Unraveling LIS1-Lissencephaly: Insights from Cerebral Organoids Suggest Severity- Dependent Genotype-Phenotype Correlations, Molecular Mechanisms and Therapeutic Strategies

Lissencephaly is a developmental cortical malformation characterized by reduced to absent gyri and a disorganized cortex, often leading to severe impairments in affected individuals and a reduced life expectancy. Heterozygous mutations in the LIS1 gene, encoding a regulator of the microtubule motor dynein, cause lissencephaly with different clinical severities. While the clinical disease spectrum correlates with the degree of lissencephaly, location and type of mutation may not. We leveraged forebrain-type organoids from LIS1-lissencephaly patients, diagnosed with mild, moderate or severe lissencephaly to investigate, in a cytoarchitecture and multi-omics approach, how the severity degree in patients might relate to specific mutations in the LIS1 gene. We questioned which processes during cortical development might be differentially affected by severity grade, and whether they could be pharmacologically targeted. We found alterations in neurodevelopment often with a severity- dependent gradient. Specifically, we identified alterations of the cytoarchitecture, progenitor cell homeostasis and neurogenesis. Particularly important disease-linked molecular mechanisms were microtubule destabilization, WNT-signaling, and perturbed cadherin- and unfolded protein-binding. Some mechanisms exhibited a severity-dependent gradient, or were specific to a severe grade. We present strategies to reverse phenotypic changes in LIS1- patient organoids, and an in silico approach with therapeutic potential. Thus, we show that different LIS1-severity grades can be recapitulated in vitro , that there is a direct link between the phenotype and genotype, that organoid-based disease modeling can identify molecular underpinnings of malformations of cortical development and that organoids provide a valid platform to develop and test therapeutic strategies. ### Competing Interest Statement The authors have declared no competing interest.