Review series

Stem cell biology is the study of how tissues and organs are formed and maintained throughout life. Recent efforts seek to translate scientific insights to the clinic. Such efforts are gaining momentum, but it is important to separate myth and hype from reality. The articles in this Review series aim to do just that, providing a balanced perspective on what the field has achieved, where it is headed, and what challenges must be overcome if effective stem cell–based therapies are to be developed.

Research into the pathogenesis, prevention, and control of infectious and parasitic diseases remains a global priority as these scourges continue to be a substantial cause of mortality and morbidity. As highlighted in this Review Series, genome-wide approaches have provided great insight into a range of human pathogens, leading to greater understanding of the human diseases that they cause. Challenges that must be overcome in order to maximize our ability to use this wealth of genomic information are also discussed.

Intermediate filaments (IFs) are one of the three major fibrillar cytoplasmic elements that make up the cytoskeleton. Cytoskeletal IFs in distinct cell types are formed from different members of a large family of proteins, the IF protein family, which also includes proteins that are present in the nucleus, where they are the main component of the nucleoskeleton. As discussed in this Review series, roles have been revealed for IFs in more than 80 human tissue-specific diseases.

Epithelial-mesenchymal transition (EMT) describes the series of events by which adherent, polarized epithelial cells convert to a mesenchymal cell phenotype, which includes an ability to both migrate and invade the extracellular matrix. As discussed in the articles in this Review series, EMT is now a recognized mechanism for dispersing cells in embryos, forming fibroblasts/mesenchymal cells in injured tissues, and initiating invasive and metastic behavior in epithelial cancer cells.

Mental disorders such as schizophrenia, bipolar illness, depression, and autism are the number one source of medical disability for people 15–44 years of age in the U.S. and Canada. In the past, these disorders have been considered psychological conflicts or chemical imbalances, but, as highlighted in this Review series, recent research indicates they are brain disorders, developmental disorders, and complex genetic disorders.

Cytokines are small protein mediators involved in essentially all biological processes. As such, abnormalities in cytokines, their receptors, and the signaling pathways that they initiate are involved in a wide variety of diseases. This Review Series discusses the important role of cytokines and their receptors in just a few of these diseases, specifically three chronic inflammatory disease areas and two forms of cancer, highlighting their potential as therapeutic targets.

Although advances in science and technology have resulted in substantial improvements in the health of individuals in the developed world, similar progress has not been observed for those living in the developing world. This Review Series focuses on the health conditions that affect people living in the developing world, and it highlights some of the areas that require attention if these conditions are either to be brought under control or eradicated.

When the homeostasis of a physiological system is markedly perturbed it is said to be stressed. It is hoped that understanding the response of physiological systems to stress stimuli, both physiologic and pathologic, will lead to the development of approaches to reduce the limitations these stimuli place on individuals. In this context, this Review Series focuses on the molecular response of several physiological systems to various stress stimuli.

Since the discovery in 1998 that gene expression could be silenced by RNA interference (RNAi), RNAi has become a routine tool for investigating the function of individual genes and gene products in the laboratory. This Review Series highlights some of the challenges that remain to be overcome if the medicinal promise of post-transcriptional gene silencing with short-interfering RNA and other molecules capable of inducing RNAi is to be fulfilled.

In 1960, Peter C. Nowell described an unusual small chromosome present in leukocytes from patients with chronic myelogenous leukemia that was thereafter designated the Philadelphia chromosome. This Review series includes contributions from individuals who performed critical experiments in the wake of the description of the Philadelphia chromosome, reflecting the nearly 50 years of work inspired by Nowell’s initial finding.