Extended Data Fig. 14: The EC stream supplies CR⁺ and RELN⁺ interneurons to the EC.

a–c, At birth, only a few individual DCX⁺RELN⁺ neurons (arrow) are present in the EC stream (a), whereas the ventral wall of the tLV contains multiple chains of DCX⁺RELN⁺COUPTFII⁺ neurons (b), location of inset shown in Fig. 6m. Some DCX+RELN+COUPTFII+ neurons are observed in the DCX⁺ chains wrapping around the lateral edge of the tLV (c). d, At 7 months of age, DCX⁺RELN⁺ cells are present in some dense clusters within the EC stream. e, Examples of DCX⁺RELN⁺COUPTFII⁺ cells in the EC at 11 months of age (arrows). f, Examples of of RELN⁺COUPTFII⁺ cells in the upper layers of the EC at 2 years of age. g, 38 GW coronal section with high magnification insets of DCX⁺CR⁺TBR1^– cells (arrows) in the EC stream clusters and EC (1–4). These cells are detectable in the EC stream at distal (1), middle (2), and proximal (3) levels relative to the medioventral tLV where the stream breaks away from the ventricle. Many additional DCX⁺CR⁺TBR1^– cells (arrows) are present in the EC (4) at birth, at the putative termini of the stream. h, At birth the EC contains DCX⁺CR⁺COUPTFII⁺ cells. i, At 2 years of age the vast majority of CR⁺ neurons in the EC co-express COUPTFII (inset). These cells display multiple morphologies including unipolar, bipolar, and multipolar. Scale bars: 1 mm (g left), 100 µm (g 1–3 top, h left, i left, a left, b left, c top left, d left, e left), 50 µm (g 4 top, a right insets, b right insets, c bottom and right insets, d right insets, e right, f), 10 µm (g 1–4 bottom, h right, i right). Abbreviations: EC: entorhinal cortex; HP: hippocampus; tLV temporal lobe lateral ventricle.