Extended Data Fig. 4: mGRASP and synaptophysin labelling provide evidence for output segregation of the two MD cell types.
From: Thalamic circuits for independent control of prefrontal signal and noise
a, Cartoon depicting strategy to label cell type specific MD→PL thalamocortical synapses using mGRASP. The pre mGRASP component is virally expressed in MDD2 or MDGRIK4 neurons in the respective Cre lines while the post mGRASP component is ubiquitously expressed in the PL. MDD2 or MDGRIK4 specific mGRASP synapses onto VIP vs PV neurons in the PL are identified by immunohistochemistry guided detection of PV and VIP neurons expressing post mGRASP in the PL. b–c, Left: Representative images of MDD2 (b) and MDGRIK4 (c) neurons expressing pre mGRASP in the MD of D2-cre and GRIK4-cre mice respectively. Right: Ubiquitous expression of post mGRASP+ neurons detected by TdTomato fluorescence in the PL of D2-cre (b) and GRIK4-cre (c) mice. Scale bar in µm: 200. d, Left to right: Examples of PL VIP+ neurons showing post mGRASP expression (magenta), VIP expression detected via immunohistochemistry (yellow) and mGRASP+ synapses from MDD2 (cyan dots, top row) or MDGRIK4 (cyan, dots, bottom row) neurons. e, Same as in d, for PL PV+ neurons. Scale bars in µm: 3 µm. f, Representative images showing layer-wise termination of synapses from MDD2 (left) and MDGRIK4 (right) neurons in the PL, labelled with virally expressed GFP fused to synaptic protein (synaptophysin). Scale bar in µm: 100. g, MDD2 neurons terminate in L1 of the PL with a higher frequency compared to MDGRIK4 neurons (n = 12 sections each from 3 D2-cre and 3 GRIK4-cre mice, *p = 0.0253, *p = 0.039, two-tailed Mann-Whitney U test comparing 50 µm bins from the pial surface across groups). All statistical tests are two-tailed. Data are presented as mean ± SEM for g
