ATP2A2 mutations in Darier's disease: variant cutaneous phenotypes are associated with missense mutations, but neuropsychiatric features are independent of mutation class

Differential Analysis of Gly211Val and Gly286Val Mutations Affecting Sarco(endo)plasmic Reticulum Ca2+-ATPase (SERCA1) in Congenital Pseudomyotonia Romagnola Cattle

Congenital pseudomyotonia in cattle (PMT) is a rare skeletal muscle disorder, clinically characterized by stiffness and by delayed muscle relaxation after exercise. Muscle relaxation impairment is due to defective content of the Sarco(endo)plasmic Reticulum Ca²⁺ ATPase isoform 1 (SERCA1) protein, caused by missense mutations in the ATP2A1 gene. PMT represents the only mammalian model of human Brody myopathy. In the Romagnola breed, two missense variants occurring in the same allele were described, leading to Gly211Val and Gly286Val (G211V/G286V) substitutions. In this study, we analyzed the consequences of G211V and G286V mutations. Results support that the reduced amount of SERCA1 is a consequence of the G211V mutation, the G286V mutation almost being benign and the ubiquitin–proteasome system (UPS) being involved. After blocking the proteasome using a proteasome inhibitor, we found that the G211V mutant accumulates in cells at levels comparable to those of WT SERCA1. Our conclusion is that G211/286V mutations presumably originate in a folding-defective SERCA1 protein, recognized and diverted to degradation by UPS, although still catalytically functional, and that the main role is played by G211V mutation. Rescue of mutated SERCA1 to the sarcoplasmic reticulum membrane can re-establish resting cytosolic Ca²⁺ concentration and prevent the appearance of pathological signs, paving the way for a possible therapeutic approach against Brody disease.

Whole-transcriptome sequencing identifies postzygotic ATP2A2 mutations in a patient misdiagnosed with herpes zoster, confirming the diagnosis of very late-onset segmental Darier disease

An 82-year-old female patient presented with a recent onset of painful skin lesions in unilateral distribution on the abdominal area following the lines of Blaschko; the initial diagnosis of Varicella-zoster infection was made. However, because the individual lesions appeared as hyperkeratotic papules and were unresponsive to antiviral therapy, a skin biopsy was performed, which revealed hyperkeratosis, suprabasal acantholysis and dyskeratosis with corps ronds and grains, consistent with acantholytic dyskeratotic acanthoma. Since this entity has been associated with Darier disease, whole transcriptome sequencing by RNA-Seq was performed on RNA isolated from a lesion as well as from adjacent normal appearing skin, and a recently developed bioinformatics pipeline that can identify both genomic sequence variants and the presence of any of over 900 viruses was applied. Two pathogenic missense mutations in the ATP2A2 gene were identified in the lesional but not in normal appearing skin, and no evidence of Varicella-Zoster infection was obtained. These findings confirm the diagnosis of segmental Darier disease due to postzygotic mutations in the ATP2A2 gene, and attest to the power of a novel single-step application of RNA-Seq in providing correct diagnosis in this rare genodermatosis.

Chromosomal Microarray Analysis as First-Tier Genetic Test for Schizophrenia

Schizophrenia is a chronic, devastating mental disorder with complex genetic components. Given the advancements in the molecular genetic research of schizophrenia in recent years, there is still a lack of genetic tests that can be used in clinical settings. Chromosomal microarray analysis (CMA) has been used as first-tier genetic testing for congenital abnormalities, developmental delay, and autism spectrum disorders. This study attempted to gain some experience in applying chromosomal microarray analysis as a first-tier genetic test for patients with schizophrenia. We consecutively enrolled patients with schizophrenia spectrum disorder from a clinical setting and conducted genome-wide copy number variation (CNV) analysis using a chromosomal microarray platform. We followed the 2020 “Technical Standards for the interpretation and reporting of constitutional copy-number variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics (ACMG) and the Clinical Genome Resource (ClinGen)” to interpret the clinical significance of CNVs detected from patients. We recruited a total of 60 patients (36 females and 24 males) into this study. We detected three pathogenic CNVs and one likely pathogenic CNV in four patients, respectively. The detection rate was 6.7% (4/60, 95% CI: 0.004–0.13), comparable with previous studies in the literature. Also, we detected thirteen CNVs classified as uncertain clinical significance in nine patients. Detecting these CNVs can help establish the molecular genetic diagnosis of schizophrenia patients and provide helpful information for genetic counseling and clinical management. Also, it can increase our understanding of the pathogenesis of schizophrenia. Hence, we suggest CMA is a valuable genetic tool and considered first-tier genetic testing for schizophrenia spectrum disorders in clinical settings.

Brain-specific heterozygous loss-of-function of ATP2A2, endoplasmic reticulum Ca2+ pump responsible for Darier's disease, causes behavioral abnormalities and a hyper-dopaminergic state

A report of a family of Darier's disease with mood disorders drew attention when the causative gene was identified as ATP2A2 (or SERCA2), which encodes a Ca2+ pump on the endoplasmic reticulum (ER) membrane and is important for intracellular Ca2+ signaling. Recently, it was found that loss-of-function mutations of ATP2A2 confer a risk of neuropsychiatric disorders including depression, bipolar disorder and schizophrenia. In addition, a genome-wide association study found an association between ATP2A2 and schizophrenia. However, the mechanism of how ATP2A2 contributes to vulnerability to these mental disorders is unknown. Here, we analyzed Atp2a2 heterozygous brain-specific conditional knockout (hetero cKO) mice. The ER membranes prepared from the hetero cKO mouse brain showed decreased Ca2+ uptake activity. In Atp2a2 heterozygous neurons, decays of cytosolic Ca2+ level were slower than control neurons after depolarization. The hetero cKO mice showed altered behavioral responses to novel environments and impairments in fear memory, suggestive of enhanced dopamine signaling. In vivo dialysis demonstrated that extracellular dopamine levels in the NAc were indeed higher in the hetero cKO mice. These results altogether indicate that the haploinsufficiency of Atp2a2 in the brain causes prolonged cytosolic Ca2+ transients, which possibly results in enhanced dopamine signaling, a common feature of mood disorders and schizophrenia. These findings elucidate how ATP2A2 mutations causing a dermatological disease may exert their pleiotropic effects on the brain and confer a risk for mental disorders.

Novel Mannich base 3FB3FA8H induces apoptosis by upregulating P53 pathway in neuroblastoma cells

P53 plays an important role in maintaining genetic stability and development of resistance against tumors. Dysregulation of P53 gene is one of the key factors contributing to the etiology of neuroblastoma which causes cells to evade apoptosis. Activating P53 pathway can be a therapeutic alternative to the currently available medicinal strategies. Mannich bases have been known to possess various biological activities including the anticancer activity. In this study, we have targeted the P53 pathway by novel Mannich base (3FB3FA8H) which can be a future prospect to cure neuroblastoma. 3FB3FA8H has shown modulation of P53 pathway leading to apoptosis of neuroblastoma cells. Mitochondrial membrane permeability is also increased by 3FB3FA8H which may be a consequence of P53 pathway modulation. 3FB3FA8H increases the mRNA levels of P53 leading to activation of BAX. Inclining BAX/BCL2 ratio towards apoptotic BAX leads to cleavage of caspase 3, ultimately, causing apoptosis. Series of experiments provide the evidence that Mannich base 3FB3FA8H leads to P53-mediated apoptosis. Inducing apoptosis by this mechanism could be of central importance in reducing tumor burden which can be a good prospect for neuroblastoma patients.

Structures of the heart specific SERCA2a Ca2+-ATPase

The sarcoplasmic/endoplasmic reticulum Ca²⁺-ATPase 2a (SERCA2a) performs active reuptake of cytoplasmic Ca²⁺ and is a major regulator of cardiac muscle contractility. Dysfunction or dysregulation of SERCA2a is associated with heart failure, while restoring its function is considered as a therapeutic strategy to restore cardiac performance. However, its structure has not yet been determined. Based on native, active protein purified from pig ventricular muscle, we present the first crystal structures of SERCA2a, determined in the CPA-stabilized E2-AlF4- form (3.3 Å) and the Ca²⁺-occluded [Ca₂]E1-AMPPCP form (4.0 Å). The structures are similar to the skeletal muscle isoform SERCA1a pointing to a conserved mechanism. We seek to explain the kinetic differences between SERCA1a and SERCA2a. We find that several isoform-specific residues are acceptor sites for post-translational modifications. In addition, molecular dynamics simulations predict that isoform-specific residues support distinct intramolecular interactions in SERCA2a and SERCA1a. Our experimental observations further indicate that isoform-specific intramolecular interactions are functionally relevant, and may explain the kinetic differences between SERCA2a and SERCA1a.

Genotype-phenotype correlations in Darier disease: A focus on the neuropsychiatric phenotype

Darier disease (DD) is an autosomal dominant skin disorder caused by mutations in ATP2A2 encoding the sarco/endoplasmic reticulum Ca²⁺ ATPase Isoform 2 (SERCA2). Evidence of a population-level association between DD and psychiatric disorders suggests that mutations in ATP2A2 may have pleiotropic effects on the brain as well as skin. Evidence of genotype-phenotype relationships between ATP2A2 mutations and neuropsychiatric phenotypes would further support this suggestion. We investigated genotype-phenotype correlations between lifetime neuropsychiatric features and ATP2A2 mutation type (dichotomized into likely gene disrupting [LGD] or protein altering) in 75 unrelated individuals with DD. We also looked for evidence of clustering of mutations within SERCA2 according to neuropsychiatric features. Combining our data with the existing literature, the rate of LGD mutations was found to be significantly higher among DD cases/families with bipolar disorder, schizophrenia, or affective psychosis (p = .011). We also found a significant relationship between mutations located in the S4-M4 region of the protein and the presence of a severe neuropsychiatric phenotype (p = .032). Our findings add support to the hypothesis that Darier-causing mutations in ATP2A2 confer susceptibility to neuropsychiatric dysfunction, in particular severe psychiatric illness. This, together with evidence from research on common polymorphisms confirms ATP2A2 as a gene at which variation influences susceptibility to major psychiatric illness.

Underexpression of α-1-microglobulin/bikunin precursor predicts a poor prognosis in oral squamous cell carcinoma

In the present study, in order to identify novel diagnostic biomarkers for the malignant behavior of oral squamous cell carcinoma (OSCC), we determined the proteomic profiles of several OSCC cell lines and keratinocytes by two-dimensional fluorescence difference gel electrophoresis and liquid chromatography tandem mass spectrometry. The protein expression level of α-1-microglobulin/bikunin precursor (AMBP) was found to be significantly lower in the OSCC cell lines than in the keratinocytes, and a significant decrease in AMBP mRNA expression was confirmed in the OSCC cell lines by RT-qPCR. To investigate the biological function of AMBP in OSCC, the cells were transiently transfected with an AMBP overexpression vector; the AMBP-overexpressing cells exhibited a significantly decreased invasion and migration in comparison to the mock-transfected control cells, although no significant changes in cell proliferation were observed. Immunohistochemistry revealed that the underexpression of AMBP was significantly associated with a high metastatic potential to cervical lymph nodes and a poor overall survival. Thus, the expression of AMBP is an independent predictive factor of cervical lymph node metastasis and a prognostic factor of overall survival, and it is involved in both cell invasion and metastasis in cervical lymph nodes in OSCC.

Novel mutations in Darier disease and association to self-reported disease severity

Darier disease is a rare and severe autosomal dominant skin disease characterised by malodorous keratotic papules in seborrheic areas of the skin. Darier disease affects up to 1 in 30 000 people and is caused by mutations in the ATP2A2 gene, which encodes to the sarco/endoplasmic reticulum calcium-ATPase isoform 2 that pumps calcium into the endoplasmic reticulum. Although many ATP2A2 variants have been described, it is not known if genotype correlates with phenotype, which could be important for prognosis and treatment. This is the first study to use whole exome sequencing to screen the ATP2A2 gene in a cohort of 28 clinically diagnosed Darier disease patients. Twenty-one different disease causing variants were identified and 15 of these were novel. Sixteen of the 21 variants were predicted to be pathogenic using in silico prediction programs. There were seven missense, four intronic/splice-sites, three frameshifts, two in-frame deletions, four nonsense and one synonymous mutations. This study also found ten patients who harbour more than one ATP2A2 variant. The phenotype of the patient cohort was assessed by photography and by patient questionnaires. The genotype-phenotype association was examined for all variants in relation to the patient's disease severity score, and no correlation could be established.

The Ca2+-ATPase pump facilitates bidirectional proton transport across the sarco/endoplasmic reticulum

Ca²⁺ transport across the sarco/endoplasmic reticulum (SR) plays an essential role in intracellular Ca²⁺ homeostasis, signalling, cell differentiation and muscle contractility. During SR Ca²⁺ uptake and release, proton fluxes are required to balance the charge deficit generated by the exchange of Ca²⁺ and other ions across the SR. During Ca²⁺ uptake by the SR Ca²⁺-ATPase (SERCA), two protons are countertransported from the SR lumen to the cytosol, thus partially compensating for the charge moved by Ca²⁺ transport. Studies have shown that protons are also transported from the cytosol to the lumen during Ca²⁺ release, but a transporter that facilitates proton transport into the SR lumen has not been described. In this article we propose that SERCA forms pores that facilitate bidirectional proton transport across the SR. We describe the location and structure of water-filled pores in SERCA that form cytosolic and luminal pathways for protons to cross the SR membrane. Based on this structural information, we suggest mechanistic models for proton translocation to the cytosol during active Ca²⁺ transport, and into the SR lumen during SERCA inhibition by endogenous regulatory proteins. Finally, we discuss the physiological consequences of SERCA-mediated bidirectional proton transport across the SR membrane of muscle and non-muscle cells.

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.

ER-luminal thiol/selenol-mediated regulation of Ca2+ signalling

The endoplasmic reticulum (ER) is the main cellular Ca(2+)storage unit. Among other signalling outputs, the ER can release Ca(2+)ions, which can, for instance, communicate the status of ER protein folding to the cytosol and to other organelles, in particular the mitochondria. As a consequence, ER Ca(2+)flux can alter the apposition of the ER with mitochondria, influence mitochondrial ATP production or trigger apoptosis. All aspects of ER Ca(2+)flux have emerged as processes that are intimately controlled by intracellular redox conditions. In this review, we focus on ER-luminal redox-driven regulation of Ca(2+)flux. This involves the direct reduction of disulfides within ER Ca(2+)handling proteins themselves, but also the regulated interaction of ER chaperones and oxidoreductases such as calnexin or ERp57 with them. Well-characterized examples are the activating interactions of Ero1α with inositol 1,4,5-trisphosphate receptors (IP3Rs) or of selenoprotein N (SEPN1) with sarco/endoplasmic reticulum Ca(2+)transport ATPase 2 (SERCA2). The future discovery of novel ER-luminal modulators of Ca(2+)handling proteins is likely. Based on the currently available information, we describe how the variable ER redox conditions govern Ca(2+)flux from the ER.

Redox-assisted regulation of Ca2+ homeostasis in the endoplasmic reticulum by disulfide reductase ERdj5

Calcium ion (Ca²⁺) is an important second messenger that regulates numerous cellular functions. Intracellular Ca²⁺ concentration ([Ca²⁺]i) is strictly controlled by Ca²⁺ channels and pumps on the endoplasmic reticulum (ER) and plasma membranes. The ER calcium pump, sarco/endoplasmic reticulum calcium ATPase (SERCA), imports Ca²⁺ from the cytosol into the ER in an ATPase activity-dependent manner. The activity of SERCA2b, the ubiquitous isoform of SERCA, is negatively regulated by disulfide bond formation between two luminal cysteines. Here, we show that ERdj5, a mammalian ER disulfide reductase, which we reported to be involved in the ER-associated degradation of misfolded proteins, activates the pump function of SERCA2b by reducing its luminal disulfide bond. Notably, ERdj5 activated SERCA2b at a lower ER luminal [Ca²⁺] ([Ca²⁺]_ER), whereas a higher [Ca²⁺]_ER induced ERdj5 to form oligomers that were no longer able to interact with the pump, suggesting [Ca²⁺]_ER-dependent regulation. Binding Ig protein, an ER-resident molecular chaperone, exerted a regulatory role in the oligomerization by binding to the J domain of ERdj5. These results identify ERdj5 as one of the master regulators of ER calcium homeostasis and thus shed light on the importance of cross talk among redox, Ca²⁺, and protein homeostasis in the ER.

Loss of function mutations in ATP2A2 and psychoses: A case report and literature survey

AIM

Though genetic factors play a major role in the pathophysiology of psychoses including bipolar disorder (BD) and schizophrenia, lack of well-established causative genetic mutations hampers their neurobiological studies. Darier's disease, an autosomal dominant skin disorder caused by mutations of ATP2A2 on chromosome 12q23-24.1, encoding sarco/endoplasmic reticulum calcium transporting ATPase 2 (SERCA2), reportedly cosegregates with BD. A recent genome-wide association study showed an association of schizophrenia with ATP2A2.

METHODS

We sequenced all coding regions of ATP2A2 in a newly identified patient with Darier's disease and BD. In addition, we performed a literature survey to examine whether likely gene disrupting (LGD) mutations are related to psychoses.

RESULTS

We identified a rare heterozygous mutation, c.1288-6A>G, at the 3' end of intron 10 in the patient. A minigene splicing assay showed that this mutation introduces a new splice site causing a frameshift and premature stop codon. A literature survey of case reports of patients with Darier's disease and psychoses revealed that the rate of LGD mutations causing frameshift, altered splicing, gain of stop codon, or loss of start codon was significantly higher among the mutations harbored by these cases (9 of 11) than that of ATP2A2 mutations for which comorbidity of psychosis was not reported (107 of 237, P = 0.026). The only non-LGD mutation (p.C560R) reported in patients with Darier's disease and BD caused decreased ATP2A2 protein expression.

CONCLUSION

These results suggest that psychoses in Darier's disease may be caused by a pleiotropic effect of loss-of-function mutations of ATP2A2.

Intellectual disability and cognitive ability in Darier disease: Swedish nation-wide study

BACKGROUND

Darier disease is an autosomal dominant skin disorder caused by mutations in the ATP2A2 gene. Anecdotal reports suggest a relationship between Darier disease and intellectual disabilities, but these reports are based on small clinical samples and limited by absence of control populations.

OBJECTIVES

To examine the risk of intellectual disability and subclinical impairments in cognitive ability in Darier disease.

METHODS

We conducted a matched cohort study based on Swedish Population-, Patient- and Conscript Registers. The risk of being diagnosed with intellectual disability was estimated in 770 individuals with Darier disease, compared with matched comparison individuals without Darier disease. Associations were examined with risk ratios from conditional logistic regressions. In addition, we analysed test-based cognitive ability data (i.e. IQ data) from the Swedish conscript examination, for a subset of patients without diagnosed intellectual disability.

RESULTS

Individuals with Darier disease had a sixfold increased risk of being diagnosed with intellectual disability (risk ratio 6.2, 95% confidence interval 3.1-12.4). For conscripted individuals with Darier disease but no diagnosed intellectual disability, mean cognitive ability scores were about half a standard deviation lower than for comparison subjects.

CONCLUSIONS

Darier disease is associated with intellectual disability and subclinical impairments in cognitive ability. The Darier-causing mutations merit further attention in molecular genetic research on intellectual disability and cognitive ability.

The association between Darier disease, bipolar disorder, and schizophrenia revisited: a population-based family study

OBJECTIVES

Darier disease is an autosomal dominant skin disorder caused by mutations in the ATPase, Ca++ transporting, cardiac muscle, slow twitch 2 (ATP2A2) gene and previously reported to cosegregate with bipolar disorder and schizophrenia in occasional pedigrees. It is, however, unknown whether these associations exist also in the general population, and the objective of this study was to examine this question.

METHODS

We compared a national sample of individuals with Darier disease and their first-degree relatives with matched unexposed individuals from the general population and their first-degree relatives, respectively. To examine risks for bipolar disorder and schizophrenia, risk ratios and 95% confidence intervals (CIs) were estimated using conditional logistic regressions.

RESULTS

Individuals with Darier disease had a 4.3 times higher risk of being diagnosed with bipolar disorder (95% CI: 2.6-7.3) and a 2.3 times higher risk of being diagnosed with schizophrenia (95% CI: 1.1-5.2) than matched individuals from the general population. Relatives of individuals with Darier disease had a 1.6 times higher risk of having bipolar disorder (95% CI: 1.1-2.5) than relatives of matched individuals from the general population, but no increased risk of schizophrenia (risk ratio = 0.8, 95% CI: 0.4-1.8).

CONCLUSIONS

The association between Darier disease and bipolar disorder is manifest also in the population, and our data suggest that genetic variability within the ATP2A2 gene that causes Darier disease also confers susceptibility for bipolar disorder. The Darier-causing mutations merit additional attention in molecular genetic research on bipolar disorder.

EvoTol: a protein-sequence based evolutionary intolerance framework for disease-gene prioritization

Methods to interpret personal genome sequences are increasingly required. Here, we report a novel framework (EvoTol) to identify disease-causing genes using patient sequence data from within protein coding-regions. EvoTol quantifies a gene's intolerance to mutation using evolutionary conservation of protein sequences and can incorporate tissue-specific gene expression data. We apply this framework to the analysis of whole-exome sequence data in epilepsy and congenital heart disease, and demonstrate EvoTol's ability to identify known disease-causing genes is unmatched by competing methods. Application of EvoTol to the human interactome revealed networks enriched for genes intolerant to protein sequence variation, informing novel polygenic contributions to human disease.

Cooccurrence of Darier's Disease and Epilepsy: A Pediatric Case Report and Review of the Literature

Darier's disease is a skin disorder characterized by multiple eruptions of hyperkeratosis or crusted papules at seborrheic areas with histologic acantholysis and dyskeratosis. It is caused by mutations in a single gene, being ATP2A2 and that is expressed in the skin and brain. The cooccurrence of various neurologic and psychiatric diseases with Darier's disease has been reported frequently in literature. They include mood disorders, epilepsy, encephalopathy, and schizophrenia. In this study, we report a pediatric case with the cooccurrence of Darier's disease and epilepsy. We also revised current English literature on this topic.

[Darier disease]

Darier disease (Darier-White disease, dyskeratosis follicularis) is a rare autosomal dominant genodermatosis with regional differences in prevalence. The responsible mutations have been identified on chromosome 12q23-24.1. The gene encodes a calcium-ATPase type 2 in the sarco-/endoplasmic reticulum (SERCA2), which belongs to the large family of P-type cation pumps. This pump couples ATP hydrolysis to the transport of cations across membranes and thus plays a significant role in intracellular calcium signaling. Neuropsychiatric disorders are often associated with Darier disease. However, these diseases are not due to mutations in the gene ATP2A2 but to a susceptibility locus in a 6.5 Mb region near this gene. Currently, the treatment is strictly limited to the relief of symptoms. In severe cases, oral retinoids (acitretin: initial 10-20 mg/Tag and isotretinoin: 0.5-1 mg/kg/day) lead to a response in 90% of cases. However, side effects often prevent long-term use of vitamin A derivatives.

The ATP2A2 gene in patients with Darier's disease: one novel splicing mutation

BACKGROUND

Darier's disease (DD) is a rare, inherited skin disorder characterized by warty papules and plaques over the seborrheic area, such as central trunk, flexures, scalp, and forehead. Mutations in ATP2A2 gene encoding the enzyme sarco/endoplasmic reticulum Ca(2+) ATPase type 2 are responsible for the disease. Here we report two Chinese families affected by DD with two ATP2A2 mutations.

MATERIALS AND METHODS

DNA was extracted from the peripheral blood samples and then subjected to polymerase chain reaction amplification and direct automated DNA sequencing.

RESULTS

A heterozygous G to T transition in the first nucleotide of intron 7 (c.630 + 1G>T) and G to A transversion at nucleotide 2898 in exon 20 of the ATP2A2 gene were identified in two pedigrees, respectively. The former mutation in the splice site is a novel mutation and is thought to lead to aberrant splicing and premature protein truncation. The latter has already been described, which leads to premature termination codons (PTC) (W966X).

CONCLUSION

The results will contribute to the expanding database of ATP2A2 mutations in patients with DD and be useful for inherited counseling and prenatal examination for affected families.

Protein aggregation of SERCA2 mutants associated with Darier disease elicits ER stress and apoptosis in keratinocytes

Mutations in sarcoplasmic/endoplasmic reticulum calcium ATPase 2 (SERCA2) underlie Darier disease (DD), a dominantly inherited skin disorder characterized by loss of keratinocyte adhesion (acantholysis) and abnormal keratinization (dyskeratosis) resulting in characteristic mucocutaneous abnormalities. However, the molecular pathogenic mechanism by which these changes influence keratinocyte adhesion and viability remains unknown. We show here that SERCA2 protein is extremely sensitive to endoplasmic reticulum (ER) stress, which typically results in aggregation and insolubility of the protein. Depletion of ER calcium stores is not necessary for the aggregation but accelerates the progression. Systematic analysis of diverse mutants identical to those found in DD patients demonstrated that the ER stress initiator is the SERCA2 mutant protein itself. These SERCA2 proteins were found to be less soluble, to aggregate and to be more polyubiquitinylated. After transduction into primary human epidermal keratinocytes, mutant SERCA2 aggregates elicited ER stress, caused increased numbers of cells to round up and detach from the culture plate, and induced apoptosis. These mutant induced events were exaggerated by increased ER stress. Furthermore, knockdown SERCA2 in keratinocytes rendered the cells resistant to apoptosis induction. These features of SERCA2 and its mutants establish a mechanistic base to further elucidate the molecular pathogenesis underlying acantholysis and dyskeratosis in DD.

Identification of mutation c.632G>A (p.G211D) in the ATP2A2 gene and genotype-phenotype correlation in a large Chinese family with Darier's disease

Darier's disease (DD, MIM 124200) is an autosomal dominant inherited skin disease. Mutations in the ATP2A2 gene, which encoded the sarcoplasmic/endoplasmic reticulum Ca(2+) -ATPase isoform 2 (SERCA2), are responsible for this skin disorder. Here we report the clinical, genetic, and molecular characterization of a large Chinese family with DD. We identified mutation c.632G>A (p.G211D) in the ATP2A2 gene in this family. Genotype-phenotype correlation in available family members provided helpful genetic counseling information for mutation carriers.

The Ca2+ pumps of the endoplasmic reticulum and Golgi apparatus

The various splice variants of the three SERCA- and the two SPCA-pump genes in higher vertebrates encode P-type ATPases of the P(2A) group found respectively in the membranes of the endoplasmic reticulum and the secretory pathway. Of these, SERCA2b and SPCA1a represent the housekeeping isoforms. The SERCA2b form is characterized by a luminal carboxy terminus imposing a higher affinity for cytosolic Ca(2+) compared to the other SERCAs. This is mediated by intramembrane and luminal interactions of this extension with the pump. Other known affinity modulators like phospholamban and sarcolipin decrease the affinity for Ca(2+). The number of proteins reported to interact with SERCA is rapidly growing. Here, we limit the discussion to those for which the interaction site with the ATPase is specified: HAX-1, calumenin, histidine-rich Ca(2+)-binding protein, and indirectly calreticulin, calnexin, and ERp57. The role of the phylogenetically older and structurally simpler SPCAs as transporters of Ca(2+), but also of Mn(2+), is also addressed.

Dysregulation of presynaptic calcium and synaptic plasticity in a mouse model of 22q11 deletion syndrome

The 22q11 deletion syndrome (22q11DS) is characterized by cognitive decline and increased risk of psychiatric disorders, mainly schizophrenia. The molecular mechanisms of neuronal dysfunction in cognitive symptoms of 22q11DS are poorly understood. Here, we report that a mouse model of 22q11DS, the Df(16)1/+ mouse, exhibits substantially enhanced short- and long-term synaptic plasticity at hippocampal CA3-CA1 synapses, which coincides with deficits in hippocampus-dependent spatial memory. These changes are evident in mature but not young animals. Electrophysiological, two-photon imaging and glutamate uncaging, and electron microscopic assays in acute brain slices showed that enhanced neurotransmitter release but not altered postsynaptic function or structure caused these changes. Enhanced neurotransmitter release in Df(16)1/+ mice coincided with altered calcium kinetics in CA3 presynaptic terminals and upregulated sarco(endo)plasmic reticulum calcium-ATPase type 2 (SERCA2). SERCA inhibitors rescued synaptic phenotypes of Df(16)1/+ mice. Thus, presynaptic SERCA2 upregulation may be a pathogenic event contributing to the cognitive symptoms of 22q11DS.

Characterization of sarcoplasmic reticulum Ca2+ ATPase nucleotide binding domain mutants using NMR spectroscopy

Sarcoplasmic reticulum Ca(2+) ATPase (SERCA) is essential for muscle function by transporting Ca(2+) from the cytosol into the sarcoplasmic reticulum through ATP hydrolysis. In this report, the effects of substitution mutations on the isolated SERCA-nucleotide binding domain (SERCA-N) were studied using NMR. (15)N-(1)H HSQC spectra of substitution mutants at the nucleotide binding site, T441A, R560V, and C561A, showed chemical shift changes, primarily in residues adjacent to the mutation sites, indicating only local effects. Further, the patterns of chemical shift changes upon AMP-PNP binding to these mutants were similar to that of the wild type SERCA-N (WT). In contrast to these nucleotide binding site mutants, a mutant found in patients with Darier's disease, E412G, showed small but significant chemical shift changes throughout the protein and rapid precipitation. However, the AMP-PNP dissociation constant (∼2.5 mM) was similar to that of WT (∼3.8 mM). These results indicate that the E412G mutant retains its catalytic activity but most likely reduces its stability. Our findings provide molecular insight into previous clinical, physiological, and biochemical observations.

Darier disease : a disease model of impaired calcium homeostasis in the skin

The importance of extracellular calcium in epidermal differentiation and intra-epidermal cohesion has been recognized for many years. Darier disease (DD) was the first genetic skin disease caused by abnormal epidermal calcium homeostasis to be identified. DD is characterized by loss of cell-to-cell adhesion and abnormal keratinization. DD is caused by genetic defects in ATP2A2 encoding the sarco/endoplasmic reticulum Ca(2+)-ATPase isoform 2 (SERCA2). SERCA2 is a calcium pump of the endoplasmic reticulum (ER) transporting Ca(2+) from the cytosol to the lumen of ER. ATP2A2 mutations lead to loss of Ca(2+) transport by SERCA2 resulting in decreased ER Ca(2+) concentration in Darier keratinocytes. Here, we review the role of SERCA2 pumps and calcium in normal epidermis, and we discuss the consequences of ATP2A2 mutations on Ca(2+) signaling in DD. This article is part of a Special Issue entitled: 11th European Symposium on Calcium.

Four novel ATP2A2 mutations in Slovenian patients with Darier disease

BACKGROUND

Darier disease (DD) is an autosomal dominant genodermatosis caused by mutations in the ATP2A2 gene. It has been reported that depletion of Ca(2+) stores within the endoplasmic reticulum of keratinocytes is associated with impaired cell cycle regulation and terminal differentiation. Mechanical stress, heat, or UV irradiation might delay cell cycle exit and permit progression into the quiescent stage without repair. When there is associated DNA damage, this can lead to an accumulation of secondary somatic mutations and possible clonal proliferation of damaged keratinocyes within keratotic papules and plaques.

OBJECTIVE

We sought to present clinical, demographic, and genetic analysis of the cohort of Slovenian patients with DD, which represents 52% of DD patients in the country.

METHODS

We examined 28 Slovenians with DD and screened genomic DNA for ATP2A2 mutations and RNA for splice site mutations.

RESULTS

The estimated prevalence of the disease in Slovenia is 2.7/100.000. We identified 7 different ATP2A2 mutations, 4 of which are novel: A516P, R559G, 463-6del6, and 1762-6del18. We also found two previously described polymorphisms in intron XVIII (2741 + 54 G>A) and in exon 15 (2172 G>A; A724A), with allele frequencies of 64.15% and 11.32%, respectively. There was a history of perceptive deafness in two DD patients from two families.

LIMITATIONS

Analysis of SERCA2 expression, measurements of Ca(2+) uptake and their influence on desmosomal assembly in vitro would add additional value to the study. Although single-stranded conformational analysis (SSCP) is a common and accepted method for screening for the presence of mutations, it does miss 10% to 20% of mutations.

CONCLUSIONS

We identified 4 novel ATP2A2 mutations in Slovenian patients with DD. Deafness seems to be a new phenotypic characteristic of DD patients.

Identification a novel missense mutation p.R761L in Chinese patients with Darier's disease

Darier's disease (DD, MIM 124200) is an autosomal dominant inherited disease. It is usually present in teenagers or adults with multiple keratotic papules or plaques in seborrheic areas. Pathogenic mutations in the ATP2A2 gene have been identified. It encodes the sarcoplasmic or endoplasmic reticulum Ca(2+) ATPase isoform 2 (SERCA2). Polymerase chain reaction and direct sequencing of the full coding sequence of ATP2A2 gene were performed to identify the mutation in this family. In this report, we identified a novel mutation of ATP2A2 gene in a Chinese family with DD. It is a novel heterozygous nucleotide G --> T transition at position 2,282 in exon 15 of the ATP2A2 gene. Our study expands the database on the ATP2A2 gene mutations in DD.

Factors controlling the activity of the SERCA2a pump in the normal and failing heart

Heart failure is the leading cause of death in western countries and is often associated with impaired Ca(2+) handling in the cardiomyocyte. In fact, cardiomyocyte relaxation and contraction are tightly controlled by the activity of the cardiac sarco(endo)plasmic reticulum (ER/SR) Ca(2+) pump SERCA2a, pumping Ca(2+) from the cytosol into the lumen of the ER/SR. This review addresses three important facets that control the SERCA2 activity in the heart. First, we focus on the alternative splicing of the SERCA2 messenger, which is strictly regulated in the developing heart. This splicing controls the formation of three SERCA2 splice variants with different enzymatic properties. Second, we will discuss the role and regulation of SERCA2a activity in the normal and failing heart. The two well-studied Ca(2+) affinity modulators phospholamban and sarcolipin control the activity of SERCA2a within a narrow window. An aberrantly high or low Ca(2+) affinity is often observed in and may even trigger cardiac failure. Correcting SERCA2a activity might therefore constitute a therapeutic approach to improve the contractility of the failing heart. Finally, we address the controversies and unanswered questions of other putative regulators of the cardiac Ca(2+) pump, such as sarcalumenin, HRC, S100A1, Bcl-2, HAX-1, calreticulin, calnexin, ERp57, IRS-1, and -2.

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.

[Darier's disease: an evaluation of its neuropsychiatric component]

BACKGROUND

Darrier's disease is a rare genodermatosis with a dominant autosomic penetrating variable transmission. The association between Darier's disease and neuropsychiatric disorders has been reported since 1996. Moreover, associations with mental retardation, schizophrenia, mood disorders and suicide have been reported. The discovery in 1999 of the ATP2A2 gene of Darier's disease, localised on chromosome 12, allowed significant advances notably in understanding the pathogenicity of these symptoms.

MATERIAL AND METHODS

In this article, we present the preliminary results of a clinical and genetic study of eight Tunisian families, involving dermatologists, psychiatrists and geneticians. Eight patients with Darier's disease and their first degree relatives were included in the study after they had given their written consent. Thirty-five subjects were examined, 23 of them had Darier's disease. All patients were submitted to a complete clinical examination; notably dermatological screening, genetic inquiry and blood tests for haplotype analysis. Only 13 of them underwent a psychiatric examination.

RESULTS

The psychiatric examination was carried out only in 13 patients with Darier's disease, who revealed neuropsychiatric symptoms with a frequency of 61.1% (8/13). Two patients presented mild mental retardation; six patients had mood disorders, three of them belonged to the same family (two had recurrent depression, four belonged to the bipolar spectrum [2 bipolar disorder type 2, 2 cyclothymia]). The coexpression of the two distinct phenotypes (Darier's disease and bipolar disease), within the same three members' of the family of our study, suggests the existence of a genetic linkage between the two diseases, as has been reported in the literature.