Converting human skin cells to neurons: a new tool to study and treat brain disorders?

Recent publications in Cell Stem Cell (Son et?al., 2011; Ambasudhan et?al., 2011), PNAS (Pfisterer et?al., 2011), and Nature (Caiazzo et?al., 2011; Pang et?al., 2011; Yoo et?al., 2011) report that functional neurons can be directly generated from human fibroblast cells without going through the pluripotent state.     

How to remake a fibroblast into a neural stem cell

In this issue of Cell Stem Cell and in a recent issue of PNAS, Thier et?al. (2012), Han et?al. (2012), and Lujan et?al. (2012) report the derivation of multipotent neural stem/progenitor cells from cultured mouse fibroblasts using distinct reprograming approaches.     

Tolerance induction by allogeneic hematopoietic stem cells

In this issue of Cell Stem Cell, Zheng et?al. (2011) report that HSCs expressing PD-L1 display enhanced engraftment in irradiated allogeneic recipients. Independently in Nature, Fujisaki et?al. (2011) observe allogeneic HSCs persisting in proximity to regulatory T?cells in nonirradiated recipients, further connecting HSCs and immune tolerance.     

Finally, Polyubiquitinated PCNA Gets Recognized

Studies from Ciccia et?al. (2012) and Yuan et?al. (2012) in this issue of Molecular Cell, together with Weston et?al. (2012), reveal that the translocase ZRANB3/AH2 can recognize K63-linked polyubiquitinated PCNA and plays an important role in restarting stalled replication forks.     

Hijacking leucyl-tRNA synthetase for amino acid-dependent regulation of TORC1

TORC1 activity in all eukaryotes is dependent on amino acid availability. However, the mechanism through which TORC1 senses amino acids is still a mystery. In the current issues of Molecular Cell and Cell, Bonfils et?al. (2012) and Han et?al. (2012) implicate leucyl-tRNA synthetase in this evolving story.     

Breaking the cell cycle of HSCs by p57 and friends

The cell cycle regulators involved in maintaining the quiescence, and thereby the self-renewal capacity, of somatic stem cells have long been elusive. Two new Cell Stem Cell articles in this issue (Matsumoto et?al., 2011; Zou et?al., 2011) now show that the CDK inhibitor p57 is a crucial brake for cycling HSCs, and links self-renewal activity to cell cycle quiescence.     

S1P(1) Bridges Mechanotransduction and Angiogenesis during Vascular Development

Mechanisms of stabilization of the vascular plexus and the role of mechanotransduction in this process are?not well understood. In this issue of Developmental Cell, Jung et?al. (2012) and Gaengel et?al. (2012) describe the ligand-sensitive and mechanosensitive functions of an important vascular G protein-coupled receptor, S1P(1).     

The special delivery of a tail-anchored protein: why it pays to use a dedicated courier

The membrane-spanning C-terminal regions in tail-anchored proteins must be recognized and delivered posttranslationally to the endoplasmic reticulum or mitochondrial membrane. A paper in this issue of Molecular Cell (Wang et?al., 2010) and another recent report (Mariappan et?al., 2010) delineate early steps in this pathway.     

Cullin RING Ligases: Glommed by Glomulin

Cullin ring ligases (CRLs) constitute the largest group of RING finger ubiquitin ligases. Two recent studies in?Molecular Cell describe glomulin as a CRL1 inhibitor that blocks interactions with its ubiquitin-conjugating enzyme (E2) (Duda et?al., 2012; Tron et?al., 2012). These findings and their significance are discussed.     

Moving right along: how PP1 helps clear the checkpoint

Spindle checkpoint silencing is crucial for cell-cycle progression, but mechanisms underlying this process remain mysterious. Two papers, one in this issue of Developmental Cell (Meadows et?al., 2011) and one in Current Biology (Rosenberg et?al., 2011), begin to show how phosphatase PP1-gamma connects chromosome-microtubule attachment with anaphase entry.     

New ways to make old walls: bacterial surprises

Two papers in this issue of Cell (Paradis-Bleau et?al., 2010 and Typas et?al., 2010) report that the lipoproteins LpoA and LpoB are required for the synthesis of cell walls in Escherichia coli. Attached to the bacterial outer membrane, these new cell wall components regulate penicillin-binding proteins located at the inner membrane.     

Unwinding to recombine

The MCM proteins are best known for their role in DNA replication, MCM2-7 forming the replicative helicase. Now, two reports in this issue of Molecular Cell, Nishimura et?al. (2012) and Lutzmann et?al. (2012) show the less well understood MCM8 and MCM9 to be crucial for effective homologous recombination.     

The powerstroke and camshaft of the RIG-I antiviral RNA detection machine

The innate immune sensor RIG-I responds to infection by binding to viral double-stranded RNA (dsRNA). In this issue of Cell, Kowalinski et?al. (2011) and Luo et?al. (2011) reveal the structure of RIG-I, and in combination with functional analyses, they show how RIG-I recognizes viral RNA to initiate signaling and a type I interferon response.     

A dedicated Wnt secretion factor

The Wnt family of signaling proteins mediates cell-cell communication during development. In this issue of Cell, B?nziger et al. (2006) and Bartscherer et al. (2006) identify Wntless/Evi, a multipass transmembrane protein in the secretory pathway of Wnt-producing cells that promotes Wnt secretion.     

Distinct and Dynamic Requirements for mTOR Signaling in Hematopoiesis and Leukemogenesis

Signaling involving PI3K and AKT regulates cell growth, partly through the mTOR kinase complexes 1 and 2. In this issue of Cell Stem Cell, Kalaitzidis et?al. and Magee et?al. reveal unique requirements for mTORC1 and mTORC2 signaling during blood development and leukemogenesis induced by loss of PTEN.     

Targeting β-catenin in CML: leukemia stem cells beware!

In this issue of Cell Stem Cell, Heidel et?al. (2012) use genetic and pharmacological approaches to reveal that Wnt/β-catenin signaling is required for leukemic stem cell (LSC) maintenance in chronic myeloid leukemia. They demonstrate that β-catenin inactivation targets imanitib-resistant LSCs in?vivo.     

Oxidative-reductionist approaches to stem and progenitor cell function

In this issue of Cell Stem Cell, Daquinag et?al. (2011) take a lesson from the oncology field to search for stromal progenitor cells within adipose tissue. Their use of phage display biopanning in?vivo identified an isoform of the extracellular matrix protein decorin as a receptor for the adipokine resistin.     

An epigenetic Tet a Tet with pluripotency

DNA and chromatin-modifying enzymes establish an ESC/iPSC-specific epigenomic landscape that is linked to a network of pluripotency genes and influences differentiation potential. In this issue of Cell Stem Cell, Koh?et?al. (2011) highlight Tet1 and Tet2 as key players in this network of coordinated genetic and epigenetic control.