1
|
Ting T, Yiwen C, Jianquan C, Chao L, Shengjing X, Min Z, Fang C. PP2Acα regulates epidermal cell proliferation via the EGFR/AKT/mTOR pathway in psoriasis-like skin lesions caused by PPP2CA deficiency. Exp Dermatol 2022; 31:1154-1164. [PMID: 35298048 DOI: 10.1111/exd.14567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 03/11/2022] [Accepted: 03/14/2022] [Indexed: 11/30/2022]
Abstract
Psoriasis, a common skin disease, endangers human physiological and mental health; however, its pathogenesis remains unclear. Keratinocyte proliferation is a typical pathological characteristic of psoriasis. Serine/threonine protein phosphatase 2A (PP2A) is one of the most important phosphatases for maintaining normal phosphorylation levels in humans. PP2Acα is the alpha subtype of the PP2A C subunit (encoded by PPP2CA), which maintains the catalytic functions of PP2A. Epidermal growth factor receptor (EGFR) is activated by phosphorylation (p-EGFR) to regulate the downstream signaling pathway to promote epidermal cell proliferation. Previous studies have found that PPP2CA induced epidermal hyperplasia, keratinization, and other pathological phenomena similar to those in mouse models of psoriasis. The present study showed that PP2Acα negatively regulated EGFR phosphorylation and epidermal cell proliferation, and EGFR inhibitors could alleviate PP2Acα by inhibiting epidermal cell proliferation. This study further examined the effect of mechanisms on epidermal cell proliferation and the downstream signaling pathway of EGFR using molecular technological methods to explore new ideas for treating psoriasis.
Collapse
Affiliation(s)
- Tao Ting
- Department of Spleen and Stomach, Jiangsu Province Hospital of Chinese Medicine
| | - Chen Yiwen
- Department of Dermatology, The Affiliated Jiangning Hospital of Nanjing Medical University District, Nanjing City, China
| | - Chen Jianquan
- Central Laboratory, The Affiliated Jiangning Hospital of Nanjing Medical University District, Nanjing City, China
| | - Lian Chao
- Central Laboratory, The Affiliated Jiangning Hospital of Nanjing Medical University District, Nanjing City, China
| | - Xu Shengjing
- Department of Dermatology, The Affiliated Jiangning Hospital of Nanjing Medical University District, Nanjing City, China
| | - Zhang Min
- Department of Dermatology, The Affiliated Jiangning Hospital of Nanjing Medical University District, Nanjing City, China
| | - Chao Fang
- Department of Dermatology, The Affiliated Jiangning Hospital of Nanjing Medical University District, Nanjing City, China.,Central Laboratory, The Affiliated Jiangning Hospital of Nanjing Medical University District, Nanjing City, China
| |
Collapse
|
2
|
New Insights into Immunological Involvement in Congenital Disorders of Glycosylation (CDG) from a People-Centric Approach. J Clin Med 2020; 9:jcm9072092. [PMID: 32635232 PMCID: PMC7408855 DOI: 10.3390/jcm9072092] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 06/27/2020] [Accepted: 06/28/2020] [Indexed: 02/08/2023] Open
Abstract
Congenital disorders of glycosylation (CDG) are rare diseases with variable phenotypes and severity. Immunological involvement remains a largely uncharted topic in CDG, mainly due to lack of robust data. To better characterize immune-related manifestations’ prevalence, relevance, and quality-of-life (QoL) impact, we developed electronic questionnaires targeting (1) CDG patients and (2) the general “healthy” population. Two-hundred and nine CDG patients/caregivers and 349 healthy participants were included in this study. PMM2-CDG was the most represented CDG (n = 122/209). About half of these participants (n = 65/122) described relevant infections with a noteworthy prevalence of those affecting the gastrointestinal tract (GI) (63.1%, n = 41/65). Infection burden and QoL impact were shown as infections correlated with more severe clinical phenotypes and with a set of relevant non-immune PMM2-CDG signs. Autoimmune diseases had only a marginal presence in PMM2-CDG (2.5%, n = 3/122), all being GI-related. Allergy prevalence was also low in PMM2-CDG (33%, n = 41/122) except for food allergies (26.8%, n = 11/41, of PMM2-CDG and 10.8%, n = 17/158, of controls). High vaccination compliance with greater perceived ineffectiveness (28.3%, n = 17/60) and more severe adverse reactions were described in PMM2-CDG. This people-centric approach not only confirmed literature findings, but created new insights into immunological involvement in CDG, namely by highlighting the possible link between the immune and GI systems in PMM2-CDG. Finally, our results emphasized the importance of patient/caregiver knowledge and raised several red flags about immunological management.
Collapse
|
3
|
Onoufriadis A, Simpson JK, McDonald C, Nguyen TTM, Campeau PM, Simpson MA, Martinez AE, McGrath JA. Nonsyndromic erythrodermic ichthyosis resulting from a homozygous mutation in PIGL. Clin Exp Dermatol 2019; 45:391-394. [PMID: 31535386 DOI: 10.1111/ced.14077] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/29/2019] [Indexed: 12/01/2022]
Affiliation(s)
- A Onoufriadis
- St John's Institute of Dermatology, School of Basic and Medical Biosciences, King's College London, London, UK
| | - J K Simpson
- St John's Institute of Dermatology, School of Basic and Medical Biosciences, King's College London, London, UK
| | - C McDonald
- Great Ormond Street Hospital for Children, NHS Foundation Trust, London, UK
| | - T T M Nguyen
- Centre Hospitalier Universitaire Sainte-Justine Research Center, University of Montreal, Montreal, Canada
| | - P M Campeau
- Centre Hospitalier Universitaire Sainte-Justine Research Center, University of Montreal, Montreal, Canada
| | - M A Simpson
- Department of Medical and Molecular Genetics, School of Basic and Medical Biosciences, King's College London, London, UK
| | - A E Martinez
- Great Ormond Street Hospital for Children, NHS Foundation Trust, London, UK
| | - J A McGrath
- St John's Institute of Dermatology, School of Basic and Medical Biosciences, King's College London, London, UK
| |
Collapse
|
4
|
PIGO deficiency: palmoplantar keratoderma and novel mutations. Orphanet J Rare Dis 2017; 12:101. [PMID: 28545593 PMCID: PMC5445308 DOI: 10.1186/s13023-017-0654-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Accepted: 05/15/2017] [Indexed: 01/19/2023] Open
Abstract
Background Several genetic defects have been identified in the glycosylphosphatidylinositol (GPI) anchor synthesis, including mutations in PIGO encoding phosphatidylinositol glycan anchor biosynthesis class O protein. These defects constitute a subgroup of the congenital disorders of glycosylation (CDG). Seven patients from five families have been reported carrying variants in PIGO that cause an autosomal recessive syndrome characterised by dysmorphism, psychomotor disability, epilepsy and hyperphosphatasemia. Methods Whole exome sequencing was performed in a boy with dysmorphism, psychomotor disability, epilepsy, palmoplantar keratoderma, hyperphosphatasemia and platelet dysfunction without a clinical bleeding phenotype. Results Two novel variants in PIGO were detected. The missense variant encoding p. His871Pro was inherited from the boy’s father while the frameshift variant encoding p. Arg604ProfsTer40 was maternally inherited. Conclusion A boy with two novel PIGO variants is reported. The skin phenotype and platelet dysfunction in this patient have not been described in previously reported patients with PIGO deficiency but it is of course uncertain whether these are caused by this disorder. The literature on PIGO deficiency is reviewed. Electronic supplementary material The online version of this article (doi:10.1186/s13023-017-0654-9) contains supplementary material, which is available to authorized users.
Collapse
|
5
|
Locke MEO, Milojevic M, Eitutis ST, Patel N, Wishart AE, Daley M, Hill KA. Genomic copy number variation in Mus musculus. BMC Genomics 2015; 16:497. [PMID: 26141061 PMCID: PMC4490682 DOI: 10.1186/s12864-015-1713-z] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 06/22/2015] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Copy number variation is an important dimension of genetic diversity and has implications in development and disease. As an important model organism, the mouse is a prime candidate for copy number variant (CNV) characterization, but this has yet to be completed for a large sample size. Here we report CNV analysis of publicly available, high-density microarray data files for 351 mouse tail samples, including 290 mice that had not been characterized for CNVs previously. RESULTS We found 9634 putative autosomal CNVs across the samples affecting 6.87% of the mouse reference genome. We find significant differences in the degree of CNV uniqueness (single sample occurrence) and the nature of CNV-gene overlap between wild-caught mice and classical laboratory strains. CNV-gene overlap was associated with lipid metabolism, pheromone response and olfaction compared to immunity, carbohydrate metabolism and amino-acid metabolism for wild-caught mice and classical laboratory strains, respectively. Using two subspecies of wild-caught Mus musculus, we identified putative CNVs unique to those subspecies and show this diversity is better captured by wild-derived laboratory strains than by the classical laboratory strains. A total of 9 genic copy number variable regions (CNVRs) were selected for experimental confirmation by droplet digital PCR (ddPCR). CONCLUSION The analysis we present is a comprehensive, genome-wide analysis of CNVs in Mus musculus, which increases the number of known variants in the species and will accelerate the identification of novel variants in future studies.
Collapse
Affiliation(s)
- M Elizabeth O Locke
- Department of Computer Science, The University of Western Ontario, London, ON, N6A 5B7, Canada.
| | - Maja Milojevic
- Department of Biology, The University of Western Ontario, Biological and Geological Sciences Building 1151 Richmond St. N, London, ON, N6A 5B7, Canada.
| | - Susan T Eitutis
- Department of Biology, The University of Western Ontario, Biological and Geological Sciences Building 1151 Richmond St. N, London, ON, N6A 5B7, Canada.
| | - Nisha Patel
- Department of Biology, The University of Western Ontario, Biological and Geological Sciences Building 1151 Richmond St. N, London, ON, N6A 5B7, Canada.
| | - Andrea E Wishart
- Department of Biology, The University of Western Ontario, Biological and Geological Sciences Building 1151 Richmond St. N, London, ON, N6A 5B7, Canada.
| | - Mark Daley
- Department of Computer Science, The University of Western Ontario, London, ON, N6A 5B7, Canada.
- Department of Biology, The University of Western Ontario, Biological and Geological Sciences Building 1151 Richmond St. N, London, ON, N6A 5B7, Canada.
| | - Kathleen A Hill
- Department of Computer Science, The University of Western Ontario, London, ON, N6A 5B7, Canada.
- Department of Biology, The University of Western Ontario, Biological and Geological Sciences Building 1151 Richmond St. N, London, ON, N6A 5B7, Canada.
| |
Collapse
|
6
|
Swoboda KJ, Margraf RL, Carey JC, Zhou H, Newcomb TM, Coonrod E, Durtschi J, Mallempati K, Kumanovics A, Katz BE, Voelkerding KV, Opitz JM. A novel germline PIGA mutation in Ferro-Cerebro-Cutaneous syndrome: a neurodegenerative X-linked epileptic encephalopathy with systemic iron-overload. Am J Med Genet A 2013; 164A:17-28. [PMID: 24259288 DOI: 10.1002/ajmg.a.36189] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 07/25/2013] [Indexed: 01/22/2023]
Abstract
Three related males presented with a newly recognized x-linked syndrome associated with neurodegeneration, cutaneous abnormalities, and systemic iron overload. Linkage studies demonstrated that they shared a haplotype on Xp21.3-Xp22.2 and exome sequencing was used to identify candidate variants. Of the segregating variants, only a PIGA mutation segregated with disease in the family. The c.328_330delCCT PIGA variant predicts, p.Leu110del (or c.1030_1032delCTT, p.Leu344del depending on the reference sequence). The unaffected great-grandfather shared his X allele with the proband but he did not have the PIGA mutation, indicating that the mutation arose de novo in his daughter. A single family with a germline PIGA mutation has been reported; affected males had a phenotype characterized by multiple congenital anomalies and severe neurologic impairment resulting in infantile lethality. In contrast, affected boys in the family described here were born without anomalies and were neurologically normal prior to onset of seizures after 6 months of age, with two surviving to the second decade. PIGA encodes an enzyme in the GPI anchor biosynthesis pathway. An affected individual in the family studied here was deficient in GPI anchor proteins on granulocytes but not erythrocytes. In conclusion, the PIGA mutation in this family likely causes a reduction in GPI anchor protein cell surface expression in various cell types, resulting in the observed pleiotropic phenotype involving central nervous system, skin, and iron metabolism.
Collapse
Affiliation(s)
- Kathryn J Swoboda
- Pediatric Motor Disorders Research Program, Department of Neurology, University of Utah School of Medicine, Salt Lake City, Utah
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Ting SB, Caddy J, Wilanowski T, Auden A, Cunningham JM, Elias PM, Holleran WM, Jane SM. The epidermis of grhl3-null mice displays altered lipid processing and cellular hyperproliferation. Organogenesis 2012; 2:33-5. [PMID: 19521564 DOI: 10.4161/org.2.2.2167] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2005] [Accepted: 09/12/2005] [Indexed: 11/19/2022] Open
Abstract
The presence of an impermeable surface barrier is an essential homeostatic mechanism in almost all living organisms. We have recently described a novel gene that is critical for the developmental instruction and repair of the integument in mammals. This gene, Grainy head-like 3 (Grhl3) is a member of a large family of transcription factors that are homologs of the Drosophila developmental gene grainy head (grh). Mice lacking Grhl3 fail to form an adequate skin barrier, and die at birth due to dehydration. These animals are also unable to repair the epidermis, exhibiting failed wound healing in both fetal and adult stages of development. These defects are due, in part, to diminished expression of a Grhl3 target gene, Transglutaminase 1 (TGase 1), which encodes a key enzyme involved in cross-linking of epidermal structural proteins and lipids into the cornified envelope (CE). Remarkably, the Drosophila grh gene plays an analogous role, regulating enzymes involved in the generation of quinones, which are essential for cross-linking structural components of the fly epidermis. In an extension of our initial analyses, we focus this report on additional defects observed in the Grhl3-null epidermis, namely defective extra-cellular lipid processing, altered lamellar lipid architecture and cellular hyperproliferation. These abnormalities suggest that Grhl3 plays diverse mechanistic roles in maintaining homeostasis in the skin.
Collapse
Affiliation(s)
- Stephen B Ting
- Rotary Bone Marrow Research Laboratories; Parkville, Victoria Australia
| | | | | | | | | | | | | | | |
Collapse
|
8
|
Ng B, Hackmann K, Jones M, Eroshkin A, He P, Wiliams R, Bhide S, Cantagrel V, Gleeson J, Paller A, Schnur R, Tinschert S, Zunich J, Hegde M, Freeze H. Mutations in the glycosylphosphatidylinositol gene PIGL cause CHIME syndrome. Am J Hum Genet 2012; 90:685-8. [PMID: 22444671 PMCID: PMC3322218 DOI: 10.1016/j.ajhg.2012.02.010] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Revised: 01/30/2012] [Accepted: 02/09/2012] [Indexed: 10/28/2022] Open
Abstract
CHIME syndrome is characterized by colobomas, heart defects, ichthyosiform dermatosis, mental retardation (intellectual disability), and ear anomalies, including conductive hearing loss. Whole-exome sequencing on five previously reported cases identified PIGL, the de-N-acetylase required for glycosylphosphatidylinositol (GPI) anchor formation, as a strong candidate. Furthermore, cell lines derived from these cases had significantly reduced levels of the two GPI anchor markers, CD59 and a GPI-binding toxin, aerolysin (FLAER), confirming the pathogenicity of the mutations.
Collapse
Affiliation(s)
- Bobby G. Ng
- Genetic Disease Program, Sanford Children's Health Research Center, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA
| | - Karl Hackmann
- Institut fuer Klinische Genetik, Medizinische Fakultaet Carl Gustav Carus, Technische Universitaet Dresden, 01307 Dresden, Germany
| | - Melanie A. Jones
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Alexey M. Eroshkin
- Genetic Disease Program, Sanford Children's Health Research Center, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA
| | - Ping He
- Genetic Disease Program, Sanford Children's Health Research Center, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA
| | - Roy Wiliams
- Genetic Disease Program, Sanford Children's Health Research Center, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA
| | - Shruti Bhide
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Vincent Cantagrel
- Neurogenetics Laboratory, Institute for Genomic Medicine, Howard Hughes Medical Institute, Department of Neurosciences and Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA
| | - Joseph G. Gleeson
- Neurogenetics Laboratory, Institute for Genomic Medicine, Howard Hughes Medical Institute, Department of Neurosciences and Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA
| | - Amy S. Paller
- Department of Dermatology, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Rhonda E. Schnur
- Division of Genetics, Department of Pediatrics, Cooper Medical School of Rowan University, Camden, NJ 08103, USA
| | - Sigrid Tinschert
- Institut fuer Klinische Genetik, Medizinische Fakultaet Carl Gustav Carus, Technische Universitaet Dresden, 01307 Dresden, Germany
| | - Janice Zunich
- Genetics Center, Indiana University School of Medicine–Northwest, Gary, IN 46408, USA
| | - Madhuri R. Hegde
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Hudson H. Freeze
- Genetic Disease Program, Sanford Children's Health Research Center, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA
| |
Collapse
|
9
|
Ahrens MJ, Li Y, Jiang H, Dudley AT. Convergent extension movements in growth plate chondrocytes require gpi-anchored cell surface proteins. Development 2009; 136:3463-74. [PMID: 19762422 DOI: 10.1242/dev.040592] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Proteins that are localized to the cell surface via glycosylphosphatidylinositol (gpi) anchors have been proposed to regulate cell signaling and cell adhesion events involved in tissue patterning. Conditional deletion of Piga, which encodes the catalytic subunit of an essential enzyme in the gpi-biosynthetic pathway, in the lateral plate mesoderm results in normally patterned limbs that display chondrodysplasia. Analysis of mutant and mosaic Piga cartilage revealed two independent cell autonomous defects. First, loss of Piga function interferes with signal reception by chondrocytes as evidenced by delayed maturation. Second, the proliferative chondrocytes, although present, fail to flatten and arrange into columns. We present evidence that the abnormal organization of mutant proliferative chondrocytes results from errors in cell intercalation. Collectively, our data suggest that the distinct morphological features of the proliferative chondrocytes result from a convergent extension-like process that is regulated independently of chondrocyte maturation.
Collapse
Affiliation(s)
- Molly J Ahrens
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, IL 60208, USA
| | | | | | | |
Collapse
|
10
|
Leyvraz C, Charles RP, Rubera I, Guitard M, Rotman S, Breiden B, Sandhoff K, Hummler E. The epidermal barrier function is dependent on the serine protease CAP1/Prss8. ACTA ACUST UNITED AC 2005; 170:487-96. [PMID: 16061697 PMCID: PMC2171460 DOI: 10.1083/jcb.200501038] [Citation(s) in RCA: 215] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Serine proteases are proteolytic enzymes that are involved in the regulation of various physiological processes. We generated mice lacking the membrane-anchored channel-activating serine protease (CAP) 1 (also termed protease serine S1 family member 8 [Prss8] and prostasin) in skin, and these mice died within 60 h after birth. They presented a lower body weight and exhibited severe malformation of the stratum corneum (SC). This aberrant skin development was accompanied by an impaired skin barrier function, as evidenced by dehydration and skin permeability assay and transepidermal water loss measurements leading to rapid, fatal dehydration. Analysis of differentiation markers revealed no major alterations in CAP1/Prss8-deficient skin even though the epidermal deficiency of CAP1/Prss8 expression disturbs SC lipid composition, corneocyte morphogenesis, and the processing of profilaggrin. The examination of tight junction proteins revealed an absence of occludin, which did not prevent the diffusion of subcutaneously injected tracer (∼600 D) toward the skin surface. This study shows that CAP1/Prss8 expression in the epidermis is crucial for the epidermal permeability barrier and is, thereby, indispensable for postnatal survival.
Collapse
Affiliation(s)
- Céline Leyvraz
- Département de Pharmacologie et de Toxicologie, Université de Lausanne, CH-1005 Lausanne, Switzerland
| | | | | | | | | | | | | | | |
Collapse
|
11
|
Hewett DR, Simons AL, Mangan NE, Jolin HE, Green SM, Fallon PG, McKenzie ANJ. Lethal, neonatal ichthyosis with increased proteolytic processing of filaggrin in a mouse model of Netherton syndrome. Hum Mol Genet 2004; 14:335-46. [PMID: 15590704 DOI: 10.1093/hmg/ddi030] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Netherton syndrome is an autosomal recessive multisystemic disorder characterized by congenital ichthyosiform erythroderma, hair shaft defects and atopy, caused by mutations within the human SPINK5 gene. To investigate the development of this disease, we have cloned mouse spink5 and created mice with a mutated premature stop codon at amino acid R820X, to produce an allele that closely mimics a point mutation (E827X) in human SPINK5. Newborn spink5(R820X/R820X) mice develop a lethal, severe ichthyosis with a loss of skin barrier function and dehydration, resulting in death within a few hours of birth, similar to that observed in patients with severe Netherton syndrome. Epidermal barrier function is compromised because of the stratum corneum becoming spontaneously detached in the newborn mice, and this is probably compounded by the reduced mechanical strength detected in the cornified envelopes. Biochemical analysis of skin from newborn wild-type and spink5(R820X/R820X) mice revealed a substantial increase in the proteolytic processing of profilaggrin into its constituent filaggrin monomers. Filaggrin functions to organize keratin filaments into highly ordered macrofibrils that crisscross the cornified cells of the stratum corneum imparting structural integrity, and defects in filaggrin processing occur in a number of forms of congenital ichthyosis. These data suggest that in the absence of the serine protease inhibitor spink5, there is an abnormal increase in the processing of profilaggrin, resulting in an overabundance of filaggrin monomers, and that this may play a direct role in the observed deficit in the adhesion of the stratum corneum and the severely compromised epidermal barrier function.
Collapse
|