Homocysteine induced alterations in gene expression in neural crest cells

The amino acid homocysteine increases in the serum when there is insufficient folic acid or vitamin B12, or with certain mutations in enzymes important in methionine metabolism. Elevated homocysteine is related to increased risk for cardiovascular and other diseases in adults and elevated maternal homocysteine increases the risk for certain congenital defects, especially those that result from abnormal development of the neural crest and neural tube. Experiments with the avian embryo model have shown that elevated homocysteine perturbs neural crest / neural tube migration in vitro and in vivo. While there have been numerous studies of homocysteine-induced changes in gene expression in adult cells, there is no previous report of a homocysteine-responsive transcriptome in the embryonic neural crest. We treated neural crest cells in vitro with exogenous homocysteine in a protocol that induces significant changes in neural crest cell migration. We used microarray analysis and expression profiling to identify 65 transcripts of genes of known function that were altered by homocysteine. The largest set of effected genes (19) included those with a role in cell migration and adhesion. Other major groups were genes involved in metabolism (13); DNA / RNA interaction (11); cell proliferation / apoptosis (10); and transporter / receptor (6). Although the genes identified in this experiment were consistent with prior observations of the effect of homocysteine upon neural crest cell function, none had been identified previously as response to homocysteine in adult cells. Keywords: homocysteine ● microarray ● expression profiling ● embryo ● neural crest Neural tube explants were obtained from stage 9+ chicken embryos to generate neural crest cell cultures. After 4 hours in culture the cells were exposed to either media or homocysteine for 6 hours. The cultures were then processed for gene expression using the affymetrics chicken chip. For these experiments 3 control (media exposed) arrays were compared to 3 homocysteine-treated (100uM final concnetration).