A system of reporters for comparative investigation of EJC-independent and EJC-enhanced nonsense-mediated mRNA decay

Nonsense-mediated mRNA decay (NMD) is a network of pathways that degrades transcripts that undergo premature translation termination. In mammals, NMD can be divided into the exon junction complex (EJC)-enhanced and EJC-independent branches. Fluorescence- and luminescence-based reporters have long been effective tools to investigate NMD, yet existing reporters largely focus on the EJC-enhanced pathway. Here, we present a system of reporters for comparative studies of EJC-independent and EJC-enhanced NMD. This system also enables the study of NMD-associated outcomes such as premature termination codon (PTC) readthrough and truncated protein degradation. These reporters are compatible with fluorescence or luminescence-based readouts via transient transfection or stable integration. Using this reporter system, we show that EJC-enhanced NMD RNA levels are reduced by 2- or 9-fold and protein levels are reduced by 7- or 12-fold compared to EJC-independent NMD, depending on the reporter gene used. Additionally, the extent of readthrough induced by G418 and an NMD inhibitor (SMG1i), alone and in combination, varies across NMD substrates. When combined, G418 and SMG1i increase readthrough product levels in an additive manner for EJC-independent reporters, while EJC-enhanced reporters show a synergistic effect. We present these reporters as a valuable toolkit to deepen our understanding of NMD and its associated mechanisms.

Uric Acid Is Not Associated With Cardiovascular Health in Youth With Type 1 Diabetes: SEARCH for Diabetes in Youth Study

CONTEXT

Uric acid's role in cardiovascular health in youth with type 1 diabetes is unknown.

OBJECTIVE

Investigate whether higher uric acid is associated with increased blood pressure (BP) and arterial stiffness over time in adolescents and young adults with type 1 diabetes and if overweight/obesity modifies this relationship.

METHODS

Longitudinal analysis of data from adolescents and young adults with type 1 diabetes from 2 visits (mean follow up 4.6 years) in the SEARCH for Diabetes in Youth multicenter prospective cohort study from 2007 to 2018. Our exposure was uric acid at the first visit and our outcome measures were the change in BP, pulse wave velocity (PWV), and augmentation index between visits. We used multivariable linear mixed-effects models and assessed for effect modification by overweight/obesity.

RESULTS

Of 1744 participants, mean age was 17.6 years, 49.4% were female, 75.9% non-Hispanic White, and 45.4% had a follow-up visit. Mean uric acid was 3.7 mg/dL (SD 1.0). Uric acid was not associated with increased BP, PWV-trunk, or augmentation index over time. Uric acid was marginally associated with PWV-upper extremity (β = .02 m/s/year, 95% CI 0.002 to 0.04). The magnitude of this association did not differ by overweight/obesity status.

CONCLUSION

Among adolescents and young adults with type 1 diabetes, uric acid was not consistently associated with increased BP or arterial stiffness over time. These results support findings from clinical trials in older adults with diabetes showing that lowering uric acid levels does not improve cardiovascular outcomes.

Mechanisms of Ovarian Cancer-Associated Cachexia

Cancer-associated cachexia occurs in 50% to 80% of cancer patients and is responsible for 20% to 30% of cancer-related deaths. Cachexia limits survival and treatment outcomes, and is a major contributor to morbidity and mortality during cancer. Ovarian cancer is one of the leading causes of cancer-related deaths in women, and recent studies have begun to highlight the prevalence and clinical impact of cachexia in this population. Here, we review the existing understanding of cachexia pathophysiology and summarize relevant studies assessing ovarian cancer-associated cachexia in clinical and preclinical studies. In clinical studies, there is increased evidence that reduced skeletal muscle mass and quality associate with worse outcomes in subjects with ovarian cancer. Mouse models of ovarian cancer display cachexia, often characterized by muscle and fat wasting alongside inflammation, although they remain underexplored relative to other cachexia-associated cancer types. Certain soluble factors have been identified and successfully targeted in these models, providing novel therapeutic targets for mitigating cachexia during ovarian cancer. However, given the relatively low number of studies, the translational relevance of these findings is yet to be determined and requires more research. Overall, our current understanding of ovarian cancer-associated cachexia is insufficient and this review highlights the need for future research specifically aimed at exploring mechanisms of ovarian cancer-associated cachexia by using unbiased approaches and animal models representative of the clinical landscape of ovarian cancer.

Injectable Hydrogel Guides Neurons Growth with Specific Directionality

Visual disabilities affect more than 250 million people, with 43 million suffering from irreversible blindness. The eyes are an extension of the central nervous system which cannot regenerate. Neural tissue engineering is a potential method to cure the disease. Injectability is a desirable property for tissue engineering scaffolds which can eliminate some surgical procedures and reduce possible complications and health risks. We report the development of the anisotropic structured hydrogel scaffold created by a co-injection of cellulose nanofiber (CNF) solution and co-polypeptide solution. The positively charged poly (L-lysine)-r-poly(L-glutamic acid) with 20 mol% of glutamic acid (PLLGA) is crosslinked with negatively charged CNF while promoting cellular activity from the acid nerve stimulate. We found that CNF easily aligns under shear forces from injection and is able to form hydrogel with an ordered structure. Hydrogel is mechanically strong and able to support, guide, and stimulate neurite growth. The anisotropy of our hydrogel was quantitatively determined in situ by 2D optical microscopy and 3D X-ray tomography. The effects of PLLGA:CNF blend ratios on cell viability, neurite growth, and neuronal signaling are systematically investigated in this study. We determined the optimal blend composition for stimulating directional neurite growth yielded a 16% increase in length compared with control, reaching anisotropy of 30.30% at 10°/57.58% at 30°. Using measurements of calcium signaling in vitro, we found a 2.45-fold increase vs. control. Based on our results, we conclude this novel material and unique injection method has a high potential for application in neural tissue engineering.

High Sox2 expression predicts taste lineage competency of lingual progenitors in vitro

Taste buds on the tongue contain taste receptor cells (TRCs) that detect sweet, sour, salty, umami and bitter stimuli. Like non-taste lingual epithelium, TRCs are renewed from basal keratinocytes, many of which express the transcription factor SOX2. Genetic lineage tracing has shown that SOX2+ lingual progenitors give rise to both taste and non-taste lingual epithelium in the posterior circumvallate taste papilla (CVP) of mice. However, SOX2 is variably expressed among CVP epithelial cells, suggesting that their progenitor potential may vary. Using transcriptome analysis and organoid technology, we show that cells expressing SOX2 at higher levels are taste-competent progenitors that give rise to organoids comprising both TRCs and lingual epithelium. Conversely, organoids derived from progenitors that express SOX2 at lower levels are composed entirely of non-taste cells. Hedgehog and WNT/β-catenin are required for taste homeostasis in adult mice. However, manipulation of hedgehog signaling in organoids has no impact on TRC differentiation or progenitor proliferation. By contrast, WNT/β-catenin promotes TRC differentiation in vitro in organoids derived from higher but not low SOX2+ expressing progenitors.

Breast cancers co-opt normal mechanisms of tolerance to promote immune evasion and metastasis

Normal developmental processes, such as those seen during embryonic development and postpartum mammary gland involution, can be reactivated by cancer cells to promote immune suppression, tumor growth, and metastatic spread. In mammalian embryos, paternal-derived antigens are at risk of being recognized as foreign by the maternal immune system. Suppression of the maternal immune response toward the fetus, which is mediated in part by the trophoblast, is critical to ensure embryonic survival and development. The postpartum mammary microenvironment also exhibits immunosuppressive mechanisms accompanying the massive cell death and tissue remodeling that occurs during mammary gland involution. These normal immunosuppressive mechanisms are paralleled during malignant transformation, where tumors can develop neoantigens that may be recognized as foreign by the immune system. To circumvent this, tumors can dedifferentiate and co-opt immune-suppressive mechanisms normally utilized during fetal tolerance and postpartum mammary involution. In this review, we discuss those similarities and how they can inform our understanding of cancer progression and metastasis.

Infant and Toddler Consumption of Sweetened and Unsweetened Lipid Nutrient Supplements After 2-Week Home Repeated Exposures

BACKGROUND

Small-quantity lipid-based nutrient supplements (SQ-LNS) are designed to address undernutrition during the complementary feeding period. SQ-LNS contains added sugars, but limited research has assessed whether infants' acceptance varies between versions with and without sugars.

OBJECTIVES

Our objective was to examine the effects of repeated exposure on children's acceptance of sweetened and unsweetened SQ-LNS. We aimed to understand caregivers' perceptions of children's liking of the 2 SQ-LNS versions and their influences on infant acceptance of SQ-LNS.

METHODS

Caregivers (86% non-Hispanic White) and children (7-24 mo), participated in a randomized, 2-week home-exposure study and baseline and post-home exposure assessments. Children were randomized to receive sweetened or unsweetened SQ-LNS versions, mixed with infant oatmeal. At in-person visits, caregivers fed both SQ-LNS versions to children and rated their child's liking for each. Caregivers fed the SQ-LNS version to which their child was randomized until the child refused to eat more. Acceptance was measured as total grams consumed. Mixed-effects linear models tested the change in SQ-LNS consumed between baseline and postexposure by the SQ-LNS version and number of home exposures. Covariates included the amount of SQ-LNS consumed at baseline, child BMI z-score, child age, and breastfeeding experience.

RESULTS

Children's acceptance of both SQ-LNS versions increased from baseline to postexposure (β, 0.71 g; 95% CI: 0.54-0.89 g; P = 0.04), regardless of SQ-LNS version (P = 0.88) or number of home exposures (P = 0.55). Caregivers rated children's liking of unsweetened SQ-LNS higher at baseline (P = 0.02). Children with lower liking ratings at baseline showed the greatest increases in acceptance between baseline and postexposure (P = 0.01).

CONCLUSIONS

Children's acceptance of SQ-LNS increased with repeated exposure, whether offered the sweetened or unsweetened version, providing preliminary support that adding sugar to SQ-LNS may not improve acceptance in young children. Children who initially like the supplement less may need repeated experience to learn to accept SQ-LNS. This trial was registered at clinicaltrials.gov as NCT04544332.