Long ago, the cell was described as the most basic individual unit of all life on Earth. Cells are found in plants, animals, and bacteria. From beating hearts to neurons firing in the brain, cells make up tissues that perform critical functions in our bodies. Most evidence suggests that no two cells are exactly alike, especially when assessing their functionality at the molecular and biochemical levels. Almost everything we know about cells, however, is inferred from research studying cell populations or groups. So, imagine finally being able to fully teeze apart the difference between a tumor cell and a normal cell in a tumor sample. Examining cells individually will lead to the understanding of how they differ and ultimately shows us how they work together. Insights into the burgeoning single-cell field has recently been the focus of a special issue in Nature.
How are humans actually put together? This is a question that has oft been thought to hold the key to who we are—the holy grail. Tracking the development of billions of individual human or animal cells has proven mostly impossible with only a microscope.The Nature issue points out that developmental biology will strongly benefit from single-cell research improvements and newly developed technologies will allow for multiple ways of approaching this complex problem. One way of looking at it is from a genetic standpoint, where naturally occurring mutations or even artificially induced mutations via CRISPR technology, can be tracked into a "cell lineage tree". Like cells themselves, no two lineage trees will likely be the same, and gaining this knowledge will have wide ranging implications in understanding disease and aging, as this tree can be highly dynamic throughout a lifetime.
Another story highlighted in the issue that truly pushes the envelope and showcases what can come out of this type of research is Aviv Regev’s work on spearheading the International Human Cell Atlas. The project is ambitious: to classify and map the over 37 trillion cells in the human body. Although it’s a large undertaking, sequencing the RNA of all the cells in a human body and using these gene expression profiles to classify them into different types will lead to mapping their organization to form a functional unit.
As you can imagine, single-cell profiling will encounter many challenges. The single-cell Nature issue brings to the forefront how the amount of data gathered, itself, can be mind-boggling. But this can be surmounted with the coalescence of multiple disciplines teaming together to analyze this lowly life-form. Single-cell analysis is calling on everyone from computer programmers to developmental biologists to pool resources to get answers to previously unanswerable questions and to make sense of the large body of data that will inevitably be collected.
The single-cell is finally seeing its time in the light. We think it’s about time.