Temporospatial gene expression of Prx1 and Prx2 is involved in morphogenesis of cranial placode-derived tissues through epithelio-mesenchymal interaction during rat embryogenesis

Reciprocal negative feedback between Prrx1 and miR-140-3p regulates rapid chondrogenesis in the regenerating antler

During growth phase, antlers exhibit a very rapid rate of chondrogenesis. The antler is formed from its growth center reserve mesenchyme (RM) cells, which have been found to be the derivatives of paired related homeobox 1 (Prrx1)-positive periosteal cells. However, the underlying mechanism that drives rapid chondrogenesis is not known. Herein, the miRNA expression profiles and chromatin states of three tissue layers (RM, precartilage, and cartilage) at different stages of differentiation within the antler growth center were analyzed by RNA-sequencing and ATAC-sequencing. We found that miR-140-3p was the miRNA that exhibited the greatest degree of upregulation in the rapidly growing antler, increasing from the RM to the cartilage layer. We also showed that Prrx1 was a key upstream regulator of miR-140-3p, which firmly confirmed by Prrx1 CUT&Tag sequencing of RM cells. Through multiple approaches (three-dimensional chondrogenic culture and xenogeneic antler model), we demonstrated that Prrx1 and miR-140-3p functioned as reciprocal negative feedback in the antler growth center, and downregulating PRRX1/upregulating miR-140-3p promoted rapid chondrogenesis of RM cells and xenogeneic antler. Thus, we conclude that the reciprocal negative feedback between Prrx1 and miR-140-3p is essential for balancing mesenchymal proliferation and chondrogenic differentiation in the regenerating antler. We further propose that the mechanism underlying chondrogenesis in the regenerating antler would provide a reference for helping understand the regulation of human cartilage regeneration and repair.

Spinal-Specific Super Enhancer in Neuropathic Pain

Dysfunctional gene expression in nociceptive pathways plays a critical role in the development and maintenance of neuropathic pain. Super enhancers (SEs), composed of a large cluster of transcriptional enhancers, are emerging as new players in the regulation of gene expression. However, whether SEs participate in nociceptive responses remains unknown. Here, we report a spinal-specific SE (SS-SE) that regulates chronic constriction injury (CCI)-induced neuropathic pain by driving Ntmt1 and Prrx2 transcription in dorsal horn neurons. Peripheral nerve injury significantly enhanced the activity of SS-SE and increased the expression of NTMT1 and PRRX2 in the dorsal horn of male mice in a bromodomain-containing protein 4 (BRD4)-dependent manner. Both intrathecal administration of a pharmacological BRD4 inhibitor JQ1 and CRISPR-Cas9-mediated SE deletion abolished the increased NTMT1 and PRRX2 in CCI mice and attenuated their nociceptive hypersensitivities. Furthermore, knocking down Ntmt1 or Prrx2 with siRNA suppressed the injury-induced elevation of phosphorylated extracellular-signal-regulated kinase (p-ERK) and glial fibrillary acidic protein (GFAP) expression in the dorsal horn and alleviated neuropathic pain behaviors. Mimicking the increase in spinal Ntmt1 or Prrx2 in naive mice increased p-ERK and GFAP expression and led to the genesis of neuropathic pain-like behavior. These results redefine our understanding of the regulation of pain-related genes and demonstrate that BRD4-driven increases in SS-SE activity is responsible for the genesis of neuropathic pain through the governance of NTMT1 and PRRX2 expression in dorsal horn neurons. Our findings highlight the therapeutic potential of BRD4 inhibitors for the treatment of neuropathic pain.SIGNIFICANCE STATEMENT SEs drive gene expression by recruiting master transcription factors, cofactors, and RNA polymerase, but their role in the development of neuropathic pain remains unknown. Here, we report that the activity of an SS-SE, located upstream of the genes Ntmt1 and Prrx2, was elevated in the dorsal horn of mice with neuropathic pain. SS-SE contributes to the genesis of neuropathic pain by driving expression of Ntmt1 and Prrx2 Both inhibition of SS-SE with a pharmacological BRD4 inhibitor and genetic deletion of SS-SE attenuated pain hypersensitivities. This study suggests an effective and novel therapeutic strategy for neuropathic pain.

PRRX2 predicts poor survival prognosis, and promotes malignant phenotype of lung adenocarcinoma via transcriptional activates PSMD1

INTRODUCTION

Paired-related homeobox transcription factor 2 (PRRX2) has been proved involves in the pathogenesis of tumors, but the role of PRRX2 in lung adenocarcinoma (LUAD) is basically not clear.

MATERIALS AND METHODS

LUAD datasets were obtained from Gene Expression Omnibus datasets. Functional enrichment analyses were performed based on R language. Several online analysis tools were used for PRRX2 expression, survival curves, and immune cell infiltration analyses. CCK-8, flow cytometry assays were used to detect the cell proliferation and apoptosis. Dual luciferase reporter system and chromatin immunoprecipitation were used to explore the interaction of PRRX2 and Proteasome 26S subunit, non-ATPases 1 (PSMD1). Xenograft in nude mice was used to assess the function of PRRX2 regulation in vivo.

RESULTS AND DISCUSSION

Bioinformatics analyses found that PRRX2 was highly expressed in LUAD tissues and the high PRRX2 expression had a poor prognostic value. PRRX2 was highly expressed in LUAD clinical samples and cell lines. PRRX2 acted as a positive regulator of cell proliferation and a negative regulator of apoptosis. PRRX2 could bind with the PSMD1 promoter and regulate PSMD1 expression, thereby affected LUAD cells' malignant phenotype. Result of xenografts in nude mice confirmed that PRRX2 promotes LUAD tumor growth in vivo. Summary, our study results reveal the crucial roles for PRRX2 in the proliferation and apoptosis of LUAD progression and suggest that PRRX2 may regulate PSMD1 expression by combining with the PSMD1 promoter, thereby participating in the malignant behavior of LUAD.

MicroRNA-7a2 is required for the development of pituitary stem cells

The pituitary gland is inhabited by a subpopulation of SOX2+ stem cells. However, the regulatory mechanisms underlying pituitary stem cell development remain poorly understood. Here, we demonstrate that microRNA-7a (miR-7a) is enriched in the developing pituitary and is spatiotemporally expressed in the pituitary stem cells. Constitutive deletion of miR-7a2 in mice results in pituitary dysplasia emerging during birth, which is primarily manifested as malformed anterior lobes. Using immunofluorescence, immunohistochemistry or in situ hybridization, we observe that the specification of hormone-expressing cells is not impeded post miR-7a2 deletion at birth, although the terminal differentiation of gonadotropes is inhibited. Further investigation of neonatal and adult pituitaries in miR-7a2 knockout mice reveals an expansion of the SOX2+ pituitary stem cell compartment. The inhibition of epithelial-mesenchymal like transition seems to be responsible for this phenotype, rather than abnormal proliferation or apoptosis. Furthermore, our data suggest that Gli3 and Ckap4 are potential targets of miR-7a in pituitary stem cells. In summary, our results identify miR-7a2 as a crucial factor involved in pituitary stem cell development.

Identification of osteogenic progenitor cell-targeted peptides that augment bone formation

Activation and migration of endogenous mesenchymal stromal cells (MSCs) are critical for bone regeneration. Here, we report a combinational peptide screening strategy for rapid discovery of ligands that not only bind strongly to osteogenic progenitor cells (OPCs) but also stimulate osteogenic cell Akt signaling in those OPCs. Two lead compounds are discovered, YLL3 and YLL8, both of which increase osteoprogenitor osteogenic differentiation in vitro. When given to normal or osteopenic mice, the compounds increase mineral apposition rate, bone formation, bone mass, and bone strength, as well as expedite fracture repair through stimulated endogenous osteogenesis. When covalently conjugated to alendronate, YLLs acquire an additional function resulting in a “tri-functional” compound that: (i) binds to OPCs, (ii) targets bone, and (iii) induces “pro-survival” signal. These bone-targeted, osteogenic peptides are well suited for current tissue-specific therapeutic paradigms to augment the endogenous osteogenic cells for bone regeneration and the treatment of bone loss.

Activation of osteogenic cells is essential for bone regeneration. Here, the authors screen a peptide library and identify 2 compounds that promote osteogenic progenitor cell differentiation in vitro, and show that they increase bone formation and fracture repair in mice.

Aberrant expression of vasculogenic mimicry, PRRX1, and CIP2A in clear cell renal cell carcinoma and its clinicopathological significance

Vasculogenic mimicry (VM) involves a tubular structure with a basement membrane that is similar to and communicates with vessels but functions independent of blood vessels to nourish tumor cells, promote tumor progression, invasion, and metastasis, with reduced 5-year survival rates. Tumor cell proliferation, invasion, and metastasis are promoted by the epithelial-mesenchymal transition (EMT). Paired-related homeobox 1 (PRRX1), a newly discovered EMT inducer, has been shown to correlate with metastasis and prognosis in diverse cancer types. Cancerous inhibitor of protein phosphatase 2A (CIP2A) was initially recognized as an oncoprotein. In this study, we aimed to investigate the expression and clinical significance of the EMT markers PRRX1, CIP2A and VM in clear cell renal cell carcinoma (CCRCC) and their respective associations with clinicopathological parameters and survival.Expression of PRRX1, CIP2A and VM in whole CCRCC tissues from 110 patients was analyzed by immunohistochemical and histochemical staining. Fisher's exact test or the chi square test was used to assess associations with positive or negative staining of these markers and clinicopathological characteristics.Positive expression of CIP2A and VM presence was significantly higher and that of PRRX1 was significantly lower in CCRCC tissues than in corresponding normal tissues. Furthermore, positive expression of CIP2A and VM was significantly associated with tumor grade, size, lymph node metastasis (LNM) stage, and tumor node metastasis (TNM) stage and inversely associated with overall survival time (OST). Moreover, levels of PRRX1 were negatively associated with tumor grade, size, LNM stage, and TNM stage. The PRRX1 subgroup had a significantly longer OST time than did the PRRX1 subgroup. In multivariate analysis, high VM and CIP2A, tumor grade, LNM stage, TNM stage, and low PRRX1 levels were identified as potential independent prognostic factors for OST in CCRCC patients.VM and expression of CIP2A and PRRX1 represent promising biomarkers for metastasis and prognosis and potential therapeutic targets in CCRCC.

Inhibition of PRRX2 suppressed colon cancer liver metastasis via inactivation of Wnt/β-catenin signaling pathway

The aim of this study was to investigate whether PRRX2 may regulate the liver metastasis of colon cancer via the Wnt/β-catenin signaling pathway. PRRX2 and β-catenin in patients with the liver metastases of colon cancer was detected by immunochemistry. Colon cancer cells (CT-26 and CMT93) were divided into Normal, si-Ctrl, si-PRRX2 and si-PRRX2 +LiCl groups. Cell invasive and migrating abilities and the related proteins were detected. Liver-metastatic mice model was constructed consisting of Normal, NC shRNA and PRRX2 shRNA groups to examine the function of PRRX2 shRNA on liver metastasis. We found that PRRX2 and β-catenin positive rate was elevated in colon cancer tissues, especially in those tissues with liver metastasis, and there was a close relation between PRRX2 and the clinical staging, lymph node metastasis and numbers of liver metastases of colon cancer patients with liver metastasis. In vitro, the invasive and migrating abilities of CT-26 and CMT93 cells decreased apparently in the si-PRRX2 group, with down-regulation of PRRX2, p-GSK3β^Ser9/GSK3β, nucleus and cytoplasm β-catenin, TCF4 and Vimentin but up-regulation of E-cadherin. However, LiCl, the Wnt/β-catenin pathway activator, can reverse the inhibitory effect of si-PRRX2 on invasive and migrating ability of colon cancer cells. In vivo, the volume and weight of transplanted tumor and the number of liver metastases in the PRRX2 shRNA group were significantly reduced, with the similar protein expression patterns as in vitro. In a word, PRRX2 inhibition may reduce invasive and migrating abilities to hinder epithelial-mesenchymal transition (EMT), and suppress colon cancer liver metastasis through inactivation of Wnt/β-catenin pathway.

gga-mir-133a-3p Regulates Myoblasts Proliferation and Differentiation by Targeting PRRX1

Non-coding RNAs play a regulatory role in the growth and development of skeletal muscle. Our previous study suggested that gga-mir-133a-3p was a potential candidate for regulating myoblast proliferation and differentiation in skeletal muscle. The purpose of our study was to reveal the regulatory mechanism of gga-mir-133a-3p in the proliferation and differentiation of chicken myoblasts. Through the detection of cell proliferation activity, cell cycle progression and EdU, we found that gga-mir-133a-3p can significantly inhibit the proliferation of myoblasts. In the process of myogenic differentiation, gga-mir-133a-3p is up-regulated, while gga-mir-133a-3p can significantly promote the up-regulation of differentiation-related muscle-derived factors, indicating that gga-mir-133a-3p can promote the differentiation of myoblasts. Validation at the transcriptional level and protein level proved that gga-mir-133a-3p can inhibit the expression of PRRX1, and the dual-luciferase assay also showed their direct targeting relationship. Correspondingly, PRRX1 can significantly promote myoblast proliferation and inhibit myoblast differentiation. In our study, we confirmed that gga-mir-133a-3p participates in the regulation of proliferation and differentiation of myoblasts by targeting PRRX1.

S100β-Positive Cells of Mesenchymal Origin Reside in the Anterior Lobe of the Embryonic Pituitary Gland

The anterior and intermediate lobes of the pituitary gland develop through invagination of the oral ectoderm and as they are endocrine tissues, they participate in the maintenance of vital functions via the synthesis and secretion of numerous hormones. We recently observed that several extrapituitary cells invade the anterior lobe of the developing pituitary gland. This raised the question of the origin(s) of these S100β-positive cells, which are not classic endocrine cells but instead comprise a heterogeneous cell population with plural roles, especially as stem/progenitor cells. To better understand the roles of these S100β-positive cells, we performed immunohistochemical analysis using several markers in S100β/GFP-TG rats, which express GFP in S100β-expressing cells under control of the S100β promoter. GFP-positive cells were present as mesenchymal cells surrounding the developing pituitary gland and at Atwell's recess but were not present in the anterior lobe on embryonic day 15.5. These cells were negative for SOX2, a pituitary stem/progenitor marker, and PRRX1, a mesenchyme and pituitary stem/progenitor marker. However, three days later, GFP-positive and PRRX1-positive (but SOX2-negative) cells were observed in the parenchyma of the anterior lobe. Furthermore, some GFP-positive cells were positive for vimentin, p75, isolectin B4, DESMIN, and Ki67. These data suggest that S100β-positive cells of extrapituitary origin invade the anterior lobe, undergoing proliferation and diverse transformation during pituitary organogenesis.

Expression studies of neuronatin in prenatal and postnatal rat pituitary

The pituitary gland, an indispensable endocrine organ that synthesizes and secretes pituitary hormones, develops with the support of many factors. Among them, neuronatin (NNAT), which was discovered in the neonatal mouse brain as a factor involved in neural development, has subsequently been revealed to be coded by an abundantly expressing gene in the pituitary gland but its role remains elusive. We analyze the expression profile of Nnat and the localization of its product during rat pituitary development. The level of Nnat expression was high during the embryonic period but remarkably decreased after birth. Immunohistochemistry demonstrated that NNAT appeared in the SOX2-positive stem/progenitor cells in the developing pituitary primordium on rat embryonic day 11.5 (E11.5) and later in the majority of SOX2/PROP1 double-positive cells on E13.5. Thereafter, during pituitary embryonic development, Nnat expression was observed in some stem/progenitor cells, proliferating cells and terminally differentiating cells. In postnatal pituitaries, NNAT-positive cells decreased in number, with most coexpressing Sox2 or Pit1, suggesting a similar role for NNAT to that during the embryonic period. NNAT was widely localized in mitochondria, peroxisomes and lysosomes, in addition to the endoplasmic reticulum but not in the Golgi. The present study thus demonstrated the variability in expression of NNAT-positive cells in rat embryonic and postnatal pituitaries and the intracellular localization of NNAT. Further investigations to obtain functional evidence for NNAT are a prerequisite.

PRRX1- and PRRX2-positive mesenchymal stem/progenitor cells are involved in vasculogenesis during rat embryonic pituitary development

We have recently shown that cells positive for the paired-related homeobox transcription factors PRRX1 and PRRX2 occur in the rat pituitary, and that they are derived from two different origins: pituitary-derived cells positive for stem cell marker SOX2 and extra-pituitary-derived cells negative for SOX2. In this study, we have further characterized the PRRX1- and PRRX2-positive cells that originate from extra-pituitary cells. Immunohistochemical analyses were performed with specific antibodies against PRRX1 and PRRX2 in order to clarify their roles in pituitary vasculogenesis. PRRX1- and PRRX2-positive cells were found in Atwell's recess and at the periphery of the pituitary on embryonic day 15.5 (E15.5). Several PRRX1-positive cells then invaded the anterior lobe, together with a few PRRX2-positive cells, on E16.5. Some PRRX1-positive cells were also positive for mesenchymal stem cell marker NESTIN. Moreover, some PRRX1/NESTIN double-positive cells showed characteristics of vascular endothelial cells with an Isolectin-B4-binding capacity. PRRX1 co-localized with vascular smooth muscle cell/pericyte marker α-smooth muscle actin in the deep area of Atwell's recess. We confirmed the presence of PRRX2/NESTIN double-positive cells at an entry area in Atwell's recess and at the periphery of the pituitary, but PRRX2 did not co-localize with Isolectin B4 or α-smooth muscle actin. These data suggest that PRRX1- and PRRX2-positive mesenchymal stem/progenitor cells are present at the periphery of the embryonic pituitary and at the entry from Atwell's recess and participate in pituitary vasculogenesis by differentiation into vascular endothelial cells and pericytes, whereas the presence of PRRX2 indicates much higher stemness than PRRX1.

Expression of Krüppel-like factor 6, KLF6, in rat pituitary stem/progenitor cells and its regulation of the PRRX2 gene

Paired-related transcription factors, PRRX1 and PRRX2, which are present in mesenchymal tissues and participate in mesenchymal cell differentiation, were recently found in the stem/progenitor cells of the pituitary gland of ectodermal origin. To clarify the role of PRRX1 and PRRX2 in the pituitary gland, the present study first aimed to identify transcription factors that regulate Prrx1 and Prrx2 expression. A promoter assay for the upstream regions of both genes was performed by co-transfection of the expression vector of several transcription factors, many of which are frequently found in the pituitary stem/progenitor cells. The results for the promoter activity of both genes showed expression in a cell type-dependent manner. Comprehensive comparison of transcriptional activity of several transcription factors was performed with CHO cells, which do not show Prrx1 and Prrx2 expression, and the results revealed the presence of common and distinct factors for both genes. Among them, KLF6 showed specific and remarkable stimulation of Prrx2 expression. In vitro experiments using an electrophoretic mobility shift assay and siRNA interference revealed a potential ability for regulation of Prrx2 expression by KLF6. Finally, immunohistochemistry confirmed the presence of KLF6 in the SOX2/PRRX2 double-positive stem/progenitor cells of the postnatal pituitary gland. Thus, the finding of KLF6 might provide a novel clue to clarify the maintenance of stem/progenitor cells of the postnatal pituitary gland.

Characterization of murine pituitary-derived cell lines Tpit/F1, Tpit/E and TtT/GF

The pituitary is an important endocrine tissue of the vertebrate that produces and secretes many hormones. Accumulating data suggest that several types of cells compose the pituitary, and there is growing interest in elucidating the origin of these cell types and their roles in pituitary organogenesis. Therein, the histogenous cell line is an extremely valuable experimental tool for investigating the function of derived tissue. In this study, we compared gene expression profiles by microarray analysis and real-time PCR for murine pituitary tumor-derived non-hormone-producing cell lines TtT/GF, Tpit/F1 and Tpit/E. Several genes are characteristically expressed in each cell line: Abcg2, Nestin, Prrx1, Prrx2, CD34, Eng, Cspg4 (Ng2), S100β and nNos in TtT/GF; Cxcl12, Raldh1, Msx1 and Twist1 in Tpit/F1; and Cxadr, Sox9, Cdh1, EpCAM and Krt8 in Tpit/E. Ultimately, we came to the following conclusions: TtT/GF cells show the most differentiated state, and may have some properties of the pituitary vascular endothelial cell and/or pericyte. Tpit/F1 cells show the epithelial and mesenchymal phenotypes with stemness still in a transiting state. Tpit/E cells have a phenotype of epithelial cells and are the most immature cells in the progression of differentiation or in the initial endothelial-mesenchymal transition (EMT). Thus, these three cell lines must be useful model cell lines for investigating pituitary stem/progenitor cells as well as organogenesis.

Molecular cloning of rat and porcine retina-derived POU domain factor 1 (POU6F2) from a pituitary cDNA library

Homeobox transcription factors are known to play crucial roles in the anterior lobe of the pituitary gland. During molecular cloning with the Yeast One-Hybrid System using a 5'-upstream region of the porcine Fshβ as a bait sequence, we have cloned a cDNA encoding a partial sequence of the retina-derived POU domain factor 1 (RPF1) from the porcine pituitary cDNA library and confirmed its specific binding to the bait sequence. In situ hybridization was performed to examine localization of Rpf1 and showed that this gene is expressed in the stem/progenitor cells of the rat pituitary primordium as well as the diencephalon and retina. In addition, real-time PCR demonstrated that Rpf1 transcripts are abundant in early embryonic periods but that this is followed by a decrease during pituitary development, indicating that this factor plays a role in differentiating cells of the pituitary. The transcriptional activity of RPF1 for genes of Prop1, Prrx1 and Prrx2, which were characterized as genes participating in the pituitary stem/progenitor cells by our group, was then examined with full-length cDNA obtained from the rat pituitary. RPF1 showed regulatory activity for Prop1 and Prrx2, but not for Prrx1. These results indicate the involvement of this retina-derived factor in pituitary development.

Rapid transition of NESTIN-expressing dividing cells from PROP1-positive to PIT1-positive advances prenatal pituitary development

We recently reported that the quantitative and qualitative transition of stem/progenitor cells occurs by the acquisition of a novel mechanism in the terminal differentiation during postnatal development of the anterior pituitary. We hypothesised that this novel mechanism is an alteration of a cell supply system accompanying proliferation of the progenitor cells. In the present study, we examined the proliferation activities of progenitor cells by indication of the expression of Nestin, a marker of rapidly dividing progenitor cells, aiming to verify our hypothesis and to resolve another outstanding issue regarding whether the Nestin gene is expressed in the pituitary. We found that NESTIN-positive dividing cells certainly exist in the pituitary through all stages of development. Almost all of the PROP1-positive progenitor cells express Nestin in early embryonic pituitary development. Thereafter, Nestin-expressing dividing cells involved in the cell supply system transfer from PROP1-positive progenitor cells to committed progenitor cells, such as PIT1-positive cells, on neonatal pituitary development. Furthermore, our data, together with the findings of previous studies on cell lineage tracing analyses using Nestin-Cre mice derived by the central nervous system (CNS)-specific Nestin promoter, suggest that at least two regulation systems for Nestin-expression exist in the pituitary, with the majority of these not being CNS-specific.