Rasanen, N. | bioRxiv Science

bioRxiv2025

Astrocytic-supplied cholesterol drives synaptic gene expression programs in developing neurons and downstream astrocytic transcriptional programs

Astrocytes participate in neuronal synaptic programs that are enriched for genetic associations in schizophrenia and autism spectrum disorders (ASD). To better understand how these co-regulated cellular programs are induced during early neuronal development, we studied astrocytes and iPSC-derived neurons in co-cultures and mono-cultures at 16 time points spanning 0.5 hours to 8 days. We found that upregulation in astrocytes of genes involved in cholesterol biosynthesis preceded the activation of synaptic gene programs in neurons and upregulation of the astrocytic Nrxn1. Neuronal knockdown of key cholesterol receptors led to downregulation of neuronal synaptic genes and induced a robust transcriptional response in the astrocytes, including further upregulation of Nrxn1. This suggests that astrocyte-supplied cholesterol drives these neuronal changes and that bi-directional signalling is occuring. The genes upregulated in neurons were enriched for deleterious variants in schizophrenia and neurodevelopmental disorders, suggesting that their pathogenic effect may be, in part, mediated by reduced buffering capacity for changes in the astrocyte cholesterol supply to neurons. These findings highlight the critical role of astrocyte-neuron interactions in psychiatric and neurodevelopmental disorders, particularly in relation to lipid metabolism and synaptic plasticity.

molecular biology↗

bioRxiv2023

Astrocytes regulate neuronal network burst frequency through NMDA receptors species- anddonor-specifically

BackgroundDevelopment of synaptic activity is a neuronal key characteristic that relies largely on interactions between neurons and astrocytes. Although astrocytes have known roles in regulating synaptic function and malfunction, the use of human or donor-specific astrocytes in disease models is still rare. Rodent astrocytes are routinely used to enhance neuronal activity in cell cultures, but less is known how human astrocytes influence neuronal activity. MethodsWe established human induced pluripotent stem cell (hiPSC)-derived neuron-astrocyte co-cultures and studied their functional development on microelectrode array (MEA). We used cell lines from 5 neurotypical control individuals and 3 pairs of monozygotic twins discordant for schizophrenia. A method combining Ngn2 overexpression and dual SMAD inhibition was used for neuronal differentiation. The neurons were co-cultured with hiPSC-derived astrocytes differentiated from 6-month-old astrospheres or rat astrocytes. ResultsWe found that the hiPSC-derived co-cultures develop complex network bursting activity similarly to neuronal co-cultures with rat astrocytes. However, the effect of NMDA receptors on neuronal network burst frequency (NBF) differed between co-cultures containing human or rat astrocytes. By using co-cultures derived from patients with schizophrenia and unaffected individuals, we found lowered NBF in the affected cells. We continued to demonstrate how astrocytes from an unaffected individual rescue the lowered NBF in the affected neurons by increasing NMDA receptor activity. ConclusionsOur results indicate that astrocytes participate in the regulation of neuronal NBF through a mechanism involving NMDA receptors. These findings shed light on the importance of using human and donor-specific astrocytes in disease modeling.

neuroscience↗