Extended Data Fig. 3: In the somatosensory TRN of postnatal SOM-Cre mice, both Cre expression and viral Cre-dependent protein expression are restricted mainly to SOM cells along the edges.
From: Two dynamically distinct circuits drive inhibition in the sensory thalamus
a, Epifluorescence images of virally induced, SOM-Cre-dependent GFP expression patterns in TRN (live 300-μm-thick slices from 7 mice). Virus carrying a Cre-dependent GFP gene (AAV9-DIO-GFP) was injected throughout the TRNs of SOM-Cre × tdTomato or SOM-Cre × ICR mice. This drove GFP expression (green) in SOM cells that expressed Cre at or after the time of the virus injection (age at injection P17.1 ± 1.18 days; age at imaging 26.8 ± 1.19). Mouse 1: images of GFP alone and overlay of GFP and genetically labelled tdTomato cells. Mice 2–7: GFP alone. Within the somatosensory TRN, expression of SOM-Cre × GFP was restricted to the edges of the nucleus and excluded from the central zone after early development. Experiment replicated 12 times. b, Same as in a except using PV-Cre mice (age at virus injection P14; age at imaging P23). Nearly all of the TRN cells expressed both genetically labelled PV-Cre × tdTomato and virally induced PV-Cre × GFP. In addition to demonstrating ubiquitous postnatal PV-Cre expression across the TRN, these results show that the virus has no obvious tropisms for different topographic regions of the TRN. Experiment replicated 4 times. c, Confocal images of Pvalb, Sst, and Cre mRNA expression through the TRN of a P27 SOM-Cre heterozygous mouse (18 μm thick section). The overall patterns of Sst and Cre mRNA labelling were nearly identical (experiment replicated in 5 sections from 4 mice). d, Sst and Cre mRNA were generally expressed in the same neurons (total counts: 167 cells, 5 sections, 4 mice; measured in the somatosensory sector of the TRN). Of the Cre-expressing cells, 88.3 ± 0.1% expressed Sst mRNA. Of the Sst-expressing cells, 96.1 ± 0.01% expressed Cre mRNA. e, AAV9-DIO-GFP injections into the TRNs of postnatal SOM-Cre mice led to GFP expression patterns that were very similar to Sst mRNA patterns. Left, DIC and epifluorescence images from a live 300-μm-thick section expressing AAV9-DIO-GFP (9 days after virus injection) in a SOM-Cre heterozygous mouse. This experiment was replicated 12 times (see a, Fig. 1g and Extended Data Fig. 1a for additional examples). f, Same as e but virus was injected into a wild-type mouse (ICR strain; no Cre expression) (tested in n = 2 mice). Matching display settings were used for the slices in c and d. The lack of fluorescent signal indicates that the AAV-DIO-GFP virus used here drives GFP expression only in Cre-expressing cells. Data are mean ± s.e.m.
