All life forms are assembled around a basic unit, the cell. Multicellular organisms have organized these unites into tissues and ultimately into more complex structures such as the human body. Human life begins with the fertilization of an oocyte resulting in a single cell that contains all the information to develop into a human, information that is stored in its DNA. Reading the genetic code and translating the information into proteins, the main cellular building blocks occur through a process called gene expression. Defects in the proper execution of gene expression programs can have severe consequences, causing developmental problems or serious diseases such as cancer. For instance, a tumor can be formed simply because a gene activation program is incorrectly executed within a single cell.
Thus, to understand why such defects can occur and to be able to correct or prevent them, we have to understand how gene activation is achieved within a single cell. Yet paradoxically, to date most of what we understand about gene control has been achieved by studying average behaviors of cells, not the individuals from which a tissue develops or a rogue cell that madly divides to form a tumor. We have developed unique and powerful methods to study gene regulation in single cells and at the single molecule level. These methods allow us to directly study how individual cells change their gene activation programs and will allow us to study why mutations in certain proteins lead to disease. These studies will therefore lead to a better understanding of the general rules governing the expression of genes in complex systems and enabling us to decipher the mechanisms underlying complex diseases, enabling the development of tools for diagnosis, prevention or treatment.