A comparative study of cellular diversity between the Xenopus pronephric and mouse metanephric nephron.

The kidney is an essential organ that ensures bodily fluid homeostasis and removes soluble waste products from the organism. Nephrons, the functional units of the kidney, comprise a blood filter, the glomerulus or glomus, and an epithelial tubule that processes the filtrate from the blood or coelom and selectively reabsorbs solutes, such as sugars, proteins, ions, and water, leaving waste products to be eliminated in the urine. Genes coding for transporters are segmentally expressed, enabling the nephron to sequentially process the filtrate. The Xenopus embryonic kidney, the pronephros, which consists of a single large nephron, has served as a valuable model to identify genes involved in nephron formation and patterning. Therefore, the developmental patterning program that generates these segments is of great interest. Prior work has defined the gene expression profiles of Xenopus nephron segments via in situ hybridization strategies, but a comprehensive understanding of the cellular makeup of the pronephric kidney remains incomplete. Here, we carried out single-cell mRNA sequencing of the functional Xenopus pronephric nephron and evaluated its cellular composition through comparative analyses with previous Xenopus studies and single-cell mRNA sequencing of the adult mouse kidney. This study reconstructs the cellular makeup of the pronephric kidney and identifies conserved cells, segments, and associated gene expression profiles. Thus, our data highlight significant conservation in podocytes, proximal and distal tubule cells, and divergence in cellular composition underlying the capacity of each nephron to remove wastes in the form of urine, while emphasizing the Xenopus pronephros as a model for physiology and disease.

Aquatic models of human ciliary diseases.

Cilia are microtubule-based structures that either transmit information into the cell or move fluid outside of the cell. There are many human diseases that arise from malfunctioning cilia. Although mammalian models provide vital insights into the underlying pathology of these diseases, aquatic organisms such as Xenopus and zebrafish provide valuable tools to help screen and dissect out the underlying causes of these diseases. In this review we focus on recent studies that identify or describe different types of human ciliopathies and outline how aquatic organisms have aided our understanding of these diseases.

Zinc transporters belonging to the Cation Diffusion Facilitator (CDF) family have complementary roles in transporting zinc out of the cytosol.

Zinc is an essential trace element that is required for the function of a large number of proteins. As these zinc-binding proteins are found within the cytosol and organelles, all eukaryotes require mechanisms to ensure that zinc is delivered to organelles, even under conditions of zinc deficiency. Although many zinc transporters belonging to the Cation Diffusion Facilitator (CDF) families have well characterized roles in transporting zinc into the lumens of intracellular compartments, relatively little is known about the mechanisms that maintain organelle zinc homeostasis. The fission yeast Schizosaccharomyces pombe is a useful model system to study organelle zinc homeostasis as it expresses three CDF family members that transport zinc out of the cytosol into intracellular compartments: Zhf1, Cis4, and Zrg17. Zhf1 transports zinc into the endoplasmic reticulum, and Cis4 and Zrg17 form a heterodimeric complex that transports zinc into the cis-Golgi. Here we have used the high and low affinity ZapCY zinc-responsive FRET sensors to examine cytosolic zinc levels in yeast mutants that lack each of these CDF proteins. We find that deletion of cis4 or zrg17 leads to higher levels of zinc accumulating in the cytosol under conditions of zinc deficiency, whereas deletion of zhf1 results in zinc accumulating in the cytosol when zinc is not limiting. We also show that the expression of cis4, zrg17, and zhf1 is independent of cellular zinc status. Taken together our results suggest that the Cis4/Zrg17 complex is necessary for zinc transport out of the cytosol under conditions of zinc-deficiency, while Zhf1 plays the dominant role in removing zinc from the cytosol when labile zinc is present. We propose that the properties and/or activities of individual CDF family members are fine-tuned to enable cells to control the flux of zinc out of the cytosol over a broad range of environmental zinc stress.

Examining Risk Factors of Health-Related Quality of Life Impairments Among Adolescents with Inflammatory Bowel Disease.

Inflammatory Bowel Disease (IBD) is a chronic, costly, and burdensome disease that is typically diagnosed during adolescence. Despite the use of effective treatments, rates of relapse and intestinal inflammation remain high and put patients at risk for long term physical and psychosocial health complications. Given the costs associated with IBD, it is critical to examine potential risk factors of poor health-related quality of life (HRQoL) among patients for the enhancement and further development of interventions. As such, the aim of the current study was to examine how sociodemographic and disease characteristics, psychosocial problems, and adherence behaviors impact HRQoL among a sample of youth with IBD. 107 adolescents with IBD and their caregiver completed self- and parent-report measures as part of a psychosocial screening service. Medical records were reviewed to obtain information regarding diagnosis, insurance, medication use, illness severity, and disease activity. Results revealed lower HRQoL scores among adolescents with more psychosocial problems (Est. = -3.08; p < .001), greater disease severity (Est. = -.40; p = .001), and those who identified as Black (Est. = -.38; p < .05). Greater disease severity (Est. = .13 p = .004), use of nonpublic insurance (Est. = .32 p = .004), and fewer psychosocial problems (Est. = -.13 p = .04) were associated with greater adherence behaviors. These findings suggest that implementing individually tailored, evidence-based psychological interventions focused on coping with psychosocial problems and symptoms may be important in enhancing adherence behaviors and HRQoL among adolescents with IBD.

Correction: DYRK1A-related intellectual disability: a syndrome associated with congenital anomalies of the kidney and urinary tract.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

DYRK1A-related intellectual disability: a syndrome associated with congenital anomalies of the kidney and urinary tract.

PURPOSE: Haploinsufficiency of DYRK1A causes a recognizable clinical syndrome. The goal of this paper is to investigate congenital anomalies of the kidney and urinary tract (CAKUT) and genital defects (GD) in patients with DYRK1A variants. METHODS: A large database of clinical exome sequencing (ES) was queried for de novo DYRK1A variants and CAKUT/GD phenotypes were characterized. Xenopus laevis (frog) was chosen as a model organism to assess Dyrk1a's role in renal development. RESULTS: Phenotypic details and variants of 19 patients were compiled after an initial observation that one patient with a de novo pathogenic variant in DYRK1A had GD. CAKUT/GD data were available from 15 patients, 11 of whom presented with CAKUT/GD. Studies in Xenopus embryos demonstrated that knockdown of Dyrk1a, which is expressed in forming nephrons, disrupts the development of segments of embryonic nephrons, which ultimately give rise to the entire genitourinary (GU) tract. These defects could be rescued by coinjecting wild-type human DYRK1A RNA, but not with DYRK1AR205* or DYRK1AL245R RNA. CONCLUSION: Evidence supports routine GU screening of all individuals with de novo DYRK1A pathogenic variants to ensure optimized clinical management. Collectively, the reported clinical data and loss-of-function studies in Xenopus substantiate a novel role for DYRK1A in GU development.

The gluconate shunt is an alternative route for directing glucose into the pentose phosphate pathway in fission yeast.

Glycolysis and the pentose phosphate pathway both play a central role in the degradation of glucose in all domains of life. Another metabolic route that can facilitate glucose breakdown is the gluconate shunt. In this shunt glucose dehydrogenase and gluconate kinase catalyze the two-step conversion of glucose into the pentose phosphate pathway intermediate 6-phosphogluconate. Despite the presence of these enzymes in many organisms, their only established role is in the production of 6-phosphogluconate for the Entner-Doudoroff pathway. In this report we performed metabolic profiling on a strain of Schizosaccharomyces pombe lacking the zinc-responsive transcriptional repressor Loz1 with the goal of identifying metabolic pathways that were altered by cellular zinc status. This profiling revealed that loz1Δ cells accumulate higher levels of gluconate. We show that the altered gluconate levels in loz1Δ cells result from increased expression of gcd1 By analyzing the activity of recombinant Gcd1 in vitro and by measuring gluconate levels in strains lacking enzymes of the gluconate shunt we demonstrate that Gcd1 encodes a novel NADP+-dependent glucose dehydrogenase that acts in a pathway with the Idn1 gluconate kinase. We also find that cells lacking gcd1 and zwf1, which encode the first enzyme in the pentose phosphate pathway, have a more severe growth phenotype than cells lacking zwf1 We propose that in S. pombe Gcd1 and Idn1 act together to shunt glucose into the pentose phosphate pathway, creating an alternative route for directing glucose into the pentose phosphate pathway that bypasses hexokinase and the rate-limiting enzyme glucose-6-phosphate dehydrogenase.

Outcomes from a 12-Week, Open-Label, Multicenter Clinical Trial of Teduglutide in Pediatric Short Bowel Syndrome.

OBJECTIVE: To determine safety and pharmacodynamics/efficacy of teduglutide in children with intestinal failure associated with short bowel syndrome (SBS-IF). STUDY DESIGN: This 12-week, open-label study enrolled patients aged 1-17 years with SBS-IF who required parenteral nutrition (PN) and showed minimal or no advance in enteral nutrition (EN) feeds. Patients enrolled sequentially into 3 teduglutide cohorts (0.0125 mg/kg/d [n = 8], 0.025 mg/kg/d [n = 14], 0.05 mg/kg/d [n = 15]) or received standard of care (SOC, n = 5). Descriptive summary statistics were used. RESULTS: All patients experienced ≥1 treatment-emergent adverse event; most were mild or moderate. No serious teduglutide-related treatment-emergent adverse events occurred. Between baseline and week 12, prescribed PN volume and calories (kcal/kg/d) changed by a median of -41% and -45%, respectively, with 0.025 mg/kg/d teduglutide and by -25% and -52% with 0.05 mg/kg/d teduglutide. In contrast, PN volume and calories changed by 0% and -6%, respectively, with 0.0125 mg/kg/d teduglutide and by 0% and -1% with SOC. Per patient diary data, EN volume increased by a median of 22%, 32%, and 40% in the 0.0125, 0.025, and 0.05 mg/kg/d cohorts, respectively, and by 11% with SOC. Four patients achieved independence from PN, 3 in the 0.05 mg/kg/d cohort and 1 in the 0.025 mg/kg/d cohort. Study limitations included its short-term, open-label design, and small sample size. CONCLUSIONS: Teduglutide was well tolerated in pediatric patients with SBS-IF. Teduglutide 0.025 or 0.05 mg/kg/d was associated with trends toward reductions in PN requirements and advancements in EN feeding in children with SBS-IF. TRIAL REGISTRATION: ClinicalTrials.gov:NCT01952080; EudraCT: 2013-004588-30.

Zinc finger protein Loz1 is required for zinc-responsive regulation of gene expression in fission yeast.

In Schizosaccharomyces pombe, alcohol dehydrogenase 1 (Adh1) is an abundant zinc-requiring enzyme that catalyses the conversion of acetaldehyde to ethanol during fermentation. In a zinc-replete cell, adh1 is highly expressed. However, in zinc-limited cells, adh1 gene expression is repressed, and cells induce the expression of an alternative alcohol dehydrogenase encoded by the adh4 gene. In our studies examining this zinc-dependent switch in alcohol dehydrogenase gene expression, we isolated an adh1Δ strain containing a partial loss of function mutation that resulted in higher levels of adh4 transcripts in zinc-replete cells. This mutation also led to the aberrant expression of other genes that are typically regulated by zinc. Using linkage analysis, we have mapped the position of this mutation to a single gene called Loss Of Zinc sensing 1 (loz1). Loz1 is a 55-kDa protein that contains a double C2H2-type zinc finger domain. The mapped mutation that disrupts Loz1 function leads to an arginine to glycine substitution in the second zinc finger domain, suggesting that the double zinc finger domain is important for Loz1 function. We show that loz1Δ cells hyperaccumulate zinc and that Loz1 is required for gene repression in zinc-replete cells. We also have found that Loz1 negatively autoregulates its own expression. We propose that Loz1 is a unique metalloregulatory factor that plays a central role in zinc homeostasis in S. pombe.

The double zinc finger domain and adjacent accessory domain from the transcription factor loss of zinc sensing 1 (loz1) are necessary for DNA binding and zinc sensing.

The Loz1 transcription factor from Schizosaccharomyces pombe plays an essential role in zinc homeostasis by repressing target gene expression in zinc-replete cells. To determine how Loz1 function is regulated by zinc, we employed a genetic screen to isolate mutants with impaired zinc-dependent gene expression and analyzed Loz1 protein truncations to map a minimal zinc-responsive domain. In the screen, we isolated 36 new loz1 alleles. 27 of these alleles contained mutations resulting in the truncation of the Loz1 protein. The remaining nine alleles contained point mutations leading to an amino acid substitution within a C-terminal double zinc finger domain. Further analysis of two of these substitutions revealed that they disrupted Loz1 DNA activity in vitro. By analyzing Loz1 protein truncations, we found that the last 96 amino acids of Loz1 was the smallest region that was able to confer partial zinc-dependent repression in vivo. This 96-amino acid region contains the double zinc finger domain and an accessory domain that enhances DNA binding. These results were further supported by the findings that MtfA, a transcription factor from Aspergillus nidulans that contains a related double zinc finger, is unable to complement loz1Δ, whereas a chimera of MtfA containing the Loz1 accessory domain is able to complement loz1Δ. Together, our studies indicate that the double zinc finger domain and adjacent accessory domain preceding zinc finger 1 are necessary for DNA binding and zinc-dependent repression.

Zinc-dependent regulation of the Adh1 antisense transcript in fission yeast.

In yeast, Adh1 (alcohol dehydrogenase 1) is an abundant zinc-binding protein that is required for the conversion of acetaldehyde to ethanol. Through transcriptome profiling of the Schizosaccharomyces pombe genome, we identified a natural antisense transcript at the adh1 locus that is induced in response to zinc limitation. This antisense transcript (adh1AS) shows a reciprocal expression pattern to that of the adh1 mRNA partner. In this study, we show that increased expression of the adh1AS transcript in zinc-limited cells is necessary for the repression of adh1 gene expression and that the increased level of the adh1AS transcript in zinc-limited cells is a result of two mechanisms. At the transcriptional level, the adh1AS transcript is expressed at a high level in zinc-limited cells. In addition to this transcriptional control, adh1AS transcripts preferentially accumulate in zinc-limited cells when the adh1AS transcript is expressed from a constitutive promoter. This secondary mechanism requires the simultaneous expression of adh1. Our studies reveal how multiple mechanisms can synergistically control the ratio of sense to antisense transcripts and highlight a novel mechanism by which adh1 gene expression can be controlled by cellular zinc availability.

Cause or effect? Undetectable vitamin D in a patient with Crohn's disease.

Crohn's disease has been described as the "great mimicker" with a wide array of presentations. We describe a case of a teenager who presented with tetany and undetectable vitamin D as initial presentation of Crohn's disease. There are reports of adults in tetany due to electrolyte derangements in chronic gastrointestinal diseases secondary to malabsorption. However, the role of deficient vitamin D as it contributes to immune system dysfunction has only begun to be explored. Vitamin D is essential for calcium absorption, immune regulation, and gut epithelial barrier. This case report discusses vitamin D physiology and its potential mediation in the pathogenesis of inflammatory bowel disease.

Tissue-Targeted CRISPR-Cas9-Mediated Genome Editing of Multiple Homeologs in F0-Generation Xenopus laevis Embryos.

Xenopus laevis frogs are a powerful developmental model that enables studies combining classical embryology and molecular manipulation. Because of the large embryo size, ease of microinjection, and ability to target tissues through established fate maps, X. laevis has become the predominant amphibian research model. Given that their allotetraploid genome has complicated the generation of gene knockouts, strategies need to be established for efficient mutagenesis of multiple homeologs to evaluate gene function. Here we describe a protocol to use CRISPR-Cas9-mediated genome editing to target either single alleles or multiple alloalleles in F0 X. laevis embryos. A single-guide RNA (sgRNA) is designed to target a specific DNA sequence encoding a critical protein domain. To mutagenize a gene with two alloalleles, the sgRNA is designed against a sequence that is common to both homeologs. This sgRNA, along with the Cas9 protein, is microinjected into the zygote to disrupt the genomic sequences in the whole embryo or into a specific blastomere for tissue-targeted effects. Error-prone repair of CRISPR-Cas9-generated DNA double-strand breaks leads to insertions and deletions creating mosaic gene lesions within the embryos. The genomic DNA isolated from each mosaic F0 embryo is sequenced, and software is applied to assess the nature of the mutations generated and degree of mosaicism. This protocol enables the knockout of genes within the whole embryo or in specific tissues in F0 X. laevis embryos to facilitate the evaluation of resulting phenotypes.

Copper metabolism and pediatric cholestasis.

PURPOSE OF REVIEW: Copper is an essential trace mineral but both deficiency and toxicity need to be avoided. Copper is regulated via excretion by the biliary system and caution was recommended when administered in patients with cholestasis. Recent clinical reports indicate that despite the cholestasis, copper should not be withheld from parenteral nutrition. RECENT FINDINGS: Transporters involved in regulating copper levels have been identified. This explains the processes that regulate copper levels and the diseases that result from transporter defects. Monitoring copper ideally requires a liver biopsy but there are reports that in infants serum copper levels correlate with the liver copper. The published cautions about copper in cholestatic patients on parenteral nutrition led to the removal of copper from the solutions. Subsequently, multiple reports of clinical copper deficiency developing in these patients including infants were published. Newer literature indicates no elevation in infant copper levels despite normal copper parenteral nutrition supplementation in the presence of cholestasis. SUMMARY: Copper is essential and levels are regulated in response to an individual's needs. The liver excretion of copper is the primary regulating method but clinically cholestasis does not result in elevated levels in infants. The best clinical approach to parenteral nutrition copper is careful monitoring even in the presence of cholestasis.

OSM-11 facilitates LIN-12 Notch signaling during Caenorhabditis elegans vulval development.

Notch signaling is critical for cell fate decisions during development. Caenorhabditis elegans and vertebrate Notch ligands are more diverse than classical Drosophila Notch ligands, suggesting possible functional complexities. Here, we describe a developmental role in Notch signaling for OSM-11, which has been previously implicated in defecation and osmotic resistance in C. elegans. We find that complete loss of OSM-11 causes defects in vulval precursor cell (VPC) fate specification during vulval development consistent with decreased Notch signaling. OSM-11 is a secreted, diffusible protein that, like previously described C. elegans Delta, Serrate, and LAG-2 (DSL) ligands, can interact with the lineage defective-12 (LIN-12) Notch receptor extracellular domain. Additionally, OSM-11 and similar C. elegans proteins share a common motif with Notch ligands from other species in a sequence defined here as the Delta and OSM-11 (DOS) motif. osm-11 loss-of-function defects in vulval development are exacerbated by loss of other DOS-motif genes or by loss of the Notch ligand DSL-1, suggesting that DOS-motif and DSL proteins act together to activate Notch signaling in vivo. The mammalian DOS-motif protein Deltalike1 (DLK1) can substitute for OSM-11 in C. elegans development, suggesting that DOS-motif function is conserved across species. We hypothesize that C. elegans OSM-11 and homologous proteins act as coactivators for Notch receptors, allowing precise regulation of Notch receptor signaling in developmental programs in both vertebrates and invertebrates.

Exploring potential noninvasive biomarkers in eosinophilic esophagitis in children.

BACKGROUND AND AIMS: Eosinophilic esophagitis (EE) continues to present clinical challenges, including a need for noninvasive tools to manage the disease. To identify a marker able to assess disease status in lieu of repeated endoscopies, we examined 3 noninvasive biomarkers, serum interleukin (IL)-5, serum eosinophil-derived neurotoxin (EDN), and stool EDN, and examined possible correlations of these with disease phenotype and activity (symptoms and histology) in a longitudinal study of children with EE. SUBJECTS AND METHODS: Children with EE were studied for up to 24 weeks (12 weeks on 1 of 2 corticosteroid therapies and 12 weeks off therapy). Twenty children with normal esophagogastroduodenoscopies with biopsies were enrolled as controls. Serum IL-5, serum EDN, and stool EDN were measured at weeks 0, 4, 12, 18, and 24 in children with EE, and at baseline alone for controls. Primary and secondary statistical analyses (excluding and including outlier values of the biomarkers, respectively) were performed. RESULTS: Sixty subjects with EE (46 [75%] boys, mean age 7.5 ±â€Š4.4 years) and 20 normal controls (10 [50%] boys, mean age 6.7 ±â€Š4.1 years) were included. Significant changes in serum EDN (significant decrease from baseline to week 4, and then rebound from week 4 to week 12) occurred. Serum EDN levels were stable after week 12. Serum IL-5 and stool EDN levels in subjects with EE were not statistically different from those of the control subjects when each time point for the cases was compared with the controls' 1-time measurement. CONCLUSIONS: Serum EDN levels were significantly higher in subjects with EE than in controls, and the results suggest a possible role, after additional future studies, for serum EDN in establishing EE diagnosis, assessing response to therapy, and/or monitoring for relapse or quiescence.

The Wnt/PCP formin Daam1 drives cell-cell adhesion during nephron development.

E-cadherin junctions facilitate assembly and disassembly of cell contacts that drive development and homeostasis of epithelial tissues. In this study, using Xenopus embryonic kidney and Madin-Darby canine kidney (MDCK) cells, we investigate the role of the Wnt/planar cell polarity (PCP) formin Daam1 (Dishevelled-associated activator of morphogenesis 1) in regulating E-cadherin-based intercellular adhesion. Using live imaging, we show that Daam1 localizes to newly formed cell contacts in the developing nephron. Furthermore, analyses of junctional filamentous actin (F-actin) upon Daam1 depletion indicate decreased microfilament localization and slowed turnover. We also show that Daam1 is necessary for efficient and timely localization of junctional E-cadherin, mediated by Daam1's formin homology domain 2 (FH2). Finally, we establish that Daam1 signaling promotes organized movement of renal cells. This study demonstrates that Daam1 formin junctional activity is critical for epithelial tissue organization.

Identification of Multicolor Fluorescent Probes for Heterogeneous Aß Deposits in Alzheimer's Disease.

Accumulation of amyloid-beta (Aß) into amyloid plaques and hyperphosphorylated tau into neurofibrillary tangles (NFTs) are pathological hallmarks of Alzheimer's disease (AD). There is a significant intra- and inter-individual variability in the morphology and conformation of Aß aggregates, which may account in part for the extensive clinical and pathophysiological heterogeneity observed in AD. In this study, we sought to identify an array of fluorescent dyes to specifically probe Aß aggregates, in an effort to address their diversity. We screened a small library of fluorescent probes and identified three benzothiazole-coumarin derivatives that stained both vascular and parenchymal Aß deposits in AD brain sections. The set of these three dyes allowed the visualization of Aß deposits in three different colors (blue, green and far-red). Importantly, two of these dyes specifically stained Aß deposits with no apparent staining of hyperphosphorylated tau or α-synuclein deposits. Furthermore, this set of dyes demonstrated differential interactions with distinct types of Aß deposits present in the same subject. Aß aggregate-specific dyes identified in this study have the potential to be further developed into Aß imaging probes for the diagnosis of AD. In addition, the far-red dye we identified in this study may serve as an imaging probe for small animal imaging of Aß pathology. Finally, these dyes in combination may help us advance our understanding of the relation between the various Aß deposits and the clinical diversity observed in AD.

The Use of Visceral Proteins as Nutrition Markers: An ASPEN Position Paper.

Serum albumin and prealbumin, well-known visceral proteins, have traditionally been considered useful biochemical laboratory values in a nutrition assessment. However, recent literature disputes this contention. The aim of this document is to clarify that these proteins characterize inflammation rather than describe nutrition status or protein-energy malnutrition. Both critical illness and chronic illness are characterized by inflammation and, as such, hepatic reprioritization of protein synthesis occurs, resulting in lower serum concentrations of albumin and prealbumin. In addition, the redistribution of serum proteins occurs because of an increase in capillary permeability. There is an association between inflammation and malnutrition, however, not between malnutrition and visceral-protein levels. These proteins correlate well with patients' risk for adverse outcomes rather than with protein-energy malnutrition. Therefore, serum albumin and prealbumin should not serve as proxy measures of total body protein or total muscle mass and should not be used as nutrition markers. This paper has been approved by the American Society for Parenteral and Enteral Nutrition Board of Directors.