Notch-Rbpj signaling is required for the development of noradrenergic neurons in mouse locus coeruleus

Abstract

SummaryThe locus coeruleus (LC) is the main source of noradrenaline in the brain and is implicated in a broad spectrum of physiological and behavioral processes. However, genetic pathways controlling the development of noradrenergic neurons in the mammalian brain are largely unknown. We report here that Rbpj, a key nuclear effector in the Notch signaling pathway, plays an essential role in LC neuron development in the mouse. Conditional inactivation of Rbpj in the dorsal rhombomere (r) 1, where LC neurons are born, resulted in a dramatic increase in the number of Phox2a-and Phox2b-expressing early-differentiating LC neurons, and dopamine-b-hydroxylase-and tyrosine-hydroxylase-expressing late-differentiating LC neurons. In contrast, other neuronal populations derived from the dorsal r1 were either reduced or unchanged. In addition, a drastic upregulation of Ascl1, an essential factor for noradrenergic neurogenesis, was observed in dorsal r1 of conditional knockout mice. Through genomic sequence analysis and EMSA and ChIP assays, a conserved Rbpjbinding motif was identified within the Ascl1 promoter. A luciferase reporter assay revealed that Rbpj per se could induce Ascl1 transactivation but this effect was counteracted by its downstream-targeted gene Hes1. Moreover, our in vitro gene transfection and in ovo electroporation assays showed that Rbpj upregulated Ascl1 expression when Hes1 expression was knocked down, although it also exerted a repressive effect on Ascl1 expression in the presence of Hes1. Thus, our results provide the first evidence that Rbpj functions as a key modulator of LC neuron development by regulating Ascl1 expression directly, and indirectly through its target gene Hes1.

TSPAN5, ERICH3 and selective serotonin reuptake inhibitors in major depressive disorder: pharmacometabolomics-informed pharmacogenomics

“…57-60 The Notch intracellular domain is then transported to the nucleus where it binds to transcription factors on gene promoters, inducing changes in gene expression. 73, 74 A recent study reported that RBPJ-κ may play a role in the expression of DDC and MAOA , 61 and we showed that RBPJ-κ KD resulted in increased expression of TPH1/2 , DDC , and SLC6A4 in SK-N-BE(2) neuroblastoma cells ( Supplementary Figure 7 ). Obviously, future studies will be required to clarify the possible functional relationships among ADAM10, TSPAN5, Notch and RBPJ-κ.…”

“…61 Therefore, we knocked down RBPJ-κ in SK-N-BE(2) cells, and observed increased expression of TPH1, TPH2 , DDC , and SLC6A4 ( Supplementary Figure 7 ). This may be one mechanism by which TSPAN5, an integral membrane protein, may influence serotonin biosynthesis, as described in more detail in the Discussion .…”

Regulation of downstream neuronal genes by proneural transcription factors during initial neurogenesis in the vertebrate brain

“…Expression was first detected in the brain at E8.0 in the nmesV before neuronal differentiation [34, 56]. We wanted to determine if the relationship between Ascl1 and Notch signalling was similar to that already described in other central nervous system regions [47]. RBPj mutant mice have been commonly used to study the role of Notch inhibition [11, 36].…”

Parathyroid hormone inhibits Notch signaling in osteoblasts and osteocytes

“…In the present study, known limitations to the study of Rbpjk/DNA interactions by EMSA are documented. Namely, displaced CSL probes are not always visible in the presence of unlabeled competitors, and formation of an active transcriptional complex in the context of Dll1 exposure may lead to a shift of the nuclear protein bound to the CSL probe and attenuation of the signal [57, 60, 61]. Although the identity of the factors that prevent the association of Rbpjκ with DNA is not known, activation of MAPK in response to PTH may be involved in this process.…”