TY - JOUR T1 - The Role of the First Postmitotic Cortical Cells in the Development of Thalamocortical Innervation in the <em>Reeler</em>Mouse JF - The Journal of Neuroscience JO - J. Neurosci. SP - 5746 LP - 5765 DO - 10.1523/JNEUROSCI.18-15-05746.1998 VL - 18 IS - 15 AU - Zoltán Molnár AU - Richard Adams AU - AndréM. Goffinet AU - Colin Blakemore Y1 - 1998/08/01 UR - http://www.jneurosci.org/content/18/15/5746.abstract N2 - In the mutant mouse reeler, the tangential distribution of thalamocortical fibers is essentially normal, even though neurons of the cortical plate accumulate below the entire early-born preplate population (Caviness et al., 1988). This seems incompatible with the hypothesis that cells of the subplate (the lower component of the preplate in normal mammals) form an axonal scaffold that guides thalamic fibers and act as temporary targets for them (Blakemore and Molnár, 1990, Shatz et al., 1990).We used carbocyanine dyes to trace projections in wild-type andreeler mice between embryonic day 13 and postnatal day 3. Preplate formation and early extension of corticofugal fibers to form a topographic array are indistinguishable in the two phenotypes. So too are the emergence of thalamic axons in topographic order through the primitive internal capsule, their meeting with preplate axons, and their distribution over the preplate scaffold. Distinctive differences appear after the cortical plate begins to accumulate below the preplate of reeler, causing the preplate axons to form oblique fascicles, running through the cortical plate. Thalamic axons then pass through the plate within the same fascicles and accumulate in the “superplate” layer for ∼2–3 d, before defasciculating and plunging down to terminate deep in the cortical plate, creating the curious “looping” pattern seen in the adult. Thus, thalamocortical innervation in reeler follows the same algorithm of development but in relation to the misplaced population of early-born neurons. Far from challenging the theory that preplate fibers guide thalamic axons, reeler provides strong evidence for it. ER -