@inproceedings{01JDA6125TRGB41924FA41Q69N,
  abstract     = {{Ghent University
FOXG1 is a transcription factor highly and specifically expressed in the developing brain. Heterozygous loss-of-function of FOXG1 causes a severe neurodevelopmental disorder called FOXG1 syndrome. FOXG1 is involved in regulating the proliferation of neural progenitor cells (NPCs) and reduced dosage is associated with NPCs prematurely exiting the cell cycle and starting neuronal differentiation. In addition, aberrant FOXG1 dose is associated with an imbalance in the ratio of glutamatergic versus GABAergic neurons. However, there is no consensus in literature yet about the direction of this imbalance. Our goal is to thoroughly study the function and characterise the effects of FOXG1 Loss of Function (LoF). 
Using CRISPR-Cas9, we developed several potential FOXG LoF iPSC lines. Since neural organoids are a promising stem cell-derived 3D tissue model recapitulating early human brain development, we generated minimally guided cerebral organoids from the different FOXG1 iPSC lines. After 35 days of differentiation, these organoids were compared with isogenic controls using immunostainings, quantitative polymerase chain reaction (qPCR) and single cell RNA sequencing (scRNA-seq) techniques.
First of all, the variability in 35 days old control organoids was apparent. Immunostainings and qPCR results showed that not all control organoids were able to induce FOXG1 expression, pointing to the limited reproducibility of forebrain formation using the minimally guided cerebral organoid protocol. Further, scRNA-seq revealed a disproportionally bigger cluster of choroid plexus cells in control organoids which failed to induce FOXG1 expression, while radial glial cells and neurons were almost absent in these organoids. This lack in reproducibility complicates the reliable interpretation of results based on the different genotypes. However, regardless of the genotype, a significant positive correlation was found between FOXG1 expression and the ratio of glutamatergic over GABAergic neurons. 
In addition, compound heterozygous frameshift mutations in FOXG1 led to a decrease in radial glia and intermediate progenitor cells, while the heterozygous frameshift appears to result in less intermediate progenitors and more neurons. Differential expression analysis between control and heterozygous radial glia cells revealed a list of 14 genes significantly upregulated in radial glia cells with a heterozygous frameshift mutation in FOXG1 and gene set enrichment analysis showed that this gene list is enriched for terms related to neuronal development. Since FOXG1 is mainly known as a transcriptional repressor, insufficient amount of functional FOXG1 might be the cause of this upregulation.
In conclusion, these results suggest that the induction of FOXG1 is a tightly controlled process and the regulatory mechanisms behind it are not yet fully understood. Insufficient amounts of functional FOXG1 in our 35 days old organoids seemed to be correlated with premature neuronal differentiation and a lower ratio of glutamatergic to GABAergic neurons. Differential expression analysis in radial glia revealed candidate genes that are potentially repressed by FOXG1. Further research towards the downstream targets of FOXG1 as well as the regulation of FOXG1 expression itself is necessary in order to improve diagnostics and develop treatments for patients with FOXG1 syndrome.}},
  author       = {{Van Loon, Nore and Genbrugge, Lukas and Van Wetter, Emiel and Godefroy, Fynn Maximilian and Vaughan, Michael B and Hamerlinck, Lisa and Colombo, Lara and Leimbacher, Sebastian and Vantomme, Lies and Daal, Esperanza and Dmitriev, Ruslan and Vergult, Sarah}},
  booktitle    = {{2024 EMBO Workshop 'Unlocking human brain complexity using 3D culture and single-cell omics', Abstracts}},
  language     = {{eng}},
  location     = {{Capri, Italy}},
  title        = {{Assessing the effect of aberrant FOXG1 expression in neural organoids}},
  url          = {{https://meetings.embo.org/event/24-single-cell-omics}},
  year         = {{2024}},
}