ALK-activating homologous mutations in LTK induce cellular transformation

Leukocyte tyrosine kinase (LTK) is a receptor tyrosine kinase reported to be overexpressed in human leukemia. Though much regarding the function of LTK remains unknown, it shares a high degree of similarity with anaplastic lymphoma kinase (ALK), which is found mutated in human cancer. In order to determine if LTK has transforming potential, we created two LTK mutants, F568L and R669Q, that correspond to two well-characterized activating mutations of ALK (F1174L and R1275Q). LTK-F568L, but not wildtype LTK or LTK-R669Q, transformed hematopoietic cells to cytokine independence. LTK-F568L exhibited a stronger ability to induce loss of contact inhibition and anchorage-independent growth of epithelial cells compared to LTK-R669Q, while wildtype LTK was non-transforming in the same cells. Likewise, LTK-F568L induced greater neurite outgrowth of PC12 cells than R669Q, while wildtype LTK could not. Correlating with transforming activity, LTK-F568L displayed significantly enhanced tyrosine phosphorylation compared to wildtype LTK and LTK-R668Q and induced activation of various signaling proteins including Shc, ERK and the JAK/STAT pathway. Expression of wildtype LTK or LTK-R669Q generally led to weaker activation of signaling proteins than expression of LTK-F568L, or no activation at all. Thus, mutating LTK at residue F568, and to a lesser extent at R669, activates the receptor tyrosine kinase, inducing cell signaling that results in transforming properties. These studies suggest that aberrant activation of LTK may contribute to neoplastic cell growth.     

Phenylthiourea specifically reduces zebrafish eye size

Phenylthiourea (PTU) is commonly used for inhibiting melanization of zebrafish embryos. In this study, the standard treatment with 0.2 mM PTU was demonstrated to specifically reduce eye size in larval fish starting at three days post-fertilization. This effect is likely the result of a reduction in retinal and lens size of PTU-treated eyes and is not related to melanization inhibition. This is because the eye size of tyr, a genetic mutant of tyrosinase whose activity is inhibited in PTU treatment, was not reduced. As PTU contains a thiocarbamide group which is presented in many goitrogens, suppressing thyroid hormone production is a possible mechanism by which PTU treatment may reduce eye size. Despite the fact that thyroxine level was found to be reduced in PTU-treated larvae, thyroid hormone supplements did not rescue the eye size reduction. Instead, treating embryos with six goitrogens, including inhibitors of thyroid peroxidase (TPO) and sodium-iodide symporter (NIS), suggested an alternative possibility. Specifically, three TPO inhibitors, including those that do not possess thiocarbamide, specifically reduced eye size; whereas none of the NIS inhibitors could elicit this effect. These observations indicate that TPO inhibition rather than a general suppression of thyroid hormone synthesis is likely the underlying cause of PTU-induced eye size reduction. Furthermore, the tissue-specific effect of PTU treatment might be mediated by an eye-specific TPO expression. Compared with treatment with other tyrosinase inhibitors or bleaching to remove melanization, PTU treatment remains the most effective approach. Thus, one should use caution when interpreting results that are obtained from PTU-treated embryos.     

Institutional review boards' use and understanding of certificates of confidentiality

Certificates of Confidentiality, issued by agencies of the U.S. government, are regarded as an important tool for meeting ethical and legal obligations to safeguard research participants' privacy and confidentiality. By shielding against forced disclosure of identifying data, Certificates are intended to facilitate research on sensitive topics critical to the public's health. Although Certificates are potentially applicable to an extensive array of research, their full legal effect is unclear, and little is known about stakeholders' views of the protections they provide. To begin addressing this challenge, we conducted a national survey of institutional review board (IRB) chairs, followed by telephone interviews with selected chairs, to learn more about their familiarity with and opinions about Certificates; their institutions' use of Certificates; policies and practices concerning when Certificates are required or recommended; and the role Certificates play in assessments of research risk. Overall, our results suggest uncertainty about Certificates among IRB chairs. On most objective knowledge questions, most respondents chose the incorrect answer or 'unsure'. Among chairs who reported more familiarity with Certificates, composite opinion scores calculated based on five survey questions were evenly distributed among positive, neutral/middle, and negative views. Further, respondents expressed a variety of ideas about the appropriate use of Certificates, what they are intended to protect, and their effect on research risk. Nevertheless, chairs who participated in our study commonly viewed Certificates as a potentially valuable tool, frequently describing them as an 'extra layer' of protection. These findings lead to several practical observations concerning the need for more stakeholder education about Certificates, consideration of Certificates for a broader range of studies, the importance of remaining vigilant and using all tools available to protect participants' confidentiality, and the need for further empirical investigation of Certificates' effect on researchers and research participants.     

Identification of CD166 as a Surface Marker for Enriching Prostate Stem/Progenitor and Cancer Initiating Cells

New therapies for late stage and castration resistant prostate cancer (CRPC) depend on defining unique properties and pathways of cell sub-populations capable of sustaining the net growth of the cancer. One of the best enrichment schemes for isolating the putative stem/progenitor cell from the murine prostate gland is Lin(-);Sca1(+);CD49f(hi) (LSC(hi)), which results in a more than 10-fold enrichment for in vitro sphere-forming activity. We have shown previously that the LSC(hi) subpopulation is both necessary and sufficient for cancer initiation in the Pten-null prostate cancer model. To further improve this enrichment scheme, we searched for cell surface molecules upregulated upon castration of murine prostate and identified CD166 as a candidate gene. CD166 encodes a cell surface molecule that can further enrich sphere-forming activity of WT LSC(hi) and Pten null LSC(hi). Importantly, CD166 could enrich sphere-forming ability of benign primary human prostate cells in vitro and induce the formation of tubule-like structures in vivo. CD166 expression is upregulated in human prostate cancers, especially CRPC samples. Although genetic deletion of murine CD166 in the Pten null prostate cancer model does not interfere with sphere formation or block prostate cancer progression and CRPC development, the presence of CD166 on prostate stem/progenitors and castration resistant sub-populations suggest that it is a cell surface molecule with the potential for targeted delivery of human prostate cancer therapeutics.     

Evaluation of commercial kits for extraction of DNA and RNA from Clostridium difficile

Commercial nucleic acid extraction kits are a cost effective, efficient and convenient way to isolate DNA and RNA from bacteria. Despite the increasing importance of the gastrointestinal pathogen, Clostridium difficile, and the increased use of nucleic acids in its identification, characterization, and investigation of virulence factors, no standardized or recommended methods for nucleic acid isolation exist. Here, we sought to evaluate 4 commercial DNA extraction kits and 3 commercial RNA extraction kits assessing cost, labor intensity, purity, quantity and quality of nucleic acid preparations. The DNA extraction kits produced a range of concentrations (20.9–546 ng/ml) and A_260/280 ratios (1.92–2.11). All kits were suitable for DNA extraction with the exception of the Roche MagNA pure LC DNA isolation kit III which produced DNA of high yield but with substantial shearing, but that did not affect downstream PCR amplifications. For RNA extraction, the Qiagen RNeasy mini kit stood out producing preparations of consistently higher concentrations and higher RNA integrity numbers (RIN). The Roche MagNA pure LC RNA isolation kit produced preparations that could not be properly assigned RINs due to a failure to remove small RNAs which were interpreted as degradation. Good DNA and RNA yield are critical but methods are often overlooked. This study highlights the potential for critical variation between established commercial systems and the need for assessment of any extraction methods that are used.     

Characterization of microsatellite loci isolated from the blacktip shark and their utility in requiem and hammerhead sharks

We isolated and characterized 16 microsatellite loci from the blacktip shark, Carcharhinus limbatus, and tested cross‐species amplification in 11 Carcharhinus species and five additional shark genera. Thirty‐six (1.6%) and 180 (48%) colonies were positive for dinucleotide repeat motifs from unenriched and enriched libraries, respectively. Heterozygosities of polymorphic loci ranged from 0.04 to 0.96 with two to 22 alleles per locus. Amplification products were observed at nine to 13 loci (five to 11 of which where polymorphic) in 10 Carcharhinus species. Several loci were also polymorphic in each of the additional genera examined.     

The Role of Genetically Modified Mesenchymal Stem Cells in Urinary Bladder Regeneration

Recent studies have demonstrated that mesenchymal stem cells (MSCs) combined with CD34⁺ hematopoietic/stem progenitor cells (HSPCs) can function as surrogate urinary bladder cells to synergistically promote multi-faceted bladder tissue regeneration. However, the molecular pathways governing these events are unknown. The pleiotropic effects of Wnt5a and Cyr61 are known to affect aspects of hematopoiesis, angiogenesis, and muscle and nerve regeneration. Within this study, the effects of Cyr61 and Wnt5a on bladder tissue regeneration were evaluated by grafting scaffolds containing modified human bone marrow derived MSCs. These cell lines were engineered to independently over-express Wnt5a or Cyr61, or to exhibit reduced expression of Cyr61 within the context of a nude rat bladder augmentation model. At 4 weeks post-surgery, data demonstrated increased vessel number (~250 vs ~109 vessels/mm²) and bladder smooth muscle content (~42% vs ~36%) in Cyr61OX (over-expressing) vs Cyr61KD (knock-down) groups. Muscle content decreased to ~25% at 10 weeks in Cyr61KD groups. Wnt5aOX resulted in high numbers of vessels and muscle content (~206 vessels/mm² and ~51%, respectively) at 4 weeks. Over-expressing cell constructs resulted in peripheral nerve regeneration while Cyr61KD animals were devoid of peripheral nerve regeneration at 4 weeks. At 10 weeks post-grafting, peripheral nerve regeneration was at a minimal level for both Cyr61OX and Wnt5aOX cell lines. Blood vessel and bladder functionality were evident at both time-points in all animals. Results from this study indicate that MSC-based Cyr61OX and Wnt5aOX cell lines play pivotal roles with regards to increasing the levels of functional vasculature, influencing muscle regeneration, and the regeneration of peripheral nerves in a model of bladder augmentation. Wnt5aOX constructs closely approximated the outcomes previously observed with the co-transplantation of MSCs with CD34⁺ HSPCs and may be specifically targeted as an alternate means to achieve functional bladder regeneration.     

Comparative Effects of Heterologous TRPV1 and TRPM8 Expression in Rat Hippocampal Neurons

Heterologous channel expression can be used to control activity in select neuronal populations, thus expanding the tools available to modern neuroscience. However, the secondary effects of exogenous channel expression are often left unexplored. We expressed two transient receptor potential (TRP) channel family members, TRPV1 and TRPM8, in cultured hippocampal neurons. We compared functional expression levels and secondary effects of channel expression and activation on neuronal survival and signaling. We found that activation of both channels with appropriate agonist caused large depolarizing currents in voltage-clamped hippocampal neurons, exceeding the amplitude responses to a calibrating 30 mM KCl stimulation. Both TRPV1 and TRPM8 currents were reduced but not eliminated by 4 hr incubation in saturating agonist concentration. In the case of TRPV1, but not TRPM8, prolonged agonist exposure caused strong calcium-dependent toxicity. In addition, TRPV1 expression depressed synaptic transmission dramatically without overt signs of toxicity, possibly due to low-level TRPV1 activation in the absence of exogenous agonist application. Despite evidence of expression at presynaptic sites, in addition to somatodendritic sites, TRPM8 expression alone exhibited no effects on synaptic transmission. Therefore, by a number of criteria, TRPM8 proved the superior choice for control over neuronal membrane potential. This study also highlights the need to explore potential secondary effects of long-term expression and activation of heterologously introduced channels.     

Host specificity under molecular and experimental scrutiny

Current research on the patterns and processes underpinning host specificity in parasites goes well beyond field observations. Molecular studies are used increasingly on a range of parasite taxa to uncover levels of specificity not recognized previously. By contrast, the widespread use of experimental infections indicates that new host-parasite combinations are achieved easily in the laboratory, suggesting that parasites are less specific than they often appear. However, molecular and experimental studies of host specificity must be interpreted with caution: the usefulness of molecular studies is sometimes overstated, whereas experiments are often performed in an unnatural context. Here, the prospects offered by both approaches, as well as their limitations, are highlighted.