The left-brain hemisphere of a normal mouse shows the normal level and cellular distribution of the Pax6 gene expression in the developing neocortex. The right-brain hemisphere shows a sustained, primate-like Pax6 expression pattern in the neocortex of a double transgenic mouse embryo. These animals have more Pax6-positive progenitor cells and a higher Pax6 expression level in the germinal layer close to the ventricle in the right hemisphere. (credit: © MPI of Molecular Cell Biology & Genetics)
Researchers at the Max Planck Institute of Molecular Cell Biology and Genetics have created a transgenic mouse in which a gene called Pax6, during embryonic development, is highly expressed in a specific group of brain cortical cells called neural progenitor stem cells (the cells that generate all cells that make up the brain).
The resulting mouse brain generated more neurons than normal and exhibited primate-like features — notably those in the top layer, a characteristic feature of an expanded neocortex.
Mouse basal progenitors, in contrast to human, do not express Pax6. In humans, basal progenitors can undergo multiple rounds of cell division, thereby substantially increasing neuron number and ultimately the size of the neocortex.
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