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Functional and Mechanistic Insights into the Pathogenesis of P63-Associated Disorders

2018; Elsevier BV; Volume: 19; Issue: 2 Linguagem: Inglês

10.1016/j.jisp.2018.10.004

1529-1774

Maria Rosaria Mollo, Luisa Cirillo, Claudia Russo, Dario Antonini, Caterina Missero,

Virus-based gene therapy research

The p53 family member p63 is a master regulator of gene expression in stratified epithelia, such as the epidermis. One of the main functions of p63 is to sustain mechanical resistance, positively regulating several epidermal genes involved in cell–matrix adhesion and cell–cell adhesion (Ferone et al., 2015Ferone G. Mollo M.R. Missero C. Epidermal cell junctions and their regulation by p63 in health and disease.Cell Tissue Res. 2015; 360: 513-528Google Scholar). In mice, p63 deficiency causes perinatal lethality due to cleft palate, limb truncation, and severe defects of all stratified epithelia and their derivatives, including the epidermis (Mills et al., 1999Mills A.A. Zheng B. Wang X.J. Vogel H. Roop D.R. Bradley A. et al.p63 is a p53 homologue required for limb and epidermal morphogenesis.Nature. 1999; 398: 708-713Crossref PubMed Scopus (1701) Google Scholar, Yang et al., 1999Yang A. Schweitzer R. Sun D. Kaghad M. Walker N. Bronson R.T. et al.p63 is essential for regenerative proliferation in limb, craniofacial and epithelial development.Nature. 1999; 398: 714-718Crossref PubMed Scopus (1908) Google Scholar). Epidermal integrity is severely compromised and the disorganized epidermis appears to peel off at birth, even after cesarean section (Senoo et al., 2007Senoo M. Pinto F. Crum C.P. McKeon F. p63 Is essential for the proliferative potential of stem cells in stratified epithelia.Cell. 2007; 129: 523-536Abstract Full Text Full Text PDF PubMed Scopus (697) Google Scholar). In humans, heterozygous mutations in the p63 gene give rise to at least five rare related syndromes with overlapping features, including ectodermal dysplasia, cleft lip/palate, and limb malformations (reviewed in Rinne et al., 2007Rinne T. Brunner H.G. van Bokhoven H. p63-associated disorders.Cell Cycle. 2007; 6: 262-268Crossref PubMed Scopus (225) Google Scholar). Among the p63-related disorders, Ectrodactyly, ectodermal dysplasia, and cleft lip/palate syndrome 3 (OMIM 604292) is characterized by central reduction defect of the hands and feet associated with cleft lip and/or palate, and is often caused by mutation in the DNA binding domain that are predicted to abolish the DNA binding capacity of p63 (Celli et al., 1999Celli J. Duijf P. Hamel B.C. Bamshad M. Kramer B. Smits A.P. et al.Heterozygous germline mutations in the p53 homolog p63 are the cause of EEC syndrome.Cell. 1999; 99: 143-153Abstract Full Text Full Text PDF PubMed Scopus (574) Google Scholar). In contrast ankyloblepharon-ectodermal defects-cleft lip/palate (AEC; OMIM 106260) syndrome is characterized by the most severe skin symptoms, including congenital erythroderma, skin fragility, atrophy, palmoplantar hyperkeratosis, and extensive and long-lasting erosive lesions (Dishop et al., 2009Dishop M.K. Bree A.F. Hicks M.J. Pathologic changes of skin and hair in ankyloblepharon-ectodermal defects-cleft lip/palate (AEC) syndrome.Am J Med Genet A. 2009; 149A: 1935-1941Google Scholar, Julapalli et al., 2009Julapalli M.R. Scher R.K. Sybert V.P. Siegfried E.C. Bree A.F. et al.Dermatologic findings of ankyloblepharon-ectodermal defects-cleft lip/palate (AEC) syndrome.Am J Med Genet A. 2009; 149A: 1900-1906Crossref PubMed Scopus (38) Google Scholar, McGrath et al., 2001McGrath J.A. Duijf P.H. Doetsch V. Irvine A.D. de Waal R. Vanmolkot K.R. et al.Hay-Wells syndrome is caused by heterozygous missense mutations in the SAM domain of p63.Hum Mol Genet. 2001; 10: 221-229Crossref PubMed Scopus (310) Google Scholar). Little is known about the pathogenic mechanisms underlying AEC skin erosions, therefore, the standard care for skin erosions consists of minimizing trauma and preventing infections. To dissect the molecular basis underlying AEC syndrome, we previously generated a knock-in mouse model constitutively expressing a mutation in the leucine 514 to phenylalanine (L514F) (Ferone et al., 2012Ferone G. Thomason H.A. Antonini D. De Rosa L. Hu B. Gemei M. et al.Mutant p63 causes defective expansion of ectodermal progenitor cells and impaired FGF signalling in AEC syndrome.EMBO Mol Med. 2012; 4: 192-205Crossref PubMed Scopus (57) Google Scholar). Leucine 514 is a highly conserved amino acid that is found mutated in phenylalanine, valine, or serine in AEC patients, and is located in the sterile alpha motif of the carboxyl terminal domain of the p63 alpha isoform (McGrath et al., 2001McGrath J.A. Duijf P.H. Doetsch V. Irvine A.D. de Waal R. Vanmolkot K.R. et al.Hay-Wells syndrome is caused by heterozygous missense mutations in the SAM domain of p63.Hum Mol Genet. 2001; 10: 221-229Crossref PubMed Scopus (310) Google Scholar, Payne et al., 2005Payne A.S. Yan A.C. Ilyas E. Li W. Seykora J.T. Young T.L. et al.Two novel TP63 mutations associated with the ankyloblepharon, ectodermal defects, and cleft lip and palate syndrome: a skin fragility phenotype.Arch Dermatol. 2005; 141: 1567-1573Crossref PubMed Scopus (33) Google Scholar). The AEC mouse model presents fully penetrant cleft palate, skin atrophy, hair and tooth defects, and no ectrodactyly, closely resembling the human disorder. Skin atrophy and delayed wound healing is associated with a reduced number of epidermal stem cells caused by compromised fibroblast growth factor receptor signaling and downregulation of expression of Fgfr2 and Fgfr3, p63 target genes. Accordingly, a defective stem cell compartment is observed in human skin affected by AEC syndrome (Ferone et al., 2012Ferone G. Thomason H.A. Antonini D. De Rosa L. Hu B. Gemei M. et al.Mutant p63 causes defective expansion of ectodermal progenitor cells and impaired FGF signalling in AEC syndrome.EMBO Mol Med. 2012; 4: 192-205Crossref PubMed Scopus (57) Google Scholar). In addition, characterization of the constitutive mouse model for AEC syndrome revealed that desmosomes, essential cell junctions required for mechanical resistance in the epidermis, are weakened in AEC syndrome due to reduced gene expression of at least three p63 direct target genes, Dsc3, Dsg1, and Dsp (Ferone et al., 2013Ferone G. Mollo M.R. Thomason H.A. Antonini D. Zhou H. Ambrosio R. et al.p63 control of desmosome gene expression and adhesion is compromised in AEC syndrome.Hum Mol Genet. 2013; 22: 531-543Crossref PubMed Scopus (56) Google Scholar), suggesting that reduced mechanical resistance could be due at least in part to reduced cell adhesion. Epidermal defects occurring after birth could not be evaluated in the AEC constitutive mouse model due to neonatal lethality caused by fully penetrant cleft palate. To further study the molecular defects underlying skin erosions typically observed in AEC syndrome, we generated and characterized a novel conditional mouse model in which mutant p63 L514F is expressed in skin starting from late development, therefore bypassing cleft palate. Consistent with the human phenotype, AEC mice develop skin erosions, crusting,and scaling associated with reduced mechanical strength, acantholysis, and cytolysis of the basal layer. Skin erosions induce a local and systemic inflammatory response dependent on Tslp, an IL-7–like cytokine that is produced by keratinocytes and released in response to epidermal barrier failure (Briot et al., 2009Briot A. Deraison C. Lacroix M. Bonnert C. Robin A. Besson C. et al.Kallikrein 5 induces atopic dermatitis-like lesions through PAR2-mediated thymic stromal lymphopoietin expression in Netherton syndrome.J Exp Med. 2009; 206: 1135-1147Crossref PubMed Scopus (395) Google Scholar, Demehri et al., 2008Demehri S. Liu Z. Lee J. Lin M.H. Crosby S.D. Roberts C.J. et al.Notch-deficient skin induces a lethal systemic B-lymphoproliferative disorder by secreting TSLP, a sentinel for epidermal integrity.PLoS Biol. 2008; 6: e123Crossref PubMed Scopus (152) Google Scholar, Soumelis et al., 2002Soumelis V. Reche P.A. Kanzler H. Yuan W. Edward G. Homey B. et al.Human epithelial cells trigger dendritic cell mediated allergic inflammation by producing TSLP.Nat Immunol. 2002; 3: 673-680Crossref PubMed Scopus (343) Google Scholar). In human and mouse skin, Tslp is highly expressed in acute and chronic lesions associated with barrier dysfunction associated with atopic dermatitis (Li et al., 2009Li M. Hener P. Zhang Z. Ganti K.P. Metzger D. Chambon P. Induction of thymic stromal lymphopoietin expression in keratinocytes is necessary for generating an atopic dermatitis upon application of the active vitamin D3 analogue MC903 on mouse skin.J Invest Dermatol. 2009; 129: 498-502Abstract Full Text Full Text PDF PubMed Scopus (100) Google Scholar, Soumelis et al., 2002Soumelis V. Reche P.A. Kanzler H. Yuan W. Edward G. Homey B. et al.Human epithelial cells trigger dendritic cell mediated allergic inflammation by producing TSLP.Nat Immunol. 2002; 3: 673-680Crossref PubMed Scopus (343) Google Scholar, Ziegler and Artis, 2010Ziegler S.F. Artis D. Sensing the outside world: TSLP regulates barrier immunity.Nat Immunol. 2010; 11: 289-293Crossref PubMed Scopus (442) Google Scholar) and to Netherton syndrome, caused by the dysregulation of epidermal proteases (Briot et al., 2010Briot A. Lacroix M. Robin A. Steinhoff M. Deraison C. Hovnanian A. Par2 inactivation inhibits early production of TSLP, but not cutaneous inflammation, in Netherton syndrome adult mouse model.J Invest Dermatol. 2010; 130: 2736-2742Abstract Full Text Full Text PDF PubMed Scopus (89) Google Scholar) (Figure 1). Tslp has wide-ranging effects on several cell lineages, including many immune cells, and is known to drive Th2-mediated inflammation. In addition, elevated systemic Tslp leads to aberrant B-cell development, with an influx of immature B cells into the periphery (Astrakhan et al., 2007Astrakhan A. Omori M. Nguyen T. Becker-Herman S. Iseki M. Aye T. et al.Local increase in thymic stromal lymphopoietin induces systemic alterations in B cell development.Nat Immunol. 2007; 8: 522-531Crossref PubMed Scopus (77) Google Scholar, Demehri et al., 2008Demehri S. Liu Z. Lee J. Lin M.H. Crosby S.D. Roberts C.J. et al.Notch-deficient skin induces a lethal systemic B-lymphoproliferative disorder by secreting TSLP, a sentinel for epidermal integrity.PLoS Biol. 2008; 6: e123Crossref PubMed Scopus (152) Google Scholar, Dumortier et al., 2010Dumortier A. Durham A.D. Di Piazza M. Vauclair S. Koch U. Ferrand G. et al.Atopic dermatitis-like disease and associated lethal myeloproliferative disorder arise from loss of Notch signaling in the murine skin.PLoS One. 2010; 5: e9258Crossref PubMed Scopus (139) Google Scholar). In AEC mice, we find that epidermal-derived Tslp circulates into the blood, causing expansion of pre-B cells in the bone marrow and spleen, giving rise to an autoimmune B-cell proliferative disorder. Interestingly, genetic ablation of Tslp in the epidermis of AEC mice has no effect on early skin lesions, but significantly reduces skin and systemic inflammation, rescuing B-cell differentiation, and reducing mortality. We conclude that p63 gene mutations in AEC syndrome affect expression of specific target genes, including those encoding for epidermal proteins involved in cell adhesion and in mechanical resilience, causing extensive skin erosions. As a consequence of these lesions, epidermal cells produce inflammatory cytokines, leading to local and systemic inflammation. Because we found that extended skin erosions in AEC patients can also be associated with TSLP, measuring its serum levels in severely affected patients may help to design strategy to ameliorate their health conditions and to prevent a secondary autoimmune disease. The authors state no conflict of interest. This work was supported by the Telethon grant GGP09230 and GGP16235 (to CM), the ERA-Net Research Program on Rare Diseases (ERARE-2) Skin-Dev (to CM). Publication of this supplement is supported by the Chinese Medical Association and Hampton Sevson Ltd.