Topic
Lab-grown 3D neural tissue used to model brain structure, function and developmental disorders.
Nature's editors call for international oversight of brain organoid work after Stanford grafted human organoids into mice lacking almost all their cortex. They write that existing ethics review does not routinely take up the questions such grafts raise.
Reality
Most primate brains carry grooves and ridges. The common marmoset's is nearly smooth, and researchers at the German Primate Center have now traced that difference to the cells that make neurons.
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A UC Berkeley team kept stem-cell-derived organoids in culture for up to a year and found TSC2-mutant astrocytes reactive from the moment they appeared. Helen Bateup says neurons may still contribute to the seizures.
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A Stanford team emptied the mouse neocortex genetically and grew human cortical organoids into the gap, where the grafts took in 25 of 29 animals, expanded nearly fivefold over three months and wired into the host nervous system.
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Mice bred without much of their own neocortex let transplanted human tissue grow bigger and wire up further, and the oversight the team describes is expert guidance plus a committee the university assembled.
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Sergiu Pasca's Stanford group deleted most of the mouse cortex and hippocampus, then filled the space with human cells. The evidence in Nature that the graft contributes to cognition is a maze test.
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The oldest human brain organoids on record matured for seven years with no body attached, and one experiment showed their developmental schedule can be pushed forward.
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Arlotta's group at Harvard cultured cortical organoids past five years and got the gene activity of a 4-year-old. The model is longitudinal now, and priced in calendar years.
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UC Irvine's morphogen-guided neocortical organoids hold anteroposterior identity across 200,000 profiled cells. In fragile X lines, one regional marker difference disappears.
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A Nature study reports that mouse organoids make cortical cell types but not the clock that sequences them, and that a third of progenitors get locked into a single fate.
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