We know that we are made up of cells. In fact, according to science, we are actually made up of 30 trillion cells and that is not even counting the microbiome that each one of us carries. Even though we are mainly made up of red blood cells, there are actually 200 different types of cells in our bodies. If researchers were to, say, understand how we grow from one cell type to another, they would have to trace the lineage of the cell through fate mapping experiments. This method was actually developed backed in the late 19th century and it mainly involves taking large pools of cells that are derived from mature tissues. The cells would then be inferred by using different-colored dyes or they may even be transplanted isotopically by labeling the cells inside animal subjects.
There are various methods of using cell-lineage tracing and I will discuss the different types in this article.
Mingfu Wu, Associate Professor of the Department of Molecular and Cellular Physiology at Albany Medical College in New York made use of Brainbow– which is a transgenic technique that was originally used as a means to map individual neurons in the brain. This method was used to help label cells using gene cassettes that will code for up to four uniquely expressed fluorescent proteins. This was extensively used by Development Biologists because progenitor cells will start to assume a different color after Cre Recombination and will continue to maintain its luster as they start to divide. Trabeculae are multiple thin sheets that are found in heart muscle cells that span across the inner surface of the organ’s ventricles. It helps boost nutrient and gas exchange during early development. Wu states that without them, it would be impossible for us to survive for long.
Professor Jay Shendure of the Department of Genome Sciences at the University of Washington, in collaboration with Alexander Scheier’s lab at Harvard University, has made a technique known as GESTALT, which is an acronym that stands for Genome Editing of Synthetic Target Arrays and Lineage Tracing.
Basically, this approach would make use of CRISPR-Cas9 to help divide the cells and track them as they start to accumulate different mutations in each subsequent creation of cells. The starting group’s cells are placed with a temporary barcode that is about 300 base pairs in length. After the experiments, the researchers would then amplify the barcodes so that they can read both the RNA or DNA, thereby helping to reconstruct the cell lineages using computational data.
A certain tag that is attached to the barcode does act like a molecular identified. This is used to help account for potential changes or biases that are introduced during a polymerase-induced chain reaction.
Pre-Hematopoietic Stem Cells
Fuchou Tang is an Assistant Professor at Peking University and his study involved isolating hematopoietic stem cells to showcase their transcriptome signatures long before they mature into human embryonic stem cells.
The study was so hard to pull off in that it required specialists to work alongside him because isolating single cells is so hard to do. Their research involved isolating individual cells. To test for their purity, Tang’s team would culture those cells in Petri dishes for a couple of days and with the use of cell markers, it would help them identify which is which. The resulting HSCs would be transplanted into mice and if it forms blood cell lineages, then the method is a success.