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Brain-wide genetic mapping identifies the indusium griseum as a prenatal target of pharmacologically unrelated psychostimulants

Fuzik J, Rehman S, Girach F, Miklosi AG, Korchynska S, Arque G, Romanov RA, Hanics J, Wagner L, Meletis K, Yanagawa Y, Kovacs GG, Alpár A, Hökfelt TGM, Harkany T (2019) Proc Natl Acad Sci U S A.  2019 Dec.  pii: 201904006. doi: 10.1073/pnas.1904006116. [Epub ahead of print] 

Web URL: Read this and related abstracts on PubMed here

Abstract:

Psychostimulant use is an ever-increasing socioeconomic burden, including a dramatic rise during pregnancy. Nevertheless, brain-wide effects of psychostimulant exposure are incompletely understood.

Here, we performed Fos-CreER
T2-based activity mapping, correlated for pregnant mouse dams and their fetuses with amphetamine, nicotine, and caffeine applied acutely during midgestation. While light-sheet microscopy-assisted intact tissue imaging revealed drug- and age-specific neuronal activation, the indusium griseum (IG) appeared indiscriminately affected. By using GAD67gfp/+ mice we subdivided the IG into a dorsolateral domain populated by γ-aminobutyric acidergic interneurons and a ventromedial segment containing glutamatergic neurons, many showing drug-induced activation and sequentially expressing Pou3f3/Brn1 and secretagogin (Scgn) during differentiation. We then combined Patch-seq and circuit mapping to show that the ventromedial IG is a quasi-continuum of glutamatergic neurons (IG-Vglut1 +) reminiscent of dentate granule cells in both rodents and humans, whose dendrites emanate perpendicularly toward while their axons course parallel with the superior longitudinal fissure. IG-Vglut1 + neurons receive VGLUT1+ and VGLUT2+ excitatory afferents that topologically segregate along their somatodendritic axis.

In turn, their efferents terminate in the olfactory bulb, thus being integral to a multisynaptic circuit that could feed information antiparallel to the olfactory-cortical pathway. In IG-
Vglut1 + neurons, prenatal psychostimulant exposure delayed the onset of Scgn expression. Genetic ablation of Scgn was then found to sensitize adult mice toward methamphetamine-induced epilepsy.

Overall, our study 
identifies brain-wide targets of the most common psychostimulants, among which Scgn +/Vglut1 + neurons of the IG link limbic and olfactory circuits.

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