Possibilities for Using Pluripotent Stem Cells for Restoring Damaged Eye Retinal Pigment Epithelium.

The retinal pigment epithelium is a monolayer of pigmented, hexagonal cells connected by tight junctions. These cells compose part of the outer blood-retina barrier, protect the eye from excessive light, have important secretory functions, and support the function of photoreceptors, ensuring the coordination of a variety of regulatory mechanisms. It is the degeneration of the pigment epithelium that is the root cause of many retinal degenerative diseases. The search for reliable cell sources for the transplantation of retinal pigment epithelium is of extreme urgency. Pluripotent stem cells (embryonic stem or induced pluripotent) can be differentiated with high efficiency into the pigment epithelium of the retina, which opens up possibilities for cellular therapy in macular degeneration and can slow down the development of pathology and, perhaps, restore a patient's vision. Pioneering clinical trials on transplantation of retinal pigment epithelial cells differentiated from pluripotent stem cells in the United States and Japan confirmed the need for developing and optimizing such approaches to cell therapy. For effective use, pigment epithelial cells differentiated from pluripotent stem cells should have a set of functional properties characteristic of such cells in vivo. This review summarizes the current state of preclinical and clinical studies in the field of retinal pigment epithelial transplantation therapy. We also discuss different differentiation protocols based on data in the literature and our own data, and the problems holding back the widespread therapeutic application of retinal pigment epithelium differentiated from pluripotent stem cells.

Mapping the ribosomal protein S7 regulatory binding site on mRNA of the E. coli streptomycin operon.

In this work it is shown by deletion analysis that an intercistronic region (ICR) approximately 80 nucleotides in length is necessary for interaction with recombinant E. coli S7 protein (r6hEcoS7). A model is proposed for the interaction of S7 with two ICR sites-region of hairpin bifurcations and Shine-Dalgarno sequence of cistron S7. A de novo RNA binding site for heterologous S7 protein of Thermus thermophilus (r6hTthS7) was constructed by selection of a combinatorial RNA library based on E. coli ICR: it has only a single supposed protein recognition site in the region of bifurcation. The SERW technique was used for selection of two intercistronic RNA libraries in which five nucleotides of a double-stranded region, adjacent to the bifurcation, had the randomized sequence. One library contained an authentic AG (-82/-20) pair, while in the other this pair was replaced by AU. A serwamer capable of specific binding to r6hTthS7 was selected; it appeared to be the RNA68 mutant with eight nucleotide mutations. The serwamer binds to r6hTthS7 with the same affinity as homologous authentic ICR of str mRNA binds to r6hEcoS7; apparent dissociation constants are 89 +/- 43 and 50 +/- 24 nM, respectively.

Selection of random RNA fragments as method for searching for a site of regulation of translation of E. coli streptomycin mRNA by ribosomal protein S7.

In E. coli cells ribosomal small subunit biogenesis is regulated by RNA-protein interactions involving protein S7. S7 initiates the subunit assembly interacting with 16S rRNA. During shift-down of rRNA synthesis level, free S7 inhibits self-translation by interacting with 96 nucleotides long specific region of streptomycin (str) mRNA between cistrons S12 and S7 (intercistron). Many bacteria do not have the extended intercistron challenging development of specific approaches for searching putative mRNA regulatory regions, which are able to interact with proteins. The paper describes application of SERF approach (Selection of Random RNA Fragments) to reveal regulatory regions of str mRNA. Set of random DNA fragments has been generated from str operon by random hydrolysis and then transcribed into RNA; the fragments being able to bind protein S7 (serfamers) have been selected by iterative rounds. S7 binds to single serfamer, 109 nucleotide long (RNA109), derived from the intercistron. After multiple copying and selection, the intercistronic mutant (RNA109) has been isolated; it has enhanced affinity to S7. RNA109 binds to the protein better than authentic intercistronic str mRNA; apparent dissociation constants are 26 +/- 5 and 60 +/- 8 nM, respectively. Location of S7 binding site on the mRNA, as well as putative mode of regulation of coupled translation of S12 and S7 cistrons have been hypothesized.