Investigation of the pathogenesis of ADAR1 gene in dyschromatosis symmetrica hereditaria.

The pathogenesis of dyschromatosis symmetrica hereditaria (DSH) has not been well defined. In this study, we sought to investigate the influence of the ADAR1 gene on DSH both in vitro and in vivo. Morpholino knockdown of adar1 in zebrafish produced phenotypes characterized by polarity changes, and abnormal migration and distribution of melanocytes. Differential expression of C-KIT and distinct patterns of apoptosis between hyperpigmented and hypopigmented areas in DSH patient were detected by means of immunohistochemical methods and TUNEL assays, respectively. This study revealed that adar1 knockdown in a zebrafish model resulted in abnormal migration and changes in the cell polarity of melanocytes, and provided novel insight into the mechanism of DSH pathogenesis.

Dyschromatosis symmetrica hereditaria: A clue to early diagnosis of Aicardi-Goutières syndrome.

A 6-year-old female with a history of Aicardi-Goutières syndrome (AGS) presented to dermatology clinic with hypopigmented and hyperpigmented macules and patches consistent with dyschromatosis symmetrica hereditaria (DSH). Previous genetic workup demonstrated a de novo, heterozygous mutation in the adenosine deaminase acting on RNA 1 (ADAR) gene. While the co-occurrence of AGS and DSH has previously been described in mutations of the ADAR gene, our case highlights the potential association between these disorders that may aid in earlier future diagnosis of AGS.

[Analysis of ADAR gene variant in a Chinese pedigree affected with dyschromatosis symmetrica hereditaria].

OBJECTIVE: To analyze the clinical features and genetic basis for a Chinese pedigree affected with hereditary dyschromatosis symmetrica hereditaria (DSH). METHODS: Peripheral blood samples of the proband and his mother were collected and subjected to PCR and Sanger sequencing. RESULTS: The patient has conformed to the typical pattern of DSH and manifested with hyperpigmentation, hypo- and hyperpigmentation spots on the back of hands, feet and face. Sanger sequencing confirmed that the proband and his mother have both harbored heterozygous splicing variant c.2762+1G>T in exon 9 of the ADAR gene, which was unreported previously. The same variant was not detected among 100 healthy controls. According to the guidelines of the American College of Medical Genetics and Genomics, the variant was predicted to be pathogenic (PVS1+PM2+PP4). CONCLUSION: The c.2762+1G>T variant of the ADAR gene probably underlay the DSH in this pedigree. Above finding has enriched the spectrum of ADAR gene mutations.

[Analysis of a Chinese pedigree affected with dyschromatosis symmetrica hereditaria due to a novel variant of ADAR gene].

OBJECTIVE: To explore the genetic basis for a Chinese pedigree affected with dyschromatosis symmetrica hereditaria (DSH). METHODS: PCR and Sanger sequencing were carried out for the proband, and suspected variant was validated by Sanger sequencing in the pedigree. RESULTS: The proband was found to harbor a novel variant of c.1352delA (p.N451Mfs*13) of the ADAR (NM_001111) gene. The same variant was found in her affected mother and sister, but not in her unaffected father, uncle, and 100 healthy individual. CONCLUSION: The novel variant of the ADAR gene probably underlay the pathogenesis of DSH in this pedigree.

Dyschromatosis Universalis Hereditaria.

Dyschromatosis universalis hereditaria (DUH) is a rare pigmentary genodermatosis usually inherited in autosomal dominant fashion characterized by multiple pinpoint to pea-sized hypo- and hyper-pigmented macules arranged in reticulate pattern that develops within the first few years of life. An 11 years old boy presented with multiple gradually progressive asymptomatic hypopigmented macules on hyperpigmented background on trunk, extremities and face since 2 years of age. Family history was absent. Punch biopsies revealed increased number of melanocytes in the epidermis with basal cell vacuolar alteration and pigmentary incontinence and perivascular infiltration by lymphocytes and melanophages in the dermis. We herein present a sporadic case of dyschromatosis universalis hereditaria.

Novel missense mutation of SASH1 in a Chinese family with dyschromatosis universalis hereditaria.

BACKGROUND: Dyschromatosis universalis hereditaria (DUH) is a pigmentary dermatosis characterized by generalized mottled macules with hypopigmention and hyperpigmention. ABCB6 and SASH1 are recently reported pathogenic genes related to DUH, and the aim of this study was to identify the causative mutations in a Chinese family with DUH. METHODS: Sanger sequencing was performed to investigate the clinical manifestation and molecular genetic basis of these familial cases of DUH, bioinformatics tools and multiple sequence alignment were used to analyse the pathogenicity of mutations. RESULTS: A novel missense mutation, c.1529G>A, in the SASH1 gene was identified, and this mutation was not found in the National Center for Biotechnology Information Database of Short Genetic Variation, Online Mendelian Inheritance in Man, ClinVar, or 1000 Genomes Project databases. All in silico predictors suggested that the observed substitution mutation was deleterious. Furthermore, multiple sequence alignment of SASH1 revealed that the p.S510N mutation was highly conserved during evolution. In addition, we reviewed the previously reported DUH-related gene mutations in SASH1 and ABCB6. CONCLUSION: Although the affected family members had identical mutations, differences in the clinical manifestations of these family members were observed, which reveals the complexity of the phenotype-influencing factors in DUH. Our findings reveal the mutation responsible for DUH in this family and broaden the mutational spectrum of the SASH1 gene.

Two novel SASH1 mutations in Chinese families with dyschromatosis universalis hereditaria.

BACKGROUND: Dyschromatosis universalis hereditaria (DUH) is a rare genodermatosis characterized by hyper- and hypo-pigmented macules on the face, trunk, and extremities. The condition causes severe cosmetic problem which can lead to significant psychological distress to the patients and bear a negative impact on society. DUH is a condition with genetic heterogeneity. The SASH1 gene was recently identified as pathogenic genes in DUH patients. METHODS: Two families clinically diagnosed with dyschromatosis universalis hereditaria were enrolled. Whole-exome sequencing combined with Sanger sequencing and bioinformatics analysis was performed in the probands. MutationTaster, CADD, SIFT, PolyPhen-2, and LRT software, and The American College of Medical Genetics and Genomics Standards and Guidelines were employed to assess the pathogenicity of detected missense mutations. One hundred healthy unrelated Chinese individuals were used as controls. All participants signed an informed consent form. RESULTS: Genetic screening revealed a heterozygous SASH1 c.1547G>A (p.Ser516Asn) mutation for patients in family 1, and SASH1 c.1547G>T (p.Ser516Ile) for family 2. Both such de novo mutations are located in a highly conserved SLY domain in SASH1, have not been previously reported in any publication, and were not detected in any control databases. CONCLUSIONS: The novel heterozygous mutations, SASH1 c.1547G>A and c.1547G>T, are likely responsible for the DUH phenotype in these two families. Our study expands the mutation spectrum of DUH. Whole-exome sequencing showed its efficiency in the diagnostic of hereditary skin disorders.

Decoupling expression and editing preferences of ADAR1 p150 and p110 isoforms.

Human adenosine deaminase acting on RNA 1 (ADAR1) catalyzes adenosine-to-inosine deamination reactions on double-stranded RNA molecules to regulate cellular responses to endogenous and exogenous RNA. Defective ADAR1 editing leads to disorders such as Aicardi-Goutières syndrome, an autoinflammatory disease that manifests in the brain and skin, and dyschromatosis symmetrica hereditaria, a skin pigmentation disorder. Two ADAR1 protein isoforms, p150 (150 kDa) and p110 (110 kDa), are expressed and can edit RNA, but the contribution of each isoform to the editing landscape remains unclear, largely because of the challenges in expressing p150 without p110. In this study, we demonstrate that p110 is coexpressed with p150 from the canonical p150-encoding mRNA due to leaky ribosome scanning downstream of the p150 start codon. The presence of a strong Kozak consensus context surrounding the p110 start codon suggests the p150 mRNA is optimized to leak p110 alongside expression of p150. To reduce leaky scanning and translation initiation at the p110 start codon, we introduced synonymous mutations in the coding region between the p150 and p110 start codons. Cells expressing p150 constructs with these mutations produced significantly reduced levels of p110. Editing analysis of total RNA from ADAR1 knockout cells reconstituted separately with modified p150 and p110 revealed that more than half of the A-to-I edit sites are selectively edited by p150, and the other half are edited by either p150 or p110. This method of isoform-selective editing analysis, making use of the modified p150, has the potential to be adapted for other cellular contexts.

Co-occurrence of Aicardi-Goutières syndrome type 6 and dyschromatosis symmetrica hereditaria due to compound heterozygous pathogenic variants in ADAR1: a case series from India.

Aicardi-Goutières syndrome type 6 (AGS6) and dyschromatosis symmetrica hereditaria (DSH) are allelic disorders caused respectively by biallelic and heterozygous pathogenic variants in ADAR1. We report three unrelated children presenting with features of both AGS6 and DSH, two of whom had compound heterozygous pathogenic variants in ADAR1. We also describe the novel genetic variants in our cases and review the literature on association of ADAR1-related AGS6 and DSH with these phenotypes.

[Analysis of ADAR1 gene variants in two pedigrees affected with dyschromatosis symmetrica hereditaria].

OBJECTIVE: To detect variants of ADAR1 gene in two Chinese pedigrees affected with dyschromatosis symmetrica hereditaria (DSH). METHODS: Clinical data and peripheral blood samples of the pedigrees were collected. All exons of the ADAR1 gene were amplified by PCR and subjected to Sanger sequencing. Suspected pathogenic variants were validated among other members of the pedigrees and 100 unrelated healthy controls. RESULTS: For pedigree 1, Sanger sequencing has identified a heterozygous missense variant c.3002G>C (p.Asp968His) in exon 11 of the ADAR1 gene in the proband and his father. For pedigree 2, a novel nonsense variant c.3145C>T (p.Gln1049Ter) was identified in exon 12 of the ADAR1 gene in the proband and his son, which were previously unreported and absent among the healthy controls. CONCLUSION: The c.3002G>C (p.Asp968His) and c.3145C>T (p.Gln1049Ter)variants of the ADAR1 gene probably underlay the DSH in the two pedigrees.

Mutated SASH1 promotes Mitf expression in a heterozygous mutated SASH1 knock­in mouse model.

The SAM and SH3 domain­containing 1 (SASH1) genes have been identified as the causal genes of dyschromatosis universalis hereditaria (DUH); these genes cause the pathological phenotypes of DUH, and SASH1 variants have been shown to regulate the abnormal pigmentation phenotype in human skin in various genodermatoses. However, investigations into the mutated SASH1 gene have been limited to in vitro studies. In the present study, to recapitulate the molecular pathological phenotypes of individuals with DUH induced by SASH1 mutations, a heterozygous BALB/c mouse model, in which the human SASH1 c.1654 T>G (p. Tyr 551Asp, Y551D) mutation was knocked in was first generated. The in vivo functional experiments on Y551D SASH1 indicated that the increased expression of microphthalmia­associated transcription factor (Mitf) was uniformly induced in the tails of heterozygous BALB/c mice, and an increased quantity of Mitf­positive epithelial cells was also detected. An increased expression of Mitf­ and Mitf­positive cells was also demonstrated in the epithelial tissues of Y551D­SASH1 affected individuals. In the present study, Mitf expression was also found to be increased by Y551D SASH1 in vitro. Taken together, these findings indicate that the upregulation of Mitf is the bona fide effector of the Y551D SASH1­mediated melanogenesis signaling pathway in vivo. SASH1 may function as a scaffold molecule for the assembly of a SASH1­Mitf molecular complex to regulate Mitf expression in the cell nucleus and thus to promote the hyperpigmented phenotype in the pathogenesis of DUH and other genodermatoses related to pigment abnormalities.

Pathogenesis of a variant in the 5' untranslated region of ADAR1 in dyschromatosis symmetrica hereditaria.

Dyschromatosis symmetrica hereditaria (DSH) is a pigmentary genodermatosis caused by mutations in ADAR1. In this study, we performed mutation analysis on a family that included typical DSH patients. No mutations were found in any coding regions or exon-intron boundary regions of ADAR1, but a previously unreported non-coding heterozygous variant, c.-60A>G, was found in the 5' untranslated region (5'UTR) of ADAR1 in the proband and her mother. The function of 5'UTR in mRNA is not well-understood. To understand the pathogenesis of the variant and the function of the 5'UTR of ADAR1, we constructed two reporter genes carrying the ADAR1 5'UTR sequence with/without the variant between the PGK promoter and a luciferase coding sequence, and performed luciferase assays, semi-quantitative PCR analyses, and polysomal assays. In human melanocytes, c.-60A>G induced a 16% reduction in transcription and a 51% reduction in translation. Our results indicate that the 5'UTR c.-60A>G variant adversely affects the post-transcriptional step in gene expression, leading to DSH. Detailed functional assays of the 5'UTR of ADAR1 in the present study revealed the gene expression to be not only downregulated, but also upregulated by defects in 5'UTR depending on the locations. The regulation of translation by 5'UTR is very complicated.

Multimodal imaging characteristics of congenital grouped hyper- and hypo-pigmented fundus lesions.

BACKGROUND: The imaging characteristics of congenital grouped pigmentation of the retinal pigment epithelium (CGP-RPE) and its non-pigmented variant - grouped congenital albinotic retinal pigment epithelial spots (GCARPES) are poorly defined in the literature. Our case series reports their multimodal imaging characteristics across a spectrum of presentations. METHODS: A retrospective review of patient records was conducted on patients seen at the Centre for Eye Health between January and December 2016. The multimodal imaging findings across four cases is described using optical coherence tomography (OCT), infrared imaging, ultra-widefield imaging, fundus photography and fundus autofluorescence (FAF). RESULTS: Case 1 is a 55-year-old female with a bilateral presentation of CGP-RPE showing typical features. Case 2 is a 28-year-old male with a classical presentation of GCARPES in the left eye. Case 3 is a 33-year-old female with unilateral CGP-RPE and an atypical solitary congenital hypertrophy of the retinal pigment epithelium (CHRPE) in the same eye. Case 4 is a unilateral presentation in an 11-year-old female with unusual characteristics. Ocular imaging characteristics of CGP-RPE lesions varied between patients: OCT showed visible RPE changes in cases 3 and 4 but not case 1. The pattern of FAF and infrared imaging also varied with most lesions displaying a pattern of hypo-autofluorescence, but some central lesions in case 3 exhibited hyper-autofluorescence. All lesions were visible with fundus photography. CONCLUSION: FAF can be helpful in alerting clinicians to the presence of lesions that may be difficult to visualise funduscopically and OCT can be helpful in differentiating between CGP-RPE and its variants from more sinister ocular conditions. All in all, these findings highlight the variable manifestation of CGP-RPE and its variants on multimodal imaging; the diagnosis of CGP-RPE and its variants should remain based on its characteristic funduscopic appearance.

[Identification of a novel c.2633_2634del CT variant of the ADAR gene in a patient with dyschromatosis symmetrica hereditaria].

OBJECTIVE: To explore the genetic etiology of two unrelated patients with dyschromatosis symmetrica hereditaria. METHODS: Variant analysis of the ADAR gene was carried out by Sanger sequencing. RESULTS: Patient 1 was found to harbor a c.2633_2634delCT (p.Ser878fs) in exon 8 of the ADAR gene. The same variant was not found among 100 unrelated individuals. No pathogenic variant of the ADAR gene was found in patient 2. Functional prediction of the ADAR c.2633_2634delCT (p.Ser878fs) variant indicated it to be pathogenic by losing a catalytic structural domain. CONCLUSION: The c.2633_2634delCT (p.Ser878fs) variant of the ADAR gene probably underlies the pathogenesis of DSH in one of the patients.

Seven novel mutations of ADAR in multi-ethnic pedigrees with dyschromatosis symmetrica hereditaria in China.

BACKGROUND: Dyschromatosis symmetrica hereditaria (DSH;OMIM: #127400) is a rare autosomal dominant skin disease of hyperpigmented and hypopigmented macules on the dorsal aspects of the feet and hands. The adenosine deaminase RNA-Specific (ADAR;OMIM: *146920) gene was identified as causing DSH. Although more than 200 mutations are reported, no research has included the pedigrees of ethnic minorities in China. To investigate clinical features and genetic factors among multi-ethnic families, seven multi-ethnic pedigrees with DSH were collected for analysis of hereditary characteristics and ADAR mutations. METHODS: All 15 exons and exon-intron sequences of the ADAR gene were amplified and Sanger sequenced from 25 patients and 36 normal controls from seven multi-ethnic DSH families with 100 healthy normal controls. Seven mutations were analyzed by Polyphen 2, SIFT and Provean. All mutations in ADAR with DSH were reviewed and genetic and clinical features were summarized for analysis. The ADEAMc domain may be a hot spot of ADAR mutations among patients with DSH. RESULTS: Seven novel mutations were identified in seven multi-ethnic pedigrees: c.497delA(p.Arg105fs), c.3352C>T(p.Gln1058*) and c.3722delT(p.Ser1181fs) were found in three Uygur families with DSH; c.1330A>G(p.Val332Met) and c.2702A>T(p.His841Leu) were found in two Kazakh pedigrees and c.1176G>A(p.Lys326Glu) and c.2861G>A(p.Arg892His) in two Hui pedigrees. We summarized 203 different mutations of ADAR from people with DSH. CONCLUSIONS: Seven novel mutations were identified in seven multi-ethnic families with DSH. Our study expands the genetic spectrum of ADAR mutations in DSH.

[Analysis of ADAR gene mutations in two pedigrees affected with dyschromatosis symmetrica hereditaria].

OBJECTIVE: To detect mutations of ADAR gene in two pedigrees affected with dyschromatosis symmetrica hereditaria (DSH). METHODS: Potential mutations of the ADAR gene were analyzed by Sanger sequencing of the probands from both pedigrees. Suspected mutations were validated by Sanger sequencing of other patients from both pedigrees as well as unrelated healthy individuals. RESULTS: A heterozygous nonsense mutation c.1325C>G (p.Ser442Ter) and a novel nonsense mutation c.1498C>T (p.Gln500Ter) were respectively identified in the ADAR gene among all patients from the two pedigrees but not among 200 healthy individuals. CONCLUSION: Mutations of the ADAR gene probably underlie the DSH in the two pedigrees. Above findings have enriched the spectrum of ADAR gene mutation.