Slitrk1 mRNA expression in mouse brain. A,F,K,P: Whole views of coronal sections of E17.5, P2, P7, and adult brain assayed via in situ hybridization with a digoxigenin-labeled antisense riboprobe. Boxes indicate regions where higher magnification images were taken. B,G,L,Q: Magnified views of the neocortex. Slitrk1 is highly expressed in prospective and mature cortical layers 3, 5, and 6, which contain projection neurons. C,H,M,R: Magnified views of the striatum. Slitrk1 is widely expressed in the embryonic striatum and becomes compartmentalized at early postnatal stages. R: Slitrk1 expression is virtually undetectable in adult striatum, with only sparse cells expressing Slitrk1 mRNA. D,I,N,S: Magnified views of the globus pallidus. Slitrk1 is expressed in the developing and adult globus pallidus. E,J,O,T: Magnified views of the thalamus. Slitrk1 is expressed broadly in the developing thalamus and becomes more refined to subsets of prospective thalamic nuclei, including the midline and intralaminar nuclei; mediodorsal, laterodorsal, and parafascicular nuclei; and ventral lateral and ventral posterior complex (see Results). CP, cortical plate; MZ, marginal zone; 3, 5, 6, cortical layers 3, 5, and 6; SP, subplate. Scale bar = 200 µm in T (applies to B–E,G–J,L–O,Q–T).