A035 Identification of neurodevelopmental organization of the ChP cell population and TTR in HD fused organoids

<h3></h3> The impact of Huntington’s Disease (HD) on neurodevelopment is still not fully elucidated. Our latest study demonstrates a new fused dorso-ventral forebrain organoid model of HD for providing new insights into the altered cellular organization of brain structures in HD neurodevelopment. The dorso-ventral organoids from juvenile HD or control iPSC mimick cortex and striatum brain regions affected in HD. HD organoids grew significantly larger than the control and showed more NSC rosettes and specific gene expression profiles, indicating a commitment to proliferation over differentiation. We demonstrate that a molecular marker TTR is highly upregulated as early as brain dorso-ventral organoids and embryonic brains of the Hu128/21 HD mouse model. By scRNAseq, we found that both HD models also show upregulation of a specific choroid plexus (ChP) cell population, which hardly occurs in control 60-day organoids and control embryos. Increased TTR expression in human HD organoids and mosaic organoids, HD mouse embryos, and the HD mouse blood serum underscores TTR’s potential significance in HD pathogenesis. ChP population early growth and the indication that early TTR biomarkers can be identified in blood serum may enable very early detection and monitoring of HD. Our results connecting the TTR marker and ChP structure brain and its increased cellular population in organoids and embryos may ultimately lead to developing novel and more effective HD therapies that target the ChP.