jerry yang, science, biology, animal cloningby Alan Trounson

Leading light in animal cloning

Jerry Yang, who died on 5 February in Boston, Massachusetts, made exceptional contributions to research on animal biotechnology and cloning, and he was a prominent figure in the scientific dialogue between the United States and China. He was only 49 when he died, finally succumbing to cancer of the salivary gland. Losing battles, however, was not Yang's way of life.

He was born in 1959, in China, and barely survived the famine of 1959–1960. His parents were poor pig farmers in the tiny village of Dongcun, about 500 kilometres south of Beijing, but in the late 1970s the award of a place at Beijing Agricultural College set Yang on the road to a wider world. A scholarship to Cornell University in New York followed, where he took a master's degree and completed his PhD in reproductive physiology.

by Mick Aulakh

Adult cardiac fibroblasts tell neighbouring myocytes to expand; embryonic fibroblasts say proliferate

Though cardiac muscle cells proliferate in embryos, they unfortunately lose this function as the heart matures. Adult cardiomyocytes tend to grow through hypertrophy (increased cell size) rather than hyperplasia (increased cell number), even though the latter process is often more desirable.

Publishing in Developmental Cell, researchers led by Deepak Srivastava at the Gladstone Institute of Cardiovascular Disease in San Francisco, California, have now identified the key factors and cell types responsible for cardiomyocyte proliferation and have helped explain the differences between the adult and embryonic behaviour of these cells1.

science. biology, fetal by Monya Baker

The protein Runx1 matters in most progenitors, but just for a while

A single haematopoietic stem cell can re-form an animal's entire blood system, but how these cells form in the embryo is a much-studied mystery. Now researchers at the University of Pennsylvania in Philadelphia piece together when and where an important gene in this process functions.

Haematopoietic stem (HS) cells are found at several sites in the early mouse conceptus (that is, the foetus and its extra-embryonic tissues). The transcription factor Runx1 is expressed at each of them. Runx1 is known to be necessary for HS cells to form in the vascular areas — the early aorta, yolk sac, placenta, umbilical vessels and vitelline arteries of the early digestive tract — but it's less clear which cells produce HSCs. Do blood cells come from the endothelial lining of blood vessels or from other progenitors?

by Monya Baker

Transient expression of a single gene has lasting effects on others

Despite the bad publicity provided by One Flew Over the Cuckoo's Nest, electroconvulsive treatments can be effective for treating depression, and the procedure is known to cause adult mice to grow new neurons in their hippocampus. Now, researchers led by Hongjun Song at Johns Hopkins Medical School have found a mechanism through which this happens. A stimulus, in this case electrical activity, temporarily activates a gene whose protein product modifies DNA in such a way to affect the long-term expression of other genes.

by Monya Baker

Wnt signalling stimulates the beginnings of gastrulation

Left to their own devices, cultured pluripotent stem cells clump together. A hotchpotch of differentiated cells forms within these so-called 'embryoid bodies', and in fact, the formation of embryoid bodies is a preliminary assay of good quality in embryonic stem (ES) cells and induced pluripotent stem (iPS) cells. Researchers led by Roel Nusse at Stanford School of Medicine in California have now observed something surprising in these much studied structures: they spontaneously begin a process called gastrulation, the cell movements that occur in mammalian embryos after implantation and which result in the formation of the three germ layers of the animal body.

by Monya Baker

A new screening technique identifies molecules that control the cell cycle

Short stretches of RNA molecules known as microRNAs (miRNAs) coordinate gene expression. Although their importance as gene regulators is now accepted, it can be hard to figure out the functions of particular miRNAs. An individual miRNA molecule can interact with multiple gene transcripts, and multiple miRNAs often serve similar functions and so mask each others' effects.

Using a new screening technique, Robert Blelloch and colleagues at the University of California, San Francisco, have identified a collection of miRNAs that allow embryonic stem (ES) cells to divide rapidly1. The team had previously engineered a line of mouse ES cells that cannot process miRNA because they lack a crucial gene called Dgcr8. Unlike normal ES cells, these knockout ES cells do not proliferate rapidly. By introducing commercially available miRNA mimics, however, the researchers were able to get the cells to start dividing more quickly. After screening nearly 300 mouse miRNAs, the researchers found 14 that greatly improved proliferation of the Dgcr8-knockout ES cells but had no effect on wild-type ES cells. The researchers then concentrated their analysis on five of the miRNAs that are also highly expressed in human ES cells.

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