Characterization of knockin mice at the <i>Rosa26</i>, <i>Tac1</i> and <i>Plekhg1</i> loci generated by homologous recombination in oocytes

<div><p>Design and engineering of complex knockin mice has revolutionized the <i>in vivo</i> manipulation of genetically defined cells. Recently development of the bacterial clustered regularly interspersed short palindromic repeats (CRISPR) associated protein 9 (Cas9) system for single site cleavage of mammalian genomes has opened the way for rapid generation of knockin mice by targeting homology directed repair to selected cleavage sites. We used this approach to generate new lines of mice that will be useful for a variety of aspects of neuroscience research. These lines have been bred to homozygosity and details of the expression and function of the transgenes are reported. Two lines target the <i>Rosa26</i>-locus and have been engineered to allow Cre-dependent expression of the avian tva receptor, and Cre-dependent expression of a cell surface targeted spaghetti-monster carrying many copies of the “ollas-tag”. Another line expresses red fluorescent protein and tva in <i>Tac1</i>-positive neurons; the fourth line targets FlpO expression to <i>Plekhg1</i> expressing neurons, providing a powerful approach to modify gene expression in thalamic excitatory neurons.</p>