Sox6 as a new modulator of renin expression in the kidney

Four-week inhibition of the renin-angiotensin system in spontaneously hypertensive rats results in persistently lower blood pressure with reduced kidney renin and changes in expression of relevant gene networks

AIMS

Prevention of human hypertension is an important challenge and has been achieved in experimental models. Brief treatment with renin-angiotensin system (RAS) inhibitors permanently reduces the genetic hypertension of the spontaneously hypertensive rat (SHR). The kidney is involved in this fascinating phenomenon, but relevant changes in gene expression are unknown.

METHODS AND RESULTS

In SHR, we studied the effect of treatment between 10 and 14 weeks of age with the angiotensin receptor blocker, losartan, or the angiotensin-converting enzyme inhibitor, perindopril [with controls for non-specific effects of lowering blood pressure (BP)], on differential RNA expression, DNA methylation, and renin immunolabelling in the kidney at 20 weeks of age. RNA sequencing revealed a six-fold increase in renin gene (Ren) expression during losartan treatment (P < 0.0001). Six weeks after losartan, arterial pressure remained lower (P = 0.006), yet kidney Ren showed reduced expression by 23% after losartan (P = 0.03) and by 43% after perindopril (P = 1.4 × 10-6) associated with increased DNA methylation (P = 0.04). Immunolabelling confirmed reduced cortical renin after earlier RAS blockade (P = 0.002). RNA sequencing identified differential expression of mRNAs, miRNAs, and lncRNAs with evidence of networking and co-regulation. These included 13 candidate genes (Grhl1, Ammecr1l, Hs6st1, Nfil3, Fam221a, Lmo4, Adamts1, Cish, Hif3a, Bcl6, Rad54l2, Adap1, Dok4), the miRNA miR-145-3p, and the lncRNA AC115371. Gene ontogeny analyses revealed that these networks were enriched with genes relevant to BP, RAS, and the kidneys.

CONCLUSION

Early RAS inhibition in SHR resets genetic pathways and networks resulting in a legacy of reduced Ren expression and BP persisting for a minimum of 6 weeks.

Integrative single-cell characterization of a frugivorous and an insectivorous bat kidney and pancreas

Frugivory evolved multiple times in mammals, including bats. However, the cellular and molecular components driving it remain largely unknown. Here, we use integrative single-cell sequencing (scRNA-seq and scATAC-seq) on insectivorous (Eptesicus fuscus; big brown bat) and frugivorous (Artibeus jamaicensis; Jamaican fruit bat) bat kidneys and pancreases and identify key cell population, gene expression and regulatory differences associated with the Jamaican fruit bat that also relate to human disease, particularly diabetes. We find a decrease in loop of Henle and an increase in collecting duct cells, and differentially active genes and regulatory elements involved in fluid and electrolyte balance in the Jamaican fruit bat kidney. The Jamaican fruit bat pancreas shows an increase in endocrine and a decrease in exocrine cells, and differences in genes and regulatory elements involved in insulin regulation. We also find that these frugivorous bats share several molecular characteristics with human diabetes. Combined, our work provides insights from a frugivorous mammal that could be leveraged for therapeutic purposes.

A systems biology approach identifies the role of dysregulated PRDM6 in the development of hypertension

Genetic variants in the third intron of the PRDM6 gene have been associated with BP traits in multiple GWAS. By combining fine mapping, massively parallel reporter assays, and gene editing, we identified super enhancers that drive the expression of PRDM6 and are partly regulated by STAT1 as the causal variants for hypertension. The heterozygous disruption of Prdm6 in mice expressing Cre recombinase under the control of mouse smooth muscle cell protein 22-α promoter (Prdm6fl/+ SM22-Cre) exhibited a markedly higher number of renin-producing cells in the kidneys at E18.5 compared with WT littermates and developed salt-induced systemic hypertension that was completely responsive to the renin inhibitor aliskiren. Strikingly, RNA-Seq analysis of the mouse aortas identified a network of PRDM6-regulated genes that are located in GWAS-associated loci for blood pressure, most notably Sox6, which modulates renin expression in the kidney. Accordingly, the smooth muscle cell-specific disruption of Sox6 in Prdm6fl/+ SM22-Cre mice resulted in a dramatic reduction of renin. Fate mapping and histological studies also showed increased numbers of neural crest-derived cells accompanied by increased collagen deposition in the kidneys of Prdm6fl/+ Wnt1Cre-ZsGreen1Cre mice compared with WT mice. These findings establish the role of PRDM6 as a regulator of renin-producing cell differentiation into smooth muscle cells and as an attractive target for the development of antihypertensive drugs.

The contribution of common and rare genetic variants to variation in metabolic traits in 288,137 East Asians

Metabolic traits are heritable phenotypes widely-used in assessing the risk of various diseases. We conduct a genome-wide association analysis (GWAS) of nine metabolic traits (including glycemic, lipid, liver enzyme levels) in 125,872 Korean subjects genotyped with the Korea Biobank Array. Following meta-analysis with GWAS from Biobank Japan identify 144 novel signals (MAF ≥ 1%), of which 57.0% are replicated in UK Biobank. Additionally, we discover 66 rare (MAF < 1%) variants, 94.4% of them co-incident to common loci, adding to allelic series. Although rare variants have limited contribution to overall trait variance, these lead, in carriers, substantial loss of predictive accuracy from polygenic predictions of disease risk from common variant alone. We capture groups with up to 16-fold variation in type 2 diabetes (T2D) prevalence by integration of genetic risk scores of fasting plasma glucose and T2D and the I349F rare protective variant. This study highlights the need to consider the joint contribution of both common and rare variants on inherited risk of metabolic traits and related diseases.

lncRNA KCNQ1OT1 regulated high glucose-induced proliferation, oxidative stress, extracellular matrix accumulation, and inflammation by miR-147a/SOX6 in diabetic nephropathy (DN)

Long non-coding RNAs (lncRNAs) have been proved to play critical roles in diabetic nephropathy (DN). This study aimed to investigate the functions and underlying mechanism of potassium voltage-gated channel subfamily Q member 1 overlapping transcript 1 (KCNQ1OT1) in DN. Blood samples were obtained from 33 DN patients and 30 healthy volunteers. Kidney biopsies tissues of DN patients (n = 10) and patients with normal kidney morphology (n = 10) were collected. We found that KCNQ1OT1 was markedly overexpressed in the blood and kidney biopsies tissues of DN patients, as well as in high glucose (HG)-cultured human glomerular mesangial (HGMC) cells. Knockdown of KCNQ1OT1 suppressed proliferation, extracellular matrix (ECM) accumulation, inflammation, and oxidative stress in HG-treated HGMC cells in vitro. KCNQ1OT1 functioned as a sponge for microRNA-147a (miR-147a), and SRY-Box Transcription Factor 6 (SOX6) was directly targeted by miR-147a. Downregulation of miR-147a or upregulation of SOX6 partly overturned the prohibitive effects of KCNQ1OT1 knockdown or miR-147a overexpression on proliferation, ECM accumulation, inflammation, and oxidative stress in HG-treated HGMC cells. Altogether, KCNQ1OT1 mediated the proliferation, ECM accumulation, inflammation, and oxidative stress in HG-treated HGMC cells via miR-147a/SOX6 axis, which might be a novel target for DN therapy.

Flexible and multifaceted: the plasticity of renin-expressing cells

The protease renin, the key enzyme of the renin–angiotensin–aldosterone system, is mainly produced and secreted by juxtaglomerular cells in the kidney, which are located in the walls of the afferent arterioles at their entrance into the glomeruli. When the body’s demand for renin rises, the renin production capacity of the kidneys commonly increases by induction of renin expression in vascular smooth muscle cells and in extraglomerular mesangial cells. These cells undergo a reversible metaplastic cellular transformation in order to produce renin. Juxtaglomerular cells of the renin lineage have also been described to migrate into the glomerulus and differentiate into podocytes, epithelial cells or mesangial cells to restore damaged cells in states of glomerular disease. More recently, it could be shown that renin cells can also undergo an endocrine and metaplastic switch to erythropoietin-producing cells. This review aims to describe the high degree of plasticity of renin-producing cells of the kidneys and to analyze the underlying mechanisms.

The Transcription Factor Sox6 Controls Renin Expression during Renal Artery Stenosis

Background

Renal artery stenosis (RAStenosis) or renal artery occlusion is an intractable problem affecting about 6% of people >65 and up to 40% of people with coronary or peripheral vascular disease in the Unites States. The renal renin-angiotensin-aldosterone system plays a key role in RAStenosis, with renin (which is mainly produced in the kidney) being recognized as the driver of the disease. In this study, we will determine a new function for the transcription factor Sox6 in the control of renal renin during RAStenosis.

Methods

We hypothesize that knocking out Sox6 in Ren1d-positive cells will protect mice against renovascular hypertension and kidney injury. To test our hypothesis, we used a new transgenic mouse model, Ren1dcre/Sox6fl/fl (Sox6 KO), in which Sox6 is knocked out in renin-expressing cells. We used a modified two-kidney, one-clip (2K1C) Goldblatt mouse model to induce RAStenosis and renovascular hypertension. BP was measured using the tail-cuff method. Renin, prorenin, Sox6, and NGAL expressions levels were measured with Western blot, in situ hybridization, and immunohistochemistry. Creatinine levels were measured using the colorimetric assay.

Results

Systolic BP was significantly lower in Sox6 KO 2 weeks after RAStenosis compared with Sox6 WT (Ren1dcre/Sox6wt/wt). Renin, prorenin, and NGAL expression levels in the stenosed kidney were lower in Sox6 KO compared with Sox6 WT mice. Furthermore, creatinine clearance was preserved in Sox6 KO compared with Sox6 WT mice.

Conclusions

Our data indicate that Sox6 controls renal renin and prorenin expression and, as such, has a function in renovascular hypertension induced by RAStenosis. These results point to a novel transcriptional regulatory network controlled by Sox6.

Pathophysiology of Hypertension: The Mosaic Theory and Beyond

Dr Irvine Page proposed the Mosaic Theory of Hypertension in the 1940s advocating that hypertension is the result of many factors that interact to raise blood pressure and cause end-organ damage. Over the years, Dr Page modified his paradigm, and new concepts regarding oxidative stress, inflammation, genetics, sodium homeostasis, and the microbiome have arisen that allow further refinements of the Mosaic Theory. A constant feature of this approach to understanding hypertension is that the various nodes are interdependent and that these almost certainly vary between experimental models and between individuals with hypertension. This review discusses these new concepts and provides an introduction to other reviews in this compendium of Circulation Research.

Renal interstitial fibroblasts coproduce erythropoietin and renin under anaemic conditions

BACKGROUND

Erythrocyte mass contributes to maintaining systemic oxygen delivery and blood viscosity, with the latter being one of the determinants of blood pressure. However, the physiological response to blood pressure changes under anaemic conditions remain unknown.

METHODS AND FINDINGS

We show that anaemia decreases blood pressure in human patients and mouse models. Analyses of pathways related to blood pressure regulation demonstrate that anaemia enhances the expression of the gene encoding the vasopressor substance renin in kidneys. Although kidney juxtaglomerular cells are known to continuously produce renin, renal interstitial fibroblasts are identified in the present study as a novel site of renin induction under anaemic hypotensive conditions in mice and rats. Notably, some renal interstitial fibroblasts are found to simultaneously express renin and the erythroid growth factor erythropoietin in the anaemic mouse kidney. Antihypertensive agents but not hypoxic stimuli induced interstitial renin expression, suggesting that blood pressure reduction triggers interstitial renin induction in anaemic mice. The interstitial renin expression was also detected in injured fibrotic kidneys of the mouse and human, and the renin-expressing interstitial cells in murine fibrotic kidneys were identified as myofibroblasts originating from renal interstitial fibroblasts. Since the elevated expression levels of renin in fibrotic kidneys along with progression of renal fibrosis were well correlated to the systemic blood pressure increase, the renal interstitial renin production seemed to affect systemic blood pressure.

INTERPRETATION

Renal interstitial fibroblasts function as central controllers of systemic oxygen delivery by producing both renin and erythropoietin.

FUNDING

Grants-in-Aid from Japan Society for the Promotion of Science (JSPS) KAKENHI (17K19680, 15H04691, and 26111002) and the Takeda Science Foundation.

Emerging roles of Sox6 in the renal and cardiovascular system

The function of Sex-determining Region Y (SRY)-related high-mobility-group box (Sox) family of transcription factors in cell fate decisions during embryonic development are well-established. Accumulating evidence indicates that the Sox family of transcription factors are fundamental in adult tissue homeostasis, regeneration, and physiology. The SoxD subfamily of genes are expressed in various cell types of different organs during embryogenesis and adulthood and have been involved in cell-fate determination, cellular proliferation and survival, differentiation, and terminal maturation in a number of cell lineages. The dysregulation in the function of SoxD proteins (i.e. Sox5, Sox6, Sox13, and Sox23) have been implicated in different disease conditions such as chondrodysplasia, cancer, diabetes, hypertension, autoimmune diseases, osteoarthritis among others. In this minireview, we present recent developments related to the transcription factor Sox6, which is involved in a number of diseases such as diabetic nephropathy, adipogenesis, cardiomyopathy, inflammatory bowel disease, and cancer. Sox6 has been implicated in the regulation of renin expression and JG cell recruitment in mice during sodium depletion and dehydration. We provide a current perspective of Sox6 research developments in last five years, and the implications of Sox6 functions in cardiovascular physiology and disease conditions.