Sox7 Regulates Lineage Decisions in Cardiovascular Progenitor Cells

Genome-wide identification and expression analysis of the Sox gene family in bivalves

Since the discovery of the Sox gene family in 1990, research on its distribution, classification, characterization, and function across various species has been significantly deepened. However, the Sox gene family has not yet been systematically and comprehensively analyzed in bivalves. In this study, 254 Sox genes were identified in 51 bivalves (covering 20 orders and 37 families). The Sox gene numbers ranged from 1 and 10 in most bivalves but no Sox gene was identified in the transcriptomes of Poromya illevis (Poromyoidea), Thracia phaseolina (Thracioidea), Solen vaginoides (Solenoidea), Lamychaena hians (Gastrochaenoidea), and Limopsis sp. and Solemya velesiana (Limopsoidea). The phylogenetic analyses revealed that Sox genes in bivalves are divided into 7 primary groups: SoxB1, SoxB2, SoxC, SoxD, SoxE, SoxF, and SoxH, with different groups exhibiting distinct conserved motif patterns. Notably, SoxA and SoxG found in most vertebrates were not identified in bivalves. Moreover, through spatiotemporal expression profiling in 6 distinct bivalve species, it was determined that the SoxH genes exhibit male-biased expression mainly in non-hermaphroditic bivalves, while SoxB1 and SoxC genes demonstrate female-biased expression, and these two Sox genes may serve a pivotal role in embryonic development stage and SoxB2, SoxC and SoxE may play a significant impact in neural development in bivalves. Sox family members also appear to possess disparate functions across different species and tissues. Overall, this study may provide a basis for future investigations into the functions and evolution of Sox genes in bivalves, and offer new perspectives on their roles in development in bivalves.

Deficiency of Sox7 leads to congenital aortic stenosis via abnormal valve remodeling

Abnormal valve development is the most common congenital heart malformation. The transcription factor Sox7 plays a critical role in the development of vascular and cardiac septation. However, it remains unclear whether Sox7 is required for heart valve development. In the present study, Sox7 was strongly expressed in the endocardial and mesenchymal cells of the developing aortic valve in mice and humans, and that endocardial cell specific deletion of Sox7 (Nfatc1 Cre;Sox7fl/fl) in mice leads to congenital aortic stenosis basing on our echocardiography data and multiple staining results. Mechanistically, Sox7 influences extracellular matrix (ECM) remodeling of the valve through regulating MMP9. Meanwhile, Sox7 also affects other valvular remodeling processes, including apoptosis and proliferation of valvular cells in Sox7 deficiency mice. Similarly, in valvular interstitial cells (VICs), Sox7 overexpression increased the protein levels of cleaved caspase3 and TUNEL-positive VICs, while Ki67-positive VICs decreased. The reverse trend was observed in VICs with Sox7 deficiency. Significant enhancement of Rbm25 transcriptional levels was observed in the Sox7 overexpression group, and the mRNA and protein levels of calcification markers such as Osterix, Osteopontin and Runx2 were reduced. The reverse trend was observed in VICs with Sox7 deficiency. Von Kossa staining and Alizarin Red staining also demonstrated that sever calcification in Nfatc1 Cre;Sox7fl/fl mice. Moreover, we detected the Sox7 protein expression in human fetal aortic valves in patients with aortic stenosis, in which Sox7 positive mesenchymal cells were decreased. Taken together, these findings identify Sox7 as a potential pathogenic gene responsible for congenital aortic stenosis in human. Our study provides novel strategies for the diagnosis and treatment of congenital valvular malformation.

Dissecting SOX2 expression and function reveals an association with multiple signaling pathways during embryonic development and in cancer progression

SRY (Sex Determining Region) box 2 (SOX2) is an essential transcription factor that plays crucial roles in activating genes involved in pre- and post-embryonic development, adult tissue homeostasis, and lineage specifications. SOX2 maintains the self-renewal property of stem cells and is involved in the generation of induced pluripotency stem cells. SOX2 protein contains a particular high-mobility group domain that enables SOX2 to achieve the capacity to participate in a broad variety of functions. The information about the involvement of SOX2 with gene regulatory elements, signaling networks, and microRNA is gradually emerging, and the higher expression of SOX2 is functionally relevant to various cancer types. SOX2 facilitates the oncogenic phenotype via cellular proliferation and enhancement of invasive tumor properties. Evidence are accumulating in favor of three dimensional (higher order) folding of chromatin and epigenetic control of the SOX2 gene by chromatin modifications, which implies that the expression level of SOX2 can be modulated by epigenetic regulatory mechanisms, specifically, via DNA methylation and histone H3 modification. In view of this, and to focus further insights into the roles SOX2 plays in physiological functions, involvement of SOX2 during development, precisely, the advances of our knowledge in pre- and post-embryonic development, and interactions of SOX2 in this scenario with various signaling pathways in tumor development and cancer progression, its potential as a therapeutic target against many cancers are summarized and discussed in this article.

Platelet extracellular vesicles preserve lymphatic endothelial cell integrity and enhance lymphatic vessel function

Lymphatic vessels are essential for preventing the accumulation of harmful components within peripheral tissues, including the artery wall. Various endogenous mechanisms maintain adequate lymphatic function throughout life, with platelets being essential for preserving lymphatic vessel integrity. However, since lymph lacks platelets, their impact on the lymphatic system has long been viewed as restricted to areas where lymphatics intersect with blood vessels. Nevertheless, platelets can also exert long range effects through the release of extracellular vesicles (EVs) upon activation. We observed that platelet EVs (PEVs) are present in lymph, a compartment to which they could transfer regulatory effects of platelets. Here, we report that PEVs in lymph exhibit a distinct signature enabling them to interact with lymphatic endothelial cells (LECs). In vitro experiments show that the internalization of PEVs by LECs maintains their functional integrity. Treatment with PEVs improves lymphatic contraction capacity in atherosclerosis-prone mice. We suggest that boosting lymphatic pumping with exogenous PEVs offers a novel therapeutic approach for chronic inflammatory diseases characterized by defective lymphatics.

Direct programming of human pluripotent stem cells into endothelial progenitors with SOX17 and FGF2

Transcription factors (TFs) are pivotal in guiding stem cell behavior, including their maintenance and differentiation. Using single-cell RNA sequencing, we investigated TFs expressed in endothelial progenitors (EPs) derived from human pluripotent stem cells (hPSCs) and identified upregulated expression of SOXF factors SOX7, SOX17, and SOX18 in the EP population. To test whether overexpression of these factors increases differentiation efficiency, we established inducible hPSC lines for each SOXF factor and found only SOX17 overexpression robustly increased the percentage of cells expressing CD34 and vascular endothelial cadherin (VEC). Conversely, SOX17 knockdown via CRISPR-Cas13d significantly compromised EP differentiation. Intriguingly, we discovered SOX17 overexpression alone was sufficient to generate CD34+VEC+CD31- cells, and, when combined with FGF2 treatment, more than 90% of CD34+VEC+CD31+ EP was produced. These cells are capable of further differentiating into endothelial cells. These findings underscore an undiscovered role of SOX17 in programming hPSCs toward an EP lineage, illuminating pivotal mechanisms in EP differentiation.

Transcription factors regulating vasculogenesis and angiogenesis

Transcription factors (TFs) play a crucial role in regulating the dynamic and precise patterns of gene expression required for the initial specification of endothelial cells (ECs), and during endothelial growth and differentiation. While sharing many core features, ECs can be highly heterogeneous. Differential gene expression between ECs is essential to pattern the hierarchical vascular network into arteries, veins and capillaries, to drive angiogenic growth of new vessels, and to direct specialization in response to local signals. Unlike many other cell types, ECs have no single master regulator, instead relying on differing combinations of a necessarily limited repertoire of TFs to achieve tight spatial and temporal activation and repression of gene expression. Here, we will discuss the cohort of TFs known to be involved in directing gene expression during different stages of mammalian vasculogenesis and angiogenesis, with a primary focus on development.

Sox7-positive endothelial progenitors establish coronary arteries and govern ventricular compaction

The cardiac endothelium influences ventricular chamber development by coordinating trabeculation and compaction. However, the endothelial-specific molecular mechanisms mediating this coordination are not fully understood. Here, we identify the Sox7 transcription factor as a critical cue instructing cardiac endothelium identity during ventricular chamber development. Endothelial-specific loss of Sox7 function in mice results in cardiac ventricular defects similar to non-compaction cardiomyopathy, with a change in the proportions of trabecular and compact cardiomyocytes in the mutant hearts. This phenotype is paralleled by abnormal coronary artery formation. Loss of Sox7 function disrupts the transcriptional regulation of the Notch pathway and connexins 37 and 40, which govern coronary arterial specification. Upon Sox7 endothelial-specific deletion, single-nuclei transcriptomics analysis identifies the depletion of a subset of Sox9/Gpc3-positive endocardial progenitor cells and an increase in erythro-myeloid cell lineages. Fate mapping analysis reveals that a subset of Sox7-null endothelial cells transdifferentiate into hematopoietic but not cardiomyocyte lineages. Our findings determine that Sox7 maintains cardiac endothelial cell identity, which is crucial to the cellular cross-talk that drives ventricular compaction and coronary artery development.

Vitamin D receptor cross-talk with p63 signaling promotes epidermal cell fate

The vitamin D receptor with its ligand 1,25 dihydroxy vitamin D3 (1,25D3) regulates epidermal stem cell fate, such that VDR removal from Krt14 expressing keratinocytes delays re-epithelialization of epidermis after wound injury in mice. In this study we deleted Vdr from Lrig1 expressing stem cells in the isthmus of the hair follicle then used lineage tracing to evaluate the impact on re-epithelialization following injury. We showed that Vdr deletion from these cells prevents their migration to and regeneration of the interfollicular epidermis without impairing their ability to repopulate the sebaceous gland. To pursue the molecular basis for these effects of VDR, we performed genome wide transcriptional analysis of keratinocytes from Vdr cKO and control littermate mice. Ingenuity Pathway analysis (IPA) pointed us to the TP53 family including p63 as a partner with VDR, a transcriptional factor that is essential for proliferation and differentiation of epidermal keratinocytes. Epigenetic studies on epidermal keratinocytes derived from interfollicular epidermis showed that VDR is colocalized with p63 within the specific regulatory region of MED1 containing super-enhancers of epidermal fate driven transcription factor genes such as Fos and Jun. Gene ontology analysis further implicated that Vdr and p63 associated genomic regions regulate genes involving stem cell fate and epidermal differentiation. To demonstrate the functional interaction between VDR and p63, we evaluated the response to 1,25(OH)2D3 of keratinocytes lacking p63 and noted a reduction in epidermal cell fate determining transcription factors such as Fos, Jun. We conclude that VDR is required for the epidermal stem cell fate orientation towards interfollicular epidermis. We propose that this role of VDR involves cross-talk with the epidermal master regulator p63 through super-enhancer mediated epigenetic dynamics.

The mechanism by which crocetin regulates the lncRNA NEAT1/miR-125b-5p/SOX7 molecular axis to inhibit high glucose-induced diabetic retinopathy

Diabetic retinopathy (DR) is a high-incidence microvascular complication with retinal neovascularization that generates irreversible visual impairment. However, the mechanism of DR is unclear and needs to be further explored. To explore the expression of NEAT1 and miR-125b-5p and the proliferation activity, migration ability, and angiogenesis ability of human retinal microvascular endothelial cells (hRMECs), RT-qPCR, CCK-8, Transwell, and tube formation assays were performed. Additionally, western blotting was used to detect the expression of SOX7, VEGFA and CD31. Furthermore, a dual-luciferase reporter gene was used to verify the targeting connection. The DR mouse model was constructed by STZ. The effect of crocetin on DR angiogenesis was detected by hematoxylin-eosin (HE) staining, immunohistochemistry (IHC), retinal digest preparations and Western blotting. The results showed that crocetin inhibited the high-glucose (Hg)-induced upregulation of NEAT1 and SOX7 and the downregulation of miR-125b-5p. Crocetin inhibited Hg-induced proliferation, migration and angiogenesis by upregulating the targeted inhibition of SOX7 by miR-125b-5p through the inhibition of NEAT1. To summarize, our study revealed that crocetin has a protective effect against Hg-induced DR by regulating the lncRNA NEAT1/miR-125b-5p/SOX7 molecular axis.

Predisposition to atrioventricular septal defects may be caused by SOX7 variants that impair interaction with GATA4

Atrioventricular septal defects (AVSD) are a complicated subtype of congenital heart defects for which the genetic basis is poorly understood. Many studies have demonstrated that the transcription factor SOX7 plays a pivotal role in cardiovascular development. However, whether SOX7 single nucleotide variants are involved in AVSD pathogenesis is unclear. To explore the potential pathogenic role of SOX7 variants, we recruited a total of 100 sporadic non-syndromic AVSD Chinese Han patients and screened SOX7 variants in the patient cohort by targeted sequencing. Functional assays were performed to evaluate pathogenicity of nonsynonymous variants of SOX7. We identified three rare SOX7 variants, c.40C > G, c.542G > A, and c.743C > T, in the patient cohort, all of which were found to be highly conserved in mammals. Compared to the wild type, these SOX7 variants had increased mRNA expression and decreased protein expression. In developing hearts, SOX7 and GATA4 were highly expressed in the region of atrioventricular cushions. Moreover, SOX7 overexpression promoted the expression of GATA4 in human umbilical vein endothelial cells. A chromatin immunoprecipitation assay revealed that SOX7 could directly bind to the GATA4 promoter and luciferase assays demonstrated that SOX7 activated the GATA4 promoter. The SOX7 variants had impaired transcriptional activity relative to wild-type SOX7. Furthermore, the SOX7 variants altered the ability of GATA4 to regulate its target genes. In conclusion, our findings showed that deleterious SOX7 variants potentially contribute to human AVSD by impairing its interaction with GATA4. This study provides novel insights into the etiology of AVSD and contributes new strategies to the prenatal diagnosis of AVSD.

Clinical and genomic characterization of 8p cytogenomic disorders

PURPOSE

To provide a detailed clinical and cytogenomic summary of individuals with chromosome 8p rearrangements of invdupdel(8p), del(8p), and dup(8p).

METHODS

We enrolled 97 individuals with invdupdel(8p), del(8p), and dup(8p). Clinical and molecular data were collected to delineate and compare the clinical findings and rearrangement breakpoints. We included additional 5 individuals with dup(8p) from the literature for a total of 102 individuals.

RESULTS

Eighty-one individuals had recurrent rearrangements of invdupdel(8p) (n = 49), del(8p)_distal (n = 4), del(8p)_proximal (n = 9), del(8p)_proximal&distal (n = 12), and dup(8p)_proximal (n = 7). Twenty-one individuals had nonrecurrent rearrangements. While all individuals had neurodevelopmental features, the frequency and severity of clinical findings were higher in individuals with invdupdel(8p), and with larger duplications. All individuals with GATA4 deletion had structural congenital heart defects; however, the presence of structural heart defects in some individuals with normal GATA4 copy number suggests there are other potentially contributing gene(s) on 8p.

CONCLUSION

Our study may inform families and health-care providers about the associated clinical findings and severity in individuals with chromosome 8p rearrangements, and guide researchers in investigating the underlying molecular and biological mechanisms by providing detailed clinical and cytogenomic information about individuals with distinct 8p rearrangements.

Systematic identification and expression analysis of the Sox gene family in spotted sea bass (Lateolabrax maculatus)

The Sox gene family encodes a set of transcription factors characterized by a conserved Sry-related high mobility group (HMG)-box domain, which performs a series of essential biological functions in diverse tissues and developmental processes. In this study, the Sox gene family was systematically characterized in spotted sea bass (Lateolabrax maculatus). A total of 26 Sox genes were identified and classified into eight subfamilies, namely, SoxB1, SoxB2, SoxC, SoxD, SoxE, SoxF, SoxH and SoxK. The phylogenetic relationship, exon-intron and domain structure analyses supported their annotation and classification. Comparison of gene copy numbers and chromosome locations among different species indicated that except tandem duplicated paralogs of Sox17/Sox32, duplicated Sox genes in spotted sea bass were generated from teleost-specific whole genome duplication during evolution. In addition, qRT-PCR was performed to detect the expression profiles of Sox genes during development and adulthood. The results showed that the expression of 16 out of 26 Sox genes was induced dramatically at different starting points after the multicellular stage, which is consistent with embryogenesis. At the early stage of sex differentiation, 9 Sox genes exhibited sexually dimorphic expression patterns, among which Sox3, Sox19 and Sox6b showed the most significant ovary-biased expression. Moreover, the distinct expression pattern of Sox genes was observed in different adult tissues. Our results provide a fundamental resource for further investigating the functions of Sox genes in embryonic processes, sex determination and differentiation as well as controlling the homeostasis of adult tissues in spotted sea bass.

ROBO2 signaling in lung development regulates SOX2/SOX9 balance, branching morphogenesis and is dysregulated in nitrofen-induced congenital diaphragmatic hernia

Background

Characterized by abnormal lung growth or maturation, congenital diaphragmatic hernia (CDH) affects 1:3000 live births. Cellular studies report proximal (SOX2⁺) and distal (SOX9⁺) progenitor cells as key modulators of branching morphogenesis and epithelial differentiation, whereas transcriptome studies demonstrate ROBO/SLIT as potential therapeutic targets for diaphragm defect repair in CDH. In this study, we tested the hypothesis that (a) experimental-CDH could changes the expression profile of ROBO1, ROBO2, SOX2 and SOX9; and (b) ROBO1 or ROBO2 receptors are regulators of branching morphogenesis and SOX2/SOX9 balance.

Methods

The expression profile for receptors and epithelial progenitor markers were assessed by Western blot and immunohistochemistry in a nitrofen-induced CDH rat model. Immunohistochemistry signals by pulmonary structure were also quantified from embryonic-to-saccular stages in normal and hypoplastic lungs. Ex vivo lung explant cultures were harvested at E13.5, cultures during 4 days and treated with increasing doses of recombinant rat ROBO1 or human ROBO2 Fc Chimera proteins for ROBO1 and ROBO2 inhibition, respectively. The lung explants were analyzed morphometrically and ROBO1, ROBO2, SOX2, SOX9, BMP4, and β-Catenin were quantified by Western blot.

Results

Experimental-CDH induces distinct expression profiles by pulmonary structure and developmental stage for both receptors (ROBO1 and ROBO2) and epithelial progenitor markers (SOX2 and SOX9) that provide evidence of the impairment of proximodistal patterning in experimental-CDH. Ex vivo functional studies showed unchanged branching morphogenesis after ROBO1 inhibition; increased fetal lung growth after ROBO2 inhibition in a mechanism-dependent on SOX2 depletion and overexpression of SOX9, non-phospho β-Catenin, and BMP4.

Conclusions

These studies provided evidence of receptors and epithelial progenitor cells which are severely affected by CDH-induction from embryonic-to-saccular stages and established the ROBO2 inhibition as promoter of branching morphogenesis through SOX2/SOX9 balance.

Rapamycin Promotes Cardiomyocyte Differentiation of Human Induced Pluripotent Stem Cells in a Stage-Dependent Manner

Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) are a promising source for cardiac regenerative therapy, and ideal for in vitro cell modeling of cardiovascular diseases and drug screening. Recent studies have shown that rapamycin can promote cardiomyocyte differentiation in various stem cells. However, how rapamycin affects cardiomyocyte differentiation of iPSCs is still not fully understood. This study aimed to investigate the effect of rapamycin on cardiomyocyte differentiation based on embryoid body (EB) method. First, to determine the autophagy induction protocol, different concentrations of rapamycin were applied in hEBs on day 6. The autophagy was most significant when applying rapamycin at 1 μM for 48 h, demonstrating by the LC3II/LC3I ratio and p62 expression. Then, 1 μM rapamycin was applied for 48 h at different time points of cardiomyocyte differentiation to investigate the role of rapamycin in this process. Compared with control, rapamycin applied on days 0-4 of differentiation significantly decreased the proportion of beating EBs and expression of cardiomyocyte-specific genes, while rapamycin applied on days 4-14 significantly increased them. Among all groups, rapamycin applied on days 4-6 achieved highest cardiomyocyte differentiation efficiency. Furthermore, using autophagy inhibitor NH₄Cl and GSK-3β inhibitor CHIR-99021, we found rapamycin-induced autophagy promoted cardiomyocyte differentiation at middle stage by negatively regulating the Wnt/β-catenin signaling pathway. These results suggest that rapamycin regulates EB-based cardiomyocyte differentiation in a stage-dependent manner, and the negative regulation of Wnt/β-catenin signaling pathway by autophagy was involved in the prodifferentiation effect of rapamycin at middle stage.