Mutations In KRT1 Research Articles

Clinical and genetic findings in 13 Chinese children with keratinopathic ichthyosis.

Keratinopathic ichthyosis (KPI) represents a group of predominantly autosomal dominant genodermatoses resulting from mutations in the KRT1, KRT2, or KRT10 genes. In KPI, the relationship between genotype and phenotype is complex. To analyze the clinical manifestations and gene mutations in Chinese patients with KPI. Clinical data were collected from 13 children diagnosed with KPI, and peripheral blood DNA samples were extracted from both the patients and their parents Next-generation sequencing was performed using a congenital ichthyosis multi-gene panel, and the selected variants in the patients and their parents were further validated using the Sanger sequencing method. Genetic analysis identified missense mutations in either KRT1 or KRT10 in ten patients exhibiting varying degrees of severity and distinct features of epidermolytic ichthyosis. A missense hotspot mutation in KRT2 was identified in one patient with superficial epidermolytic ichthyosis. Additionally, two truncation mutations in KRT10 were detected, leading to the development of generalized ichthyosiform erythroderma. Ear malformation and ectropion at birth, scalp involvement, and palmoplantar hyperkeratosis were observed as early signs of ichthyosis with confetti. We analyzed the genotype-phenotype correlations in KPI, revealing that the types and locations of different mutations are associated with distinct phenotypic characteristics. Oral acitretin could be considered a treatment option for severe patients at an appropriate dosage and timing.

PA12 A case of pustular psoriasis in epidermolytic ichthyosis: coincidence or common pathway?

Abstract An 8-year-old boy with epidermolytic ichthyosis (EI) due to a heterozygous KRT1 mutation presented with a striking bullous skin eruption. Microbiological swabs were sent, and oral antibiotics were prescribed for suspected bullous impetigo. He deteriorated clinically, developing a fever and more extensive pustular rash reminiscent of generalized pustular psoriasis (GPP). Skin biopsies from two distinct cutaneous sites revealed histology strongly supportive of pustular psoriasis. Oral ciclosporin was commenced in addition to intensive topical emollient therapy. Following widespread desquamation, the pustular eruption fully resolved. Recurrence upon weaning of ciclosporin necessitated the introduction of ustekinumab. The rash remains controlled on this therapy. The EI is caused by heterozygous mutations in KRT1 or KRT10, and presents at birth with erythroderma and widespread skin denudation. The erythema and skin fragility abate in early childhood, giving way to prominent hyperkeratosis. Severe palmoplantar keratoderma is seen in those with KRT1 mutations. The GPP is a rare but life-threatening condition characterized by sterile pustules with or without systemic involvement. Interleukin (IL)-36-mediated inflammatory signalling plays a pathogenic role, as evidenced by loss of function mutations in IL36RN, which encodes an IL-36 receptor antagonist (Marrakchi S, Guigue P, Renshaw BR et al. Interleukin-36-receptor antagonist deficiency and generalized pustular psoriasis. N Engl J Med 2011; 365:620–8), and the efficacy of IL-36 receptor inhibitor spesolimab in a recent phase II trial. Both EI and GPP are rare, and the confluence of these entities in this case is striking. Four other cases in the literature describe a GPP-like eruption in patients with congenital ichthyoses. The coexistence of these conditions might be explained by their immunological profiles. Studies of the skin of patients with congenital ichthyoses have shown immune dysregulation with T helper 17/IL-23 skewing, and upregulation of associated inflammatory cytokines, including IL-36γ. The latter encodes for an IL-36 receptor agonist (Paller AS, Renert-Yuval Y, Suprun M et al. An IL-17-dominant immune profile is shared across the major orphan forms of ichthyosis. J Allergy Clin Immunol 2017; 139:152–65). Thus, increased IL-36 receptor agonist activity in congenital ichthyosis could theoretically lead to GPP in genetically predisposed individuals with already upregulated IL-36 receptor-mediated signalling.

Nonsense mutations in KRT1 caused recessive epidermolytic palmoplantar keratoderma with knuckle pads

Epidermolytic palmoplantar keratoderma (EPPK) is characterized by diffuse hyperkeratosis affecting palms and soles with suprabasal epidermolysis or vacuolar degeneration histopathologically. The disorder is caused by heterozygous mutations in KRT9 or KRT1. Dominant-negative mutations in KRT1 could also result in epidermolytic ichthyosis with EPPK, a more severe entity affecting the entire body. To investigate the genetic basis and pathogenesis of two unrelated patients with EPPK and knuckle pads, both of whom were born to consanguineous parents of Chinese origin. Next-generation sequencing was applied to the two patients using genomic DNA extracted from peripheral blood. Quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR), immunofluorescence (IF) staining and Western blot (WB) were employed to evaluate mRNA and protein expression level. Ultrastructural changes of skin lesion were analysed using transmission electron microscopy. Two novel homozygous mutations, c.457C>T (p.Gln153*) and c.33C>G (p.Tyr11*) in KRT1, were identified in patients 1 and 2 respectively. The nonsense mutations were predicted to result in nonsense-mediated mRNA decay and absence of keratin 1, which was confirmed in the skin lesions from patient 1. Upregulated keratin 2 was detected both in the affected and unaffected skin samples from patient 1, while the protein abundance and distribution pattern of keratin 10 remained unchanged. An aberrant and clumped staining pattern of keratin 9 was noted in the palmar skin of patient 1. Homozygous 'knockout' mutations in KRT1 resulted in EPPK with knuckle pads rather than epidermolytic ichthyosis. We speculated that sparing of non-acral skin might be due to compensatory effect of keratin 2 upregulation by forming heterodimer with keratin 10.

First Case of KRT2 Epidermolytic Nevus and Novel Clinical and Genetic Findings in 26 Italian Patients with Keratinopathic Ichthyoses.

Keratinopathic ichthyoses (KI) are a clinically heterogeneous group of keratinization disorders due to mutations in KRT1, KTR10, or KRT2 genes encoding keratins of suprabasal epidermis. Characteristic clinical features include superficial blisters and erosions in infancy and progressive development of hyperkeratosis. Histopathology shows epidermolytic hyperkeratosis. We describe the clinical, histopathological, and molecular findings of a series of 26 Italian patients from 19 unrelated families affected with (i) epidermolytic ichthyosis due to KRT1 or KRT10 mutations (7 and 9 cases, respectively); (ii) KTR10-mutated ichthyosis with confetti (2 cases); (iii) KRT2-mutated superficial epidermolytic ichthyosis (5 cases); and (iv) KRT10-mutated epidermolytic nevus (2 cases). Of note, molecular genetic testing in a third case of extensive epidermolytic nevus revealed a somatic missense mutation (p.Asn186Asp) in the KRT2 gene, detected in DNA from lesional skin at an allelic frequency of 25% and, at very low frequency (1.5%), also in blood. Finally, we report three novel dominant mutations, including a frameshift mutation altering the C-terminal V2 domain of keratin 1 in three familiar cases presenting a mild phenotype. Overall, our findings expand the phenotypic and molecular spectrum of KI and show for the first time that epidermolytic nevus can be due to somatic KRT2 mutation.

Bullous diseases caused by KRT1 gene mutations: from epidermolytic hyperkeratosis to a novel variant of epidermolysis bullosa simplex.

IntroductionMutations in the KRT1 gene encoding keratin 1 cause epidermolytic hyperkeratosis characterized by blistering in the neonatal period followed by ichthyotic hyperkeratosis in childhood and adolescent life. We observed a spectrum of clinical manifestations of blistering disorders caused by different mutations in the same KRT1 gene.AimTo analyse the phenotypic spectrum of blistering disorders caused by the KRT1 mutations.Material and methodsFour patients with an epidermal barrier defect manifesting as blistering with the KRT1 mutations were included to the study. The clinical course of the disease was analysed, histology, immunofluorescence and electron microscopic examinations were performed.ResultsAn adult patient with severe ichthyosis with p.Asn188Lys mutation in exon 1 of KRT1 who occasionally develops blisters in adolescence represents epidermolytic hyperkeratosis, a newborn child who died 4 days after birth due to disruption of the epidermal barrier (extensive blister and erosions) with mutation p.Ser193Pro in the KTR1 gene and two adult sisters harbouring heterozygous mutation c.591+1A>G in the KRT1 gene who present superficial blisters induced by mild trauma from the birth up to adolescent life without ichthyosis suggesting the diagnosis of epidermolysis bullosa simplex. Histopathology in all adult patients showed cytoplasm disruption in keratinocytes of the stratum spinosum with keratohyalin granule-like structures and, on the ultrastructural level, the presence of keratin clumping confirming the pathology of keratin intermediate filaments.ConclusionsThis study extends the knowledge of the clinical spectrum for the KRT1 gene mutations. This is the first description of familial dominant epidermolysis bullosa simplex linked to the KRT1 mutation.

Gene Editing–Mediated Disruption of Epidermolytic Ichthyosis–Associated KRT10 Alleles Restores Filament Stability in Keratinocytes

Epidermolytic ichthyosis is a skin fragility disorder caused by dominant-negative mutations in KRT1 or KRT10. No definitive restorative therapies exist that target these genetic faults. Gene editing can be used to efficiently introduce frameshift mutations to inactivate mutant genes. This can be applied to counter the effect of dominantly inherited diseases such as epidermolytic ichthyosis. In this study, we used transcription activator-like effector nuclease technology, to disrupt disease-causing mutant KRT10 alleles in an exvivo cellular approach, with the intent of developing a therapy for patients with epidermolytic ichthyosis. A transcription activator-like effector nuclease was designed to specifically target a region of KRT10, upstream of a premature termination codon known to induce a genetic knockout. This proved highly efficient at gene disruption in a patient-derived keratinocyte cell line. In addition, analysis for off-target effects indicated no promiscuous gene editing-mediated disruption. Reversion of the keratin intermediate filament fragility phenotype associated with epidermolytic ichthyosis was observed by the immunofluorescence analysis of correctly gene-edited single-cell clones. This was in concurrence with immunofluorescence and ultrastructure analysis of murine xenograft models. The efficiency of this approach was subsequently confirmed in primary patient keratinocytes. Our data demonstrate the feasibility of an exvivo gene-editing therapy for more than 95.6% of dominant KRT10 mutations.

Novel Splice-Site Mutation of KRT1 Underlies Diffuse Palmoplantar Keratoderma in a Large Chinese Pedigree.

To identify potential causative gene mutations in a large Han Chinese pedigree with diffuse nonepidermolytic palmoplantar keratoderma (NEPPK). We enrolled 11 patients and 8 healthy individuals from a pedigree with NEPPK and 100 randomly selected healthy controls. Biopsy samples were obtained from the proband. Genomic DNA was extracted from a peripheral blood sample from each participant. Mutation detection via polymerase chain reaction and Sanger sequencing of relevant potential causative genes, including KRT1, KRT6C, KRT10, KRT16, AQP5, and SERPINB7, was performed. Comparisons were made between sequencing outcomes and currently available reference genome databases, including HGMD Pro, Pubmed, 1000 Genomics, and dbSNP. Histological findings, clinical features, and medical history were in accordance with the diagnosis of diffuse NEPPK. We identified a novel splice-site mutation c.1255-1G > C in intron 6 of KRT1 in all individuals with NEPPK in the pedigree. Diffuse NEPPK is a relatively rare subtype of palmoplantar keratoderma. The results of this study expand the spectrum of KRT1 mutations in diffuse NEPPK and provide insights into the understanding of its underlying pathological mechanisms and phenotype-genotype correlations.

Novel and recurrent mutations in keratin 1 cause epidermolytic ichthyosis and palmoplantar keratoderma.

Mutations in keratin genes underlie a variety of epidermal and nonepidermal cell-fragility disorders, and are the genetic basis of many inherited palmoplantar keratodermas (PPKs). Epidermolytic PPK (EPPK) is an autosomal dominant disorder that can be due to mutations in the keratin 1 gene, KRT1. Epidermolytic ichthyosis (EI), the major keratinopathic ichthyosis, is characterized by congenital erythroderma, blistering and erosions of the skin. Causative mutations in KRT1 and KRT10 have been described, with PPK being present primarily in association with the former. We report four unrelated cases (one with sporadic EI and three with autosomal dominant PPK), due to two novel and two recurrent KRT1 mutations. Mutations in KRT1 are not only scattered throughout the keratin 1 protein, as opposed to being clustered, but can result in a range of phenotypes as further confirmed by these mutations, giving a complex genotype/phenotype pattern.

Epidermolytic Ichthyosis Sine Epidermolysis

Epidermolytic ichthyosis (EI) is a rare disorder of cornification caused by mutations in KRT1 and KRT10, encoding two suprabasal epidermal keratins. Because of the variable clinical features and severity of the disease, histopathology is often required to correctly direct the molecular analysis. EI is characterized by hyperkeratosis and vacuolar degeneration of the upper epidermis, also known as epidermolytic hyperkeratosis, hence the name of the disease. In the current report, the authors describe members of 2 families presenting with clinical features consistent with EI. The patients were shown to carry classical mutations in KRT1 or KRT10, but did not display epidermolytic changes on histology. These observations underscore the need to remain aware of the limitations of pathological features when considering a diagnosis of EI.

Expanding the Mutation Spectrum of Ichthyosis with Confetti

Ichthyosis with confetti is a rare, autosomal dominant disorder caused by frameshift mutations in KRT10 or KRT1 and characterized by the development of white, genetically revertant macules in red, diseased skin. All cases result from mutations affecting the tail domains of keratin-10 or keratin-1, and Suzuki etal. expand the mutation spectrum for ichthyosis with confetti caused by mutations in KRT1, showing that a polyarginine frameshift in the keratin-1 tail can also cause this disorder.

Ichthyosis hystrix Lambert type and Curth-Macklin type are a single entity with affected (KRT1 mutation) or unaffected (KRT10 mutation) palms and soles?

Ichthyosis hystrix Lambert type (IHL) and Curth-Macklin type (IHCM) are very rare conditions characterised by striking hyperkeratotic lesions. They differ from epidermolytic ichthyosis, referred to as “IH Brocq type” in earlier reports by the absence of blister formation clinically and the presence of perinuclear tonofilament shells ultrastructurally. In IHCM, the palms/soles are affected, which is not the case in IHL [1-3]. To date, there have been four reports of KRT1 mutations in IHCM [4-7], [...]

Molekularne podłoże keratynopatii

Keratin disorders are a group of rare bullous skin diseases. They are caused by mutations in genes encoding keratins – the main structural proteins of intermediate filament cytoskeleton of epithelial cells and also one of the major components of hair and nails. Different pairs of keratins are the expressed depending on the skin layer, thus variability in the course of keratinopathies is observed. This disorders are inherited in autosomal dominant pattern mostly. Mutations occur in different regions of the keratin genes. In most of these diseases correlation between the location of mutations, and the severity of clinical symptoms can be observed. The most common keratin disorder is epidermolysis bullosa simplex (EBS), which is caused by mutations in KRT5 and KRT14. These genes are expressed in basal layer of epidermal cells. Depending on the effect of the molecular defect in the protein, EB simplex can phenotype of EBS may be highly different - from mild and localized forms, to severe and generalized. Another disease from this group is epidermolytic ichthyosis, which is caused by mutations in KRT1 and KRT10, expressed in epidermal suprabasal cell layer. This paper contains an overview of selected keratin disorders in terms of their molecular pathology. Beside those mentioned above, ichthyosis bullosa of Siemiens, pachyonychia congenita, and Dowling-Degos disease are also described.

A Unique Pattern of Dyskeratosis Characterizes Epidermolytic Hyperkeratosis and Epidermolytic Palmoplantar Keratoderma

Hereditary skin diseases that are characterized ultrastructurally by intracellular clumpings of keratin tonofilaments, such as Darier disease and Ichthyosis Hystrix of Curth-Macklin, display epidermal dyskeratosis also histologically. Epidermolytic hyperkeratosis (EHK) and epidermolytic palmoplantar keratoderma (Voerner type) (EPPK) are 2 types of autosomal dominant keratodermas, which are also characterized ultrastructurally by intracellular clumpings of tonofilaments but usually without a clear description of histological dyskeratosis. The main aim of the present study was to characterize the histologic signs of keratin aggregation and clumping in the involved epidermis of EHK and EPPK. Two cases of EHK caused by KRT1 mutations and 4 cases of EPPK caused by KRT9 mutations were studied. The biopsies were obtained mostly from the involved skin of the palm. All 6 biopsies were studied histologically, and 4 biopsies (2 EHKs and 2 EPPKs) were also studied ultrastructurally. All 6 cases displayed the characteristic histological epidermolytic changes. In addition, intracytoplasmic and perinuclear eosinophilic homogenizations and round to oval eosinophilic inclusions were identified with varying frequencies in the involved epidermis of all 6 cases. These findings, which were more prominent in the EHK cases, corresponded most likely to the intracytoplasmic aggregates of tonofilaments and to the large round to oval dense clumps of tonofilaments, which were observed ultrastructurally. In conclusion, varying degrees of dyskeratosis are frequently present in EHK and EPPK and should be considered to be a histological characteristic of these disorders.

Splice Site and Deletion Mutations in Keratin (KRT1 and KRT10) Genes: Unusual Phenotypic Alterations in Scandinavian Patients with Epidermolytic Hyperkeratosis

Epidermolytic hyperkeratosis is a rare autosomal dominant inherited skin disorder caused by keratin 1 or keratin 10 mutations. Keratins are major structural proteins of the epidermis, and in keratinocytes committed to terminal differentiation the intermediate filaments are composed of keratin 1 and keratin 10 heterodimers. The majority of reported mutations (86.6%) are heterozygous single point mutations and most of these are located in the 1A and 2B regions of the highly conserved keratin alpha-helical rod domain. We have studied eight Scandinavian families with epidermolytic hyperkeratosis and identified three point mutations, two codon deletions, two splice site mutations, and a complex deletion/insertion. Two of the point mutations were in the KRT1 gene (F191C and K177N) and the other was in KRT10 (L453P). All three patients had associated palmoplantar keratoderma. The splice site mutations in KRT1 both caused a large deletion removing 22 codons (delta176-197) from the 1A helical domain. Codon deletions were found in KRT1 (delta170-173) and in KRT10 (delta161-162) in two patients with a severe phenotype. A final patient had a more complex mutation with a large deletion (442 bp) together with a large insertion (214 bp) of unknown origin that caused deletion of exon 6 in KRT1. In conclusion, we have found eight novel keratin mutations that cause epidermolytic hyperkeratosis with differing phenotypes. Even when a large part of keratin 1 (46 amino acids) is deleted, surprisingly mild phenotypes can result, suggesting that genotype-phenotype relationships in epidermolytic hyperkeratosis are complex and do not solely depend on the type of mutation but also depend on interactions between the behavior of the mutant protein and the cellular environment.

Two Cases of Primarily Palmoplantar Keratoderma Associated with Novel Mutations in Keratin 1

Mutations in keratin 1 were initially described in the classical form of bullous congenital ichthyosiform erythroderma (also known as epidermolytic hyperkeratosis). More recently the range of phenotypes associated with mutations in this gene has been extended to include annular ichthyosiform erythroderma and mild epidermolytic palmoplantar keratoderma. Here we present two novel mutations in the keratin 1 gene (KRT1): a 5' donor splice site mutation in exon 1 (591 + 2T > A) that predicts a 22 amino acid in-frame deletion in the keratin 1 1A domain; and an in-frame deletion in exon 7 (1376del24) that predicts a foreshortened 2B coiled-coil domain of keratin 1. In each case these mutations are associated with palmoplantar keratoderma and mild ichthyosis, largely limited to the flexural areas. These mutations appear to have a less damaging effect than previously reported mis-sense mutations sited in the helix boundary motifs. This report extends the range of phenotypes associated with mutations in KRT1.

Phenotypic/genotypic correlations in patients with epidermolytic hyperkeratosis and the effects of retinoid therapy on keratin expression.

Dominant-negative mutations in the KRT1 and KRT10 genes cause epidermolytic hyperkeratosis, a rare form of ichthyosis sometimes associated with palmoplantar keratoderma. Although there is no permanent cure, some patients improve on retinoid therapy. More knowledge is needed, however, about the mechanism of action of retinoids and the genotypic/phenotypic correlations in this disease. Thirteen patients from 10 families with generalized disease and 2 sporadic patients with nevoid lesions were studied, probably representing most of the patients in Sweden and Norway. All patients, except one nevoid case, were known to have KRT1 or KRT10 mutations. Those with mutated keratin 1 (K1) invariably had associated keratoderma (n=6). In contrast, only 1 of 7 patients with K10 mutations had this problem (p = 0.0047). Five out of 6 patients with KRT10 mutations benefited from treatment with oral acitretin (5-25mg/day) or topical tretinoin/tazarotene, but none of the patients with KRT1 mutations derived any benefit. Quantitative analysis of K1 and K10 mRNA in skin biopsies obtained before and after retinoid therapy (n=8) showed no consistent down-regulation of mutated keratin that would explain the therapeutic outcome. Instead, the mRNA expression of K2e (a normal constituent of the upper epidermis) diminished especially in nonresponders. In contrast, K4 mRNA and protein (marker of retinoid bioactivity in normal epidermis) increased in almost all retinoid-treated patients. In conclusion, our study confirms a strong association between KRT1 mutations and palmoplantar keratoderma. Retinoid therapy is particularly effective in patients with KRT10 mutations possibly because they are less vulnerable to a down-regulation of K2e, potentially functioning as a substitute for the mutated protein in patients with KRT1 mutations.