Mina, an Il4 repressor, controls T helper type 2 bias.

T helper type 2 (T(H)2) bias, which is the propensity of naive CD4(+) T cells to differentiate into interleukin 4 (IL-4)-secreting T(H)2 cells, is a genetic trait that affects susceptibility to infectious, autoimmune and allergic diseases. T(H)2 bias correlates with the amount of IL-4 initially secreted by newly activated helper T cells that feeds back positively through the pathway of the IL-4 receptor and the transcription factors STAT6 and GATA-3 to drive T(H)2 development. Here we identify Mina, a member of the jumonji C (JmjC) protein family, as a genetic determinant of T(H)2 bias. Mina specifically bound to and repressed the Il4 promoter. Mina overexpression in transgenic mice impaired Il4 expression, whereas its knockdown in primary CD4(+) T cells led to Il4 derepression. Our findings collectively provide mechanistic insight into an Il4-regulatory pathway that controls helper T cell differentiation and genetic variation in T(H)2 bias.

Enhanced susceptibility of Ago1/3 double-null mice to influenza A virus infection.

RNA interference (RNAi) is a critical component of many cellular antiviral responses in plants, invertebrates, and mammals. However, its in vivo role in host protection from the negative-sense RNA virus influenza virus type A (flu) is unclear. Here we have examined the role of RNAi in host defense to flu by analyzing Argonaute 1 and 3 double-knockout mice deficient in components of the RNA-induced silencing complex. Compared to littermate controls, flu-infected double-knockout mice exhibited increased mortality, consistent with more severe alveolitis and pneumonitis. These data indicate that optimal resistance to flu requires Argonaute 1 and/or 3. Enhanced mortality of double-knockout mice was not associated either with increased viral replication or with differential pulmonary recruitment or function of innate and adaptive immune cells. Given the absence of detectable immune defects, our results support the notion that the enhanced flu susceptibility of double-knockout mice arises from an intrinsic impairment in the ability of lung cells to tolerate flu-elicited inflammation.

Supporting the democratization of science during a pandemic: genomics Course-based Undergraduate Research Experiences (CUREs) as an effective remote learning strategy.

The initial phase of the COVID-19 pandemic changed the nature of course delivery from largely in-person to exclusively remote, thus disrupting the well-established pedagogy of the Genomics Education Partnership (GEP; https://www.thegep.org). However, our web-based research adapted well to the remote learning environment. As usual, students who engaged in the GEP's Course-based Undergraduate Research Experience (CURE) received digital projects based on genetic information within assembled Drosophila genomes. Adaptations for remote implementation included moving new member faculty training and peer Teaching Assistant office hours from in-person to online. Surprisingly, our faculty membership significantly increased and, hence, the number of supported students. Furthermore, despite the mostly virtual instruction of the 2020-2021 academic year, there was no significant decline in student learning nor attitudes. Based on successfully expanding the GEP CURE within a virtual learning environment, we provide four strategic lessons we infer toward democratizing science education. First, it appears that increasing access to scientific research and professional development opportunities by supporting virtual, cost-free attendance at national conferences attracts more faculty members to educational initiatives. Second, we observed that transitioning new member training to an online platform removed geographical barriers, reducing time and travel demands, and increased access for diverse faculty to join. Third, developing a Virtual Teaching Assistant program increased the availability of peer support, thereby improving the opportunities for student success. Finally, increasing access to web-based technology is critical for providing equitable opportunities for marginalized students to fully participate in research courses. Online CUREs have great potential for democratizing science education.

Student Attitudes Contribute to the Effectiveness of a Genomics CURE.

The Genomics Education Partnership (GEP) engages students in a course-based undergraduate research experience (CURE). To better understand the student attributes that support success in this CURE, we asked students about their attitudes using previously published scales that measure epistemic beliefs about work and science, interest in science, and grit. We found, in general, that the attitudes students bring with them into the classroom contribute to two outcome measures, namely, learning as assessed by a pre- and postquiz and perceived self-reported benefits. While the GEP CURE produces positive outcomes overall, the students with more positive attitudes toward science, particularly with respect to epistemic beliefs, showed greater gains. The findings indicate the importance of a student's epistemic beliefs to achieving positive learning outcomes.

Apoptosis regulates notochord development in Xenopus.

The notochord is the defining characteristic of the chordate embryo and plays critical roles as a signaling center and as the primitive skeleton. In this study we show that early notochord development in Xenopus embryos is regulated by apoptosis. We find apoptotic cells in the notochord beginning at the neural groove stage and increasing in number as the embryo develops. These dying cells are distributed in an anterior to posterior pattern that is correlated with notochord extension through vacuolization. In axial mesoderm explants, inhibition of this apoptosis causes the length of the notochord to approximately double compared to controls. In embryos, however, inhibition of apoptosis decreases the length of the notochord and it is severely kinked. This kinking also spreads from the anterior with developmental stage such that, by the tadpole stage, the notochord lacks any recognizable structure, although notochord markers are expressed in a normal temporal pattern. Extension of the somites and neural plate mirrors that of the notochord in these embryos, and the somites are severely disorganized. These data indicate that apoptosis is required for normal notochord development during the formation of the anterior-posterior axis, and its role in this process is discussed.

Transcriptional activation of Mina by Sp1/3 factors.

Mina is an epigenetic gene regulatory protein known to function in multiple physiological and pathological contexts, including pulmonary inflammation, cell proliferation, cancer and immunity. We showed previously that the level of Mina gene expression is subject to natural genetic variation linked to 21 SNPs occurring in the Mina 5' region. In order to explore the mechanisms regulating Mina gene expression, we set out to molecularly characterize the Mina promoter in the region encompassing these SNPs. We used three kinds of assays--reporter, gel shift and chromatin immunoprecipitation--to analyze a 2 kb genomic fragment spanning the upstream and intron 1 regions flanking exon 1. Here we discovered a pair of Mina promoters (P1 and P2) and a P1-specific enhancer element (E1). Pharmacologic inhibition and siRNA knockdown experiments suggested that Sp1/3 transcription factors trigger Mina expression through additive activity targeted to a cluster of four Sp1/3 binding sites forming the P1 promoter. These results set the stage for comprehensive analysis of Mina gene regulation from the context of tissue specificity, the impact of inherited genetic variation and the nature of upstream signaling pathways.

Distinct effectors of platelet-derived growth factor receptor-alpha signaling are required for cell survival during embryogenesis.

Platelet-derived growth factor receptor (PDGFR) signaling is essential for normal embryonic development in many organisms, including frog, mouse, zebrafish, and sea urchin. The mode of action of PDGFR signaling during early development is poorly understood, however, mostly because inhibition of signaling through either the PDGFRalpha or PDGFRbeta is embryonic lethal. In Xenopus embryos, disruption of PDGFRalpha signaling causes migrating anterior mesoderm cells to lose direction and undergo apoptosis through the mitochondrial pathway. To understand the mechanism of PDGFRalpha function in this process, we have analyzed all known effector-binding sites in vivo. By using a chemical inducer of dimerization to activate chimera PDGFRalphas, we have identified a role for phospholipase Cgamma (PLCgamma) in protecting cells from death. PDGFRalpha-mediated cell survival requires PLCgamma and phosphatidylinositol 3-kinase signaling, and that PDGFRalpha with binding sites for these two signaling factors is sufficient for this activity. Other effectors of PDGFRalpha signaling, Shf, SHP-2, and Crk, are not required for this process. Thus, our findings show that PDGFRalpha signaling through PLCgamma and phosphatidylinositol 3-kinase has a protective role in preventing apoptosis in early development. Furthermore, we demonstrate that small molecule inducers of dimerization provide a powerful system to manipulate receptor function in developing embryos.

The mitochondrial-apoptotic pathway is triggered in Xenopus mesoderm cells deprived of PDGF receptor signaling during gastrulation.

Platelet-derived growth factor receptor (PDGFR) signaling is required for normal gastrulation in Xenopus laevis. Embryos deprived of PDGFR signaling develop with a range of gastrulation-specific defects including spina bifida, shortened anteroposterior axis, and reduced anterior structures. These defects arise because the involuting mesoderm fails to move appropriately. In this study, we determine that inhibition of PDGFR signaling causes prospective head mesoderm cells to appear in the blastocoel cavity at the onset of gastrulation, stage 10. These aberrant cells undergo apoptosis via the caspase 3 pathway at an embryonic checkpoint called the early gastrula transition (EGT). They are TUNEL-positive and have increased levels of caspase 3 activity compared to control embryos. Apoptotic death of these mesoderm cells can be prevented by co-injection of mRNA encoding Bcl-2 or by injection of either a general caspase inhibitor or a caspase 3-specific inhibitor. Prevention of cell death, however, is not sufficient to rescue gastrulation defects in these embryos. Based on these data, we propose that PDGFR signaling is necessary for survival of prospective head mesoderm cells, and also plays an essential role in the control of their cell movement during gastrulation.