Characterization of Sonic Hedgehog transcripts in the adult mouse brain: co-expression with neuronal and oligodendroglial markers

• Published in: Brain Structure and Function Vol. 229; no. 3; pp. 705 - 727
• Main Authors: Russo, Mariagiovanna, Pellegrino, Giuliana, Faure, Hélène, Tirou, Linda, Sharif, Ariane, Ruat, Martial
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.04.2024; Springer Nature B.V; Springer Verlag
• Subjects: Acetyltransferase; Animals; Astrocytes; Biomedical and Life Sciences; Biomedicine; Brain; Brain - metabolism; Cell Biology; Choline O-acetyltransferase; Dopamine receptors; Fluorescence in situ hybridization; Glutamate decarboxylase; Glutamatergic transmission; Glutamic acid; Hedgehog protein; Hedgehog Proteins - genetics; Hedgehog Proteins - metabolism; Hypothalamus; In Situ Hybridization, Fluorescence; Life Sciences; Mammals; Mice; Microglial cells; Neurology; Neurons - metabolism; Neurosciences; Nitric-oxide synthase; Olig2 protein; Original Article; Phenotypes; RNA, Messenger - metabolism; Signal transduction; Sox10 protein; Transcription factors; Tyrosine 3-monooxygenase; γ-Aminobutyric acid; Multiple sclerosis; Shh; Smoothened; RNAscope; Neurodegenerative diseases; Patched
• ISSN: 1863-2661; 1863-2653; 1863-2661; 0340-2061
• DOI: 10.1007/s00429-023-02756-2

In the adult mammalian brain, astrocytes are proposed to be the major Sonic Hedgehog (Shh)-responsive cells. However, the sources of the Shh molecule mediating activation of the pathway are still poorly characterized. The present work investigates the distribution and phenotype of cells expressing Shh mRNA in the adult mouse brain. Using single-molecule fluorescent in situ hybridization (smfISH), we report much broader expression of Shh transcripts in almost all brain regions than originally reported. We identify Shh mRNA in HuC/D + neuronal populations, including GABAergic (glutamic acid decarboxylase 67, Gad67), cholinergic (choline acetyltransferase, ChAT), dopaminergic (tyrosine hydroxylase, TH), nitrergic (neuronal nitric oxide synthase, nNOS), and in a small population of oligodendroglial cells expressing Sox10 and Olig2 mRNA transcription factors. Further analysis of Shh mRNA in cerebral cortical and hypothalamic neurons suggests that Shh is also expressed by glutamatergic neurons. Interestingly, we did not observe substantial Desert Hedgehog and Indian Hedgehog mRNA signals, nor Shh signals in S100β + astrocytes and Iba1 + microglial cells. Collectively, the present work provides the most robust central map of Shh-expressing cells to date and underscores the importance of nitrergic neurons in regulating Shh availability to brain cells. Thus, our study provides a framework for future experiments aimed at better understanding of the functions of Shh signaling in the brain in normal and pathological states, and the characterization of novel regulatory mechanisms of the signaling pathway.