Lithium as a positive modulator of defective WNT pathway in Cornelia de Lange Syndrome models

The cohesin complex is a multimeric system, highly conserved in the course of cellular evolution from the most primitive life forms to human cells. Cohesins are essential Structural Maintenance of Chromosomes (SMC), protein-containing complexes that interact with chromatin and modulate chromatin organization and gene expression. Genetic variants that cause structural and/or functional alterations induce an array of congenital pathologies named "cohesinopathies". It is believed that such malformations arise from deregulation of pivotal developmental molecular pathways. Canonical WNT pathway has been shown to be perturbed in association with central nervous system malformation in Cornelia de Lange Syndrome (CdLS), one of the most characterized cohesinopathy. In this study, we validated the relevance of canonical WNT pathway and assess the effect of LiCl-dependent activation of WNT pathway in three CdLS experimental models: Lymphoblastoid cell lines from patients, murine Neural Stem Cells (NSCs) and Drosophila melanogaster. Methods Lymphoblastoid cells (immortalized lines from CdLS patients) of patients carrying mutations of NIPBL or HDAC8 genes and healthy donors were used in these studies. These cells were treated with LiCl 1mM, 2,5mM and 5mM, and vehicle and proliferation rate were measured. Proliferation and differentiation capabilities were also assessed in CdLS NSCs upon LiCl treatment. Flies were grown upon food added with a different concentration of LiCl. Drosophila brains were analyzed for morphological evaluation. Results and conclusions Preliminary data on lymphoblastoid cells showed no effects on cell death rate in healthy donor following LiCl treatment. And, although with a patient-specific response, LiCl appeared to induce an increase in proliferation, especially in cell lines that were slow-growing compared to controls. NSCs showed reduced NSCs proliferation rate and differentiating capabilities. The presence of lithium could reduce the detrimental effects in a significant way. Drosophila mutants for nipped-B gene, the ortholog of human NIPBL, display malformations in mushroom bodies (MB), a structure involved in olfactory learning and memory. Treating subsequent generation of flies with 100mM of LiCl, MB morphology was restored in the offspring. All these data further confirm the hypothesis that in “cohesinophaties” is present an impairment of WNT pathway that could, in part, explain the typical neurodevelopmental alterations of this syndrome. Moreover, these studies could pave the way for future therapeutic strategies.