Study On Molecular Genetic Mechanisms Of Two Inherited Skin Diseases

Skin, as one of the biggest organs of human, functioned as the protector and regulator against the outside environment. Human skin mainly included two parts:epidermis and the underneath dermis. Hair follicles and sweat glands belonged to skin appendages. This study focused on the epidermis and skin appendages. This essay got two parts:(1) A genetic analysis of sporadic cases with disseminated superficial actinic porokeratosisDisseminated superficial actinic porokeratosis (DSAP) was first described by Cherosky in 1966. DSAP is considered as an autosomal dominantly inherited epidermal keratinization disorder. With the progress of genetic mechanism research, five chromosome loci and seven genes have been linked to DSAP. Although a significant genetic heterogenesis exists in DASP, MVK is believed to be the main causative gene.Six sporadic DSAP cases were collected and identified in the Affiliated Union Hospital of Huazhong University of Science and Technology. DNA sequencing analysis for the entire coding regions of gene MVK in the six sporadic cases were performed directly, and two novel missense mutations were identified, which were c.31CT (P11S) and c.1004G>A (G335D). One previously reported mutation c.1126G>A (G376S) was also confirmed. The MVK protein located differently in the epidermis between the DSAP case and the normal control, which was tested by immunohistochemistry. No significant sub-cellular location differences were observed among all the three mutants and wild-type MVK by immunofluorescence staining. Subtle secondary structure alterations were observed between the G335D mutant and wild-type MVK. The binding energy between G335D and ATP is lower than that of wild type and ATP, which were analyzed by AutoDock. Maybe the stronger binding of ATP with mutated G335D MVK, makes abnormality of MVK function. Western blotting showed that the three mutants were less stable than wild-type MVK in different degrees. Knocking down of MVK by siRNA could induce abnormal apoptosis. This apoptosis got associated with PARP1.(2) A familial genetic analysis of X-linked recessive hypohidrotic ectodermal dysplasiaHypohidrotic ectodermal dysplasia (HED) is one of the most common types of 175 genetic ectodermal dysplasia disorders. HED can be inherited as X-linked recessive, autosomal recessive and autosomal dominant pattern. EDA, EDAR, EDARADD and WNT10A were characterized to be associated with HED. Among these, EDA was considered to be the most common causitive gene for HED.A Chinese family with HED was identified in Xiaogan Central Hospital. Direct DNA sequencing of the entire coding region and exon-intron boundaries of EDA was performed and a novel missense mutation c.T1061>C (L354P) in the TNF-like domain of EDA was identifid. This missense mutation was not present in the unaffected male family members and 168 normal controls. The secondary structure alteration caused by mutation was also analyzed. Maybe the structure alteration interfered the binding of EDA with EDAR, and blocked the cascade signal pathway. For the causitive mutation located in X chromosome, the disorder in this family was defined as X-linked reccesive hypohidrotic ectodermal dysplasia (XLHED).In summary, we focused on two genetic disorders associated with skin and its appendages, which were DSAP and XLHED. Several novel disease-causing mutations were characterized and the mutation spectrum was expanded, which could be a tool in the clinical characterization, genetic counseling and prenatal diagnosis of DSAP and XLHED. Functional analysis was also explored to clarify the pathogenesis, which could be helpful to clinical therapy.