Regulation of hematopoietic development by ZBTB transcription factors

Fetal hemoglobin induction in azacytidine responders enlightens methylation patterns related to blast clearance in higher-risk MDS and CMML

BACKGROUND

As new treatment options for patients with higher-risk myelodysplastic syndromes are emerging, identification of prognostic markers for hypomethylating agent (HMA) treatment and understanding mechanisms of their delayed and short-term responses are essential. Early fetal hemoglobin (HbF) induction has been suggested as a prognostic indicator for decitabine-treated patients. Although epigenetic mechanisms are assumed, responding patients' epigenomes have not been thoroughly examined. We aimed to clarify HbF kinetics and prognostic value for azacytidine treated patients, as well as the epigenetic landscape that might influence HbF re-expression and its clinical relevance.

RESULTS

Serial HbF measurements by high-performance liquid chromatography (n = 20) showed induction of HbF only among responders (p = 0.030). Moreover, HbF increase immediately after the first azacytidine cycle demonstrated prognostic value for progression-free survival (PFS) (p = 0.032, HR = 0.19, CI 0.24-1.63). Changes in methylation patterns were revealed with methylated DNA genome-wide sequencing analysis (n = 7) for FOG-1, RCOR-1, ZBTB7A and genes of the NuRD-complex components. Targeted pyrosequencing methodology (n = 28) revealed a strong inverse correlation between the degree of γ-globin gene (HBG2) promoter methylation and baseline HbF levels (p = 0.003, rs =  - 0.663). A potential epigenetic mechanism of HbF re-expression in azacytidine responders was enlightened by targeted methylation analysis, through hypomethylation of site -53 of HBG2 promoter (p = 0.039, rs =  - 0.504), which corresponds to MBD2-NuRD binding site, and to hypermethylation of the CpG326 island of ZBTB7A (p = 0.05, rs = 0.482), a known HbF repressor. These changes were associated to blast cell clearance (pHBG2 = 0.011, rs = 0.480/pZBTB7A = 0.026, rs = 0.427) and showed prognostic value for PFS (pZBTB7A = 0.037, HR = 1.14, CI 0.34-3.8).

CONCLUSIONS

Early HbF induction is featured as an accessible prognostic indicator for HMA treatment and the proposed potential epigenetic mechanism of HbF re-expression in azacytidine responders includes hypomethylation of the γ-globin gene promoter region and hypermethylation of the CpG326 island of ZBTB7A. The association of these methylation patterns with blast clearance and their prognostic value for PFS paves the way to discuss in-depth azacytidine epigenetic mechanism of action.

Long noncoding RNA GATA2AS influences human erythropoiesis by transcription factor and chromatin landscape modulation

ABSTRACT

Long noncoding RNAs (lncRNAs) are extensively expressed in eukaryotic cells and have been revealed to be important for regulating cell differentiation. Many lncRNAs have been found to regulate erythroid differentiation in the mouse. However, given the low sequence conservation of lncRNAs between mouse and human, our understanding of lncRNAs in human erythroid differentiation remains incomplete. lncRNAs are often transcribed opposite to protein coding genes and regulate their expression. Here, we characterized a human erythrocyte-expressed lncRNA, GATA2AS, which is transcribed opposite to erythroid transcription regulator GATA2. GATA2AS is a 2080-bp long, primarily nucleus-localized noncoding RNA that is expressed in erythroid progenitor cells and decreases during differentiation. Knockout of GATA2AS in human HUDEP2 erythroid progenitor cells using CRISPR-Cas9 genome editing to remove the transcription start site accelerated erythroid differentiation and dysregulated erythroblast gene expression. We identified GATA2AS as a novel GATA2 and HBG activator. Chromatin isolation by RNA purification showed that GATA2AS binds to thousands of genomic sites and colocalizes at a subset of sites with erythroid transcription factors including LRF and KLF1. RNA pulldown and RNA immunoprecipitation confirmed interaction between GATA2AS and LRF and KLF1. Chromatin immunoprecipitation sequencing (ChIP-seq) showed that knockout of GATA2AS reduces binding of these transcription factors genome wide. Assay for transposase-accessible chromatin sequencing (ATAC-seq) and H3K27ac ChIP-seq showed that GATA2AS is essential to maintain the chromatin regulatory landscape during erythroid differentiation. Knockdown of GATA2AS in human primary CD34+ cells mimicked results in HUDEP2 cells. Overall, our results implicate human-specific lncRNA GATA2AS as a regulator of erythroid differentiation by influencing erythroid transcription factor binding and the chromatin regulatory landscape.

Novel insights into the ontogeny of basophils

Basophils are the least common granulocytes, accounting for <1% of peripheral blood leukocytes. In the last 20 years, analytical tools for mouse basophils have been developed, and we now recognize that basophils play critical roles in various immune reactions, including the development of allergic inflammation and protective immunity against parasites. Moreover, the combined use of flow cytometric analyses and knockout mice has uncovered several progenitor cells committed to basophils in mice. Recently, advancements in single-cell RNA sequencing (scRNA-seq) technologies have challenged the classical view of the differentiation of various hematopoietic cell lineages. This is also true for basophil differentiation, and studies using scRNA-seq analysis have provided novel insights into basophil differentiation, including the association of basophil differentiation with that of erythrocyte/megakaryocyte and the discovery of novel basophil progenitor cells in the mouse bone marrow. In this review, we summarize the recent findings of basophil ontogeny in both mice and humans, mainly focusing on studies using scRNA-seq analyses.

SUMOylation of zebrafish transcription factor Zbtb21 affects its transcription activity

Background

Post-translational modification by Small Ubiquitin-like MOdifier (SUMO) is an important mechanism to regulate protein activity, protein stability, and localization of substrates. Zbtb21 is a zinc finger and BTB (Broad-complex, Tram-track and Bric à brac) domain-containing transcription factor. Bioinformatic prediction suggests several putative SUMOylated sites in Zbtb21 protein.

Methods

Two evolutionarily conserved lysine residues in Zbtb21 protein were mutated alone or in combination to disrupt the binding with SUMO molecules. Western blot and co-immunoprecipitation analyses were performed to detect the SUMOylation state of wild type and mutant Zbtb21 proteins, respectively. Luciferase reporter assays were conducted to evaluate their transcription activities. Meanwhile, immunofluorescence staining was carried out to show their sub-nuclear localizations. Finally, co-immunoprecipitation was performed to detect the interaction between Zbtb21 and its partners.

Results

Phylogenetically conserved lysines 419 and 845 of zebrafish Zbtb21 protein can be conjugated with SUMO molecules. SUMOylation does not affect the subcellular localization and protein stability of Zbtb21, as well as the interaction with Zbtb14 or Zbtb21. Nevertheless, luciferase reporter assays revealed that Zbtb21 is a dual-function transcription factor which exerts activation or repression effect on different promoters, and SUMOylation can modulate the transcriptional activity of Zbtb21 in regulating downstream target genes. Hence, Zbtb21 is identified as a novel substrate of SUMOylation, which would be important for its function.

Conclusions

Zebrafish Zbtb21 protein can be SUMOylated on lysines 419 and 845, which is evolutionary conserved. SUMOylation affects the dual role of Zbtb21 on transcription.

Oncoprotein SET-associated transcription factor ZBTB11 triggers lung cancer metastasis

Metastasis is the major cause of lung cancer-related death, but the mechanisms governing lung tumor metastasis remain incompletely elucidated. SE translocation (SET) is overexpressed in lung tumors and correlates with unfavorable prognosis. Here we uncover SET-associated transcription factor, zinc finger and BTB domain-containing protein 11 (ZBTB11), as a prometastatic regulator in lung tumors. SET interacts and collaborates with ZBTB11 to promote lung cancer cell migration and invasion, primarily through SET-ZBTB11 complex-mediated transcriptional activation of matrix metalloproteinase-9 (MMP9). Additionally, by transcriptional repression of proline-rich Gla protein 2 (PRRG2), ZBTB11 links Yes-associated protein 1 (YAP1) activation to drive lung tumor metastasis independently of SET-ZBTB11 complex. Loss of ZBTB11 suppresses distal metastasis in a lung tumor mouse model. Overexpression of ZBTB11 is recapitulated in human metastatic lung tumors and correlates with diminished survival. Our study demonstrates ZBTB11 as a key metastatic regulator and reveals diverse mechanisms by which ZBTB11 modulates lung tumor metastasis.

Zbtb16 increases susceptibility of atrial fibrillation in type 2 diabetic mice via Txnip-Trx2 signaling

Atrial fibrillation (AF) is the most prevalent sustained cardiac arrhythmia, and recent epidemiological studies suggested type 2 diabetes mellitus (T2DM) is an independent risk factor for the development of AF. Zinc finger and BTB (broad-complex, tram-track and bric-a-brac) domain containing 16 (Zbtb16) serve as transcriptional factors to regulate many biological processes. However, the potential effects of Zbtb16 in AF under T2DM condition remain unclear. Here, we reported that db/db mice displayed higher AF vulnerability and Zbtb16 was identified as the most significantly enriched gene by RNA sequencing (RNA-seq) analysis in atrium. In addition, thioredoxin interacting protein (Txnip) was distinguished as the key downstream gene of Zbtb16 by Cleavage Under Targets and Tagmentation (CUT&Tag) assay. Mechanistically, increased Txnip combined with thioredoxin 2 (Trx2) in mitochondrion induced excess reactive oxygen species (ROS) release, calcium/calmodulin-dependent protein kinase II (CaMKII) overactivation, and spontaneous Ca2+ waves (SCWs) occurrence, which could be inhibited through atrial-specific knockdown (KD) of Zbtb16 or Txnip by adeno-associated virus 9 (AAV9) or Mito-TEMPO treatment. High glucose (HG)-treated HL-1 cells were used to mimic the setting of diabetic in vitro. Zbtb16-Txnip-Trx2 signaling-induced excess ROS release and CaMKII activation were also verified in HL-1 cells under HG condition. Furthermore, atrial-specific Zbtb16 or Txnip-KD reduced incidence and duration of AF in db/db mice. Altogether, we demonstrated that interrupting Zbtb16-Txnip-Trx2 signaling in atrium could decrease AF susceptibility via reducing ROS release and CaMKII activation in the setting of T2DM.

Zinc Finger and BTB Domain-Containing 20: A Newly Emerging Player in Pathogenesis and Development of Human Cancers

Zinc finger and BTB domain-containing 20 (ZBTB20), which was initially identified in human dendritic cells, belongs to a family of transcription factors (TFs) with an N-terminal BTB domain and one or more C-terminal DNA-binding zinc finger domains. Under physiological conditions, ZBTB20 acts as a transcriptional repressor in cellular development and differentiation, metabolism, and innate immunity. Interestingly, multiple lines of evidence from mice and human systems have revealed the importance of ZBTB20 in the pathogenesis and development of cancers. ZBTB20 is not only a hotspot of genetic variation or fusion in many types of human cancers, but also a key TF or intermediator involving in the dysregulation of cancer cells. Given the diverse functions of ZBTB20 in both health and disease, we herein summarize the structure and physiological roles of ZBTB20, with an emphasis on the latest findings on tumorigenesis and cancer progression.

Dimerization choice and alternative functions of ZBTB transcription factors

Zinc Finger DNA-binding domain-containing proteins are the most populous family among eukaryotic transcription factors. Among these, members of the BTB domain-containing ZBTB sub-family are mostly known for their transcriptional repressive functions. In this Viewpoint article, we explore molecular mechanisms that potentially diversify the function of ZBTB proteins based on their homo and heterodimerization, alternative splicing and post-translational modifications. We describe how the BTB domain is as much a scaffold for the assembly of co-repressors, as a domain that regulates protein stability. We highlight another mechanism that regulates ZBTB protein stability: phosphorylation in the zinc finger domain. We explore the non-transcriptional, structural roles of ZBTB proteins and highlight novel findings that describe the ability of ZBTB proteins to associate with poly adenosine ribose in the nucleus during the DNA damage response. Herein, we discuss the contribution of BTB domain scaffolds to the formation of transcriptional repressive complexes, to chromosome compartmentalization and their non-transcriptional, purely structural functions in the nucleus.

A review of the role of zinc finger proteins on hematopoiesis

The bone marrow is responsible for producing an incredible number of cells daily in order to maintain blood homeostasis through a process called hematopoiesis. Hematopoiesis is a greatly demanding process and one entirely dependent on complex interactions between the hematopoietic stem cell (HSC) and its surrounding microenvironment. Zinc (Zn2+) is considered an important trace element, playing diverse roles in different tissues and cell types, and zinc finger proteins (ZNF) are proteins that use Zn2+ as a structural cofactor. In this way, the ZNF structure is supported by a Zn2+ that coordinates many possible combinations of cysteine and histidine, with the most common ZNF being of the Cys2His2 (C2H2) type, which forms a family of transcriptional activators that play an important role in different cellular processes such as development, differentiation, and suppression, all of these being essential processes for an adequate hematopoiesis. This review aims to shed light on the relationship between ZNF and the regulation of the hematopoietic tissue. We include works with different designs, including both in vitro and in vivo studies, detailing how ZNF might regulate hematopoiesis.

Late fetal hematopoietic failure results from ZBTB11 deficiency despite abundant HSC specification

Hematopoiesis produces diverse blood cell lineages to meet the basal needs and sudden demands of injury or infection. A rapid response to such challenges requires the expansion of specific lineages and a prompt return to balanced steady-state levels, necessitating tightly coordinated regulation. Previously we identified a requirement for the zinc finger and broad complex, tramtrak, bric-a-brac domain-containing 11 (ZBTB11) transcription factor in definitive hematopoiesis using a forward genetic screen for zebrafish myeloid mutants. To understand its relevance to mammalian systems, we extended these studies to mice. When Zbtb11 was deleted in the hematopoietic compartment, embryos died at embryonic day (E) 18.5 with hematopoietic failure. Zbtb11 hematopoietic knockout (Zbtb11hKO) hematopoietic stem cells (HSCs) were overabundantly specified from E14.5 to E17.5 compared with those in controls. Overspecification was accompanied by loss of stemness, inability to differentiate into committed progenitors and mature lineages in the fetal liver, failure to seed fetal bone marrow, and total hematopoietic failure. The Zbtb11hKO HSCs did not proliferate in vitro and were constrained in cell cycle progression, demonstrating the cell-intrinsic role of Zbtb11 in proliferation and cell cycle regulation in mammalian HSCs. Single-cell RNA sequencing analysis identified that Zbtb11-deficient HSCs were underrepresented in an erythroid-primed subpopulation and showed downregulation of oxidative phosphorylation pathways and dysregulation of genes associated with the hematopoietic niche. We identified a cell-intrinsic requirement for Zbtb11-mediated gene regulatory networks in sustaining a pool of maturation-capable HSCs and progenitor cells.

The N-Terminal Part of Drosophila CP190 Is a Platform for Interaction with Multiple Architectural Proteins

CP190 is a co-factor in many Drosophila architectural proteins, being involved in the formation of active promoters and insulators. CP190 contains the N-terminal BTB/POZ (Broad-Complex, Tramtrack and Bric a brac/POxvirus and Zinc finger) domain and adjacent conserved regions involved in protein interactions. Here, we examined the functional roles of these domains of CP190 in vivo. The best-characterized architectural proteins with insulator functions, Pita, Su(Hw), and dCTCF, interacted predominantly with the BTB domain of CP190. Due to the difficulty of mutating the BTB domain, we obtained a transgenic line expressing a chimeric CP190 with the BTB domain of the human protein Kaiso. Another group of architectural proteins, M1BP, Opbp, and ZIPIC, interacted with one or both of the highly conserved regions in the N-terminal part of CP190. Transgenic lines of D. melanogaster expressing CP190 mutants with a deletion of each of these domains were obtained. The results showed that these mutant proteins only partially compensated for the functions of CP190, weakly binding to selective chromatin sites. Further analysis confirmed the essential role of these domains in recruitment to regulatory regions associated with architectural proteins. We also found that the N-terminal of CP190 was sufficient for recruiting Z4 and Chromator proteins and successfully achieving chromatin opening. Taken together, our results and the results of previous studies showed that the N-terminal region of CP190 is a platform for simultaneous interaction with various DNA-binding architectural proteins and transcription complexes.

Characterizing control of memory CD8 T cell differentiation by BTB-ZF transcription factor Zbtb20

Members of the BTB-ZF transcription factor family regulate the immune system. Our laboratory identified that family member Zbtb20 contributes to the differentiation, recall responses, and metabolism of CD8 T cells. Here, we report a characterization of the transcriptional and epigenetic signatures controlled by Zbtb20 at single-cell resolution during the effector and memory phases of the CD8 T cell response. Without Zbtb20, transcriptional programs associated with memory CD8 T cell formation were up-regulated throughout the CD8 T response. A signature of open chromatin was associated with genes controlling T cell activation, consistent with the known impact on differentiation. In addition, memory CD8 T cells lacking Zbtb20 were characterized by open chromatin regions with overrepresentation of AP-1 transcription factor motifs and elevated RNA- and protein-level expressions of the corresponding AP-1 components. Finally, we describe motifs and genomic annotations from the DNA targets of Zbtb20 in CD8 T cells identified by cleavage under targets and release under nuclease (CUT&RUN). Together, these data establish the transcriptional and epigenetic networks contributing to the control of CD8 T cell responses by Zbtb20.

Multiomic analysis of cohesin reveals that ZBTB transcription factors contribute to chromatin interactions

One bottleneck in understanding the principles of 3D chromatin structures is caused by the paucity of known regulators. Cohesin is essential for 3D chromatin organization, and its interacting partners are candidate regulators. Here, we performed proteomic profiling of the cohesin in chromatin and identified transcription factors, RNA-binding proteins and chromatin regulators associated with cohesin. Acute protein degradation followed by time-series genomic binding quantitation and BAT Hi-C analysis were conducted, and the results showed that the transcription factor ZBTB21 contributes to cohesin chromatin binding, 3D chromatin interactions and transcriptional repression. Strikingly, multiomic analyses revealed that the other four ZBTB factors interacted with cohesin, and double degradation of ZBTB21 and ZBTB7B led to a further decrease in cohesin chromatin occupancy. We propose that multiple ZBTB transcription factors orchestrate the chromatin binding of cohesin to regulate chromatin interactions, and we provide a catalog of many additional proteins associated with cohesin that warrant further investigation.

Precision Editing as a Therapeutic Approach for β-Hemoglobinopathies

Beta-hemoglobinopathies are the most common genetic disorders worldwide, caused by a wide spectrum of mutations in the β-globin locus, and associated with morbidity and early mortality in case of patient non-adherence to supportive treatment. Allogeneic transplantation of hematopoietic stem cells (allo-HSCT) used to be the only curative option, although the indispensable need for an HLA-matched donor markedly restricted its universal application. The evolution of gene therapy approaches made possible the ex vivo delivery of a therapeutic β- or γ- globin gene into patient-derived hematopoietic stem cells followed by the transplantation of corrected cells into myeloablated patients, having led to high rates of transfusion independence (thalassemia) or complete resolution of painful crises (sickle cell disease-SCD). Hereditary persistence of fetal hemoglobin (HPFH), a syndrome characterized by increased γ-globin levels, when co-inherited with β-thalassemia or SCD, converts hemoglobinopathies to a benign condition with mild clinical phenotype. The rapid development of precise genome editing tools (ZFN, TALENs, CRISPR/Cas9) over the last decade has allowed the targeted introduction of mutations, resulting in disease-modifying outcomes. In this context, genome editing tools have successfully been used for the introduction of HPFH-like mutations both in HBG1/HBG2 promoters or/and in the erythroid enhancer of BCL11A to increase HbF expression as an alternative curative approach for β-hemoglobinopathies. The current investigation of new HbF modulators, such as ZBTB7A, KLF-1, SOX6, and ZNF410, further expands the range of possible genome editing targets. Importantly, genome editing approaches have recently reached clinical translation in trials investigating HbF reactivation in both SCD and thalassemic patients. Showing promising outcomes, these approaches are yet to be confirmed in long-term follow-up studies.

ZBTB2 is recruited to a specific subset of HIF-1 target loci to facilitate full gene expression under hypoxia

The cellular response to hypoxia is mainly governed by a transcription factor, hypoxia-inducible factor 1 (HIF-1). Although upregulation of HIF-1 target genes has been hypothesized to require interaction of HIF-1 with other coactivators, much remains to be elucidated regarding the underlying mechanisms. Here, we demonstrate that zinc finger and BTB domain-containing protein 2 (ZBTB2) enhances the expression of certain HIF-1 target genes under hypoxia. ChIP-Seq analysis showed that there is a subset of HIF-1 target genes with overlapping HIF-1 and ZBTB2 peaks. Examination of a representative gene, EGFR antisense RNA 1 (EGFR-AS1), showed that HIF-1 binding to the consensus hypoxia-responsive element (HRE) sequence resulted in the recruitment of ZBTB2 to the gene locus and increased p300-mediated histone acetylation, leading to enhanced gene expression under hypoxia. In contrast, expression of HIF-1 target genes lacking ZBTB2 peaks, such as carbonic anhydrase 9 (CA9), was not upregulated by ZBTB2. These findings demonstrate that ZBTB2 is a novel factor that can be recruited to the vicinity of HREs on a subset of HIF-1 target gene loci, and is required for their full expression under hypoxia.

Zbtb40 Deficiency Leads to Morphological and Phenotypic Abnormalities of Spermatocytes and Spermatozoa and Causes Male Infertility

Studies on the gene regulation of spermatogenesis are of unusual significance for maintaining male reproduction and treating male infertility. Here, we have demonstrated, for the first time, that a loss of ZBTB40 function leads to abnormalities in the morphological and phenotypic characteristics of mouse spermatocytes and spermatids as well as male infertility. We revealed that Zbtb40 was expressed in spermatocytes of mouse testes, and it was co-localized with γH2AX in mouse secondary spermatocytes. Interestingly, spermatocytes of Zbtb40 knockout mice had longer telomeres, compromised double-strand break (DSB) repair in the sex chromosome, and a higher apoptosis ratio compared to wild-type (WT) mice. The testis weight, testicular volume, and cauda epididymis body weight of the Zbtb40^+/- male mice were significantly lower than in WT mice. Mating tests indicated that Zbtb40^+/- male mice were able to mate normally, but they failed to produce any pups. Notably, sperm of Zbtb40^+/- mice showed flagellum deformities and abnormal acrosome biogenesis. Furthermore, a ZBTB40 mutation was associated with non-obstructive azoospermia. Our results implicate that ZBTB40 deficiency leads to morphological and phenotypic abnormalities of spermatocytes and spermatids and causes male infertility. This study thus offers a new genetic mechanism regulating mammalian spermatogenesis and provides a novel target for gene therapy in male infertility.

ZBTB7A suppresses glioblastoma tumorigenesis through the transcriptional repression of EPB41L5

Glioblastoma multiforme (GBM), the most aggressive and malignant glioma, has a poor prognosis. Although patients with GBM are treated with surgery, chemotherapy, and radiation therapy, GBM is highly resistant to treatment, making it difficult and expensive to treat. In this study, we analyzed the Gene Expression Profiling Interactive Analysis dataset, the Cancer Genome Atlas dataset, and Gene Expression Omnibus array data. ZBTB7A (also called FBI1/POKEMON/LRF) was found to be highly expressed in low-grade glioma but significantly downregulated in patients with GBM. ZBTB7A is a transcription factor that plays an important role in many developmental stages, including cell proliferation. The activation of epithelial-mesenchymal transition (EMT) is a key process in cancer progression and metastasis. Erythrocyte membrane protein band 4.1 like 5 (EPB41L5) is an essential protein for EMT progression and metastasis in various types of cancer. We found that ZBTB7A depletion in U87 cells induced GBM progression and metastasis. Based on RNA sequencing data, ZBTB7A directly binds to the promoter of the EPB41L5 gene, reducing its expression and inhibiting GBM progression. We demonstrated that ZBTB7A dramatically inhibits GBM tumor growth through transcriptional repression of EPB41L5. Thus, both ZBTB7A and EPB41L5 may be potential biomarkers and novel therapeutic targets for GBM treatment. Overall, we discovered the role of a novel tumor suppressor that directly inhibits GBM progression (ZBTB7A) and identified EPB41L5 as a therapeutic target protein for patients with GBM.

The remodeling of Z-DNA in the mammalian germ line

We recently discovered a novel biological process, the scheduled remodeling of Z-DNA structures in the developing fetal mouse male germ cells [Nat. Cell Biol. 24, 1141-1153]. This process affects purine/pyrimidine dinucleotide repeat (PPR) rich sequences, which can form stable left-handed Z-DNA structures. The protein that carries out this function is identified as ZBTB43, member of a large family of ZBTB proteins. Z-DNA remodeling by ZBTB43 not only coincides with global remodeling of DNA methylation and chromatin events in the male germ line, but it also is a prerequisite for de novo DNA methylation. When ZBTB43 changes DNA structure from the left-handed zigzag shaped Z-DNA to the regular smooth right-handed B-DNA, it also generates a suitable substrate for the de novo DNA methyltransferase, DNMT3A. By instructing de novo DNA methylation at PPRs in prospermatogonia, ZBTB43 safeguards epigenomic integrity of the male gamete. PPRs are fragile sequences, sites of large deletions and rearrangements in mammalian cells, and this fragility is thought to be due to Z-DNA structure formation rather than the sequence itself. This idea is now supported by the in vivo finding that DNA double strand breaks accumulate in mutant prospermatogonia which lack ZBTB43-dependent Z-DNA remodeling. If unrepaired, double stranded DNA breaks can lead to germ line mutations. Therefore, by preventing such breaks ZBTB43 is critical for guarding genome stability between generations. Here, we discuss the significance and implications of these findings in more detail.

The N6-methyladenosine methyltransferase METTL16 enables erythropoiesis through safeguarding genome integrity

During erythroid differentiation, the maintenance of genome integrity is key for the success of multiple rounds of cell division. However, molecular mechanisms coordinating the expression of DNA repair machinery in erythroid progenitors are poorly understood. Here, we discover that an RNA N⁶-methyladenosine (m⁶A) methyltransferase, METTL16, plays an essential role in proper erythropoiesis by safeguarding genome integrity via the control of DNA-repair-related genes. METTL16-deficient erythroblasts exhibit defective differentiation capacity, DNA damage and activation of the apoptotic program. Mechanistically, METTL16 controls m⁶A deposition at the structured motifs in DNA-repair-related transcripts including Brca2 and Fancm mRNAs, thereby upregulating their expression. Furthermore, a pairwise CRISPRi screen revealed that the MTR4-nuclear RNA exosome complex is involved in the regulation of METTL16 substrate mRNAs in erythroblasts. Collectively, our study uncovers that METTL16 and the MTR4-nuclear RNA exosome act as essential regulatory machinery to maintain genome integrity and erythropoiesis.

Leukemia/lymphoma-related factor (LRF) or osteoclast zinc finger protein (OCZF) overexpression promotes osteoclast survival by increasing Bcl-xl mRNA: A novel regulatory mechanism mediated by the RNA binding protein SAM68

RANKL induces NFATc1, a key transcriptional factor to induce osteoclast-specific genes such as cathepsin K, whereas transcriptional control of osteoclast survival is not fully understood. Leukemia/lymphoma-related factor (LRF) in mouse and osteoclast zinc finger protein (OCZF) in rat are zinc finger and BTB domain-containing protein (zBTB) family of transcriptional regulators, and are critical regulators of hematopoiesis. We have previously shown that differentiation and survival were enhanced in osteoclasts from OCZF-Transgenic (Tg) mice. In the present study, we show a possible mechanism of osteoclast survival regulated by LRF/OCZF and the role of OCZF overexpression in pathological bone loss. In the in vitro cultures, LRF was highly colocalized with NFATc1 in cells of early stage in osteoclastogenesis, but only LRF expression persisted after differentiation into mature osteoclasts. LRF expression was further enhanced in resorbing osteoclasts formed on dentin slices. Osteoclast survival inhibitor such as alendronate, a bisphosphonate reduced LRF expression. Micro CT evaluation revealed that femurs of OCZF-Tg mice showed significantly lower bone volume compared to that of WT mice. Furthermore, OCZF overexpression markedly promoted bone loss in ovariectomy-induced osteolytic mouse model. The expression of anti-apoptotic Bcl-xl mRNA, which is formed by alternative splicing, was enhanced in the cultures in which osteoclasts are formed from OCZF-Tg mice. In contrast, the expression of pro-apoptotic Bcl-xs mRNA was lost in the culture derived from OCZF-Tg mice. We found that the expression levels of RNA binding splicing regulator, Src substrate associated in mitosis of 68 kDa (Sam68) protein were markedly decreased in OCZF-Tg mice-derived osteoclasts. In addition, shRNA-mediated knockdown of Sam68 expression increased the expression of Bcl-xl mRNA, suggesting that SAM68 regulates the expression of Bcl-xl. These results indicate that OCZF overexpression reduces protein levels of Sam68, thereby promotes osteoclast survival, and suggest that LRF/OCZF is a promising target for regulating pathological bone loss.

An enhancer located in a Pde6c intron drives transient expression in the cone photoreceptors of developing mouse and human retinas

How cone photoreceptors are formed during retinal development is only partially known. This is in part because we do not fully understand the gene regulatory network responsible for cone genesis. We reasoned that cis-regulatory elements (enhancers) active in nascent cones would be regulated by the same upstream network that controls cone formation. To dissect this network, we searched for enhancers active in developing cones. By electroporating enhancer-driven fluorescent reporter plasmids, we observed that a sequence within an intron of the cone-specific Pde6c gene acted as an enhancer in developing mouse cones. Similar fluorescent reporter plasmids were used to generate stable transgenic human induced pluripotent stem cells that were then grown into three-dimensional human retinal organoids. These organoids contained fluorescently labeled cones, demonstrating that the Pde6c enhancer was also active in human cones. We observed that enhancer activity was transient and labeled a minor population of developing rod photoreceptors in both mouse and human systems. This cone-enriched pattern argues that the Pde6c enhancer is activated in cells poised between rod and cone fates. Additionally, it suggests that the Pde6c enhancer is activated by the same regulatory network that selects or stabilizes cone fate choice. To further understand this regulatory network, we identified essential enhancer sequence regions through a series of mutagenesis experiments. This suggested that the Pde6c enhancer was regulated by transcription factor binding at five or more locations. Binding site predictions implicated transcription factor families known to control photoreceptor formation and families not previously associated with cone development. These results provide a framework for deciphering the gene regulatory network that controls cone genesis in both human and mouse systems. Our new transgenic human stem cell lines provide a tool for determining which cone developmental mechanisms are shared and distinct between mice and humans.

The transcription factor LRF promotes integrin β7 expression by and gut homing of CD8αα+ intraepithelial lymphocyte precursors

While T cell receptor (TCR) αβ+CD8α+CD8β- intraepithelial lymphocytes (CD8αα+ IELs) differentiate from thymic IEL precursors (IELps) and contribute to gut homeostasis, the transcriptional control of their development remains poorly understood. In the present study we showed that mouse thymocytes deficient for the transcription factor leukemia/lymphoma-related factor (LRF) failed to generate TCRαβ+CD8αα+ IELs and their CD8β-expressing counterparts, despite giving rise to thymus and spleen CD8αβ+ T cells. LRF-deficient IELps failed to migrate to the intestine and to protect against T cell-induced colitis, and had impaired expression of the gut-homing integrin α4β7. Single-cell RNA-sequencing found that LRF was necessary for the expression of genes characteristic of the most mature IELps, including Itgb7, encoding the β7 subunit of α4β7. Chromatin immunoprecipitation and gene-regulatory network analyses both defined Itgb7 as an LRF target. Our study identifies LRF as an essential transcriptional regulator of IELp maturation in the thymus and subsequent migration to the intestinal epithelium.

Down-regulation of the transcriptional repressor ZNF802 (JAZF1) reactivates fetal hemoglobin in β0-thalassemia/HbE

Reactivating of fetal hemoglobin (HbF; α2γ2) can ameliorate the severity of β-thalassemia disease by compensating for adult hemoglobin deficiency in patients. Previously, microarray analysis revealed that zinc finger protein (ZNF)802 (also known as Juxta-posed with another zinc finger gene-1 (JAZF1)) was upregulated in human erythroblasts derived from adult peripheral blood compared with fetal liver-derived cells, implying a potential role as a HbF repressor. However, deficiency in ZNF802 induced by lentiviral shRNA in β⁰-thalassemia/hemoglobinE erythroblasts had no effect on erythroblast proliferation and differentiation. Remarkably, the induction of HBG expression was observed at the transcriptional and translational levels resulting in an increase of HbF to 35.0 ± 3.5%. Interestingly, the embryonic globin transcripts were also upregulated but the translation of embryonic globin was not detected. These results suggest ZNF802 might be a transcriptional repressor of the γ-globin gene in adult erythroid cells.

The BTB transcription factors ZBTB11 and ZFP131 maintain pluripotency by repressing pro-differentiation genes

In pluripotent cells, a delicate activation-repression balance maintains pro-differentiation genes ready for rapid activation. The identity of transcription factors (TFs) that specifically repress pro-differentiation genes remains obscure. By targeting ∼1,700 TFs with CRISPR loss-of-function screen, we found that ZBTB11 and ZFP131 are required for embryonic stem cell (ESC) pluripotency. ESCs without ZBTB11 or ZFP131 lose colony morphology, reduce proliferation rate, and upregulate transcription of genes associated with three germ layers. ZBTB11 and ZFP131 bind proximally to pro-differentiation genes. ZBTB11 or ZFP131 loss leads to an increase in H3K4me3, negative elongation factor (NELF) complex release, and concomitant transcription at associated genes. Together, our results suggest that ZBTB11 and ZFP131 maintain pluripotency by preventing premature expression of pro-differentiation genes and present a generalizable framework to maintain cellular potency.

Discovery of a novel megakaryopoiesis enhancer, ingenol, promoting thrombopoiesis through PI3K-Akt signaling independent of thrombopoietin

Thrombocytopenia, a most common complication of radiotherapy and chemotherapy, is an important cause of morbidity and mortality in cancer patients. However, there are still no approved agents for the treatment of radiation- and chemotherapy-induced thrombocytopenia (RIT and CIT, respectively). In this study, a drug screening model for predicting compounds with activity in promoting megakaryocyte (MK) differentiation and platelet production was established based on machine learning (ML), and a natural product ingenol was predicted as a potential active compound. Then, in vitro experiments showed that ingenol significantly promoted MK differentiation in K562 and HEL cells. Furthermore, a RIT mice model and c-MPL knock-out (c-MPL^-/-) mice constructed by CRISPR/Cas9 technology were used to assess the therapeutic action of ingenol on thrombocytopenia. The results showed that ingenol accelerated megakaryopoiesis and thrombopoiesis both in RIT mice and c-MPL^-/- mice. Next, RNA-sequencing (RNA-seq) was carried out to analyze the gene expression profile induced by ingenol during MK differentiation. Finally, through experimental verifications, we demonstrated that the activation of PI3K/Akt signaling pathway was involved in ingenol-induced MK differentiation. Blocking PI3K/Akt signaling pathway abolished the promotion of ingenol on MK differentiation. Nevertheless, inhibition of TPO/c-MPL signaling pathway could not suppress ingenol-induced MK differentiation. In conclusion, our study builds a drug screening model to discover active compounds against thrombocytopenia, reveals the critical roles of ingenol in promoting MK differentiation and platelet production, and provides a promising avenue for the treatment of RIT.

OUP accepted manuscript

AIMS

Arrhythmogenic cardiomyopathy (ACM) is an inherited cardiac disorder that is characterized by progressive loss of myocardium that is replaced by fibro-fatty cells, arrhythmias, and sudden cardiac death. While myocardial degeneration and fibro-fatty replacement occur in specific locations, the underlying molecular changes remain poorly characterized. Here, we aim to delineate local changes in gene expression to identify new genes and pathways that are relevant for specific remodelling processes occurring during ACM.

METHODS AND RESULTS

Using Tomo-Seq, genome-wide transcriptional profiling with high spatial resolution, we created transmural epicardial-to-endocardial gene expression atlases of explanted ACM hearts to gain molecular insights into disease-driving processes. This enabled us to link gene expression profiles to the different regional remodelling responses and allowed us to identify genes that are potentially relevant for disease progression. In doing so, we identified distinct gene expression profiles marking regions of cardiomyocyte degeneration and fibro-fatty remodelling and revealed Zinc finger and BTB domain-containing protein 11 (ZBTB11) to be specifically enriched at sites of active fibro-fatty replacement of myocardium. Immunohistochemistry indicated ZBTB11 to be induced in cardiomyocytes flanking fibro-fatty areas, which could be confirmed in multiple cardiomyopathy patients. Forced overexpression of ZBTB11 induced autophagy and cell death-related gene programmes in human cardiomyocytes, leading to increased apoptosis.

CONCLUSION

Our study shows the power of Tomo-Seq to unveil new molecular mechanisms in human cardiomyopathy and uncovers ZBTB11 as a novel driver of cardiomyocyte loss.

Whole-transcriptome analysis in acute lymphoblastic leukemia: a report from the DFCI ALL Consortium Protocol 16-001

RNA-seq is feasible in the context of a prospective clinical trial for de novo ALL within a clinically sensitive turnaround time.

RNA-seq identified several genetic alterations not detected by conventional methods that confer potential prognostic and therapeutic impact.

The molecular hallmark of childhood acute lymphoblastic leukemia (ALL) is characterized by recurrent, prognostic genetic alterations, many of which are cryptic by conventional cytogenetics. RNA sequencing (RNA-seq) is a powerful next-generation sequencing technology that can simultaneously identify cryptic gene rearrangements, sequence mutations and gene expression profiles in a single assay. We examined the feasibility and utility of incorporating RNA-seq into a prospective multicenter phase 3 clinical trial for children with newly diagnosed ALL. The Dana-Farber Cancer Institute ALL Consortium Protocol 16-001 enrolled 173 patients with ALL who consented to optional studies and had samples available for RNA-seq. RNA-seq identified at least 1 alteration in 157 patients (91%). Fusion detection was 100% concordant with results obtained from conventional cytogenetic analyses. An additional 56 gene fusions were identified by RNA-seq, many of which confer prognostic or therapeutic significance. Gene expression profiling enabled further molecular classification into the following B-cell ALL (B-ALL) subgroups: high hyperdiploid (n = 36), ETV6-RUNX1/-like (n = 31), TCF3-PBX1 (n = 7), KMT2A-rearranged (KMT2A-R; n = 5), intrachromosomal amplification of chromosome 21 (iAMP21) (n = 1), hypodiploid (n = 1), Philadelphia chromosome (Ph)-positive/Ph-like (n = 16), DUX4-R (n = 11), PAX5 alterations (PAX5 alt; n = 11), PAX5 P80R (n = 1), ZNF384-R (n = 4), NUTM1-R (n = 1), MEF2D-R (n = 1), and others (n = 10). RNA-seq identified 141 nonsynonymous mutations in 93 patients (54%); the most frequent were RAS-MAPK pathway mutations. Among 79 patients with both low-density array and RNA-seq data for the Philadelphia chromosome-like gene signature prediction, results were concordant in 74 patients (94%). In conclusion, RNA-seq identified several clinically relevant genetic alterations not detected by conventional methods, which supports the integration of this technology into front-line pediatric ALL trials. This trial was registered at www.clinicaltrials.gov as #NCT03020030.

Comprehensive transcriptome characterization of Grus japonensis using PacBio SMRT and Illumina sequencing

The red-crowned crane (Grus japonensis) is an endangered species distributed across southeast Russia, northeast China, Korea, and Japan. Here, we sequenced for the first time the full-length unreferenced transcriptome of red-crowned crane mixed samples using a PacBio Sequel platform. A total of 359,136 circular consensus sequences (CCS) were obtained via clustering to remove redundancy. A total of 303,544 full-length non-chimeric sequences were identified by judging whether CCS contained 5' and 3' adapters, and the poly(A) tail. Eight samples were sequenced using Illumina, and PacBio sequencing data were corrected according to the collected Illumina data to obtain more accurate full-length transcripts. A total of 4,100 long non-coding RNAs, 13,115 simple sequences repeat loci and 29 transcription factor families were identified. The expression of lncRNAs and TFs in pancreas was lowest comparing with other tissues. Many enriched immune-related transmission pathways (MHC and IL receptors) were identified in the spleen. This study will contribute to a better understanding of the gene structure and post-transcriptional regulatory network, and provide references for future studies on red-crowned cranes.

ZBTB Transcription Factors: Key Regulators of the Development, Differentiation and Effector Function of T Cells

The development and differentiation of T cells represents a long and highly coordinated, yet flexible at some points, pathway, along which the sequential and dynamic expressions of different transcriptional factors play prominent roles at multiple steps. The large ZBTB family comprises a diverse group of transcriptional factors, and many of them have emerged as critical factors that regulate the lineage commitment, differentiation and effector function of hematopoietic-derived cells as well as a variety of other developmental events. Within the T-cell lineage, several ZBTB proteins, including ZBTB1, ZBTB17, ZBTB7B (THPOK) and BCL6 (ZBTB27), mainly regulate the development and/or differentiation of conventional CD4/CD8 αβ⁺ T cells, whereas ZBTB16 (PLZF) is essential for the development and function of innate-like unconventional γδ⁺ T & invariant NKT cells. Given the critical role of T cells in host defenses against infections/tumors and in the pathogenesis of many inflammatory disorders, we herein summarize the roles of fourteen ZBTB family members in the development, differentiation and effector function of both conventional and unconventional T cells as well as the underlying molecular mechanisms.

The BTB-domain transcription factor ZBTB2 recruits chromatin remodelers and a histone chaperone during the exit from pluripotency

Transcription factors (TFs) harboring broad-complex, tramtrack, and bric-a-brac (BTB) domains play important roles in development and disease. These BTB domains are thought to recruit transcriptional modulators to target DNA regions. However, a systematic molecular understanding of the mechanism of action of this TF family is lacking. Here, we identify the zinc finger BTB-TF Zbtb2 from a genetic screen for regulators of exit from pluripotency and demonstrate that its absence perturbs embryonic stem cell differentiation and the gene expression dynamics underlying peri-implantation development. We show that ZBTB2 binds the chromatin remodeler Ep400 to mediate downstream transcription. Independently, the BTB domain directly interacts with nucleosome remodeling and deacetylase and histone chaperone histone regulator A. Nucleosome remodeling and deacetylase recruitment is a common feature of BTB TFs, and based on phylogenetic analysis, we propose that this is a conserved evolutionary property. Binding to UBN2, in contrast, is specific to ZBTB2 and requires a C-terminal extension of the BTB domain. Taken together, this study identifies a BTB-domain TF that recruits chromatin modifiers and a histone chaperone during a developmental cell state transition and defines unique and shared molecular functions of the BTB-domain TF family.

Zbtb46-dependent altered developmental program in embryonic stem cell-derived blood cell progenitors

Zbtb46 is a recently identified dendritic cell (DC)-specific transcription factor with poorly defined biology. Although Zbtb46 is highly expressed in conventional DCs, evidence also points to its presence in erythroid progenitors and endothelial cells suggesting that this factor might influence the early hematopoietic development. Here, we probe the effect of this transcription factor in embryonic stem cell (ESC)-derived blood cell progenitors using chemically inducible mouse cell lines. Unexpectedly, forced expression of this protein elicited a broad repressive effect at the early stage of ESC differentiation. Ectopic expression of Zbtb46 interfered with the mesoderm formation and cell proliferation was also negatively impacted. More importantly, reduced number of CD11b+ myeloid blood cells were generated from ESC-derived Flk1+ mesoderm cells in the presence of Zbtb46. Consistent with this finding, our gene expression profiling revealed that numerous myeloid and immune response related genes, including Irf8, exhibited lower expression in the Zbtb46-primed cells. Despite these repressive effects, however, Zbtb46 overexpression was associated with enhanced formation of erythroid blood cell colonies and increased adult hemoglobin (Hbb-b1) expression at the early phase of ESC differentiation. Moreover, elevated percent of CD105 (Endoglin) positive cells were detected in the Zbtb46-primed samples. In summary, our results support that Zbtb46 suppresses the ESC-derived myeloid development and diverts mesoderm cells toward erythroid developmental pathway. Moreover, our transcriptomic data provide a resource for exploration of the Zbtb46 regulatory network in ESC-derived progenitors.

Role of ZBTB7A zinc finger in tumorigenesis and metastasis

The zinc finger and BTB (broad-complex, tramtrack and bric a brac) domain containing protein 7A (ZBTB7A) is a pleiotropic transcription factor that plays an important role in various stages of cell proliferation, differentiation, and other developmental processes. ZBTB7A is a member of the POK family that directly and specifically binds to short DNA recognition sites located near their target genes thereby acting as transcriptional activator or repressor. ZBTB7A overexpression has been associated with tumorigenesis and metastasis in various human cancer types, including breast, prostate, lung, ovarian, and colon cancer. However in some instances downregulation of ZBTB7A results in tumor progression, suggesting its role as a tumor suppressor. ZBTB7A is involved with complicated regulatory networks which include protein-protein and protein-nucleic acid interactions. ZBTB7A involvement in cancer progression and metastasis is perhaps enabled through the regulation of various signaling pathways depending on the type and genetic context of cancer. The association of ZBTB7A with other proteins affects cancer aggressiveness, therapeutic resistance and clinical outcome. This review focuses on the involvement of ZBTB7A in various signaling pathways and its role in cancer progression. We will also review the literature on ZBTB7A and cancer which could be potentially explored for its therapeutic implications.

ZNF410 represses fetal globin by singular control of CHD4

Known fetal hemoglobin (HbF) silencers have potential on-target liabilities for rational β-hemoglobinopathy therapeutic inhibition. Here, through transcription factor (TF) CRISPR screening, we identify zinc-finger protein (ZNF) 410 as an HbF repressor. ZNF410 does not bind directly to the genes encoding γ-globins, but rather its chromatin occupancy is concentrated solely at CHD4, encoding the NuRD nucleosome remodeler, which is itself required for HbF repression. CHD4 has two ZNF410-bound regulatory elements with 27 combined ZNF410 binding motifs constituting unparalleled genomic clusters. These elements completely account for the effects of ZNF410 on fetal globin repression. Knockout of ZNF410 or its mouse homolog Zfp410 reduces CHD4 levels by 60%, enough to substantially de-repress HbF while eluding cellular or organismal toxicity. These studies suggest a potential target for HbF induction for β-hemoglobin disorders with a wide therapeutic index. More broadly, ZNF410 represents a special class of gene regulator, a conserved TF with singular devotion to regulation of a chromatin subcomplex.

The Zinc Finger Protein Zbtb18 Represses Expression of Class I Phosphatidylinositol 3-Kinase Subunits and Inhibits Plasma Cell Differentiation

The Zinc finger protein, Zbtb18, is downregulated during PC differentiation.

Enhanced expression of Zbtb18 leads to impaired PC development.

Zbtb18 directly binds and inhibits expression of PI3K subunits.

The PI3K pathway plays a key role in B cell activation and is important for the differentiation of Ab producing plasma cells (PCs). Although much is known about the molecular mechanisms that modulate PI3K signaling in B cells, the transcriptional regulation of PI3K expression is poorly understood. In this study, we identify the zinc finger protein Zbtb18 as a transcriptional repressor that directly binds enhancer/promoter regions of genes encoding class I PI3K regulatory subunits, subsequently limiting their expression, dampening PI3K signaling and suppressing PC responses. Following activation, dividing B cells progressively downregulated Zbtb18, allowing gradual amplification of PI3K signals and enhanced development of PCs. Human Zbtb18 displayed similar expression patterns and function in human B cells, acting to inhibit development of PCs. Furthermore, a number of Zbtb18 mutants identified in cancer patients showed loss of suppressor activity, which was also accompanied by impaired regulation of PI3K genes. Taken together, our study identifies Zbtb18 as a repressor of PC differentiation and reveals its previously unappreciated function as a transcription modulator of the PI3K signaling pathway.

Physiological and Aberrant γ-Globin Transcription During Development

The expression of the fetal Gγ- and Aγ-globin genes in normal development is confined to the fetal period, where two γ-globin chains assemble with two α-globin chains to form α₂γ₂ tetramers (HbF). HbF sustains oxygen delivery to tissues until birth, when β-globin replaces γ-globin, leading to the formation of α₂β₂ tetramers (HbA). However, in different benign and pathological conditions, HbF is expressed in adult cells, as it happens in the hereditary persistence of fetal hemoglobin, in anemias and in some leukemias. The molecular basis of γ-globin differential expression in the fetus and of its inappropriate activation in adult cells is largely unknown, although in recent years, a few transcription factors involved in this process have been identified. The recent discovery that fetal cells can persist to adulthood and contribute to disease raises the possibility that postnatal γ-globin expression could, in some cases, represent the signature of the fetal cellular origin.

CTCF As an Example of DNA-Binding Transcription Factors Containing Clusters of C2H2-Type Zinc Fingers

In mammals, most of the boundaries of topologically associating domains and all well-studied insulators are rich in binding sites for the CTCF protein. According to existing experimental data, CTCF is a key factor in the organization of the architecture of mammalian chromosomes. A characteristic feature of the CTCF is that the central part of the protein contains a cluster consisting of eleven domains of C2H2-type zinc fingers, five of which specifically bind to a long DNA sequence conserved in most animals. The class of transcription factors that carry a cluster of C2H2-type zinc fingers consisting of five or more domains (C2H2 proteins) is widely represented in all groups of animals. The functions of most C2H2 proteins still remain unknown. This review presents data on the structure and possible functions of these proteins, using the example of the vertebrate CTCF protein and several well- characterized C2H2 proteins in Drosophila and mammals.

Nucleus Accumbens-Associated Protein 1 Binds DNA Directly through the BEN Domain in a Sequence-Specific Manner

Nucleus accumbens-associated protein 1 (NAC1) is a nuclear protein that harbors an amino-terminal BTB domain and a carboxyl-terminal BEN domain. NAC1 appears to play significant and diverse functions in cancer and stem cell biology. Here we demonstrated that the BEN domain of NAC1 is a sequence-specific DNA-binding domain. We selected the palindromic 6 bp motif ACATGT as a target sequence by using a PCR-assisted random oligonucleotide selection approach. The interaction between NAC1 and target DNA was characterized by gel shift assays, pull-down assays, isothermal titration calorimetry (ITC), chromatin-immunoprecipitation assays, and NMR chemical shifts perturbation (CSP). The solution NMR structure revealed that the BEN domain of human NAC-1 is composed of five conserved α helices and two short β sheets, with an additional hitherto unknown N-terminal α helix. In particular, ITC clarified that there are two sequential events in the titration of the BEN domain of NAC1 into the target DNA. The ITC results were further supported by CSP data and structure analyses. Furthermore, live cell photobleaching analyses revealed that the BEN domain of NAC1 alone was unable to interact with chromatin/other proteins in cells.

ZBTB gene expression in HIV patients: a possible new molecular mechanism of viral control

HIV infects its target cell and integrates into its genome as an essential step in its replication cycle. Proviral DNA is also subjected to the same transcriptional regulation as the host cell genome by its own transcriptional factors, with activating or repressive activity. There is a clear interaction between the presence of transcriptional repressors and a decrease in the rate of HIV replication, promoting gene silencing in infected cells, which serve as viral reservoirs. This represents a major obstacle for HIV eradication. The ZBTB gene family comprises 49 genes that encode transcription factors that have a repressor function in differentiation and development of cells of the lymphopoietic lineage, including the main target cells of HIV, CD4⁺ T cells. In this cross-sectional study, we evaluated the expression profile of ZBTB genes in CD4⁺ T cells of HIV-positive individuals with different levels of infection control. We found upregulation of gene expression of ZBTB4 (p < 0.01), ZBTB7B (p < 0.001), and ZBTB38 (p < 0.05) and downregulation of ZBTB16 (p < 0.01) in HIV-positive patients compared to HIV-negative individuals. Interestingly, in a deeper analysis, we observed that elite controllers had the highest levels of expression of the ZBTB38, ZBTB2, HIC1, ZBTB7A, ZBTB7B (ThPOK) and ZBTB4 genes, showing 2.56- to 7.60-fold upregulation compare to the ART-naïve group. These results suggest a possible contribution of these ZBTB transcriptional repressors in HIV-positive patients and a possible new molecular mechanism of viral control.

LRF/ZBTB7A conservation accentuates its potential as a therapeutic target for the hematopoietic disorders

Conserved sequences across species have always provided valuable insights to improve our understanding on the human genome's entity and the interplay among different loci. Lymphoma/leukemia related factor (LRF) is encoded by ZBTB7A gene and belongs to an evolutionarily conserved family of transcription factors, implicated in vital cellular functions. The present data, demonstrating the wide-spread and the high overlap of the LRF/ZBTB7A recognition sites with genomic segments identified as CpG islands in the human genome, suggest that its binding capacity strongly depends on a specific sequence-encoded feature within CpGs. We have previously shown that de-methylation of the CpG island 326 lying in the ZBTB7A gene promoter is associated with impaired pharmacological induction of fetal hemoglobin in β-type hemoglobinopathies patients. Within this context we aimed to investigate the extent of the LRF/ZBTB7A conservation among primates and mouse genome, focusing our interest also on the CpG island flanking the gene's promoter region, in an effort to further establish its epigenetic regulatory role in human hematopoiesis and pharmacological involvement in hematopoietic disorders. Comparative analysis of the human ZBTB7A nucleotide and amino acid sequences and orthologous sequences among non-human primates and mouse, exhibited high conservation scores. Pathway analysis, clearly indicated that LRF/ZBTB7A influences conserved cellular processes. These data in conjunction with the high levels of expression foremost in hematopoietic tissues, highlighted LRF/ZBTB7A as an essential factor operating indisputably during hematopoiesis.

HBV DNA integrates into upregulated ZBTB20 in patients with hepatocellular carcinoma

Hepatitis B virus (HBV) affects the malignant phenotype of hepatocellular carcinoma (HCC). The aim of the present study was to investigate the integration sites of HBV DNA and the expression of the zinc finger protein, zinc finger and BTB domain containing 20 (ZBTB20) in patients with hepatocellular carcinoma. Integration of the HBV gene was detected using a high-throughput sequencing technique based on the HBV-Alu-PCR method. The expression of ZBTB20 was detected by western blotting. HBVX integration sites were detected in ~70% of the HCC tissue samples. HBV-integrated subgene X detection suggested that 67% of the integrated specimens were inserted into the host X gene in a forward direction, 57% in a reverse direction, 24% in both forward and reverse directions, and 38% had two HBV integration sites. A total of 3,320 HBV integration sites were identified, including 1,397 in HCC tissues, 1,205 in paracancerous tissues and 718 in normal liver tissues. HBV integration fragments displayed enrichment in the 200–800 bp region. Additionally, the results suggested that HBV was highly integrated into transmembrane phosphatase with tensin homology, long intergenic non-protein coding RNA (LINC)00618, LOC101929241, ACTR3 pseudogene 5, LINC00999, LOC101928775, deleted in oesophageal cancer 1, LINC00824, EBF transcription factor 2 and ZBTB20 in tumour tissues. Furthermore, the expression of ZBTB20 was upregulated in HCC tissues compared with normal control liver tissues, and was associated with HBV integration frequency. The present study suggested that HBV DNA integrated into upregulated ZBTB20 in patients with hepatocellular carcinoma, which might promote the occurrence and development of HCC. Furthermore, the results of the present study may provide a theoretical basis for the diagnosis and treatment of HCC.

The diagnostic challenges and clinical course of a myeloid/lymphoid neoplasm with eosinophilia and ZBTB20-JAK2 gene fusion presenting as B-lymphoblastic leukemia

We report the diagnostic challenges and the clinical course of a patient with an extraordinary presentation of B-lymphoblastic leukemia (B-ALL) with eosinophilia. We identified a novel ZBTB20-JAK2 gene fusion as a chimeric RNA transcript using the Archer platform. This gene fusion from the same patient was recently identified by Peterson et al. (2019) at the genomic level using a different sequencing technology platform. The configuration of this gene fusion predicts the production of a kinase-activating JAK2 fusion protein, which would normally lead to a diagnosis of Philadelphia chromosome–like B-ALL (Ph-like B-ALL). However, the unusual presentation of eosinophilia led us to demonstrate the presence of this gene fusion in nonlymphoid hematopoietic cells by fluorescence in situ hybridization (FISH) studies with morphologic correlation. Therefore, we believe this disease, in fact, represents blast crisis arising from an underlying myeloid neoplasm with JAK2 rearrangements. This case illustrates the difficulty in differentiating Ph-like B-ALL and myeloid/lymphoid neoplasm with eosinophilia and gene rearrangements (MLN-EGR) in blast crisis. As currently defined, the diagnosis of MLN-EGR relies on the hematologic presentations and the identification of marker gene fusions (including PCM1-JAK2, ETV6-JAK2, and BCR-JAK2). However, these same gene fusions, when limited to B-lymphoblasts, also define Ph-like B-ALL. Yet, our case does not conform to either condition. Therefore, the assessment for lineage restriction of gene rearrangements to reflect the pathophysiologic difference between B-ALL and MLN-EGR in blast crisis is likely a more robust diagnostic approach and allows the inclusion of MLN-EGR with novel gene fusions.

Structural basis of specific DNA binding by the transcription factor ZBTB24

ZBTB24, encoding a protein of the ZBTB family of transcriptional regulators, is one of four known genes—the other three being DNMT3B, CDCA7 and HELLS—that are mutated in immunodeficiency, centromeric instability and facial anomalies (ICF) syndrome, a genetic disorder characterized by DNA hypomethylation and antibody deficiency. The molecular mechanisms by which ZBTB24 regulates gene expression and the biological functions of ZBTB24 are poorly understood. Here, we identified a 12-bp consensus sequence [CT(G/T)CCAGGACCT] occupied by ZBTB24 in the mouse genome. The sequence is present at multiple loci, including the Cdca7 promoter region, and ZBTB24 binding is mostly associated with gene activation. Crystallography and DNA-binding data revealed that the last four of the eight zinc fingers (ZFs) (i.e. ZF5-8) in ZBTB24 confer specificity of DNA binding. Two ICF missense mutations have been identified in the ZBTB24 ZF domain, which alter zinc-binding cysteine residues. We demonstrated that the corresponding C382Y and C407G mutations in mouse ZBTB24 abolish specific DNA binding and fail to induce Cdca7 expression. Our analyses indicate and suggest a structural basis for the sequence specific recognition by a transcription factor centrally important for the pathogenesis of ICF syndrome.

The multi-faceted functioning portrait of LRF/ZBTB7A

Transcription factors (TFs) consisting of zinc fingers combined with BTB (for broad-complex, tram-track, and bric-a-brac) domain (ZBTB) are a highly conserved protein family that comprises a multifunctional and heterogeneous group of TFs, mainly modulating cell developmental events and cell fate. LRF/ZBTB7A, in particular, is reported to be implicated in a wide variety of physiological and cancer-related cell events. These physiological processes include regulation of erythrocyte maturation, B/T cell differentiation, adipogenesis, and thymic insulin expression affecting consequently insulin self-tolerance. In cancer, LRF/ZBTB7A has been reported to act either as oncogenic or as oncosuppressive factor by affecting specific cell processes (proliferation, apoptosis, invasion, migration, metastasis, etc) in opposed ways, depending on cancer type and molecular interactions. The molecular mechanisms via which LRF/ZBTB7A is known to exert either physiological or cancer-related cellular effects include chromatin organization and remodeling, regulation of the Notch signaling axis, cellular response to DNA damage stimulus, epigenetic-dependent regulation of transcription, regulation of the expression and activity of NF-κB and p53, and regulation of aerobic glycolysis and oxidative phosphorylation (Warburg effect). It is a pleiotropic TF, and thus, alterations to its expression status become detrimental for cell survival. This review summarizes its implication in different cellular activities and the commonly invoked molecular mechanisms triggered by LRF/ZBTB7A’s orchestrated action.

De novo ZBTB7A variant in a patient with macrocephaly, intellectual disability, and sleep apnea: implications for the phenotypic development in 19p13.3 microdeletions

Interstitial microdeletions at chromosome 19p13.3 are frequently associated with a constellation of clinical features including macrocephaly, characteristic face, intellectual disability, and sleep apnea. Previous studies in 25 patients with 19p13.3 microdeletions have revealed loss of MAP2K2 in 24 patients and that of PIAS4 and ZBTB7A in 23 patients, suggesting that these three adjacent genes are candidate genes for the phenotypic development in 19p13.3 microdeletions. We identified a de novo likely pathogenic heterozygous missense variant of ZBTB7A (NM_015898.3:c.1152C>G, p.(Cys384Trp)) in a Japanese boy with macrocephaly, intellectual disability, and sleep apnea. This variant affects the conserved cysteine residue forming the coordinate bond with Zn²⁺ ion at the first zinc finger domain, and is predicted to exert a dominant-negative effect because of the generation of homo- and hetero-dimers with the wild-type and variant ZBTB7A proteins. The results argue for a critical relevance of ZBTB7A to the development of most, but probably not all, of the 19p13.3 microdeletion phenotype.

Regulation of the positive transcriptional effect of PLZF through a non-canonical EZH2 activity

The transcription factor PLZF (promyelocytic leukemia zinc finger protein) acts as an epigenetic regulator balancing self-renewal and differentiation of hematopoietic cells through binding to various chromatin-modifying factors. First described as a transcriptional repressor, PLZF is also associated with active transcription, although the molecular bases underlying the differences are unknown. Here, we reveal that in a hematopoietic cell line, PLZF is predominantly associated with transcribed genes. Additionally, we identify a new association between PLZF and the histone methyltransferase, EZH2 at the genomic level. We find that co-occupancy of PLZF and EZH2 on chromatin at PLZF target genes is not associated with SUZ12 or trimethylated lysine 27 of histone H3 (H3K27me3) but with the active histone mark H3K4me3 and active transcription. Removal of EZH2 leads to an increase of PLZF binding and increased gene expression. Our results suggest a new role of EZH2 in restricting PLZF positive transcriptional activity independently of its canonical PRC2 activity.

ZBTB12 DNA methylation is associated with coagulation- and inflammation-related blood cell parameters: findings from the Moli-family cohort

Background

Zinc finger and BTB domain-containing protein 12 (ZBTB12) is a predicted transcription factor with potential role in hematopoietic development. Recent evidence linked low methylation level of ZBTB12 exon1 to myocardial infarction (MI) risk. However, the role of ZBTB12 in the pathogenesis of MI and cardiovascular disease in general is not yet clarified. We investigated the relation between ZBTB12 methylation and several blood parameters related to cardio-cerebrovascular risk in an Italian family-based cohort.

Results

ZBTB12 methylation was analyzed on white blood cells from the Moli-family cohort using the Sequenom EpiTYPER MassARRAY (Agena). A total of 13 CpG Sequenom units were analyzed in the small CpG island located in the only translated ZBTB12 exon. Principal component analysis (PCA) was performed to identify groups of CpG units with similar methylation estimates. Linear mixed effect regressions showed a positive association between methylation of ZBTB12 Factor 2 (including CpG units 8, 9–10, 16, 21) and TNF-ɑ stimulated procoagulant activity, a measure of procoagulant and inflammatory potential of blood cells. In addition, we also found a negative association between methylation of ZBTB12 Factor 1 (mainly characterized by CpG units 1, 3–4, 5, 11, and 26) and white blood cell and granulocyte counts. An in silico prediction analysis identified granulopoiesis- and hematopoiesis-specific transcription factors to potentially bind DNA sequences encompassing CpG1, CpG3–4, and CpG11.

Conclusions

ZBTB12 hypomethylation is linked to shorter TNF-ɑ stimulated whole blood coagulation time and increased WBC and granulocyte counts, further elucidating the possible link between ZBTB12 methylation and cardiovascular disease risk.

Electronic supplementary material

The online version of this article (10.1186/s13148-019-0665-6) contains supplementary material, which is available to authorized users.

Identification and Conservation Analysis of Cis-Regulatory Elements in Pig Liver

The liver plays a key role in metabolism and affects pig production. However, the functional annotation of noncoding regions of the pig liver remains poorly understood. We revealed the landscape of cis-regulatory elements and their functional characterization in pig liver. We identified 102,373 cis-regulatory elements in the pig liver, including enhancers, promoters, super-enhancers, and broad H3K4me3 domains, and highlighted 26 core transcription regulatory factors in the pig liver as well. We found similarity of cis-regulatory elements among those of pigs, humans, and cattle. Despite the low proportion of functionally conserved enhancers (~30%) between pig and human liver tissue, ~78% of the pig liver enhancer orthologues sequence could play an enhancer role in other human tissues. Additionally, we observed that the ratio of consistent super-enhancer-associated genes was significantly higher than the ratio of functionally conserved super-enhancers. Approximately 54% of the core regulation factors driven by super-enhancers were consistent across the liver from these three species. Our pig liver annotation and functional characterization studies provide a system and resource for noncoding annotation for future gene regulatory studies in pigs. Furthermore, our study also showed the high level functional conservation of cis-regulatory elements in mammals; it also improved our understanding of regulation function of mammal cis-regulatory elements.

Developmental regulation of regenerative potential in Drosophila by ecdysone through a bistable loop of ZBTB transcription factors

In many organisms, the regenerative capacity of tissues progressively decreases as development progresses. However, the developmental mechanisms that restrict regenerative potential remain unclear. In Drosophila, wing imaginal discs become unable to regenerate upon damage during the third larval stage (L3). Here, we show that production of ecdysone after larvae reach their critical weight (CW) terminates the window of regenerative potential by acting on a bistable loop composed of two antagonistic Broad-complex/Tramtrack/Bric-à-brac Zinc-finger (ZBTB) genes: chinmo and broad (br). Around mid L3, ecdysone signaling silences chinmo and activates br to switch wing epithelial progenitors from a default self-renewing to a differentiation-prone state. Before mid L3, Chinmo promotes a strong regenerative response upon tissue damage. After mid L3, Br installs a nonpermissive state that represses regeneration. Transient down-regulation of ecdysone signaling or Br in late L3 larvae enhances chinmo expression in damaged cells that regain the capacity to regenerate. This work unveils a mechanism that ties the self-renewing and regenerative potential of epithelial progenitors to developmental progression.

This study finds that the loss of regeneration potential in Drosophila wing imaginal discs is induced by the production of the steroid hormone ecdysone after the larva reaches its critical weight. Manipulating ecdysone signaling or the downstream transcription factors can uncouple regenerative properties from developmental progression.

While some organisms exhibit remarkable regenerative abilities throughout their life, many animals, including mammals, present limited regenerative potential that progressively decreases during development. Understanding the mechanisms underlying this progressive loss is important to devise therapeutic approaches aiming at facilitating the regeneration of a damaged tissue throughout life. The fruitfly Drosophila is a powerful model organism to address such questions. Indeed, while tissues, such as imaginal discs, can fully regenerate if damaged during early development, they fail to do so upon damages during late development. We show here that restriction of regenerative potential occurring during midlarval stages is due to the production of a steroid hormone, named ecdysone. By genetically manipulating ecdysone signaling, we can uncouple regenerative abilities from developmental progression. In particular, we show that ecdysone signaling triggers a switch in the sequential expression of two transcription factors, Chinmo and Broad, that positively and negatively regulate the competence for imaginal disc regeneration, respectively. Our work therefore identifies a key developmental signal that restricts regenerative potential in insects and opens new perspectives on elucidating how regeneration-permissive transcriptional programs are locked as development progresses.