Generation of Pet1210-Cre Transgenic Mouse Line Reveals Non-Serotonergic Expression Domains of Pet1 Both in CNS and Periphery

Abstract

Neurons producing serotonin (5-hydroxytryptamine, 5-HT) constitute one of the most widely distributed neuronal networks in the mammalian central nervous system (CNS) and exhibit a profuse innervation throughout the CNS already at early stages of development. Serotonergic neuron specification is controlled by a combination of secreted molecules and transcription factors such as Shh, Fgf4/8, Nkx2.2, Lmx1b and Pet1. In the mouse, Pet1 mRNA expression appears between 10 and 11 days post coitum (dpc) in serotonergic post-mitotic precursors and persists in serotonergic neurons up to adulthood, where it promotes the expression of genes defining the mature serotonergic phenotype such as tryptophan hydroxylase 2 (Tph2) and serotonin transporter (SERT). Hence, the generation of genetic tools based on Pet1 specific expression represents a valuable approach to study the development and function of the serotonergic system. Here, we report the generation of a Pet1210-Cre transgenic mouse line in which the Cre recombinase is expressed under the control of a 210 kb fragment from the Pet1 genetic locus to ensure a reliable and faithful control of somatic recombination in Pet1 cell lineage. Besides Cre-mediated recombination accurately occurred in the serotonergic system as expected and according to previous studies, Pet1210-Cre transgenic mouse line allowed us to identify novel, so far uncharacterized, Pet1 expression domains. Indeed, we showed that in the raphe Pet1 is expressed also in a non-serotonergic neuronal population intermingled with Tph2-expressing cells and mostly localized in the B8 and B9 nuclei. Moreover, we detected Cre-mediated recombination also in the developing pancreas and in the ureteric bud derivatives of the kidney, where it reflected a specific Pet1 expression. Thus, Pet1210-Cre transgenic mouse line faithfully drives Cre-mediated recombination in all Pet1 expression domains representing a valuable tool to genetically manipulate serotonergic and non-serotonergic Pet1 cell lineages.

Cellular architecture and transmitter phenotypes of neurons of the mouse median raphe region

“…PET-1-independent and dependent serotonergic cells have been shown to project to different brain areas (Kiyasova et al 2011). Furthermore, non-serotonergic neurons were also found to be positive for PET-1 in several raphe nuclei (Pelosi et al 2014). …”

Vsx1 Transiently Defines an Early Intermediate V2 Interneuron Precursor Compartment in the Mouse Developing Spinal Cord

“…Fourteen micrometer cryostat sections were cut and double in situ hybridization (ISH) protocol was performed essentially as previously described with slight modifications (Beguin et al, 2013; Pelosi et al, 2014). Sections were simultaneously hybridized overnight at 65°C with a DIG-conjugated Foxn4 (NM_148935.2, nucleotides 78–1643 (Francius et al, 2015)) and a fluorescein-labeled Vsx1 (NM_054068.2, nucleotides 121–2728, provided by C. Cepko) riboprobe.…”

Divergent in vivo activity of non‐serotonergic and serotonergic VGluT3–neurones in the median raphe region

“…The currently available, MRR-related recombinase expressing mouse strains, including VGluT3-Cre (Tatti et al 2014), ePet-Cre (Scott et al 2005), Pet1 210 -Cre (Pelosi et al 2014), TpH2-Cre (Weber et al 2009(Weber et al , 2011 or SERT-Cre (Zhuang et al 2005) animals, cannot unequivocally differentiate the most prominent MRR subpopulations. VGluT3 is also expressed by 5-HT+ cells, but, as demonstrated in the present study, they are fundamentally different from the VGluT3+/5-HTgroup, rendering presently known serotonergic and glutamatergic markers unusable for tagging only the 5-HT-glutamatergic population.…”