5.3 Single cell proteomics research

Scientists often use transcriptome research to understand the proteomics in cells. At present, the relationship between mRNA and protein abundance in cells is not very clear, so a technique that can directly evaluate the relationship between transcriptome and functional proteome is urgently needed. The complex chemical properties of proteins make it difficult for us to quantify proteins as accurately as RNA, but as the sensitivity of mass spectrometry becomes higher and higher, the volatize technology of proteins becomes more and more mature, we also see hope for single-cell protein research. In addition, due to the continuous development of antibodies such as high-affinity antibodies, nanobodies, single-chain variable fragment, and ligands (aptamer), these high-affinity technologies can also provide more sensitive technical means to make single-cell proteomics research a reality as soon as possible.

In addition to sequencing, we also need to conduct other single-cell studies, such as single-cell DNA structure studies and single-cell epigenome research. Chromosomal conformation, DNA methylation, open chromatin structure, and small-molecule metabolome are all moving towards the single-cell level. No matter what kind of cells, real-time, multi-variable and multi-dimensional detection of living cells in the tissue is the ideal detection method we need most, because only in this way can we obtain the most realistic and systematic cell status and data. For RNA molecules, this may mean the detection of single transcript molecules in living cells. This test can not only discover which molecules are involved in each biological process, but also help us have a deeper understanding and understanding of each biological process.

In addition to detection and analysis, we also need to perform some interference experiments at the single cell level in order to have a dynamic understanding of the function of the cell. For example, the use of RNA molecules to regulate the function of cells can even play a therapeutic role. Transfection of cells with quantitatively diluted RNA is the first reported transcriptome induced phenotype remodeling (TIPeR). After the whole transcriptome, or part of the RNA molecules are transfected into the cell, the phenotype of the cell can be changed towards the intended goal. The goal of TIPeR technology is to use cells' "RNA memory" to achieve specific cell functions, which is a functional genomics technology that can regulate cell functions and phenotypes. Transcriptome analysis and quantitative regulation technology allow us to manipulate the phenotype and function of cells, which has very important significance for basic scientific research and clinical treatment.

5.4 Prospects of single cell biology research

At the single cell level, all diseases are different in pathology. Single-cell research can help us better understand why some cells are sick, while others are normal; it can also tell us why some cells are very sensitive to drugs, but other cells are "indifferent" to drugs. Scientists have discovered many cell or tissue characteristics most affected by the disease, as well as cell or tissue characteristics related to the disease's onset or severity. Finding out these specific molecular states related to disease helps us discover and make good use of drug targets, but whether these targets can be found depends on how well we can recognize "sick" cells.

For example, we all know that dopaminergic neurons will gradually lose the ability to synthesize and secrete dopamine after patients have Parkinson's disease, and these cells will eventually die as the disease progresses. Each receptor, ion channel protein or transporter protein found on these neuronal cells can be the target of drug action, which can delay the progression of the disease or improve the patient's condition. The drugs currently used to treat Parkinson's disease mainly target the four proteins on these neuronal cells, which are the Dopa transporter, the muscarinic receptor M1, and the monoamine oxidase (MAO) and adenosine A2A receptor. Previous histological studies have found targets for drugs, but many of them are not on target cells. The unique sensitivity and specificity of single-cell research tells us that there are at least 300 to 400 different drug action genes on a variety of cells. If the same is true for Parkinson's disease patients, we can choose at least 30 to 40 drug targets for targeted treatment during the long period of disease progression.

In addition to the role of translational research, single-cell research can fundamentally change our view of how multicellular tissues (organs) work, allowing us to raise many new scientific questions. For example, among the hundreds of billions of cells in the human body, how many different cells are there? What does somatic DNA variation mean for cell identification and cell diversity? If somatic mutations are very common, do they occur randomly or are they part of a planned mutation in the genome? Is the phenotype of the cell determined by its own genome, or is it the result of the dynamic influence of the surrounding environment? In other words, is DNA the executor of the execution program or is it just a carrier of information?

Microbiome sequencing data has consistently shown that single-celled microorganisms are part of a multicellular host. On the other hand, DNA and RNA sequencing studies on individual cells in a multicellular tissue also found that these cells are extremely heterogeneous. This shows that the cells in multicellular organisms are not as obvious as the tissues in each organism. The function of these tissues is determined by the ecosystem of these cells, and the interaction between these cells determines the entire phenotype of the tissue, this situation is very similar to the microbiome. If this is a common guideline for all living things, then determining the diversity of single cells and the ecosystem between the cells will be the inevitable way for us to understand every living thing.

Author's Bio: 

CD Genomics