CCNB1IP1 regulatory evolution underlies gradual increases in cortical size and folding in primates.

Evolutionary increases in CCNB1IP1 expression are linked to cortical size and folding in primates, with knock-in experiments inducing cortical folding in mice.

• Why it matters: Understanding the molecular basis of cortical expansion and folding is crucial for insights into human cognitive evolution, yet these mechanisms are not fully known.
• What they did: Researchers identified CCNB1IP1 as a key regulator by comparing primates and tree shrews, analyzing cis-regulatory elements, and manipulating gene expression in mice through overexpression and knock-in approaches.
• The result: Elevated CCNB1IP1 expression correlates with increased cortical size and folding, and its knock-in in mice induces cortical folding, suggesting its role in primate brain evolution.