(Epi)transcriptomic analysis of an in vitro human neurogenesis model upon modulation of cannabinoid CB1 receptor signaling

• Applicant: Constance Vennin, Ph.D.
• Subject Area: Experimental Models for the Understanding of Nervous System Diseases
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 495867535

Endocannabinoids and their receptors constitute a widespread lipid signaling system in vertebrates, both in the adult, but also in the embryo. During brain development, endocannabinoids regulate neuronal progenitor proliferation, differentiation, migration and the establishment of axonal connectivity. External factors (e.g., stress, drugs, etc.) can challenge neural development, leading to dysregulation of these processes and, in consequence, to long-lasting and irreversible alterations in brain function and behavior later in life. For the human cannabinoid type 1 receptor (CB1), over stimulation has been described to promote hyperactivity, anxiety, learning deficits, and predisposition for cannabis abuse in adolescence and adulthood. The cellular mechanisms underlying the increased susceptibility towards these mental disorders are not understood and represent the focus of my project. In rodents, CB1 regulates gene expression by inducing epigenetic reprogramming. Therefore, I hypothesize this mechanism to occur during human neurogenesis. To shed light onto these complex processes in models of early human brain development, I will take advantage of the cutting-edge technology of human induced pluripotent stem cells (hiPSCs) and human brain organoids, which I have recently established in the lab. In the first work package, hiPSC-derived neural progenitor cells (NPC) will be differentiated into cortical excitatory and inhibitory neurons, respectively, in the absence or presence delta 9-tetrahydrocannabinol (THC), the main psychotropic component of cannabis. Then, the transcriptome and the epigenome of these neurons will be determined by RNA-seq and Chromatin Immunoprecipitation-seq. In the second work package, 3-dimensional human brain organoids will be generated under THC treatment. I will investigate the impact of the THC treatment on neuronal differentiation at different brain organoid maturation stages by immunostaining for progenitor and neuronal markers but also by single-cell RNA-seq, enabling to identify the different neuronal cell populations present within the brain organoids at different time points of their development. The single-cell RNA-seq will provide information about the dynamic trajectory of brain development and how a dysregulation of the endocannabinoid system impairs it. I will also decipher the effect of THC treatment on neuronal connectivity and activity by using light-sheet fluorescent microscopy and electrophysiological analyses. Collectively, in a model of human embryonic brain development, I will highlight the role of the endocannabinoid system and the mechanisms underlying increased susceptibility towards mental disorders.

• DFG Programme: Research Grants