Biomedical subjects

Sascha Rutz

Publications and source records attributed to Sascha Rutz.

4 recordsLinked to original sources

PubMed2005

Design of siRNAs producing unstructured guide-RNAs results in improved RNA interference efficiency.

In RNA interference (RNAi), guide RNAs direct RNA-induced silencing complexes (RISC) to their mRNA targets, thus enabling the cleavage that leads to gene silencing. We describe a strong inverse correlation between the degree of guide-RNA secondary structure formation and gene silencing by small interfering (si)RNA. Unstructured guide strands mediate the strongest silencing whereas structures with base-paired ends are inactive. Thus, the availability of terminal nucleotides within guide structures determines the strength of silencing. A to G and C to U base exchanges, which involve wobble base-pairing with the target but preserve complementarity, turned inactive into active guide structures, thereby expanding the space of functional siRNAs. Previously observed base degenerations among mature micro (mi)RNAs together with the data presented here suggest a crucial role of the guide-RNA structures in miRNA action. The analysis of the effect of the secondary structures of guide-RNA sequences on RNAi efficiency provides a basis for better understanding RNA silencing pathways and improving the design of siRNAs.

Algorithms↗

PubMed2005

Notch ligands Delta-like1, Delta-like4 and Jagged1 differentially regulate activation of peripheral T helper cells.

The Notch pathway is involved in cell differentiation processes in various organs and at several developmental stages. The importance of Notch for early T lymphocyte development is well established. Recently, Notch has been implicated in directing naive T helper cell differentiation towards the Th1, Th2 or regulatory T cell lineages. However, the molecular events underlying these processes are poorly understood. We show that the Notch ligands Delta-like1, Delta-like4 and Jagged1 differentially affect early T cell activation and proliferation following T cell receptor cross-linking. Delta-like1 and Jagged1 induce a dose-dependent inhibition of early activation markers CD69 and CD25, as well as inhibition of proliferation after anti-CD3 stimulation of purified CD4+ T cells. Similarly, the rapid activation of transcription factors NF-AT, AP-1 and NF-kappaB is suppressed. In contrast, triggering of Notch by Delta-like4 enhances T cell activation and proliferation. The observed effects are dependent on simultaneous cross-linking of TCR and Notch but independent of gamma-secretase-mediated cleavage of Notch. These data suggest direct interference between Notch and early TCR signal transduction events, independent of the classical Notch pathway via release of the Notch intracellular domain. A Notch-mediated alteration of TCR signaling strength may contribute to the recently described modulation of naïve T cell differentiation by Notch ligands.

Adaptor Proteins, Signal Transducing↗

PubMed2004

Towards in vivo application of RNA interference - new toys, old problems.

RNA interference (RNAi) is the sequence-specific degradation of mRNA by short double-stranded RNA molecules. The technology, introduced only 5 years ago, has stimulated many fantasies regarding the future of functional gene analysis and gene therapy. Given its ease of application, its high efficiency and remarkable specificity, RNAi holds great promise for broad in vitro and in vivo application in all areas of biomedicine. Despite its potential, the major obstacle to the use of RNAi (as for all previous gene silencing approaches) is the need for efficient and sustained delivery of small interfering RNA into primary mammalian cells, and specific targeting of particular cell types in vivo.

Animals↗

PubMed2004

Interleukin-2 is essential for CD4+CD25+ regulatory T cell function.

Constitutive expression of CD25, the IL-2 receptor alpha-chain, defines a distinct population of CD4+ T cells (Treg) with suppressive activity in vitro and in vivo. IL-2 has been implicated in the generation and maintenance of Treg, however, a functional contribution of the IL-2 receptor during suppression is thus far unknown. We show that IL-2 is required for Treg function in vitro, since suppression is completely abrogated by selective blocking of the IL-2 receptor on Treg during co-culture with responder T cells. We demonstrate that Treg, which do not produce IL-2, compete for IL-2 secreted by responder T cells. In accordance with the idea of competition being part of the suppressive mechanism, in vitro neutralization of IL-2 mimics all effects of Treg. Conversely, recombinant IL-2 abrogates inhibition of IL-2 production in responder T cells, the hallmark of Treg suppression. Finally, activation in the presence of IL-2 primes Treg to produce IL-10 upon secondary stimulation, indicating that IL-2 uptake is also required to induce additional suppressive factors that might be more relevant for suppression in vivo. We propose the parakrine uptake of soluble mediators as a flexible mechanism to adapt Treg activity to the strength of the responder T cell reaction.

Animals↗