Here we present the Transcription Factor Encyclopedia (TFe), a new web-based compendium of mini review articles on transcription factors (TFs) that is founded on the principles of open access and collaboration. Our consortium of over 100 researchers has collectively contributed over 130 mini review articles on pertinent human, mouse and rat TFs. Notable features of the TFe website include a high-quality PDF generator and web API for programmatic data retrieval. TFe aims to rapidly educate scientists about the TFs they encounter through the delivery of succinct summaries written and vetted by experts in the field. TFe is available at http://www.cisreg.ca/tfe.

Perfluorocarboxylic acids (PFCAs) of chain length greater than seven carbon atoms bioconcentrate in the livers of fish. However, a mechanistic cause for the empirically observed increase in the bioconcentration potential of PFCAs as a function of chain length has yet to be determined. To this end, recombinant rat liver fatty acid-binding protein (L-FABP) was purified, and its interaction with PFCAs was characterized in an aqueous system at pH 7.4. Relative binding affinities of L-FABP with PFCAs of carbon chain lengths of five to nine were established fluorimetrically. The energetics, mechanism, and stoichiometry of the interaction of perfluorooctanoic acid (PFOA) with L-FABP were examined further by isothermal titration calorimetry (ITC) and electrospray ionization combined with tandem mass spectrometry (ESI-MS/MS). Perfluorooctanoic acid was shown to bind to L-FABP with an affinity approximately an order of magnitude less than the natural ligand, oleic acid, and to have at least 3:1 PFOA:L-FABP stoichiometry. Two distinct modes of PFOA binding to L-FABP were observed by ESI-MS/MS analysis; in both cases, PFOA binds solely as the neutral species under typical physiological pH and aqueous concentrations of the anion. A comparison of their chemical and physical properties with other well-studied biologically relevant chemicals showed that accumulation of PFCAs in proteins as the neutral species is predictable. For example, the interaction of PFOA with L-FABP is almost identical to that of the acidic ionizing drugs ketolac, ibuprofen, and warfarin that show specificity to protein partitioning with a magnitude that is proportional to the K(OW) (octanol-water partitioning) of the neutral species. The experimental results suggest that routine pharmacochemical models may be applicable to predicting the protein-based bioaccumulation of long-chain PFCAs.

Introduction / Innovation Concept: Insertion of an internal jugular (IJ) central venous catheter (CVC) under ultrasound guidance (USG) is a complex skill that requires considerable practice in order to achieve technical proficiency. Simulation allows novices to engage in structured and high volume repetitive practice of USG IJ CVC insertion and to work through a predictable pattern of errors prior to real patient encounters. Based on earlier work on learning curves for CVC insertion, this curriculum uses a model of simulation-based high volume deliberate practice of the fundamental skills of USG CVC insertion, and was designed with careful consideration of the conditions associated with optimal learning and improvement of performance. Methods: Eight residents (post graduate year 2) from the Departments of Emergency Medicine and Anesthesiology engaged in deliberate practice of USG CVC insertion during three two-hour sessions, at 2-week intervals. Progress of the residents was monitored with direct observation and regular hand motion analysis (HMA), which was compared to performance metrics set by a local expert. Curriculum, Tool, or Material: Students reviewed online introductory ultrasound video and articles outlining internal jugular (IJ) and femoral CVC insertion prior to the first session. Session 1 focused on ultrasound skills including knobology, transducer movement, and needle tracking. This was followed by 60 minutes of deliberate practice of the skills of USG CVC insertion on both femoral and IJ models. During sessions 2/3, students practiced complete gowning and draping using sterile technique. This was followed again by deliberate practice of the skills of USG CVC insertion on both femoral and IJ models. Students received coaching and feedback throughout all sessions, with HMA assessment of USG IJ CVC insertion at the beginning and end of each session. After three training sessions, consisting of 85 total attempts, 5/8 residents surpassed the expert benchmark for probe hand motion, 6/8 for needle hand motion, and 1/8 for total procedure time, with the remaining residents approaching the expert benchmark for each metric. Conclusion: We have successfully developed a simulation-based curriculum for USG IJ CVC placement. Residents demonstrated continuous improvement in each session, approaching or exceeding the expert benchmarks by the end of the third session.

The oncogenic transcription factor E2A-PBX1 is expressed consequent to chromosomal translocation 1;19 and is an important oncogenic driver in cases of pre-B-cell acute lymphoblastic leukemia (ALL). Elucidating the mechanism by which E2A-PBX1 induces lymphoid leukemia would be expedited by the availability of a tractable experimental model in which enforced expression of E2A-PBX1 in hematopoietic progenitors induces pre-B-cell ALL. However, hematopoietic reconstitution of irradiated mice with bone marrow infected with E2A-PBX1-expressing retroviruses consistently gives rise to myeloid, not lymphoid, leukemia. Here, we elucidate the hematopoietic consequences of forced E2A-PBX1 expression in primary murine hematopoietic progenitors. We show that introducing E2A-PBX1 into multipotent progenitors permits the retention of myeloid potential but imposes a dense barrier to lymphoid development prior to the common lymphoid progenitor stage, thus helping to explain the eventual development of myeloid, and not lymphoid, leukemia in transplanted mice. Our findings also indicate that E2A-PBX1 enforces the aberrant, persistent expression of some genes that would normally have been down-regulated in the subsequent course of hematopoietic maturation. We show that enforced expression of one such gene, Hoxa9, a proto-oncogene associated with myeloid leukemia, partially reproduces the phenotype produced by E2A-PBX1 itself. Existing evidence suggests that the 1;19 translocation event takes place in committed B-lymphoid progenitors. However, we find that retrovirus-enforced expression of E2A-PBX1 in committed pro-B-cells results in cell cycle arrest and apoptosis. Our findings indicate that the neoplastic phenotype induced by E2A-PBX1 is determined by the developmental stage of the cell into which the oncoprotein is introduced.

The oncoprotein E2A-PBX1 is produced by the t(1;19) chromosomal translocation in pre-B cell acute lymphoblastic leukemia (ALL). We and others have shown that retrovirus-enforced expression of E2A-PBX1 in mouse bone marrow results in a lethal leukemia with short latency. Suprisingly, almost all animals die of myeloid leukemia rather than the B-lymphoid disease observed clinically. The E-protein E47, a product of the wild-type E2A gene, is required in the earliest stages of B-lymphoid commitment. E47 and E2A-PBX1 are identical in their amino-terminal 483 residues and this region includes transcriptional activation domains capable of recruiting CBP/p300 and presumably other co-regulators. Therefore, we hypothesized that E2A-PBX1 may block B-lymphoid commitment by exerting dominant-negative effects on E-proteins including E47. Bone marrow cells transduced with E2A-PBX1 failed to repopulate the B-lymphoid compartment at two weeks post-reconstitution of sub-lethally-irradiated mice, whereas there was exuberant proliferation of transduced myeloid progenitors suggesting selective intereference with B-lymphopoiesis. This phenomenon was examined further using a more experimentally tractable in vitro system. “Lineage negative” hematopoietic progenitors from fetal livers differentiate rapidly to committed B-lymphoid progenitors (B220+, CD19+, Mac-1-, Gr-1-) on co-culture with OP9 stromal cells in the presence of interleukin-7 (IL-7). However, enforced expression of E2A-PBX1 produced a myeloid immunophenotype (B220-, CD19-, Mac-1+, Gr-1+). Furthermore, these cells are dependent on myeloid cytokines, display no IL-7 responsiveness, and have a high forward scatter/side scatter profile. RT-PCR analysis shows severely reduced levels of lymphoid-associated transcripts (E2A, Ebf1, Pax5 and Irf8) and substantially elevated levels of myeloid associated transcripts (Csfr1, Id1 and Pu.1) relative to control lymphoid cells. All of these properties are characteristic of macrophage progenitors, a fate adopted by E2A−/− cells under similar culture conditions. Our findings showing that E2A-PBX1 is capable of altering the lineage fate of early hematopoietic progenitors in a manner similar to gene targeting of E2A provide support, albeit circumstantial, for a mechanism that involves dominant-negative effects on E-proteins and perhaps competition for limiting co-regulators such as CBP/p300. Consistent with the latter possibility, murine bone marrow cells expressing an E2A-PBX1 mutant impaired in CBP/p300 recruitment retain a minor propensity to repopulate the B-lymphoid compartment of irradiated transplant recipients. The results of experiments to evaluate the impact of E2A-PBX1 on transcriptional induction by E47 will be presented. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3097.