MTSS2 and syndromic intellectual disability: Since its discovery, ABBA has gained broader interest due to two significant findings: first, its mRNA expression increases upon exercise-induced activation of granule neurons in the dentate gyrus of the hippocampus, and it was required for exercise-induced increase in dendritic spine density [2]; second, a missense mutation in MTSS2, a human gene encoding ABBA, was found to cause intellectual disability syndrome [3].