CERAMIDE SYNTHASE 6 REGULATES CELLULAR FUNCTIONS DURING NEOCORTEX DEVELOPMENT AND IS ASSOCIATED WITH CORTICAL DEVELOPMENT DISORDERS

Cerebral cortical malformations, such as heterotopias, are associated with epilepsy, developmental delay and intellectual disability. Heterotopias are neuron clusters found in abnormal localisations, e.g., in the subcortical white matter. Rare de novo mutations in the Ceramide Synthase 6 (CERS6) gene were found in patients with heterotopia, drug-resistant epilepsy and/or intellectual disability. CERS6 is involved in de novo ceramide production at the endoplasmic reticulum, although its role during neurodevelopment is unknown. Ceramides are building blocks of more complex sphingolipids, e.g., sphingomyelin and glycosphingolipids, including gangliosides. Sphingolipids are major components of cell membranes and are essential for structural maintenance and organelle homeostasis. They also act as metabolic fuel, second messengers and membrane platforms for protein anchoring. Using mouse and human in vitro neocortex development models, we study the roles of CerS6/CERS6 and ceramides in health and disease. Mouse development is studied using in utero electroporation to knockdown or overexpress CerS6, including patient variants. Preliminary results show defects in progenitor cells and neuron distribution, as well as a disrupted ventricular surface when CerS6 is downregulated. When CERS6 is overexpressed, an increase in the number of progenitors and their ability to proliferate is observed, with patient mutations having variable effects. Using these acute manipulations, gene dosage effects are observed. Human development can be recapitulated in vitro using human induced pluripotent stem cells (patient-derived and gene-edited) to generate, e.g. dorsal forebrain organoids. We will be assessing progenitors and neurons in generated mutant cultures. It is crucial to further decipher CERS6 function in these cell-types.