The human body is a very complex biological machine, composed of a vast number of cells. The most current research suggests that the number of cells in the human body is around 30 trillion—or 30,000,000,000,000 in standard form—which can be further divided into about 200 different cell types. When you consider that each of these cells has its own structure and function, the degree of complexity in the human body is nothing short of astounding.
In their efforts to explore the structure, function, and genomic qualities of all these different cells, scientists typically study large samples at a time. The resulting research gives an overview of the qualities of the entire cell population—thousands or millions of cells—instead of the qualities of a single cell. Sometimes, cell population knowledge is preferable, such as in the study of variability within the population. Other times, however, the study of a single cell has the potential to lead to great discoveries that could benefit us all.
Why Study Single Cells?
When isolated from the rest of the cell population, the study of a single cell can reveal a great deal about its characteristics and could identify the origins of any problems within the cell. A chief example of this is cancer, which begins with DNA damage or mutations within a single cell and then begins to grow abnormally, affecting other cells and eventually forms a tumor. Isolating research to develop an in-depth knowledge of this single cell and its eventual issues could lead to a greater understanding of how cancer progresses—and how to stop it.
Similarly, the study of the DNA and RNA at the heart of the human body’s vast network of complications and diversity can be isolated to a single cell. By noting the differences in the DNA programming from one cell type to another, researchers may be able to gain insight into the complex DNA changes that give rise to the cell diversity necessary for us to function. With approximately 3 billion base pairs in each cell, it’s easy to see why scrutinizing a single cell at a time could be beneficial.
The process of isolating single cells and studying their genetic material has given rise to a new field of research known as single-cell genomics, which aims to examine the DNA and RNA within a cell, instead of studying the human genome as a whole or as part of a cell population. In technical terms, this is a significant departure from extracting DNA from millions of genetically similar cells and using it to prepare a sample for study.
Instead, single-cell genomics employs single-cell sequencing. After isolating the desired cell via cell sorting and extracting its DNA, researchers must produce multiple copies of the DNA (amplify it) to study it effectively. In some cases, researchers may amplify the entire cell genome, while in others, it may be more beneficial to amplify only a specific area of interest. After amplification, researchers use high-throughput DNA sequencing methods to determine the sequence of base pairs contained within that cell.
Implications of Single-Cell Genomics
As single-cell genomics continues to grow and expand, researchers hope to make significant strides in identifying the genetic origins of the various types of cancer and learn more about slowing or halting their growth. Similarly, researchers discovered that other types of cells once thought to be similar or identical to one another are susceptible to mutation as well. The DNA of neurons, for example, can mutate, and the changes could contribute to brain disorders like Parkinson’s, Alzheimer’s, epilepsy, even autism.
Much more research and expansion of the field of single-cell genomics is needed before direct links are clear. However, technological advances in the arenas of cell sorting, DNA extraction, DNA amplification, and more have accelerated single-cell genomics at a rate never thought possible. Overall, the future looks positive for those experiencing the effects of cancer and other potentially DNA-linked disorders.
https://www.jax.org/news-and-insights/2015/december/single-cell-genomics# (reference only)