MicroRNA analysis of childhood atopic dermatitis reveals a role for miR-451a.

BACKGROUND: MicroRNAs (miRNAs), important regulators of gene expression, have been implicated in a variety of disorders. The expression pattern of miRNAs in paediatric atopic dermatitis (AD) has not been well studied. OBJECTIVES: We sought to investigate miRNA expression profiles in different blood compartments of infants with AD. METHODS: Small RNA and analysis with the HTG EdgeSeq system were performed to identify differentially expressed miRNAs in peripheral blood mononuclear cells (PBMCs) and plasma of infants with AD vs. age-matched healthy controls, with reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) used for validation and measurement of miRNA targets. Logistic regression models with area under the receiving operating characteristic estimation was used to evaluate the diagnostic potential of chosen miRNAs for AD. RESULTS: RNA sequencing was performed to access miRNA expression profiles in paediatric AD. We identified 10 differentially expressed miRNAs in PBMCs and eight dysregulated miRNAs in plasma of infants with AD compared with controls. Upregulated miRNAs in PBMCs included miRNAs known to be involved in inflammation: miR-223-3p, miR-126-5p and miR-143-3p. Differential expression of only one miRNA, miR-451a, was observed in both PBMCs and plasma of children with AD. Dysregulation of three miRNAs (miR-451a, miR-143-3p and miR-223-3p) was validated in larger numbers of samples and miR-451a was identified as a predictive biomarker for the early diagnosis of the disease. Experimentally verified targets of miR-451a, interleukin 6 receptor (IL6R) and proteasome subunit beta type-8 (PSMB8), were increased in patients with AD, negatively correlated with miR-451a levels and upregulated following inhibition of miR-451a in PBMCs. CONCLUSIONS: In infants with AD, a distinct peripheral blood miRNA signature is seen, highlighting the systemic effects of the disease. miR-451a is uniquely expressed in different blood compartments of patients with AD and may serve as a promising novel biomarker for the early diagnosis of AD.

Mutations in SMARCAD1 cause autosomal dominant adermatoglyphia and perturb the expression of epidermal differentiation-associated genes.

BACKGROUND: Autosomal dominant adermatoglyphia (ADG) is characterized by lack of palmoplantar epidermal ridges. Recently, ADG was found to be caused in one family by a mutation in SMARCAD1, a member of the SNF subfamily of the helicase protein superfamily. OBJECTIVES: To investigate the genetic basis of ADG. METHODS: We used direct sequencing and global gene expression analysis. RESULTS: We identified three novel heterozygous mutations in SMARCAD1 (c.378 + 2T > C, c.378 + 5G > C and c.378 + 1G > A) in a total of six patients. Surprisingly, all four ADG-causing mutations identified to date disrupt a single conserved donor splice site adjacent to the 3' end of a noncoding exon and are predicted to result in haploinsufficiency for a skin-specific isoform of SMARCAD1. These data indicate a pivotal role for the SMARCAD1-skin specific isoform in dermatoglyph formation. In order to better understand the consequences of ADG-associated mutations, we ascertained the global transcription profiles of primary keratinocytes downregulated for SMARCAD1 and of patient-derived keratinocytes. A total of eight genes were found to be differentially expressed in both patient-derived and knocked down keratinocytes. Of interest, these differentially expressed genes have been implicated in epidermal ontogenesis and differentiation, and in psoriasis, which is characterized by abnormal finger ridge patterns. CONCLUSIONS: The present data suggest that ADG is genetically homogeneous and result from perturbed expression of epidermal differentiation-associated genes.

New intragenic and promoter region deletion mutations in FERMT1 underscore genetic homogeneity in Kindler syndrome.

BACKGROUND: Kindler syndrome (KS) is a rare autosomal recessive skin disorder, which was recently reclassified as a subtype of epidermolysis bullosa. Despite the fact that loss-of-function mutations in the FERMT1 gene, encoding kindlin-1, have been shown to cause the syndrome in numerous patients, a small number of typical cases of KS in which FERMT1 mutations could not be identified has raised the possibility that the disorder may be genetically heterogeneous. AIM: To assess two highly consanguineous families with clinical characteristics of KS. RESULTS: In the first family, a hitherto unreported deletion (c.137-140delTAGT) in FERMT1 was detected, which is predicted to lead to premature termination of translation. However, direct sequencing of the coding region of FERMT1 failed to disclose any pathogenic change in the second family. To confirm the possibility that the disease in this family may be due to a mutation in another gene, we used homozygosity mapping, and found that all affected family members share a segment of homozygosity on 20p12.3, spanning the FERMT1 gene. Accordingly, a large and highly unusual deletion (g.-711-1241del) spanning the putative FERMT1 promoter sequence and the first noncoding exon of the gene was found to cosegregate with the disease phenotype in this family, and to prevent transcription of the gene, as attested by the lack of FERMT1 message in the skin of a patient. CONCLUSION: The present data provide evidence in support of genetic homogeneity in KS.

CEDNIK syndrome results from loss-of-function mutations in SNAP29.

BACKGROUND: CEDNIK (cerebral dysgenesis, neuropathy, ichthyosis and keratoderma) syndrome is a rare genodermatosis which was shown 5 years ago in one family to be associated with a loss-of-function mutation in SNAP29, encoding a member of the SNARE family of proteins. Decrease in SNAP29 expression was found to result in abnormal lamellar granule maturation leading to aberrant epidermal differentiation and ichthyosis. OBJECTIVES: To delineate the molecular consequences of disease-causing mutations in SNAP29. METHODS: We used direct sequencing, in vitro mutagenesis and three-dimensional organotypic cell cultures. RESULTS: We identified a novel homozygous insertion in SNAP29 (c.486insA) in two sibs presenting with ichthyosis and dysgenesis of the corpus callosum. In vitro transfection experiments indicated that this mutation results in SNAP29 loss-of-function. Further substantiating this notion, we could replicate histological features typical for CEDNIK syndrome in three-dimensional primary human keratinocyte organotypic cell cultures downregulated for SNAP29. CONCLUSIONS: The identification of a second mutation in SNAP29 in the present study definitely establishes a causal relationship between defective function of SNAP29 and the pleiotropic manifestations of CEDNIK syndrome. Our present and previous data position SNAP29 as an essential component of the epidermal differentiation machinery.