FAT4 and Rubinstein-Taybi syndrome due to CREBBP mutations: An exemplary case is the FAT3 gene, encoding an atypical cadherin associated with large brain volume or head size downregulated in CDH8+/− neurons [27], while FAT4, a gene also encoding an atypical cadherin, is upregulated in RSTS neurons and associated with an opposite clinical phenotype, i.e., microcephaly, a universal feature of RSTS patients.