Figure 6: Sox14 and Otx2 are co-expressed in the embryonic tectum and both define the dLGN-IN population.

ISH for Otx2 and IHC for GFP showing the location of double-positive Sox14⁺Otx2⁺ cells before (E17.5) and after (P3) birth in Sox14^Gfp/+ brains. (a) At E17.5 Gfp⁺ and Otx2⁺ neurons occupy adjacent domains of the vLGN (inset 1) and of the pretectum (inset 3). Sox14⁺Otx2⁺ double-positive neurons are present in the outermost region of the superior colliculus (SC) and forming a stream of cells that extends from the SC towards the dLGN along the surface of the brain (white arrows in inset 2). (b) At P3 Sox14⁺Otx2⁺ double-positive neurons are clearly visible in the dLGN and scattered in other thalamic nuclei. Furthermore, some double-positive neurons are also present in the IGL and vLGN (white arrows) and quantified in d. (c) The stream of Sox14⁺Otx2⁺ double-positive neurons lining the brain at the level of pretectum and thalamus is highlighted with white arrows. (d) Quantification of the relative distribution of Sox14⁺Otx2⁺ double-positive neurons in the three domains of the LGN (dLGN: 75.96±3.71; vLGN: 14.93±2.18; IGL: 9.10±1.75; %, mean±s.e.m.; n=531 cells from 3 brains) and the relative numbers of double-positive and single-positive neurons in the dLGN (Gfp⁺Otx2⁺: 92.15±0.47; Gfp⁺: 6.23±0.36; Otx2⁺: 1.62±0.81; %, mean±s.e.; n=651 cells from 3 brains). (e) Schematic summary of the distribution of Sox14⁺Otx2⁺ double-positive and single-positive neurons across the thalamic (p3 and p2), pretectal (p1) and SC territories, before and after birth. Scale bars, 100 μm.