title: Loss-of-Function Mutations in SERPINB8 Linked to Exfoliative Ichthyosis with Impaired Mechanical Stability of Intercellular Adhesions.
abstract: SERPINS comprise a large and functionally diverse family of serine protease inhibitors. Here, we report three unrelated families with loss-of-function mutations in SERPINB8 in association with an autosomal-recessive form of exfoliative ichthyosis. Whole-exome sequencing of affected individuals from a consanguineous Tunisian family and a large Israeli family revealed a homozygous frameshift mutation, c.947delA (p.Lys316Serfs(∗)90), and a nonsense mutation, c.850C>T (p.Arg284(∗)), respectively. These two mutations are located in the last exon of SERPINB8 and, hence, would not be expected to lead to nonsense-mediated decay of the mRNA; nonetheless, both mutations are predicted to lead to loss of the reactive site loop of SERPINB8, which is crucial for forming the SERPINB8-protease complex. Using Sanger sequencing, a homozygous missense mutation, c.2T>C (p.Met1?), predicted to result in an N-terminal truncated protein, was identified in an additional family from UAE. Histological analysis of a skin biopsy from an individual homozygous for the variant p.Arg284(∗) showed disadhesion of keratinocytes in the lower epidermal layers plus decreased SERPINB8 levels compared to control. In vitro studies utilizing siRNA-mediated knockdown of SERPINB8 in keratinocytes demonstrated that in the absence of the protein, there is a cell-cell adhesion defect, particularly when cells are subjected to mechanical stress. In addition, immunoblotting and immunostaining revealed an upregulation of desmosomal proteins. In conclusion, we report mutations in SERPINB8 that are associated with exfoliative ichthyosis and provide evidence that SERPINB8 contributes to the mechanical stability of intercellular adhesions in the epidermis.
authors.affiliation: Centre for Cell Biology and Cutaneous Research, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London E1 2AT, UK.
authors.forename: Manuela
authors.initials: M
authors.lastname: Pigors
authors.affiliation: Department of Dermatology, Tel Aviv Sourasky Medical Center, 64239 Tel Aviv, Israel.
authors.forename: Ofer
authors.initials: O
authors.lastname: Sarig
authors.affiliation: Institute of Human Genetics, University Medical Center Freiburg, 79106 Freiburg, Germany.
authors.forename: Lisa
authors.initials: L
authors.lastname: Heinz
authors.affiliation: University College London Genetics Institute, London WC1E 6BT, UK.
authors.forename: Vincent
authors.initials: V
authors.lastname: Plagnol
authors.affiliation: Institute of Human Genetics, University Medical Center Freiburg, 79106 Freiburg, Germany.
authors.forename: Judith
authors.initials: J
authors.lastname: Fischer
authors.affiliation: Department of Dermatology, Tel Aviv Sourasky Medical Center, 64239 Tel Aviv, Israel.
authors.forename: Janan
authors.initials: J
authors.lastname: Mohamad
authors.affiliation: Department of Dermatology, Tel Aviv Sourasky Medical Center, 64239 Tel Aviv, Israel.
authors.forename: Natalia
authors.initials: N
authors.lastname: Malchin
authors.affiliation: Centre for Cell Biology and Cutaneous Research, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London E1 2AT, UK.
authors.forename: Shefali
authors.initials: S
authors.lastname: Rajpopat
authors.affiliation: Department of Dermatology, Charles Nicolle Hospital, 1006 Tunis, Tunisia.
authors.forename: Monia
authors.initials: M
authors.lastname: Kharfi
authors.affiliation: Consultant Dermatologist (retired), British Ministry of Defence, London SW1A 2HB, UK.
authors.forename: Giles G
authors.initials: GG
authors.lastname: Lestringant
authors.affiliation: Department of Dermatology, Tel Aviv Sourasky Medical Center, 64239 Tel Aviv, Israel.
authors.forename: Eli
authors.initials: E
authors.lastname: Sprecher
authors.affiliation: Centre for Cell Biology and Cutaneous Research, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London E1 2AT, UK. Electronic address: d.p.kelsell@qmul.ac.uk.
authors.forename: David P
authors.initials: DP
authors.lastname: Kelsell
authors.affiliation: Centre for Cell Biology and Cutaneous Research, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London E1 2AT, UK. Electronic address: d.blaydon@qmul.ac.uk.
authors.forename: Diana C
authors.initials: DC
authors.lastname: Blaydon
mesh_terms: D002448:Cell Adhesion / Q000235:genetics*; D018389:Codon, Nonsense / Q000235:genetics; D003241:Consanguinity; D005091:Exons / Q000235:genetics; D005260:Female; D016368:Frameshift Mutation / Q000235:genetics; D005808:Genes, Recessive / Q000235:genetics; D006720:Homozygote; D006801:Humans; D007057:Ichthyosis / Q000235:genetics*; D007223:Infant; D015603:Keratinocytes / Q000378:metabolism; D008297:Male; D009154:Mutation / Q000235:genetics*; D020125:Mutation, Missense / Q000235:genetics; D010375:Pedigree; D015843:Serpins / Q000235:genetics*; D014421:Turkey
chemical_list: D018389:Codon, Nonsense; C108403:SERPINB8 protein, human; D015843:Serpins