Branch point evolution controls species-specific alternative splicing and regulates long term potentiation

Regulation and functionality of species-specific alternative splicing has remained enigmatic to the present date. Calcium/calmodulin-dependent protein kinase II{beta} (CaMKII{beta}) is expressed in several splice variants and plays a key role in learning and memory. Here, we identify and characterize several primate-specific CAMK2B splice isoforms, which show altered kinetic properties and changes in substrate specificity. Furthermore, we demonstrate that primate-specific Camk2{beta} alternative splicing is achieved through branch point weakening during evolution. We show that reducing branch point and splice site strengths during evolution globally renders constitutive exons alternative, thus providing a paradigm for cis-directed species-specific alternative splicing regulation. Using CRISPR/Cas9 we introduced a weaker human branch point into the mouse genome, resulting in human-like CAMK2B splicing in the brain of mutant mice. We observe a strong impairment of long-term potentiation in CA3-CA1 synapses of mutant mice, thus connecting branch point-controlled, species-specific alternative splicing with a fundamental function in learning and memory.