During gestation there is a high demand for the essential nutrient choline. Adult rats supplemented with choline during embryonic days (E) 11-17 have improved memory performance and do not exhibit age-related memory decline, whereas prenatally choline-deficient animals have memory deficits. Choline, via betaine, provides methyl groups for the production of S-adenosylmethionine, a substrate of DNA methyltransferases (DNMTs). We describe an apparently adaptive epigenomic response to varied gestational choline supply in rat fetal liver and brain. S-Adenosylmethionine levels increased in both organs of E17 fetuses whose mothers consumed a choline-supplemented diet. Surprisingly, global DNA methylation increased in choline-deficient animals, and this was accompanied by overexpression of Dnmt1 mRNA. Previous studies showed that the prenatal choline supply affects the expression of multiple genes, including insulin-like growth factor 2 (Igf2), whose expression is regulated in a DNA methylation-dependent manner. The differentially methylated region 2 of Igf2 was hypermethylated in the liver of E17 choline-deficient fetuses, and this as well as Igf2 mRNA levels correlated with the expression of Dnmt1 and with hypomethylation of a regulatory CpG within the Dnmt1 locus. Moreover, mRNA expression of brain and liver Dnmt3a and methyl CpG-binding domain 2 (Mbd2) protein as well as cerebral Dnmt3l was inversely correlated to the intake of choline. Thus, choline deficiency modulates fetal DNA methylation machinery in a complex fashion that includes hypomethylation of the regulatory CpGs within the Dnmt1 gene, leading to its overexpression and the resultant increased global and gene-specific (e.g. Igf2) DNA methylation. These epigenomic responses to gestational choline supply may initiate the long term developmental changes observed in rats exposed to varied choline intake in utero.An adequate supply of essential nutrients involved in the metabolism of methyl groups, including folic acid, vitamin B 12 , and choline, is central for normal development of the fetus. This is perhaps best exemplified by the discovery that the dietary supply of folic acid, a vitamin that acts as a coenzyme in one-carbon transfer pathways, during the periconceptual period is critical in prevention of neural tube defects (1). Studies in animal models (2-5) as well as recent epidemiological investigations in humans (6) indicate that choline intake during gestation is particularly important for the normal development and function of the central nervous system. In a frequently used experimental model that employs offspring of pregnant rats or mice consuming diets of varying choline content during the 7-day period of the second half of gestation (embryonic days E11-17), prenatal choline deficiency causes deficits in certain memory tasks (7), whereas prenatal choline supplementation leads to enhanced memory and attention and prevents agerelated memory decline (7-13). These behavioral changes are accompanied by electrophysiological, neuroanatomical, and neuro...

Bone morphogenetic proteins (BMPs) have multiple functions in the developing nervous system. A member of this family, BMP-9, was found to be highly expressed in the embryonic mouse septum and spinal cord, indicating a possible role in regulating the cholinergic phenotype. In cultured neurons, BMP-9 directly induced the expression of the cholinergic gene locus encoding choline acetyltransferase and the vesicular acetylcholine transporter and up-regulated acetylcholine synthesis. The effect was reversed upon withdrawal of BMP-9. Intracerebroventricular injection of BMP-9 increased acetylcholine levels in vivo. Although certain other BMPs also up-regulated the cholinergic phenotype in vitro, they were less effective than BMP-9. These data indicate that BMP-9 is a differentiating factor for cholinergic central nervous system neurons.

Background: The amyloid precursor protein (APP) is transported via the secretory pathway to the cell surface, where it may be cleaved within its ectodomain by α-secretase, or internalized within clathrin-coated vesicles. An alternative proteolytic pathway occurs within the endocytic compartment, where the sequential action of β-and γ-secretases generates the amyloid β protein (Aβ). In this study, we investigated the effects of modulators of endocytosis on APP processing.

Choline acetyltransferase (ChAT), the enzyme that synthesizes the neurotransmitter acetylcholine (ACh), is thought to be present in kinetic excess in cholinergic neurons. The rate-limiting factor in ACh production is the provision of choline to ChAT. Cholinergic neurons are relatively unique in their expression of the choline transporter 1 (CHT1), which exhibits high-affinity for choline and catalyzes its uptake from the extracellular space to the neuron. Multiple lines of evidence indicate that the activity of CHT1 is a key determinant of choline supply for ACh synthesis. We examined the interaction of ChAT and ChT activity using mice heterozygous for a null mutation in the Chat gene (Chatϩ/Ϫ). In these mice, brain ChAT activity was reduced by 40 -50% relative to the wild type, but brain ACh levels as well as ACh content and depolarization-evoked ACh release in hippocampal slices were normal. However, the amount of choline taken up by CHT1 and ACh synthesized de novo from choline transported by CHT1 in hippocampal slices, as well as levels of CHT1 mRNA in the septum and CHT1 protein in several regions of the CNS, were 50 -100% higher in Chatϩ/Ϫ than in Chatϩ/ϩ mice. Thus, haploinsufficiency of ChAT leads to an increased expression of CHT1. Increased ChT activity may compensate for the reduced ChAT activity in Chatϩ/Ϫ mice, contributing to the maintenance of apparently normal cholinergic function as reflected by normal performance of these mice in several behavioral assays.

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 (...