Awareness and usage of evidence-based learning strategies among health professions students and faculty.

Introduction: Learning is essential and life-long for faculty and students. Often students and teachers use ineffective learning strategies and are not aware of evidence-based strategies.Methods: A multicenter, international, cross-sectional, online survey-based assessment of awareness of evidence-based learning strategies among health professions students (n = 679) and faculty (n = 205).Results: Students endorsed many study habits which violate evidence-based principles, including studying whatever is due soonest (389/679, 57%), failing to return to course material once a course has ended (465/679, 68%), and re-reading underlined or highlighted notes (298.679, 44%). While the majority of faculty surveyed (125/157, 80%) reported recommending effective study strategies for their students, most students (558/679, 82%) said they did not study the way they do because of instruction from faculty. The majority of faculty (142/156, 91%) and students (347/661, 53%) believe students have different learning styles.Discussion: The results of this study demonstrate health professions students continue to use many ineffective study strategies, and both students and faculty hold misconceptions about evidence-based learning. While planning a curriculum, medical educators should focus on teaching students how to learn and use higher order thinking procedures in addition to teaching content.

Chronic ulcerative stomatitis: Case series of an under-recognized entity.

Chronic ulcerative stomatitis (CUS) is a mucocutaneous condition characterized by chronic relapsing and remitting oral ulcers and erosions. This condition remains under-recognized among dermatopathologists, possibly because of common misdiagnosis as oral erosive lichen planus (LP). We report five cases of CUS in order to raise awareness of this uncommon condition. All patients presented with desquamative gingivitis and/or oral erosions, with biopsies showing lichenoid mucositis and epithelial nuclear IgG deposition on direct immunofluorescence. Recognition of the characteristic direct immunofluorescence findings allows for distinction of chronic ulcerative stomatitis from oral LP and appropriate therapy.

Head and Neck Squamous Cell Carcinoma Metabolism Draws on Glutaminolysis, and Stemness Is Specifically Regulated by Glutaminolysis via Aldehyde Dehydrogenase.

Cancer cells use alternate energetic pathways; however, cancer stem cell (CSC) metabolic energetic pathways are unknown. The purpose of this study was to define the metabolic characteristics of head and neck cancer at different points of its pathogenesis with a focus on its CSC compartment. UPLC-MS/MS-profiling and GC-MS-validation studies of human head and neck cancer tissue, saliva, and plasma were used in conjunction with in vitro and in vivo models to carry out this investigation. We identified metabolite biomarker panels that distinguish head and neck cancer from healthy controls, and confirmed involvement of glutamate and glutaminolysis. Glutaminase, which catalyzes glutamate formation from glutamine, and aldehyde dehydrogenase (ALDH), a stemness marker, were highly expressed in primary and metastatic head and neck cancer tissues, tumorspheres, and CSC versus controls. Exogenous glutamine induced stemness via glutaminase, whereas inhibiting glutaminase suppressed stemness in vitro and tumorigenesis in vivo. Head and neck CSC (CD44hi/ALDHhi) exhibited higher glutaminase, glutamate, and sphere levels than CD44lo/ALDHlo cells. Glutaminase drove transcriptional and translational ALDH expression, and glutamine directed even CD44lo/ALDHlo cells toward stemness. Glutaminolysis regulates tumorigenesis and CSC metabolism via ALDH. These findings indicate that glutamate is an important marker of cancer metabolism whose regulation via glutaminase works in concert with ALDH to mediate cancer stemness. Future analyses of glutaminolytic-ALDH driven mechanisms underlying tumorigenic transitions may help in the development of targeted therapies for head and neck cancer and its CSC compartment.

The soluble interleukin-6 receptor is a mediator of hematopoietic and skeletal actions of parathyroid hormone.

Both PTH and IL-6 signaling play pivotal roles in hematopoiesis and skeletal biology, but their interdependence is unclear. The purpose of this study was to evaluate the effect of IL-6 and soluble IL-6 receptor (sIL-6R) on hematopoietic and skeletal actions of PTH. In the bone microenvironment, PTH stimulated sIL-6R protein levels in primary osteoblast cultures in vitro and bone marrow in vivo in both IL-6(+/+) and IL-6(-/-) mice. PTH-mediated hematopoietic cell expansion was attenuated in IL-6(-/-) compared with IL-6(+/+) bone marrow, whereas sIL-6R treatment amplified PTH actions in IL-6(-/-) earlier than IL-6(+/+) marrow cultures. Blocking sIL-6R signaling with sgp130 (soluble glycoprotein 130 receptor) inhibited PTH-dependent hematopoietic cell expansion in IL-6(-/-) marrow. In the skeletal system, although intermittent PTH administration to IL-6(+/+) and IL-6(-/-) mice resulted in similar anabolic actions, blocking sIL-6R significantly attenuated PTH anabolic actions. sIL-6R showed no direct effects on osteoblast proliferation or differentiation in vitro; however, it up-regulated myeloid cell expansion and production of the mesenchymal stem cell recruiting agent, TGF-ß1 in the bone marrow microenvironment. Collectively, sIL-6R demonstrated orphan function and mediated PTH anabolic actions in bone in association with support of myeloid lineage cells in the hematopoietic system.

Endothelial cell-derived interleukin-6 regulates tumor growth.

BACKGROUND: Endothelial cells play a complex role in the pathobiology of cancer. This role is not limited to the making of blood vessels to allow for influx of oxygen and nutrients required for the high metabolic demands of tumor cells. Indeed, it has been recently shown that tumor-associated endothelial cells secrete molecules that enhance tumor cell survival and cancer stem cell self-renewal. The hypothesis underlying this work is that specific disruption of endothelial cell-initiated signaling inhibits tumor growth. METHODS: Conditioned medium from primary human dermal microvascular endothelial cells (HDMEC) stably transduced with silencing RNA for IL-6 (or controls) was used to evaluate the role of endothelial-derived IL-6 on the activation of key signaling pathways in tumor cells. In addition, these endothelial cells were co-transplanted with tumor cells into immunodefficient mice to determine the impact of endothelial cell-derived IL-6 on tumor growth and angiogenesis. RESULTS: We observed that tumor cells adjacent to blood vessels show strong phosphorylation of STAT3, a key mediator of tumor progression. In search for a possible mechanism for the activation of the STAT3 signaling pathway, we observed that silencing interleukin (IL)-6 in tumor-associated endothelial cells inhibited STAT3 phosphorylation in tumor cells. Notably, tumors vascularized with IL-6-silenced endothelial cells showed lower intratumoral microvessel density, lower tumor cell proliferation, and slower growth than tumors vascularized with control endothelial cells. CONCLUSIONS: Collectively, these results demonstrate that IL-6 secreted by endothelial cells enhance tumor growth, and suggest that cancer patients might benefit from targeted approaches that block signaling events initiated by endothelial cells.

Real-time sharing and expression of migraine headache suffering on Twitter: a cross-sectional infodemiology study.

BACKGROUND: Although population studies have greatly improved our understanding of migraine, they have relied on retrospective self-reports that are subject to memory error and experimenter-induced bias. Furthermore, these studies also lack specifics from the actual time that attacks were occurring, and how patients express and share their ongoing suffering. OBJECTIVE: As technology and language constantly evolve, so does the way we share our suffering. We sought to evaluate the infodemiology of self-reported migraine headache suffering on Twitter. METHODS: Trained observers in an academic setting categorized the meaning of every single "migraine" tweet posted during seven consecutive days. The main outcome measures were prevalence, life-style impact, linguistic, and timeline of actual self-reported migraine headache suffering on Twitter. RESULTS: From a total of 21,741 migraine tweets collected, only 64.52% (14,028/21,741 collected tweets) were from users reporting their migraine headache attacks in real-time. The remainder of the posts were commercial, re-tweets, general discussion or third person's migraine, and metaphor. The gender distribution available for the actual migraine posts was 73.47% female (10,306/14,028), 17.40% males (2441/14,028), and 0.01% transgendered (2/14,028). The personal impact of migraine headache was immediate on mood (43.91%, 6159/14,028), productivity at work (3.46%, 486/14,028), social life (3.45%, 484/14,028), and school (2.78%, 390/14,028). The most common migraine descriptor was "Worst" (14.59%, 201/1378) and profanity, the "F-word" (5.3%, 73/1378). The majority of postings occurred in the United States (58.28%, 3413/5856), peaking on weekdays at 10:00h and then gradually again at 22:00h; the weekend had a later morning peak. CONCLUSIONS: Twitter proved to be a powerful source of knowledge for migraine research. The data in this study overlap large-scale epidemiological studies, avoiding memory bias and experimenter-induced error. Furthermore, linguistics of ongoing migraine reports on social media proved to be highly heterogeneous and colloquial in our study, suggesting that current pain questionnaires should undergo constant reformulations to keep up with modernization in the expression of pain suffering in our society. In summary, this study reveals the modern characteristics and broad impact of migraine headache suffering on patients' lives as it is spontaneously shared via social media.

Can peer feedback substitute for faculty feedback in predoctoral dental education?

PURPOSE/OBJECTIVES: The ability to give and receive feedback is a key skill to develop during predoctoral dental education, and the use of peer feedback specifically offers distinct benefits including a different understanding of material due to peers' proximity of knowledge development and assisting with overburdened instructors. However, it is unclear if peer feedback offers similar quality to instructor feedback. METHODS: Dental students in two different graduation years provided quantitative and qualitative peer feedback on a case-based oral and maxillofacial pathology simulation. The data from these exercises were aggregated and analyzed to compare the quality of qualitative feedback to course examination scores. Student perceptions of peer feedback were also recorded. RESULTS: The mean quality of feedback was not correlated with course examination scores, though the number of times students gave high-quality feedback and received high-quality feedback was correlated with course examination scores. Student feedback overall had a lower quality than instructor feedback, though there was no significant difference between instructor feedback quality and the maximum student feedback quality received. Student perceptions of the utility of feedback were positive. CONCLUSION: While instructor feedback is more reliable and consistent, our findings suggest that in most instances, at least one peer in moderate-sized groups is able to approximate the quality of instructor feedback on case-based assignments.

Exploring HD-tDCS Effect on µ-opioid Receptor and Pain Sensitivity in Temporomandibular Disorder: A Pilot Randomized Clinical Trial Study.

This study explored the association between experimentally-induced pain sensitivity and µ-opioid receptor (µOR) availability in patients with temporomandibular disorder (TMD) and further investigated any changes in the pain and µOR availability following high-definition transcranial direct current stimulation (HD-tDCS) over the primary motor cortex (M1) with pilot randomized clinical trials. Seven patients with TMD completed either active (n = 3) or sham treatment (n = 4) for 10 daily sessions and underwent positron emission tomography (PET) scans with [11C]carfentanil, a selective µOR agonist, a week before and after treatment. PET imaging consisted of an early resting and late phase with the sustained masseteric pain challenge by computer-controlled injection of 5% hypertonic saline. We also included 12 patients with TMD, obtained from our previous study, for baseline PET analysis. We observed that patients with more sensitivity to pain, indicated by lower infusion rate, had less µOR availability in the right amygdala during the late phase. Moreover, active M1 HD-tDCS, compared to sham, increased µOR availability post-treatment in the thalamus during the early resting phase and the amygdala, hippocampus, and parahippocampal gyrus during the late pain challenge phase. Importantly, increased µOR availability post-treatment in limbic structures including the amygdala and hippocampus was associated with decreased pain sensitivity. The findings underscore the role of the µOR system in pain regulation and the therapeutic potential of HD-tDCS for TMD. Nonetheless, large-scale studies are necessary to establish the clinical significance of these results. TRIAL REGISTRATION: ClinicalTrial.gov (NCT03724032) PERSPECTIVE: This study links pain sensitivity and µ-opioid receptors in patients with TMD. HD-tDCS over M1 improved µOR availability, which was associated with reduced pain sensitivity. Implications for TMD pain management are promising, but larger clinical trials are essential for validation.

American Dental Education Association Compendium Entrustable Professional Activities Workgroup report.

PURPOSE: Entrustable professional activities (EPAs) are discrete clinical tasks that can be evaluated to help define readiness for independent practice in the health professions and are intended to increase trust in the dental graduate. EPAs provide a framework that bridges competencies to clinical practice. This report describes the work of the American Dental Education Association (ADEA) Compendium EPA Workgroup to develop a list of EPAs for dental education and supportive resources, including specifications and a glossary. METHODS: Preliminary work including literature and resource review, mapping of existing competencies, and review of other health professions' EPAs informed the development of our EPAs list. Workgroup members achieved consensus using a modified Delphi process. A Qualtrics survey using a validated rubric for the assessment of EPAs as described in peer-reviewed literature was used. Dental educators, including academic deans, were surveyed for feedback on the content and format of the EPAs. RESULTS: Based on findings in the literature analysis of existing EPAs and competencies in health professions, a list of EPAs was developed along with a description of specifications. The EPA workgroup (nine members from multiple institutions) used the Delphi process in receiving feedback from various experts. A list of 11 core EPAs was vetted by dental educators including academic deans (n = âˆ¼23), and the process of development was reviewed by EPAs experts outside dental education. A glossary was developed to align language. CONCLUSION: These EPAs define the scope of dental practice. This report represents Phase 1 of the EPA framework development and vetting process. Future directions will include a broader vetting of the EPA list, faculty development, and national standardized technology that support this work to optimize implementation.

Oral health educators' reflections on teaching 2022 and beyond.

INTRODUCTION: The global pandemic prompted changes in health science education affecting both teaching and learning. This multi-institutional study assesses the near-term implications of these changes on faculty and faculty development. The project goals were to: (1) describe faculty experiences of teaching during the pandemic; (2) identify ways to sustain new pedagogical approaches, (3) describe the types of support faculty members need, and (4) offer recommendations to enhance oral health professions education. METHODS: A mixed-method approach using exploratory sequential design was conducted in two phases collecting qualitative and quantitative data. Focus group participants included didactic, pre-clinical, and clinical faculty in dental school (DMD/DDS), dental hygiene and dental therapy programs, and also faculty members serving in administrative roles in these programs (N = 37). One hundred forty-four faculty participated in the multi-institutional follow-up survey. RESULTS: Focus group and survey results led to 14 recommendations (nine structural and five individual) for oral health profession institutions and educators. CONCLUSION: Oral health profession education faculty were dramatically impacted by the pandemic and new faculty development needs were identified. Traditional faculty development topics and practices may be no longer applicable in the post-COVID-19 environment. Additionally, the pandemic stimulated creative approaches for curriculum design, teaching, and assessment in oral health profession education. Strategies need to be implemented to sustain these innovations.

Small ubiquitin-like modifier (SUMO) modification mediates function of the inhibitory domains of developmental regulators FOXC1 and FOXC2.

FOXC1 and FOXC2 are forkhead transcription factors that play essential roles during development and physiology. Despite their critical role, the mechanisms that regulate the function of these factors remain poorly understood. We have identified conserved motifs within a previously defined N-terminal negative regulatory region of FOXC1/C2 that conforms to the definition of synergy control or SC motifs. Because such motifs inhibit the activity of transcription factors by serving as sites of post-translational modification by small ubiquitin-like modifier (SUMO), we have examined whether FOXC1/C2 are targets of SUMOylation and probed the functional significance of this modification. We find that endogenous FOXC1 forms modified by SUMO2/3 can be detected. Moreover, in cell culture, all three SUMO isoforms are readily conjugated to FOXC1 and FOXC2. The modification can be reconstituted in vitro with purified components and can be reversed in vitro by treatment with the SUMO protease SENP2. SUMOylation of FOXC1 and FOXC2 occurs primarily on one consensus synergy control motif with minor contributions of a second, more degenerate site. Notably, although FOXC1 is also phosphorylated at multiple sites, disruption of sites immediately downstream of the SC motifs does not influence SUMOylation. Consistent with a negative functional role, SUMOylation-deficient mutants displayed higher transcriptional activity when compared with wild type forms despite comparable protein levels and subcellular localization. Thus, the findings demonstrate that SC motifs mediate the inhibitory function of this region by serving as sites for SUMOylation and reveal a novel mechanism for acute and reversible regulation of FOXC1/C2 function.

Pediatric extranodal marginal zone B-cell lymphoma presenting as amyloidosis in minor salivary glands: a case report and review of the literature.

We report an unusual case of an extranodal marginal zone B-cell lymphoma (EMZL) arising in the labial minor salivary gland in an immunocompetent 11-year-old boy. The initial histopathologic review favored localized amyloidosis. However, further evaluation supported the diagnosis of low-grade B-cell lymphoma with plasmacytic differentiation, surrounded by deposits of AL κ-type amyloid. Clinical management consisted of excision with no recurrence at 1-year follow-up. This case demonstrates that a diagnosis of lymphoma must be considered in cases of amyloidosis associated with minor salivary gland involvement, even in children. In addition, we provide a literature review of extranodal marginal zone B-cell lymphoma arising in salivary glands.

The basic helix loop helix transcription factor Twist1 is a novel regulator of ATF4 in osteoblasts.

Parathyroid hormone (PTH) is an essential regulator of endochondral bone formation and an important anabolic agent for the reversal of bone loss. PTH mediates its functions in part by regulating binding of the bone-related activating transcription factor 4 (ATF4) to the osteoblast-specific gene, osteocalcin. The basic helix-loop-helix (bHLH) factors Twist1 and Twist2 also regulate osteocalcin transcription in part through the interaction of the C-terminal "box" domain in these factors and Runx2. In this study, we discovered a novel function of PTH: its ability to dramatically decrease Twist1 transcription. Since ATF4 is a major regulator of the PTH response in osteoblasts, we assessed the mutual regulation between these factors and determined that Twist proteins and ATF4 physically interact in a manner that affects ATF4 DNA binding function. We mapped the interaction domain of Twist proteins to the C-terminal "box" domain and of ATF4, to the N-terminus. Furthermore, we demonstrate that Twist1 overexpression in osteoblasts attenuates ATF4 binding to the osteocalcin promoter in response to PTH. This study thus identifies Twist proteins as novel inhibitory binding partners of ATF4 and explores the functional significance of this interaction.

Receptor-interacting protein (RIP) and Sirtuin-3 (SIRT3) are on opposite sides of anoikis and tumorigenesis.

BACKGROUND: Regulating cross-talk between anoikis and survival signaling pathways is crucial to regulating tissue processes and mitigating diseases like cancer. Previously, the authors demonstrated that anoikis activates a signaling pathway involving the CD95/Fas-mediated signaling pathway that is regulated by receptor-interacting protein (RIP), a kinase that shuttles between Fas-mediated cell death and integrin/focal adhesion kinase (FAK)-mediated survival pathways. Because it is known that sirtuin-3 (SIRT3), a nicotinamide adenine dinucleotide-dependent deacetylase, regulates cell survival, metabolism, and tumorigenesis, the authors hypothesized that SIRT3 may engage in cross-talk with Fas/RIP/integrin/FAK survival-death pathways in cancer cell systems. METHODS: Using immunohistochemical staining, immunoblotting, human tissue microarrays, and overexpression and suppression approaches in vitro and in vivo, the roles of RIP and SIRT3 were examined in oral squamous cell carcinoma (OSCC) anoikis resistance and tumorigenesis. RESULTS: RIP and SIRT3 had opposite expression profiles in OSCC cells and tissues. Stable suppression of RIP enhanced SIRT3 levels, whereas stable suppression of SIRT3 did not impact RIP levels in OSCC cells. The authors observed that, as OSCC cells became anoikis-resistant, they formed multicellular aggregates or oraspheres in suspension conditions, and their expression of SIRT3 increased as their RIP expression decreased. Also, anoikis-resistant OSCC cells with higher SIRT3 and low RIP expression induced an increased tumor burden and incidence in mice, unlike their adherent OSCC cell counterparts. Furthermore, stable suppression of SIRT3 inhibited anoikis resistance and reduced tumor incidence. CONCLUSIONS: The current results indicted that RIP is a likely upstream, negative regulator of SIRT3 in anoikis resistance, and an anoikis-resistant orasphere phenotype defined by higher SIRT3 and low RIP expression contributes to a more aggressive phenotype in OSCC development.

Entrustable professional activities framework for assessment of patient handoffs in dentistry.

PURPOSE/OBJECTIVES: The aim of this study is to report data on the lack of a proper patient handoff system in dentistry and dental education and to present a possible solution to integrate this into curriculum using the "entrustable professional activities" (EPAs) framework. METHODS: Delphi participants from seven US dental schools provided feedback on a preliminary definition of handoff, a mnemonic and an assessment rubric. 2019 American Dental Education Association Commission on Change and Innovation in Dental Education (ADEA CCI) participants further evaluated the handoff EPA using the EQual rubric for EPA quality and structure. RESULTS: Delphi participants identified points of transition in dentistry, selected the D-PASS as a mnemonic, and agreed with the evaluation rubric. The ADEA CCI participants agreed the handoff EPA describes work that is essential for the profession and suitable for entrustment. CONCLUSION: The D-PASS rubric is an effective way to assess patient handoffs.

Magic angle spinning NMR-based metabolic profiling of head and neck squamous cell carcinoma tissues.

High-resolution magic-angle spinning (HR-MAS) proton NMR spectroscopy is used to explore the metabolic signatures of head and neck squamous cell carcinoma (HNSCC) which included matched normal adjacent tissue (NAT) and tumor originating from tongue, lip, larynx and oral cavity, and associated lymph-node metastatic (LN-Met) tissues. A total of 43 tissues (18 NAT, 18 Tumor and 7 LN-Met) from 22 HNSCC patients were analyzed. Principal Component Analysis of NMR data showed a clear classification between NAT and tumor tissues, however, LN-Met tissues were classified among tumor. A partial least-squares discriminant analysis model generated from NMR metabolic profiles was used to differentiate normal from tumor samples (Q(2) > 0.80, Receiver Operator Characteristic area under the curve >0.86, using 7-fold cross validation). HNSCC and LN-Met tissues showed elevated levels of lactate, amino acids including leucine, isoleucine, valine, alanine, glutamine, glutamate, aspartate, glycine, phenylalanine and tyrosine, choline containing compounds, creatine, taurine, glutathione, and decreased levels of triglycerides. These elevated metabolites were associated with highly active glycolysis, increased amino acids influx (anaplerosis) into the TCA cycle, altered energy metabolism, membrane choline phospholipid metabolism, and oxidative and osmotic defense mechanisms. Moreover, decreased levels of triglycerides may indicate lipolysis followed by ß-oxidation of fatty acids that may exist to deliver bioenergy for rapid tumor cell proliferation and growth.

Entrustable professional activities framework for assessment in predoctoral dental education, developed using a modified Delphi process.

PURPOSE/OBJECTIVES: The purpose of this study was to define and develop a set of Entrustable Professional Activities (EPAs) for dental education using a modified Delphi consensus approach. EPAs define the core tasks that a graduating dentist needs to perform independently in practice. The EPA framework facilitates assessment of competencies as they manifest in the tasks and independence needed to be ready for practice. METHODS: Feedback was obtained from participants about a list of EPAs, with modifications made after each of the 3 rounds, using a modified Delphi approach. Phase 1 included attendees at the ADEA Fall 2017 meeting (n = 35) who participated in an EPA workshop primarily composed of academic deans. The Phase 2 "reactor panel" consisted of 10 dental schools' academic deans and other individuals with expertise and interest in dental curriculum and assessment (n = 31). Phase 3 participants were attendees at the ADEA CCI 2019 meeting (n = 91) who also participated in a 2-day EPA workshop. RESULTS: In phase 1, overall ratings for acceptability of the EPAs were satisfactory. In phase 2, the next iteration of EPAs was judged as satisfactory for inclusion in curriculum, match well with clinical practice and clarity. In phase 3, the EPAs were judged as satisfactory for being an "entrustable, essential, and important task of the profession." Qualitative feedback suggested wording, measurability, and specific focus of EPA statements is important. CONCLUSIONS: A preliminary set of EPAs was designed for predoctoral dental education through a systematic, careful consensus building approach involving a diverse set of participants.

Oxidative stress drives disulfide bond formation between basic helix-loop-helix transcription factors.

Basic helix-loop-helix (bHLH) transcription factors including Twist1 and E2a proteins regulate essential processes. These factors bind DNA as homo- or heterodimers and the choice of binding partners determines their functional output. To investigate potential regulators of bHLH dimerization, cells were exposed to the oxidative agent hydrogen peroxide (H(2)O(2)). Western blot analysis in the presence or absence of reducing agents, revealed that H(2)O(2) induces the rapid formation of an intermolecular disulfide bond between Twist1 homodimers and Twist/E2a proteins heterodimers. The disulfide bond is first observed between Twist1 homodimers at 25 mM H(2)O(2) and between Twist1 heterodimers at 75 mM H(2)O(2). This response is dependent upon cell density as H(2)O(2) did not induce disulfide bridge formation between bHLH proteins in cells seeded at high density. In the presence of E proteins, the formation of Twist1/E2a proteins heterodimers is favored over Twist1 homodimers, identifying an oxidative stimulus as an important factor in modulating binding partner specificity. We further demonstrated that a cysteine residue located at the C-terminus of Twist1 and E2a proteins is involved in this response. Disulfide bond formation between Twist1 homodimers significantly reduced its ability to interact with two of its binding partners, Runx2 and HDAC4, indicating that disulfide dimerization in response to H(2)O(2) has functional significance. These data support the conclusion that disulfide bond formation in response to an oxidative stimulus contributes to Twist1 homo- and heterodimerization and raises the possibility that the redox status of a cell may represent an important step in bHLH transcriptional regulation.