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Keratin intermediate filaments constitute the primary cytoskeletal component of epithelial cells. Numerous human disease phenotypes related to keratin mutation remain mechanistically elusive. Our recent crystal structures of the helix 1B heterotetramer from keratin 1/10 enabled further investigation of the effect of pathologic 1B domain mutations on keratin structure. We used our highest resolution keratin 1B structure as a template for homology-modeling the 1B heterotetramers of keratin 5/14 (associated with blistering skin disorders), keratin 8/18 (associated with liver disease), and keratin 74/28 (associated with hair disorder). Each structure was examined for the molecular alterations caused by incorporating pathogenic 1B keratin mutations. Structural modeling indicated keratin 1B mutations can harm the heterodimer interface (R265PK5, L311RK5, R211PK14, I150VK18), the tetramer interface (F231LK1, F274SK74), or higher-order interactions needed for mature filament formation (S233LK1, L311RK5, Q169EK8, H128LK18). The biochemical changes included altered hydrophobic and electrostatic interactions, and altered surface charge, hydrophobicity or contour. Together, these findings advance the genotype-structurotype-phenotype correlation for keratin-based human diseases.

BACKGROUND: Annular epidermolytic ichthyosis (AEI) is a rare autosomal dominant ichthyosis that was recently described in 10 separate families in the English literature. There are no reports on the phenotypic heterogeneity of AEI.
OBJECTIVE: We investigated, for the first time, a large Chinese AEI pedigree exhibiting interfamilial phenotypic heterogeneity.
METHODS: We collected clinical data and DNA from the members of the family, and skin lesions were obtained from two patients with different phenotypes. Skin imaging examinations were performed. Whole-exome sequencing (WES) and Sanger sequencing were used to detect gene mutations.
RESULTS: The characteristic features of granular layer degeneration in the two biopsies were verified via histological methods. The missense mutation c.1436T > C in KRT1 was detected in all nine patients.
CONCLUSIONS: This study demonstrates that AEI may present with different clinical phenotypes and that mutation analysis for suspected cases is necessary to obtain a precise diagnosis.

Epidermolytic palmoplantar keratoderma (EPPK) is characterized by hyperkeratotic lesions on palms and soles. The disorder is caused by mutations of keratin 9 (KRT9) or KRT1 gene.
Epidermolytic palmoplantar keratoderma was diagnosed by physical examination and histopathological analysis in a five-generation Chinese family. Mutation was screened by Sanger sequencing. The palmar expression of multiple cytokeratins were analyzed by tape-stripping and Real-time PCR. Literatures of EPPK with additional symptoms were reviewed.
Affected family members showed diffuse palmoplantar keratosis, with knuckle pads, friction-related lesions and a novel additional symptom of palmar constriction. A heterozygous mutation of c.T491C (p.L164P) of KRT9 was found within the helix initiation motif. The hydrophobic effect was decreased and the initiation of coiled-coil conformation was delayed. The KRT16/KRT6 expression were significantly increased in the patients, especially on the right, indicating activation of stress-response and wound-healing cytokeratins. There were also increased KRT9/KRT2, unchanged KRT10/KRT1, and undetectable KRT14/KRT5 expression. The genetic and phenotypic heterogeneity of EPPK with additional symptoms were summarized by literature review.
The p.L164P mutation of KRT9 caused EPPK with a novel symptom of palmar constriction. The expression of multiple cytokeratins was altered in EPPK patients.

Epidermolytic palmoplantar keratoderma (EPPK) is a rare skin disorder and its pathogenesis and inheritability are unknown.
To investigate the inheritance and pathogenesis of EPPK.
Two EPPK cases occurred in a three-generation Chinese family. Patient-parents trio EPPK was carried out and the identified candidate variants were confirmed by Sanger sequencing.
A heterozygous missense pathogenic variant, c.488G > A (p.Arg163Gln), in the keratin (KRT) 9 gene was detected in the proband and his son via targeted exome sequencing, and then validated by Sanger sequencing. This pathogenic variant cosegregated with the EPPK in extended family members, and was predicted to be pathogenic by SIFT, PolyPhen2, PROVEAN, and Mutation Taster. This heterozygous variation was not evident in 100 healthy controls.
This report describes a KRT9 c.488G > A (p.Arg163Gln) variant causing a diffuse phenotype of Chinese EPPK. The current results broaden the spectrum of KRT9 pathogenic variants responsible for EPPK and have important implications for molecular diagnosis, treatment, and genetic counseling for this family.

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Epidermolytic palmoplantar keratoderma (EPPK) is a rare autosomal dominant skin disorder characterized by diffuse hyperkeratosis on the palms and soles. Whole-exome sequencing (WES) has become a powerful tool for the detection of rare causal variants of Mendelian disorders. However, no causal gene for EPPK in the Uygur population has been identified until now, and no treatment exists than can address the underlying pathology.WES analysis was undertaken on two individuals from a large Uygur EPPK pedigree whose disease locus mapped to 17q21.2 (chr:38994621-39893408) following previous linkage analysis. KRT9 (NM_000226.3:c.487C>T, p.Arg163Trp), and KRT15 (XM_005257346.1:c.212G>T, XP_005257403.1:p.Gly71Val) located in this region, have been identified as two candidate causative genes for EPPK in the Uygur family. Sanger sequencing was conducted on this region in other affected individuals (n = 38) from this family, non-affected individuals (n = 56) from this family and 100 unrelated controls. The missense mutation KRT9 c.487C>T, identified in this large Uygur population, is a potential causative mutation. To date, EPPK has no effective therapy, and siRNA is a potential avenue for EPPK therapy. To investigate this, full-length wild-type Keratin9 (KRT9; pKRT9-WT) and p.Arg163Trp (pKRT9-R163W) were then transfected into HaCaT cells. The small interfering RNAs targeting the KRT9 R163W mutant and wildtype KRT9 were transfected into HaCaT cells, and total RNA isolated at 72 h post-transfection. Quantitative polymerase chain reaction and western blotting were used to analyse the effects of knock-down on KRT9 mRNA and protein levels, respectively. siRNA was shown to specifically inhibit mutant KRT9 mRNA and protein expression (p < 0.01, with 95% confidence limits). Our study suggests that KRT9 is a causal gene for EPPK. This information is helpful for understanding the pathogenesis of EPPK in the Uygur population and raises the possibility of designing a novel siRNA treatment strategy for this population of EPPK patients.

During recent years, inborn errors of human IL-17 immunity have been demonstrated to underlie primary immunodeficiencies with chronic mucocutaneous candidiasis (CMC). Various defects in receptors responsible for sensing of Candida albicans or downstream signalling to IL-17 may lead to susceptibility to Candida infection. While CMC is common in patients with profound T cell immunodeficiencies, CMC is also recognised as part of other immunodeficiencies in syndromic CMC, or as relatively isolated CMC disease. We describe a 40-year-old woman with a clinical picture involving cutaneous bacterial abscesses, chronic oral candidiasis and extensive dermatophytic infection of the feet. By whole exome sequencing, we identified a STAT1-gain-of-function mutation. Moreover, the patient\'s peripheral blood mononuclear cells displayed severely impaired Th17 responses. The patient was treated with antifungals and prophylactic antibiotics, which led to resolution of the infection. We discuss the current knowledge within the field of Th17 deficiency and the pathogenesis and treatment of CMC.

Epidermolytic palmoplantar keratoderma (EPPK) is an autosomal dominant disease characterized by diffuse hyperkeratosis of the epidermis of the palm and sole with an erythematous margin. The Keratin 9 (KRT9) and Keratin 1 genes are responsible for EPPK. Several previous studies have focused on the genetic basis of EPPK; however, genetic anticipation has not yet been reported. We described a four-generation family with EPPK and identified a p.R163W mutation of KRT9. We observed a decrease in the age of onset in three consecutive generations in the family of the proband, indicating possible genetic anticipation in this familial EPPK. Further studies are needed to elucidate the mechanisms of anticipation in EPPK.