title: A synonymous mutation in SPINK5 exon 11 causes Netherton syndrome by altering exonic splicing regulatory elements.
abstract: Netherton syndrome (NS) is a rare, life-threatening ichthyosiform syndrome caused by recessive loss-of-function mutations in SPINK5 gene encoding lymphoepithelial Kazal-type-related inhibitor (LEKTI), a serine protease inhibitor expressed in the most differentiated epidermal layers and crucial for skin barrier function. We report the functional characterization of a previously unrecognized synonymous variant, c.891C>T (p.Cys297Cys), identified in the SPINK5 exon 11 of an NS patient. We demonstrated that the c.891C>T mutation is associated with abnormal pre-mRNA splicing and residual LEKTI expression in the patient's keratinocytes. Subsequent minigene splicing assays and in silico predictions confirmed the direct role of the synonymous mutation in inhibiting exon 11 inclusion by a mechanism that involves the activity of exonic regulatory sequences, namely splicing enhancer and silencer. However, this deleterious effect was not complete and a residual amount of normal mRNA and LEKTI protein could be detected, correlating with the relatively mild patient's phenotype. Our study represents the first identification of a disease-causing SPINK5 mutation that alters splicing without affecting canonical splice sites.
authors.affiliation: Dermatology Unit, Ospedale Pediatrico Bambino Gesù-IRCCS, Rome, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Fortugno
authors.forename: Fabiana
authors.initials: F
authors.lastname: Grosso
authors.forename: Giovanna
authors.initials: G
authors.lastname: Zambruno
authors.forename: Serena
authors.initials: S
authors.lastname: Pastore
authors.forename: Flavio
authors.initials: F
authors.lastname: Faletra
authors.forename: Daniele
authors.initials: D
authors.lastname: Castiglia
mesh_terms: D002478:Cells, Cultured; D002675:Child, Preschool; D019295:Computational Biology / Q000379:methods; D004742:Enhancer Elements, Genetic / Q000235:genetics; D005091:Exons / Q000235:genetics*; D005260:Female; D005838:Genotype; D006801:Humans; D015603:Keratinocytes; D009154:Mutation; D056770:Netherton Syndrome / Q000235:genetics*; D010641:Phenotype; D053491:Proteinase Inhibitory Proteins, Secretory / Q000235:genetics*; D012326:RNA Splicing / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000074163:Serine Peptidase Inhibitor Kazal-Type 5; D037941:Silencer Elements, Transcriptional / Q000235:genetics
chemical_list: D053491:Proteinase Inhibitory Proteins, Secretory; C120650:SPINK5 protein, human; D000074163:Serine Peptidase Inhibitor Kazal-Type 5