Transcriptome analysis identifies activated signaling pathways and regulated ABC transporters and solute carriers after hyperosmotic stress in renal MDCK I cells

Integrating Transcriptome and Metabolome Analyses Revealed Salinity Induces Arsenobetaine Biosynthesis in Marine Medaka (Oryzias melastigma)

Marine fish exhibit elevated levels of arsenobetaine (AsB), while the impact and underlying mechanism of salinity on AsB biosynthesis remain inadequately explored. In this study, marine medaka (Oryzias melastigma), typically inhabiting 30‰ high salinity, were gradually acclimated to low salinities of 20, 10, and 0‰. Following acclimation, the fish were exposed to arsenate (As(V)) in their diet for 30 days. Results showed a significant accumulation of total arsenic (As) and AsB concentrations in the muscle and head tissues of the exposed fish, with these accumulations exhibiting a positive correlation with water salinity. Transcriptome analyses revealed that exposure to As(V) at low salinity may disrupt membrane components and induce cytoskeletal injuries, while at high salinity, it triggered oxidoreductase activity and transmembrane transport. Metabolome analyses indicated that low salinity induced osmotic stress, resulting in an increased requirement for amino acids to upload intracellular osmotic equilibrium in O. melastigma. Furthermore, the key organic osmolytes and amino acids, including taurine, l-methionine, guanidinoethyl sulfonate, and N-acetyl-l-aspartic acid, exhibited a negative correlation with the AsB concentration. These findings indicated that salinity can regulate osmotic balance by influencing amino acid synthesis under low salinity and stimulating AsB synthesis under high salinity conditions in O. melastigma. This study provides insights into the impact of high salinity on AsB biosynthesis, the underlying regulatory mechanisms, and implications for managing As(V) risk.

Voltage-gated ion channels as novel regulators of epithelial ion transport in the osmoregulatory organs of insects

Voltage-gated ion channels (VGICs) respond to changes in membrane potential (Vm) and typically exhibit fast kinetic properties. They play an important role in signal detection and propagation in excitable tissues. In contrast, the role of VGICs in non-excitable tissues like epithelia is less studied and less clear. Studies in epithelia of vertebrates and invertebrates demonstrate wide expression of VGICs in epithelia of animals. Recently, VGICs have emerged as regulators of ion transport in the Malpighian tubules (MTs) and other osmoregulatory organs of insects. This mini-review aims to concisely summarize which VGICs have been implicated in the regulation of ion transport in the osmoregulatory epithelia of insects to date, and highlight select groups for further study. We have also speculated on the roles VGICs may potentially play in regulating processes connected directly to ion transport in insects (e.g., acid-base balance, desiccation, thermal tolerance). This review is not meant to be exhaustive but should rather serve as a thought-provoking collection of select existing highlights on VGICs, and to emphasize how understudied this mechanism of ion transport regulation is in insect epithelia.

Genomic insights into the seawater adaptation in Cyprinidae

BACKGROUND

Cyprinidae, the largest fish family, encompasses approximately 367 genera and 3006 species. While they exhibit remarkable adaptability to diverse aquatic environments, it is exceptionally rare to find them in seawater, with the Far Eastern daces being of few exceptions. Therefore, the Far Eastern daces serve as a valuable model for studying the genetic mechanisms underlying seawater adaptation in Cyprinidae.

RESULTS

Here, we sequenced the chromosome-level genomes of two Far Eastern daces (Pseudaspius brandtii and P. hakonensis), the two known cyprinid fishes found in seawater, and performed comparative genomic analyses to investigate their genetic mechanism of seawater adaptation. Demographic history reconstruction of the two species reveals that their population dynamics are correlated with the glacial-interglacial cycles and sea level changes. Genomic analyses identified Pseudaspius-specific genetic innovations related to seawater adaptation, including positively selected genes, rapidly evolving genes, and conserved non-coding elements (CNEs). Functional assays of Pseudaspius-specific variants of the prolactin (prl) gene showed enhanced cell adaptation to greater osmolarity. Functional assays of Pseudaspius specific CNEs near atg7 and usp45 genes suggest that they exhibit higher promoter activity and significantly induced at high osmolarity.

CONCLUSIONS

Our results reveal the genome-wide evidence for the evolutionary adaptation of cyprinid fishes to seawater, offering valuable insights into the molecular mechanisms supporting the survival of migratory fish in marine environments. These findings are significant as they contribute to our understanding of how cyprinid fishes navigate and thrive in diverse aquatic habitats, providing useful implications for the conservation and management of marine ecosystems.

Voltage-gated ion channels are expressed in the Malpighian tubules and anal papillae of the yellow fever mosquito (Aedes aegypti), and may regulate ion transport during salt and water imbalance

Vectors of infectious disease include several species of Aedes mosquitoes. The life cycle of Aedes aegypti, the yellow fever mosquito, consists of a terrestrial adult and an aquatic larval life stage. Developing in coastal waters can expose larvae to fluctuating salinity, causing salt and water imbalance, which is addressed by two prime osmoregulatory organs - the Malpighian tubules (MTs) and anal papillae (AP). Voltage-gated ion channels (VGICs) have recently been implicated in the regulation of ion transport in the osmoregulatory epithelia of insects. In the current study, we: (i) generated MT transcriptomes of freshwater-acclimated and brackish water-exposed larvae of Ae. aegypti, (ii) detected expression of several voltage-gated Ca2+, K+, Na+ and non-ion-selective ion channels in the MTs and AP using transcriptomics, PCR and gel electrophoresis, (iii) demonstrated that mRNA abundance of many altered significantly following brackish water exposure, and (iv) immunolocalized CaV1, NALCN, TRP/Painless and KCNH8 in the MTs and AP of larvae using custom-made antibodies. We found CaV1 to be expressed in the apical membrane of MTs of both larvae and adults, and its inhibition to alter membrane potentials of this osmoregulatory epithelium. Our data demonstrate that multiple VGICs are expressed in osmoregulatory epithelia of Ae. aegypti and may play an important role in the autonomous regulation of ion transport.

Osmolar Modulation Drives Reversible Cell Cycle Exit and Human Pluripotent Cell Differentiation via NF-κВ and WNT Signaling

Terminally differentiated cells are commonly regarded as the most stable cell state in adult organisms, characterized by growth arrest while fulfilling their specialized functions. A better understanding of the mechanisms involved in promoting cell cycle exit will improve the ability to differentiate pluripotent cells into mature tissues for both pharmacological and therapeutic use. Here, it demonstrates that a hyperosmolar environment enforces a protective p53-independent quiescent state in immature hepatoma cells and in pluripotent stem cell-derived models of human hepatocytes and endothelial cells. Prolonged culture in hyperosmolar conditions stimulates changes in gene expression promoting functional cell maturation. Interestingly, hyperosmolar conditions do not only trigger growth arrest and cellular maturation but are also necessary to maintain this maturated state, as switching back to plasma osmolarity reverses the changes in expression of maturation and proliferative markers. Transcriptome analysis revealed sequential stages of osmolarity-regulated growth arrest followed by cell maturation, mediated by activation of NF-κВ, and repression of WNT signaling, respectively. This study reveals that a modulated increase in osmolarity serves as a biochemical signal to promote long-term growth arrest and cellular maturation into different lineages, providing a practical method to generate differentiated hiPSCs that resemble their mature counterpart more closely.

SNAT2 is responsible for hyperosmotic induced sarcosine and glycine uptake in human prostate PC-3 cells

Solute carriers (SLC) are important membrane transport proteins in normal and pathophysiological cells. The aim was to identify amino acid SLC(s) responsible for uptake of sarcosine and glycine in prostate cancer cells and investigate the impact hereon of hyperosmotic stress. Uptake of ¹⁴C-sarcosine and ³H-glycine was measured in human prostate cancer (PC-3) cells cultured under isosmotic (300 mOsm/kg) and hyperosmotic (500 mOsm/kg) conditions for 24 h. Hyperosmotic culture medium was obtained by supplementing the medium with 200 mM of the trisaccharide raffinose. Amino acid SLC expression was studied using RT-PCR, real-time PCR, and western blotting. siRNA knockdown of SNAT2 was performed. Experiments were conducted in at least 3 independent cell passages. The uptake of Sar and Gly was increased approximately 8-ninefold in PC-3 cells after 24 h hyperosmotic culture. PAT1 mRNA and protein could not be detected, while SNAT2 was upregulated at the mRNA and protein level. Transfection with SNAT2-specific siRNA reduced V_max of Sar uptake from 2653 ± 38 to 513 ± 38 nmol mg protein^-1 min^-1, without altering the K_m value (3.19 ± 0.13 vs. 3.42 ± 0.71 mM), indicating that SNAT2 is responsible for at least 80% of Sar uptake in hyperosmotic cultured PC-3 cells. SNAT2 is upregulated in hyperosmotic stressed prostate cancer cells and SNAT2 is responsible for cellular sarcosine and glycine uptake in hyperosmotic cultured PC-3 cells. Sar is identified as a substrate for SNAT2, and this has physiological implications for understanding cellular solute transport in prostate cancer cells.

Novel mechanisms of epithelial ion transport: insights from the cryptonephridial system of lepidopteran larvae

Lepidopterans are among the most widespread and easily recognized insects. Whereas adult lepidopterans are known for their beauty and ecological importance as pollinators and sources of food for other animals, larvae are economically important pests of forests and agricultural crops. In the larval body, rapid growth while feeding on plant-based diet is associated with extreme alkalinity (up to pH = 11) of the midgut lumen that helps digest plant proteins. Additionally, the presence of plant secondary metabolites which serve as anti-herbivory agents requires uninterrupted excretory function, accomplished primarily by the Malpighian tubules (MTs). The so-called cryptonephridial condition, along with extreme regional heterogeneity of the MTs, and the ability to rapidly and reversibly alter the direction of epithelial ion transport are features that allow uninterrupted MT functioning and recycling of base equivalents. Studies of MTs in lepidopteran larvae have revealed that rapid adjustments in epithelial ion transport include unexpected roles for voltage-gated, ligand-gated and mechanosensitive ion channels, as well as gap junctions. These molecular components are present in epithelia of a variety of vertebrates and invertebrates and thus are likely to constitute a universal epithelial toolkit for rapid autonomous regulation of epithelial function.

Voltage-gated calcium channels regulate K+ transport in the Malpighian tubules of the larval cabbage looper, Trichoplusia ni

Transporting epithelia are tissues that specialize in the directional movements of ions and water and are typically either secretory or reabsorptive. Recent work on the Malpighian tubule of larval lepidopterans (caterpillars) demonstrated that the distal ileac plexus segment of this epithelium is capable of rapidly switching between ion secretion and reabsorption. Subsequent transcriptomic studies suggested expression of voltage-gated ion channels in the lepidopteran MTs (which are not contractile and not innervated). The present study shows that isolated MTs of larval Trichoplusia ni express α1, β2, and α2δ4 subunits of voltage-gated Ca²⁺ channel Ca_V1 and that pan-Ca_Vα immunoreactivity is present in the apical and basolateral membranes of the principal cells. Basolateral membrane potential (V_bl) in isolated MTs of larval Trichoplusia ni was influenced by Ca_V1 functioning; pharmacological inhibition of Ca_V1 reversed V_bl from inside-negative to inside-positive, and also reduced transepithelial potential (V_te), lowered [Ca²⁺]_i and reversed the direction of K⁺ transport from secretion to reabsorption. Thus, our findings indicate that a functional Ca_V1 channel is necessary for constitutive K⁺ secretion observed in isolated preparations of lepidopteran MTs. Lastly, V_te and V_bl of isolated MTs were influenced by changes in bathing saline [K⁺]. Our findings suggest that epithelia may rely on Ca_V channels to enable robust ion secretion and downregulation of Ca_V channels, together with other transcriptional changes, enables ion reabsorption.

A Semi-In Vivo Transcriptional Assay to Dissect Plant Defense Regulatory Modules

Plants use different regulatory modules in response to changes in their surroundings. With the transcriptomic approaches governing all research areas, an integrative, fast, and sensitive approach toward validating genes of interest becomes a critical step prior to functional studies in planta. This chapter describes a detailed method for a quantitative analysis of transcriptional readouts of defense response genes using tobacco leaves as a transient system. The method uses Luciferase reporter assays to monitor activities of defense pathway promoters. Under normal conditions, the JASMONATE ZIM-DOMAIN (JAZ) proteins repress defense genes by preventing their expression. Here, we will provide a detailed protocol on the use of a dual-luciferase system to analyze activities of various defense response promoters simultaneously. We will use two well-characterized modules from the Jasmonic acid (JA) defense pathway; the JAZ3 repressor protein and the promoters of three of JA responsive genes, MYC2, 3 and 4. This assay revealed not only differences in promoter strength but also provided quantitative insights on the JAZ3 repression of MYCs in a quantitative manner.

Establishment of a low-tumorigenic MDCK cell line and study of differential molecular networks

Influenza is an acute respiratory infection caused by the influenza virus, and vaccination against influenza is considered the best way to prevent the onset and spread. MDCK (Madin-Darby canine kidney) cells are typically used to isolate the influenza virus, however, their high tumorigenicity is the main controversy in the production of influenza vaccines. Here, MDCK-C09 and MDCK-C35 monoclonal cell lines were established, which were proven to be low in tumorigenicity. RNA-seq of MDCK-C09, MDCK-C35, and MDCK-W73 cells was performed to investigate the putative tumorigenicity mechanisms. Tumor-related molecular interaction analysis of the differentially expressed genes indicates that hub genes, such as CUL3 and EGFR, may play essential roles in tumorigenicity differences between MDCK-C (MDCK-C09 and MDCK-C35) and MDCK-W (MDCK-W73) cells. Moreover, the analysis of cell proliferation regulation-associated molecular interaction shows that downregulated JUN and MYC, for instance, mediate increased proliferation of these cells. The present study provides a new low-tumorigenic MDCK cell line and describes the potential molecular mechanism for the low tumorigenicity and high proliferation rate.

Nfat5 is involved in the hyperosmotic regulation of Tmem184b: a putative modulator of ibuprofen transport in renal MDCK I cells

Nuclear factor of activated T cells 5 (NFAT5) is a transcription factor involved in the regulation of several genes involved in the response to extracellular hyperosmolality. Recently, the uptake of ibuprofen by an as yet unknown carrier was suggested in Madin‐Darby canine kidney (MDCK) I cells exposed to hyperosmolality. We therefore speculated that Nfat5 could be involved in the regulation of this ibuprofen carrier. Reverse transfection with siRNA against Nfat5 was used to knock down Nfat5 in MDCK I cells. The uptake of both radiolabelled taurine and ibuprofen was measured in MDCK I cells, first treated with siRNA against Nfat5 and afterwards cultivated with raffinose‐supplemented normal growth medium (500 mOsm) for 24 h. The siRNA transfection resulted in knockdown of Nfat5, and uptake of both taurine and ibuprofen was significantly decreased in transfected MDCK I cells. The decrease in ibuprofen uptake indicates that Nfat5 is involved in upregulation of the ibuprofen carrier. A transcriptome analysis of MDCK I cells treated with siRNA against Nfat5 revealed 989 genes upregulated by Nfat5 during hyperosmotic exposure. From these genes, the gene product transmembrane protein 184b was found to be regulated by Nfat5, and Tmem184b was the only potential gene product involved in the uptake of ibuprofen in MDCK I cells.

Dataset

The RNA sequencing dataset is available from the NCBI Gene Expression 452 Omnibus (https://www.ncbi.nlm.nih.gov/geo/) with the accession number GSE122074.

Identifying Hub Genes for Heat Tolerance in Water Buffalo (Bubalus bubalis) Using Transcriptome Data

Heat stress has a detrimental effect on the physiological and production performance of buffaloes. Elucidating the underlying mechanisms of heat stress is challenging, therefore identifying candidate genes is urgent and necessary. We evaluated the response of buffaloes (n = 30) to heat stress using the physiological parameters, ELISA indexes, and hematological parameters. We then performed mRNA and microRNA (miRNA) expression profiles analysis between heat tolerant (HT, n = 4) and non-heat tolerant (NHT, n = 4) buffaloes, as well as the specific modules, significant genes, and miRNAs related to the heat tolerance identified using the weighted gene co-expression network analysis (WGCNA). The results indicated that the buffaloes in HT had a significantly lower rectal temperature (RT) and respiratory rate (RR) and displayed a higher plasma heat shock protein (HSP70 and HSP90) and cortisol (COR) levels than those of NHT buffaloes. Differentially expressed analysis revealed a total of 753 differentially expressed genes (DEGs) and 16 differentially expressed miRNAs (DEmiRNAs) were identified between HT and NHT. Using the WGCNA analysis, these DEGs assigned into 5 modules, 4 of which were significantly correlation with the heat stress indexes. Interestingly, 158 DEGs associated with heat tolerance in the turquoise module were identified, 35 of which were found within the protein-protein interaction network. Several hub genes (IL18RAP, IL6R, CCR1, PPBP, IL1B, and IL1R1) were identified that significantly enriched in the Cytokine-cytokine receptor interaction. The findings may help further elucidate the underlying mechanisms of heat tolerance in buffaloes.