The experiments showed that the human and chimpanzee brain organoids were remarkably similar in many ways including in the mix of cell types and in how these cells were arranged. have now analysed brain organoids grown from reprogrammed human, chimpanzee and orangutan cells. Mora-BermГєdez, Badsha, Kanton, Camp et al. Recently, researchers have been able to use these reprogrammed cells to make tissue that resembles the brain in petri dishes, known as brain organoids. Under the right conditions, cells collected from adult humans and other animals can be reprogrammed to behave like brain stem cells. To study the earliest stages of brain development, researchers often use human brain cells grown in the laboratory. How these species differences arise is not clear, but it likely occurs in the earliest phases of development when brain stem and progenitor cells divide and give rise to cerebral cortex cells in the growing brain. Networks of brain cells in the cerebral cortex also behave differently in the two species. Moreover, a part of the brain called the cerebral cortex вЂ“ which plays a key role in memory, attention, awareness and thought вЂ“ contains twice as many cells in humans as the same region in chimpanzees.

The human brain is about three times as big as the brain of our closest living relative, the chimpanzee.

These subtle differences in cortical progenitors between humans and chimpanzees may have consequences for human neocortex evolution. Consistent with this, the small set of genes more highly expressed in human apical progenitors points to increased proliferative capacity, and the proportion of neurogenic basal progenitors is lower in humans. Notably, however, live imaging of apical progenitor mitosis uncovered a lengthening of prometaphase-metaphase in humans compared to chimpanzees that is specific to proliferating progenitors and not observed in non-neural cells. We find that the cytoarchitecture, cell type composition, and neurogenic gene expression programs of humans and chimpanzees are remarkably similar. Here, we have searched for such differences by analysing cerebral organoids from human and chimpanzees using immunohistofluorescence, live imaging, and single-cell transcriptomics. This expansion is thought to primarily reflect differences in proliferation versus differentiation of neural progenitors during cortical development. Human neocortex expansion likely contributed to the remarkable cognitive abilities of humans.

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