A basic assumption about the normal nervous system is that its neurons possess identical genomes. Here we present direct evidence for genomic variability, manifested as chromosomal aneuploidy, among developing and mature neurons. Analysis of mouse embryonic cerebral cortical neuroblasts in situ detected lagging chromosomes during mitosis, suggesting the normal generation of aneuploidy in these somatic cells. Spectral karyotype analysis identified Ϸ33% of neuroblasts as aneuploid. Most cells lacked one chromosome, whereas others showed hyperploidy, monosomy, and͞or trisomy. The prevalence of aneuploidy was reduced by culturing cortical explants in medium containing fibroblast growth factor 2. Interphase fluorescence in situ hybridization on embryonic cortical cells supported the rate of aneuploidy observed by spectral karyotyping and detected aneuploidy in adult neurons. Our results demonstrate that genomes of developing and adult neurons can be different at the level of whole chromosomes.

Together, these data demonstrate that human brain cells (both neurons and non-neuronal cells) can be aneuploid and that the resulting genetic mosaicism is a normal feature of the human CNS.

Five cognate G protein-coupled receptors (S1P 1-5 ) have been shown to mediate various cellular effects of sphingosine 1-phosphate (S1P). Here we report the generation of mice null for S1P 2 and for both S1P 2 and S1P 3 . S1P 2 -null mice were viable and fertile and developed normally. The litter sizes from S1P 2 S1P 3 double-null crosses were remarkably reduced compared with controls, and double-null pups often did not survive through infancy, although double-null survivors lacked any obvious phenotype. Mouse embryonic fibroblasts (MEFs) were examined for the effects of receptor deletions on S1P signaling pathways. Wild-type MEFs were responsive to S1P in activation of Rho and phospholipase C (PLC), intracellular calcium mobilization, and inhibition of forskolin-activated adenylyl cyclase. S1P 2 -null MEFs showed a significant decrease in Rho activation, but no effect on PLC activation, calcium mobilization, or adenylyl cyclase inhibition. Double-null MEFs displayed a complete loss of Rho activation and a significant decrease in PLC activation and calcium mobilization, with no effect on adenylyl cyclase inhibition. These data extend our previous findings on S1P 3 -null mice and indicate preferential coupling of the S1P 2 and S1P 3 receptors to Rho and PLC/Ca 2؉ pathways, respectively. Although either receptor subtype supports embryonic development, deletion of both produces marked perinatal lethality, demonstrating an essential role for combined S1P signaling by these receptors.Sphingosine 1-phosphate (S1P) 1 is a bioactive lysophospholipid that elicits diverse physiological effects on most types of cells and tissues. Several lines of evidence from a wealth of in vitro studies revealed that these effects are induced by S1P activation of any of five cognate G protein-coupled receptors: S1P 1 (LP B1 /EDG-1), S1P 2 (LP B2 /H218/AGR16/EDG-5), S1P 3 (LP B3 /EDG-3), S1P 4 (LP C1 /EDG-6), and S1P 5 (LP B4 /NRG-1/ EDG-8) (reviewed in Refs. 1-7). In part reflecting a lack of receptor subtype-specific agonists/antagonists and the universal expression of multiple S1P receptor genes in many single cell types, the in vivo roles of each receptor were unclear until the recent use of genetic approaches in mice (reviewed in Ref. 44). Liu et al. (8) reported that S1P 1 -null mice are lethal. S1P 1 -null mice exhibit embryonic hemorrhage and incomplete vascular maturation, which lead to intrauterine death. S1P-induced cell migration and activation of the small GTPase Rac are severely defective in S1P 1 -null mouse embryonic fibroblasts (MEFs), suggesting that the loss of S1P cellular signaling is relevant to those phenotypes found in S1P 1 -null mice (8). We observed that S1P 3 -null mice are without marked phenotypic differences compared with controls (9). However, S1P-induced phospholipase C (PLC) activation is severely defective in S1P 3 -null MEFs (9). In this study, we generated S1P 2 -null mice. S1P 2 -null mice were viable and apparently normal, as were S1P 3 -null mice. However, S1P-induced Rho activation was impaired. B...

Rationale Caffeine is widely consumed in foods and beverages and is also used for a variety of medical purposes. Despite its widespread use, relatively little is understood regarding how genetics affects consumption, acute response, or the long-term effects of caffeine. Objective This paper reviews the literature on the genetics of caffeine from the following: (1) twin studies comparing heritability of consumption and of caffeine-related traits, including withdrawal symptoms, caffeine-induced insomnia, and anxiety, (2) association studies linking genetic polymorphisms of metabolic enzymes and target receptors to variations in caffeine response, and (3) case-control and prospective studies examining relationship between polymorphisms associated with variations in caffeine response to risks of Parkinson’s and cardiovascular diseases in habitual caffeine consumers. Results Twin studies find the heritability of caffeine-related traits to range between 0.36 and 0.58. Analysis of poly-substance use shows that predisposition to caffeine use is highly specific to caffeine itself and shares little common disposition to use of other substances. Genome association studies link variations in adenosine and dopamine receptors to caffeine-induced anxiety and sleep disturbances. Polymorphism in the metabolic enzyme cytochrome P-450 is associated with risk of myocardial infarction in caffeine users. Conclusion Modeling based on twin studies reveals that genetics plays a role in individual variability in caffeine consumption and in the direct effects of caffeine. Both pharmacodynamic and pharmacokinetic polymorphisms have been linked to variation in response to caffeine. These studies may help guide future research in the role of genetics in modulating the acute and chronic effects of caffeine.

The existence of aneuploid cells within the mammalian brain has suggested the influence of genetic mosaicism on normal neural circuitry. However, aneuploid cells might instead be glia, nonneural, or dying cells, which are irrelevant to direct neuronal signaling. Combining retrograde labeling with FISH for chromosome-specific loci, distantly labeled aneuploid neurons were observed in expected anatomical projection areas. Coincident labeling for immediate early gene expression indicated that these aneuploid neurons were functionally active. These results demonstrate that functioning neurons with aneuploid genomes form genetically mosaic neural circuitries as part of the normal organization of the mammalian brain.cerebral cortex ͉ chromosome paint ͉ mosacism A neuploidy, the loss and͞or gain of chromosomes producing numerical deviation from haploid multiples, has documented effects on cellular physiology, particularly in pathophysiological settings such as cancer and Down's syndrome (1, 2). Whereas even the quantitative change of a single-gene product can produce major changes in cellular signaling (3), the effects associated with loss or gain of Ϸ1,000 gene copies on an average chromosome should have even more pronounced changes on a cell's physiology. Approximately 33% of neural progenitor cells display genetic variability, manifested as chromosomal aneuploidy that encompasses both loss and gain of chromosomes (4-7). In the mature brain, aneuploid cells that express neuronal markers have been observed (4, 6). However, an unanswered question is whether these neurons represent functional rather than dying cells, with death being a common fate for aneuploid cells in other systems (8,9). Toward determining their relevance for adult brain function, we examined aneuploid cells in the normal brain for anatomical connectivity and functional activity. MethodsProcedures involving live animals were conducted at the University of California at San Diego (UCSD), approved by the Animal Subjects Committee at UCSD, and conform to National Institutes of Health guidelines and public law.Activation Paradigm for Immediate Early Gene (IEG) Induction. All animals were transferred from the home cage to a clean cage 1 h before killing. To maximize the activation of cortical cells, two mice received additional stimulation that included exposure to a novel male (10) and to various odors (11). Specifically, a novel male was placed in the same cage as the subject male, and the males were allowed to interact for 1-3 min. After the removal of the novel male, subject males were then exposed sequentially to peppermint and banana odors for 15 min each while remaining in the clean cage. Animals were killed 1 h after the beginning of the exposure paradigm, perfused with 0.9% saline, followed by 4% paraformaldehyde in 0.1 M PBS (pH 7.4), and brain tissue was processed as described below.Retrograde Tracer Injections. Ten male 8-week-old mice from three different strains (BalbC͞CR, Swiss Webster, and c129SvJ) received tracer injections. Mice were ane...