Heat-shock mediated overexpression of HNF1β mutations has differential effects on gene expression in the Xenopus pronephric kidney.

The transcription factor HNF1B, encoded by the TCF2 gene, plays an important role in the organogenesis of vertebrates. In humans, heterozygous mutations of HNF1B are associated with several diseases, such as pancreatic β-cell dysfunction leading to maturity-onset diabetes of the young (MODY5), defective kidney development, disturbed liver function, pancreas atrophy, and malformations of the genital tract. The African claw frog Xenopus laevis is an excellent model to study the processes involved in embryogenesis and organogenesis, as it can be manipulated easily with a series of methods. In the present study, we overexpressed HNF1β mutants in the developing Xenopus embryo to assess their roles during organogenesis, particularly in the developing pronephric kidney. Towards this goal, we developed a heat-shock inducible binary Cre/loxP system with activator and effector strains. Heat-shock activation of the mutant HNF1B variants P328L329del and A263insGG resulted in malformations of various organs and the affected larvae developed large edemas. Defects in the pronephros were primarily confined to malformed proximal tubules. Furthermore, the expression of the proximal tubule marker genes tmem27 and slc3a1, both involved in amino acid transport, was affected. Both P328L329del and A263insGG downregulated expression of slc3a1. In addition, P328L329del reduced tmem27 expression while A263insGG overexpression decreased expression of the chloride channel clcnk and the transcription factor pax2. Overexpression of two mutant HNF1B derivatives resulted in distinct phenotypes reflected by either a reduction or an enlargement of pronephros size. The expression of selected pronephric marker genes was differentially affected upon overexpression of HNF1B mutations. Based on our findings, we postulate that HNF1B mutations influence gene regulation upon overexpression in specific and distinct manners. Furthermore, our study demonstrates that the newly established Cre/loxP system for Xenopus embryos is an attractive alternative to examine the gene regulatory potential of transcription factors in developing pronephric kidney as exemplified here for HNF1B

Gene expression analysis defines the proximal tubule as the compartment for endocytic receptor-mediated uptake in the Xenopus pronephric kidney

Endocytic receptors in the proximal tubule of the mammalian kidney are responsible for the reuptake of numerous ligands, including lipoproteins, sterols, vitamin-binding proteins, and hormones, and they can mediate drug-induced nephrotoxicity. In this paper, we report the first evidence indicating that the pronephric kidneys of Xenopus tadpoles are capable of endocytic transport. We establish that the Xenopus genome harbors genes for the known three endocytic receptors megalin/LRP2, cubilin, and amnionless. The Xenopus endocytic receptor genes share extensive synteny with their mammalian counterparts. In situ hybridizations demonstrated that endocytic receptor expression is highly tissue specific, primarily in the pronephric kidney, and did not occur prior to neurulation. Expression was strictly confined to proximal tubules of the pronephric kidney, which closely resembles the situation reported in mammalian kidneys. By immunohistochemistry, we demonstrated that Xenopus pronephric tubule epithelia express high amounts of the endocytic receptors megalin/lrp2 and cubilin in the apical plasma membrane. Furthermore, functional aspects of the endocytic receptors were revealed by the vesicular localization of retinol-binding protein in the proximal tubules, probably representing endocytosed protein. In summary, we provide here the first comprehensive report of endocytic receptor expression, including amnionless, in a nonmammalian species. Remarkably, renal endocytic receptor expression and function in the Xenopus pronephric kidney closely mirrors the situation in the mammalian kidney. The Xenopus pronephric kidney therefore represents a novel, simple model for physiological studies on the molecular mechanisms underlying renal tubular endocytosi

Organization of the pronephric kidney revealed by large-scale gene expression mapping

Gene expression mapping reveals 8 functionally distinct domains in the Xenopus pronephros. Interestingly, no structure equivalent to the mammalian collecting duct is identified

SAPALDIA: Methods and participation in the cross-sectional part of the Swiss Study on Air Pollution and Lung Diseases in Adults

Summary: SAPALDIA-the Swiss Study on Air Pollution and Lung Diseases in Adults-focuses on the long term health effects of low to moderate levels of air pollutants as typically seen in different parts of Switzerland. The aim of the SAPALDIA cross-sectional study carried out in 1991 was to determine the prevalence of bronchial asthma, chronic bronchitis and allergic conditions in the adult population of Switzerland and to identify and to determine the respective importance of potentially influencing factors. These could be both personal (smoking habits, allergy status, family history, occupation) and environmental (outdoor and indoor pollution, aeroallergens, climate). A further aim of the cross-sectional study consisted in the identification of individuals susceptible to present symptoms during a two year observation period and to be included in the SAPALDIA follow-up study. This technical report represents the methodological documentation for the cross-sectional study of SAPALDIA. The instruments and the methods of standardisation are presented and discussed. The medical examination consisted of a computerised interview using a standardised questionnaire, the taking of a blood sample for serological tests, allergy skin testing, the measurement of endexpiratory CO and body height, and pulmonary function testing followed by methacholine challenge testing or bronchodilatation testing. The pattern of participation and the 9651 participants of the study, representing 59.3% of the sample, are described. Based on information on non-participants gained by telephone interviews and mailed short questionnaires, possible selection biases are quantified and discusse

VISIONS:the VISTA Star Formation Atlas I. Survey overview

VISIONS is an ESO public survey of five nearby (d < 500 pc) star-forming molecular cloud complexes that are canonically associated with the constellations of Chamaeleon, Corona Australis, Lupus, Ophiuchus, and Orion. The survey was carried out with the Visible and Infrared Survey Telescope for Astronomy (VISTA), using the VISTA Infrared Camera (VIRCAM), and collected data in the near-infrared passbands J (1.25 μm), H (1.65 μm), and KS (2.15 μm). With a total on-sky exposure time of 49.4h VISIONS covers an area of 650 deg2, it is designed to build an infrared legacy archive with a structure and content similar to the Two Micron All Sky Survey (2MASS) for the screened star-forming regions. Taking place between April 2017 and March 2022, the observations yielded approximately 1.15 million images, which comprise 19 TB of raw data. The observations undertaken within the survey are grouped into three different subsurveys. First, the wide subsurvey comprises shallow, large-scale observations and it has revisited the star-forming complexes six times over the course of its execution. Second, the deep subsurvey of dedicated high-sensitivity observations has collected data on areas with the largest amounts of dust extinction. Third, the control subsurvey includes observations of areas of low-to-negligible dust extinction. Using this strategy, the VISIONS observation program offers multi-epoch position measurements, with the ability to access deeply embedded objects, and it provides a baseline for statistical comparisons and sample completeness – all at the same time. In particular, VISIONS is designed to measure the proper motions of point sources, with a precision of 1 mas yr−1 or better, when complemented with data from the VISTA Hemisphere Survey (VHS). In this way, VISIONS can provide proper motions of complete ensembles of embedded and low-mass objects, including sources inaccessible to the optical ESA Gaia mission. VISIONS will enable the community to address a variety of research topics from a more informed perspective, including the 3D distribution and motion of embedded stars and the nearby interstellar medium, the identification and characterization of young stellar objects, the formation and evolution of embedded stellar clusters and their initial mass function, as well as the characteristics of interstellar dust and the reddening law

VISIONS: The VISTA Star Formation Atlas -- I. Survey overview

© The Authors 2023. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0).VISIONS is an ESO public survey of five nearby (d < 500 pc) star-forming molecular cloud complexes that are canonically associated with the constellations of Chamaeleon, Corona Australis, Lupus, Ophiuchus, and Orion. The survey was carried out with VISTA, using VIRCAM, and collected data in the near-infrared passbands J, H, and Ks. With a total on-sky exposure time of 49.4 h VISIONS covers an area of 650 deg$^2$, and it was designed to build an infrared legacy archive similar to that of 2MASS. Taking place between April 2017 and March 2022, the observations yielded approximately 1.15 million images, which comprise 19 TB of raw data. The observations are grouped into three different subsurveys: The wide subsurvey comprises shallow, large-scale observations and has visited the star-forming complexes six times over the course of its execution. The deep subsurvey of dedicated high-sensitivity observations has collected data on the areas with the largest amounts of dust extinction. The control subsurvey includes observations of areas of low-to-negligible dust extinction. Using this strategy, the VISIONS survey offers multi-epoch position measurements, is able to access deeply embedded objects, and provides a baseline for statistical comparisons and sample completeness. In particular, VISIONS is designed to measure the proper motions of point sources with a precision of 1 mas/yr or better, when complemented with data from VHS. Hence, VISIONS can provide proper motions for sources inaccessible to Gaia. VISIONS will enable addressing a range of topics, including the 3D distribution and motion of embedded stars and the nearby interstellar medium, the identification and characterization of young stellar objects, the formation and evolution of embedded stellar clusters and their initial mass function, as well as the characteristics of interstellar dust and the reddening law.Peer reviewe

Prospects for the Xenopus Embryo Model in Therapeutics Technologies

Access to suitable animal models is essential in the field of therapeutics technologies. Recently, lower vertebrates have emerged as attractive low-cost animal models which offer new exciting applications in functional genomics and therapeutics technologies. Amphibian embryos of the genus Xenopus have long served as important models for the study of vertebrate development. Xenopus is evolutionary significantly less distant to humans than fish models, which suggests that experimental findings gained with Xenopus will more accurately predict human biology. Numerous experimental advantages, including external development, large size, identifiable blastomeres, and their ability to withstand extensive surgical intervention and culture in vitro, have favored the use of the Xenopus model in the past. More recently, the introduction of a simple efficient method to disrupt gene functions and the rapid development of genomic resources has further increased the attractiveness of this low-cost, high-throughput model for the analysis of vertebrate gene functions. Using the Xenopus embryo as the primary animal model, our research in the field of therapeutics technologies has focused on the identification and validation of novel drug targets by employing genomic and transcriptomic information in the analysis of the molecular and cellular processes underlying kidney organogenesis and vascular development. Furthermore, our research on signaling pathways controlling cellular differentiation of embryonic tissues provides important insights that may ultimately lead to the development of novel cell-based therapies in regenerative medicine. Finally, we are exploring the possibility of employing the Xenopus embryos in chemical library screens to identify novel chemical modulators of organogenesis

A Role for All-Trans-Retinoic Acid in the Early Steps of Lymphatic Vasculature Development

The molecular mechanisms that regulate the earliest steps of lymphatic vascular system development are unknown. To identify regulators of lymphatic competence and commitment, we used an in vitro vascular assay with mouse embryonic stem cell-derived embryoid bodies (EBs). We found that incubation with retinoic acid (RA) and, more potently, with RA in combination with cAMP, induced the expression of the lymphatic competence marker LYVE-1 in the vascular structures of the EBs. This effect was dependent on RA receptor (RAR)-α and protein kinase A signaling. RA-cAMP incubation also promoted the development of CD31+/LYVE-1+/Prox1+ cell clusters. In situ studies revealed that RAR-α is expressed by endothelial cells of the cardinal vein in ED 9.5–11.5 mouse embryos. Timed exposure of mouse and Xenopus embryos to excess of RA upregulated LYVE-1 and VEGFR-3 on embryonic veins and increased formation of Prox1-positive lymphatic progenitors. These findings indicate that RA signaling mediates the earliest steps of lymphatic vasculature development

The prepattern transcription factor Irx3 directs nephron segment identity

The nephron, the basic structural and functional unit of the vertebrate kidney, is organized into discrete segments, which are composed of distinct renal epithelial cell types. Each cell type carries out highly specific physiological functions to regulate fluid balance, osmolarity, and metabolic waste excretion. To date, the genetic basis of regionalization of the nephron has remained largely unknown. Here we show that Irx3, a member of the Iroquois (Irx) gene family, acts as a master regulator of intermediate tubule fate. Comparative studies in Xenopus and mouse have identified Irx1, Irx2, and Irx3 as an evolutionary conserved subset of Irx genes, whose expression represents the earliest manifestation of intermediate compartment patterning in the developing vertebrate nephron discovered to date. Intermediate tubule progenitors will give rise to epithelia of Henle’s loop in mammals. Loss-of-function studies indicate that irx1 and irx2 are dispensable, whereas irx3 is necessary for intermediate tubule formation in Xenopus. Furthermore, we demonstrate that misexpression of irx3 is sufficient to direct ectopic development of intermediate tubules in the Xenopus mesoderm. Taken together, irx3 is the first gene known to be necessary and sufficient to specify nephron segment fate in vivo

Gene expression analysis defines the proximal tubule as the compartment for endocytic receptor-mediated uptake in the Xenopus pronephric kidney

ISSN:0031-6768ISSN:1432-201