A glycine transporter 2-Cre knock-in mouse line for glycinergic neuron-specific gene manipulation.

Glycine is an inhibitory neurotransmitter in the brainstem and spinal cord. Glycine transporter 2 (GLYT2) is responsible for the uptake of extracellular glycine. GLYT2 is specifically expressed in glycinergic neurons and thus has been used as a marker of glycinergic neurons. Here, we generated GLYT2 promotor-driven Cre recombinase (Cre)-expressing mice (GLYT2-Cre knock-in mice) to develop a tool for manipulating gene expression in glycinergic neurons. Cre activity was examined by crossing the GLYT2-Cre knock-in mice with a Cre reporter mouse line, R26R, which express β-galactosidase (β-gal) in a Cre-dependent manner. X-gal staining of GLYT2-Cre/R26R double transgenic mouse brains and spinal cords revealed that the Cre activity was primarily distributed in the brainstem, cerebellum, and spinal cord. These areas are rich in glycinergic neurons. Furthermore, we performed immunohistochemistry for β-gal combined with hybridization for GLYT2 in the GLYT2-Cre/R26R double transgenic mouse brains to determine whether Cre activity is specifically localized to glycinergic neurons. The β-gal protein and GLYT2 mRNAs were colocalized in the cerebellar Golgi cells, dorsal cochlear nucleus, gigantocellular reticular nucleus, spinal trigeminal nucleus, nucleus of the trapezoid body, and lateral lemniscus. More than 98% of the GLYT2 mRNA-expressing cells in these brain regions also expressed β-gal, whereas 90-98% of the β-gal-positive cells expressed the GLYT2 mRNAs. Thus, Cre activity is specifically localized to glycinergic neurons with high fidelity in the GLYT2-Cre knock-in mice. The GLYT2-Cre knock-in mouse line will be a useful tool for studying glycinergic neurons and neurotransmission.