Persistence of changed attitudes among students in an integrated anatomy curriculum.

Many medical schools in the United States have integrated anatomy into an organ-based preclinical curriculum with some schools using anatomy as the cornerstone of their reorganization efforts. Curricular change could affect one or more of the three domains of learning, with the cognitive domain often scrutinized exclusively. A previous study reported the impact of anatomy integration on the affective domain, specifically, student attitudes toward learning anatomy. This mixed methods follow-up study asked if the observed attitudinal changes and lack of effect on student knowledge and confidence persisted using knowledge and confidence surveys, focus groups, internal and national surveys, and United States Medical Licensing Examination® performance metrics. Results evidenced the persistence of specific attitudinal differences between cohorts with blocked versus integrated anatomy with no apparent short- or long-term differences in anatomy learning or confidence in this learning. Altered attitudes included lower value placed on working in teams and reflective practices, and less recognition of anatomy's contribution (or less contribution of anatomy learning) to professional identity formation. These attitudinal changes could result in a weaker foundation for building collaborative skills throughout the medical curriculum. A decreased sense of student engagement also followed curricular change, as assessed by data from the American Association of Medical Colleges Year 2 Questionnaire. Overall, results emphasized the necessity of anticipating, monitoring, and if necessary, addressing changes in the affective domain when undertaking curricular change.

Cold-Inducible RNA Binding Protein Impedes Breast Tumor Growth in the PyMT Murine Model for Breast Cancer.

RNA binding proteins (RBPs) post-transcriptionally regulate gene expression by associating with regulatory sequences in the untranslated regions of mRNAs. Cold-inducible RBP (CIRP) is a stress-induced RBP that was recently shown to modulate inflammation in response to cellular stress, where it increases or decreases pro-tumorigenic (proinflammatory) cytokines in different contexts. CIRP expression is altered in several cancers, including breast cancer, but the effects of CIRP on inflammation in breast cancer is not known. Here, we investigate if CIRP alters growth and the inflammatory profile of breast tumors. Transgenic mice overexpressing CIRP in the mammary epithelium were crossed with the PyMT mouse model of breast cancer, and the effects on both early and late tumorigenesis and inflammation were assessed. The effects of CIRP knockdown were also assessed in Py2T cell grafts. Overexpression of CIRP led to decreased tumorigenesis in the PyMT mouse model. Conversely, the knockdown of CIRP in Py2T cell grafts led to increased tumor growth. Luminex cytokine assays assessed the effects on the inflammatory environment. CIRP/PyMT mammary glands/mammary tumors and serum had decreased cytokines that promote inflammation, angiogenesis, and metastasis compared to PyMT mammary glands and serum, documenting a shift towards an environment less supportive of tumorigenesis. CIRP overexpression also decreased CD4+ helper T cells and increased CD8+ cytotoxic T cells in mammary tumors. Overall, these data support a role for CIRP as a potent antitumor molecule that suppresses both local and systemic pro-tumorigenic inflammation.

Applying holistic review practices to a Combined Baccalaureate/Medical Degree Program: Reflections on lessons learned.

PROBLEM: Despite the implementation of holistic review in the medical school application process, there is little information about how this can be utilized in Combined Baccalaureate/Medical Degree pipeline programs, especially since many programs offer reserved spots to their students in the medical school. Implementing holistic review in a Combined Baccalaureate/Medical Degree program and intentionally structuring it to align with the medical school mission and admissions practices and processes, can improve the diversification of the physician workforce, contribute to more primary care doctors, and promote in-state practice. INTERVENTION: Utilizing the medical school admissions by-laws, committee structure, shared training, and educational processes, we successfully engrained in our committee members the values and mission alignment to select the best applicants to fulfill the medical school mission using holistic review. To our knowledge, no other program has written about how holistic review is used in Combined Baccalaureate/Medical Degree programs and how it contributes to program outcomes. CONTEXT: The Combined Baccalaureate/Medical Degree Program is a partnership between the undergraduate College of Arts and Sciences and the School of Medicine. The Combined Baccalaureate/Medical Degree admissions committee is a subcommittee of the School of Medicine admissions committee but has a separate membership. Hence, the holistic admissions process for the program mirrors the School of Medicine admissions process. To determine the outcome of this process, we analyzed practice specialty, practice location, gender, race and ethnicity of program alumni. IMPACT: To date, the Combined Baccalaureate/Medical Degree holistic admissions processes have supported the medical school mission, "…To meet the physician workforce needs of the state by selection of students who are likely to train in specialty areas of need and to remain in or return to the areas of our state needing physicians." This implementation has resulted in 75% (37/49) of our practicing alumni selecting a primary care specialty, and 69% (34/49) practicing in the state. In addition, 55% (27/49) identify as Underrepresented in Medicine. LESSONS LEARNED: We observed that having an intentional structured alignment in place allowed for implementation of holistic practices in the Combined Baccalaureate/Medical Degree admissions process. The high retention rates and specialty of graduates from the Combined Baccalaureate/Medical Degree Program support our intentional efforts to diversify our admissions committees and align the Combined Baccalaureate/Medical Degree program's holistic review admissions process with our School of Medicine mission and admissions practices and processes, as key strategies to reach our diversity-related goals.

Impact of the COVID-19 pandemic on rural obstetrics practices in New Mexico.

CONTEXT: During pregnancy, the immune system is altered, putting women at increased risk of complications from respiratory viruses. There is limited information about the effects of COVID-19 on pregnant women and obstetrics programs, particularly in rural regions. AIMS: Most published reports have been from large urban hospitals. This study sought to gain insight into how the COVID-19 pandemic is impacting rural obstetrics programs. MATERIALS AND METHODS: This qualitative study surveyed participants who worked in rural obstetrics programs in New Mexico using a free response questionnaire. RESULTS: The pandemic has changed the obstetrics experience in rural New Mexico by impacting the relationship between patients and providers and altering the family-centered model of birth. Difficulties unique to rural obstetrics included lack of transportation, limited hospital rooms and limited staff, including OB providers, nurses and housekeeping. Wellness has been impacted for providers, manifested in increased anxiety, stress and burnout. Patients reported increased anxiety, decreased family support, and potential disruptions in maternal-infant bonding. CONCLUSIONS: Rural hospitals and clinics in New Mexico and across the United States operate with challenges at baseline, with many clinics across the nation closing, leading to increasing shortages of healthcare services in rural areas. This study showed that COVID-19 has increased the challenges that rural obstetrics providers face, altering the way they practice and creating uncertainty for the future due to potentially permanent changes to their practice. Future research will explore the lasting effects of the pandemic on rural obstetrics providers specifically, and rural hospitals generally.

Anatomy integration: Effective change or change of affect?

Anatomy is fundamental to clinical practice, is considered a rite of passage in becoming a physician and is key to professional identity formation. The anatomy course that began the medical curriculum at the University of New Mexico School of Medicine was recently dissolved to address content and process gaps in the pre-clinical curriculum. Anatomy was integrated into the organ system blocks to make room for new courses to address content gaps. Previous reports of anatomy integration document more positive attitudes and perceptions to teaching anatomy in context, as compared to an independent course. The current prospective study compared two medical student cohorts to determine the effects of teaching anatomy in and out of context on the cognitive and affective domains of learning. In a pre, post, and follow-up design, methods included content assessments, confidence probes, and attitude surveys informed by focus groups. Results indicated that anatomical knowledge and student confidence was gained and mastered in both curricula. Initial acquisition of content was higher in the integrated curriculum, but not maintained. Students in the integrated curriculum displayed a different relationship to learning anatomy, appearing more concerned with their personal progression than with the connection of anatomy to medical practice or patient care. These students also agreed less with statements related to working in teams, reflective practices and professional identity formation. Further studies will determine if this difference will diminish with continued exposure to anatomy and may inform future curricular adjustments. Anat Sci Educ. © 2018 American Association of Anatomists.

Cold-inducible RNA binding protein in cancer and inflammation.

RNA binding proteins (RBPs) play key roles in RNA dynamics, including subcellular localization, translational efficiency and metabolism. Cold-inducible RNA binding protein (CIRP) is a stress-induced protein that was initially described as a DNA damage-induced transcript (A18 hnRNP), as well as a cold-shock domain containing cold-stress response protein (CIRBP) that alters the translational efficiency of its target messenger RNAs (mRNAs). This review summarizes recent work on the roles of CIRP in the context of inflammation and cancer. The function of CIRP in cancer appeared to be solely driven though its functions as an RBP that targeted cancer-associated mRNAs, but it is increasingly clear that CIRP also modulates inflammation. Several recent studies highlight roles for CIRP in immune responses, ranging from sepsis to wound healing and tumor-promoting inflammation. While modulating inflammation is an established role for RBPs that target cytokine mRNAs, CIRP appears to modulate inflammation by several different mechanisms. CIRP has been found in serum, where it binds the TLR4-MD2 complex, acting as a Damage-associated molecular pattern (DAMP). CIRP activates the NF-κB pathway, increasing phosphorylation of Iκκ and IκBα, and stabilizes mRNAs encoding pro-inflammatory cytokines. While CIRP promotes higher levels of pro-inflammatory cytokines in certain cancers, it also decreases inflammation to accelerate wound healing. This dichotomy suggests that the influence of CIRP on inflammation is context dependent and highlights the importance of detailing the mechanisms by which CIRP modulates inflammation. WIREs RNA 2018, 9:e1462. doi: 10.1002/wrna.1462 This article is categorized under: RNA in Disease and Development > RNA in Disease RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.

Please exit safely: maternal and twin pair neonatal outcomes according to delivery mode when twin A is vertex.

OBJECTIVE: To investigate maternal and infant outcomes associated with delivery mode for twins with a cephalic presenting twin. METHODS: Linked birth certificate and ICD hospital discharge data were analyzed retrospectively for 5573 mothers and their respective twin pairs born live at 34-42 weeks' gestation, with twin A vertex, in Washington State from 1997-2007. Relative risks (RR) and 95% confidence intervals of adverse maternal and twin pair outcomes were calculated for vaginal delivery or cesarean during labor in comparison to cesarean without labor. RESULTS: Vaginal delivery or cesarean during labor was associated with significantly elevated rates of maternal hemorrhage (RR = 2.8 [2.2,3.7]), infection (RR = 2.2 [1.5,3.3]), twin pair birth injury (RR = 2.6 [1.2,5.4]) and low 5-min Apgar scores (RR = 1.4 [1.1,1.8]) and with significantly lower rates of ventilation among preterm twin pairs only (RR = 0.8 [0.7,0.9]). The lowest rate of combined poor short-term outcomes occurred in mothers and twin pairs delivered by cesarean without labor (23%) and the highest rates occurred in those with operative vaginal or cesarean during labor (39% and 34%, respectively). Among women in labor, 35% of nulliparas achieved spontaneous vaginal delivery of both twins compared to 63% of non-nulliparas. CONCLUSION: For nulliparous women who carry twins to term, planned cesarean may improve outcomes.

Cold-inducible RNA binding protein in mouse mammary gland development.

RNA binding proteins (RBPs) regulate gene expression by controlling mRNA export, translation, and stability. When altered, some RBPs allow cancer cells to grow, survive, and metastasize. Cold-inducible RNA binding protein (CIRP) is overexpressed in a subset of breast cancers, induces proliferation in breast cancer cell lines, and inhibits apoptosis. Although studies have begun to examine the role of CIRP in breast and other cancers, its role in normal breast development has not been assessed. We generated a transgenic mouse model overexpressing human CIRP in the mammary epithelium to ask if it plays a role in mammary gland development. Effects of CIRP overexpression on mammary gland morphology, cell proliferation, and apoptosis were studied from puberty through pregnancy, lactation and weaning. There were no gross effects on mammary gland morphology as shown by whole mounts. Immunohistochemistry for the proliferation marker Ki67 showed decreased proliferation during the lactational switch (the transition from pregnancy to lactation) in mammary glands from CIRP transgenic mice. Two markers of apoptosis showed that the transgene did not affect apoptosis during mammary gland involution. These results suggest a potential in vivo function in suppressing proliferation during a specific developmental transition.

Quantum dot assisted tracking of the intracellular protein Cyclin E in Xenopus laevis embryos.

BACKGROUND: Luminescent semiconductor nanocrystals, also known as quantum dots (QD), possess highly desirable optical properties that account for development of a variety of exciting biomedical techniques. These properties include long-term stability, brightness, narrow emission spectra, size tunable properties and resistance to photobleaching. QD have many promising applications in biology and the list is constantly growing. These applications include DNA or protein tagging for in vitro assays, deep-tissue imaging, fluorescence resonance energy transfer (FRET), and studying dynamics of cell surface receptors, among others. Here we explored the potential of QD-mediated labeling for the purpose of tracking an intracellular protein inside live cells. RESULTS: We manufactured dihydrolipoic acid (DHLA)-capped CdSe-ZnS core-shell QD, not available commercially, and coupled them to the cell cycle regulatory protein Cyclin E. We then utilized the QD fluorescence capabilities for visualization of Cyclin E trafficking within cells of Xenopus laevis embryos in real time. CONCLUSIONS: These studies provide "proof-of-concept" for this approach by tracking QD-tagged Cyclin E within cells of developing embryos, before and during an important developmental period, the midblastula transition. Importantly, we show that the attachment of QD to Cyclin E did not disrupt its proper intracellular distribution prior to and during the midblastula transition. The fate of the QD after cyclin E degradation following the midblastula transition remains unknown.

MicroRNA-16 modulates HuR regulation of cyclin E1 in breast cancer cells.

RNA binding protein (RBPs) and microRNAs (miRNAs or miRs) are post-transcriptional regulators of gene expression that are implicated in development of cancers. Although their individual roles have been studied, the crosstalk between RBPs and miRNAs is under intense investigation. Here, we show that in breast cancer cells, cyclin E1 upregulation by the RBP HuR is through specific binding to regions in the cyclin E1 mRNA 3' untranslated region (3'UTR) containing U-rich elements. Similarly, miR-16 represses cyclin E1, dependent on its cognate binding sites in the cyclin E1 3'UTR. Evidence in the literature indicates that HuR can regulate miRNA expression and recruit or dissociate RNA-induced silencing complexes (RISC). Despite this, miR-16 and HuR do not affect the other's expression level or binding to the cyclin E1 3'UTR. While HuR overexpression partially blocks miR-16 repression of a reporter mRNA containing the cyclin E1 3'UTR, it does not block miR-16 repression of endogenous cyclin E1 mRNA. In contrast, miR-16 blocks HuR-mediated upregulation of cyclin E1. Overall our results suggest that miR-16 can override HuR upregulation of cyclin E1 without affecting HuR expression or association with the cyclin E1 mRNA.

Microenvironmental control of the breast cancer cell cycle.

The mammary gland is one of the best-studied examples of an organ whose structure and function are influenced by reciprocal signaling and communication between cells and their microenvironment. The mammary epithelial cell (MEC) microenvironment includes stromal cells and extracellular matrix (ECM). Abundant evidence shows that the ECM and growth factors co-operate to regulate cell cycle progression, and that the ECM is altered in breast tumors. In particular, mammographically dense breast tissue is a significant risk factor for developing breast carcinomas. Dense breast tissue is associated with increased stromal collagen and epithelial cell content. In this article, we overview recent studies addressing the effects of ECM composition on the breast cancer cell cycle. Although the normal breast ECM keeps the MEC cycle in check, the ECM remodeling associated with breast cancer positively regulates the MEC cycle. ECM effects on the downstream biochemical and mechanosignaling pathways in both normal and tumorigenic MECs will be reviewed.

Developmental downregulation of Xenopus cyclin E is phosphorylation and nuclear import dependent and is mediated by ubiquitination.

Cyclins are regulatory subunits that bind to and activate catalytic Cdks. Cyclin E associates with Cdk2 to mediate the G1/S transition of the cell cycle. Cyclin E is overexpressed in breast, lung, skin, gastrointestinal, cervical, and ovarian cancers. Its overexpression correlates with poor patient prognosis and is involved in the etiology of breast cancer. We have been studying how cyclin E is normally downregulated during development in order to determine if disruption of similar mechanisms could either contribute to its overexpression in cancer, or be exploited to decrease its expression. In Xenopus laevis embryos, cyclin E protein level is high and constant until its abrupt destabilization by an undefined mechanism after the 12th cell cycle, which corresponds to the midblastula transition (MBT) and remodeling of the embryonic to the adult cell cycle. Since degradation of mammalian cyclin E is regulated by the ubiquitin proteasome system and is phosphorylation dependent, we examined the role of phosphorylation in Xenopus cyclin E turnover. We show that similarly to human cyclin E, phosphorylation of serine 398 and threonine 394 plays a role in cyclin E turnover at the MBT. Immunofluorescence analysis shows that cyclin E relocalizes from the cytoplasm to the nucleus preceding its degradation. When nuclear import is inhibited, cyclin E stability is markedly increased after the MBT. To investigate whether degradation of Xenopus cyclin E is mediated by the proteasomal pathway, we used proteasome inhibitors and observed a progressive accumulation of cyclin E in the cytoplasm after the MBT. Ubiquitination of cyclin E precedes its proteasomal degradation at the MBT. These results show that cyclin E destruction at the MBT requires both phosphorylation and nuclear import, as well as proteasomal activity.

Three-dimensional collagen represses cyclin E1 via ß1 integrin in invasive breast cancer cells.

The behavior of breast epithelial cells is influenced by their microenvironment which includes stromal cells and extracellular matrix (ECM). During cancer progression, the tissue microenvironment fails to control proliferation and differentiation, resulting in uncontrolled growth and invasion. Upon invasion, the ECM encountered by breast cancer cells changes from primarily laminin and collagen IV to primarily collagen I. We show here that culturing invasive breast cancer cells in 3-dimensional (3D) collagen I inhibits proliferation through direct regulation of cyclin E1, a G(1)/S regulator that is overexpressed in breast cancer. When the breast cancer cell line MDA-MB-231 was cultured within 3D collagen I gels, the G(1)/S transition was inhibited as compared to cells cultured on conventional 2D collagen or plastic dishes. Cells in 3D collagen downregulated cyclin E1 protein and mRNA, with no change in cyclin D1 level. Cyclin D1 was primarily cytoplasmic in 3D cultures, and this was accompanied by decreased phosphorylation of Rb, a nuclear target for both cyclin E1- and cyclin D1-associated kinases. Positive regulators of cyclin E1 expression, the transcription factor c-Myc and cold-inducible RNA binding protein (CIRP), were decreased in 3D collagen cultures, while the collagen I receptor ß1 integrin was greatly increased. Inhibition of ß1 integrin function rescued proliferation and cyclin E1 expression as well as c-Myc expression and Rb phosphorylation, but cyclin D1 remained cytoplasmic. We conclude that cyclin E1 is repressed independent of effects on cyclin D1 in a 3D collagen environment and dependent on ß1 integrin interaction with collagen I, reducing proliferation of invasive breast cancer cells.

Increasing rates of preterm twin births coincide with improving twin pair survival.

OBJECTIVE: To examine trends in twin gestational age over time, with adjustment for potential confounding factors, and to assess twin pair mortality and respiratory support over time. METHODS: Rates of preterm births, respiratory support, and neonatal mortality were calculated for 21,569 twin pairs born from 1980 to 2005 in Washington State, using birth certificate and hospital discharge data. Fetal death risks were determined on a "per-pair-at-risk" basis. RESULTS: While the proportion of twins born at 24-31 weeks remained stable at 8%, the proportion born at 32-36 weeks increased from 28% to 48%, and the proportion at 37-42 weeks declined from 64% to 44% (P<0.0001). Controlling individually for a variety of factors, such as maternal age, race, parity, and mode of delivery did not diminish the highly significant trend of increasing preterm births (P<0.0001 for each). Twin pair neonatal mortality decreased significantly through time (P<0.0001); however, the rate of pairs with one or both infants requiring oxygen or ventilation increased significantly through time (P<0.0001). Fetal death risks declined for term twins. CONCLUSIONS: The proportion of twins born at 32-36 weeks' gestation has increased over time, along with requirement for respiratory support. Twin pair mortality decreased from 1980 to 2005.

The F-box protein Cdc4/Fbxw7 is a novel regulator of neural crest development in Xenopus laevis.

BACKGROUND: The neural crest is a unique population of cells that arise in the vertebrate ectoderm at the neural plate border after which they migrate extensively throughout the embryo, giving rise to a wide range of derivatives. A number of proteins involved in neural crest development have dynamic expression patterns, and it is becoming clear that ubiquitin-mediated protein degradation is partly responsible for this. RESULTS: Here we demonstrate a novel role for the F-box protein Cdc4/Fbxw7 in neural crest development. Two isoforms of Xenopus laevis Cdc4 were identified, and designated xCdc4alpha and xCdc4beta. These are highly conserved with vertebrate Cdc4 orthologs, and the Xenopus proteins are functionally equivalent in terms of their ability to degrade Cyclin E, an established vertebrate Cdc4 target. Blocking xCdc4 function specifically inhibited neural crest development at an early stage, prior to expression of c-Myc, Snail2 and Snail. CONCLUSIONS: We demonstrate that Cdc4, an ubiquitin E3 ligase subunit previously identified as targeting primarily cell cycle regulators for proteolysis, has additional roles in control of formation of the neural crest. Hence, we identify Cdc4 as a protein with separable but complementary functions in control of cell proliferation and differentiation.

Cold-inducible RNA-binding protein contributes to human antigen R and cyclin E1 deregulation in breast cancer.

The cell cycle regulator cyclin E1 is aberrantly expressed in a variety of human cancers. In breast cancer, elevated cyclin E1 correlates with poor outcome, as do high cytoplasmic levels of the stress-induced RNA-binding protein human antigen R (HuR). We showed previously that increased cytoplasmic HuR elevates cyclin E1 in MCF-7 breast cancer cells by stabilizing its mRNA. We show here that cold-inducible RNA-binding protein (CIRP) co-regulates cyclin E1 with HuR in breast cancer cells. CIRP had been shown to interact with HuR in Xenopus laevis oocytes and to be decreased in endometrial cancer. To investigate if human CIRP and HuR co-regulate cyclin E1, HuR and CIRP levels were altered in MCF-7 cells and effects on cyclin E1 assessed. Altering HuR expression resulted in a reciprocal change in CIRP expression, while altering CIRP expression resulted in corresponding changes in HuR and cyclin E1 expression. CIRP and HuR co-precipitated in the presence of RNA and CIRP enhanced HuR binding to the cyclin E1 mRNA and increased cyclin E1 mRNA stability. CIRP co-localized with HuR predominantly in the nucleus, but also in discrete cytoplasmic foci identified as stress granules (SGs). CIRP overexpression increased the number of HuR-containing SGs, while its knockdown decreased them. Our results suggest that CIRP positively regulates HuR, ultimately resulting in increased protein synthesis of at least one of its targets.

MicroRNA-125a represses cell growth by targeting HuR in breast cancer.

MicroRNAs (miRNAs) are a class of naturally occurring, small, non-coding RNAs that control gene expression during development,normal cell function and disease. Although there is emerging evidence that some miRNAs can function as oncogenes or tumor suppressors, there is limited understanding of the role of miRNAs in cancer. In this study, we observed that the expression of miR-125a was inversely correlated with HuR expression in several different breast carcinoma cell lines. HuR is a stress-induced RNA binding protein whose expression is elevated or localization perturbed in several different cancers. Increased cytoplasmic localization of HuR is a prognostic marker in breast cancer. Real time PCR and gene reporter assays indicated that HuR was translationally repressed by miR-125a. Re-establishing miR-125a expression in breast cancer cells decreased HuR protein level and inhibited cell growth. Using MCF-7 breast cancer cells, we further clarified that miR-125a inhibited cell growth via a dramatic suppression of cell proliferation and promotion of apoptosis.In addition, cell migration was also inhibited by miR-125a overexpression. Importantly, the repression of cell proliferation and migration engendered by miR-125a was partly rescued by HuR re-expression. Our results suggest that miR-125a may function as a tumor suppressor for breast cancer, with HuR as a direct and functional target.

Deadenylation of maternal mRNAs mediated by miR-427 in Xenopus laevis embryos.

We show that microRNA-427 (miR-427) mediates the rapid deadenylation of maternal mRNAs after the midblastula transition (MBT) of Xenopus laevis embryogenesis. By MBT, the stage when the embryonic cell cycle is remodeled and zygotic transcription of mRNAs is initiated, each embryo has accumulated approximately 10(9) molecules of miR-427 processed from multimeric pri-miR-427 transcripts synthesized after fertilization. We demonstrate that the maternal mRNAs for cyclins A1 and B2 each contain a single miR-427 target sequence, spanning less than 30 nucleotides, that is both necessary and sufficient for deadenylation, and that inactivation of miR-427 leads to stabilization of the mRNAs. Although this deadenylation normally takes place after MBT, exogenous miRNAs produced prematurely in vivo can promote deadenylation prior to MBT, indicating that turnover of the maternal mRNAs is limited by the amount of accumulated miR-427. Injected transcripts comprised solely of the cyclin mRNA 3' untranslated regions or bearing a 5' ApppG cap undergo deadenylation, showing that translation of the targeted RNA is not required. miR-427 is not unique in promoting deadenylation, as an unrelated miRNA, let-7, can substitute for miR-427 if the reporter RNA contains an appropriate let-7 target site. We propose that miR-427, like the orthologous miR-430 of zebrafish, functions to down-regulate expression of maternal mRNAs early in development.

ElrA and AUF1 differentially bind cyclin B2 mRNA.

In Xenopus embryos, maternal cyclins drive the first 12 cell divisions after which several cyclins are terminally degraded, including cyclin B2. Cyclin B2 disappearance is due to transcription-mediated mRNA deadenylation at the midblastula transition, when transcription initiates and the cell cycle lengthens. To further define the mechanism, we characterized proteins capable of binding cyclin B2 3'UTR. We show that ElrA and AUF1 compete for binding to regions containing cytoplasmic polyadenylation elements (CPEs), with AUF1 binding increasing at the midblastula transition. Deletion of both CPEs abrogates polyadenylation but has no effect on deadenylation or binding of ElrA or AUF1. Overexpression of ElrA or AUF1 does not alter cyclin B2 mRNA stability. These results show that ElrA and AUF1 bind to cyclin B2 mRNA independent of CPEs and function by binding other elements.

Increasing rates of sex-discordant twins no longer correspond to decreasing perinatal mortality rates.

OBJECTIVE: To analyze dizygotic twinning rates and outcomes over a 25-year period. METHODS: Birth and fetal death certificates from 1980-2004 in Washington State, USA, were analyzed retrospectively to find factors associated with the increase in sex-discordant twins through time. "Low" and "high" fertility treatment groups were defined according to demographic traits. Perinatal mortality was defined as fetal or neonatal death of one or both twins and Weinberg's rule was used to estimate mortality for monozygotic and dizygotic pairs. RESULTS: Controlling simultaneously for maternal age, race, parity, and education did not eliminate the trend of increasing sex-discordant twins from 1992-2004 (M-H chi2 P=0.001). The "low" fertility group had a non-significant decline in sex-discordant twins (M-H chi2 P=0.24), whereas the "high" fertility group had a significant increase (M-H chi2 P=0.001). Perinatal mortality decreased for monozygtic twin pairs throughout the study period, but decreased until the mid-1990s and then increased slightly through 2004 for the dizygotic twin pairs. CONCLUSION: Advancing maternal age and increasing use of fertility treatments are largely responsible for the increase in dizygotic twins from 1980-2004 and may also be responsible for the stalling of the decline in perinatal mortality rate.