NATURE: 21. 3. 2013

NATURE: Differential stem- and progenitor-cell trafficking by prostaglandin E₂

"To maintain lifelong production of blood cells, haematopoietic stem cells (HSCs) are tightly regulated by inherent programs and extrinsic regulatory signals received from their microenvironmental niche. Long-term repopulating HSCs reside in several, perhaps overlapping, niches that produce regulatory molecules and signals necessary for homeostasis and for increased output after stress or injury^{1, 2, 3, 4, 5}. Despite considerable advances in the specific cellular or molecular mechanisms governing HSC–niche interactions, little is known about the regulatory function in the intact mammalian haematopoietic niche. (...)"

http://www.nature.com/nature/journal/v495/n7441/full/nature11929.html

NATURE: Evolutionary genomics: Detecting selection

"Advances in population genetics and genome sequencing have made it possible to identify anonymous fragments of DNA that have undergone selection. This yields some evolutionary answers, and a panoply of puzzles."

http://www.nature.com/nature/journal/v495/n7441/full/495325a.html

NATURE: Stem cells: Painkillers caught in blood-cell trafficking

"Haematopoietic stem and progenitor cells move from the bone marrow into the circulation to replenish normal blood-cell levels. Inhibiting a prostaglandin-mediated signalling pathway may promote this process."

http://www.nature.com/nature/journal/v495/n7441/full/nature12085.html

NATURE: Blood test for cancer DNA

The DNA that is shed into the bloodstream from dying cancer cells might one day be used to monitor the disease. Carlos Caldas at the Cancer Research UK Cambridge Institute and his colleagues identified genetic markers to track disease in 30 women being treated for advanced breast cancer."

http://www.nature.com/nature/journal/v495/n7441/full/495284c.html

SCIENCE: A Localized Wnt Signal Orients Asymmetric Stem Cell Division in Vitro

"Developmental signals such as Wnts are often presented to cells in an oriented manner. To examine the consequences of local Wnt signaling, we immobilized Wnt proteins on beads and introduced them to embryonic stem cells in culture. At the single-cell level, the Wnt-bead induced asymmetric distribution of Wnt–β-catenin signaling components, oriented the plane of mitotic division, and directed asymmetric inheritance of centrosomes. Before cytokinesis was completed, the Wnt-proximal daughter cell expressed high levels of nuclear β-catenin and pluripotency genes, whereas the distal daughter cell acquired hallmarks of differentiation. We suggest that a spatially restricted Wnt signal induces an oriented cell division that generates distinct cell fates at predictable positions relative to the Wnt source."

http://www.sciencemag.org/content/339/6126/1445.abstract

SCIENCE: Dual Origin of the Epithelium of the Mammalian Middle Ear

"The air-filled cavity and ossicles of the mammalian middle ear conduct sound to the cochlea. Using transgenic mice, we show that the mammalian middle ear develops through cavitation of a neural crest mass. These cells, which previously underwent an epithelial-to-mesenchymal transformation upon leaving the neural tube, undergo a mesenchymal-to-epithelial transformation to form a lining continuous with the endodermally derived auditory tube. The epithelium derived from endodermal cells, which surrounds the auditory tube and eardrum, develops cilia, whereas the neural crest–derived epithelium does not. Thus, the cilia critical to clearing pathogenic infections from the middle ear are distributed according to developmental derivations. A different process of cavitation appears evident in birds and reptiles, indicating that this dual epithelium may be unique to mammals."

http://www.sciencemag.org/content/339/6126/1453.abstract