Bone morphogenetic protein 9 induces the transcriptome of basal forebrain cholinergic neurons

Abstract

Basal forebrain cholinergic neurons (BFCN) participate in processes of learning, memory, and attention. Little is known about the genes expressed by BFCN and the extracellular signals that control their expression. Previous studies showed that bone morphogenetic protein (BMP) 9 induces and maintains the cholinergic phenotype of embryonic BFCN. We measured gene expression patterns in septal cultures of embryonic day 14 mice and rats grown in the presence or absence of BMP9 by using species-specific microarrays and validated the RNA expression data of selected genes by immunoblot and immunocytochemistry analysis of their protein products. BMP9 enhanced the expression of multiple genes in a time-dependent and, in most cases, reversible manner. The set of BMP9-responsive genes was concordant between mouse and rat and included genes encoding cell-cycle͞growth control proteins, transcription factors, signal transduction molecules, extracellular matrix, and adhesion molecules, enzymes, transporters, and chaperonins. BMP9 induced the p75 neurotrophin receptor (NGFR), a marker of BFCN, and Cntf and Serpinf1, two trophic factors for cholinergic neurons, suggesting that BMP9 creates a trophic environment for BFCN. To determine whether the genes induced by BMP9 in culture were constituents of the BFCN transcriptome, we purified BFCN from embryonic day 18 mouse septum by using fluorescence-activated cell sorting of NGFR ؉ cells and profiled mRNA expression of these and NGFR ؊ cells. Approximately 30% of genes induced by BMP9 in vitro were overexpressed in purified BFCN, indicating that they belong to the BFCN transcriptome in situ and suggesting that BMP signaling contributes to maturation of BFCN in vivo.nerve growth factor receptor ͉ neuronal development ͉ septum ͉ microarray ͉ fluorescence-activated cell sorting B one morphogenetic proteins (BMPs) play critical roles in the development of the nervous system, and there is growing evidence that BMPs regulate the expression of neurotransmitter phenotype, including the cholinergic phenotype (1-4) of basal forebrain cholinergic neurons (BFCN) that project to the neocortex and hippocampus and are important in the processes of attention, learning, and memory (5). Previous studies identified multiple BMP-regulated target genes in a variety of cells, including nervous tissue. However, although BMP target genes have been characterized in the specification of catecholaminergic and serotonergic neurons (6, 7), little is known about BMP target genes implicated in BFCN determination. BFCN are defined by their neuroanatomical location and the neurotransmitter that they synthesize and release, i.e., acetylcholine. The latter process requires a concerted expression of three genes, encoding choline acetyltransferase (Chat), the vesicular acetylcholine transporter (Vacht), and the choline transporter 1 (Cht1). Several additional features of these cells include expression of acetylcholinesterase, the neurotrophin receptors NGFR and TRKA, the expression of certain neurotransmitter receptors (...

BMP9 ameliorates amyloidosis and the cholinergic defect in a mouse model of Alzheimer’s disease

“…These data confirm our previous studies showing that BMP9 not only directly induces the cholinergic phenotype, but also may generate a trophic environment for cholinergic neurons by promoting the synthesis of NGF and its receptors (3,5,29). The BMP9-induced increase in NGF levels is of particular interest because NGF is a prototypic trophic factor for septal cholinergic neurons (51) whose utility as a therapeutic agent for AD has been actively explored (18).…”

“…The actions of BMP9 on hippocampal CHAT levels are consistent with prior investigations showing the induction of the cholinergic phenotype by this protein in multiple in vitro systems (2,4,5,29) as well as in in vivo models (2, 3), such as axotomized septohippocampal cholinergic neurons (3). BMP9 was highly effective at increasing CHAT levels in the hippocampus of both WT/CHGFP and APP.PS1/CHGFP mice at 5 mo of age.…”

“…Application of BMP9 to basal forebrain cell cultures and into the cerebral ventricles of developing mouse embryos (2) and adult mice (3) significantly increases ACh production. Moreover, the idea that the BMP9-signaling pathway may be a master regulator of the BFCN phenotype is supported by evidence showing that BMP9 is sufficient to induce BFCN-like features in human embryonic stem cell-derived neural progenitor cells (4) and that, in rodent basal forebrain cell cultures, BMP9 induces the BFCN transcriptome (5). Recent studies indicate that intracerebroventricularly (i.c.v.…”

“…Recent studies indicate that ACVR2B binds BMP9 with highest affinity (48) and thus is the most likely type II receptor to mediate this interaction. Stimulation of these receptors in BFCN leads to the phosphorylation of SMAD1/5/8 proteins (29), i.e., activation of the canonical BMP-signaling pathway, and consequent changes in transcription of multiple genes, including stimulation of the expression of Chat (2) and several transcription factors (5). Indeed, we found that some actions of BMP9 in BFCN, e.g., stimulation of Ngf gene transcription, require the synthesis of an intermediate protein factor (possibly a transcriptional regulator) (29).…”

Bone Morphogenetic Protein 9 and 13 Induce C3H10T1/2 Cell Differentiation to Cardiomyocyte-Like Cells in Vitro

“…It is well known that BMPs, especially BMP2 and BMP4, play an essential role in the differentiation of stem cells into myocardial cells (42,43). BMP9 and BMP13 are part of the TGF-b superfamily and are shown to be extensively involved in the embryonic development and formation of vascular endothelial cells, bone cells, and the basal forebrain cholinergic neurons (2,4,25). However, it is not clear whether BMP9 and BMP13 have the capability of inducing cardiomyocyte differentiation of stem cells.…”