Publications by authors named "Frances J D Smith"

70 Publications

PSENEN Mutation in Coexistent Hidradenitis Suppurativa and Dowling-Degos Disease.

Indian Dermatol Online J 2021 Jan-Feb;12(1):147-149. Epub 2020 Sep 28.

Department of Medical Genetics, Christian Medical College, Vellore, Tamil Nadu, India.

Hidradenitis suppurativa is a chronic relapsing disease with multiple abscesses, nodules, and scars in the apocrine bearing areas. Dowling-Degos is a rare autosomal dominant genodermatosis characterized by multiple hyperpigmented macules or papules in reticulate pattern, affecting mainly the flexures. We report a case of coexisting hidradenitis suppurativa and Dowling-Degos disease in a 31-year-old male in whom mutation analysis revealed a splice site mutation c.62-1G>T.
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http://dx.doi.org/10.4103/idoj.IDOJ_218_20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7982026PMC
September 2020

Skin fragility, woolly hair syndrome with a desmoplakin mutation - a case from India.

Int J Dermatol 2018 09 25;57(9):e73-e75. Epub 2018 Jun 25.

Pachyonychia Congenita Project, Holladay, UT, USA.

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http://dx.doi.org/10.1111/ijd.14096DOI Listing
September 2018

Enamel Anomalies in a Pachyonychia Congenita Patient with a Mutation in KRT16.

J Invest Dermatol 2019 01 25;139(1):238-241. Epub 2018 Sep 25.

Laboratory of Skin Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland, USA. Electronic address:

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http://dx.doi.org/10.1016/j.jid.2018.07.005DOI Listing
January 2019

First Report of Pachyonychia Congenita Type PC-K6a in the Romanian Population.

Maedica (Bucur) 2017 Jun;12(2):123-126

Pachyonychia Congenita Project, Salt Lake City, Utah, USA.

Pachyonychia congenita (PC) is a rare autosomal dominant skin disorder, with unknown prevalence, although it is estimated there are between 2,000 and 10,000 cases of PC worldwide. The International PC Research Registry (IPCRR) has currently identified (as of November 2016) 746 individuals (in 403 families) with genetically confirmed PC. Heterozygous mutations, predominantly missense mutations, in any one of five keratin genes, KRT6A, KRT6B, KRT6C, KRT16, or KRT17 cause PC. The predominant clinical findings include plantar keratoderma, plantar pain and variable dystrophy of some or all toenails and/ or fingernails. Oral leukokeratosis, follicular hyperkeratosis, cysts of various types and natal teeth may also be present. We report the first case of genetically confirmed PC from Romania due to a mutation in KRT6A, p.Arg466Pro.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5649033PMC
June 2017

Management of Plantar Keratodermas.

J Am Podiatr Med Assoc 2017 Sep;107(5):428-435

Plantar keratodermas can arise due to a variety of genetically inherited mutations. The need to distinguish between different plantar keratoderma disorders is becoming increasingly apparent because there is evidence that they do not respond identically to treatment. Diagnosis can be aided by observation of other clinical manifestations, such as palmar keratoderma, more widespread hyperkeratosis of the epidermis, hair and nail dystrophies, or erythroderma. However, there are frequent cases of plantar keratoderma that occur in isolation. This review focuses on the rare autosomal dominant keratin disorder pachyonychia congenita, which presents with particularly painful plantar keratoderma for which there is no specific treatment. Typically, patients regularly trim/pare/file/grind their calluses and file/grind/clip their nails. Topical agents, including keratolytics (eg, salicylic acid, urea) and moisturizers, can provide limited benefit by softening the skin. For some patients, retinoids help to thin calluses but may lead to increased pain. This finding has stimulated a drive for alternative treatment options, from gene therapy to alternative nongenetic methods that focus on novel findings regarding the pathogenesis of pachyonychia congenita and the function of the underlying genes.
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http://dx.doi.org/10.7547/16-043DOI Listing
September 2017

Keratin 6b variant p.Gly499Ser reported in delayed-onset pachyonychia congenita is a non-pathogenic polymorphism.

J Dermatol 2017 12 16;44(12):e312. Epub 2017 Aug 16.

Pachyonychia Congenita Project, School of Life Sciences, University of Dundee, Dundee, UK.

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http://dx.doi.org/10.1111/1346-8138.14001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5724482PMC
December 2017

Keratin 17 Mutations in Four Families from India with Pachyonychia Congenita.

Indian J Dermatol 2017 Jul-Aug;62(4):422-426

School of Life Sciences, Division of Biological Chemistry and Drug Discovery, Dermatology and Genetic Medicine, University of Dundee, Dundee, UK.

Pachyonychia congenita (PC) is a rare autosomal dominant genetic skin disorder due to a mutation in any one of the five keratin genes, , , , , or . The main features are palmoplantar keratoderma, plantar pain, and nail dystrophy. Cysts of various types, follicular hyperkeratosis, oral leukokeratosis, hyperhidrosis, and natal teeth may also be present. Four unrelated Indian families presented with a clinical diagnosis of PC. This was confirmed by genetic testing; mutations in were identified in all affected individuals.
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http://dx.doi.org/10.4103/ijd.IJD_321_16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5527726PMC
August 2017

A novel mutation in a case of pachyonychia congenita from India.

Indian J Dermatol Venereol Leprol 2017 Jan-Feb;83(1):95-98

Centre for Dermatology and Genetic Medicine, Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee, UK; Pachyonychia Congenita Project, Salt Lake City, Utah, USA.

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http://dx.doi.org/10.4103/0378-6323.193620DOI Listing
May 2017

Pachyonychia Congenita: New Classification and Diagnosis.

Indian J Dermatol 2016 Sep-Oct;61(5):567

Pachyonychia Congenita Project, Salt Lake City, UT, USA.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5029248PMC
http://dx.doi.org/10.4103/0019-5154.190110DOI Listing
October 2016

Keratin 12 missense mutation induces the unfolded protein response and apoptosis in Meesmann epithelial corneal dystrophy.

Hum Mol Genet 2016 Mar 11;25(6):1176-91. Epub 2016 Jan 11.

School of Biomedical Sciences, University of Ulster, Coleraine BT52 1SA, Northern Ireland, UK,

Meesmann epithelial corneal dystrophy (MECD) is a rare autosomal dominant disorder caused by dominant-negative mutations within the KRT3 or KRT12 genes, which encode the cytoskeletal protein keratins K3 and K12, respectively. To investigate the pathomechanism of this disease, we generated and phenotypically characterized a novel knock-in humanized mouse model carrying the severe, MECD-associated, K12-Leu132Pro mutation. Although no overt changes in corneal opacity were detected by slit-lamp examination, the corneas of homozygous mutant mice exhibited histological and ultrastructural epithelial cell fragility phenotypes. An altered keratin expression profile was observed in the cornea of mutant mice, confirmed by western blot, RNA-seq and quantitative real-time polymerase chain reaction. Mass spectrometry (MS) and immunohistochemistry demonstrated a similarly altered keratin profile in corneal tissue from a K12-Leu132Pro MECD patient. The K12-Leu132Pro mutation results in cytoplasmic keratin aggregates. RNA-seq analysis revealed increased chaperone gene expression, and apoptotic unfolded protein response (UPR) markers, CHOP and Caspase 12, were also increased in the MECD mice. Corneal epithelial cell apoptosis was increased 17-fold in the mutant cornea, compared with the wild-type (P < 0.001). This elevation of UPR marker expression was also observed in the human MECD cornea. This is the first reporting of a mouse model for MECD that recapitulates the human disease and is a valuable resource in understanding the pathomechanism of the disease. Although the most severe phenotype is observed in the homozygous mice, this model will still provide a test-bed for therapies not only for corneal dystrophies but also for other keratinopathies caused by similar mutations.
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http://dx.doi.org/10.1093/hmg/ddw001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4764196PMC
March 2016

Severe dermatitis, multiple allergies, and metabolic wasting syndrome caused by a novel mutation in the N-terminal plakin domain of desmoplakin.

J Allergy Clin Immunol 2015 Nov 12;136(5):1268-76. Epub 2015 Jun 12.

Clinical Medicine, Trinity College Dublin, Dublin, Ireland; Pediatric Dermatology, Our Lady's Children's Hospital Crumlin, Dublin, Ireland; National Children's Research Centre, Our Lady's Children's Hospital Crumlin, Dublin, Ireland. Electronic address:

Background: Severe dermatitis, multiple allergies, and metabolic wasting (SAM) syndrome is a recently recognized syndrome caused by mutations in the desmoglein 1 gene (DSG1). To date, only 3 families have been reported.

Objective: We studied a new case of SAM syndrome known to have no mutations in DSG1 to detail the clinical, histopathologic, immunofluorescent, and ultrastructural phenotype and to identify the underlying molecular mechanisms in this rare genodermatosis.

Methods: Histopathologic, electron microscopy, and immunofluorescent studies were performed. Whole-exome sequencing data were interrogated for mutations in desmosomal and other skin structural genes, followed by Sanger sequencing of candidate genes in the patient and his parents.

Results: No mutations were identified in DSG1; however, a novel de novo heterozygous missense c.1757A>C mutation in the desmoplakin gene (DSP) was identified in the patient, predicting the amino acid substitution p.His586Pro in the desmoplakin polypeptide.

Conclusions: SAM syndrome can be caused by mutations in both DSG1 and DSP. Knowledge of this genetic heterogeneity is important for both analysis of patients and genetic counseling of families. This condition and these observations reinforce the importance of heritable skin barrier defects, in this case desmosomal proteins, in the pathogenesis of atopic disease.
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http://dx.doi.org/10.1016/j.jaci.2015.05.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4649901PMC
November 2015

Expanding the Phenotypic Spectrum of Olmsted Syndrome.

J Invest Dermatol 2015 Nov 12;135(11):2879-2883. Epub 2015 Jun 12.

Centre for Dermatology and Genetic Medicine, College of Life Sciences and College of Medicine, Dentistry and Nursing, University of Dundee, Dundee, UK. Electronic address:

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http://dx.doi.org/10.1038/jid.2015.217DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4652067PMC
November 2015

PCQoL: A Quality of Life Assessment Measure for Pachyonychia Congenita.

J Cutan Med Surg 2015 Jan-Feb;19(1):57-65. Epub 2015 Jan 1.

Division of Dermatology, Department of Medicine, University of Alberta, Edmonton, ABPachyonychia Congenita Project, Salt Lake City, UTCentre for Dermatology and Genetic Medicine, Division of Molecular Medicine, University of Dundee, Dundee, UKDivision of Dermatology, Department of Medicine, University of Saskatchewan, Saskatoon, SK

Background: Pachyonychia congenita (PC) is a rare but often debilitating, dominantly inherited disorder. New treatments require more accurate instruments for evaluating changes in the quality of life in these patients.

Objectives: This study was undertaken to develop and validate a quality of life questionnaire for PC patients (PCQoL).

Methods: Relevant factors influencing quality of life in PC patients were identified and incorporated into the well-recognized, general questionnaire, the Dermatology Life Quality Index (DLQI), to establish a disease-specific measure, the PCQoL. Classical test theory (CTT) and Rasch analysis (RA) were used to analyze and validate the PCQoL.

Results: CTT analysis established test-retest reliability and internal consistency for the PCQoL. Concurrent and construct validity for the DLQI and the PCQoL were also validated. Chi-square-based infit and outfit statistics indicated that the Rasch model fits the observed responses very well. RA reconfirmed reliability, internal consistency, reasonable homogeneity, construct validity, and the presence of three RA-based domains.

Conclusion: The PCQoL questionnaire is a measure validated by both CTT and RA. It appears to be a valuable tool in measuring quality of life modifications in PC individuals with keratoderma.
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http://dx.doi.org/10.2310/7750.2014.14017DOI Listing
September 2015

Loss-of-function mutations in CAST cause peeling skin, leukonychia, acral punctate keratoses, cheilitis, and knuckle pads.

Am J Hum Genet 2015 Mar 12;96(3):440-7. Epub 2015 Feb 12.

Department of Dermatology, Peking University First Hospital, Beijing 100034, China; Beijing Key Laboratory of Molecular Diagnosis on Dermatoses, Beijing 100034, China; Peking-Tsinghua Center for Life Sciences, Beijing 100871, China. Electronic address:

Calpastatin is an endogenous specific inhibitor of calpain, a calcium-dependent cysteine protease. Here we show that loss-of-function mutations in calpastatin (CAST) are the genetic causes of an autosomal-recessive condition characterized by generalized peeling skin, leukonychia, acral punctate keratoses, cheilitis, and knuckle pads, which we propose to be given the acronym PLACK syndrome. In affected individuals with PLACK syndrome from three families of different ethnicities, we identified homozygous mutations (c.607dup, c.424A>T, and c.1750delG) in CAST, all of which were predicted to encode truncated proteins (p.Ile203Asnfs∗8, p.Lys142∗, and p.Val584Trpfs∗37). Immunohistochemistry shows that staining of calpastatin is reduced in skin from affected individuals. Transmission electron microscopy revealed widening of intercellular spaces with chromatin condensation and margination in the upper stratum spinosum in lesional skin, suggesting impaired intercellular adhesion as well as keratinocyte apoptosis. A significant increase of apoptotic keratinocytes was also observed in TUNEL assays. In vitro studies utilizing siRNA-mediated CAST knockdown revealed a role for calpastatin in keratinocyte adhesion. In summary, we describe PLACK syndrome, as a clinical entity of defective epidermal adhesion, caused by loss-of-function mutations in CAST.
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http://dx.doi.org/10.1016/j.ajhg.2014.12.026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4375526PMC
March 2015

Keratins and skin disease.

Cell Tissue Res 2015 Jun 27;360(3):583-9. Epub 2015 Jan 27.

Centre for Cutaneous Research, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK.

Mutations in keratin genes cause a diverse spectrum of skin, hair and mucosal disorders. Cutaneous disorders include epidermolysis bullosa simplex, palmoplantar keratoderma, epidermolytic ichthyosis and pachyonychia congenita. Both clinical and laboratory observations confirm a major role for keratins in maintaining epidermal cell-cell adhesion. When normal tissue homeostasis is disturbed, for example, during wound healing and cancer, keratins play an important non-mechanical role. Post-translational modifications including glycosylation and phosphorylation of keratins play an important role in protection of epithelial cells from injury. Keratins also play a role in modulation of the immune response. A current focus in the area of keratins and disease is the development of new treatments including small inhibitory RNA (siRNA) to mutant keratins and small molecules to modulate keratin expression.
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http://dx.doi.org/10.1007/s00441-014-2105-4DOI Listing
June 2015

In vivo gene silencing following non-invasive siRNA delivery into the skin using a novel topical formulation.

J Control Release 2014 Dec 30;196:355-62. Epub 2014 Oct 30.

Centre for Dermatology and Genetic Medicine, Division of Molecular Medicine, University of Dundee, Dundee DD1 5EH, Scotland, UK. Electronic address:

Therapeutics based on short interfering RNAs (siRNAs), which act by inhibiting the expression of target transcripts, represent a novel class of potent and highly specific next-generation treatments for human skin diseases. Unfortunately, the intrinsic barrier properties of the skin combined with the large size and negative charge of siRNAs make epidermal delivery of these macromolecules quite challenging. To help evaluate the in vivo activity of these therapeutics and refine delivery strategies we generated an innovative reporter mouse model that predominantly expresses firefly luciferase (luc2p) in the paw epidermis--the region of murine epidermis that most closely models the tissue architecture of human skin. Combining this animal model with state-of-the-art live animal imaging techniques, we have developed a real-time in vivo analysis work-flow that has allowed us to compare and contrast the efficacies of a wide range nucleic acid-based gene silencing reagents in the skin of live animals. While inhibition was achieved with all of the reagents tested, only the commercially available "self-delivery" modified Accell-siRNAs (Dharmacon) produced potent and sustained in vivo gene silencing. Together, these findings highlight just how informative reliable reporter mouse models can be when assessing novel therapeutics in vivo. Using this work-flow, we developed a novel clinically-relevant topical formulation that facilitates non-invasive epidermal delivery of unmodified and "self-delivery" siRNAs. Remarkably, a sustained >40% luc2p inhibition was observed after two 1-hour treatments with Accell-siRNAs in our topical formulation. Importantly, our ability to successfully deliver siRNA molecules topically brings these novel RNAi-based therapeutics one-step closer to clinical use.
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http://dx.doi.org/10.1016/j.jconrel.2014.10.022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4275573PMC
December 2014

Disease classification using clinical and molecular features.

J Dermatol 2014 Oct 9;41(10):949. Epub 2014 Sep 9.

Department of Dermatology, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel.

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http://dx.doi.org/10.1111/1346-8138.12587DOI Listing
October 2014

Desmoglein 1 deficiency results in severe dermatitis, multiple allergies and metabolic wasting.

Nat Genet 2013 Oct 25;45(10):1244-1248. Epub 2013 Aug 25.

Department of Dermatology, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel.

The relative contribution of immunological dysregulation and impaired epithelial barrier function to allergic diseases is still a matter of debate. Here we describe a new syndrome featuring severe dermatitis, multiple allergies and metabolic wasting (SAM syndrome) caused by homozygous mutations in DSG1. DSG1 encodes desmoglein 1, a major constituent of desmosomes, which connect the cell surface to the keratin cytoskeleton and have a crucial role in maintaining epidermal integrity and barrier function. Mutations causing SAM syndrome resulted in lack of membrane expression of DSG1, leading to loss of cell-cell adhesion. In addition, DSG1 deficiency was associated with increased expression of a number of genes encoding allergy-related cytokines. Our deciphering of the pathogenesis of SAM syndrome substantiates the notion that allergy may result from a primary structural epidermal defect.
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http://dx.doi.org/10.1038/ng.2739DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3791825PMC
October 2013

Keratin 9 is required for the structural integrity and terminal differentiation of the palmoplantar epidermis.

J Invest Dermatol 2014 Mar 20;134(3):754-763. Epub 2013 Aug 20.

Division of Molecular Medicine and Centre for Dermatology and Genetic Medicine, Colleges of Life Sciences and Medicine, Dentistry and Nursing, University of Dundee, Dundee, UK. Electronic address:

Keratin 9 (K9) is a type I intermediate filament protein whose expression is confined to the suprabasal layers of the palmoplantar epidermis. Although mutations in the K9 gene are known to cause epidermolytic palmoplantar keratoderma, a rare dominant-negative skin disorder, its functional significance is poorly understood. To gain insight into the physical requirement and importance of K9, we generated K9-deficient (Krt9(-/-)) mice. Here, we report that adult Krt9(-/-)mice develop calluses marked by hyperpigmentation that are exclusively localized to the stress-bearing footpads. Histological, immunohistochemical, and immunoblot analyses of these regions revealed hyperproliferation, impaired terminal differentiation, and abnormal expression of keratins K5, K14, and K2. Furthermore, the absence of K9 induces the stress-activated keratins K6 and K16. Importantly, mice heterozygous for the K9-null allele (Krt9(+/-)) show neither an overt nor histological phenotype, demonstrating that one Krt9 allele is sufficient for the developing normal palmoplantar epidermis. Together, our data demonstrate that complete ablation of K9 is not tolerable in vivo and that K9 is required for terminal differentiation and maintaining the mechanical integrity of palmoplantar epidermis.
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http://dx.doi.org/10.1038/jid.2013.356DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3923277PMC
March 2014

Plectin mutations underlie epidermolysis bullosa simplex in 8% of patients.

J Invest Dermatol 2014 Jan 17;134(1):273-276. Epub 2013 Jun 17.

Department of Dermatology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands. Electronic address:

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http://dx.doi.org/10.1038/jid.2013.277DOI Listing
January 2014

Heterozygous mutations in AAGAB cause type 1 punctate palmoplantar keratoderma with evidence for increased growth factor signaling.

J Invest Dermatol 2013 Dec 6;133(12):2805-2808. Epub 2013 Jun 6.

Dermatology and Genetic Medicine, College of Life Sciences and College of Medicine, Dentistry and Nursing, University of Dundee, Dundee, UK; Department of Dermatology, Ninewells Hospital and Medical School, Dundee, UK. Electronic address:

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http://dx.doi.org/10.1038/jid.2013.243DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3826975PMC
December 2013

Generation and characterisation of keratin 7 (K7) knockout mice.

PLoS One 2013 31;8(5):e64404. Epub 2013 May 31.

Centre for Dermatology & Genetic Medicine, Division of Molecular Medicine, College of Life Sciences, Dentistry & Nursing, University of Dundee, Dundee, United Kingdom.

Keratin 7 (K7) is a Type II member of the keratin superfamily and despite its widespread expression in different types of simple and transitional epithelia, its functional role in vivo remains elusive, in part due to the lack of any appropriate mouse models or any human diseases that are associated with KRT7 gene mutations. Using conventional gene targeting in mouse embryonic stem cells, we report here the generation and characterisation of the first K7 knockout mouse. Loss of K7 led to increased proliferation of the bladder urothelium although this was not associated with hyperplasia. K18, a presumptive type I assembly partner for K7, showed reduced expression in the bladder whereas K20, a marker of the terminally differentiated superficial urothelial cells was transcriptionally up-regulated. No other epithelia were seen to be adversely affected by the loss of K7 and western blot and immunofluorescence microscopy analysis revealed that the expression of K8, K18, K19 and K20 were not altered in the absence of K7, with the exception of the kidney where there was reduced K18 expression.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0064404PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3669307PMC
February 2014

Allele-specific siRNA silencing for the common keratin 12 founder mutation in Meesmann epithelial corneal dystrophy.

Invest Ophthalmol Vis Sci 2013 Jan 17;54(1):494-502. Epub 2013 Jan 17.

School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland BT52 1SA, UK.

Purpose: To identify an allele-specific short interfering RNA (siRNA), against the common KRT12 mutation Arg135Thr in Meesmann epithelial corneal dystrophy (MECD) as a personalized approach to treatment.

Methods: siRNAs against the K12 Arg135Thr mutation were evaluated using a dual luciferase reporter gene assay and the most potent and specific siRNAs were further screened by Western blot. Off-target effects on related keratins were assessed and immunological stimulation of TLR3 was evaluated by RT-PCR. A modified 5' rapid amplification of cDNA ends method was used to confirm siRNA-mediated mutant knockdown. Allele discrimination was confirmed by quantitative infrared immunoblotting.

Results: The lead siRNA, with an IC(50) of thirty picomolar, showed no keratin off-target effects or activation of TLR3 in the concentration ranges tested. We confirmed siRNA-mediated knockdown by the presence of K12 mRNA fragments cleaved at the predicted site. A dual tag infrared immunoblot showed knockdown to be allele-specific, with 70% to 80% silencing of the mutant protein.

Conclusions: A potent allele-specific siRNA against the K12 Arg135Thr mutation was identified. In combination with efficient eyedrop formulation delivery, this would represent a personalized medicine approach, aimed at preventing the pathology associated with MECD and other ocular surface pathologies with dominant-negative or gain-of-function pathomechanisms.
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http://dx.doi.org/10.1167/iovs.12-10528DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3869971PMC
January 2013

Haploinsufficiency for AAGAB causes clinically heterogeneous forms of punctate palmoplantar keratoderma.

Nat Genet 2012 Nov 14;44(11):1272-6. Epub 2012 Oct 14.

Centre for Dermatology and Genetic Medicine, College of Life Sciences and College of Medicine, Dentistry & Nursing, University of Dundee, UK.

Palmoplantar keratodermas (PPKs) are a group of disorders that are diagnostically and therapeutically problematic in dermatogenetics. Punctate PPKs are characterized by circumscribed hyperkeratotic lesions on the palms and soles with considerable heterogeneity. In 18 families with autosomal dominant punctate PPK, we report heterozygous loss-of-function mutations in AAGAB, encoding α- and γ-adaptin-binding protein p34, located at a previously linked locus at 15q22. α- and γ-adaptin-binding protein p34, a cytosolic protein with a Rab-like GTPase domain, was shown to bind both clathrin adaptor protein complexes, indicating a role in membrane trafficking. Ultrastructurally, lesional epidermis showed abnormalities in intracellular vesicle biology. Immunohistochemistry showed hyperproliferation within the punctate lesions. Knockdown of AAGAB in keratinocytes led to increased cell division, which was linked to greatly elevated epidermal growth factor receptor (EGFR) protein expression and tyrosine phosphorylation. We hypothesize that p34 deficiency may impair endocytic recycling of growth factor receptors such as EGFR, leading to increased signaling and cellular proliferation.
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http://dx.doi.org/10.1038/ng.2444DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3836166PMC
November 2012

Generic and personalized RNAi-based therapeutics for a dominant-negative epidermal fragility disorder.

J Invest Dermatol 2012 Jun 8;132(6):1627-35. Epub 2012 Mar 8.

Dermatology and Genetic Medicine, Division of Molecular Medicine, Colleges of Life Sciences and Medicine, Dentistry & Nursing, University of Dundee, Dundee, UK.

Epidermolytic palmoplantar keratoderma (EPPK) is one of >30 autosomal-dominant human keratinizing disorders that could benefit from RNA interference (RNAi)-based therapy. EPPK is caused by mutations in the keratin 9 (KRT9) gene, which is exclusively expressed in thick palm and sole skin where there is considerable keratin redundancy. This, along with the fact that EPPK is predominantly caused by a few hotspot mutations, makes it an ideal proof-of-principle model skin disease to develop gene-specific, as well as mutation-specific, short interfering RNA (siRNA) therapies. We have developed a broad preclinical RNAi-based therapeutic package for EPPK containing generic KRT9 siRNAs and allele-specific siRNAs for four prevalent mutations. Inhibitors were systematically identified in vitro using a luciferase reporter gene assay and validated using an innovative dual-Flag/Strep-TagII quantitative immunoblot assay. siKRT9-1 and siKRT9-3 were the most potent generic K9 inhibitors, eliciting >85% simultaneous knockdown of wild-type and mutant K9 protein synthesis at picomolar concentrations. The allele-specific inhibitors displayed similar potencies and, importantly, exhibited strong specificities for their target dominant-negative alleles with little or no effect on wild-type K9. The most promising allele-specific siRNA, siR163Q-13, was tested in a mouse model and was confirmed to preferentially inhibit mutant allele expression in vivo.
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http://dx.doi.org/10.1038/jid.2012.28DOI Listing
June 2012

Development of allele-specific therapeutic siRNA in Meesmann epithelial corneal dystrophy.

PLoS One 2011 12;6(12):e28582. Epub 2011 Dec 12.

Division of Molecular Medicine, Colleges of Life Sciences and Medicine, Dentistry & Nursing, University of Dundee, Dundee, Scotland.

Background: Meesmann epithelial corneal dystrophy (MECD) is an inherited eye disorder caused by dominant-negative mutations in either keratins K3 or K12, leading to mechanical fragility of the anterior corneal epithelium, the outermost covering of the eye. Typically, patients suffer from lifelong irritation of the eye and/or photophobia but rarely lose visual acuity; however, some individuals are severely affected, with corneal scarring requiring transplant surgery. At present no treatment exists which addresses the underlying pathology of corneal dystrophy. The aim of this study was to design and assess the efficacy and potency of an allele-specific siRNA approach as a future treatment for MECD.

Methods And Findings: We studied a family with a consistently severe phenotype where all affected persons were shown to carry heterozygous missense mutation Leu132Pro in the KRT12 gene. Using a cell-culture assay of keratin filament formation, mutation Leu132Pro was shown to be significantly more disruptive than the most common mutation, Arg135Thr, which is associated with typical, mild MECD. A siRNA sequence walk identified a number of potent inhibitors for the mutant allele, which had no appreciable effect on wild-type K12. The most specific and potent inhibitors were shown to completely block mutant K12 protein expression with negligible effect on wild-type K12 or other closely related keratins. Cells transfected with wild-type K12-EGFP construct show a predominantly normal keratin filament formation with only 5% aggregate formation, while transfection with mutant K12-EGFP construct resulted in a significantly higher percentage of keratin aggregates (41.75%; p<0.001 with 95% confidence limits). The lead siRNA inhibitor significantly rescued the ability to form keratin filaments (74.75% of the cells contained normal keratin filaments; p<0.001 with 95% confidence limits).

Conclusions: This study demonstrates that it is feasible to design highly potent siRNA against mutant alleles with single-nucleotide specificity for future treatment of MECD.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0028582PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3236202PMC
April 2012