Dissection of the molecular effects of Citron Kinase deletion: insights from neuro-developmental and neuro-oncology models

Research on genetic and non-genetic disorders of the brain has revealed the enormous complexity of the mammalian central nervous system (CNS) and how the CNS optimal functioning requires a delicate balance and interplay of its cell types and molecular signaling pathways. Neuro-developmental disorders and brain tumors differently impact the CNS functioning but are however tightly linked, as disruptions of developmental signaling pathways have been implicated in tumor initiation and progression. Additionally, genetic deregulation of certain proteins or uncontrolled timing of gene expression can result in neurodevelopmental disorders and/or cancer and exploring these shared pathways could open the way for developing innovative therapies for brain tumor treatment. In this context, we focused our study on the multifaceted role of Citron Kinase (CIT-K), leading cause of MCPH17, a genetic form of primary microcephaly. We developed new mouse model and human forebrain organoids, to underscore the species-specific differences and molecular consequences of CIT-K mutations and provide crucial insights into human microcephaly. We found that during neurodevelopment, loss of CIT-K alters the organoid cytoarchitectural complexity, disrupts the polarity of neural progenitor cells (NPCs) cytokinesis, and leads to apoptosis and DNA damage accumulation. The latter occurs because loss of CIT-K compromises the correct functioning of the homologous recombination pathway, important to repair DNA double strand break lesions. We found that these alterations can be reverted by acting on microtubule dynamics and HDAC6, offering potential therapeutic interventions for this disorder. Also, we investigated the consequences of targeting CIT-K for Medulloblastoma (MB), the most prevalent malignant brain tumor in children, as MB cancer cells share many molecular features with NPCs. We previously proposed CIT-K as a target for MB treatment as its loss reduces the expansion of MB, both in vitro and in vivo, leading to cytokinesis failure, apoptosis, and DNA damage. We thus explored the therapeutic potential of CIT-K by characterizing the effects of Lestaurtinib, a polypharmacological inhibitor previously tested in clinical trials for other tumor types. We found that 7 this molecule can phenocopy the effects of CIT-K loss, thus highlighting it as a good candidate for drug repositioning in MB. Collectively, these findings contribute to a comprehensive understanding of CIT-K diverse roles in both neurodevelopment and neuro-oncology by unraveling its intricate molecular mechanisms and highlight the potential therapeutic strategies for these disorders in the complex landscape of brain biology.