Role of autophagy and ferroptosis in the development of endometriotic cysts (Review).

It is considered that the etiology of endometriosis is retrograde menstruation of endometrial tissue. Although shed endometrial cells are constantly exposed to a challenging environment with iron overload, oxidative stress and hypoxia, a few cells are able to survive and continue to proliferate and invade. Ferroptosis, an iron­dependent form of non­apoptotic cell death, is known to play a major role in the development and course of endometriosis. However, few papers have concentrated on the dynamic interaction between autophagy and ferroptosis throughout the progression of diseases. The present review summarized the current understanding of the mechanisms underlying autophagy and ferroptosis in endometriosis and discuss their role in disease development and progression. For the present narrative review electronic databases including PubMed and Google Scholar were searched for literature published up to the October 31, 2023. Autophagy and ferroptosis may be activated at early stages in endometriosis development. On the other hand, excessive activation of intrinsic pathways (e.g., estrogen and mechanistic target of rapamycin) may promote disease progression through autophagy inhibition. Furthermore, suppression of ferroptosis may cause further progression of endometriotic lesions. In conclusion, the autophagy and ferroptosis pathways may play a dual role in disease initiation and progression. The present review discussed the temporal transition of non­apoptotic cell death regulation during disease progression from retrograde endometrium to early lesions to established lesions.

HL156A, an AMP-Activated Protein Kinase Activator, Inhibits Cyst Growth in Autosomal Dominant Polycystic Kidney Disease.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is the most prevalent genetic kidney disorder. While metformin has demonstrated the ability to inhibit cyst growth in animal models of ADPKD via activation of adenosine monophosphate-activated protein kinase (AMPK), its effectiveness in humans is limited due to its low potency. This study explored the impact of HL156A, a new and more potent AMPK activator, in a mouse model of ADPKD. METHODS: To investigate whether HL156A inhibits the proliferation of renal cyst cells in ADPKD in vitro, exogenous human telomerase reverse transcriptase (hTERT)-immortalized renal cyst cells from ADPKD patients were treated with HL156A, and an MTT (dimethylthiazol-diphenyltetrazolium bromide) assay was performed. To assess the cyst-inhibitory effect of HL156A in vivo, we generated Pkd1 conditional knockout (KO) mice with aquaporin 2 (AQP2)-Cre, which selectively expresses Cre recombinase in the collecting duct. The effectiveness of HL156A in inhibiting cyst growth and improving renal function was confirmed by measuring the number of cysts and blood urea nitrogen (BUN) levels in the collecting duct-specific Pkd1 KO mice. RESULTS: When cyst cells were treated with up to 20 µM of metformin or HL156A, HL156A reduced cell viability by 25% starting at a concentration of 5 µM, whereas metformin showed no effect. When AQP2-Cre male mice were crossed with Pkd1flox/flox female mice, and when AQP2-Cre female mice were crossed with Pkd1flox/flox male mice, the number of litters produced by both groups was comparable. In collecting duct-specific Pkd1 KO mice, HL156A was found to inhibit cyst growth, reducing both the number and size of cysts. Furthermore, it was confirmed that kidney function improved as HL156A treatment led to a reduction in elevated BUN levels. Lastly, it was observed that the increase in AMPK phosphorylation induced by HL156A decreased ERK phosphorylation and α-SMA expression. CONCLUSION: HL156A has potential as a drug that can restore kidney function in ADPKD patients by inhibiting cyst growth.

NAMPT Overexpression Drives Cell Growth in Polycystic Liver Disease through Mitochondrial Metabolism Regulation.

A group of genetic diseases known as polycystic liver disease (PLD) are distinguished by the gradual development of fluid-filled hepatic cysts formed from cholangiocytes and commonly related to primary cilia defects. The NAD salvage pathway, which sustains cellular bioenergetics and supplies a required substrate for tasks important to rapidly multiplying cells, has a rate-limiting phase that is mediated by nicotinamide phosphoribosyltransferase (NAMPT). In this study, the efficacy and mechanisms of action of FK866, a novel, high-potency NAMPT inhibitor with a good toxicity profile, were assessed. NAMPT-siRNA and FK866 reduced NAD levels and inhibited the proliferation of PLD cells in a dose-dependent manner. Notably, this pharmacologic and siRNA-mediated suppression of NAMPT was less effective in normal cells at the same concentrations. The addition of nicotinamide mononucleotide (NMN), a byproduct of NAMPT that restores NAD concentration, rescued the cellular viability of PLD cells and verified the on-target action of FK866. In FK866-treated PLD cells, mitochondrial respiration and ATP production were impaired and reactive oxygen species production was induced. Importantly, FK866 treatment was associated with improved effects of octreotide, a drug used for PLD treatment. As a result, the use of NAMPT inhibitors, including FK866 therapy, offers the possibility of a further targeted strategy for the therapeutic treatment of PLD.

Defective mesenchymal Bmpr1a-mediated BMP signaling causes congenital pulmonary cysts.

Abnormal lung development can cause congenital pulmonary cysts, the mechanisms of which remain largely unknown. Although the cystic lesions are believed to result directly from disrupted airway epithelial cell growth, the extent to which developmental defects in lung mesenchymal cells contribute to abnormal airway epithelial cell growth and subsequent cystic lesions has not been thoroughly examined. In the present study using genetic mouse models, we dissected the roles of bone morphogenetic protein (BMP) receptor 1a (Bmpr1a)-mediated BMP signaling in lung mesenchyme during prenatal lung development and discovered that abrogation of mesenchymal Bmpr1a disrupted normal lung branching morphogenesis, leading to the formation of prenatal pulmonary cystic lesions. Severe deficiency of airway smooth muscle cells and subepithelial elastin fibers were found in the cystic airways of the mesenchymal Bmpr1a knockout lungs. In addition, ectopic mesenchymal expression of BMP ligands and airway epithelial perturbation of the Sox2-Sox9 proximal-distal axis were detected in the mesenchymal Bmpr1a knockout lungs. However, deletion of Smad1/5, two major BMP signaling downstream effectors, from the lung mesenchyme did not phenocopy the cystic abnormalities observed in the mesenchymal Bmpr1a knockout lungs, suggesting that a Smad-independent mechanism contributes to prenatal pulmonary cystic lesions. These findings reveal for the first time the role of mesenchymal BMP signaling in lung development and a potential pathogenic mechanism underlying congenital pulmonary cysts.

Congenital disorders are medical conditions that are present from birth. Although many congenital disorders are rare, they can have a severe impact on the quality of life of those affected. For example, congenital pulmonary airway malformation (CPAM) is a rare congenital disorder that occurs in around 1 out of every 25,000 pregnancies. In CPAM, abnormal, fluid-filled sac-like pockets of tissue, known as cysts, form within the lungs of unborn babies. After birth, these cysts become air-filled and do not behave like normal lung tissue and stop a baby's lungs from working properly. In severe cases, babies with CPAM need surgery immediately after birth. We still do not understand exactly what the underlying causes of CPAM might be. CPAM is not considered to be hereditary ­ that is, it does not appear to be passed down in families ­ nor is it obviously linked to any environmental factors. CPAM is also very difficult to study, because researchers cannot access tissue samples during the critical early stages of the disease. To overcome these difficulties, Luo et al. wanted to find a way to study CPAM in the laboratory. First, they developed a non-human animal 'model' that naturally forms CPAM-like lung cysts, using genetically modified mice where the gene for the signaling molecule Bmpr1a had been deleted in lung cells. Normally, Bmpr1a is part of a set of the molecular instructions, collectively termed BMP signaling, which guide healthy lung development early in life. However, mouse embryos lacking Bmpr1a developed abnormal lung cysts that were similar to those found in CPAM patients, suggesting that problems with BMP signalling might also trigger CPAM in humans. Luo et al. also identified several other genes in the Bmpr1a-deficient mouse lungs that had abnormal patterns of activity. All these genes were known to be controlled by BMP signaling, and to play a role in the development and organisation of lung tissue. This suggests that when these genes are not controlled properly, they could drive formation of CPAM cysts when BMP signaling is compromised. This work is a significant advance in the tools available to study CPAM. Luo et al.'s results also shed new light on the molecular mechanisms underpinning this rare disorder. In the future, Luo et al. hope this knowledge will help us develop better treatments for CPAM, or even help to prevent it altogether.

The Tilapia Cyst Tissue Enclosing the Proliferating Myxobolus bejeranoi Parasite Exhibits Cornified Structure and Immune Barrier Function.

Myxozoa, a unique group of obligate endoparasites within the phylum Cnidaria, can cause emerging diseases in wild and cultured fish populations. Recently, the myxozoan Myxobolus bejeranoi has been identified as a prevalent pathogen infecting the gills of cultured hybrid tilapia, leading to systemic immune suppression and considerable mortality. Here, we employed a proteomic approach to examine the impact of M. bejeranoi infection on fish gills, focusing on the structure of the granulomata, or cyst, formed around the proliferating parasite to prevent its spread to surrounding tissue. Enrichment analysis showed increased immune response and oxidative stress in infected gill tissue, most markedly in the cyst's wall. The intense immune reaction included a consortium of endopeptidase inhibitors, potentially combating the myxozoan arsenal of secreted proteases. Analysis of the cyst's proteome and histology staining indicated that keratin intermediate filaments contribute to its structural rigidity. Moreover, we uncovered skin-specific proteins, including a grainyhead-like transcription factor and a teleost-specific S100 calcium-binding protein that may play a role in epithelial morphogenesis and cysts formation. These findings deepen our understanding of the proteomic elements that grant the cyst its distinctive nature at the critical interface between the fish host and myxozoan parasite.

Transcriptomic analysis of subarachnoid cysts of Taenia solium reveals mechanisms for uncontrolled proliferation and adaptations to the microenvironment.

Subarachnoid neurocysticercosis (SANCC) is caused by an abnormally transformed form of the metacestode or larval form of the tapeworm Taenia solium. In contrast to vesicular parenchymal and ventricular located cysts that contain a viable scolex and are anlage of the adult tapeworm, the subarachnoid cyst proliferates to form aberrant membranous cystic masses within the subarachnoid spaces that cause mass effects and acute and chronic arachnoiditis. How subarachnoid cyst proliferates and interacts with the human host is poorly understood, but parasite stem cells (germinative cells) likely participate. RNA-seq analysis of the subarachnoid cyst bladder wall compared to the bladder wall and scolex of the vesicular cyst revealed that the subarachnoid form exhibits activation of signaling pathways that promote proliferation and increased lipid metabolism. These adaptions allow growth in a nutrient-limited cerebral spinal fluid. In addition, we identified therapeutic drug targets that would inhibit growth of the parasite, potentially increase effectiveness of treatment, and shorten its duration.

Genetics of cystogenesis in base-edited human organoids reveal therapeutic strategies for polycystic kidney disease.

In polycystic kidney disease (PKD), microscopic tubules expand into macroscopic cysts. Among the world's most common genetic disorders, PKD is inherited via heterozygous loss-of-function mutations but is theorized to require additional loss of function. To test this, we establish human pluripotent stem cells in allelic series representing four common nonsense mutations, using CRISPR base editing. When differentiated into kidney organoids, homozygous mutants spontaneously form cysts, whereas heterozygous mutants (original or base corrected) express no phenotype. Using these, we identify eukaryotic ribosomal selective glycosides (ERSGs) as PKD therapeutics enabling ribosomal readthrough of these same nonsense mutations. Two different ERSGs not only prevent cyst initiation but also limit growth of pre-formed cysts by partially restoring polycystin expression. Furthermore, glycosides accumulate in cyst epithelia in organoids and mice. Our findings define the human polycystin threshold as a surmountable drug target for pharmacological or gene therapy interventions, with relevance for understanding disease mechanisms and future clinical trials.

ArHsp90 is important in stress tolerance and embryo development of the brine shrimp, Artemia franciscana.

Females of the extremophile crustacean, Artemia franciscana, either release motile nauplii via the ovoviviparous pathway or encysted embryos (cysts) via the oviparous pathway. Cysts contain an abundant amount of the ATP-independent small heat shock protein that contributes to stress tolerance and embryo development, however, little is known of the role of ATP-dependent molecular chaperone, heat shock protein 90 (Hsp90) in the two processes. In this study, a hsp90 was cloned from A. franciscana. Characteristic domains of ArHsp90 were simulated from the deduced amino acid sequence, and 3D structures of ArHsp90 and Hsp90s of organisms from different groups were aligned. RNA interference was then employed to characterize ArHsp90 in A. franciscana nauplii and cysts. The partial knockdown of ArHsp90 slowed the development of nauplius-destined, but not cyst-destined embryos. ArHsp90 knockdown also reduced the survival and stress tolerance of nauplii newly released from A. franciscana females. Although the reduction of ArHsp90 had no effect on the development of diapause-destined embryos, the resulting cysts displayed reduced tolerance to desiccation and low temperature, two stresses normally encountered by A. franciscana in its natural environment. The results reveal that Hsp90 contributes to the development, growth, and stress tolerance of A. franciscana, an organism of practical importance as a feed source in aquaculture.

[Aging-associated Cyst Formation and Fibrosis].

Cysts are abnormal fluid-filled sacs found in various human organs, including the liver. Liver cysts can be associated with known causes such as parasite infections and gene mutations, or simply aging. Among these causes, simple liver cysts are often found in elderly people. While they are generally benign, they may occasionally grow but rarely shrink with age, indicating their clear association with aging. However, the mechanism behind the formation of simple liver cysts has not been thoroughly investigated. Recently, we have generated transgenic mice that specifically overexpress fibroblast growth factor (FGF)18 in hepatocytes. These mice exhibit severe liver fibrosis without inflammation and spontaneously develop liver cysts that grow with age. Our findings suggest that simple liver cysts can be induced by fibrosis accompanied by sterile inflammation or injury, whereas fibrosis accompanied by severe inflammation or injury may lead to cirrhosis. We also discuss the detrimental effects of disease- and aging-associated fibrosis in various organs, such as the heart, lungs, and kidneys. Additionally, we provide a brief summary of the two currently approved anti-fibrotic drugs for idiopathic pulmonary fibrosis, nintedanib and pirfenidone, as well as their possibility of future expansion of application toward other fibrotic diseases.

The Link between Autosomal Dominant Polycystic Kidney Disease and Chromosomal Instability: Exploring the Relationship.

In autosomal dominant polycystic kidney disease (ADPKD) with germline mutations in a PKD1 or PKD2 gene, innumerable cysts develop from tubules, and renal function deteriorates. Second-hit somatic mutations and renal tubular epithelial (RTE) cell death are crucial features of cyst initiation and disease progression. Here, we use established RTE lines and primary ADPKD cells with disease-associated PKD1 mutations to investigate genomic instability and DNA damage responses. We found that ADPKD cells suffer severe chromosome breakage, aneuploidy, heightened susceptibility to DNA damage, and delayed checkpoint activation. Immunohistochemical analyses of human kidneys corroborated observations in cultured cells. DNA damage sensors (ATM/ATR) were activated but did not localize at nuclear sites of damaged DNA and did not properly activate downstream transducers (CHK1/CHK2). ADPKD cells also had the ability to transform, as they achieved high saturation density and formed colonies in soft agar. Our studies indicate that defective DNA damage repair pathways and the somatic mutagenesis they cause contribute fundamentally to the pathogenesis of ADPKD. Acquired mutations may alternatively confer proliferative advantages to the clonally expanded cell populations or lead to apoptosis. Further understanding of the molecular details of aberrant DNA damage responses in ADPKD is ongoing and holds promise for targeted therapies.

Activation of farnesoid X receptor retards expansion of renal collecting duct cell-derived cysts via inhibition of CFTR-mediated Cl- secretion.

The transcription factor farnesoid X receptor (FXR) regulates energy metabolism. Specifically, FXR functions to regulate cystic fibrosis transmembrane conductance regulator (CFTR)-mediated Cl- secretion in intestinal epithelial cells. Therefore, this study aimed to investigate the role of FXR in CFTR-mediated Cl- secretion in renal tubular cells and to further elucidate its effects on renal cyst formation and growth. CFTR-mediated Cl- transport was evaluated via short-circuit current (ISC) measurements in Madin-Darby canine kidney (MDCK) cell monolayers and primary rat inner medullary collecting duct cells. The role of FXR in renal cyst formation and growth was determined by the MDCK cell-derived cyst model. Incubation with synthesized (GW4064) and endogenous (CDCA) FXR ligands reduced CFTR-mediated Cl- secretion in a concentration- and time-dependent manner. The inhibitory effect of FXR ligands was not due to the result of reduced cell viability and was attenuated by cotreatment with an FXR antagonist. FXR activation significantly decreased CFTR protein but not its mRNA. In addition, FXR activation inhibited CFTR-mediated Cl- secretion in primary renal collecting duct cells. FXR activation decreased ouabain-sensitive ISC without altering Na+-K+-ATPase mRNA and protein levels. Furthermore, FXR activation significantly reduced the number of cysts and renal cyst expansion. These inhibitory effects were correlated with a decrease in the expression of protein synthesis regulators mammalian target of rapamycin/S6 kinase. This study shows that FXR activation inhibits Cl- secretion in renal cells via inhibition of CFTR expression and retards renal cyst formation and growth. The discoveries point to a physiological role of FXR in the regulation of CFTR and a potential therapeutic application in polycystic kidney disease treatment.NEW & NOTEWORTHY The present study reveals that farnesoid X receptor (FXR) activation reduces microcyst formation and enlargement. This inhibitory effect of FXR activation is involved with decreased cell proliferation and cystic fibrosis transmembrane conductance regulator-mediated Cl- secretion in renal collecting duct cells. FXR might represent a novel target for the treatment of autosomal dominant polycystic kidney disease.

The Cyst Epithelium in Polycystic Kidney Disease Patients Displays Normal Apical-Basolateral Cell Polarity.

The main characteristic of polycystic kidney disease is the development of multiple fluid-filled renal cysts. The discovery of mislocalized sodium-potassium pump (Na,K-ATPase) in the apical membrane of cyst-lining epithelia alluded to reversal of polarity as a possible explanation for the fluid secretion. The topic of apical Na,K-ATPase in cysts remains controversial. We investigated the localization of the Na,K-ATPase and assessed the apical-basolateral polarization of cyst-lining epithelia by means of immunohistochemistry in kidney tissue from six polycystic kidney disease patients undergoing nephrectomy. The Na,K-ATPase α1 subunit was conventionally situated in the basolateral membrane of all immunoreactive cysts. Proteins of the Crumbs and partitioning defective (Par) complexes were localized to the apical membrane domain in cyst epithelial cells. The apical targeting protein Syntaxin-3 also immunolocalized to the apical domain of cyst-lining epithelial cells. Proteins of the basolateral Scribble complex immunolocalized to the basolateral domain of cysts. Thus, no deviations from the typical epithelial distribution of basic cell polarity proteins were observed in the cysts from the six patients. Furthermore, we confirmed that cysts can originate from virtually any tubular segment with preserved polarity. In conclusion, we find no evidence of a reversal in apical-basolateral polarity in cyst-lining epithelia in polycystic kidney disease.

Inhibiting centrosome clustering reduces cystogenesis and improves kidney function in autosomal dominant polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is a monogenic disorder accounting for approximately 5% of patients with renal failure, yet therapeutics for the treatment of ADPKD remain limited. ADPKD tissues display abnormalities in the biogenesis of the centrosome, a defect that can cause genome instability, aberrant ciliary signaling, and secretion of pro-inflammatory factors. Cystic cells form excess centrosomes via a process termed centrosome amplification (CA), which causes abnormal multipolar spindle configurations, mitotic catastrophe, and reduced cell viability. However, cells with CA can suppress multipolarity via "centrosome clustering," a key mechanism by which cells circumvent apoptosis. Here, we demonstrate that inhibiting centrosome clustering can counteract the proliferation of renal cystic cells with high incidences of CA. Using ADPKD human cells and mouse models, we show that preventing centrosome clustering with 2 inhibitors, CCB02 and PJ34, blocks cyst initiation and growth in vitro and in vivo. Inhibiting centrosome clustering activates a p53-mediated surveillance mechanism leading to apoptosis, reduced cyst expansion, decreased interstitial fibrosis, and improved kidney function. Transcriptional analysis of kidneys from treated mice identified pro-inflammatory signaling pathways implicated in CA-mediated cystogenesis and fibrosis. Our results demonstrate that centrosome clustering is a cyst-selective target for the improvement of renal morphology and function in ADPKD.

A transcriptomics-based RNAi screen for regulators of meiosis and early stages of oocyte development in Drosophila melanogaster.

A properly regulated series of developmental and meiotic events must occur to ensure the successful production of gametes. In Drosophila melanogaster ovaries, these early developmental and meiotic events include the production of the 16-cell cyst, meiotic entry, synaptonemal complex (SC) formation, recombination, and oocyte specification. In order to identify additional genes involved in early oocyte development and meiosis, we reanalyzed 3 published single-cell RNA-seq datasets from Drosophila ovaries, using vasa (germline) together with c(3)G, cona, and corolla (SC) as markers. Our analysis generated a list of 2,743 co-expressed genes. Many known SC-related and early oocyte development genes fell within the top 500 genes on this list, as ranked by the abundance and specificity of each gene's expression across individual analyses. We tested 526 available RNAi lines containing shRNA constructs in germline-compatible vectors representing 331 of the top 500 genes. We assessed targeted ovaries for SC formation and maintenance, oocyte specification, cyst development, and double-strand break dynamics. Six uncharacterized genes exhibited early developmental defects. SC and developmental defects were observed for additional genes not well characterized in the early ovary. Interestingly, in some lines with developmental delays, meiotic events could still be completed once oocyte specificity occurred indicating plasticity in meiotic timing. These data indicate that a transcriptomics approach can be used to identify genes involved in functions in a specific cell type in the Drosophila ovary.

A synthetic agent ameliorates polycystic kidney disease by promoting apoptosis of cystic cells through increased oxidative stress.

Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenic cause of chronic kidney disease and the fourth leading cause of end-stage kidney disease, accounting for over 50% of prevalent cases requiring renal replacement therapy. There is a pressing need for improved therapy for ADPKD. Recent insights into the pathophysiology of ADPKD revealed that cyst cells undergo metabolic changes that up-regulate aerobic glycolysis in lieu of mitochondrial respiration for energy production, a process that ostensibly fuels their increased proliferation. The present work leverages this metabolic disruption as a way to selectively target cyst cells for apoptosis. This small-molecule therapeutic strategy utilizes 11beta-dichloro, a repurposed DNA-damaging anti-tumor agent that induces apoptosis by exacerbating mitochondrial oxidative stress. Here, we demonstrate that 11beta-dichloro is effective in delaying cyst growth and its associated inflammatory and fibrotic events, thus preserving kidney function in perinatal and adult mouse models of ADPKD. In both models, the cyst cells with homozygous inactivation of Pkd1 show enhanced oxidative stress following treatment with 11beta-dichloro and undergo apoptosis. Co-administration of the antioxidant vitamin E negated the therapeutic benefit of 11beta-dichloro in vivo, supporting the conclusion that oxidative stress is a key component of the mechanism of action. As a preclinical development primer, we also synthesized and tested an 11beta-dichloro derivative that cannot directly alkylate DNA, while retaining pro-oxidant features. This derivative nonetheless maintains excellent anti-cystic properties in vivo and emerges as the lead candidate for development.

Basigin Deficiency Induces Spontaneous Polycystic Kidney in Mice.

BACKGROUND: Polycystic kidney disease is the most common hereditary kidney disorder with early and frequent hypertension symptoms. The mechanisms of cyst progression in polycystic kidney disease remain incompletely understood. METHODS: Bsg (basigin) heterozygous and homozygous knockout mice were generated using cas9 system, and Bsg overexpression was achieved by adeno-associated virus serotype 9 injection. Renal morphology was investigated through histological and imaging analysis. Molecular analysis was performed through transcriptomic profiling and biochemical approaches. RESULTS: Bsg-deficient mice exhibited significantly elevated arterial blood pressure. Further investigation demonstrated that Bsg deficiency triggers spontaneous cystic formation in mouse kidneys, which shares similar cyst pathological features and common transcriptional regulatory pathways with human polycystic kidney disease. Moreover, Bsg disruption promoted polycystin-1 ubiquitination and degradation, leading to activation of polycystic kidney disease associated cAMP and AMPK signaling pathways in Bsg knockout mouse kidneys. Finally, adeno-associated virus serotype 9 mediated Bsg reexpression reversed cystic progression in Bsg knockout mice in vivo, and Bsg overexpression inhibited the expansion of Madin-Darby canine kidney cysts in vitro. CONCLUSIONS: Our findings show that Bsg deficiency leads to an early-onset spontaneous polycystic kidney phenotype, suggesting that dysregulated Bsg signaling may be a contributing factor in cystogenesis.

Ablation of Long Noncoding RNA Hoxb3os Exacerbates Cystogenesis in Mouse Polycystic Kidney Disease.

SIGNIFICANCE STATEMENT: Long noncoding RNAs (lncRNAs) are a class of nonprotein coding RNAs with pivotal functions in development and disease. They have emerged as an exciting new drug target category for many common conditions. However, the role of lncRNAs in autosomal dominant polycystic kidney disease (ADPKD) has been understudied. This study provides evidence implicating a lncRNA in the pathogenesis of ADPKD. We report that Hoxb3os is downregulated in ADPKD and regulates mammalian target of rapamycin (mTOR)/Akt pathway in the in vivo mouse kidney. Ablating the expression of Hoxb3os in mouse polycystic kidney disease (PKD) activated mTOR complex 2 (mTORC2) signaling and exacerbated the cystic phenotype. The results from our study provide genetic proof of concept for future studies that focus on targeting lncRNAs as a treatment option in PKD. BACKGROUND: ADPKD is a monogenic disorder characterized by the formation of kidney cysts and is primarily caused by mutations in two genes, PKD1 and PKD2 . METHODS: In this study, we investigated the role of lncRNA Hoxb3os in ADPKD by ablating its expression in the mouse. RESULTS: Hoxb3os -null mice were viable and had grossly normal kidney morphology but displayed activation of mTOR/Akt signaling and subsequent increase in kidney cell proliferation. To determine the role of Hoxb3os in cystogenesis, we crossed the Hoxb3os -null mouse to two orthologous Pkd1 mouse models: Pkhd1/Cre; Pkd1F/F (rapid cyst progression) and Pkd1RC/RC (slow cyst progression). Ablation of Hoxb3os exacerbated cyst growth in both models. To gain insight into the mechanism whereby Hoxb3os inhibition promotes cystogenesis, we performed western blot analysis of mTOR/Akt pathway between Pkd1 single-knockout and Pkd1 - Hoxb3os double-knockout (DKO) mice. Compared with single-knockout, DKO mice presented with enhanced levels of total and phosphorylated Rictor. This was accompanied by increased phosphorylation of Akt at Ser 473 , a known mTORC2 effector site. Physiologically, kidneys from DKO mice displayed between 50% and 60% increase in cell proliferation and cyst number. CONCLUSIONS: The results from this study indicate that ablation of Hoxb3os in mouse PKD exacerbates cystogenesis and dysregulates mTORC2.

Rel governs loser elimination during stem cell competition in the Drosophila testis.

In the Drosophila testis, a group of stromal cells termed hub provides multiple niche signals for the surrounding germline and somatic stem cells. Stem cells of both populations compete for physical retention in the niche, and clones unable to transduce any one niche signal are rapidly eliminated from the stem cell pool by differentiation. We have mapped the transcriptomes of isolated somatic cyst stem cells and differentiated cyst cells, and found that the stem cells but not their differentiated progeny exhibit the signature of an innate immune response including the NF-κB transcription factor Relish (Rel). Related signalling pathways had previously implicated in cell competition in larval epithelia, prompting the question of whether NF-κB signalling was, despite the clear differences between the two competition scenarios, also involved in stem cell competition in the testis. Here we show i) that in the testis Rel is dispensable for stemness, ii) that loss of Rel or the upstream receptor Toll suppresses loser elimination following a variety of different triggers used to induce loser fate, and iii) that clonal Rel activation is sufficient for the displacement of neutral or winner cells from the niche, even if these cells otherwise retain stem cell properties.

Germline and Somatic Cell Syncytia in Insects.

Syncytia are common in the animal and plant kingdoms both under normal and pathological conditions. They form through cell fusion or division of a founder cell without cytokinesis. A particular type of syncytia occurs in invertebrate and vertebrate gametogenesis when the founder cell divides several times with partial cytokinesis producing a cyst (nest) of germ line cells connected by cytoplasmic bridges. The ultimate destiny of the cyst's cells differs between animal groups. Either all cells of the cyst become the gametes or some cells endoreplicate or polyploidize to become the nurse cells (trophocytes). Although many types of syncytia are permanent, the germ cell syncytium is temporary, and eventually, it separates into individual gametes. In this chapter, we give an overview of syncytium types and focus on the germline and somatic cell syncytia in various groups of insects. We also describe the multinuclear giant cells, which form through repetitive nuclear divisions and cytoplasm hypertrophy, but without cell fusion, and the accessory nuclei, which bud off the oocyte nucleus, migrate to its cortex and become included in the early embryonic syncytium.