MiRNA activity directs stem cell commitment to a particular fate

Comment on: Mann M, et al. Proc Natl Acad Sci USA. 2010; 107:15804-9.     

Implications for matrix metalloproteinases as modulators of pediatric lung disease

Matrix metalloproteinases (MMPs) are a large family (>20) of cation-dependent proteinases believed to be important modulators of normal human lung development and potentially harmful mediators of lung damage. Little is known about MMP production and secretion by the lung during childhood or how alterations in MMP levels may be involved in lung damage. We examined endotracheal aspirates from children (<19 years) without lung disease for the presence of MMP activity. Only gelatinase activity was detectable, and inhibitor profiles suggest they represented one or more MMPs. Comparison of gelatinase activity, MMP expression, and MMP activity in children without pulmonary disease with children who required mechanical ventilation for respiratory failure show: 1) gelatinase activity was approximately five- to sixfold higher in respiratory failure; 2) MMP-7, MMP-8, and MMP-9 concentrations and MMP-8 and MMP-9 activities were markedly elevated in respiratory failure; and 3) MMP-7, MMP-8, and MMP-9 levels were significantly correlated in children with lung disease. These studies provide compelling evidence that specific MMPs are present in the diseased lung and may participate in the pathogenesis of pediatric respiratory failure.     

Immunochemical detection of the alpha-subunit of the G-protein, GZ, in membranes and cytosols of mammalian cells

An antiserum (AS 98) was raised against a synthetic peptide deduced from published cDNA sequences of the alpha-subunit of the putative G-protein, GZ (Fong et al. Proc. Natl. Acad. Sci. USA 85, 3066-3070, 1988; Matsuoka et al. Proc. Natl. Acad. Sci. USA 85, 5384-5388, 1988). In membrane and cytosol preparations of many but not all tested mammalian tissues, AS 98 predominantly recognized two proteins of 40 and 43 kDa Mr. Whereas high levels of a 40 kDa GZ alpha-subunit were found in rat liver membranes and in brain cytosol, AS 98 failed to detect the alpha-subunit of GZ in brain membranes.     

Probing the complexity of miRNA expression across hematopoiesis

Comment on: Petriv OI, et al. Proc Natl Acad Sci USA 2010; 107:15443-8.     

Inositol pyrophosphates in cell death and life

Comment on: Koldobskiy MA, et al. Proc Natl Acad Sci USA 2010; 107:20947-51.     

The role of eIF5A in protein synthesis

Comment on: Henderson A, et al. Proc Natl Acad Sci USA 2011; 108:6415-9.     

Mechanistic insights into the action of Bisphenol A on the germline using C. elegans

Feature on: Allard P, et al. Proc Natl Acad Sci USA 2010; 107:20405-10.     

Slowly cycling versus rapidly cycling intestinal stem cells: Distinct roles or redundancy

Comment on: Montgomery RK, et al. Proc Natl Acad Sci USA 2011; 108:179-84.     

You’d better catch that Wnt: Primitive hematopoiesis requires canonical Wnt signaling

Comment on: Tran HT, et al. Proc Natl Acad Sci USA 2010; 107:16160-5.     

AGTR1 as a therapeutic target in ER-positive and ERBB-negative breast cancer cases

Comment on: Rhodes DR, et al. Proc Natl Acad Sci USA 2009; 106:10284-9.     

Could TCTP contribute to Armin Braun's paradigm of tumor reversion in plants?

Comment on: Brioudes F, et al. Proc Natl Acad Sci USA 2010; 107:16384-9.     

Dynamics of the recovery from sRNA-mediated gene silencing

Comment on: Mitarai N, Benjamin JA, Krishna S, Semsey S, Csiszovszki Z, Massé E, et al. Dynamic features of gene expression control by small regulatory RNAs. Proc Natl Acad Sci USA 2009; 106:10655-9.     

MALT lymphoma meets stem cells

Comment on: Vicente-Dueñas C, et al. Proc Natl Acad Sci USA 2012; 109:10534-9.     

A generalized discrete model linking rippling pattern formation and individual cell reversal statistics in colonies of myxobacteria

Self-organization processes in multicellular aggregates of bacteria and amoebae offer fascinating insights into the evolution of cooperation and differentiation of cells. During myxobacterial development a variety of spatio-temporal patterns emerges such as counterpropagating waves of cell density that are known as rippling. Recently, several models have been introduced that qualitatively reproduce these patterns. All models include active motion and a collision-triggered reversal of individual bacteria. Here, we present a systematic study of a generalized discrete model that is based on similar assumptions as the continuous model by Igoshin et al (2001 Proc. Natl Acad. Sci. USA 98 14913). We find counterpropagating as well as unidirectional rippling waves in extended regions of the parameter space. If the interaction strength and the degree of cooperativity are large enough, rippling patterns appear even in the absence of a refractory period. We show for the first time that the experimentally observed double peak in the reversal statistics of bacteria in rippling colonies (Welch and Kaiser 2001 Proc. Natl Acad. Sci. USA 98 14907) can be reproduced in simulations of counterpropagating rippling waves which are dominant in experiments. In addition, the reversal statistics in the pre-rippling phase is correctly reproduced.     

Role for Geminin in sustaining the activity of hematopoietic stem cells

Ohno Y, et al. Proc Natl Acad Sci USA 2010; In press.     

Building a great wall around mitosis: Evolutionary conserved roles for the Greatwall/MASTL kinases in securing chromosome stability

Comment on: Voets E, et al. Cell Cycle 2010; 9:3591–3601 & Burgess A, et al. Proc Natl Acad Sci USA 2010; 107:12564–9.     

MicroRNA-dependent regulation of the microenvironment and the epithelial stromal cell interactions in the mouse mammary gland

Ohno Y, et al. Proc Natl Acad Sci USA 2010; In press.     

Engineering autoactivating forms of matrix metalloproteinase-9 and expression of the active enzyme in cultured cells and transgenic mouse brain

Matrix metalloproteinases (MMPs) are hypothesized to play an important role in the pathogenesis of several central nervous system disorders. Increased levels of expression of MMP-9 (gelatinase B) and MMP-2 (gelatinase A) have been observed in Alzheimer's disease, stroke, multiple sclerosis, and amyotrophic lateral sclerosis. This suggests an aberrant regulation of MMPs that could lead to inappropriate expression of MMP activity. To allow us to evaluate the effect of increased levels of active MMP-9 in the central nervous system, mutant forms of the enzyme were designed to autocatalytically remove the pro domain, yielding active enzyme. This was accomplished by modifying residues in the cysteine switch autoinhibitor region of the propeptide. Stable cell lines and transgenic mice that express G100L and D103N autoactive forms of human MMP-9 were developed to study the role of dysregulation of MMP-9 in disease.     

Transient RNA interference in hematopoietic progenitors with functional consequences

Short interfering (si) RNAs have now been shown to inhibit gene expression in several species, including mammals (Elbashir et al.: Nature 411:494-498, 2001; Fire et al.: Nature 391:806-811, 1998). RNA inhibition in primary cells such as stem cells would facilitate rapid gene discovery in a postgenome era. While retroviruses can deliver siRNA expression cassettes for stable expression (Barton and Medzhitov: Proc Natl Acad Sci USA 99:14943-14945, 2002; Paddison et al.: Proc Natl Acad Sci USA 99:1443-1448, 2002; Rubinson et al.: Nat Genet 33:401-406, 2003), an efficient method for direct transfer of siRNA to stem cells is still lacking. Here, we established electroporation to deliver siRNA to hematopoietic progenitors. On average, at least 80% of cells take up the RNA, and these display nearly 100% knockout of marker gene expression at both the RNA and protein level. Moreover, knockdown of the hematopoietic regulator, CD45, results in 3-fold more hematopoietic colonies in a progenitor assay. These results demonstrate that transient transfection of siRNA to primary cells can have substantial functional consequences. This technology may be applicable to a variety of primary cell types.