Autosomal-dominant calcium ATPase disorders

ATP1A3 regulates protein synthesis for mitochondrial stability under heat stress

Pathogenic variants in ATP1A3, the gene encoding the α3 subunit of the Na+/K+-ATPase, cause alternating hemiplegia of childhood (AHC) and related disorders. Impairments in Na+/K+-ATPase activity are associated with the clinical phenotype. However, it remains unclear whether additional mechanisms are involved in the exaggerated symptoms under stressed conditions in patients with AHC. We herein report that the intracellular loop (ICL) of ATP1A3 interacted with RNA-binding proteins, such as Eif4g (encoded by Eif4g1), Pabpc1 and Fmrp (encoded by Fmr1), in mouse Neuro2a cells. Both the siRNA-mediated depletion of Atp1a3 and ectopic expression of the p.R756C variant of human ATP1A3-ICL in Neuro2a cells resulted in excessive phosphorylation of ribosomal protein S6 (encoded by Rps6) and increased susceptibility to heat stress. In agreement with these findings, induced pluripotent stem cells (iPSCs) from a patient with the p.R756C variant were more vulnerable to heat stress than control iPSCs. Neurons established from the patient-derived iPSCs showed lower calcium influxes in responses to stimulation with ATP than those in control iPSCs. These data indicate that inefficient protein synthesis contributes to the progressive and deteriorating phenotypes in patients with the p.R756C variant among a variety of ATP1A3-related disorders.

Mendelian Disorders in an Interstitial Cystitis/Bladder Pain Syndrome Cohort

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic pain disorder causing symptoms of urinary frequency, urgency, and bladder discomfort or pain. Although this condition affects a large population, little is known about its etiology. Genetic analyses of whole exome sequencing are performed on 109 individuals with IC/BPS. One family has a previously reported SIX5 variant (ENST00000317578.6:c.472G>A, p.Ala158Thr), consistent with Branchiootorenal syndrome 2 (BOR2). A likely pathogenic heterozygous variant in ATP2A2 (ENST00000539276.2:c.235G>A, p.Glu79Lys) is identified in two unrelated probands, indicating possible Darier-White disease. Two private heterozygous variants are identified in ATP2C1 (ENST00000393221.4:c.2358A>T, p.Glu786Asp (VUS/Likely Pathogenic) and ENST00000393221.4:c.989C>G, p.Thr330Ser (likely pathogenic)), indicative of Hailey-Hailey Disease. Sequence kernel association test analysis finds an increased burden of rare ATP2C1 variants in the IC/BPS cases versus a control cohort (p = 0.03, OR = 6.76), though does not survive Bonferroni correction. The data suggest that some individuals with IC/BPS may have unrecognized Mendelian syndromes. Comprehensive phenotyping and genotyping aid in understanding the range of diagnoses in the population-based IC/BPS cohort. Conversely, ATP2C1, ATP2A2, and SIX5 may be candidate genes for IC/BPS. Further evaluation with larger numbers is needed. Genetically screening individuals with IC/BPS may help diagnose and treat this painful disorder due to its heterogeneous nature.

Generalized Hailey-Hailey disease: Novel splice-site mutations of ATP2C1 gene in Chinese population and a literature review

BACKGROUND

Hailey-Hailey disease (HHD; OMIM: 169600) is an autosomal dominate genodermatosis, characterized by recurrent blisters and erosions clinically and remarkable acantholysis pathologically. The underlying pathogenic factor is the mutation of ATP2C1 gene (OMIM: 604384), which encodes secretory pathway Ca²⁺ /Mn²⁺ -ATPase (SPCA1). Skin folds are the predilection site of HHD. Atypical cases with a generalized pattern have rarely been reported, making it prone to misdiagnosis.

METHODS

In this study, we presented three Chinese pedigrees of Hailey-Hailey disease with generalized skin lesions. ATP2C1 mutations were screened by DNA sequencing and their transcripts were further confirmed by minigene assay. We also performed a literature review of previously published generalized HHD over past two decades together with our cases.

RESULTS

Three splice-site mutations were identified: c.2487+1G>A, c.2126+1G>A, and c.1891-2A>G, which resulted in an exon 25-truncated transcript, two exon 22-truncated transcripts, and two exon 21-truncated transcripts, respectively. The c.2487+1G>A and the c.1891-2A>G mutations are novel mutations which have not been reported before. No clustered mutations of ATP2C1 gene were found in generalized HHD patients in literature along with our novel mutations.

CONCLUSION

We found no hot spot mutations in ATP2C1 correlated with the generalized pattern of HHD. Our study expanded the spectrum of ATP2C1 mutations, which would be useful for disease diagnosis and genetic counseling.

SERCA is critical to control the Bowditch effect in the heart

The Bowditch effect or staircase phenomenon is the increment or reduction of contractile force when heart rate increases, defined as either a positive or negative staircase. The healthy and failing human heart both show positive or negative staircase, respectively, but the causes of these distinct cardiac responses are unclear. Different experimental approaches indicate that while the level of Ca2+ in the sarcoplasmic reticulum is critical, the molecular mechanisms are unclear. Here, we demonstrate that Drosophila melanogaster shows a negative staircase which is associated to a slight but significant frequency-dependent acceleration of relaxation (FDAR) at the highest stimulation frequencies tested. We further showed that the type of staircase is oppositely modified by two distinct SERCA mutations. The dominant conditional mutation SERCAA617T induced positive staircase and arrhythmia, while SERCAE442K accentuated the negative staircase of wild type. At the stimulation frequencies tested, no significant FDAR could be appreciated in mutant flies. The present results provide evidence that two individual mutations directly modify the type of staircase occurring within the heart and suggest an important role of SERCA in regulating the Bowditch effect.

Yeast-Based Screen to Identify Natural Compounds with a Potential Therapeutic Effect in Hailey-Hailey Disease

The term orthodisease defines human disorders in which the pathogenic gene has orthologs in model organism genomes. Yeasts have been instrumental for gaining insights into the molecular basis of many human disorders, particularly those resulting from impaired cellular metabolism. We and others have used yeasts as a model system to study the molecular basis of Hailey-Hailey disease (HHD), a human blistering skin disorder caused by haploinsufficiency of the gene ATP2C1 the orthologous of the yeast gene PMR1. We observed that K. lactis cells defective for PMR1 gene share several biological similarities with HHD derived keratinocytes. Based on the conservation of ATP2C1/PMR1 function from yeast to human, here we used a yeast-based assay to screen for molecules able to influence the pleiotropy associated with PMR1 deletion. We identified six compounds, Kaempferol, Indirubin, Lappaconite, Cyclocytidine, Azomycin and Nalidixic Acid that induced different major shape phenotypes in K. lactis. These include mitochondrial and the cell-wall morphology-related phenotypes. Interestingly, a secondary assay in mammalian cells confirmed activity for Kaempferol. Indeed, this compound was also active on human keratinocytes depleted of ATP2C1 function by siRNA-treatment used as an in-vitro model of HHD. We found that Kaempferol was a potent NRF2 regulator, strongly inducing its expression and its downstream target NQO1. In addition, Kaempferol could decrease oxidative stress of ATP2C1 defective keratinocytes, characterized by reduced NRF2-expression. Our results indicated that the activation of these pathways might provide protection to the HHD-skin cells. As oxidative stress plays pivotal roles in promoting the skin lesions of Hailey-Hailey, the NRF2 pathway could be a viable therapeutic target for HHD.

Non-Desmoglein Antibodies in Patients With Pemphigus Vulgaris

Pemphigus vulgaris (PV) is a potentially life-threatening mucocutaneous autoimmune blistering disease. Patients develop non-healing erosions and blisters due to cell–cell detachment of keratinocytes (acantholysis), with subsequent suprabasal intraepidermal splitting. Identified almost 30 years ago, desmoglein-3 (Dsg3), a Ca²⁺-dependent cell adhesion molecule belonging to the cadherin family, has been considered the “primary” autoantigen in PV. Proteomic studies have identified numerous autoantibodies in patients with PV that have known roles in the physiology and cell adhesion of keratinocytes. Antibodies to these autoantibodies include desmocollins 1 and 3, several muscarinic and nicotinic acetylcholine receptor subtypes, mitochondrial proteins, human leukocyte antigen molecules, thyroid peroxidase, and hSPCA1—the Ca²⁺/Mn²⁺-ATPase encoded by ATP2C1, which is mutated in Hailey–Hailey disease. Several studies have identified direct pathogenic roles of these proteins, or synergistic roles when combined with Dsg3. We review the role of these direct and indirect mechanisms of non-desmoglein autoantibodies in the pathogenesis of PV.

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.

Bullous, pseudobullous, & pustular dermatoses

Several dermatoses are typified by the formation of spaces (blisters; bullae) within or beneath the epidermis. These may be acellular or filled with particular species of inflammatory cells. Etiological categories include infectious, immune-mediated, genetic, drug-related, and idiopathic lesions. Examples of such disorders include impetigo, Herpes virus infections, pemphigus, bullous pemphigoid and pemphigoid gestationis, epidermolysis bullosa acquisita, IgA-related dermatoses, inherited epidermolysis bullosa variants, Hailey-Hailey disease, and porphyria cutanea tarda. Other conditions manifest microscopic acantholysis within the surface epithelium but are not associated with clinical bullae, such as Darier disease and Grover disease. Finally, both infectious and non-infectious causes exist for the development of neutrophilic pustules in the epidermis, as seen in pustular psoriasis, Sneddon-Wilkinson disease (subcorneal pustular dermatosis), and acute generalized exanthematous pustulosis. This review considers the clinical and histological features of all of these diseases.

A Bullous Flare of a Hyperkeratotic Affair: A Case Report

BACKGROUND

Darier's disease is an autosomal dominant genodermatosis typified by hyperkeratotic papules and plaques in a predominately seborrheic distribution. The vesiculo-bullous variant of Darier's disease is rare. Several previously reported cases have demonstrated clinical and microscopic features resembling familial benign chronic pemphigus or Hailey-Hailey disease.

OBJECTIVES

The objective of this report is to describe an uncommon presentation of Darier's disease, which has been infrequently described in the literature.

METHODS

The authors present a case of bullous flare of long-standing Darier's disease.

CONCLUSIONS

Darier's disease may assume several atypical morphologies, including vesiculo-bullous lesions.

A family with atypical Hailey Hailey disease--is there more to the underlying genetics than ATP2C1?

The autosomal dominant Hailey Hailey disease (HHD) is caused by mutations in the ATP2C1 gene encoding for human secretory pathway Ca2+/Mn2+ ATPase protein (hSPCA1) in the Golgi apparatus. Clinically, HHD presents with erosions and hyperkeratosis predominantly in the intertrigines. Here we report an exome next generation sequencing (NGS) based analysis of ATPase genes in a Greek family with 3 HHD patients presenting with clinically atypical lesions mainly localized on the neck and shoulders. By NGS of one HHD-patient and in silico SNP calling and SNP filtering we identified a SNP in the expected ATP2C1 gene and SNPs in further ATPase genes. Verification in all 3 affected family members revealed a heterozygous frameshift deletion at position 2355_2358 in exon 24 of ATP2C1 in all three patients. 7 additional SNPs in 4 ATPase genes (ATP9B, ATP11A, ATP2B3 and ATP13A5) were identified. The SNPs rs138177421 in the ATP9B gene and rs2280268 in the ATP13A5 gene were detected in all 3 affected, but not in 2 non affected family members. The SNPs in the ATP2B3 and ATP11A gene as well as further SNPs in the ATP13A5 gene could not be confirmed in all affected family members. One may speculate that besides the level of functional hSPCA1 protein, levels of other ATPase proteins may influence expressivity of the disease and might also contribute, as in this case, to atypical presentations.

Efficacy of magnesium chloride in the treatment of Hailey-Hailey disease: from serendipity to evidence of its effect on intracellular Ca(2+) homeostasis

BACKGROUND

Hailey-Hailey disease (HHD), also known as familial benign chronic pemphigus, is a rare autosomal dominant inherited intraepidermal blistering genodermatosis. Mutations in the ATP2C1 gene encoding for the Golgi secretory pathway Ca(2+) /Mn(2+) -ATPasi protein 1 (SPCA1) affect the processing of desmosomal components and the epidermal suprabasal cell-cell adhesion by deregulating the keratinocyte cytosolic Ca(2+) concentration. We report the unexpected, dramatic, and persistent clinical improvement of the skin lesions of a patient affected with longstanding HHD with daily intake of a solution containing magnesium chloride hexahydrate (MgCl2 ).

MATERIALS AND METHODS

We investigated the effect of MgCl2 on the intracellular Ca(2+) homeostasis and on the activity of particular Ca(2+) -effectors in HeLa cells transfected with chimeric aequorins (cytAEQ, mtAEQ, erAEQ and GoAEQ) targeted to different subcellular compartments (cytosol, mitochondria, endoplasmic reticulum, and Golgi, respectively).

RESULTS

Experimental investigations on HeLa cells showed the effect of MgCl2 on the function of Ca(2+) -extrusor systems, resulting in increased cytosolic and mitochondrial Ca(2+) levels, without altering the mechanisms of intraluminal Ca(2+) -filling and Ca(2+) -release of stores.

CONCLUSIONS

Based on our clinical observation and experimental results, it can be hypothesized that MgCl2 could act as an inhibitor of the Ca(2+) -extruding activity in keratinocytes favoring intracellular Ca(2+) -disponibility and Ca(2+) -dependent mechanisms in desmosome assembly. This may represent the molecular basis of the good response of the HHD clinical features with MgCl2 solution in the patient described.

Acrokeratosis verruciformis of Hopf showing P602L mutation in ATP2A2 and overlapping histopathological features with Darier disease

The relationship between acrokeratosis verruciformis (AKV) of Hopf and Darier disease (DD) has been debated for several decades. Both diseases are now thought to result from mutations in the same gene, that is, the ATP2A2 gene encoding the sarco (endo) plasmic reticulum Ca ATPase2 pump (SERCA2), although their histopathological features are different. We sought to detect possible overlapping histopathological features between AKV and DD. Fourteen members of a family affected by AKV were analyzed for the underlying molecular genetic derangement, and 3 cases were studied histopathologically using multiple step sections. A heterozygous P602L mutation in ATP2A2 was identified as the underlying cause in this family. This mutation and a heterozygous A698V were previously described in AKV. Both mutations were not among the 162 mutations in ATP2A2, which were reported to date in DD. The histopathological study demonstrated in several consecutive step sections of 2 of the 3 studied cases, foci of small suprabasal clefts with acantholytic keratinocytes, some of which were mildly dyskeratotic. These focal features were reminiscent of the basic histopathological characteristics of DD. These shared histopathological features of AKV with DD suggest that AKV and DD are allelic disorders with variable expression of the same disease, although identical mutations in ATP2A2 in AKV and DD were not reported to date.

Detection and comparison of two types of ATP2C1 gene mutations in Chinese patients with Hailey-Hailey disease

The gene ATP2C1 is identified as the defective gene in Hailey-Hailey disease (HHD). The nonsense and missense are two common types of mutations and have, respectively, been detected in many HHD patients. The aims of our study were to identify the pathogenic ATP2C1 abnormality in Chinese HHD patients, and to compare nonsense and missense mutations in vivo to provide further understanding of the molecular and the physiological basis of HHD. The nucleotide sequencing of the ATP2C1 gene was performed in HHD patients, unaffected family members and 100 unrelated individuals. Meanwhile, we detected and analyzed the clinical manifestations, the expression of ATP2C1 mRNA and hSPCA1 protein in the two types of mutations. Three heterozygous mutations were identified, including a previously reported nonsense mutation (R799X), two novel missense mutations (D644G) and (R417K). The results of comparisons between two types of mutations showed that the common clinical features, the similarly low-level expressions of ATP2C1 mRNA and hSPCA1 protein, but the ATP2C1 mRNA expression of nonsense mutation was lower than missense mutation and even less than half the level of normal people. Our findings expand the known spectrum of ATP2C1 mutations in HHD. We supported the haploinsufficiency theory as prevalent mechanism in both types of mutations, and believed that the differences of ATP2C1 mRNA expressions in peripheral blood may relate with the type of mutation and reflect the state of illness of patients.

A systematic approach to systemic contact dermatitis and symmetric drug-related intertriginous and flexural exanthema (SDRIFE): a closer look at these conditions and an approach to intertriginous eruptions

Systemic contact dermatitis is a condition that occurs when an individual sensitized to a contact allergen is exposed to that same allergen or a cross-reacting molecule through a systemic route. Systemic exposure to allergens can include transcutaneous, transmucosal, oral, intravenous, intramuscular, and inhalational routes. Baboon syndrome is perhaps the most recognizable form of systemic contact dermatitis, presenting with diffuse, well demarcated erythema of the buttocks, upper inner thighs, and axillae. Other forms of systemic contact dermatitis include dermatitis at sites of previous exposure to the allergen such as at a previous site of dermatitis or at sites of previous positive patch tests, dyshidrotic hand eczema, flexural dermatitis, exanthematous rash, erythroderma, and vasculitis-like lesions. The most common causes of systemic contact dermatitis consist of three groups of allergens: (i) metals including mercury, nickel, and gold; (ii) medications including aminoglycoside antibacterials, corticosteroids, and aminophylline; and (iii) plants and herbal products including the Compositae and Anacardiaceae plant families and Balsam of Peru. Baboon syndrome caused by systemic medications without a known history of previous cutaneous sensitization in the patient has been termed drug-related baboon syndrome (DRBS) or symmetric drug-related intertriginous and flexural exanthema (SDRIFE). Criteria for SDRIFE include exposure to systemic drug at first or repeated dose, erythema of the gluteal/perianal area and/or V-shaped erythema of the inguinal area, involvement of at least one other intertriginous localization, symmetry of affected areas, and absence of systemic toxicity. The most common causes are aminopenicillins, β-lactam antibacterials, and certain chemotherapeutic agents, though the list of etiologic agents continues to grow. Baboon syndrome and SDRIFE should be strongly considered in a patient presenting with a symmetric intertriginous eruption involving multiple body folds. With the knowledge of the most frequent causes of these conditions, a detailed history and review of exposures will guide the clinician in the search for the most likely etiologic agent.

Secretory pathway stress responses as possible mechanisms of disease involving Golgi Ca2+ pump dysfunction

In mammalian tissues, uptake of Ca(2+) and Mn(2+) by Golgi membranes is mediated by the secretory pathway Ca(2+) -ATPases, SPCA1 and SPCA2, encoded by the ATP2C1 and ATP2C2 genes. Loss of one copy of the ATP2C1 gene, which causes SPCA1 haploinsufficiency, leads to squamous cell tumors of keratinized epithelia in mice and to Hailey-Hailey disease, an acantholytic skin disease, in humans. Although the disease phenotypes resulting from SPCA1 haploinsufficiency in mice and humans are quite different, each species-specific phenotype is remarkably similar to those arising as a result of null mutations in one copy of the ATP2A2 gene, encoding SERCA2, the endoplasmic reticulum (ER) Ca(2+) pump. SERCA2 haploinsufficiency, like SPCA1 haploinsufficiency, causes squamous cell tumors in mice and Darier's disease, also an acantholytic skin disease, in humans. The phenotypic similarities between SPCA1 and SERCA2 haploinsufficiency in the two species, and the general functions of the two pumps in consecutive compartments of the secretory pathway, suggest that the underlying disease mechanisms are similar. In this review, we discuss evidence supporting the view that chronic Golgi stress and/or ER stress resulting from Ca(2+) pump haploinsufficiencies leads to activation of cellular stress responses in keratinocytes, with the predominance of proapoptotic pathways (although not necessarily apoptosis itself) leading to acantholytic skin disease in humans and the predominance of prosurvival pathways leading to tumors in mice.

Tissue nonspecific alkaline phosphatase is activated via a two-step mechanism by zinc transport complexes in the early secretory pathway

A number of enzymes become functional by binding to zinc during their journey through the early secretory pathway. The zinc transporters (ZnTs) located there play important roles in this step. We have previously shown that two zinc transport complexes, ZnT5/ZnT6 heterodimers and ZnT7 homo-oligomers, are required for the activation of alkaline phosphatases, by converting them from the apo- to the holo-form. Here, we investigated the molecular mechanisms of this activation. ZnT1 and ZnT4 expressed in chicken DT40 cells did not contribute to the activation of tissue nonspecific alkaline phosphatase (TNAP). The reduced activity of TNAP in DT40 cells deficient in both ZnT complexes was not restored by zinc supplementation nor by exogenous expression of other ZnTs that increase the zinc content in the secretory pathway. Moreover, we showed that expression of ZnT5/ZnT6 heterodimers reconstituted with zinc transport-incompetent ZnT5 mutant failed to restore TNAP activity but could stabilize the TNAP protein as the apo-form, regardless of zinc status. These findings demonstrate that TNAP is activated not simply by passive zinc binding but by an elaborate two-step mechanism via protein stabilization followed by enzyme conversion from the apo- to the holo-form with zinc loaded by ZnT complexes in the early secretory pathway.

A novel missense mutation of the ATP2C1 gene in a Chinese patient with Hailey-Hailey disease

Benign familial chronic pemphigus (Hailey-Hailey disease, HHD; MIM 169600) is a rare autosomal dominant hereditary disorder characterized by pruritic vesicles, painful erosions and scaly erythematous plaques at the sites of friction and flexures. Mutations in ATP2C1, which encoding the human secretory pathway Ca²(+)/Mn²(+)-ATPase protein 1 (hSPCA1), have been identified as the pathogenic gene of HHD. We found a novel, distinct, heterozygous mutation during study of a Chinese patient with HHD. We identified a C→T transition at nucleotide 1235 (p.Thr352IIe), in exon 13 of ATP2C1. This observation would be useful for genetic counseling and prenatal diagnosis for affected families and in expanding the repertoire of ATP2C1 mutations underlying HHD.

The remarkable capacity for gut microbial and host interactions

The stunning complexity of the resident microbiota and the intricate pathways of microbial and host interactions provide a massive adaptive capacity for mammals. In this addendum we reflect on our recent publication on Toll-like receptor 2 deficiency related colonic mucosal epigenetic, immunologic and microbiomic changes. Our findings underscored the tremendous flexibility of the gut and its microbiota. This flexibility can provide means to overcome significant environmental or genetic challenges. In the meantime, the challenged intestinal system may become vulnerable to otherwise tolerable insults. In such instances, the fine-tuned mutualistic balance between the gut and its microflora may collapse leading to dysbiosis and disease. The ultimate challenge for biomedical research in these cases is to find optimal means for the restoration and maintenance of healthy host physiology.

Golgi calcium pump secretory pathway calcium ATPase 1 (SPCA1) is a key regulator of insulin-like growth factor receptor (IGF1R) processing in the basal-like breast cancer cell line MDA-MB-231

Calcium signaling is a key regulator of pathways important in tumor progression, such as proliferation and apoptosis. Most studies assessing altered calcium homeostasis in cancer cells have focused on alterations mediated through changes in cytoplasmic free calcium levels. Here, we show that basal-like breast cancers are characterized by an alteration in the secretory pathway calcium ATPase 1 (SPCA1), a calcium pump localized to the Golgi. Inhibition of SPCA1 in MDA-MB-231 cells produced pronounced changes in cell proliferation and morphology in three-dimensional culture, without alterations in sensitivity to endoplasmic reticulum stress induction or changes in global calcium signaling. Instead, the effects of SPCA1 inhibition in MDA-MB-231 cells reside in altered regulation of calcium-dependent enzymes located in the secretory pathway, such as proprotein convertases. Inhibition of SPCA1 produced a pronounced alteration in the processing of insulin-like growth factor receptor (IGF1R), with significantly reduced levels of functional IGF1Rβ and accumulation of the inactive trans-Golgi network pro-IGF1R form. These studies identify for the first time a calcium transporter associated with the basal-like breast cancer subtype. The pronounced effects of SPCA1 inhibition on the processing of IGF1R in MDA-MB-231 cells independent of alterations in global calcium signaling also demonstrate that some calcium transporters can regulate the processing of proteins important in tumor progression without major alterations in cytosolic calcium signaling. Inhibitors of SPCA1 may offer an alternative strategy to direct inhibitors of IGF1R and attenuate the processing of other proprotein convertase substrates important in basal breast cancers.

Genetic diagnosis of Hailey-Hailey disease in two Chinese families: novel mutations in the ATP2C1 gene

Hailey-Hailey disease (HHD; OMIM 169600), is an autosomal dominantly inherited disorder characterized by suprabasal cell separation of the epidermis. Mutations in ATP2C1, which encodes the human secretory pathway Ca(2+)/ Mn(2) +/- ATPase protein 1 (hSPCA1), have been identified as the pathogenic gene of HHD without evidence of genetic heterogeneity. In this study, the ATP2C1 gene was screened in two typical Chinese pedigrees with HHD, and two specific novel mutations of the ATP2CL gene were identified. Family 1 had a 16-base deletion mutation c.1068-1083del16 and family 2 had a substitution mutation c.1982T>G (p.Met661Arg). DNA sequencing of the three descendants of the probands revealed that they all had the normal genotype, indicating that there had been no transmission of the mutation.

Darier disease, multiple bone cysts, and aniridia due to double de novo heterozygous mutations in ATP2A2 and PAX6

Darier disease (DD) is an autosomal dominant genodermatosis caused by mutations in ATP2A2 and characterized by multiple warty papules coalescing in seborrheic areas and specific histological skin changes. Rare patients are described with variable bone involvement, but this association has never been sufficiently emphasized. Aniridia is a developmental disorder of the eye due to heterozygous mutations in PAX6. DD and aniridia are Mendelian traits mapping on independent loci and have never been reported in association. Here, we describe a 14-year-old girl showing the unique combination of DD, multiple bone cysts, and bilateral aniridia. Molecular investigations demonstrated that such a complex phenotype is due to double de novo heterozygous mutations in ATP2A2 and PAX6. Review of the literature indicates that, in DD, bone cysts are true developmental abnormalities of the skeleton. This finding suggests a role for ATP2A2 in bone biology. More systematic studies are expected in order to estimate the true prevalence of bone cysts in DD and the relationship between skeletal changes and ATP2A2 perturbation.