratosis. Subsequent genetic testing revealed a deletion in the ATP2C1 gene that led us to conclude that this case of ADCF is probably a variant of familial benign chronic pemphigus (Hailey-Hailey disease).

Calcium pumps and keratinocytes: lessons from Darier's disease and Hailey-Hailey disease

Darier's disease and Hailey-Hailey disease are autosomal dominantly inherited skin disorders in which desmosomal adhesion between keratinocytes is abnormal. ATP2A2 and ATP2C1 have been identified as the causative genes for Darier's disease and Hailey-Hailey disease, respectively. ATP2A2 encodes the sarco(endo)plasmic reticulum Ca(2+)-ATPase isoform 2 (SERCA2) pump, while ATP2C1 encodes a secretory pathway Ca(2+)/Mn(2+)-ATPase (SPCA1) found in the Golgi apparatus. We review recent work into the function of these pumps in human keratinocytes and discuss how mutations in these genes might cause these diseases by altering the formation or stability of desmosomes.

Mutation analysis of ATP2C1 gene in Taiwanese patients with Hailey-Hailey disease

BACKGROUND

Hailey-Hailey disease (HHD) is an autosomal dominant disorder with recurrent eruption of vesicles and bullae involving predominantly the neck, groin and axillary regions. Histopathology shows suprabasal cleavage in epidermal cells. Recent studies have revealed that HHD is caused by mutations in the ATP2C1 gene encoding a novel Ca2+ pump.

OBJECTIVES

To analyse the mutations of the ATP2C1 gene in Taiwanese patients with HHD.

METHODS

In total, five familial and two sporadic cases of HHD were retrieved from the medical records. The diagnosis of HHD was made based on the characteristic clinical features and histopathological evidence. All 27 exons and flanking intron boundaries were amplified by polymerase chain reaction and products analysed by direct sequencing.

RESULTS

We identified six novel mutations and one reported mutation: three deletion mutations (nt884-904del, 1459delCTCA, 1975delA), two non-sense mutations (R39X, R783X), one mis-sense mutation (A730T) and one splicing mutation (483 + 2T-->A). The non-sense mutation R39X had been reported previously; the other six mutations are novel mutations.

CONCLUSIONS

These results demonstrate that a spectrum of ATP2C1 gene mutations is present in Taiwanese HHD patients.

Mutations of ATP2C1 in Japanese patients with Hailey-Hailey disease: intrafamilial and interfamilial phenotype variations and lack of correlation with mutation patterns

We report herein mutations of ATP2C1 in 11 Japanese patients with Hailey-Hailey disease gene (including five previously reported) and compare the mutation pattern with clinical phenotypes. Patients with missense mutations and some of those with mutations causing premature termination showed erythema and erosions primarily at intertriginous areas. In two families with unique mutations, one with an in-frame three amino acid deletion plus an eight amino acid insertion and one with a two base pair deletion predicted to cause premature truncation, some affected individuals had unique clinical features -- generalization of Hailey-Hailey disease and generalized skin eruption resembling keratotic papules in Darier's disease -- but other affected individuals did not, suggesting the presence of severe intrafamilial phenotype variations. Our findings suggest that differences in clinical phenotypes are probably related to factors other than the type of causative mutation.

Squamous cell carcinoma arising in Hailey-Hailey disease

Hailey-Hailey disease is a recurrent, autosomal dominant vesiculobullous dermatotis with a predilection for intertrigenous areas. We report what we believe to be the first case of squamous cell carcinoma arising de novo in a skin lesion of Hailey-Hailey disease. The occurrence of malignant neoplasms arising in the skin lesions of Hailey-Hailey disease and other acantholytic dermatoses is reviewed.

Dissociation of intra- and extracellular domains of desmosomal cadherins and E-cadherin in Hailey-Hailey disease and Darier's disease

In order to clarify the pathomechanism of acantholysis in Hailey-Hailey disease (HHD) and Darier's disease (DD), the distribution of desmosomal and adherens junction-associated proteins was studied in the skin of patients with HHD (n = 4) and DD (n = 3). Domain-specific antibodies were used to determine the cellular localization of the desmosomal transmembrane glycoproteins (desmogleins 1 and 3 and desmocollin), desmosomal plaque proteins (desmoplakin, plakophilin and plakoglobin) and adherens junction-associated proteins (E-cadherin, alpha-catenin, beta-catenin and actin). A significant difference in staining patterns between intra- and extracellular domains of desmosomal cadherins and E-cadherin was demonstrated in acantholytic cells in both HHD and DD, but not in those in pemphigus vulgaris and pemphigus foliaceus samples used as controls. In acantholytic cells in HHD and DD, antibodies against attachment plaque proteins and intracellular epitopes of desmosomal cadherins exhibited diffuse cytoplasmic staining, whereas markedly reduced staining was observed with antibodies against extracellular epitopes of the desmogleins. Similarly, membrane staining of an intracellular epitope of E-cadherin was preserved, while immunoreactivity of an extracellular epitope of E-cadherin was destroyed. While the DD gene has been identified as ATP2A2, the gene for HHD has not been clarified. The dissociation of intra- and extracellular domains of desmosomal cadherin and E-cadherin is characteristic of the acantholytic cells in HHD and DD, and not of pemphigus. This common phenomenon in HHD and DD might be closely related to the pathophysiological mechanisms in both conditions.

Squamous cell carcinoma arising in Hailey-Hailey disease of the vulva

A 61-year-old woman, who was known to have Hailey-Hailey disease, presented with increasing vulval soreness. Biopsy showed vulval intraepithelial neoplasia (VIN) 3 and subsequent histology from a vulvectomy specimen showed extensive VIN with early invasive squamous cell carcinoma. This may be another example of chronic inflammation of the vulval area leading to the development of squamous cell carcinoma. However, in this case, chronic human papillomavirus may also have played a part, leading to VIN and reactivation of the Hailey-Hailey disease. We can find no previous reports of squamous cell carcinoma developing in the setting of Hailey-Hailey disease.

Mutations in ATP2C1, encoding a calcium pump, cause Hailey-Hailey disease

Hailey-Hailey disease (HHD, MIM 16960) is inherited in an autosomal dominant manner and characterized by persistent blisters and erosions of the skin. Impaired intercellular adhesion and epidermal blistering also occur in individuals with pemphigus (which is due to autoantibodies directed against desmosomal proteins) and in patients with Darier disease (DD, MIM 124200), which is caused by mutations in a gene encoding a sarco/endoplasmic reticulum (ER)-Golgi calcium pump. We report here the identification of mutations in ATP2C1, encoding the human homologue of an ATP-powered pump that sequesters calcium into the Golgi in yeast, in 21 HHD kindreds. Regulation of cytoplasmic calcium is impaired in cultured keratinocytes from HHD patients, and the normal epidermal calcium gradient is attenuated in vivo in HHD patients. Our findings not only provide an understanding of the molecular basis of HHD, but also underscore the importance of calcium control to the functioning of stratified squamous epithelia.

Hereditary diseases of desmosomes

Desmosomes are key adhesion complexes in most epithelia, including epidermis. Although structural components of desmosomes have been identified as target antigens in several of the autoimmune blistering skin diseases, there are relatively few data on inherited disorders arising from mutations in genes encoding these proteins and glycoproteins. For example, an association between an inherited abnormality of desmosomes and Darier disease and Hailey Hailey disease has been proposed on histopathological grounds, but genetic linkage studies have not invoked known desmosomal gene loci. However, linkage analyses have implicated one or more of the desmosomal cadherins (desmogleins 1-3, desmocollins 1-3), the genes for which are tightly clustered within a 650-kb region on 18q12.1, in the pathogenesis of a different autosomal dominant genodermatosis, striate palmoplantar keratoderma. In addition, a rare autosomal recessive skin fragility-ectodermal dysplasia syndrome has recently been recognised which results from total ablation of plakophilin 1, an intracellular desmosomal plaque protein that reinforces adhesion between the cytoskeleton and the cell membrane in terminally differentiating keratinocytes. In the future, it is likely that a number of other desmosome genodermatoses will be identified, each resulting from dominant or recessively inherited mutations in component structural proteins.

Plakophilin 3--a novel cell-type-specific desmosomal plaque protein

Desomosomes are cell-cell adhesion structures of epithelia and some non-epithelial tissues, such as heart muscle and the dendritic reticulum of lymph node follicles, which on their cytoplasmic side anchor intermediate filaments at the plasma membrane. Besides clusters of specific transmembrane glycoproteins of the cadherin family (desmogleins and desmocollins), they contain several desmosomal plaque proteins, such as desmoplakins, plakoglobin, and one or more plakophilins. Using recombinant DNA and immunological techniques, we have identified a novel desmosomal plaque protein that is closely related to plakophilins 1 and 2, both members of the "armadillo-repeat" multigene family, and have named it plakophilin 3 (PKP3). The product of the complete human cDNA defines a protein of 797 amino acids, with a calculated molecular weight of 87.081 kDa and an isoelectric point of pH 10.1. Northern blot analysis has shown that PKP3 mRNA has a size of approximately 2.9 kb and is detectable in the total RNA of cells of stratified and single-layered epithelia. With the help of specific poly- and monoclonal antibodies we have localized PKP3, by immunofluorescence or immunoelectron microscopy, to desmosomes of most simple and almost all stratified epithelia and cell lines derived therefrom, with the remarkable exception of hepatocytes and hepatocellular carcinoma cells. We have also determined the structure of the human PKP3 gene and compared it with that of plakophilin 1 (PKP1). Using fluorescence in situ hybridization, we have localized the human genes for the three known plakophilins to the chromosomes 1q32 (PKP1), 12p11 (PKP2) and 11p15 (PKP3). The similarities and differences of the diverse plakophilins are discussed.

Skin fragility and hypohidrotic ectodermal dysplasia resulting from ablation of plakophilin 1

We report a 2-year-old boy with an unusual autosomal recessively inherited skin disease comprising trauma-induced skin fragility and congenital ectodermal dysplasia affecting hair, nails and sweat glands. Skin biopsy showed widening of intercellular spaces between keratinocytes and ultrastructural findings of small, poorly formed desmosomes with reduced connections to the keratin filament cytoskeleton. Immunohistochemical analysis revealed a complete absence of staining for the accessory desmosomal plaque protein plakophilin 1 (PKP1; band 6 protein). The affected individual was a compound heterozygote for null mutations on both alleles of the PKP1 gene. Both mutations occurred within the amino terminus of PKP1, the domain which normally binds the cytoskeletal keratin filament network to the cell membrane. Apart from its localization within desmosomal plaques, PKP1 may also be present within the cytoplasm and nucleus and has putative roles in signal transduction and regulation of gene activity. The clinicopathological observations in this patient demonstrate the relevance of PKP1 to desmosome formation, cutaneous cell-cell adhesion and epidermal development and demonstrate the specific manifestations of human functional knockout mutations in this gene.

Molecular cloning of the gene for the human prostaglandin transporter hPGT: gene organization, promoter activity, and chromosomal localization

Prostaglandins (PGs) play diverse and important roles in human health and disease. We recently identified the first known PG transporter cDNA in the rat (PGT) and human (hPGT). To aid in the analysis of any possible human disease caused by mutations in PGT, we have cloned and characterized the hPGT gene. The gene exists as a single copy in the human genome and is comprised of 14 exons distributed over approximately 95 kb. Two introns disrupt putative trans-membrane spans of the coding region; each of these sites is near a highly conserved charged residue. The approximately 250 bp immediately 5' to the start of exon 1 contain a TATAAA sequence (TATA box), a transcription initiation (Inr) consensus (CTCANTCT), two Sp 1 sequences (GGGCGG), and a cAMP response element (CGGCGTCA). Ligation of approximately 3.5 kb of 5' flanking sequence to a luciferase reporter yielded > 15-fold activity above background when expressed in A549 human lung epithelial cells. PCR-based monochromosomal somatic cell hybrid mapping and fluorescence in situ hybridization localized hPGT to chromosome 3q21. Three microsatellites were identified, one of which was demonstrated to be polymorphic in unrelated individuals and may be useful in evaluating PGT as a candidate gene in human disease.

Ultrastructural localization of cell junctional components (desmoglein, plakoglobin, E-cadherin, and beta-catenin) in Hailey-Hailey disease, Darier's disease, and pemphigus vulgaris

The distribution of desmoglein, plakoglobin, E-cadherin, and beta-catenin in the peri-lesional and lesional skin of Hailey-Hailey disease, Darier's disease, and pemphigus vulgaris was examined by immunoelectron microscopy. In the peri-lesional skin, the immunolabeling of these desmosomal components was localized to desmosomes. Adherens junction-associated E-cadherin and beta-catenin were at the cell periphery, excluding desmosomes. The labeling pattern was similar among these diseases, but the labeling intensity particularly that of plakoglobin in Hailey-Hailey disease and Darier's disease, was less than that of normal controls, suggesting that these glycoproteins are quantitatively less concentrated in the normal epidermis of these inherited diseases. In the acantholytic cells of Hailey-Hailey disease and Darier's disease the immunolabeling of the components of desmosomes was diffusely distributed in the cytoplasms, whereas that of adherensjunction was mostly at the cell periphery and partly diffusely in the cytoplasm. In contrast, desmosomes of detaching keratinocytes in pemphigus vulgaris still showed the labeling of desmoglein and plakoglobin. These findings suggest that the inherited acantholytic diseases, i.e., Hailey-Hailey disease and Darier's disease have a different pathogenesis from that of autoimmune acantholysis in pemphigus vulgaris: The intracellular components of desmosomes may primarily be disrupted in the genetic acantholytic diseases in the initial stages of acantholysis. Several unsolved questions in the previous light microscopic immunofluorescence studies using the same antibodies are now answered: 1) the diffusion of desmosomal proteins is not due to the internalization of desmosomes, 2) intracellular components of adherens junction are also finally dissolved, 3) diffuse cytoplasmic immunofluorescence patterns of desmosomal components could be explained by immunoelectron microscopy as those attached to cell membrane and trapped in tonofilament aggregates.

Hailey-Hailey disease keratinocytes: normal assembly of cell-cell junctions in vitro

The blisters in the inherited disorder, Hailey-Hailey disease, may be caused by defective epidermal junctional complexes. We evaluated these structural complexes in vivo and in vitro. We induced a vesicular lesion in the apparently normal skin of a patient with Hailey-Hailey disease and studied a biopsy of this lesion by transmission electron microscopy. To determine whether acantholysis was related to a defect in the number or assembly of intercellular junctions, we cultured Hailey-Hailey disease keratinocytes in medium containing 0.1 mM Ca2+ and increased the [Ca2+] to 1.1 mM in order to induce assembly of cell-cell junctions. Keratinocytes were examined by double immunofluorescence with antibodies to the desmosome protein, desmoplakin, and the adherens junction protein, vinculin, at intervals after the increase in [Ca2+]. Characteristic Hailey-Hailey disease histopathology was observed by electron microscopy of the patient's skin after trauma, but we found no splitting of desmosomes. Based on the location, intensity, and rate of change of immunofluorescent staining, Hailey-Hailey and normal keratinocytes did not differ in their ability to assemble desmosomes and adherens junctions. Furthermore, we observed no significant morphologic differences between normal and Hailey-Hailey keratinocytes cultured in low and high [Ca2+]-containing media; Hailey-Hailey cells contained abundant normal-appearing desmosomes in 1.1 mM [Ca2+]. Since Hailey-Hailey disease keratinocytes can assemble normal-appearing adherens junctions and desmosomes in vitro, the functional defect may not lie in assembly of cell-cell adhering junctions, or additional perturbation may be required to expose the defect.

Evidence for genetic heterogeneity in monilethrix

Monilethrix is a rare inherited defect of the hair shaft resulting in hair fragility and dystrophic alopecia. In contrast to recent reports mapping monilethrix to the type II epithelial and trichocyte keratin gene cluster on 12q13, we strongly excluded these candidate genes in another family with autosomal dominant monilethrix. Moreover, there was no evidence for linkage of the disease to the keratin gene cluster on chromosome 17q12-q21, thus excluding defects in all known trichocyte and epithelial keratins as the cause of monilethrix in this family. Likewise, several other genes known to play an important role in hair shaft formation (trichohyalin and involucrin, ultra-high sulfur matrix proteins, and transglutaminases 1, 2, and 3) did not provide any evidence for linkage. Our results indicate genetic heterogeneity in monilethrix and suggest that aberrations in at least one other gene result in a similar phenotype.