Development of a rapamycin-inducible protein-knockdown system in the unicellular red alga Cyanidioschyzon merolae.

An inducible protein-knockdown system is highly effective for investigating the functions of proteins and mechanisms essential for the survival and growth of organisms. However, this technique is not available in photosynthetic eukaryotes. The unicellular red alga Cyanidioschyzon merolae possesses a very simple cellular and genomic architecture and is genetically tractable but lacks RNA interference machinery. In this study, we developed a protein-knockdown system in this alga. The constitutive system utilizes the destabilizing activity of the FRB domain of human target of rapamycin (TOR) kinase or its derivatives to knock down target proteins. In the inducible system, rapamycin treatment induces the heterodimerization of the human FKBP12-rapamycin binding (FRB) domain fused to the target proteins with the human FK506-binding protein 12 (FKBP) fused to S-phase kinase associated protein 1 (SKP1) or Cullin 1 (CUL1), subunits of the SCF E3 ubiquitin ligase. This results in the rapid degradation of the target proteins through the ubiquitin-proteasome pathway. With this system, we successfully degraded endogenous essential proteins such as the chloroplast division protein Dynamin related protein 5B (DRP5B) and E2 transcription factor (E2F), a regulator of the G1/S transition, within 2-3 hours after rapamycin administration, enabling the assessment of resulting phenotypes. This rapamycin-inducible protein-knockdown system contributes to the functional analysis of genes whose disruption leads to lethality.

A case of progressive right ventricular failure with ventricular arrhythmia and aortic insufficiency after implantable left ventricular assist device implantation.

Right ventricular failure (RVF) is a serious complication after left ventricular assist device (LVAD) implantation. In this report, a case of RVF that developed over two years after LVAD implantation is presented. The patient was a 12-year-old male with dilated phase of hypertrophic cardiomyopathy. He had no risk factors for early or late-onset RVF. However, his right ventricular function worsened after he developed ventricular arrhythmia (VA), and right ventricular dysfunction became exacerbated with an increasing frequency of VAs. He also developed moderate aortic insufficiency (AI), which became severe. Two years after implantation, he was admitted for treatment of recurrent ventricular tachycardia and became inotropic-dependent during hospitalization. Finally, he underwent successful heart transplantation 2 years and 9 months after LVAD implantation. This case suggests that vicious cycle of RV dysfunction, recurrent VAs and severe AI could lead to RVF in patients without known risk factors for RVF, even long after LVAD implantation. Learning objective: This report shows a progressive right ventricular failure (RVF) two years after left ventricular assist device (LVAD) implantation. Although the patient had no known risk factor, vicious circle of RV dysfunction, ventricular arrhythmias (VAs) and aortic insufficiency (AI) lead to RVF. Patients with LVAD as destination therapy will increase and require long-term LVAD management. We should recognize that these patients could develop RVF even years after LVAD implantation in association with VAs and AI.

A novel pathogenic variant located just upstream of the C-terminal Ser423-X-Ser425 phosphorylation motif in SMAD3 causing Loeys-Dietz syndrome.

OBJECTIVE: Loeys-Dietz syndrome (LDS) is a heritable disorder of connective tissue closely related to Marfan syndrome (MFS). LDS is caused by loss-of-function variants of genes that encode components of transforming growth factor-ß (TGF-ß) signaling; nevertheless, LDS type 1/2 caused by TGFBR1/2 pathogenic variants is frequently found to have paradoxical increases in TGF-ß signaling in the aneurysmal aortic wall. Here, we present a Japanese LDS family having a novel SMAD3 variant. METHODS: The proband was tested via clinical, genetic, and histological analyses. In vitro analysis was performed for pathogenic evaluation. RESULTS: The novel heterozygous missense variant of SMAD3 [c.1262G>A, p.(Cys421Tyr)], located just upstream of the C-terminal Ser423-X-Ser425 phosphorylation motif, was found in this instance of LDS type 3. This variant led to reduced phospho-SMAD3 (Ser423/Ser425) levels and transcription activity in vitro; however, a paradoxical upregulation of TGF-ß signaling was evident in the aortic wall. CONCLUSIONS: Our results revealed the presence of TGF-ß paradox in this case with the novel loss-of-function SMAD3 variant. The precise mechanism underlying the paradox is unknown, but further research is warranted to clarify the influence of the SMAD3 variant type and location on the LDS3 phenotype as well as the molecular mechanism leading to LDS3 aortopathy.

The Polycomb repressive complex 2 deposits H3K27me3 and represses transposable elements in a broad range of eukaryotes.

The mobility of transposable elements (TEs) contributes to evolution of genomes. Their uncontrolled activity causes genomic instability; therefore, expression of TEs is silenced by host genomes. TEs are marked with DNA and H3K9 methylation, which are associated with silencing in flowering plants, animals, and fungi. However, in distantly related groups of eukaryotes, TEs are marked by H3K27me3 deposited by the Polycomb repressive complex 2 (PRC2), an epigenetic mark associated with gene silencing in flowering plants and animals. The direct silencing of TEs by PRC2 has so far only been shown in one species of ciliates. To test if PRC2 silences TEs in a broader range of eukaryotes, we generated mutants with reduced PRC2 activity and analyzed the role of PRC2 in extant species along the lineage of Archaeplastida and in the diatom P. tricornutum. In this diatom and the red alga C. merolae, a greater proportion of TEs than genes were repressed by PRC2, whereas a greater proportion of genes than TEs were repressed by PRC2 in bryophytes. In flowering plants, TEs contained potential cis-elements recognized by transcription factors and associated with neighbor genes as transcriptional units repressed by PRC2. Thus, silencing of TEs by PRC2 is observed not only in Archaeplastida but also in diatoms and ciliates, suggesting that PRC2 deposited H3K27me3 to silence TEs in the last common ancestor of eukaryotes. We hypothesize that during the evolution of Archaeplastida, TE fragments marked with H3K27me3 were selected to shape transcriptional regulation, controlling networks of genes regulated by PRC2.

PGC-1α-mediated angiogenesis prevents pulmonary hypertension in mice.

Pulmonary hypertension (PH) is a life-threatening disease characterized by a progressive narrowing of pulmonary arterioles. Although VEGF is highly expressed in lung of patients with PH and in animal PH models, the involvement of angiogenesis remains elusive. To clarify the pathophysiological function of angiogenesis in PH, we compared the angiogenic response in hypoxia (Hx) and SU5416 (a VEGFR2 inhibitor) plus Hx (SuHx) mouse PH models using 3D imaging. The 3D imaging analysis revealed an angiogenic response in the lung of the Hx-PH, but not of the severer SuHx-PH model. Selective VEGFR2 inhibition with cabozantinib plus Hx in mice also suppressed angiogenic response and exacerbated Hx-PH to the same extent as SuHx. Expression of endothelial proliferator-activated receptor γ coactivator 1α (PGC-1α) increased along with angiogenesis in lung of Hx-PH but not SuHx mice. In pulmonary endothelial cell-specific Ppargc1a-KO mice, the Hx-induced angiogenesis was suppressed, and PH was exacerbated along with increased oxidative stress, cellular senescence, and DNA damage. By contrast, treatment with baicalin, a flavonoid enhancing PGC-1α activity in endothelial cells, ameliorated Hx-PH with increased Vegfa expression and angiogenesis. Pulmonary endothelial PGC-1α-mediated angiogenesis is essential for adaptive responses to Hx and might represent a potential therapeutic target for PH.

Teneligliptin, a DPP-4 Inhibitor, Improves Vascular Endothelial Function via Divergent Actions Including Changes in Circulating Endothelial Progenitor Cells.

Purpose: Dipeptidyl peptidase-4 (DPP-4) inhibitors increase endothelial progenitor cells (EPCs) in peripheral blood circulation. However, the underlying mechanisms and effects on vascular endothelial function remain unclear. We evaluated whether the DPP-4 inhibitor teneligliptin increases circulating EPCs by inhibiting stromal-derived factor-1α (SDF-1α) and improves flow-mediated vascular dilatation (FMD) in type 2 diabetes mellitus patients with acute coronary syndrome (ACS) or its risk factors. Patients and Methods: This single-center, open-label, prospective, randomized controlled trial evaluated 17 patients (hemoglobin A1c ≤7.5% and peak creatinine phosphokinase <2000 IU/mL) with ACS or a history of ACS or multiple cardiovascular risk factors. Metabolic variables of glucose and lipids, circulating EPCs, plasma DPP-4 activity, and SDF-1α levels, and FMD were evaluated at baseline and 28 ± 4 weeks after enrollment. Patients were randomly assigned to either the teneligliptin (n = 8) or control (n = 9) groups. Results: The DPP-4 activity (∆-509.5 ± 105.7 vs ∆32.8 ± 53.4 µU/mL) and SDF-1α levels (∆-695.6 ± 443.2 vs ∆11.1 ± 193.7 pg/mL) were significantly decreased after 28 weeks in the teneligliptin group than those in the control group. The number of EPCs showed an increasing trend in the teneligliptin treated group; albeit this did not reach statistical significance. Glucose and lipid levels were not significantly different between the groups before and after 28 weeks. However, FMD was significantly improved in the teneligliptin group when compared to the control group (∆3.8% ± 2.1% vs ∆-0.3% ± 2.9%, P=0.006). Conclusion: Teneligliptin improved FMD through a mechanism other than increasing the number of circulating EPCs.

The ratio of TAPSE to PASP predicts prognosis in lung transplant candidates with pulmonary arterial hypertension.

Lung transplantation (LT) is the only option for patients with pulmonary arterial hypertension (PAH) refractory to maximal medical therapy. However, some patients referred for LT could survive without LT, and its determinants remain unclear. This study aimed to elucidate prognostic factors of severe PAH at the referral time. We retrospectively analyzed 34 patients referred for LT evaluation. The primary outcome was a composite of death or LT. Over a median follow-up period of 2.56 years, eight patients received LT and eight died. Compared with LT-free survival group, pulmonary arterial systolic pressure (PASP) was higher (p = 0.042), and the ratio of tricuspid annular plane systolic excursion (TAPSE) to PASP (TAPSE/PASP) was lower (p = 0.01) in LT or death group. In receiver operating characteristic analysis, the area under the curve was 0.759 (95% confidence interval 0.589-0.929) for TAPSE/PASP to predict primary outcome, and the optimal cut-off value was 0.30 mm/mmHg (sensitivity 0.875 and specificity 0.667). In a multivariate analysis, TAPSE/PASP was independently associated with death or LT. Kaplan-Meier analysis showed a better LT-free survival in patients with TAPSE/PASP ≧0.30 mm/mmHg than in those with < 0.30 mm/mmHg (p = 0.001). Low-level TAPSE/PASP could be a poor prognostic factor in PAH patients referred for LT evaluation.

Prognostic value of follow-up vasoreactivity test in pulmonary arterial hypertension.

BACKGROUND: Acute vasoreactivity test with inhaled nitric oxide (NO) is performed during diagnostic right heart catheterization (RHC) to identify patients with pulmonary arterial hypertension (PAH) who respond to calcium channel blockers. Our purpose was to investigate the prognostic importance of follow-up vasoreactivity test after treatment. METHODS: We retrospectively analyzed 36 PAH patients (mean age, 47 years; 61 % treatment-naïve), who underwent diagnostic and follow-up RHC and vasoreactivity tests at our center. The primary outcome was all-cause mortality. RESULTS: The median time between baseline and follow-up RHC was 9.7 months. Absolute change in mean pulmonary arterial pressure (ΔmPAP) during NO challenge was less pronounced after treatment, but there was great variability among patients. Overall cohort was dichotomized into two groups: preserved vasoreactivity (ΔmPAP ≤ -1 mmHg) and less vasoreactivity (ΔmPAP ≥0 mmHg) at follow-up RHC. Less vasoreactivity group had higher usage rate of endothelin receptor antagonists and parenteral prostacyclin analogues. During a median observation period of 6.3 years after follow-up RHC, 7 patients died, of which 6 showed less vasoreactivity at follow-up. Absolute ΔmPAP ≥0 at follow-up RHC was associated with all-cause mortality in univariable Cox regression analysis (hazard ratio, 8.728; 95 % confidence interval, 1.045-72.887; p = 0.045), whereas other hemodynamic parameters were not. Absolute ΔmPAP ≥0 at follow-up RHC was associated with all-cause mortality in multivariable Cox analysis adjusted for age and known PAH prognostic factors (HR, 12.814; 95 % CI, 1.088-150.891; p = 0.043). Kaplan-Meier survival analysis revealed a significantly worse survival of less vasoreactivity group compared to preserved vasoreactivity group (log-rank test, p = 0.016). CONCLUSIONS: Follow-up vasoreactivity test after treatment could contribute to the detection of high-risk subgroups who might need careful monitoring and referral for lung transplantation.

Life cycle and functional genomics of the unicellular red alga Galdieria for elucidating algal and plant evolution and industrial use.

Sexual reproduction is widespread in eukaryotes; however, only asexual reproduction has been observed in unicellular red algae, including Galdieria, which branched early in Archaeplastida. Galdieria possesses a small genome; it is polyextremophile, grows either photoautotrophically, mixotrophically, or heterotrophically, and is being developed as an industrial source of vitamins and pigments because of its high biomass productivity. Here, we show that Galdieria exhibits a sexual life cycle, alternating between cell-walled diploid and cell wall-less haploid, and that both phases can proliferate asexually. The haploid can move over surfaces and undergo self-diploidization or generate heterozygous diploids through mating. Further, we prepared the whole genome and a comparative transcriptome dataset between the diploid and haploid and developed genetic tools for the stable gene expression, gene disruption, and selectable marker recycling system using the cell wall-less haploid. The BELL/KNOX and MADS-box transcription factors, which function in haploid-to-diploid transition and development in plants, are specifically expressed in the haploid and diploid, respectively, and are involved in the haploid-to-diploid transition in Galdieria, providing information on the missing link of the sexual life cycle evolution in Archaeplastida. Four actin genes are differently involved in motility of the haploid and cytokinesis in the diploid, both of which are myosin independent and likely reflect ancestral roles of actin. We have also generated photosynthesis-deficient mutants, such as blue-colored cells, which were depleted in chlorophyll and carotenoids, for industrial pigment production. These features of Galdieria facilitate the understanding of the evolution of algae and plants and the industrial use of microalgae.

Severe aortic stenosis during leptin replacement therapy in a patient with generalized lipodystrophy-associated progeroid syndrome due to an LMNA variant: A case report.

Leptin replacement therapy (LRT) has drastically improved the prognosis of patients with lipodystrophy, but pro-inflammatory properties of leptin could become evident in the long term. Here, we report a 30-year-old Japanese woman with generalized lipodystrophy-associated progeroid syndrome due to a heterozygous LMNA variant (c.29C > T; p.T10I), who was diagnosed with severe aortic stenosis (AS) after more than a decade of LRT, which required transcatheter aortic valve implantation. Given her marked hypoadiponectinemia and the LMNA variant, our patient might have been susceptible to progeria-associated disorders, including aortic stenosis, which could have been exaggerated by the prolonged 'imbalanced adipokines' caused by LRT between pro-inflammatory leptin and anti-inflammatory adiponectin. Thus, long-term LRT could be associated with AS in patients with the LMNA variant to cause generalized lipodystrophy-associated progeroid syndrome and hypoadiponectinemia.

Cost-Effectiveness of Management for Hospitalized Patients.

The cost and/or cost-effectiveness for inpatient management according to the gender of attending physicians remain to be elucidated.Hospitalization costs were extracted from the Diagnosis Procedure Combination (DPC) -based payment system. Using a dataset of 7,457 hospitalized patients with cardiovascular diseases in our hospital from 2012 to 2018, we compared the actual cost of inpatient management by female cardiologists with that by male cardiologists. Next, we estimated the cost-effectiveness of inpatient management according to the gender of the attending cardiologist. The cost of initial hospitalization per patient was similar between the patients treated by a female or male middle-grade cardiologist ($17,527 ± 14,158, versus $17,358 ± 15,183, P = 0.69). As an analysis on cost-effectiveness, the incremental cost of hospitalization managed by male middle-grade cardiologists was $67 per patient as compared with female middle-grade cardiologists. Concordantly, evaluation of the incremental cost-effectiveness ratio per quality-adjusted life year gained showed that the inpatient management by female cardiologists was dominant over that by male cardiologists.Inpatient management by female cardiologists was more cost-effective as compared with that by male cardiologists. Physician gender might have a considerable effect on medical economics.

Late-onset right ventricular failure after continuous-flow left ventricular assist device implantation: case presentation and review of the literature.

With the widespread use of implantable left ventricular assist device (LVAD), right ventricular failure (RVF) has become a serious problem that becomes apparent several weeks or later after LVAD implantation. However, there are no marked preoperative signs of RVF. This is called late-onset RVF and is currently a major problem leading to long-term complications following implantable LVAD use. Pathogenically, this could be the result of left ventricular suction by LVAD that causes the septum shift to the left ventricular side. This causes a change in morphology of the right ventricle, resulting in impaired right ventricular function. Aortic insufficiency and ventricular arrhythmia, which are also important as long-term complications after LVAD implantation, are considered to be closely involved in the onset and progression of RVF. Once late-onset RVF develops, exercise capacity declines and inotrope administration may be required. Late-onset RVF was also reported to be significantly associated with increased mortality. Several predictors of RVF have been proposed such as preoperative left ventricular diastolic dimension <64 mm, tricuspid valve annulus diameter ≥41 mm, and so on. However, some reports identified no predictors. The basic treatment strategy for late-onset RVF is to optimize volume status by administering diuretics and ensuring inotrope as needed. ß-blockers and antiarrhythmic agents often need to be reduced in terms of dosage or even discontinued because these might reduce right ventricular function. Although their efficacy is unclear, pulmonary vasodilators may be used to reduce right ventricular afterload. It is better to decrease the rotation speed of LVAD to minimize the displacement of the septum; however, this is often difficult because the required flow rate cannot be secured. Progress in the prevention and management of late-onset RVF is required because the number of patients who require longer-term LVAD support will increase with the spread of LVAD use as destination therapy.

A cotransformation system of the unicellular red alga Cyanidioschyzon merolae with blasticidin S deaminase and chloramphenicol acetyltransferase selectable markers.

BACKGROUND: The unicellular red alga Cyanidioschyzon merolae exhibits a very simple cellular and genomic architecture. In addition, procedures for genetic modifications, such as gene targeting by homologous recombination and inducible/repressible gene expression, have been developed. However, only two markers for selecting transformants, uracil synthase (URA) and chloramphenicol acetyltransferase (CAT), are available in this alga. Therefore, manipulation of two or more different chromosomal loci in the same strain in C. merolae is limited. RESULTS: This study developed a nuclear targeting and transformant selection system using an antibiotics blasticidin S (BS) and the BS deaminase (BSD) selectable marker by homologous recombination in C. merolae. In addition, this study has succeeded in simultaneously modifying two different chromosomal loci by a single-step cotransformation based on the combination of BSD and CAT selectable markers. A C. merolae strain that expresses mitochondrion-targeted mSCARLET (with the BSD marker) and mVENUS (with the CAT marker) from different chromosomal loci was generated with this procedure. CONCLUSIONS: The newly developed BSD selectable marker enables an additional genetic modification to the already generated C. merolae transformants based on the URA or CAT system. Furthermore, the cotransformation system facilitates multiple genetic modifications. These methods and the simple nature of the C. merolae cellular and genomic architecture will facilitate studies on several phenomena common to photosynthetic eukaryotes.

CZON-cutter - a CRISPR-Cas9 system for multiplexed organelle imaging in a simple unicellular alga.

The unicellular alga Cyanidioschyzon merolae has a simple cellular structure; each cell has one nucleus, one mitochondrion, one chloroplast and one peroxisome. This simplicity offers unique advantages for investigating organellar proliferation and the cell cycle. Here, we describe CZON-cutter, an engineered clustered, regularly interspaced, short palindromic repeats (CRISPR)/CRISPR-associated nuclease 9 (Cas9) system for simultaneous genome editing and organellar visualization. We engineered a C. merolae strain expressing a nuclear-localized Cas9-Venus nuclease for targeted editing of any locus defined by a single-guide RNA (sgRNA). We then successfully edited the algal genome and visualized the mitochondrion and peroxisome in transformants using fluorescent protein reporters with different excitation wavelengths. Fluorescent protein labeling of organelles in living transformants allows us to validate phenotypes associated with organellar proliferation and the cell cycle, even when the edited gene is essential. Combined with the exceptional biological features of C. merolae, CZON-cutter will be instrumental for investigating cellular and organellar division in a high-throughput manner. This article has an associated First Person interview with the first author of the paper.

An Autopsy Case of Pulmonary Veno-Occlusive Disease Complicated with Chronic Obstructive Pulmonary Disease and Severe Pulmonary Hypertension.

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory lung disease with obstructed airflow and frequently causes secondary mild-moderate pulmonary hypertension (PH). However, a low proportion (1%-5%) of COPD patients develop severe therapy-resistant PH, and it is crucial to determine whether the patient has another disease capable of causing severe PH, including pulmonary arterial hypertension.Here, we describe a case of a 71-year-old male with COPD complicated by severe PH and right heart failure. He had a history of heavy smoking and developed progressive hypoxemia on exertion. He had severe airflow limitation (forced expiratory volume % in one second, FEV 1.0% = 42.8%) with a markedly reduced diffusing capacity of the lung (predicted diffusion capacity of carbon monoxide, %DLCO = 29%), and high-resolution computed tomography (CT) demonstrated significant lung parenchymal abnormalities such as diffuse interlobular septal thickening, ground-glass opacities, and enlarged mediastinal lymph nodes. He was diagnosed with group 3 PH caused by COPD but resistant to the treatment of COPD, diuretics, and oxygen therapy. Pathohistological analysis of autopsy specimens revealed the coexistence of interstitial fibrosis and partial occlusion of the small intrapulmonary veins, which led to a conclusive diagnosis of pulmonary veno-occlusive disease (PVOD).Because of its rarity and similarity with idiopathic pulmonary arterial hypertension, PVOD is difficult to diagnose antemortem and has a poor prognosis. High-resolution CT findings (septal thickening, ground glass, and enlarged lymph nodes) and severely reduced DLCO should be carefully evaluated for the early detection and treatment of PVOD in COPD patients with severe PH.

Development of a Novel Nanoarchitecture of the Robust Photosystem I from a Volcanic Microalga Cyanidioschyzon merolae on Single Layer Graphene for Improved Photocurrent Generation.

Here, we report the development of a novel photoactive biomolecular nanoarchitecture based on the genetically engineered extremophilic photosystem I (PSI) biophotocatalyst interfaced with a single layer graphene via pyrene-nitrilotriacetic acid self-assembled monolayer (SAM). For the oriented and stable immobilization of the PSI biophotocatalyst, an His6-tag was genetically engineered at the N-terminus of the stromal PsaD subunit of PSI, allowing for the preferential binding of this photoactive complex with its reducing side towards the graphene monolayer. This approach yielded a novel robust and ordered nanoarchitecture designed to generate an efficient direct electron transfer pathway between graphene, the metal redox center in the organic SAM and the photo-oxidized PSI biocatalyst. The nanosystem yielded an overall current output of 16.5 µA·cm-2 for the nickel- and 17.3 µA·cm-2 for the cobalt-based nanoassemblies, and was stable for at least 1 h of continuous standard illumination. The novel green nanosystem described in this work carries the high potential for future applications due to its robustness, highly ordered and simple architecture characterized by the high biophotocatalyst loading as well as simplicity of manufacturing.

Cell size for commitment to cell division and number of successive cell divisions in cyanidialean red algae.

Several eukaryotic cell lineages proliferate by multiple fission cell cycles, during which cells grow to manyfold of their original size, then undergo several rounds of cell division without intervening growth. A previous study on volvocine green algae, including both unicellular and multicellular (colonial) species, showed a correlation between the minimum number of successive cell divisions without intervening cellular growth, and the threshold cell size for commitment to the first round of successive cell divisions: two times the average newly born daughter cell volume for unicellular Chlamydomonas reinhardtii, four times for four-celled Tetrabaena socialis, in which each cell in the colony produces a daughter colony by two successive cell divisions, and eight times for the eight-celled Gonium pectorale, in which each cell produces a daughter colony by three successive cell divisions. To assess whether this phenomenon is also applicable to other lineages, we have characterized cyanidialean red algae, namely, Cyanidioschyzon merolae, which proliferates by binary fission, as well as Cyanidium caldarium and Galdieria sulphuraria, which form up to four and 32 daughter cells (autospores), respectively, in a mother cell before hatching out. The result shows that there is also a correlation between the number of successive cell divisions and the threshold cell size for cell division or the first round of the successive cell divisions. In both C. merolae and C. caldarium, the cell size checkpoint for cell division(s) exists in the G1-phase, as previously shown in volvocine green algae. When C. merolae cells were arrested in the G1-phase and abnormally enlarged by conditional depletion of CDKA, the cells underwent two or more successive cell divisions without intervening cellular growth after recovery of CDKA, similarly to C. caldarium and G. sulphuraria. These results suggest that the threshold size for cell division is a major factor in determining the number of successive cell divisions and that evolutionary changes in the mechanism of cell size monitoring resulted in a variation of multiple fission cell cycle in eukaryotic algae.

CXCR7 ameliorates myocardial infarction as a ß-arrestin-biased receptor.

Most seven transmembrane receptors (7TMRs) are G protein-coupled receptors; however, some 7TMRs evoke intracellular signals through ß-arrestin as a biased receptor. As several ß-arrestin-biased agonists have been reported to be cardioprotective, we examined the role of the chemokine receptor CXCR7 as a ß-arrestin-biased receptor in the heart. Among 510 7TMR genes examined, Cxcr7 was the most abundantly expressed in the murine heart. Single-cell RNA-sequencing analysis revealed that Cxcr7 was abundantly expressed in cardiomyocytes and fibroblasts. Cardiomyocyte-specific Cxcr7 null mice showed more prominent cardiac dilatation and dysfunction than control mice 4 weeks after myocardial infarction. In contrast, there was no difference in cardiac phenotypes between fibroblast-specific Cxcr7-knockout mice and control mice even after myocardial infarction. TC14012, a specific agonist of CXCR7, significantly recruited ß-arrestin to CXCR7 in CXCR7-expressing cells and activated extracellular signal-regulated kinase (ERK) in neonatal rat cardiomyocytes. Cxcr7 expression was significantly increased and ERK was activated in the border zone of the heart in control, but not Cxcr7 null mice. These results indicate that the abundantly expressed CXCR7 in cardiomyocytes may play a protective role in the heart as a ß-arrestin-biased receptor and that CXCR7 may be a novel therapeutic target for myocardial infarction.