Recent advances in understanding inherited disorders of keratinization [version 1; referees: 4 approved]

The ichthyoses are a heterogeneous group of skin diseases characterized by localized or generalized scaling or both. Other common manifestations include palmoplantar keratoderma, erythroderma, recurrent infections, and hypohidrosis. Abnormal barrier function is a cardinal feature of the ichthyoses, which results in compensatory hyperproliferation and transepidermal water loss. Barrier function is maintained primarily by the stratum corneum, which is composed of cornified cells surrounded by a corneocyte lipid envelope and intercellular lipid layers. The lipid components are composed primarily of ceramides. Human genetics has advanced our understanding of the role of the epidermal lipid barrier, and a series of discoveries in animals and humans revealed mutations in novel genes causing disorders of keratinization. Recently, next-generation sequencing has further expanded our knowledge, identifying novel mutations that disrupt the ceramide pathway and result in disorders of keratinization. This review focuses on new findings in ichthyoses caused by mutations involving lipid synthesis or function or both

Genetic investigation of childhood vascular tumor biology reveals pathways for therapeutic intervention [version 1; peer review: 2 approved]

Vascular tumors are neoplasms of endothelial cells, a significant number of which present in childhood. Recent studies have examined the mutational landscape of many subtypes of vascular tumors, identifying mutations primarily within the Ras–mitogen-activated protein kinase (MAPK) pathway and providing a unique opportunity to consider targeted therapeutics. This review will summarize the current understanding of childhood vascular tumor pathobiology

Mutations in KDSR Cause Recessive Progressive Symmetric Erythrokeratoderma

Supplemental Data Supplemental Data include five figures and three tables and can be found with this article online at http://dx.doi.org/10.1016/j.ajhg.2017.05.003. Supplemental Data Document S1. Figures S1–S5 and Tables S1–S3 Download Document S2. Article plus Supplemental Data Download Web Resources 1000 Genomes, http://www.internationalgenome.org/ ANNOVAR, http://annovar.openbioinformatics.org/en/latest/ BWA-MEM, http://bio-bwa.sourceforge.net/index.shtml Database of Genomic Variants, http://dgv.tcag.ca/dgv/app/home dbSNP, https://www.ncbi.nlm.nih.gov/projects/SNP/ Exome Aggregation Consortium (ExAC) Browser, http://exac.broadinstitute.org/ ExonPrimer, https://ihg.helmholtz-muenchen.de/ihg/ExonPrimer.html GenBank, https://www.ncbi.nlm.nih.gov/genbank/ Genome Analysis Toolkit (GATK), https://software.broadinstitute.org/gatk/ Integrative Genomics Viewer (IGV), http://software.broadinstitute.org/software/igv/ OMIM, https://www.omim.org/ SNPmasker, http://bioinfo.ebc.ee/snpmasker/ UCSC Genome Browser, https://genome.ucsc.edu/index.html Variant Effect Predictor, http://useast.ensembl.org/info/docs/tools/vep/index.html The discovery of new genetic determinants of inherited skin disorders has been instrumental to the understanding of epidermal function, differentiation, and renewal. Here, we show that mutations in KDSR (3-ketodihydrosphingosine reductase), encoding an enzyme in the ceramide synthesis pathway, lead to a previously undescribed recessive Mendelian disorder in the progressive symmetric erythrokeratoderma spectrum. This disorder is characterized by severe lesions of thick scaly skin on the face and genitals and thickened, red, and scaly skin on the hands and feet. Although exome sequencing revealed several of the KDSR mutations, we employed genome sequencing to discover a pathogenic 346 kb inversion in multiple probands, and cDNA sequencing and a splicing assay established that two mutations, including a recurrent silent third base change, cause exon skipping. Immunohistochemistry and yeast complementation studies demonstrated that the mutations cause defects in KDSR function. Systemic isotretinoin therapy has achieved nearly complete resolution in the two probands in whom it has been applied, consistent with the effects of retinoic acid on alternative pathways for ceramide generation

Mutations in EDA and EDAR Genes in a Large Mexican Hispanic Cohort with Hypohidrotic Ectodermal Dysplasia

Ectodermal dysplasias (ED) encompass nearly 200 different genetic conditions identified by the lack, or dysgenesis, of at least two ectodermal derivatives, such as hair, nails, teeth, and sweat glands. Hypohidrotic/anhidrotic ED (HED) is the most frequent form of ED and it can be inherited as an X-linked (XL)-HED (MIM 305100), autosomal recessive (AR)-HED (MIM 224900), or autosomal dominant (AD)-HED (MIM 229490) condition. HED is caused by mutations in any of the three ectodisplasin pathway genes: ectodisplasin (EDA), which encodes a ligand for the second gene, the EDA receptor (ectodysplasin A-receptor, EDAR), and EDARADD, an intracellular signaling for this pathway. HED is characterized by a triad of clinical features including absent or diminished eccrine sweat glands, missing and/or malformed teeth, and thin, sparse hair. It also includes dryness of the skin, eyes, airways, and mucous membranes, as well as other ectodermal defects and, in some cases, fever, seizures, and rarely, death. XL-HED is caused by mutations in the EDA gene, located on chromosome Xq12-q13.1, which encodes a signaling molecule of the tumor necrosis factor (TNF) superfamily. AR- and AD-HED are caused by mutations in the EDAR gene, located on chromosome 2q11.q13 or the EDARAssociated Death Domain encoding gene, EDARADD, located on chromosome 1q42-q431. Several mutations in the EDA, EDAR, and EDARADD genes have been described as causing HED in different populations. The XL-HED form is the most common and is responsible for 90% of all HED cases2-6. The three forms of HED are clinically indistinguishable. To date, a comprehensive evaluation of HED in the Mexican Hispanic population has not been undertaken. In the present study, we aimed to characterize the mutations in EDA, EDAR, and EDARADD genes present in Mexican Hispanic patients with HED. Male and female patients (35 families) from different geographical regions of Mexico with features suggestive of HED were enrolled in the study (Fig. 1). Index cases and their parents were screened for missing or malformed teeth, thin or sparse hair, and nail changes; all subjects answered questions about sweating, heat intolerance, fever, seizures, and family history of siblings deceased due to unknown feve