Altered extracellular matrix structure and elevated stiffness in a brain organoid model for disease
Mutations in Lissencephaly 1 (LIS1) result in various human brain developmental diseases, such as changes in brain structure, lissencephaly, and epilepsy. RNA-sequencing data from on-chip organoids derived from human embryonic stem cells (hESCs) revealed significant changes in the expression of extracellular matrix (ECM) – related genes in LIS1+/- samples. This project examined the biomechanical properties of LIS1+/- mutated and healthy hESCs-derived cortical organoids. A rheological test using the pipette aspiration technique revealed that LIS1+/- cortical organoids are stiffer than control organoids. The increased stiffness of the LIS1+/- cortices was proportional to an increased expression of the nuclear mechano-sensing protein, Lamin A, highlighting the adverse cellular and nuclear changes underlying the stiffening of LIS1+/- organoids. To delineate the ECM composition associated with the stiffening effect in LIS1+/-, healthy and mutated hippocampal and cortical organoids were examined at the protein, mRNA, and miRNA levels. Whole RNA sequencing showed altered expression of multiple collagen-related pathways, including the 'collagens containing ECM' and the 'Collagen trimer' pathways. Differential mRNA expression has inversely correlated with the expression of their targeting miRNAs in the LIS1+/- organoids. This inverse miRNA-mRNA expression was most pronounced in genes associated with the ECM-receptor signalling pathway. At the protein level, the mutated hippocampal organoids showed unilateral, substantial increased expression of collagens and proteins involved in collagen synthesis, modification, and remodelling. Following a collagenolytic treatment with the catalytic domain of the MMP9 enzyme, the stiffness levels in the LIS1+/- organoids were reduced to control values. Overall, this work provides new information about the role of LIS1 in controlling collagen expression and the abnormal mechanical properties associated with mutation to the LIS1 gene in the development of the human cortex and hippocampus. Overall design: Expetiment1-2: RNA-seq (exp.1) and small RNA-seq (exp.2) were used to compare the expression of 105-days-old wild type and LIS1+/- cortical organoids derived from human embryonic stem cells. In another experiment (Exp.3), RNA seq was used to compare the expression of wild-type and LIS1+/- brain organoids derived from human embryonic stem cells, with and without MMP9 catalytic domain treatment. Each biological repeat included 8-10 organoids on day 105 or 8-10 on day 18.