Heterologous Protein Expression in the Xenopus Oocyte

Voltage-clamp fluorometry analysis of structural rearrangements of ATP-gated channel P2X2 upon hyperpolarization

Gating of the ATP-activated channel P2X2 has been shown to be dependent not only on [ATP] but also on membrane voltage, despite the absence of a canonical voltage-sensor domain. We aimed to investigate the structural rearrangements of rat P2X2 during ATP- and voltage-dependent gating, using a voltage-clamp fluorometry technique. We observed fast and linearly voltage-dependent fluorescence intensity (F) changes at Ala337 and Ile341 in the TM2 domain, which could be due to the electrochromic effect, reflecting the presence of a converged electric field. We also observed slow and voltage-dependent F changes at Ala337, which reflect structural rearrangements. Furthermore, we determined that the interaction between Ala337 in TM2 and Phe44 in TM1, which are in close proximity in the ATP-bound open state, is critical for activation. Taking these results together, we propose that the voltage dependence of the interaction within the converged electric field underlies the voltage-dependent gating.

Incidence of Depression and Anxiety in a Cohort of Adolescents With Nonalcoholic Fatty Liver Disease

OBJECTIVES

To determine the incidence of clinically diagnosed depression and anxiety in adolescents with nonalcoholic fatty liver disease (NAFLD).

METHODS

This was a prospective, longitudinal cohort study between January 1, 2012 and July 1, 2018 conducted in a Children's Hospital Pediatric Gastroenterology Clinic. Participants included adolescents 12 to 17 years old at baseline with biopsy-confirmed NAFLD. The primary outcomes were having depression and/or anxiety based upon a clinical diagnosis established by a physician or psychologist. The rates of depression and anxiety were measured at baseline and longitudinally throughout follow-up.

RESULTS

A total of 160 adolescents with NAFLD were followed for a mean of 3.8 years. At baseline, 8.1% had a diagnosis of depression. During follow-up, an additional 9.5% (95% confidence interval, 4.7-14.3) developed depression. The incidence density of depression was 27 new cases per 1000 person-years at risk. In adolescents with NAFLD, 6.3% had anxiety at baseline and 6.7% (95% confidence interval, 2.6-10.7) developed anxiety during follow-up. The incidence density of anxiety was 18 new cases per 1000 person-years at risk. The change in alanine aminotransferase was significantly worse for adolescents with NAFLD who developed depression compared to those who did not develop depression (P < 0.01).

CONCLUSIONS

Adolescents with NAFLD had a high incidence of clinically diagnosed depression and anxiety. The rates were higher than expected relative to the available data in the general population. Addressing this mental health burden will require efforts at both the patient level and the systems level.

Research-Relevant Background Lesions and Conditions in Common Avian and Aquatic Species

Non-mammalian vertebrates including birds, fish, and amphibians have a long history of contributing to ground-breaking scientific discoveries. Because these species offer several experimental advantages over higher vertebrates and share extensive anatomic and genetic homology with their mammalian counterparts, they remain popular animal models in a variety of fields such as developmental biology, physiology, toxicology, drug discovery, immunology, toxicology, and infectious disease. As with all animal models, familiarity with the anatomy, physiology, and spontaneous diseases of these species is necessary for ensuring animal welfare, as well as accurate interpretation and reporting of study findings. Working with avian and aquatic species can be especially challenging in this respect due to their rich diversity and array of unique adaptations. Here, we provide an overview of the research-relevant anatomic features, non-infectious conditions, and infectious diseases that impact research colonies of birds and aquatic animals, including fish and Xenopus species.

Using the Xenopus Oocyte Toolbox

The Xenopus oocyte is a unique model system, allowing both the study of complex biological processes within a cellular context through expression of exogenous mRNAs and proteins, and the study of the cell, molecular, and developmental biology of the oocyte itself. During oogenesis, Xenopus oocytes grow dramatically in size, with a mature oocyte having a diameter of ∼1.3 mm, and become highly polarized, localizing many mRNAs and proteins. Thus, the mature oocyte is a repository of maternal mRNAs and proteins that will direct early embryogenesis prior to zygotic genome transcription. Importantly, the Xenopus oocyte also has the capacity to translate exogenous microinjected RNAs, which has enabled breakthroughs in a wide range of areas including cell biology, developmental biology, molecular biology, and physiology. This introduction outlines how Xenopus oocytes can be used to study a variety of important biological questions.