The genetic material, or genome, first and foremost operates at the level of specific cells, and practically any animal tissue or embryo consists of thousands of highly diverse cells. How and why the same genome leads to such enormous diversity of cell types and functions are unanswered questions of modern biology. Yet, cell-specific approaches to link cause and effect are virtually absent for a majority of animal groups. This interdisciplinary project addresses these bottlenecks experimentally by developing novel genomic approaches and chemical labeling tools for genome-wide characterization of expression, classification, and mapping of thousands of individual cells in parallel. This information is used to (i) achieve a nearly complete census of cell types within a given organism, focusing on animal models critical to understanding mechanisms of learning and memory, such as Aplysia, and regeneration, such as Pleurobrachia, and (ii) generate nanoscale probes that selectively mark specific cells for genome editing, regardless of any advance knowledge about the cells' molecular diversity. Several communities are benefiting from the proposed research, including comparative neurobiology, development, biological oceanography, and the emerging field of synthetic biology. The project also affords cross-disciplinary training opportunities for trainees from the undergraduate to postdoctoral level and educational outreach activities in marine and comparative biology aimed at a diverse K-12 student body.
The grand challenge in our understanding of the genomes-to-phenomes relationships is our general inability to manipulate genome operation at the level of specific individual cells at any given location and at any given time. These obstacles are more dramatic for most invertebrates, when researchers study development or neuronal functions with little information about the cellular composition of target organs. Here, microfluidics for massive parallel single-cell capture and sequencing are integrated with novel cell selection technologies, such as aptamer-based-Cell-SELEX, for quantitative gene expression analyses and imaging of individual cells in intact tissues. Aplysia (and, once single-cell tools are validated, Pleurobrachia and/or related ctenophore species) are used to achieve nearly complete genome-wide classification of the majority of cell types in their neural systems and effector organs. The read-out(s) to measure/control gene expression in identified neurons are: scRNA-seq data with both normalized and absolute quantification of expression levels for target genes, and q-RT-PCR. Controls are neurons in which target genes are not active or silenced. First, unique resources for a diversity of cell adhesion molecules and other surface macromolecular structures critical to design and characterize cell-specific probes are generated. Then, using tools of chemical evolution, a high-throughput system to manufacture cell-specific aptamer-/molecular beacon-based fluorescent probes at a large scale is tested. Finally, hybrid nanoscale probes (e.g. made by coupling cell-specific fluorescent markers with nucleic acid analogues) are tested for their ability to self-deliver molecular constructs into target cells without direct injection, electroporation, or the need to make transgenic animals. This project is co-funded by the Chemistry of Life Processes program in the Division of Chemistry.
