Simona Coppola1, Antonella Insalaco2, Erika Zara3, Martina Di Rocco4, Denise Pires Marafon2, Francesca Spadaro5, Luca Pannone6, Luciapia Farina2, Luca Pasquini5, Simone Martinelli7, Fabrizio De Benedetti8, Marco Tartaglia9. 1. National Centre Rare Diseases, Istituto Superiore di Sanità, Rome, Italy. 2. Division of Rheumatology, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy. 3. Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy; Department of Biology and Biotechnology "Charles Darwin," "Sapienza" University of Rome, Rome, Italy. 4. Department of Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy; Department of Human Neuroscience, "Sapienza" University of Rome, Rome, Italy. 5. Core Facilities, Istituto Superiore di Sanità, Rome, Italy. 6. Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy. 7. Department of Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy. 8. Division of Rheumatology, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy. Electronic address: fabrizio.debenedetti@opbg.net. 9. Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy. Electronic address: marco.tartaglia@opbg.net.
Abstract
BACKGROUND: Pathogenic missense variants in cell division control protein 42 (CDC42) differentially affect protein function, causing a clinically wide phenotypic spectrum variably affecting neurodevelopment, hematopoiesis, and immune response. More recently, 3 variants at the C-terminus of CDC42 were proposed to similarly impact protein function and cause a novel autoinflammatory disorder. OBJECTIVES: We sought to clinically and functionally classify these variants to improve patient management. METHODS: Comparative analysis of the available clinical data and medical history of patients was performed. In vitro and in vivo studies were carried out to functionally characterize individual variants. RESULTS: Differently from what had previously been observed for the p.R186C change causing neonatal-onset cytopenia, autoinflammation, and recurrent hemophagocytic lymphohistiocytosis, p.C188Y and p.∗192Cext∗24 promoted accelerated protein degradation. Unprenylated CDC42C188Y did not behave as a membrane-bound protein, whereas the residual CDC42∗192Cext∗24 mutant replicated the CDC42R186C behavior, being targeted to the Golgi apparatus in a palmitoylation-dependent manner. Assessment of in vitro polarized migration and development in Caenorhabditis elegans documented a loss-of-function behavior of the p.C188Y and p.∗192Cext∗24 variants. Consistently, the 3 pathogenic variants were associated with different clinical presentations, with dysmorphisms, severity, and age of onset of cytopenia and extent of autoinflammation representing major differences. CONCLUSIONS: Pathogenic variants at the CDC42 C-terminus differently impact protein stability, localization, and function, and cause different diseases, with p.R186C specifically associated with neonatal-onset pancytopenia and severe autoinflammation/hemophagocytic lymphohistiocytosis requiring emapalumab and bone marrow transplantation, and p.C188Y and p.∗192Cext∗24 causing anakinra-sensitive autoinflammation.
BACKGROUND: Pathogenic missense variants in cell division control protein 42 (CDC42) differentially affect protein function, causing a clinically wide phenotypic spectrum variably affecting neurodevelopment, hematopoiesis, and immune response. More recently, 3 variants at the C-terminus of CDC42 were proposed to similarly impact protein function and cause a novel autoinflammatory disorder. OBJECTIVES: We sought to clinically and functionally classify these variants to improve patient management. METHODS: Comparative analysis of the available clinical data and medical history of patients was performed. In vitro and in vivo studies were carried out to functionally characterize individual variants. RESULTS: Differently from what had previously been observed for the p.R186C change causing neonatal-onset cytopenia, autoinflammation, and recurrent hemophagocytic lymphohistiocytosis, p.C188Y and p.∗192Cext∗24 promoted accelerated protein degradation. Unprenylated CDC42C188Y did not behave as a membrane-bound protein, whereas the residual CDC42∗192Cext∗24 mutant replicated the CDC42R186C behavior, being targeted to the Golgi apparatus in a palmitoylation-dependent manner. Assessment of in vitro polarized migration and development in Caenorhabditis elegans documented a loss-of-function behavior of the p.C188Y and p.∗192Cext∗24 variants. Consistently, the 3 pathogenic variants were associated with different clinical presentations, with dysmorphisms, severity, and age of onset of cytopenia and extent of autoinflammation representing major differences. CONCLUSIONS: Pathogenic variants at the CDC42 C-terminus differently impact protein stability, localization, and function, and cause different diseases, with p.R186C specifically associated with neonatal-onset pancytopenia and severe autoinflammation/hemophagocytic lymphohistiocytosis requiring emapalumab and bone marrow transplantation, and p.C188Y and p.∗192Cext∗24 causing anakinra-sensitive autoinflammation.