Volume 17, No 1 , 2016

The executive branch formally announced its biotechnology policy on June 26, 1986, in the form of the Coordinated Framework for Regulation of Biotechnology (OSTP 1986), as reviewed previously and described in more detail in this article. The three lead agencies with responsibility for implementation of the policy were the US Department of Agriculture (USDA), the Department of Health and Human Services (DHHS), and the Environmental Protection Agency (EPA).

The cornea on the front surface of the eye is our window to the world, hence maintenance of corneal tissue transparency is essential for vision. The integrity and functionality of the outermost corneal layer, the epithelium, plays a key role in refraction of light on to the retina at the back of the eye. Like other epithelia, the epithelium of the cornea is maintained by stem cells.

The kidneys play a critical homeostatic role in the regulation of body fluid composition and excretion of waste products. Here I review our understanding of how the three different vertebrate kidney types (pronephros, mesonephros, and metanephros) arise during mouse development with a more comprehensive focus on the molecular regulation of metanephros formation.

A little over 50 years ago, Sydney Brenner had the foresight to develop the nematode (round worm) Caenorhabditis elegans as a genetic model for understanding questions of developmental biology and neurobiology. Over time, research on C. elegans has expanded to explore a wealth of diverse areas in modern biology including studies of the basic functions and interactions of eukaryotic cells, host-parasite interactions, and evolution. C. elegans has also become an important organism in which to study processes that go awry in human diseases.

Although C. elegans is primarily touted for its facile genetics, there has been a burgeoning interest in studying cell biological processes in this organism.

This article discusses the maintenance of C. elegans in the laboratory. Topics include the acquisition of worm strains from the Caenorhabditis Genetics Center (CGC), methods of culture and transfer, decontamination of stocks, synchronizing and staging cultures, and procedures for freezing worms for long-term storage and for recovering them from the frozen state.

Genome editing is used to make targeted modifications to the genome of eukaryotic cells. There are many potential applications of genome editing in human pluripotent stem cells (hPSCs) including the generation of knockout and reporter cell lines. This protocol describes a system for efficient genome editing in hPSCs using engineered transcription activator-like effector nucleases (TALENs) or clustered regularly interspaced short palindromic repeat (CRISPR) technology.

Prolonged culture of pluripotent and multipotent stem cells exposes the cells to strong selection pressures, often resulting in genomic alterations. Any genetic manipulation of the cells may further jeopardize their genomic stability. Genomic aberrations affect the differentiation capacity of stem cells, their stem cell identity and their tumorigenicity, and should thus be routinely evaluated for their proper use in basic research and in clinical trials.

The directed differentiation of human embryonic stem cells (hESCs) or human induced pluripotent stem cells (hiPSCs) into hepatocytes could facilitate a rational study of the molecular mechanisms underlying human liver development as well as provide a renewable source of exogenous hepatocytes for drug toxicity testing and cell-based therapeutics. Moreover, if hepatocytes were produced from hiPSCs originating from patients with inborn errors of hepatic metabolism, such cells could be used for modeling liver disease.

The pluripotency of embryonic stem (ES) cells is the result of a highly dynamic equilibrium that is controlled by a complex network of transcription factors that confer unique transcriptional properties to ES cells. Regulation of gene expression appears to correlate with the presence of dual chromatin marks called bivalent domains at the promoters of poised developmental genes. These marks keep differentiation genes silenced but poised and ready to be activated or permanently repressed during differentiation.