How does the olfactory apparatus of vertebrates detect and discriminate thousands of odors? Our approach to elucidating the mechanisms of olfactory discrimination involves the characterization of odorant receptors and the neural pathways that they activate. We are also interested in the developmental mechanisms responsible for specifying odorant receptor expression in olfactory neurons and the pathfinding of these cells' axons to their appropriate targets. Finally, our lab is developing DNA microarray technologies to elucidate genome-wide patterns of gene expression in the nervous system.
The zebrafish olfactory system. The numerical and anatomical simplicity of the zebrafish olfactory system facilitates an analysis of the molecular and cellular basis of olfactory coding in a vertebrate species. In one line of investigation, we are defining the odorant-binding properties of cloned fish odorant receptors, as fish respond to water soluble cues that are more amenable as probes for biochemical analyses. The zebrafish also offers advantages for studying development; methods for the generation and screening of mutant zebrafish may permit genetic approaches for studying odorant receptor gene expression and olfactory neurogenesis. Genomic mapping of odorant receptor genes and reveals that, as in other vertebrate species, odorant receptor genes are clustered in the zebrafish genome. However, genes tightly linked within a cluster are not coordinately regulated, suggesting that the regulation of individual receptor genes require the interaction of specific trans-acting factors with proximal cis-regulatory sequences. We are pursuing a variety of approaches, including transgenic manipulations, to define the promoter sequences responsible for directing the developmentally-regulated expression of the odorant receptor genes.
Patterning in the olfactory bulb. Olfactory neurons expressing the same odorant receptor converge with great precision to a small number of glomeruli in the olfactory bulb. This suggests that spatial patterns of afferent innervation in the bulb are used to encode olfactory information. What are the mechanisms for specifying the pattern of olfactory neuron projections in the olfactory bulb? We are pursuing several complementary approaches to identify the molecules involved in olfactory axon pathfinding. Transgenic manipulations in the mouse and zebrafish are being used to assess the potential role of candidate genes in the formation of the olfactory sensory map. We are also utilizing DNA microarrays to search for molecules expressedin spatially-restricted patterns in the olfactory bulb; such molecules would be good candidates as guidance cues for ingrowing olfactory axons.
DNA microarrays. Recent advances, which include the sequencing of entire genomes of selected model systems and the ability to survey "genome-wide" patterns of gene expression, now allow the dissection of biological processes at unprecedented levels of detail. We have established in our laboratory the full capabilities for carrying out DNA microarray analysis of gene expression. These techniques allow the analysis of mRNA expression from tens of thousands of genes at a time. To date, we have created high-density cDNA microarrays from the mouse and the zebrafish. We are using these microarrays as tools to investigate patterns of developmentally-regulated and spatially-restricted patterns of gene expression in the vertebrate central nervous system.
Our research is focused on understanding the molecular mechanisms of cellular differentiation in the nervous system. To this end, we are developing and applying DNA microarray-based approaches to identify – on a genome-wide level – the genes and genetic programs that underlie the progression of cells from the undifferentiated stem cell to the mature cell state. The information gained from these studies will be used to interpret and guide future studies on the development of neuronal precursors and mature neurons from human embryonic stem cells. In addition, the expertise of the Functional Genomics Laboratory in DNA microarray approaches and statistical analysis of large-scale gene expression datasets will be made available to all investigators on campus studying human stem cell biology.
In the News
The National Institutes of Health today announced its first research grants through President Barack Obama’s BRAIN Initiative, including three awards to the University of California, Berkeley, totaling nearly $7.2 million over three years.
Three UC Berkeley scientists were among a gathering of the nation’s top scientists at the White House this morning (Tuesday, April 2) as President Barack Obama announced a major national initiative to develop new tools to create real-time traffic maps of the human brain.
Two UC Berkeley scientists, Jennifer Doudna and John Ngai, each will receive a $100,000 Grand Challenges Explorations grant from the Bill & Melinda Gates Foundation to explore innovative research that could impact global health.