This transgene expresses Cre recombinase under the control of a rat synapsin I promoter. Cre recombinase activity is detected in neuronal cells, including brain, spinal cord and DRGs, as early as E12.5, as well as in neurons in adult. Line 671 contains 10 copies of the transgene inserted into chromosome 6 over 1 Mb from the nearest gene (chr6:10,423,318; NCBI37/mm9) with a duplication of unknown size at the insertion site. (J:68558)