SPARC: a method to genetically manipulate precise proportions of cells

Many experimental approaches rely on controlling gene expression in select subsets of cells within an individual animal. However, reproducibly targeting transgene expression to specific fractions of a genetically-defined cell-type is challenging. We developed parse redictive ctivity through ecombinase ompetition (SPARC), a generalizable toolkit that can express any effector in precise proportions of post-mitotic cells in . Using this approach, we demonstrate targeted expression of many effectors and apply these tools to calcium imaging of individual neurons and optogenetic manipulation of sparse cell populations .