The neuropsychiatric phenotype in Darier disease.

BACKGROUND: Darier disease (DD) is a rare autosomal dominantly inherited skin disorder in which co-occurrence of neuropsychiatric abnormalities has been frequently reported by dermatologists. It is caused by mutations in a single gene, ATP2A2, which is expressed in the skin and brain. OBJECTIVES: To conduct the first systematic investigation of the neuropsychiatric phenotype in DD. METHODS: One hundred unrelated individuals with DD were assessed using a battery of standardized neuropsychiatric measures. Data were also obtained on a number of clinical features of DD. RESULTS: Individuals with DD were found to have high lifetime rates of mood disorders (50%), specifically major depression (30%) and bipolar disorder (4%), and suicide attempts (13%) and suicidal thoughts (31%). These were more common in DD when compared with general population data. The prevalence of epilepsy (3%) in the sample was also higher than the prevalence in the general population. There was no consistent association of specific dermatological features of DD and presence of psychiatric features. CONCLUSIONS: These findings highlight the need for clinicians to assess and recognize neuropsychiatric symptoms in DD. The results do not suggest that neuropsychiatric symptoms are simply a psychological reaction to having a skin disease, but are consistent with the pleiotropy hypothesis that mutations in the ATP2A2 gene, in addition to causing DD, confer susceptibility to neuropsychiatric features. Further research is needed to investigate genotype-phenotype correlations between the types and/or locations of pathogenic mutations within ATP2A2 and the expressed neuropsychiatric phenotypes.

Expression of the sarco/endoplasmic reticulum calcium ATPase type 2 and 3 isoforms in normal skin and Darier's disease.

BACKGROUND: Darier's disease (DD) is caused by mutations in ATP2A2, which encodes the sarco/endoplasmic reticulum calcium ATPase type 2 (SERCA2), a member of a family of calcium pumps important in intracellular calcium signalling. SERCA2 has two isoforms. SERCA2a occurs mainly in cardiac and skeletal muscle, whereas SERCA2b occurs ubiquitously and is coexpressed with the related SERCA type 3 (SERCA3) in many tissues. It is not known why mutations in the widely expressed SERCA2 manifest as a focal skin disease. OBJECTIVES: To provide insight into the pathogenesis of DD by examining SERCA isoform expression in normal skin and DD skin. METHODS: Using immunohistochemistry we studied SERCA2a, SERCA2b and SERCA3 expression in nonlesional and lesional skin from seven patients with DD and normal skin from seven control subjects. We quantified SERCA2a and SERCA2b staining intensity by grey scale analysis of fluorescence intensity. RESULTS: In normal and DD epidermis both SERCA2a and SERCA2b staining was seen. SERCA2a staining in epidermis was less intense relative to pilar muscle whereas SERCA2b staining in epidermis was of marginally greater intensity than in pilar muscle. SERCA3 was not expressed in normal or DD epidermis, but was found in eccrine glands and blood vessels. No reduction was detected in SERCA2a or SERCA2b staining intensity in DD nonlesional epidermis compared with control epidermis. In within-patient comparisons, SERCA2a and SERCA2b staining in lesional epidermis was less intense than in nonlesional epidermis. CONCLUSIONS: Both SERCA2a and SERCA2b are present in epidermis, although the latter may predominate. The absence of coexpressed SERCA3 in epidermis may explain the localization of DD. Comparable SERCA2 staining intensity in nonlesional DD and control epidermis, even in patients predicted to be haploinsufficient, suggests partial compensation by upregulation of the normal allele. Unknown additional factors may trigger focal lesions by overcoming this compensation. Reduced staining intensity in lesional tissue may be secondary, or may reflect local downregulation of SERCA2 expression predisposing to development of focal lesions.

Genes, growth factors and acanthosis nigricans.

Acanthosis nigricans (AN) occurs most commonly in association with hyperinsulinaemia and more rarely as a paraneoplastic syndrome. It is also a feature of several genetic disorders. Indirect evidence suggests a role for tyrosine kinase growth factor receptor signalling in the pathogenesis of AN. Defects in the insulin receptor gene causing insulin resistance and AN are well recognized, but recent data in several other syndromes of this association, including lipodystrophic disorders, have identified causative defects in other pathways. The mechanism of AN due to insulin resistance is most probably direct or indirect activation of the insulin-like growth factor 1 receptor by high levels of circulating insulin. However, more direct evidence for abnormal tyrosine kinase receptor signalling in AN has been provided by studies of craniosynostosis and skeletal dysplasia syndromes with AN, which have identified activating mutations in fibroblast growth factor receptors.

Genetic epidemiology of Darier's disease: a population study in the west of Scotland.

BACKGROUND: Darier's disease has a world-wide distribution, but estimates of prevalence have varied. The discovery that the disease is due to mutations in ATP2A2 provides the opportunity to study the genetic epidemiology of the disease in localized populations. OBJECTIVES: To survey the prevalence of Darier's disease in the west of Scotland and look for founder effects in this population. METHODS: We ascertained cases of Darier's disease in the west of Scotland and used genealogy and mutational analysis to seek common ancestry. RESULTS: Seventy-eight current cases were identified, giving a prevalence of approximately 1 : 30 000. While 63 cases gave a history of Darier's disease in previous generations, conventional genealogy identified only two pairs of two family groups with common ancestry within the last 180 years. Eleven patients (14%; three of whom had in total four affected children) had probable de novo mutations. Causative mutations in ATP2A2 have been identified in 11 of 15 pedigrees screened for mutation, but no two share the same mutation. CONCLUSIONS: High estimates of prevalence are likely to be due to intensive ascertainment, rather than founder effects. Darier's disease is likely to be more common than has been recognized in other populations.

Platelet and cardiac function in Darier's disease.

ATP2A2, the gene that is abnormal in Darier's disease, encodes SERCA2, a calcium pump that is expressed in many tissues. The wide expression of SERCA2 might suggest that ATP2A2 mutations would cause a multisystem disease. There is however, no evidence of consistent extracutaneous manifestations of Darier's disease. We have conducted preliminary studies in patients with Darier's disease, in two extracutaneous systems in which SERCA2 is known to be important, in order to investigate whether subtle defects have been overlooked. We found no evidence for altered cardiac function in 10 patients using two-dimensional, colour and Doppler echocardiography. There were no consistent defects in platelet function in 12 patients, using bleeding time and aggregation studies. We conclude that the skin is sensitive to defects in SERCA2 function to which other systems appear robust.

trans-dominant inhibition of connexin-43 by mutant connexin-26: implications for dominant connexin disorders affecting epidermal differentiation.

Dominant mutations of GJB2-encoding connexin-26 (Cx26) have pleiotropic effects, causing either hearing impairment (HI) alone or in association with palmoplantar keratoderma (PPK/HI). We examined a British family with the latter phenotype and identified a new dominant GJB2 mutation predicted to eliminate the amino acid residue E42 (DeltaE42) in Cx26. To dissect the pathomechanisms that result in diverse phenotypes of dominant GJB2 mutations, we studied the effect of three Cx26 mutants (DeltaE42, D66H and R75W) identified in individuals with PPK/HI, and another (W44C) present in individuals with non-syndromic HI on gap junctional intercellular communication. We expressed mutant Cx26 alone and together with the epidermal connexins Cx26, Cx37 and Cx43 in paired Xenopus oocytes, and measured the intercellular coupling by dual voltage clamping. Homotypic expression of each connexin as well as co-expression of wild-type (wt) Cx26/wtCx43 and wtCx26/wtCx37 yielded variable, yet robust, levels of channel activity. However, all four Cx26 mutants were functionally impaired and failed to induce intercellular coupling. When co-expressed with wtCx26, all four mutants suppressed the wtCx26 channel activity consistent with a dominant inhibitory effect. However, only those Cx26 mutants associated with a skin phenotype also significantly (P<0.05) inhibited intercellular conductance of co-expressed wtCx43, indicating a direct interaction of mutant Cx26 units with wtCx43. These results demonstrate, for the first time, a trans-dominant negative effect of Cx26 mutants in vitro. Furthermore, they support a novel concept suggesting that the principal mechanism for manifestation of dominant GJB2 mutations in the skin is their dominant interference with the function of wtCx43. This assumption is further corroborated by our finding that Cx26 and Cx43 focally colocalize at gap junctional plaques in affected skin tissue of two carriers of DeltaE42.

A novel mutation in the keratin 13 gene causing oral white sponge nevus.

White sponge nevus (WSN) is an autosomal-dominantly inherited form of mucosal leukokeratosis. Defects in keratins, proteins that form the stress-bearing cytoskeleton in epithelia, have been shown to cause several epithelial fragility disorders. Recently, mutations in the genes encoding mucosal-specific keratins K4 and K13 were shown to be the underlying cause of WSN. We have studied a large Scottish family with 19 persons affected by WSN in four generations. The K4 locus was excluded by genetic linkage analysis; however, genetic linkage consistent with a K13 defect was obtained. Subsequently, a heterozygous missense mutation 335A>G was detected in exon 1 of the KRT13 gene, predicting the amino acid change N112S in the 1A domain of the K13 polypeptide. The mutation was confirmed in affected family members and was excluded from 50 unaffected people by restriction enzyme analysis. These results confirm that mucosal keratin defects are the cause of WSN.

Localization of a gene (MCUL1) for multiple cutaneous leiomyomata and uterine fibroids to chromosome 1q42.3-q43.

Dominant transmission of multiple uterine and cutaneous smooth-muscle tumors is seen in the disorder multiple leiomyomatosis (ML). We undertook a genomewide screen of 11 families segregating ML and found evidence for linkage to chromosome 1q42.3-q43 (maximum multipoint LOD score 5.40). Haplotype construction and analysis of recombinations permitted the minimal interval containing the locus, which we have designated "MCUL1," to be refined to an approximately 14-cM region flanked by markers D1S517 and D1S2842. Allelic-loss studies of tumors indicated that MCUL1 may act as a tumor suppressor. Identification of MCUL1 should have wide interest, since this gene may harbor low-penetrance variants predisposing to the common form of uterine fibroids and/or may undergo somatic mutation in sporadic leiomyomata.

Novel and recurrent mutations in the genes encoding keratins K6a, K16 and K17 in 13 cases of pachyonychia congenita.

Thirteen patients with pachyonychia congenita types 1 and 2 were studied, two of which had a family history of pachyonychia and 11 of which were sporadic cases. Heterozygous mis-sense or small in-frame insertion/deletion mutations were detected in the genes encoding keratins K6a, K16, and K17 in all cases. Three novel mutations, F174V, E472K, and L469R were found in the K6a gene. Two novel mutations, M121T and L128Q were detected in K16. Similarly, three novel mutations, L95P, S97del, and L99P were found in K17. In addition, we identified recurrent mutations N171del (three instances) and F174S in K6a and R94H in K17. Analysis of both phenotype and genotype data led to the following conclusions: (i) K6a or K16 mutations produce the pachyonychia congenita type 1 phenotype, whereas K17 (or K6b) mutations cause pachyonychia congenita type 2; (ii) the presence of pilosebaceous cysts following puberty is the best indicator of pachyonychia congenita type 2; (iii) prepubescent patients are more difficult to classify due to the lack of cysts; and (iv) natal teeth are indicative of pachyonychia congenita type 2, although their absence does not preclude the pachyonychia congenita type 2 phenotype. This study establishes useful diagnostic criteria for pachyonychia congenita types 1 and 2, which will help limit unnecessary DNA analysis in the diagnosis and management of this genetically heterogeneous group of genodermatoses.

Mutant loricrin is not crosslinked into the cornified cell envelope but is translocated into the nucleus in loricrin keratoderma.

Loricrin is a major constituent of the epidermal cornified cell envelope. We have recently identified heterozygous loricrin gene mutations in two dominantly inherited skin diseases, the ichthyotic variant of Vohwinkel syndrome and progressive symmetric erythrokeratoderma, collectively termed loricrin keratoderma. In order to see whether the mutant loricrin molecules predicted by DNA sequencing are expressed in vivo and to define their pathologic effects, we raised antibodies against synthetic peptides corresponding to the mutated sequences of loricrin. Immunoblotting of horny cell extracts from loricrin keratoderma patients showed specific bands for mutant loricrin. Immunohistochemistry of loricrin keratoderma skin biopsies showed positive immunoreactivity to the mutant loricrin antibodies in the nuclei of differentiated epidermal keratinocytes. The immunostaining was localized to the nucleoli of the lower granular cell layer. As keratinocyte differentiation progressed the immunoreactivity moved gradually into the nucleoplasm leaving nucleoli mostly nonimmunoreactive. No substantial staining was observed along the cornified cell envelope. This study confirmed that mutant loricrin was expressed in the loricrin keratoderma skin. Mutant loricrin, as a dominant negative disrupter, is not likely to affect cornified cell envelope crosslinking directly, but seems to interfere with nuclear/nucleolar functions of differentiating keratinocytes. In addition, detection of the mutant loricrin in scraped horny layer could provide a simple noninvasive screening test for loricrin keratoderma. J Invest Dermatol 115:1088-1094 2000

Connexin mutations associated with palmoplantar keratoderma and profound deafness in a single family.

Recently, mutations in two gap junction genes, GJB2 and GJB3 (encoding Connexin 26 and Connexin 31, respectively), have been shown to underlie either inherited hearing loss and skin disease or both disorders. In this study, we have extended our analysis of a small family in which palmoplantar keratoderma and various forms of deafness is segregating. In addition to the previously described sequence variant M34T in GJB2, two other sequence variants were identified: D66H also in GJB2 and R32W in GJB3. As D66H segregated with the skin disease, it is likely to underlie the palmoplantar keratoderma. The other two gap junction variants identified may contribute to the type of hearing impairment and the variable severity of the skin disease in the family.

Connexin mutations associated with palmoplantar keratoderma and profound deafness in a single family.

Recently, mutations in two gap junction genes, GJB2 and GJB3 (encoding Connexin 26 and Connexin 31, respectively), have been shown to underlie either inherited hearing loss and skin disease or both disorders. In this study, we have extended our analysis of a small family in which palmoplantar keratoderma and various forms of deafness is segregating. In addition to the previously described sequence variant M34T in GJB2, two other sequence variants were identified: D66H also in GJB2 and R32W in GJB3. As D66H segregated with the skin disease, it is likely to underlie the palmoplantar keratoderma. The other two gap junction variants identified may contribute to the type of hearing impairment and the variable severity of the skin disease in the family.

Hailey-Hailey disease is caused by mutations in ATP2C1 encoding a novel Ca(2+) pump.

Hailey-Hailey disease (HHD) is an autosomal dominant skin disorder characterized by suprabasal cell separation (acantholysis) of the epidermis. Previous genetic linkage studies localized the gene to a 5 cM interval on human chromosome 3q21. After reducing the disease critical region to <1 cM, we used a positional cloning strategy to identify the gene ATP2C1, which is mutated in HHD. ATP2C1 encodes a new class of P-type Ca(2+)-transport ATPase, which is the homologue for the rat SPLA and the yeast PMR1 medial Golgi Ca(2+)pumps and is related to the sarco(endo)plasmic calcium ATPase (SERCA) and plasma membrane calcium ATPase (PCMA) families of Ca(2+)pumps. The predicted protein has the same apparent transmembrane organization and contains all of the conserved domains present in other P-type ATPases. ATP2C1 produces two alternative splice variants of approximately 4.5 kb encoding predicted proteins of 903 and 923 amino acids. We identified 13 different mutations, including nonsense, frameshift insertion and deletions, splice-site mutations, and non-conservative missense mutations. This study demonstrates that defects in ATP2C1 cause HHD and together with the recent identification of ATP2A2 as the defective gene in Darier's disease, provide further evidence of the critical role of Ca(2+)signaling in maintaining epidermal integrity.