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Researchers used brain organoid models derived from Down syndrome patients to study how the extra copy of chromosome 21 affects the development of oligodendrocytes, the cells responsible for producing myelin that insulates nerve fibers. They found that trisomy 21 causes an accumulation of immature, pre-myelinating oligodendrocytes that fail to properly mature and produce normal myelin, despite increased contact with neurons. This developmental disruption appears to uncouple the normal progression from oligodendrocyte differentiation to functional myelin production, potentially explaining the impaired brain connectivity observed in Down syndrome.
Why it matters
This study identifies a specific cellular mechanism underlying intellectual disability in Down syndrome, revealing that the condition disrupts not just neuron development but also the critical process of myelination. Understanding this developmental bottleneck could inform future therapeutic strategies aimed at promoting proper oligodendrocyte maturation and improving brain connectivity in individuals with Down syndrome.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Intellectual disability is a hallmark of Down syndrome (DS), caused by the triplication of human chromosome 21. Abnormal neuronal connectivity and impaired myelination are consistently observed in DS, yet the underlying mechanisms remain poorly understood. Here, we used DS-derived isogenic induced pluripotent stem cell-derived forebrain assembloids (FAs) to investigate oligodendrocyte lineage cell (OLLC) development and neuron-glia interactions. Trisomic FAs exhibited an expansion of BCAS1+ pre-myelinating OLLCs, without a corresponding increase in myelin basic protein (MBP) expression. Transcriptomic analyses identified a euploid-enriched, trophic and maturation-supportive state (OLLC_2-TMS) and a trisomy-enriched synaptic interactions and differentiation state (OLLC_3-SID), lacking coordinated enrichment in myelination-promoting programs. Corresponding transcriptional signatures were identified in OLLCs from early postnatal human cortex. Increased excitatory neuronal contacts with pre-myelinating OLLCs accompanied ultrastructural myelin abnormalities in trisomic assembloids. Our findings suggest that trisomy redirects OLLC development toward a pre-myelinating state, uncoupling oligodendrocyte differentiation from productive myelination.