bims-bicyki 2021-07-25 papers

bims-bicyki

Biomed News

on Bicaudal-C1 and interactors in cystic kidney disease

Issue of 2021‒07‒25
seventeen papers selected by
Céline Gagnieux
École Polytechnique Fédérale de Lausanne (EPFL)

Identification of pathological transcription in autosomal dominant polycystic kidney disease epithelia.
Urinary citrate as a marker of renal function in patients with autosomal dominant polycystic kidney disease.
Neonatal polycystic kidney disease: a novel variant.
Unilateral polycystic kidney disease.
Phosphorylation of H3-Thr3 by Haspin Is Required for Primary Cilia Regulation.
Rosiglitasone and ROCK Inhibitors Modulate Fibrogenetic Changes in TGF-β2 Treated Human Conjunctival Fibroblasts (HconF) in Different Manners.
Cullin 1 (CUL1) Promotes Primary Ciliogenesis through the Induction of Ubiquitin-Proteasome-Dependent Dvl2 Degradation.
Comparison of ciliary targeting of two rhodopsin-like GPCRs: role of C-terminal localization sequences in relation to cilium type.
From tip to toe - dressing centrioles in γTuRC.
Centriole is the pivot coordinating dynamic signaling for cell proliferation and organization during early development in the vertebrates.
Myocardin-related transcription factor and serum response factor regulate cilium turnover by both transcriptional and local mechanisms.
Roles of NEK family in cell cycle regulation.
Clinical and genetic heterogeneity of primary ciliopathies (Review).
Single-Component Optogenetic Tools for Inducible RhoA GTPase Signaling.
Spatiotemporal model of cellular mechanotransduction via Rho and YAP.
Spectrum of Mutations in Pediatric Non-glomerular Chronic Kidney Disease Stages 2-5.
PPP1CA/YAP/GS/Gln/mTORC1 pathway activates retinal Müller cells during diabetic retinopathy.

Sci Rep. 2021 Jul 23. 11(1): 15139

Identification of pathological transcription in autosomal dominant polycystic kidney disease epithelia.

Sebastian Friedrich, Hannah Müller, Caroline Riesterer, Hannah Schüller, Katja Friedrich, Carlotta Leonie Wörner, Tilman Busch, Amandine Viau, E Wolfgang Kuehn, Michael Köttgen, Alexis Hofherr.

Autosomal dominant polycystic kidney disease (ADPKD) affects more than 12 million people worldwide. Mutations in PKD1 and PKD2 cause cyst formation through unknown mechanisms. To unravel the pathogenic mechanisms in ADPKD, multiple studies have investigated transcriptional mis-regulation in cystic kidneys from patients and mouse models, and numerous dysregulated genes and pathways have been described. Yet, the concordance between studies has been rather limited. Furthermore, the cellular and genetic diversity in cystic kidneys has hampered the identification of mis-expressed genes in kidney epithelial cells with homozygous PKD mutations, which are critical to identify polycystin-dependent pathways. Here we performed transcriptomic analyses of Pkd1- and Pkd2-deficient mIMCD3 kidney epithelial cells followed by a meta-analysis to integrate all published ADPKD transcriptomic data sets. Based on the hypothesis that Pkd1 and Pkd2 operate in a common pathway, we first determined transcripts that are differentially regulated by both genes. RNA sequencing of genome-edited ADPKD kidney epithelial cells identified 178 genes that are concordantly regulated by Pkd1 and Pkd2. Subsequent integration of existing transcriptomic studies confirmed 31 previously described genes and identified 61 novel genes regulated by Pkd1 and Pkd2. Cluster analyses then linked Pkd1 and Pkd2 to mRNA splicing, specific factors of epithelial mesenchymal transition, post-translational protein modification and epithelial cell differentiation, including CD34, CDH2, CSF2RA, DLX5, HOXC9, PIK3R1, PLCB1 and TLR6. Taken together, this model-based integrative analysis of transcriptomic alterations in ADPKD annotated a conserved core transcriptomic profile and identified novel candidate genes for further experimental studies.

DOI: https://doi.org/10.1038/s41598-021-94442-8
Int Urol Nephrol. 2021 Jul 19.

Urinary citrate as a marker of renal function in patients with autosomal dominant polycystic kidney disease.

Francisco José Borrego Utiel, Isidoro Herrera Contreras, Enoc Merino García, Maria Victoria Camacho Reina, Clara Moriana Domínguez, Esther Ocaña Pérez.

  INTRODUCTION: Autosomal dominant polycystic kidney disease (ADPKD) is frequent to find low urinary citrate levels. Recently, it has been suggested that urinary citrate could be a marker of covert metabolic acidosis in chronic kidney disease.OBJECTIVE: Our aim was to analyze relationship between urinary citrate levels, renal function, and serum bicarbonate in ADPKD patients.
METHODS: We determined citrate in 24-h collected urine from ADPKD patients and correlated with glomerular filtration rate (CKD-EPI equation) and serum bicarbonate concentration.
RESULTS: We included 120 patients, 60% men, eGFR was 71 ± 32 mL/min/1.73 m2. Urinary citrate/creatinine ratio was 195 ± 152 mg/gCr (range 1.2-689) with levels significantly higher in females. Urinary citrate lower than 300 mg/gCr was present in 75% of patients and when considering chronic kidney stages (CKD), we observed reduced levels in 48.8% in CKD1 stage, in 79.4% in CKD2 stage, in 96.2% in CKD3 stage, and in 94.7% of patients in CKD4 stage. Urinary citrate was correlated with serum creatinine (r = - 0.61, p < 0.001) and eGFR (r = 0.55, p < 0.001) in both gender. We did not find any correlation with serum bicarbonate. Using a general linear modeling analysis, we found as predictors of urinary citrate/creatinine ratio to glomerular filtration rate, gender, and age. Lower levels of urinary citrate were accompanied by a decline in urinary osmolality and in renal excretion of calcium and uric acid. In a subgroup of patients, we measured total kidney volume and we found an inverse correlation with urinary citrate levels that disappeared when it was corrected with glomerular filtration rate.
CONCLUSIONS: Urinary citrate is very frequently reduced in ADPKD patients being present from very early CKD stages. Their levels in urine are inversely correlated with glomerular filtration rate and it is not related with serum bicarbonate concentration. We think that it would be interesting to study urinary citrate as a marker of chronic kidney disease in ADPKD patients.

Keywords:  Acidosis; Chronic kidney disease; Citrate; Polycystic kidney disease

DOI:  https://doi.org/10.1007/s11255-021-02953-0
BMJ Case Rep. 2021 Jul 21. pii: e242991. [Epub ahead of print]14(7):

Neonatal polycystic kidney disease: a novel variant.

Catherine Finnegan, Claire Murphy, Fionnuala Breathnach.

  Polycystic kidney disease (PKD) is a condition typified by multiple renal cysts and renal enlargement. Classification is usually determined by mode of inheritance-autosomal dominant PKD (ADPKD) or autosomal recessive PKD (ARPKD). ARPKD frequently presents in fetal life, but here we report a rare case of a family with two siblings diagnosed with ADPKD manifesting in utero with novel genetic findings. During the first pregnancy, enlarged cystic kidneys were noted at the gestational age (GA) of 18 weeks, which became progressively larger and anyhdramnios ensued by GA of 25 weeks. The couple opted to terminate the pregnancy. The second pregnancy similarly presented with bilateral enlarged cystic kidneys, but amniotic fluid remained normal throughout and she delivered at GA of 36 weeks. Genetic testing revealed the fetus to be heterozygous in AD PKD1, which is known to cause ADPKD and heterozygous for a hypomorphic allele for ADPKD of uncertain significance. The fetus was also found to be heterozygous in the AR PKHD1 gene with a variant not previously described in the literature. Where fetal features consistent with ARPKD are identified in the setting of familial ADPKD, this fetal manifestation of ADPKD, resulting from combined variants in the PKD1 gene, should be considered.

Keywords:  materno-fetal medicine; pregnancy; renal medicine

DOI:  https://doi.org/10.1136/bcr-2021-242991
Kidney Int. 2021 Aug;pii: S0085-2538(21)00144-7. [Epub ahead of print]100(2): 483

Unilateral polycystic kidney disease.

Carissa Y Dumancas, Fouad T Chebib.

DOI: https://doi.org/10.1016/j.kint.2021.01.011
Int J Mol Sci. 2021 Jul 20. pii: 7753. [Epub ahead of print]22(14):

Phosphorylation of H3-Thr3 by Haspin Is Required for Primary Cilia Regulation.

Roberto Quadri, Sarah Sertic, Anna Ghilardi, Diego Rondelli, Guido Roberto Gallo, Luca Del Giacco, Marco Muzi-Falconi.

  Primary cilia are commonly found on most quiescent, terminally differentiated cells and play a major role in the regulation of the cell cycle, cell motility, sensing, and cell-cell communication. Alterations in ciliogenesis and cilia maintenance are causative of several human diseases, collectively known as ciliopathies. A key determinant of primary cilia is the histone deacetylase HDAC6, which regulates their length and resorption and whose distribution is regulated by the death inducer-obliterator 3 (Dido3). Here, we report that the atypical protein kinase Haspin is a key regulator of cilia dynamics. Cells defective in Haspin activity exhibit longer primary cilia and a strong delay in cilia resorption upon cell cycle reentry. We show that Haspin is active in quiescent cells, where it phosphorylates threonine 3 of histone H3, a known mitotic Haspin substrate. Forcing Dido3 detachment from the chromatin prevents Haspin inhibition from impacting cilia dynamics, suggesting that Haspin activity is required for the relocalization of Dido3-HDAC6 to the basal body. Exploiting the zebrafish model, we confirmed the physiological relevance of this mechanism. Our observations shed light on a novel player, Haspin, in the mechanisms that govern the determination of cilia length and the homeostasis of mature cilia.

Keywords:  Dido3; H3T3; HDAC6; Haspin; ciliopathy; primary cilia; zebrafish

DOI:  https://doi.org/10.3390/ijms22147753
Int J Mol Sci. 2021 Jul 08. pii: 7335. [Epub ahead of print]22(14):

Rosiglitasone and ROCK Inhibitors Modulate Fibrogenetic Changes in TGF-β2 Treated Human Conjunctival Fibroblasts (HconF) in Different Manners.

Yuika Oouchi, Megumi Watanabe, Yosuke Ida, Hiroshi Ohguro, Fumihito Hikage.

  PURPOSE: The effects of Rho-associated coiled-coil containing protein kinase (ROCK) 1 and 2 inhibitor, ripasudil hydrochloride hydrate (Rip), ROCK2 inhibitor, KD025 or rosiglitazone (Rosi) on two-dimension (2D) and three-dimension (3D) cultured human conjunctival fibroblasts (HconF) treated by transforming growth factor (TGFβ2) were studied.METHODS: Two-dimension and three-dimension cultured HconF were examined by transendothelial electrical resistance (TEER, 2D), size and stiffness (3D), and the expression of the extracellular matrix (ECM) including collagen1 (COL1), COL4 and COL6, fibronectin (FN), and α-smooth muscle actin (αSMA) by quantitative PCR (2D, 3D) in the presence of Rip, KD025 or Rosi.
RESULTS: TGFβ2 caused a significant increase in (1) the TEER values (2D) which were greatly reduced by Rosi, (2) the stiffness of the 3D organoids which were substantially reduced by Rip or KD025, and (3) TGFβ2 induced a significant up-regulation of all ECMs, except for COL6 (2D) or αSMA (3D), and down-regulation of COL6 (2D). Rosi caused a significant up-regulation of COL1, 4 and 6 (3D), and down-regulation of COL6 (2D) and αSMA (3D). Most of these TGFβ2-induced expressions in the 2D and αSMA in the 3D were substantially inhibited by KD025, but COL4 and αSMA in 2D were further enhanced by Rip.
CONCLUSION: The findings reported herein indicate that TGFβ2 induces an increase in fibrogenetic changes on the plane and in the spatial space, and are inhibited by Rosi and ROCK inhibitors, respectively.

Keywords:  3D culture; KD025; ROCK inhibitor; TGFβ2; human conjunctival fibroblast; ripasudil; rosiglitazone

DOI:  https://doi.org/10.3390/ijms22147335
Int J Mol Sci. 2021 Jul 15. pii: 7572. [Epub ahead of print]22(14):

Cullin 1 (CUL1) Promotes Primary Ciliogenesis through the Induction of Ubiquitin-Proteasome-Dependent Dvl2 Degradation.

Sun-Ok Kim, Kyoung Sang Cho, Bo Yeon Kim, Kyung Ho Lee.

  Primary cilia are nonmotile cellular signal-sensing antenna-like structures composed of microtubule-based structures that distinguish them from motile cilia in structure and function. Primary ciliogenesis is regulated by various cellular signals, such as Wnt, hedgehog (Hh), and platelet-derived growth factor (PDGF). The abnormal regulation of ciliogenesis is closely related to developing various human diseases, including ciliopathies and cancer. This study identified a novel primary ciliogenesis factor Cullin 1 (CUL1), a core component of Skp1-Cullin-F-box (SCF) E3 ubiquitin ligase complex, which regulates the proteolysis of dishevelled 2 (Dvl2) through the ubiquitin-proteasome system. Through immunoprecipitation-tandem mass spectrometry analysis, 176 Dvl2 interacting candidates were identified, of which CUL1 is a novel Dvl2 modulator that induces Dvl2 ubiquitination-dependent degradation. Neddylation-dependent CUL1 activity at the centrosomes was essential for centrosomal Dvl2 degradation and primary ciliogenesis. Therefore, this study provides a new mechanism of Dvl2 degradation by CUL1, which ultimately leads to primary ciliogenesis, and suggest a novel target for primary cilia-related human diseases.

Keywords:  CUL1; Dvl2; primary ciliogenesis; proteolysis; ubiquitination

DOI:  https://doi.org/10.3390/ijms22147572
J Neurosci. 2021 Jul 22. pii: JN-RM-0357-21. [Epub ahead of print]

Comparison of ciliary targeting of two rhodopsin-like GPCRs: role of C-terminal localization sequences in relation to cilium type.

Abhishek Chadha, Antonio E Paniagua, David S Williams.

Primary cilia exhibit a distinct complement of proteins, including G-protein-coupled receptors (GPCRs) that mediate sensory and developmental signals. The localization of GPCRs to the ciliary membrane involves ciliary localization sequences (CLSs), but it is not known how CLSs might relate to cilium type. Here, we studied the localization of two RHO-like GPCRs, SSTR3 and RHO, in three types of cilia: from IMCD3 cells, hTERT-RPE1 cells (possessing pocket cilia), and rod photoreceptors (whose cilia grow into elaborate phototransductive outer segments). SSTR3 was localized specifically to all three types of cilia, whereas RHO showed more selectivity for the photoreceptor cilium. Focusing on C-terminal CLSs, we characterized a novel CLS in the SSTR3 C-terminus, which was required for the robust ciliary localization of SSTR3. Replacing the C-terminus of RHO with this SSTR3 CLS enhanced ciliary localization, compared with full-length RHO, in IMCD3 and hTERT-RPE1 cells. Addition of the SSTR3 CLS to the single transmembrane protein, CD8A, enabled ciliary localization. In hTERT-RPE1 cells, a partial SSTR3 CLS added to CD8A effected specific localization to the periciliary (pocket) membrane, demonstrating C-terminal localization sequence targeting to this domain. Using retinas from mice, including both sexes, we show that deletion of the C-terminus of RHO reduced its rod outer segment localization and that addition of the SSTR3 C-terminal CLS to the truncated RHO partly rescued this mislocalization. Overall, the study details elements of the different C-termini of SSTR3 and RHO that are major effectors in determining specificity of cilium (or pericilium) localization among different types of cilia.SIGNIFICANCE STATEMENTThe localization of G-protein-coupled receptors to primary cilia is key to many types of signal transduction. After characterizing a novel C-terminal ciliary localization sequence (CLS) in SSTR3, we investigated how SSTR3 and RHO localization to the cilium relates to C-terminal CLSs and to cilium type. We found that the SSTR3 C-terminal CLS was effective in three different types of cilia, but the RHO C-terminus showed a clear localization preference for the highly elaborate photoreceptor cilium. When added to CD8A, part of the SSTR3 CLS promoted specific periciliary membrane localization in hTERT-RPE1 cells, demonstrating an effective CLS for this domain. Thus, we demonstrate that elements of the C-termini of SSTR3 and RHO determine different localization patterns among different types of cilia.

DOI: https://doi.org/10.1523/JNEUROSCI.0357-21.2021
J Cell Sci. 2021 Jul 15. pii: jcs258397. [Epub ahead of print]134(14):

From tip to toe - dressing centrioles in γTuRC.

Nina Schweizer, Jens Lüders.

  Centrioles are microtubule-based cylindrical structures that assemble the centrosome and template the formation of cilia. The proximal part of centrioles is associated with the pericentriolar material, a protein scaffold from which microtubules are nucleated. This activity is mediated by the γ-tubulin ring complex (γTuRC) whose central role in centrosomal microtubule organization has been recognized for decades. However, accumulating evidence suggests that γTuRC activity at this organelle is neither restricted to the pericentriolar material nor limited to microtubule nucleation. Instead, γTuRC is found along the entire centriole cylinder, at subdistal appendages, and inside the centriole lumen, where its canonical function as a microtubule nucleator might be supplemented or replaced by a function in microtubule anchoring and centriole stabilization, respectively. In this Opinion, we discuss recent insights into the expanded repertoire of γTuRC activities at centrioles and how distinct subpopulations of γTuRC might act in concert to ensure centrosome and cilia biogenesis and function, ultimately supporting cell proliferation, differentiation and homeostasis. We propose that the classical view of centrosomal γTuRC as a pericentriolar material-associated microtubule nucleator needs to be revised.

Keywords:  Centriole; Centrosome; Ciliogenesis; Microtubules; PCM; γTuRC

DOI:  https://doi.org/10.1242/jcs.258397
Cell Biol Int. 2021 Jul 21.

Centriole is the pivot coordinating dynamic signaling for cell proliferation and organization during early development in the vertebrates.

O J Roopasree, Adivitiya, Soura Chakraborty, Suneel Kateriya, Shobi Veleri.

  Vertebrates have an elaborate and functionally segmented body. It evolves from a single cell by systematic cell proliferation but attains a complex body structure with exquisite precision. This development requires two cellular events: cell cycle and ciliogenesis. For these events, the dynamic molecular signaling is converged at the centriole. The cell cycle helps in cell proliferation and growth of the body and is a highly regulated and integrated process. Its errors cause malignancies and developmental disorders. The cells newly proliferated are organized during organogenesis. For a cellular organization, dedicated signaling hubs are developed in the cells, and most often cilia are utilized. The cilium is generated from one of the centrioles involved in cell proliferation. The developmental signaling pathways hosted in cilia are essential for the elaboration of the body plan. The cilium's compartmental seclusion is ideal for noise-free molecular signaling and is essential for the precision of the body layout. The dysfunctional centrioles and primary cilia distort the development of body layout that manifest as serious developmental disorders. Thus, centriole has a dual role in the growth and cellular organization. It organizes dynamically expressed molecules of cell cycle and ciliogenesis and plays a balancing act to generate new cells and organize them during development. A putative master molecule may regulate and coordinate the dynamic gene expression at the centrioles. The convergence of many critical signaling components at the centriole reiterates the idea that centriole is a major molecular workstation involved in elaborating the structural design and complexity in vertebrates. This article is protected by copyright. All rights reserved.

Keywords:  cell division; cellular signaling; centriole; cilia; gene expression; vertebrate development

DOI:  https://doi.org/10.1002/cbin.11667
iScience. 2021 Jul 23. 24(7): 102739

Myocardin-related transcription factor and serum response factor regulate cilium turnover by both transcriptional and local mechanisms.

Pam Speight, Matthew Rozycki, Shruthi Venugopal, Katalin Szászi, Michael Kofler, András Kapus.

  Turnover of the primary cilium (PC) is critical for proliferation and tissue homeostasis. Each key component of the PC resorption machinery, the HEF1/Aurora kinase A (AurA)/HDAC6 pathway harbors cis-elements potentially targeted by the transcriptional co-activator myocardin-related transcription factor (MRTF) and/or its partner serum response factor (SRF). Thus we investigated if MRTF and/or SRF regulate PC turnover. Here we show that (1) both MRTF and SRF are indispensable for serum-induced PC resorption, and (2) they act via both transcriptional and local mechanisms. Intriguingly, MRTF and SRF are present in the basal body and/or the PC, and serum facilitates ciliary MRTF recruitment. MRTF promotes the stability and ciliary accumulation of AurA and facilitates SRF phosphorylation. Ciliary SRF interacts with AurA and HDAC6. MRTF also inhibits ciliogenesis. It interacts with and is required for the correct localization of the ciliogenesis modulator CEP290. Thus, MRTF and SRF are critical regulators of PC assembly and/or disassembly, acting both as transcription factors and as PC constituents.

Keywords:  cell biology; functional aspects of cell biology; organizational aspects of cell biology

DOI:  https://doi.org/10.1016/j.isci.2021.102739
Yi Chuan. 2021 Jul 20. 43(7): 642-653

Roles of NEK family in cell cycle regulation.

Yuan-Yuan Li, Lei Guo, Zhi-Ming Han.

  As a serine/threonine kinase, NIMA-related kinases (NEKs) play important roles in the regulation of cell cycle, and involve in several cellular activities such as centrosome separation, spindle assembly, chromatin condensation, nuclear envelope breakdown, spindle assembly checkpoint signaling, cytokinesis, cilia formation and DNA damage response. In this review, we summarize the component, structural characteristics and functions of NEK family in mitosis and meiosis based on the relevant researches in recent years, providing a reference for the further study on the roles of NEKs in the regulation of cell cycle and a theoretical basis for the clinical diagnosis and treatment of tumors.

Keywords:  NIMA-related kinases; meiosis; mitosis

DOI:  https://doi.org/10.16288/j.yczz.20-421
Int J Mol Med. 2021 Sep;pii: 176. [Epub ahead of print]48(3):

Clinical and genetic heterogeneity of primary ciliopathies (Review).

Ina Ofelia Focșa, Magdalena Budișteanu, Mihaela Bălgrădean.

  Ciliopathies comprise a group of complex disorders, with involvement of the majority of organs and systems. In total, >180 causal genes have been identified and, in addition to Mendelian inheritance, oligogenicity, genetic modifications, epistatic interactions and retrotransposon insertions have all been described when defining the ciliopathic phenotype. It is remarkable how the structural and functional impairment of a single, minuscule organelle may lead to the pathogenesis of highly pleiotropic diseases. Thus, combined efforts have been made to identify the genetic substratum and to determine the pathophysiological mechanism underlying the clinical presentation, in order to diagnose and classify ciliopathies. Yet, predicting the phenotype, given the intricacy of the genetic cause and overlapping clinical characteristics, represents a major challenge. In the future, advances in proteomics, cell biology and model organisms may provide new insights that could remodel the field of ciliopathies.

Keywords:  cilia; ciliopathies; epistasis; modifier; oligogenic; pleiotropy; signaling

DOI:  https://doi.org/10.3892/ijmm.2021.5009
Adv Biol (Weinh). 2021 Jul 21. e2100810

Single-Component Optogenetic Tools for Inducible RhoA GTPase Signaling.

Erin E Berlew, Ivan A Kuznetsov, Keisuke Yamada, Lukasz J Bugaj, Joel D Boerckel, Brian Y Chow.

  Optogenetic tools are created to control RhoA GTPase, a central regulator of actin organization and actomyosin contractility. RhoA GTPase, or its upstream activator ARHGEF11, is fused to BcLOV4, a photoreceptor that can be dynamically recruited to the plasma membrane by a light-regulated protein-lipid electrostatic interaction with the inner leaflet. Direct membrane recruitment of these proteins induces potent contractile signaling sufficient to separate adherens junctions with as little as one pulse of blue light. Induced cytoskeletal morphology changes are dependent on the alignment of the spatially patterned stimulation with the underlying cell polarization. RhoA-mediated cytoskeletal activation drives yes-associated protein (YAP) nuclear localization within minutes and consequent mechanotransduction verified by YAP-transcriptional enhanced associate domain transcriptional activity. These single-transgene tools do not require protein binding partners for dynamic membrane localization and permit spatiotemporally precise control over RhoA signaling to advance the study of its diverse regulatory roles in cell migration, morphogenesis, and cell cycle maintenance.

Keywords:  RhoA; light-oxygen-voltage; optogenetics

DOI:  https://doi.org/10.1002/adbi.202100810
Integr Biol (Camb). 2021 Jul 17. pii: zyab012. [Epub ahead of print]

Spatiotemporal model of cellular mechanotransduction via Rho and YAP.

Javor K Novev, Mathias L Heltberg, Mogens H Jensen, Amin Doostmohammadi.

  How cells sense and respond to mechanical stimuli remains an open question. Recent advances have identified the translocation of Yes-associated protein (YAP) between nucleus and cytoplasm as a central mechanism for sensing mechanical forces and regulating mechanotransduction. We formulate a spatiotemporal model of the mechanotransduction signalling pathway that includes coupling of YAP with the cell force-generation machinery through the Rho family of GTPases. Considering the active and inactive forms of a single Rho protein (GTP/GDP-bound) and of YAP (non-phosphorylated/phosphorylated), we study the cross-talk between cell polarization due to active Rho and YAP activation through its nuclear localization. For fixed mechanical stimuli, our model predicts stationary nuclear-to-cytoplasmic YAP ratios consistent with experimental data at varying adhesive cell area. We further predict damped and even sustained oscillations in the YAP nuclear-to-cytoplasmic ratio by accounting for recently reported positive and negative YAP-Rho feedback. Extending the framework to time-varying mechanical stimuli that simulate cyclic stretching and compression, we show that the YAP nuclear-to-cytoplasmic ratio's time dependence follows that of the cyclic mechanical stimulus. The model presents one of the first frameworks for understanding spatiotemporal YAP mechanotransduction, providing several predictions of possible YAP localization dynamics, and suggesting new directions for experimental and theoretical studies.

Keywords:  Rho GTPase signalling; YAP activation; YAP nuclear translocation; cell polarization; mechanotransduction; protein oscillations

DOI:  https://doi.org/10.1093/intbio/zyab012
Front Genet. 2021 ;12 697085

Spectrum of Mutations in Pediatric Non-glomerular Chronic Kidney Disease Stages 2-5.

Xiaoyuan Wang, Huijie Xiao, Yong Yao, Ke Xu, Xiaoyu Liu, Baige Su, Hongwen Zhang, Na Guan, Xuhui Zhong, Yanqin Zhang, Jie Ding, Fang Wang.

  Renal hypodysplasia and cystic kidney diseases, the common non-glomerular causes of pediatric chronic kidney disease (CKD), are usually diagnosed by their clinical and imaging characteristics. The high degree of phenotypic heterogeneity, in both conditions, makes the correct final diagnosis dependent on genetic testing. It is not clear, however, whether the frequencies of damaged alleles vary among different ethnicities in children with non-glomerular CKD, and this will influence the strategy used for genetic testing. In this study, 69 unrelated children (40 boys, 29 girls) of predominantly Han Chinese ethnicity with stage 2-5 non-glomerular CKD caused by suspected renal hypodysplasia or cystic kidney diseases were enrolled and assessed by molecular analysis using proband-only targeted exome sequencing and array-comparative genomic hybridization. Targeted exome sequencing discovered genetic etiologies in 33 patients (47.8%) covering 10 distinct genetic disorders. The clinical diagnoses in 13/48 patients (27.1%) with suspected renal hypodysplasia were confirmed, and two patients were reclassified carrying mutations in nephronophthisis (NPHP) genes. The clinical diagnoses in 16/20 patients (80%) with suspected cystic kidney diseases were confirmed, and one patient was reclassified as carrying a deletion in the hepatocyte nuclear factor-1-beta gene (HNF1B). The diagnosis of one patient with unknown non-glomerular disease was elucidated. No copy number variations were identified in the 20 patients with negative targeted exome sequencing results. NPHP genes were the most common disease-causing genes in the patients with disease onsets above 6 years of age (14/45, 31.1%). The children with stage 2 and 3 CKD at onset were found to carry causative mutations in paired box gene 2 (PAX2) and HNF1B gene (11/24, 45.8%), whereas those with stage 4 and 5 CKD mostly carried causative mutations in NPHP genes (19/45, 42.2%). The causative genes were not suspected by the kidney imaging patterns at disease onset. Thus, our data show that in Chinese children with non-glomerular renal dysfunction caused by renal hypodysplasia and cystic kidney diseases, the common causative genes vary with age and CKD stage at disease onset. These findings have the potential to improve management and genetic counseling of these diseases in clinical practice.

Keywords:  chronic kidney disease; cystic kidney diseases; genetic diagnosis; non-glomerular; renal hypodysplasia; targeted exome sequencing

DOI:  https://doi.org/10.3389/fgene.2021.697085
Exp Eye Res. 2021 Jul 17. pii: S0014-4835(21)00269-4. [Epub ahead of print]210 108703

PPP1CA/YAP/GS/Gln/mTORC1 pathway activates retinal Müller cells during diabetic retinopathy.

Yang Guo, Xiaomin Cang, Linling Zhu, Manhui Zhu, Aihong Li, Zhenzhen Wang, Yuting Zhang, Xueqin Wang, E Song.

  Diabetic retinopathy (DR) is a vision-loss complication caused by diabetes with high prevalence. During DR, the retinal microvascular injury and neurodegeneration derived from chronic hyperglycemia have attracted global attention to retinal Müller cells (RMCs), the major macroglia in the retina contributes to neuroprotection. Protein Phosphatase 1 Catalytic Subunit Alpha (PPP1CA) dephosphorylates the transcriptional coactivator Yes-associated protein (YAP) to promote the transcription of glutamine synthetase (GS). GS catalyzes the transformation of neurotoxic glutamate (Glu) into nontoxic glutamine (Gln) to activate the mammalian target of rapamycin complex 1 (mTORC1), which promotes the activation of RMCs. In this study, in vitro MIO-M1 cell and in vivo mouse high-fat diet and streptozotocin (STZ)-induced diabetic model to explore the role of the PPP1CA/YAP/GS/Gln/mTORC1 pathway on the activation of MRCs during DR. Results showed that PPP1CA promoted the dephosphorylation and nuclear translocation of YAP in high glucose (HG)-exposed MIO-M1 cells. YAP transcribed GS in HG-exposed MIO-M1 cells in a TEAD1-dependent and PPP1CA-dependent way. GS promoted the biosynthesis of Gln in HG-exposed MIO-M1 cells. Gln activated mTORC1 instead of mTORC2 in HG-exposed MIO-M1 cells. The proliferation and activation of HG-exposed MIO-M1 cells were PPP1CA/YAP/GS/Gln/mTORC1-dependent. Finally, RMC proliferation and activation during DR were inhibited by the PPP1CA/YAP/GS/Gln/mTORC1 blockade. The findings supplied a potential idea to protect RMCs and alleviate the development of DR.

Keywords:  Diabetic retinopathy (DR); Mammalian target of rapamycin complex 1 (mTOR 1); Protein phosphatase 1 catalytic subunit alpha (PPP1CA); Retinal Müller cells (RMCs)

DOI:  https://doi.org/10.1016/j.exer.2021.108703