Figure 3. The Cxcr4 lineage contributes to mDA neurons between E11.5 and E15.5. A, Experimental timeline. B, Coronal view of the adult ventral midbrain. mDA neurons are indicated in green. Red box indicates area shown in D, E, F, G, and H. C, Schematic indicating the medial SNc (m_SN), lateral SNc (l_SN), dorsal VTA (d_VTA), and ventral VTA (v_VTA). Fate-mapped cells in these areas are quantified in I. D, E, F, G, H, Immunostaining for tdT (red) and TH (green) on P30 coronal midbrain sections. Rli, Rostral linear nucleus; RN, red nucleus. D′, E′, F′, G′, H′, Area in the VTA indicated by the box (dashed line) in D, E, F, G, and H. D′′, E′′, F′′, G′′, H′′, Area in the SNc indicated by the box (solid line) in D, E, F, G, and H. E′–H′′, Arrowheads indicate tdT-expressing cells with glial morphology. D–D′′, With TM11.5, most cells in the ventral midbrain appear to be positive for tdT, including almost all mDA neurons. E–E′′, With TM12.5, some mDA neurons do not coexpress tdT (indicated by asterisks). F–G′′, With TM13.5 and TM14.5, many tdT-positive mDA neurons (indicated by arrows) are present in the ventral part of the VTA. In the SNc, double-labeled mDA neurons are almost completely restricted to the medial SNc. H–H′′, With TM15.5, only very few tdT-expressing mDA neurons are present and none are found in the examples in H′ and H′′. I, Quantitative analysis of tdT-expressing cells in the P30 midbrain. The percentage of tdT-expressing TH-positive mDA neurons was determined in m_SN, l_SN, d_VTA, and v_VTA as shown in the schematic in C. With TM13.5, TM14.5, or TM15.5, the Cxcr4 lineage does essentially not contribute to mDA neurons in the l_SN. With TM15.5, the few labeled mDA neurons are restricted to the d_VTA and v_VTA. J–J′′, Immunostaining for tdT (red) and glutamine synthetase (GS; green), an astrocyte marker on P30 coronal midbrain sections. TM was administered at E12.5. Scale bars: D, E, F, G, H, 200 μm; J, 50 μm. Analysis of the contribution of the Cxcr4 lineage to mDA neurons and other midbrain areas at E18.5 (Extended Data Figs. 3-1, 3-2).