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Refining the mutational spectrum and gene–phenotype correlates in pontocerebellar hypoplasia: results of a multicentric study

2021; BMJ; Volume: 59; Issue: 4 Linguagem: Inglês

10.1136/jmedgenet-2020-107497

1468-6244

Sara Nuovo, Alessia Micalizzi, Romina Romaniello, Filippo Arrigoni, Monia Ginevrino, Antonella Casella, Valentina Serpieri, Stefano D’Arrigo, Marilena Briguglio, Grazia Salerno, Sara Rossato, Stefano Sartori, Vincenzo Leuzzi, Roberta Battini, Bruria Ben‐Zeev, Claudio Graziano, Marisol Mirabelli Badenier, V. Branković, Nardo Nardocci, Ronen Spiegel, Danijela Petković Ramadža, Giovanni Vento, Itxaso Martí, Alessandro Simonati, Savina Dipresa, Elena Freri, Tommaso Mazza, Maria Teresa Bassi, Luca Bosco, Lorena Travaglini, Ginevra Zanni, Enrico Bertini, Nicola Vanacore, Renato Borgatti, Enza Maria Valente,

Cancer-related molecular mechanisms research

Background Pontocerebellar hypoplasias (PCH) comprise a group of genetically heterogeneous disorders characterised by concurrent hypoplasia of the pons and the cerebellum and variable clinical and imaging features. The current classification includes 13 subtypes, with ~20 known causative genes. Attempts have been made to delineate the phenotypic spectrum associated to specific PCH genes, yet clinical and neuroradiological features are not consistent across studies, making it difficult to define gene-specific outcomes. Methods We performed deep clinical and imaging phenotyping in 56 probands with a neuroradiological diagnosis of PCH, who underwent NGS-based panel sequencing of PCH genes and MLPA for CASK rearrangements. Next, we conducted a phenotype-based unsupervised hierarchical cluster analysis to investigate associations between genes and specific phenotypic clusters. Results A genetic diagnosis was obtained in 43 probands (77%). The most common causative gene was CASK , which accounted for nearly half cases (45%) and was mutated in females and occasionally in males. The European founder mutation p.Ala307Ser in TSEN54 and pathogenic variants in EXOSC3 accounted for 18% and 9% of cases, respectively. VLDLR , TOE1 and RARS2 were mutated in single patients. We were able to confirm only few previously reported associations, including jitteriness and clonus with TSEN54 and lower motor neuron signs with EXOSC3 . When considering multiple features simultaneously, a clear association with a phenotypic cluster only emerged for EXOSC3 . Conclusion CASK represents the major PCH causative gene in Italy. Phenotypic variability associated with the most common genetic causes of PCH is wider than previously thought, with marked overlap between CASK and TSEN54 -associated disorders.