A heterozygous null mutation combined with the G1258A polymorphism ofSPINK5causes impaired LEKTI function and abnormal expression of skin barrier proteins

Netherton Syndrome Caused by Heterozygous Frameshift Mutation Combined with Homozygous c.1258A>G Polymorphism in SPINK5 Gene

Netherton syndrome (NS) is a rare autosomal recessive disorder caused by SPINK5 mutations, resulting in a deficiency in its processed protein LEKTI. It is clinically characterized by the triad of congenital ichthyosis, atopic diathesis, and hair shaft abnormalities. The SPINK5 (NM_006846.4): c.1258A>G polymorphism (rs2303067) shows a significant association with atopy and atopic dermatitis (AD), which share several clinical features with NS. We describe an NS patient, initially misdiagnosed with severe AD, who carried the heterozygous frameshift (null) mutation (NM_006846.4): c.957_960dup combined with homozygous rs2303067 in the SPINK5 gene. Histopathological examination confirmed the diagnosis, whereas an immunohistochemical study showed normal epidermal expression of LEKTI, despite the genetic findings. Our results corroborate the hypothesis that haploinsufficiency of SPINK5, in the presence of a SPINK5 null heterozygous mutation in combination with homozygous SPINK5 rs2303067 polymorphism, can be causative of an NS phenotype, impairing the function of LEKTI despite its normal expression. Due to the clinical overlap between NS and AD, we suggest performing SPINK5 genetic testing to search for the SPINK5 (NM_006846.4): c.1258A>G polymorphism (rs2303067) and ensure a correct diagnosis, mainly in doubtful cases.

SPINKs in Tumors: Potential Therapeutic Targets

The serine protease inhibitor Kazal type (SPINK) family includes SPINK1-14 and is the largest branch in the serine protease inhibitor family. SPINKs play an important role in pancreatic physiology and disease, sperm maturation and capacitation, Nager syndrome, inflammation and the skin barrier. Evidence shows that the unregulated expression of SPINK1, 2, 4, 5, 6, 7, and 13 is closely related to human tumors. Different SPINKs exhibit various regulatory modes in different tumors and can be used as tumor prognostic markers. This article reviews the role of SPINK1, 2, 4, 5, 6, 7, and 13 in different human cancer processes and helps to identify new cancer treatment targets.

A novel tumor suppressor SPINK5 targets Wnt/β-catenin signaling pathway in esophageal cancer

Esophageal cancer is one of the most common tumor in the world, and the morbidity rate is as high as 100/100 000 in some parts of China. Therefore, it is important and urgent to explore the pathogenesis of esophageal cancer and find new therapeutic targets for esophageal cancer. In this study, we found that a novel tumor suppressor SPINK5 is significantly reduced in the development of esophageal cancer, and is closely related to the pathological differentiation and lymph node metastasis of esophageal cancer via bioinformatics analysis and esophageal cancer tissue array. Further studies have found that SPINK5 is closely related to Wnt/β‐catenin signaling pathway by bioinformatics analysis and western blot. In esophageal cancer cells, SPINK5 overexpression can inhibit Wnt/β‐catenin signaling pathway. Combined with LiCl or MG‐132 treatment, SPINK5 can inhibit GSK3β phosphorylation and promote β‐catenin protein degradation, thus inhibit Wnt/β‐catenin signaling pathway. In vivo study, SPINK5 overexpression can significantly inhibit the growth of esophageal cancer cells. Our study shows that SPINK5 can inhibit the proliferation, migration, and invasion of esophageal cancer cells by inhibiting Wnt/β‐catenin signaling pathway, and thus plays an important role in the development of esophageal cancer, and may serve as a treatment target of esophageal cancer.

Clinical profiles of pediatric patients with GPP alone and with different IL36RN genotypes

BACKGROUND

IL36RN mutation has been identified as one pathogenesis of generalized pustular psoriasis, but the existence of GPP patients without mutation makes this controversial.

OBJECTIVE

Our study aimed at assessing the differences in clinical profiles of children with GPP, with and without IL36RN mutation.

METHODS

An ambispective case series study involved review of the records of 66 childhood patients with pediatric-onset GPP and without previous psoriasis vulgaris.

RESULTS

c.115+6T>C was the most common mutation in this Chinese population with GPP alone. The age at onset was nearly halved in the homozygotes/compound heterozygotes than in IL36RN-negative patients. Besides a more severe inflammatory progression, three minor signs could prioritize patients with GPP for IL36RN screening (confluent lakes of pus (P=0.002), perianal erosion (P=0.014), and flexural erosion (P=0.007)). More patients with the pathogenic mutation converted to ACH than those without mutation (χ2=4.773, P=0.029). Children with GPP with or without IL36RN mutation responded well to oral low-dose acitretin, but IL36RN-positive cases suffered a much higher half-year recurrence rate after withdrawl of acitretin treatment(χ2=10.370, P=0.001).

CONCLUSIONS

Specific clinical features can remind dermatologists of the necessity of sequencing diagnosis. The mild pustular phenotype of those without mutation may imply the possible role of the epigenetic changes of IL36RN, or other IL36-blockers in the pathogenesis. Pediatric patients with GPP alone, both with and without IL36RN mutation responded well to low-dose acitretin.

Systemic therapy for atopic dermatitis

Systemic therapy for atopic dermatitis (AD) is indicated in patients with severe disease refractory to adequate topical treatment. Currently available drugs aim to decrease inflammation by suppressing and/or modulating immune responses and thus may indirectly improve skin barrier function, resulting in a decrease in clinical signs and symptoms in particular pruritus. Before considering systemic treatment, patient adherence to topical treatment including skin care has to be ensured. The selection of the drug depends on the disease severity, localization, complications, concomitant diseases, and age of the patient, but also on their availability and costs as well as the doctor's experience. Bearing in mind the potential risk of resistance, systemic therapy with antibiotics should be exclusively considered in clinically manifest infections such as in children. Here, we review recently published clinical trials and case reports on systemic therapy of pediatric and adult patients with AD to draw conclusions for clinical practice. Although AD is a common disease, controlled clinical studies investigating the efficacy of systemic drugs are scarce, except for cyclosporine, which has been approved for the therapy of severe AD.

Intercellular skin barrier lipid composition and organization in Netherton syndrome patients

Netherton syndrome (NTS) is a rare genetic skin disease caused by mutations in the serine protease inhibitor Kazal-type 5 gene, which encodes the lympho-epithelial Kazal-type-related inhibitor. NTS patients have profoundly impaired skin barrier function. As stratum corneum (SC) lipids have a crucial role in the skin barrier function, we investigated the SC lipid composition and organization in NTS patients. We studied the SC lipid composition by means of mass spectrometry, and the lipid organization was examined by infrared spectroscopy and X-ray diffraction. Decreased free fatty acid (FFA) chain length and increased levels of monounsaturated FFAs were observed in the SC of NTS patients compared with controls. Furthermore, the level of short-chain ceramides (CERs) was enhanced in NTS patients and a strong reduction in long-chain CER levels was seen in several patients. The changes in lipid composition modified the lipid organization leading to an increased disordering of the lipids compared with the controls. In addition, in a subgroup of patients the organization of the lipid layers changed dramatically. The altered FFA and CER profiles in NTS patients corresponded to changes in the expression of enzymes involved in SC lipid processing. The observed changes in lipid composition, lipid organization, and enzyme expression are likely to contribute to the barrier dysfunction in NTS.

Where genotype is not predictive of phenotype: towards an understanding of the molecular basis of reduced penetrance in human inherited disease

Some individuals with a particular disease-causing mutation or genotype fail to express most if not all features of the disease in question, a phenomenon that is known as 'reduced (or incomplete) penetrance'. Reduced penetrance is not uncommon; indeed, there are many known examples of 'disease-causing mutations' that fail to cause disease in at least a proportion of the individuals who carry them. Reduced penetrance may therefore explain not only why genetic diseases are occasionally transmitted through unaffected parents, but also why healthy individuals can harbour quite large numbers of potentially disadvantageous variants in their genomes without suffering any obvious ill effects. Reduced penetrance can be a function of the specific mutation(s) involved or of allele dosage. It may also result from differential allelic expression, copy number variation or the modulating influence of additional genetic variants in cis or in trans. The penetrance of some pathogenic genotypes is known to be age- and/or sex-dependent. Variable penetrance may also reflect the action of unlinked modifier genes, epigenetic changes or environmental factors. At least in some cases, complete penetrance appears to require the presence of one or more genetic variants at other loci. In this review, we summarize the evidence for reduced penetrance being a widespread phenomenon in human genetics and explore some of the molecular mechanisms that may help to explain this enigmatic characteristic of human inherited disease.

Human involucrin promoter mediates repression-resistant and compartment-specific LEKTI expression

Gene-modified skin grafts, produced through gene transfer to human keratinocyte stem cells, offer the possibility of therapeutic benefit for inherited skin diseases. We have previously described efficient lentiviral vector-mediated gene transfer to keratinocyte stem cells and the generation of human skin grafts for the inherited skin disease, Netherton syndrome, which arises due to mutations in serine protease inhibitor Kazal-type 5 (SPINK5). Vectors incorporating an internal murine retroviral-derived promoter [spleen focus-forming virus (SFFV)] in combination with a codon-optimized SPINK5 transgene supported high levels of reconstitution and robust correction of skin architecture. Subsequent longer-term experiments have uncovered unanticipated silencing phenomena, with loss of SPINK5 gene expression over time. The inadvertent introduction of CpG sites during codon optimization appears to have rendered vectors susceptible to silencing due to methylation across the promoter-transgene boundary. Substitution of the methylation-susceptible SFFV promoter with a 572-bp minimal human involucrin promoter (INVOp), which encodes very few CpG sites, prevented repression of the SPINK5 transgene and resulted in durable and highly compartment-specific reconstitution of lympho-epithelial Kazal-type-related inhibitor (LEKTI) in human skin grafted onto immunodeficient mice. We conclude that skin grafts modified with lentiviral vectors encoding INVOp offer a suitable platform for therapeutic gene therapy in Netherton syndrome, and our experience highlights unanticipated effects of transgene codon optimization.

Ex-vivo gene therapy restores LEKTI activity and corrects the architecture of Netherton syndrome-derived skin grafts

Netherton syndrome (NS) is a debilitating congenital skin disorder caused by mutations in the SPINK5 gene encoding the lymphoepithelial Kazal-type-related inhibitor (LEKTI). It is characterized by defective keratinization, recurrent infections, and hypernatraemic dehydration with a mortality rate of about 10% in the first year of life. Currently, there are no curative treatments for NS. We have developed a HIV-1 based, self-inactivating lentiviral vector to express SPINK5 in keratinocytes as part of an ex-vivo gene therapy strategy for NS. High transduction efficiency was achieved in NS keratinocytes and reconstitution of LEKTI expression was confirmed in previously deficient cells. These genetically corrected keratinocytes were further tested in an in vitro organotypic culture (OTC) system and in vivo mouse/human skin engraftment model. Results showed correction of epidermal architecture in both OTCs and regenerated skin grafts. Importantly, the results from corrected skin grafts indicated that even where detectable LEKTI expression was restored to a limited numbers of cells, a wider bystander benefit occurred around these small populations. As LEKTI is a secreted protein, the genetically modified graft may provide not only an immediate local protective barrier, but also act as a source of secreted LEKTI providing a generalized benefit following ex-vivo gene therapy.