hTERT knockdown in human embryonic kidney cells using double-stranded RNA

Transduction of Human Fetal Liver Hematopoietic CD34+ Stem and Progenitor Cells into a Cell Line by Enhancing Telomerase Activity

Background: Human fetal liver hematopoietic stem cells have proven potential as therapeutics but lack extensive research due to their limited supply. Even in vitro expanded fetal liver hematopoietic stem cells enter senescence or lose their self-renewal capacity after a few days in culture. The present study aimed to obtain a homogeneous and persistent supply of hematopoietic stem cells from the fetal liver by establishing a cell line through immortalization of cells by enhancing telomerase activity. Materials and Methods: Human fetal liver hematopoietic CD34+ stem and progenitor cells were transformed and immortalized using retroviruses carrying the human telomerase (hTERT) gene. Following transduction, telomerase activity was assessed using the TRAP assay and telomere length was examined by Southern blotting in transduced cells. Their characterization was conducted using flowcytometry to analyze the CD34+ population of hematopoietic stem cells and their colony forming potential using colony forming unit (CFU) assay. Results: After transduction with hTERT, the life span of human fetal liver hematopoietic CD34+ stem and progenitor cells were extended to 80 population doublings, without any change in cell morphology or population doubling times. Constitutive hTERT expression enhanced the replicative capacity and prevented terminal differentiation of CD34+ fetal liver hematopoietic stem and progenitor cells (FLHSPCs). Moreover, hTERT-transduced stem cells maintained their telomere length and telomerase activity. Conclusion: By introducing telomerase activity into hematopoietic stem and progenitor cells, their lifespan can be extended while maintaining stemness. These modified cells hold promise for in vitro research focused on studying hematopoietic stem cells derived from fetal liver.

Therapeutic Targets in Telomerase and Telomere Biology of Cancers

Telomeres play an important role to conserve genomic integrity by protecting the ends of chromosomes in normal cells. Since, their progressive shortening during successive cell division which lead to chromosomal instability. Notably, telomere length is perpetuated by telomerase in large majority of cancers, thereby ensure indefinite cell proliferation-a hallmark of cancer-and this unique feature has provided telomerase as the preferred target for drug development in cancer therapeutics. Cancer cells have acquired the potential to have telomere length maintenance by telomerase activation- up-regulation of hTERT gene expression in tumor cells is synchronized by multiple genetic and epigenetic modification mechanisms viz hTERT structural variants, hTERT promoter mutation and epigenetic modifications through hTERT promoter methylation which have been implicated in various cancers initiation and progression. In view of these facts, strategies have been made to target the underlining molecular mechanisms involved in telomerase reactivation as well as of telomere structure with special reference to distortion of sheltrin proteins. This review is focussed on extensive understanding of telomere and telomerase biology. which will provide indispensable informations for enhancing the efficiency of rational anticancer drug design. However, there is also an urgent need for better understanding of cell signalling pathways for alternative lengthening of telomere which is present in telomerase negative cancer for therapeutic targets.

Exposure to dsRNA elicits RNA interference in Brachionus manjavacas (Rotifera)

RNA interference (RNAi) is a powerful technique for functional genomics, yet no studies have reported its successful application to zooplankton. Many zooplankton, particularly microscopic metazoans of phylum Rotifera, have unique life history traits for which genetic investigation has been limited. In this paper, we report the development of RNAi methods for rotifers, with the exogenous introduction of double-stranded RNA (dsRNA) through the use of a lipofection reagent. Transfection with dsRNA for heat shock protein 90, the membrane-associated progesterone receptor, and mitogen-activated protein kinase significantly increased the proportion of non-reproductive females. Additionally, a fluorescence-based lectin binding assay confirmed the significant suppression of four of six glycosylation enzymes that were targeted with dsRNA. Suppression of mRNA transcripts was confirmed with quantitative PCR. Development of RNAi for rotifers promises to enhance the ability for assessing genetic regulation of features critical to their life history and represents a key step toward functional genomics research in zooplankton.

Strategies targeting telomerase inhibition

Telomerase plays a pivotal role in cellular immortality and tumorigenesis. Its activity is normally not detectable in most somatic cells while it is reactivated in the vast majority of cancer cells. Therefore, inhibition of telomerase has been viewed as a promising anticancer approach due to its specificity for cancer cells. Studies so far have shown that telomerase inhibition can inhibit the proliferation of cancer cells or cause apoptosis while it has no effect on most normal cells. Strategies currently being applied to induce telomerase inhibition target virtually all of the major components of the ribonucleoprotein holoenzyme and related cell signal pathways that regulate its activity. These strategies include inhibition of telomerase through targeting at the telomerase reverse transcriptase (TERT) catalytic subunit, the telomerase RNA (TR) component, and associated proteins. Other strategies have been developed to target the proteins associated with telomerase at the telomeric ends of chromosomes such as tankyrase. The specific mechanisms that mediate those inhibition effects include small molecules, antisense RNA, and ribozymes. Although the beneficial evidence of telomerase inhibition is obvious, limitations of strategies remain to be resolved to increase the feasibility of clinical application. This analysis will summarize recent developments of strategies in telomerase inhibition.