KRT5 Mutations Research Articles

Next-generation sequencing through multigene panel testing for the diagnosis of hereditary epidermolysis bullosa in Chinese population.

Epidermolysis bullosa (EB) is a heritable blistering disorder. We performed a next-generation sequencing-based multigene panel test and successfully predicted 100% of the EB types, including, 36 EB simplex (EBS), 13 junctional EB (JEB), 86 dystrophic EB (DEB), and 3 Kindler EB. Chinese JEB and recessive DEB (RDEB) patients have relatively mild phenotypes; for severe type separately accounts for 45.5% and 23.8%, respectively. We identified 96 novel and 49 recurrent pathogenic variants in 11 genes, although we failed to detect the second mutation in one JEB and five RDEB patients. We identified one novel p.E475K mosaic mutation in the clinically normal mother of one out of 13 EBS patients with KRT5 mutations, one recurrent p.G2034R mosaic mutation, and one novel p.G2043R mosaic mutation in the clinically normal relatives of two out of 19 dominant DEB patients. This study shows that next-generation technology could be an effective tool in diagnosing EB.

Analysis of KRT5 and KRT14 gene mutations and mode of inheritance in Iranian patients with clinical suspicion of Epidermolysis bullosa simplex.

Background: Epidermolysis bullosa simplex is a hereditary skin disorder caused by mutations in several genes such as KRT5 and KRT14 . Skin fragility in basal keratinocytes presence regions led to the cytolysis of epidermis and blistering. Aim of this study was to detect the molecular defects in KRT5 and KRT14 genes hot spots in patients with clinical suspicion of EBS and investigation of their probable genotype-phenotype correlations. Methods: Exons 1 and 6-7 of KRT5 and exons 1 and 4-7 of KRT14 amplification and mutation detection were performed by polymerase chain reaction and Sanger sequencing, respectively. Novel variants pathogenicity evaluated by bioinformatics tools. Results: Nine important variants detected in seven different patients within 6 Iranian families affected by Epidermolysis bullosa simplex, of which four variants were novel. Three patients had a mottled pigmentation phenotype [G96D (p.Gly96Asp) and F97I (p.Phe97Ile) in KRT5 ]. One of them showed a Dowling–Meara phenotype [A417P (p.Ala417Pro) and E477D (p.Glu477Asp) in KRT5 ] and another had a Koebner type phenotype [R397I (p.Arg397Ile) and Q444* (p.Gln444Ter) in KRT5 ]. A novel variant [G92E (p.Gly92Glu) in KRT5 ] in a double heterozygous state with a challenging variant [A413T (p.Ala413Thr) in KRT14 ] identified in one patient with Koebner type phenotype. Also, a previously reported mutation [I377T (p.Ile377Thr) in KRT14 gene] identified in this study. Conclusion: The results of molecular data analysis showed that the most severe phenotypes were associated with mutations in highly conserved regions. In some cases, different inheritance modes were observed.

Notice of withdrawal.

L. Frommherz, J. Küsel, A. Zimmer, J. Fischer, C. Has. Skin fragility caused by biallelic KRT10 mutations: an intriguing form of self-improving epidermolytic ichthyosis https://onlinelibrary.wiley.com/doi/10.1111/bjd.18325 The above article from the British Journal of Dermatology, published online on 6 July 2019 in Wiley Online Library (wileyonlinelibrary.com), and in print and online in issue 182:3 (cover date March 2020) has been withdrawn by agreement between the authors, the journal's Editor-in-Chief, John Ingram, the British Association of Dermatologists, and John Wiley & Sons Limited. The withdrawal has been agreed because consent to publish was not obtained in this case. The authors and the journal sincerely apologize for this oversight. The article is no longer available online in order to protect patient confidentiality.

Ichthyosis with confetti caused by new and recurrent mutations in KRT10 associated with varying degrees of keratin 10 mis-localization

BackgroundIchthyosis with confetti (IWC) is an extremely rare autosomal-dominant genodermatosis characterized by erythroderma with numerous confetti-like pale spots. IWC is caused by mutations in KRT10 (IWC-I) or KRT1 (IWC-II) which affect their tail domains. In IWC-I, the mutations lead to replacement of glycine/serine-rich keratin 10 (K10) tail with arginine- or alanine-rich frameshift motifs, causing K10 mis-localization which might trigger loss of the mutant KRT10 allele via mitotic recombination, leading to genetic reversion. ObjectiveTo investigate mutations in five IWC-I patients and their functional consequences. MethodsWe performed Sanger sequencing of KRT1 and KRT10 in peripheral blood samples of five patients, with highly polymorphic KRT10 SNPs genotyped to confirm loss-of-heterozygosity in the epidermis of pale spots. K10 expression pattern was examined in both patient skin biopsies and HaCaT cells overexpressing mutant KRT10-enhanced green fluorescence protein fusion. ResultsFour novel and one recurrent KRT10 mutations were identified in patient peripheral blood samples but not in the corresponding pale spot epidermis. Two of the mutations, c.1696_1699dupCACA and c.1676dupG, affected residues close to K10 carboxyl terminus and encoded only 3 and 6 arginine residues, which were far fewer than reported previously. Interestingly, imaging analyses for K10 in HaCaT cells overexpressing either of these two mutations and in the corresponding patients' affected skin, showed a remarkably lower level of K10 mis-localization compared to that of other mutations reported in this study. ConclusionsOur findings suggest that the number of arginine residues in the mutant tail may correlate with the level of K10 mis-localization in IWC-I keratinocytes. These results expand the genotypic and phenotypic spectrum of IWC-I.

Mutations in KRT10 in epidermolytic acanthoma.

Epidermolytic acanthoma (EA) is a rare acquired lesion demonstrating a characteristic histopathological pattern of epidermal degeneration referred to as epidermolytic hyperkeratosis (EHK). On histopathological analysis, EA appears nearly identical to inherited EHK-associated dermatoses such as epidermolytic ichthyosis and ichthyosis bullosa of Siemens. While it has been speculated that EA is caused by mutations in KRT10, KRT1, or KRT2 found in these inherited dermatoses, none have yet been identified. Herein, we aim to identify the contributions of keratin mutations to EA. Using genomic DNA extracted from paraffin-embedded samples from departmental archives, we evaluated a discovery cohort using whole-exome sequencing (WES) and assessed remaining samples using Sanger sequencing screening and restriction fragment length polymorphism (RFLP) analysis. DNA from 16/20 cases in our sample was of sufficient quality for polymerase chain reaction amplification. WES of genomic DNA from lesional tissue revealed KRT10 c.466C > T, p.Arg156Cys mutations in 2/3 samples submitted for examination. RFLP analysis of these samples as well as eight additional samples confirmed the mutations identified via WES and identified four additional cases with Arg156 mutations. In sum, 6/11 screened cases showed hotspot mutation in KRT10. Hotspot mutations in the Arg156 position of KRT10, known to cause epidermolytic ichthyosis, also underlie EA.

A Novel Mutation of KRT14 Gene in a Newborn with Epidermolysis Bullosa Simplex (Dowling-Meara Type): Case Report

Epidermolysis bullosa simplex (EBS) is a group of inherited skin diseases characterized by intraepidermal blistering upon mild trauma. They are classified into three major types based on the severity and distribution of blisters, age of onset, and histological findings. These three major types are caused by KRT5 and KRT14 gene mutations. EBS Dowling-Meara (DM) is one of the most severe subtypes which mostly affects neonates. Electron microscopy is a primary diagnostic tool for EBS; however, mutation analysis has recently become more important for its diagnosis, prognosis, genetic counselling, and prenatal diagnosis. Several studies have reported that almost all mutations in EBS-DM patients are found in the highly conserved rod domains of the KRT5 and KRT14 genes and have also demonstrated a genotype-phenotype correlation. Here, we report an EBS-DM case diagnosed by mutation analysis in a newborn and a missense mutation not identified in humans previously.

Report of an autosomal recessive epidermolytic ichthyosis

Epidermolytic ichthyosis (EI) previously named bullous congenital ichthyosiform erythroderma of Brocq or epidermolytic hyperkeratosis (mostly considered as a histological term now) is rare with a variable defect of cornification, clinically characterized by generalized erythema, erosions, scaling, and easily breaking blisters that become less frequent later in life while hyperkeratosis increases. It is usually inherited in an autosomal-dominant fashion and is caused by the mutations in the genes KRT1 and KRT10, coding for the proteins keratin 1 and keratin 10, respectively. To date, only six recessive KRT10 mutations have been shown to cause autosomal-recessive EI, all of which have been found to lead to the complete absence of the keratin 10 protein. To the best of our knowledge, this is the first such case report from India.

307 Homozygous Biallelic KRT5 Mutations in Epidermolysis Bullosa Simplex, Including a Complete Human Keratin 5 “Knock-Out”, in Families with Extensive Consanguinity

Epidermolysis bullosa simplex (EBS) is usually inherited as an autosomal dominant disease due to monoallelic gain-of-function mutations in the KRT5 and KRT14 genes. Although autosomal recessive forms of EBS have been associated with mutations in at least 10 genes, recessive EBS due to homozygous biallelic KRT5 mutations has not been reported previously; it has been hypothesized that it would result in embryonic lethality. We sought the genetic causes of EBS in a cohort of EB patients by performing whole exome sequencing (WES) and using a disease-targeted next-generation sequencing (NGS) panel of 21 genes. The pathogenicity and consequences of the mutations were determined by expression profiling and at tissue and ultrastructural levels. Two pathogenic, homozygous missense variants of KRT5 in two patients with generalized EBS and a homozygous null mutation in a patient who died as a neonate from complications of EB were found. The two missense mutations disrupted keratin 5 expression on immunofluorescence microscopy, and the human “knock-out” of KRT5 showed no RNA and protein expression. Collectively, these findings identify biallelic KRT5 mutations with a phenotypic spectrum varying from mild, localized and generalized to lethal, expanding the genotypic profile of autosomal recessive EBS.

Biallelic KRT5 mutations in autosomal recessive epidermolysis bullosa simplex, including a complete human keratin 5 “knock-out”

Epidermolysis bullosa simplex (EBS) is usually inherited as an autosomal dominant disease due to monoallelic gain-of-function mutations in KRT5 or KRT14. Although autosomal recessive forms of EBS have been associated with mutations in at least 10 genes, recessive EBS due to homozygous biallelic KRT5 mutations has not been reported previously; it has been hypothesized that it would result in prenatal lethality. We sought the genetic causes of EB in a cohort of 512 distinct EB families by performing whole exome sequencing (WES) and using an EB-targeting next-generation sequencing (NGS) panel of 21 genes. The pathogenicity and consequences of the mutations were determined by expression profiling and at tissue and ultrastructural levels. Two pathogenic, homozygous missense variants of KRT5 in two patients with generalized EBS and a homozygous null mutation in a patient who died as a neonate from complications of EB were found. The two missense mutations disrupted keratin 5 expression on immunofluorescence microscopy, and the human “knock-out” of KRT5 showed no RNA and protein expression. Collectively, these findings identify biallelic KRT5 mutations with a phenotypic spectrum varying from mild, localized and generalized to perinatal lethal, expanding the genotypic profile of autosomal recessive EBS.

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.

A KRT16 mutation in the first Chinese pedigree with Pachyonychia congenita and review of the literatures.

Pachyonychia congenita (PC), a rare autosomal dominant disorder, is featured by significant hypertrophic nail, palmoplantar keratoderma, and plantar pain. It is caused by the mutation of KRT6A, KRT6B, KRT6C, KRT16, or KRT17. To identify the gene mutation caused the PC in a Chinese family. Genomic DNA was extracted from peripheral blood samples of five patients and six healthy individuals. Genomic DNA of three patients was sequenced by whole-exome sequencing (WES). Then, exons 6 of KRT16 of all samples were amplified by polymerase chain reaction (PCR), and PCR products were sequenced to identify potential mutations. We identified the proline substitution mutation p.Leu421Pro (c.1262T>C) in the 2B domain of K16 that is associated with PC in a Chinese family. The same mutation was not found in the six healthy individuals of the family. The mutation found in this studyis the first report in China. So far, 25 mutations in KRT16 have been reportedly associated with PC. Twenty-one mutations are located on exon 1, and four mutations on exon 6.

Anex vivoRNAtrans‐splicing strategy to correct human generalized severe epidermolysis bullosa simplex

SummaryBackgroundGeneralized severe epidermolysis bullosa simplex (EBS‐gen sev) is a genetic blistering skin disease in which autosomal dominant mutations in either the keratin KRT5 or KRT14 genes lead to impaired function of the intermediate filament cytoskeleton in the basal epidermis. Here we present an ex vivo RNA trans‐splicing‐based therapeutic approach to correct the phenotype.ObjectivesTo correct a mutation within exon 1 of the KRT14 gene, using a 5′‐trans‐splicing approach, where any mutation within the first seven exons could be replaced by a single therapeutic molecule.MethodsA therapeutic RNA trans‐splicing molecule containing wild‐type exons 1–7 was stably transduced into an EBS patient‐derived keratinocyte line. Trans‐splicing was confirmed via reverse‐transcriptase polymerase chain reaction, Western blotting and immunofluorescence microscopy. Skin equivalents generated from corrected keratinocytes were grafted onto nude mice and analysed about 8 weeks post‐transplantation for regular epidermal stratification, trans‐splicing‐induced green fluorescent protein expression and blistering.ResultsTransplanted skin equivalents generated from trans‐splicing‐corrected patient keratinocytes showed a stable and blister‐free epidermis. KRT14 correction disrupted EBS‐gen sev‐associated proinflammatory signalling, as shown at the mRNA and protein levels. Disruption of the pathogenic feedback loop in addition to overall downregulation of KRT14 expression highlighted the effect of KRT14 correction on the EBS pathomechanism.ConclusionsOur data demonstrate that trans‐splicing‐mediated mRNA therapy is an effective method for the correction of dominantly inherited KRT14 mutations at the transcriptional level. This results in the rescue of the EBS‐gen sev phenotype and stabilization of the epidermis in a xenograft mouse model.

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.

Generalized Dowling-Degos disease with an initiation codon mutation of KRT5 mutation

Generalized Dowling-Degos disease with an initiation codon mutation of KRT5 mutation

775 A new phenotype combining hidradenitis suppurativa with Dowling-Degos disease caused by a founder mutation in PSENEN

Dowling-Degos disease (DDD) is a rare disorder featuring reticulate pigmentation and hair follicular involvement and resulting from mutations in KRT5, POFUT1 and POGLUT1. Hidradenitis suppurativa (HS) is a chronic inflammatory disease of the hair follicle unit which can be caused by mutations in four genes (including PSENEN) encoding the -secretase complex. Both HS and DDD typically involve the flexural areas of the body. During the past 10 years, we encountered 4 patients who presented with clinical features consistent with both DDD and HS and aimed at identifying the genetic cause of coexisting DDD and HS. We initially excluded KRT5, POGLUT1 and POFUT1 mutations in all 4 patients. We then screened PSENEN for pathogenic mutations using Sanger sequencing since this gene was recently reported to be associated with the double phenotype displayed by our patients. We identified in all 4 affected individuals an hitherto unreported heterozygous c.168T>G, p.Y56X mutation in PSENEN. Haplotype analysis confirmed a common ancestral origin for the mutation in all 4 patients. Using qPCR and RNA extracted from patient keratinocytes, we observed a significant decrease in the expression of PSENEN as well as POFUT1 which had previously been implicated in DDD. DDD as well as HS-associated genes have been shown to encode important regulators of Notch signaling. Accordingly, using a reporter assay, we demonstrated decreased Notch activity in patient's keratinocytes. The present data confirm the genetic basis of the combined DDD-HS phenotype and suggest that Notch signaling may play a central role in the pathogenesis of this rare condition.

807 Revertant mosaicism in the first case of recessive epidermolysis bullosa simplex caused by KRT5 mutations

807 Revertant mosaicism in the first case of recessive epidermolysis bullosa simplex caused by KRT5 mutations

178 Cooperation of keratin mutations and posttranslational modifications

The skin fragility disorder Epidermolysis bullosa simplex (EBS) mostly results from KRT5 and KRT14 mutations which cause aggregation of the keratin cytoskeleton and render the skin sensitive to mild trauma, followed by recurrent blisters. The prevalence of more serious disease during warmer summer months in most EBS patients suggests that temperature-sensing mechanisms cooperating with keratin mutations contribute to this phenomenon. In order to dissect the underlying mechanism and to exploit this for a therapy approach, we analyzed several KRT5 and KRT14 mutations in a cell culture based heat stress assay. Hence, we identified a subset of KRT5 mutations forming extensive keratin networks with KRT14 at normal culture conditions but reversible aggregation of the keratin cytoskeleton upon short exposure to elevated temperature. This heat-induced aggregation of the keratin cytoskeleton subsequently led to impaired desmosomes and diminished intercellular adhesion. A phosphoproteomic approach revealed elevated Ser phosphorylation of mutant KRT5, but not KRT14, upon brief heat exposure, indicating the involvement of specific kinases in the heat-induced keratin aggregation. Currently, we are investigating kinase inhibitors to prevent the heat-induced filament collapse. Moreover, parthenolide, a plant sesquiterpene lactone that exerts anti-cancer and anti-inflammatory properties and modulates sirtuin function, was found to affect keratin organization, likely by reducing elevated Lys acetylation of mutant keratins. Most importantly, pre-treatment of a temperature-sensitive KRT5 mutant with parthenolide prevented heat-induced keratin aggregation and strengthened desmosome adhesion. Collectively, we show that keratin mutations promote select posttranslational modifications, partially in combination with elevated temperature. Our assay system and results enable the development of a rational therapy for the improvement of EBS.

Traceless Targeting and Isolation of Gene-Edited Immortalized Keratinocytes from Epidermolysis Bullosa Simplex Patients

Epidermolysis bullosa simplex (EBS) is a blistering skin disease caused by dominant-negative mutations in either KRT5 or KRT14, resulting in impairment of keratin filament structure and epidermal fragility. Currently, nearly 200 mutations distributed across the entire length of these genes are known to cause EBS. Genome editing using programmable nucleases enables the development of ex vivo gene therapies for dominant-negative genetic diseases. A clinically feasible strategy involves the disruption of the mutant allele while leaving the wild-type allele unaffected. Our aim was to develop a traceless approach to efficiently disrupt KRT5 alleles using TALENs displaying unbiased monoallelic disruption events and devise a strategy that allows for subsequent screening and isolation of correctly modified keratinocyte clones without the need for selection markers. Here we report on TALENs that efficiently disrupt the KRT5 locus in immortalized patient-derived EBS keratinocytes. Inactivation of the mutant allele using a TALEN working at sub-optimal levels resulted in restoration of intermediate filament architecture. This approach can be used for the functional inactivation of any mutant keratin allele regardless of the position of the mutation within the gene and is furthermore applicable to the treatment of other inherited skin disorders.

Abstract 2706: KRT16 germline mutation associated with familial syndrome of tylosis with esophageal cancer (TOC)

Abstract Tylosis (palmoplantar keratoderma) with esophageal cancer (TOC) also known as Howel-Evans syndrome has been associated with pathogenic mutations in RHBDF2. A potential TOC family was referred for clinical evaluation at the Family Cancer Assessment Clinic (FCAC) at Huntsman Cancer Institute, Salt Lake City, Utah. Multiple relatives of the proband had hyperkeratosis on the areas of skin associated with pressure and friction, especially the feet, as well as oral leukoplakia. The proband’s father, paternal aunt, paternal grandfather, and paternal great grandfather had been diagnosed with esophageal cancer. Clinical testing was unable to identify a germline mutation in RHBDFR2 that explained the observed phenotype and inheritance pattern. As part of Heritage 1K Project (University of Utah), Pediatric & Adult Cancer Section, we performed whole genome sequencing (WGS) on 5 family members, 4 that were affected with the hyperkeratosis, and 1 unaffected family member, to identify other potential genetic causes for the observed TOC phenotype. We prioritized variants via VAAST (Variant Annotation, Analysis and Search Tool). Reducing our genes of interest to those involved in palmoplantar keratoderma with PHEVOR (Phenotype Driven Variant Ontological Re-ranking Tool), we identified a pathogenic mutation: KRT16 c.379C>T p.Arg127Cys. This mutation is reported in a large palmoplantar keratoderma family (without esophageal cancer) and is listed as pathogenic in Clinvar (www.ncbi.nlm.nih.gov/clinvar). KRT16 c.379C>T p.Arg127Cys was present in each of the affected family members, but not in the unaffected relative. Our analysis is the first of its kind to suggest carriers of pathogenic variants in KRT16 are at-risk for esophageal cancer, and may benefit from esophageal surveillance. Additionally, patients presenting with a family history of esophageal cancer should be considered for germline testing for KRT16 mutations along with RHBDF2 mutations. Citation Format: Erin L. Young, Lance Pflieger, Luke Maese, Trent Fowler, Kinley Garfield, N. Jewel Samadder, Bella Johnson, Clinton C. Mason, Barry Moore, Shawn Ryanearson, Mark Yandell, Wendy Kohlmann, Joshua D. Schiffman. KRT16 germline mutation associated with familial syndrome of tylosis with esophageal cancer (TOC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2706. doi:10.1158/1538-7445.AM2017-2706

Proteomic profiling of Pachyonychia congenita plantar callus

Callus samples from the ball and the arch of the foot, collected on tape circles, were compared by shotgun proteomic profiling. Pachyonychia congenita subjects were sampled who exhibited a mutation in KRT6A, KRT6B, KRT6C, KRT16 or KRT17, and the proteins were digested and analyzed by tandem mass spectrometry. In comparison with samples from unaffected control subjects, those from subjects with KRT6A or KRT16 mutations displayed the most differences in profile from normal, while those from subjects with KRT6C or KRT17 mutations showed few differences from normal. The profiles from subjects with KRT6B mutations were intermediate in protein profile differences. Degree of departure from the normal profile could be estimated by expression of numerous proteins in callus from the ball of the foot that were consistently different. By contrast, the protein profile from the arch of the foot was hardly affected. The results provide a foundation for noninvasive monitoring of the efficacy of treatments with quantitative assessment of departure from the normal phenotype. SignificancePachyonychia congenita is an orphan disease in which the connection between the basic defect (keratin mutation) and debilitating symptoms (severe plantar pain) is poorly understood. Present work addresses the degree to which the protein profile is altered in the epidermis where the severe pain originates. The results indicate that the mutated keratins differ greatly in the degree to which they elicit perturbations in protein profile. In those cases with markedly altered protein levels, monitoring the callus profile may provide an objective measure of treatment efficacy.