Bone morphogenetic protein-2 induces expression of murine zinc finger transcription factor ZNF450

LINC00473-modified bone marrow mesenchymal stem cells incorporated thermosensitive PLGA hydrogel transplantation for steroid-induced osteonecrosis of femoral head: A detailed mechanistic study and validity evaluation

The pathogenesis of steroid-induced osteonecrosis of the femoral head (SONFH) involves a glucocorticoid-induced imbalance of osteogenic and adipogenic differentiation, and apoptosis of bone marrow mesenchymal stem cells (BMSCs). An increasing number of genes, especially noncoding RNAs, have been implicated in the function of BMSCs. Our previous studies have confirmed the key role of LINC00473 and miR-23a-3p on the osteogenic, adipogenic differentiation, and apoptosis of BMSCs. However, the underlying mechanism of this process is still unclear. Based on bioinformatics analysis, here we investigated the effects of LINC00473 on the LRP5/Wnt/β-catenin signaling pathway in the osteogenesis and adipogenesis of BMSCs, as well as the PEBP1/Akt/Bad/Bcl-2 signaling pathway in dexamethasone- (Dex-) induced apoptosis of BMSCs. Our data showed that LINC00473 could promote osteogenesis and suppress the adipogenesis of BMSCs through the activation of the miR-23a-3p/LRP5/Wnt/β-catenin signaling pathway axis, while rescuing BMSCs from Dex-induced apoptosis by activating the miR-23a-3p/PEBP1/Akt/Bad/Bcl-2 signaling pathway axis. Notably, we observed that LINC00473 interacted with miR-23a-3p in an Argonaute 2 (AGO2)-dependent manner based on dual-luciferase reporter assay, AGO2-related RNA immunoprecipitation, and RNA antisense purification assay. Furthermore, injectable thermosensitive polylactic-co-glycolic acid (PLGA) hydrogel loaded with rat-derived BMSCs (rBMSCs) modified by LINC00473 were used for the treatment of SONFH in a rat model. Our results demonstrated that PLGA hydrogels provided a suitable environment for harboring rBMSCs. Besides, transplantation of PLGA hydrogels loaded with rBMSCs modified by LINC00473 could significantly promote the bone repair and reconstruction of the necrotic area at the femoral head in our SONFH rat model. Surprisingly, compared with the transplantation of BMSCs alone, the transplanted rBMSCs encapsulated within the PLGA hydrogel could migrate from the medullary cavity to the femoral head. In summary, LINC00473 promoted osteogenesis, inhibited adipogenesis, and antagonized Dex-induced apoptosis of BMSCs. Therefore, LINC00473 could provide a new strategy for the treatment of SONFH.

Converging disease genes in ICF syndrome: ZBTB24 controls expression of CDCA7 in mammals

For genetically heterogeneous diseases a better understanding of how the underlying gene defects are functionally interconnected will be important for dissecting disease etiology. The Immunodeficiency, Centromeric instability, Facial anomalies (ICF) syndrome is a chromatin disorder characterized by mutations in DNMT3B, ZBTB24, CDCA7 or HELLS Here, we generated a Zbtb24 BTB domain deletion mouse and found that loss of functional Zbtb24 leads to early embryonic lethality. Transcriptome analysis identified Cdca7 as the top down-regulated gene in Zbtb24 homozygous mutant mESCs, which can be restored by ectopic ZBTB24 expression. We further demonstrate enrichment of ZBTB24 at the CDCA7 promoter suggesting that ZBTB24 can function as a transcription factor directly controlling Cdca7 expression. Finally, we show that this regulation is conserved between species and that CDCA7 levels are reduced in patients carrying ZBTB24 nonsense mutations. Together, our findings demonstrate convergence of the two ICF genes ZBTB24 and CDCA7 at the level of transcription.

Two ZNF509 (ZBTB49) isoforms induce cell-cycle arrest by activating transcription of p21/CDKN1A and RB upon exposure to genotoxic stress

ZNF509 is unique among POK family proteins in that four isoforms are generated by alternative splicing. Short ZNF509 (ZNF509S1, -S2 and -S3) isoforms contain one or two out of the seven zinc-fingers contained in long ZNF509 (ZNF509L). Here, we investigated the functions of ZNF509 isoforms in response to DNA damage, showing isoforms to be induced by p53. Intriguingly, to inhibit proliferation of HCT116 and HEK293 cells, we found that ZNF509L activates p21/CDKN1A transcription, while ZNF509S1 induces RB. ZNF509L binds to the p21/CDKN1A promoter either alone or by interacting with MIZ-1 to recruit the co-activator p300 to activate p21/CDKN1A transcription. In contrast, ZNF509S1 binds to the distal RB promoter to interact and interfere with the MIZF repressor, resulting in derepression and transcription of RB. Immunohistochemical analysis revealed that ZNF509 is highly expressed in normal epithelial cells, but was completely repressed in tumor tissues of the colon, lung and skin, indicating a possible role as a tumor suppressor.

A novel deletion in ZBTB24 in a Lebanese family with immunodeficiency, centromeric instability, and facial anomalies syndrome type 2

The immunodeficiency, centromeric instability and facial anomalies (ICF) syndrome is a rare autosomal recessive disease characterized by targeted chromosome breakage, directly related to a genomic methylation defect. It manifests with phenotypic and clinical variability, with the most consistent features being developmental delay, facial anomalies, cytogenetic defects and immunodeficiency with a reduction in serum immunoglobulin levels. From the molecular point of view, ICF syndrome was always divided into ICF type I (ICF1) and ICF type 2 (ICF2). Mutations in DNMT3B gene are responsible for ICF1, while mutations in ZBTB24 have been reported to be responsible for ICF2. In this study, we describe a Lebanese family with three ICF2 affected brothers. Sanger sequencing of the coding sequence of ZBTB24 gene was conducted and revealed a novel deletion: c.396_397delTA (p.His132Glnfs*19), resulting in a loss-of-function of the corresponding protein. ZBTB24 belongs to a large family of transcriptional factors and may be involved in DNA methylation of juxtacentromeric DNA. Detailed molecular and functional studies of the ZBTB24 and DNMT3B genes are needed to understand the pathophysiology of ICF syndrome.

Proteomic identification of differently expressed proteins responsible for osteoblast differentiation from human mesenchymal stem cells

Human mesenchymal stem cells (hMSC) are a population of multipotent cells that can differentiate into osteoblasts, chondrocytes, adipocytes, and other cells. The exact mechanism governing the differentiation of hMSC into osteoblasts remains largely unknown. Here, we analyzed protein expression profiles of undifferentiated as well as osteogenic induced hMSC using 2-D gel electrophoresis (2-DE), mass spectrometry (MS), and peptide mass fingerprinting (PMF) to investigate the early gene expression in osteoblast differentiation. We have generated proteome maps of undifferentiated hMSC and osteogenic induced hMSC on day 3 and day 7. 2-DE revealed 102 spots with at least 2.0-fold changes in expression and 52 differently expressed proteins were successfully identified by MALDI-TOF-MS. These proteins were classified into 7 functional categories: metabolism, signal transduction, transcription, calcium-binding protein, protein degradation, protein folding and others. The expression of some identified proteins was confirmed by further RT-PCR analyses. This study clarifies the global proteome during osteoblast differentiation. Our results will play an important role in better elucidating the underlying molecular mechanism in hMSC differentiation into osteoblasts.

Adult human sarcomas. I. Basic science

When connective tissue undergoes malignant transformation, glioblastomas and sarcomas arise. However, the ancient biochemical mechanisms, which are now operational in sarcomas distorted by mutations and gene fusions in misaligned chromosomes, were originally acquired by those cells that emerged during the Cambrian explosion. Preserved throughout evolution up to the genus Homo, these mechanisms dictate the apoptosis- and senescence-resistant immortality of malignant cells. A 'retroviral paradox' distinguishes human sarcomas from those of the animal world. In contrast to the retrovirally induced sarcomatous transformation of animal (avian, murine, feline and simian) cells, human sarcomas have so far failed to yield a causative retroviral isolate. However, the proto-oncogenes/oncogenes transduced from their host cells by retroviruses of animals are the same that are active in human sarcomas. Since the encoded oncoproteins arise after birth, they are recognized frequently by the immune system of the host. Immune lymphocytes that kill autologous sarcoma cells in vitro commonly fail to do so in vivo. Sarcoma vaccines generate immune T- and natural killer cell reactions; even when vaccinated patients do not show a clinical response, their tumors become more sensitive to chemotherapy. The aim of this review is to lay a solid molecular biological foundation for the conclusion that targeting the sarcoma oncogenes will result in regression of the disease.

Genomic structure and cloning of two transcript isoforms of human Sp8

Background

The Specificity proteins (Sp) are a family of transcription factors that have three highly conserved zinc-fingers located towards the carboxy-terminal that bind GC-boxes and assist in the initiation of gene transcription. Human Sp1-7 genes have been characterized. Recently, the phenotype of Sp8 null mice has been described, being tailless and having severe truncation of both fore and hind limbs. They also have malformed brains with defective closure of the anterior and posterior neuropore during brain development.

Results

The human Sp8 gene is a three-exon gene that maps to 7p21.3, close to the related Sp4 gene. From an osteosarcoma cell line we cloned two transcript variants that use two different first exons and have a common second exon. One clone encodes a 508-residue protein, Sp8L (isoform 1) and the other a shorter 490-residue protein, Sp8S (isoform 2). These two isoforms are conserved being found also in mice and zebrafish. Analysis of the Sp8L protein sequence reveals an amino-terminal hydrophobic Sp-motif that is disrupted in Sp8S, a buttonhead box and three C₂H₂ zinc-fingers. Sp8 mRNA expression was detected in a wide range of tissues at a low level, with the highest levels being found in brain. Treatment of the murine pluripotent cell line C3H10T1/2 with 100 ng/mL BMP-2 induced Sp8 mRNA after 24 hours.

Conclusions

There is conservation of the two Sp8 protein isoforms between primates, rodents and fish, suggesting that the isoforms have differing roles in gene regulation. Sp8 may play a role in chondrogenic/osteoblastic differentiation in addition to its role in brain and limb development.