Through countless studies, it’s clear that genes and environmental factors are important for determining cellular identity. Now, a research team at the University of Southern California  (USC) have found that timing is another critical factor in determining cell fate during organ development.

Developing human nephron, the filtering unit of the kidney. Image by Nils O. Lindstrom and Tracy Tran/McMahon Lab USC Stem Cell

In findings published in Development Cell, Dr. Andy McMahon’s group shows that development of the nephron, the filtering structure of the kidney, is acutely dependent on when cells arrive in that developmental region. Cells that arrive in the developing nephron early become part of the tubule, which is responsible for reabsorption of water and salt, whereas cells that arrive late become part of the glomerulus, the structure that is responsible for filtering blood.

The scientists verified that timing influenced cell identity with a combination of microscopy, which allowed them to follow particular cell types as they developed, and single-cell RNA sequencing, which allowed them to determine how gene expression changes in a population of cells.

In a press release, Dr. McMahon details the importance of these findings:

“By studying normal human nephron development, we’re gaining important information about how to replicate this intricate process in the laboratory. The hope is that laboratory-grown nephrons can be used to further study the process of development, screen potential therapies to treat disease, and eventually provide the building blocks to assemble functional kidneys for transplantation into patients.”

Understanding kidney development is crucial because approximately 30 million people suffer from chronic kidney disease and it is the ninth leading cause of death in the United States alone. Insights into the basics of kidney biology can provide important advances to develop novel therapeutics for this devastating condition.