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This Week in Nature: Feb 25, 2010

In Nature this week, Research out of Stanford identifies three factors that, when expressed in combination, rapidly and efficiently convert mouse embryonic and postnatal fibroblasts into functional neurons in vitro. Asc11, Brn2, and Myt11 have shown to induce neuronal cells that express multiple neuron-specific proteins and form functional synapses. The authors write that their finding could have implications for studies of neural development and disease modeling as well as regenerative medicine.

In a research article in Nature this week, another Stanford team discusses the requirement of AID-dependent DNA demethylation in nuclear reprogramming towards pluripotency in human somatic cells. The team generated interspecies (mouse and human) heterokaryons and observed that reprogramming was initiated rapidly ― in only one day ― and efficiently (70 percent) without cell division and DNA replication. Using a siRNA-mediated knockdown method, the team showed that AID is required for promoter demethylation and induction for Oct4 and Nanog expression.

Researchers at EMBL in Heidelberg, Germany, and Cold Spring Harbor Laboratory report their exploration of the link between ancient miRNAs and body plan evolution. Foteini Christodoulou et al. posit that any specific localization shared between protostomes and deuterosomes should reflect miRNA specificity as such of their last common ancestor. In their investigation, Christodoulou and colleagues indicate that the oldest known animal miRNA is miR-100. “These findings reveal that microRNA evolution and the establishment of tissue identities were closely coupled in bilaterian evolution. Also, they outline a minimum set of cell types and tissues that existed in the protostome-deuterostome ancestor,” the authors write.

Also in Nature this week, an international research team indentifies that transcription factor Tbx3 improves the germ-line competency of iPS cells. The team performed a genome-wide chromatin immunoprecipitation sequencing analysis of Tbx3-binding sites in embryonic stem cells which suggested that it regulates reprogramming factors and shares many common downstream regulatory targets with Oct4, Sox2, Nanog, and Smad1. They also found that iPS cells generated with OSK and Tbx3 showed improved germ-cell contribution to the gonads and germ-line transmission frequency. “This study underscores the intrinsic qualitative differences between iPS cells generated by different methods, and highlights the need to rigorously characterize iPS cells beyond in vitro studies,” they write.