A Study On Gene Mutations And Related Pathogenic Mechanism Of Hereditary Pigmentary Skin Disorders

BACKGROUND:Lentiginosis can be occasionally encountered in clinical practice. It is characterized with brown patches with various sizes. It can be the skin presentation of several genetically involved syndromes and can also be an idiopathic skin disorder. Familial generalized lentiginosis usually presented with generalized lentiginosis, lacking of systemic involvement. The disease was considered to be autosomal dominant inheritance and was scarce reported. The pathogenicity is also unknown. Exome sequencing is widely used for detection of pathogenic gene in rare hereditary disease since 2005. This method produces relatively smaller data and higher positive diagnostic rate.OBJECTIVE:This research intended to detect the pathogenic gene in a pedigree diagnosed as familial generalized lentiginosis and studied the expression status of the candidate gene in cutaneous tissue.METHODS:Clinical data and family pedigree were collected. Genomic DNA was extracted with standard technique. Exome sequencing was completed in 2 patients and 1 normal control. With data analysis, interpretation and co-segregating analysis, we obtained the candidate gene. We analysed the candidate gene in 2 spordic generalized lentigosis and screened the identified mutation in 200 normal controls. Then we conducted the immunohistochemistry, immunofluorescent staining and Western Blot in both the cutaneous tissue of the patient and the normal control.RESULTS:Mutation in EPHB1 gene co-segregated with disease. The mutation was predicted to be damaging in several function predict softwares and was absent in multiple gene database. The mutation was also not detected within 200 normal people. Immunohistochemistry, immunofluorescent staining and Western Blot all revealed the expression of the EPHB1 gene was higher in skin lesion than in normal control. But we fail to detect the mutation in 2 sporadic cases of generalized lentignosis. The muatation also showed a frequency in ExAC database, which was higher than the disease incidence.CONCLUSION:The EPHB1 gene could not be defined as the candidate gene for familial generalized lentiginosis. EPHB1 gene might involve in pathogenesis of pigmentary dermatosis.BACKGROUND:The dyschromatoses are a group of disorders characterized by simultaneous occured hyperpigmented macules admixed with hypopigmented macules. The dyschromatoses usually limits to skin, with rare systemic involvement. Dyschromatosis universalis hereditaria and dyschromatosis symmetrica hereditaria are two classic types of dyschromatoses. Clinical and histological presentations are similar in these two diseases. But with distinct pathogenic genes, genetic diagnosis is critical in differential diagnosis. Targeted gene sequencing is efficient in genetic diagnosis of groups of highly heterogeneous diseases, yet the reports about its application in pigmentary skin disorders are limited.OBJECTIVE:This research intended to identify the pathogenic mutations in a group of patients who were clinically diagnosed as dyschromatosis universalis hereditaria by targeted gene sequencing, and further validated that this techonology was sufficient and cost-effective in genetic diagnosis of herediatary pigmentary disorders.METHODS:8 patients initially diagnosed with DUH from 7 pedigrees were included. Genomic DNA was extracted by standard procedure. Targeted genes were captured by Nimbtegen sequence capture array and later sequenced by Hiseq2500. All mutations detected on ADARl and ABCB6 genes were analyzed according to the frequency in control database, the mutation types, and the published evidence to determine the pathogenicity.RESULTS:Family pedigree and clinical presentations were reported in 3 patients from two Chinese families who were genetically diagnosed. All 3 patients have prominent cutaneous dyschromatoses involving the whole body without systemic complications. Different pathogenic genes in these patients with similar phenotype were identified, one novel mutation on ADAR1 (c.1325C>G) and one recurrent mutation in ABCB6 (c. 1270T>C), which successfully distinguished two diseases with the similar phenotype.CONCLUSION:Skin lesion of untypical dyschromatosis symmetrica hereditaria could involve the trunk, mimicking dyschromatosis universalis hereditaria.Targeted genes sequencing is time and cost friendly compared with traditional Sanger sequencing and could be an effective tool for molecular diagnosis in pigmentary skin diseases.BACKGROUND:Dyschromatosis symmetrica hereditaria is a rare pigmentary genodermatosis, which is autosomal dominant inheritance with high penetrance. Patients show a mixture of hyperpigmented and hypopigmented macules distributed on the face and the dorsal aspects of the extremities. The disease is caused by mutation in adenosine deaminase acting on RNA1 (ADAR1) gene.OBJECTIVE:The research intended to identify the causal mutation in ADAR1 gene in 5 patients with DSH.METHODS:Peripheral blood samples were collected from the patients. Genomic DNA was isolated by the standard method. All exons of ADAR1 and their flanking intronic sequences were polymerase chain reaction (PCR)-amplified and the PCR products were subjected to direct sequencing.RESULTS:We identified five causal mutations in the patients with DSH,2 of them were novel and 3 of them were recurrent. All mutations located on exon, affecting structure and function of the protein.CONCLUSTION:We identified the causal mutations in patients with DSH.