Differential nuclear architecture of striatal neurons

<strong>Background:</strong><br>The striatum is composed by five different neuronal populations of which the MSNs constitute the<br>major cell type (~95%). The remaining ~5% of the striatal neurons comprise aspiny interneurons,<br>which have been classified on the basis of their morphology, protein content and electrophysiological properties as large cholinergic interneurons and somatostatin-, parvalbumin- and calretinin-expressing<br>GABAergic interneurons. In addition to these discriminative features, we showed that nuclear morphology is also particular for each striatal cell type (Matamales, Bertran-Gonzalez et al., 2009). <br>Indeed, the characteristic nuclear architecture of striatal populations is evident on DNA staining with TO-PRO-3, which reveals differences regarding the nuclear diameter, the nuclear shape and the pattern of heterochromatin distribution. Thus, nuclear staining with TO-PRO-3 provides a simple means<br>for the identification of MSNs in the absence of other markers. In addition, the other striatal neurons<br>also have distinct nuclear staining patterns, which allow a good prediction of their nature. This method<br>may be useful to identify striatal neurons in tissue sections and potentially in living tissue, using vital<br>DNA fluorescent dyes. With this simple method we carefully quantified striatal neuronal populations<br>and we clearly showed that all MSNs express either D1R or D2R or both. It will be worth to test<br>whether nuclear architecture in striatal neurons is linked to differences in rates of transcriptional<br>activity. In addition, it will be interesting to analyze whether a correlation between the organization of<br>the nucleus of striatal neurons and their characteristic neuronal activity exists.<br> <br><strong>Figure Legend:</strong> (A-E) Schematic view of striatal neurons nuclear morphology: (A),<br>MSNs; (B), Parvalbumin interneurons; (C), Calretinin interneurons; (D), Somatostatin interneurons; (E), Cholinergic interneurons. The three different features that allow the identification of striatal neuronal populations based on their nuclear architecture are represented: blue line designates nuclear shape; dashed green line and numbers indicate average nuclear diameter (μm); red dots are DNA chromocenters; red line represents heterochromatin rim. For details, see Matamales, Bertran-Gonzalez et al., 2009.<br><br>