Heart development is a delicate and complex process regulated by coordination of various signaling pathways. In this study, we investigated the role of sox18 in heart development by modulating Wnt/β-Catenin signaling pathways. Our spatiotemporal expression analysis revealed that sox18 is mainly expressed in the heart, branchial arch, pharyngeal arch, spinal cord, and intersegmental vessels at the tailbud stage of Xenopus tropicalis embryo. Overexpression of sox18 in the X. tropicalis embryos causes heart edema, while loss-of-function of sox18 can change the signal of developmental heart marker gata4 at different stages, suggesting that sox18 plays an essential role in the development of the heart. Knockdown of SOX18 in human umbilical vein endothelial cells suggests a link between Sox18 and β-CATENIN, a key regulator of the Wnt signaling pathway. Sox18 negatively regulates islet1 and tbx3, the downstream factors of Wnt/β-Catenin signaling, during the linear heart tube formation and the heart looping stage. Taken together, our findings highlight the crucial role of Sox18 in the development of the heart via inhibiting Wnt/β-Catenin signaling.

SRY-box transcription factor 18 (SOX18) is known to play a crucial role in the growth and development of hair follicles (HF) in both humans and mice. However, the specific effect of SOX18 on sheep hair follicles remains largely unknown. In our previous study, we observed that SOX18 was specifically expressed within dermal papilla cells (DPCs) in ovine hair follicles, leading us to investigate its potential role in the growth of hair follicles in sheep. In the present study, we aimed to examine the effect of SOX18 in DPCs and preliminarily study its regulatory mechanism through RNA-seq. We initially found that the overexpression of SOX18 promoted the proliferation of DPCs compared to the negative control group, while the interference of SOX18 had the opposite effect. To gain further insight into the regulatory mechanism of SOX18, we conducted RNA-seq analysis after knocking down SOX18 in Hu sheep DPCs. The result showed that the Wnt/β-Catenin signaling pathway was involved in the growth process of DPC after SOX18 knockdown. Subsequently, we investigated the effect of SOX18 on the Wnt/β-Catenin signaling pathway in DPCs using TOP/FOP-flash, qRT-PCR, and Western blot (WB) analysis. Our data demonstrated that SOX18 could activate the Wnt/β-Catenin signaling pathway in DPCs. Additionally, we observed that SOX18 could rescue the proliferation of DPCs after inhibiting the Wnt/β-Catenin signaling pathway. These findings underscore the essential role of SOX18 as a functional molecule governing the proliferation of DPCs. Additionally, these findings also greatly enhance our understanding of the role of SOX18 in the proliferation of DPCs and the growth of wool in Hu sheep.

Mutations in the transcription factor-coding gene SOX18, the growth factor-coding gene VEGFC and its receptor-coding gene VEGFR3/FLT4 cause primary lymphedema in humans. In mammals, SOX18, together with COUP-TFII/NR2F2, activates the expression of Prox1, a master regulator in lymphatic identity and development. Knockdown studies have also suggested an involvement of Sox18, Coup-tfII/Nr2f2, and Prox1 in zebrafish lymphatic development. Mutants in the corresponding genes initially failed to recapitulate the lymphatic defects observed in morphants. In this paper, we describe a novel zebrafish sox18 mutant allele, sa12315, which behaves as a null. The formation of the lymphatic thoracic duct is affected in sox18 homozygous mutants, but defects are milder in both zygotic and maternal-zygotic sox18 mutants than in sox18 morphants. Remarkably, in sox18 mutants, the expression of the closely related sox7 gene is elevated where lymphatic precursors arise. Sox7 could thus mask the absence of a functional Sox18 protein and account for the mild lymphatic phenotype in sox18 mutants, as shown in mice. Partial knockdown of vegfc exacerbates lymphatic defects in sox18 mutants, making them visible in heterozygotes. Our data thus reinforce the genetic interaction between Sox18 and Vegfc in lymphatic development, previously suggested by knockdown studies, and highlight the ability of Sox7 to compensate for Sox18 lymphatic dysfunction.

The transcription factor SOX18 has been shown to play a crucial role in lung cancer progression and metastasis. In this study, we investigated the effect of Sm4, a SOX18 inhibitor, on cell cycle regulation in non-small cell lung cancer (NSCLC) cell lines LXF-289 and SK-MES-1, as well as normal human lung fibroblast cell line IMR-90. Our results demonstrated that Sm4 treatment induced cytotoxic effects on all three cell lines, with a greater effect observed in NSCLC adenocarcinoma cells. Sm4 treatment led to S-phase cell accumulation and upregulation of p21, a key regulator of the S-to-G2/M phase transition. While no significant changes in SOX7 or SOX17 protein expression were observed, Sm4 treatment resulted in a significant upregulation of SOX17 gene expression. Furthermore, our findings suggest a complex interplay between SOX18 and p21 in the context of lung cancer, with a positive correlation observed between SOX18 expression and p21 nuclear presence in clinical tissue samples obtained from lung cancer patients. These results suggest that Sm4 has the potential to disrupt the cell cycle and target cancer cell growth by modulating SOX18 activity and p21 expression. Further investigation is necessary to fully understand the relationship between SOX18 and p21 in lung cancer and to explore the therapeutic potential of SOX18 inhibition in lung cancer.

Head and neck squamous cell carcinoma (HNSCC) is the most common type of malignancy in the head and neck region worldwide. The therapeutic strategies for HNSCC remain unsatisfying and limited. Here, we found a population of resistant Bmi1-expressing cells in the presence of cetuximab treatment and reported a novel role of SRY-box transcription factor 18 (SOX18), a member of the SOX family, in promoting HNSCC resistance to cetuximab. This study aimed to investigate the regulatory mechanism of Sox18 in Bmi1-positive cells and to search for better therapeutic targets.
We successfully obtained Bmi1CreER, RosatdTomato, and RosaDTA mice and identified Bmi1-expressing cells through lineage tracing. SOX18 expression in HNSCC and normal tissues was analyzed by immunohistochemistry, colocalization of Sox18, and Bmi1-expressing cells was analyzed by immunofluorescence, and SOX18 expression in SCC9 cell lines was quantified by western blotting and quantitative real-time PCR. The investigation of the mechanism of SOX18-mediated cetuximab resistance in Bmi1-positive cells was based on the analysis of single-cell RNA-seq data obtained from the Gene Expression Omnibus (GEO) database. Western blotting was performed to verify the results obtained from the single-cell RNA-seq analysis.
In our study, we demonstrated that Bmi1-expressing cells were resistant to cetuximab treatment and that depletion of Bmi1-expressing cells improved cetuximab efficacy in HNSCC. We then discovered that Sox18 mediated the stem cell-like properties of Bmi1-expressing cells and promoted cellular cetuximab resistance through an oxidative phosphorylation pathway. There was a significant downregulation of key genes in the oxidative phosphorylation pathway in Sox18 knockout cell lines.
Taken together, the findings of our study suggest that Sox18 mediates the resistance of Bmi1-expressing cells to cetuximab in HNSCC via the oxidative phosphorylation pathway.

Dermal papilla cell (DPC), one of the key cell types during hair follicle development and regeneration, specifies hair size, shape and cycling. It is also an important in vitro screening model for hair growth. Although some characteristics of DPCs, such as agglutinative growth and marker genes, have been studied in mice and humans, the intrinsic properties of ovine DPCs and the regulatory mechanism of the intrinsic properties during continued culture in vitro remained unknown. In this study, based on our previous single-cell transcriptome sequencing on sheep lambskin, we verified SOX18 and PDGFRA as the novel marker genes of ovine DPCs through immunofluorescence staining on skin sections and cultured DPCs. Using continued cell culture and alkaline phosphatase staining, we found that different from mice and humans, ovine DPCs exhibit particularly robust and stable aggregation with unbated alkaline phosphatase activity till 30 passages during continued culture in vitro. Also, we found that the expression of some marker genes and the activity of Wnt/β-catenin signaling differ between early passaged DPCs and multiple passaged DPCs. Further, using Wnt/β-catenin agonist and antagonist, we demonstrated that Wnt/β-catenin signaling could regulate cell aggregation and alkaline phosphatase activity of ovine DPCs through regulating FGF and IGF signaling. This study provides the basis for isolating ovine DPCs and defines their intrinsic properties, which contribute to improving wool performance and medicine of hair regeneration.

BACKGROUND: Brain microvascular endothelial cells (BMECs) play a major role in the blood-brain barrier (BBB), and are critical for establishing an in vitro BBB model. Currently, iPSC-derived BMECs (iBMECs) have been used to construct in vitro BBB models with physiological barrier functions, such as high trans-endothelial electrical resistance (TEER) and expression of transporter proteins. However, the relatively low p-glycoprotein (P-gp) level and a decrease in the efflux ratio of its substrates in iBMECs suggest their immature nature. Therefore, more mature iBMECs by optimizing the differentiation induction protocol is beneficial for establishing a more reliable in vitro BBB model for studying central nervous system (CNS) drug transport.
METHODS: To identify human brain endothelial cell fate-inducing factors, HUVEC was transfected with Zic3A-, Zic3B-, and Sox18-expressing lentivirus vector. Since SOX18 was found to induce BMEC properties, we used a Dox-inducible Tet-on system to express SOX18 during iBMEC differentiation and explored the impact of SOX18 expression on iBMEC maturation.
RESULTS: Sox18-mediated iBMECs achieved a higher TEER value than normal iBMECs (> 3000 Ω cm2). From day 6 to day 10 (d6-10 group), the iBMECs with SOX18 expression expressed a series of tight junction markers and showed upregulation of Mfsd2a, a specific marker of the BBB. The d6-10 group also expressed SLC2A1/Glut1 at levels as high as normal iBMECs, and upregulated ABCB1/P-gp and ABCC1/MRP1 expression. Moreover, Sox18-mediated iBMECs showed higher viability than normal iBMECs after puromycin treatment, indicating that SOX18 expression could upregulate P-gp activity in iBMECs.
CONCLUSIONS: Inducible SOX18 expression in iBMECs gained BBB phenotypes, including high TEER values and upregulation of tight junction-related genes, endothelial cell (EC) markers, BBB transporters, and higher cell viability after treatment with puromycin. Collectively, we provide a differentiation method for the maturation of human iPS cell-derived BMECs with SOX18 expression, describing its contribution to form an in vitro BBB model for CNS drug transport studies.

Sox18 is a developmental gene that encodes transcription factors. It has been indicated as be a key gene affecting the growth and development of hair follicles, in which dermal papilla cells (DPCs) have been demonstrated to play an important role through their ability to induce the formation of hair follicles. Pre-laboratory studies have found that Sox18 is differentially expressed in the dermal papilla cells of different pattern types of Hu sheep. We speculated that Sox18 plays an important role in the dermal papilla cells of Hu sheep. In our study, we analyzed the effect of Sox18 on the induction ability of DPCs in order to elucidate the function and molecular mechanism of Sox18 in the DPCs of Hu sheep. We first identified the expression of Sox18 in the DPCs of Hu sheep by immunofluorescence staining. We then used alkaline phosphatase staining, cell morphology observations and RT-PCR to detect the effect of Sox18 on the induction of DPCs after overexpression of or interference with Sox18. We also used RT-PCR, WB and immunofluorescence staining to detect the effect of Sox18 on the Wnt/β-catenin signal pathway in DPCs. We found that Sox18 was specifically expressed in the DPCs of Hu sheep, and that Sox18 could enhance the alkaline phosphatase activity in the DPCs of Hu sheep and accelerate cell agglutination. The results of RT-PCR revealed that Sox18 promoted the mRNA expression of Versican, HHIP and FGFRI, and inhibited the mRNA expression of BMP4 and WIF1. Further studies showed that Sox18 promoted the expression of β-catenin and activated the Wnt/β-catenin signal pathway in DPCs. When the Wnt/β-catenin signal pathway of DPCs was activated, the induction ability of DPCs was enhanced. Overall, we believe that Sox18 could enhance the induction ability of DPCs in Hu sheep and regulate the induction ability of DPCs through the Wnt/β-catenin signal pathway.

UNASSIGNED: Hypotrichosis-lymphedema-telangiectasia syndrome (HLTS) is a disease characterized by the failure of angiogenesis, vascularization, and hair formation caused by a mutation in the SOX18 gene.
UNASSIGNED: We report a 15-year-old female patient presented with sparse hairs on her scalp and eyebrows and the absence of eyelashes and body hair since birth. We detected premature weathering due to abnormality of the hair shaft.
UNASSIGNED: Detection of trichophytosis and split hair in light microscopy in a patient with sparse hair, telangiectasia, and lymphedema may help diagnose HLTS.

Pathogenic variants in SOX18 are associated with hypotrichosis-lymphedema-telangiectasia-renal defects syndrome (HLTRS) and hypotrichosis-lymphedema-telangiectasia syndrome (HLTS). Eleven patients with SOX18 related HLTRS/HLTS have been previously described. Cardinal features include varying degrees of hypotrichosis, lymphedema and telangiectasias. We report a 15-year-old female patient with a likely de novo SOX18 pathogenic variant identified on duo exome sequencing. In addition to the classic features, the currently reported patient presented with novel clinical features including musculoskeletal abnormalities and strikingly poor wound healing. Chronic skin ulcers have been a major cause of morbidity for the patient and have led to significant functional limitation. Further, our experience with wound management has been detailed. We hope to improve understanding of the clinical spectrum of this ultra-rare disorder by reviewing the phenotypic features in all reported patients including our patient.