Identification of BCL11B as a regulator of adipogenesis

DNA-binding affinity and specificity determine the phenotypic diversity in BCL11B-related disorders

BCL11B is a Cys2-His2 zinc-finger (C2H2-ZnF) domain-containing, DNA-binding, transcription factor with established roles in the development of various organs and tissues, primarily the immune and nervous systems. BCL11B germline variants have been associated with a variety of developmental syndromes. However, genotype-phenotype correlations along with pathophysiologic mechanisms of selected variants mostly remain elusive. To dissect these, we performed genotype-phenotype correlations of 92 affected individuals harboring a pathogenic or likely pathogenic BCL11B variant, followed by immune phenotyping, analysis of chromatin immunoprecipitation DNA-sequencing data, dual-luciferase reporter assays, and molecular modeling. These integrative analyses enabled us to define three clinical subtypes of BCL11B-related disorders. It is likely that gene-disruptive BCL11B variants and missense variants affecting zinc-binding cysteine and histidine residues cause mild to moderate neurodevelopmental delay with increased propensity for behavioral and dental anomalies, allergies and asthma, and reduced type 2 innate lymphoid cells. Missense variants within C2H2-ZnF DNA-contacting α helices cause highly variable clinical presentations ranging from multisystem anomalies with demise in the first years of life to late-onset, hyperkinetic movement disorder with poor fine motor skills. Those not in direct DNA contact cause a milder phenotype through reduced, target-specific transcriptional activity. However, missense variants affecting C2H2-ZnFs, DNA binding, and "specificity residues" impair BCL11B transcriptional activity in a target-specific, dominant-negative manner along with aberrant regulation of alternative DNA targets, resulting in more severe and unpredictable clinical outcomes. Taken together, we suggest that the phenotypic severity and variability is largely dependent on the DNA-binding affinity and specificity of altered BCL11B proteins.

Developmental regulation of dermal adipose tissue by BCL11b

The distinct anatomic environment in which adipose tissues arise during organogenesis is a principle determinant of their adult expansion capacity. Metabolic disease results from a deficiency in hyperplastic adipose expansion within the dermal/subcutaneous depot; thus, understanding the embryonic origins of dermal adipose is imperative. Using single-cell transcriptomics throughout murine embryogenesis, we characterized cell populations, including Bcl11b + cells, that regulate the development of dermal white adipose tissue (dWAT). We discovered that BCL11b expression modulates the Wnt signaling microenvironment to enable adipogenic differentiation in the dermal compartment. Subcutaneous and visceral adipose arises from a distinct population of Nefl + cells during embryonic organogenesis, whereas Pi16 + /Dpp4 + fibroadipogenic progenitors support obesity-stimulated hypertrophic expansion in the adult. Together, these results highlight the unique regulatory pathways used by anatomically distinct adipose depots, with important implications for human metabolic disease.

ARID1B maintains mesenchymal stem cell quiescence via inhibition of BCL11B-mediated non-canonical Activin signaling

ARID1B haploinsufficiency in humans causes Coffin-Siris syndrome, associated with developmental delay, facial dysmorphism, and intellectual disability. The role of ARID1B has been widely studied in neuronal development, but whether it also regulates stem cells remains unknown. Here, we employ scRNA-seq and scATAC-seq to dissect the regulatory functions and mechanisms of ARID1B within mesenchymal stem cells (MSCs) using the mouse incisor model. We reveal that loss of Arid1b in the GLI1+ MSC lineage disturbs MSCs' quiescence and leads to their proliferation due to the ectopic activation of non-canonical Activin signaling via p-ERK. Furthermore, loss of Arid1b upregulates Bcl11b, which encodes a BAF complex subunit that modulates non-canonical Activin signaling by directly regulating the expression of activin A subunit, Inhba. Reduction of Bcl11b or non-canonical Activin signaling restores the MSC population in Arid1b mutant mice. Notably, we have identified that ARID1B suppresses Bcl11b expression via specific binding to its third intron, unveiling the direct inter-regulatory interactions among BAF subunits in MSCs. Our results demonstrate the vital role of ARID1B as an epigenetic modifier in maintaining MSC homeostasis and reveal its intricate mechanistic regulatory network in vivo, providing novel insights into the linkage between chromatin remodeling and stem cell fate determination.

The role of zinc finger proteins in the fate determination of mesenchymal stem cells during osteogenic and adipogenic differentiation

Zinc finger proteins (ZFPs) constitute a crucial group of transcription factors widely present in various organisms. They act as transcription factors, nucleases, and RNA-binding proteins, playing significant roles in cell differentiation, growth, and development. With extensive research on ZFPs, their roles in the determination of mesenchymal stem cells (MSCs) fate during osteogenic and adipogenic differentiation processes have become increasingly clear. ZFP521, for instance, is identified as an inhibitor of the Wnt signaling pathway and RUNX2's transcriptional activity, effectively suppressing osteogenic differentiation. Moreover, ZFP217 contributes to the inhibition of adipogenic differentiation by reducing the M6A level of the cell cycle regulator cyclin D1 (CCND1). In addition, other ZFPs can also influence the fate of mesenchymal stem cells (MSCs) during osteogenic and adipogenic differentiation through various signaling pathways, transcription factors, and epigenetic controls, participating in the subsequent differentiation and maturation of precursor cells. Given the prevalent occurrence of osteoporosis, obesity, and related metabolic disorders, a comprehensive understanding of the regulatory mechanisms balancing bone and fat metabolism is essential, with a particular focus on the fate determination of MSCs in osteogenic and adipogenic differentiation. In this review, we provide a detailed summary of how zinc finger proteins influence the osteogenic and adipogenic differentiation of MSCs through different signaling pathways, transcription factors, and epigenetic mechanisms. Additionally, we outline the regulatory mechanisms of ZFPs in controlling osteogenic and adipogenic differentiation based on various stages of MSC differentiation.

BCL11B expression in hepatocellular carcinoma relates to chemosensitivity and clinical prognosis

INTRODUCTION

B-cell lymphoma/leukemia 11B (BCL11B) is a subunit of SWI/SNF chromatin remodeling complexes and functions in cell cycle regulation and apoptosis upon DNA replication stress and damages via transcription. Many malignancies were reported to exhibit changes in BCL11B gene expression; however, no study has focused on the relationship between BCL11B and hepatocellular carcinoma, which potentially exhibits DNA replication stress and damages upon its oncogenesis. Thus, in this study, we examined the molecular characterization of BCL11B expression in hepatocellular carcinoma.

METHODS AND RESULTS

The cumulative progression-free survival and overall survival were significantly longer in the clinical cases of BCL11B-negative hepatocellular carcinoma than BCL11B-positve cases. Microarray and real-time PCR analyses in hepatocellular carcinoma cell lines indicated a correlation between BCL11B and GATA6, a gene reported to be correlated with oncogenic activities and resistance to anthracycline, which is often used for hepatocellular carcinoma chemotherapy. Consequently, BCL11B-overexpressing cell lines exhibited resistance to anthracycline in cell growth assays and the resistance has been evidenced by the increased expression of BCL-xL in cell lines. The results were supported by the analyses of human HCC samples showing the correlation between BCL11B and GATA6 expressions.

DISCUSSIONS AND CONCLUSION

Our results indicated that overexpression of BCL11B amplifies GATA6 expression in hepatocellular carcinoma in vitro and in vivo that leads to anti-apoptotic signal activation, and induces resistance to chemotherapy, which influenced the postoperative prognosis.

Epigenetic Dynamics in the Function of T-Lineage Regulatory Factor Bcl11b

The transcription factor Bcl11b is critically required to support the development of diverse cell types, including T lymphocytes, type 2 innate lymphoid cells, neurons, craniofacial mesenchyme and keratinocytes. Although in T cell development its onset of expression is tightly linked to T-lymphoid lineage commitment, the Bcl11b protein in fact regulates substantially different sets of genes in different lymphocyte populations, playing strongly context-dependent roles. Somewhat unusually for lineage-defining transcription factors with site-specific DNA binding activity, much of the reported chromatin binding of Bcl11b appears to be indirect, or guided in large part by interactions with other transcription factors. We describe evidence suggesting that a further way in which Bcl11b exerts such distinct stage-dependent functions is by nucleating changes in regional suites of epigenetic modifications through recruitment of multiple families of chromatin-modifying enzyme complexes. Herein we explore what is - and what remains to be - understood of the roles of Bcl11b, its cofactors, and how it modifies the epigenetic state of the cell to enforce its diverse set of context-specific transcriptional and developmental programs.

Bcl11b/Ctip2 in Skin, Tooth, and Craniofacial System

Ctip2/Bcl11b is a zinc finger transcription factor with dual action (repression/activation) that couples epigenetic regulation to gene transcription during the development of various tissues. It is involved in a variety of physiological responses under healthy and pathological conditions. Its role and mechanisms of action are best characterized in the immune and nervous systems. Furthermore, its implication in the development and homeostasis of other various tissues has also been reported. In the present review, we describe its role in skin development, adipogenesis, tooth formation and cranial suture ossification. Experimental data from several studies demonstrate the involvement of Bcl11b in the control of the balance between cell proliferation and differentiation during organ formation and repair, and more specifically in the context of stem cell self-renewal and fate determination. The impact of mutations in the coding sequences of Bcl11b on the development of diseases such as craniosynostosis is also presented. Finally, we discuss genome-wide association studies that suggest a potential influence of single nucleotide polymorphisms found in the 3’ regulatory region of Bcl11b on the homeostasis of the cardiovascular system.

Master regulator genes and their impact on major diseases

Master regulator genes (MRGs) have become a hot topic in recent decades. They not only affect the development of tissue and organ systems but also play a role in other signal pathways by regulating additional MRGs. Because a MRG can regulate the concurrent expression of several genes, its mutation often leads to major diseases. Moreover, the occurrence of many tumors and cardiovascular and nervous system diseases are closely related to MRG changes. With the development in omics technology, an increasing amount of investigations will be directed toward MRGs because their regulation involves all aspects of an organism’s development. This review focuses on the definition and classification of MRGs as well as their influence on disease regulation.

Murine in vitro cellular models to better understand adipogenesis and its potential applications

Adipogenesis has been extensively studied using in vitro models of cellular differentiation, enabling long-term regulation of fat cell metabolism in human adipose tissue (AT) material. Many studies promote the idea that manipulation of this process could potentially reduce the prevalence of obesity and its related diseases. It has now become essential to understand the molecular basis of fat cell development to tackle this pandemic disease, by identifying therapeutic targets and new biomarkers. This review explores murine cell models and their applications for study of the adipogenic differentiation process in vitro. We focus on the benefits and limitations of different cell line models to aid in interpreting data and selecting a good cell line model for successful understanding of adipose biology.

A cellular perspective of adipogenesis transcriptional regulation

Adipose cells store lipids in the cytoplasm and signal systemically through secretion of adipokines and other molecules that regulate body energy metabolism. Differentiation of fat cells and its regulation has been the focus of extensive research since the early 1970s. In this review, we had attempted to examine the research bearing on the control of adipose cell differentiation, some of it dating back to the early days when Howard Green and his group described the preadipocyte cell lines 3T3-L1 and 3T3-F442A during 1974-1975. We also concentrated our attention on research published during the last few years, emphasizing data described on transcription factors that regulate adipose differentiation, outside of those that were reported earlier as part of the canonical adipogenic transcriptional cascade, which has been the subject of ample reviews by several groups of researchers. We focused on the studies carried out with the two preadipocyte cell culture models, the 3T3-L1 and 3T3-F442A cells that have provided essential data on adipose biology.

Functional characterization of common BCL11B gene desert variants suggests a lymphocyte-mediated association of BCL11B with aortic stiffness

The recent genome-wide analysis of carotid–femoral pulse wave velocity (PWV) identified a significant locus within the 14q32.2 gene desert. Gene regulatory elements for the transcriptional regulator B-cell CLL/lymphoma 11B (BCL11B) are within this locus and an attractive target for the gene association. We investigated the functional impact of these gene desert SNPs on BCL11B transcript in human aorta to characterize further its role in aortic stiffness. To do this, we used a large repository of aortic tissues (n = 185) from an organ transplant program and assessed ex vivo stiffness of the aortic rings. We tested association of three lead SNPs from the GWAS meta-analysis with ex vivo aortic stiffness and BCL11B aortic mRNA expression: rs1381289 and rs10782490 SNPs associated significantly with PWV and showed allele-specific differences in BCL11B mRNA. The risk alleles associated with lower BCL11B expression, suggesting a protective role for BCL11B. Despite strong association, we could not detect BCL11B protein in the human aorta. However, qPCR for CD markers showed that BCL11B transcript correlated strongly with markers for activated lymphocytes. Our data confirm the significance of the 14q32.2 region as a risk locus for aortic stiffness and an upstream regulator of BCL11B. The BCL11B transcript detected in the human aorta may reflect lymphocyte infiltration, suggesting that immune mechanisms contribute to the observed association of BCL11B with aortic stiffness.

LncRNA Gm15290 sponges miR-27b to promote PPARγ-induced fat deposition and contribute to body weight gain in mice

We found that Gm15290 was one of the most upregulated lncRNAs in the adipose of ob/ob mice through lncRNA microarray analysis. Then, manipulations of overexpression and silencing in mouse primary adipocytes showed that Gm15290 positively regulated adipogenesis, manifested by increasing lipid deposition and upregulating adipogenic genes including PPARγ, C/EBPα, and aP2. However, overexpression of mutant Gm15290 (at the binding site of miR-27c) did not have an promoting effect on adipogenesis. Additionally, Gm15290 was found to potentially interact with miR-27b that had been identified as a PPARγ targeting miRNA, and we verified their interaction by luciferase activity and RNA pull down assays. Furthermore, inhibition of Gm15290, by injection of the Gm15290 siRNA, decreased the body weight gain and mass of adipose tissues, including iWAT and eWAT, in mice fed with HFD. In conclusion, Gm15290 sponges miR-27b to increase fat deposition and body weight in HFD-fed mice.

The flavonoid derivative 4′-nitro-6-hydroxyflavone suppresses the activity of HNF4α and stimulates the degradation of HNF4α protein through the activation of AMPK

Hepatocyte nuclear factor 4α (HNF4α) is a nuclear receptor that regulates the expression of genes involved in a number of critical metabolic pathways. The modulation of HNF4α activity is thought to be a promising drug target pathway for hyperlipidemia. To identify compounds that reduce the activity of HNF4α, we conducted luciferase reporter assays using the promoter region of microsomal triglyceride transfer protein (MTP) gene, which contains an HNF4α-responsive element. Using this system, we show here that the flavonoid derivative 4′-nitro-6-hydroxyflavone (NOHF) suppresses MTP promoter activity. Treatment with NOHF caused a decrease in the expression of the HNF4α target gene. We also identified that NOHF triggers the AMP-activated protein kinase (AMPK) and accelerates the degradation of HNF4α protein. Knock-down of AMPK diminishes the effect of NOHF. These results indicate that NOHF is an AMPK activator and attenuates the transcriptional activity of HNF4α, at least in part, by accelerating HNF4α protein degradation.

The Emerging Role of Zfp217 in Adipogenesis

Zinc finger protein 217 (Zfp217), a member of the krüppel-type zinc finger protein family, plays diverse roles in cell differentiation and development of mammals. Despite extensive research on the functions of Zfp217 in cancer, pluripotency and reprogramming, its physiological roles in adipogenesis remain unknown. Our previous RNA sequencing data suggest the involvement of Zfp217 in adipogenesis. In this study, the potential function of Zfp217 in adipogenesis was investigated through bioinformatics analysis and a series of experiments. The expression of Zfp217 was found to be gradually upregulated during the adipogenic differentiation in C3H10T1/2 cells, which was consistent with that of the adipogenic marker gene Pparg2. Furthermore, there was a positive, significant relationship between Zfp217 expression and adipocyte differentiation. It was also observed that Zfp217 could not only trigger proliferative defect in C3H10T1/2 cells, but also interact with Ezh2 and suppress the downstream target genes of Ezh2. Besides, three microRNAs (miR-503-5p, miR-135a-5p and miR-19a-3p) which target Zfp217 were found to suppress the process of adipogenesis. This is the first report showing that Zfp217 has the capacity to regulate adipogenesis.

BCL11B gene heterozygosity causes weight loss accompanied by increased energy consumption, but not defective adipogenesis, in mice

BCL11B is a zinc finger-type transcription factor that regulates the development of the white adipose tissue (WAT), skin, central nervous system, and immune system. BCL11B is required for proper adipocyte differentiation, and BCL11B-/- embryos at E19.5 have very low amounts of the subcutaneous WAT. Here, we demonstrated that BCL11B+/- mice have lower body weight than BCL11B+/+ mice, whereas the expression of adipogenic marker genes in the WAT was comparable between BCL11B+/+ and BCL11B+/- mice. Histological analysis indicated that BCL11B+/- mice fed a high-fat diet have much smaller white adipocytes and lipid droplets in the WAT and liver, respectively. In addition, BCL11B+/- mice had increased energy consumption under both standard and high-fat diets. Thus, this study identifies BCL11B as a regulator of energy metabolism, and it is unlikely that BCL11B functions in the WAT contribute to energy metabolism in BCL11B+/- mice.

Bcl11b-A Critical Neurodevelopmental Transcription Factor-Roles in Health and Disease

B cell leukemia 11b (Bcl11b) is a zinc finger protein transcription factor with a multiplicity of functions. It works as both a genetic suppressor and activator, acting directly, attaching to promoter regions, as well as indirectly, attaching to promoter-bound transcription factors. Bcl11b is a fundamental transcription factor in fetal development, with important roles for the differentiation and development of various neuronal subtypes in the central nervous system (CNS). It has been used as a specific marker of layer V subcerebral projection neurons as well as striatal interneurons. Bcl11b also has critical developmental functions in the immune, integumentary and cardiac systems, to the extent that Bcl11b knockout mice are incompatible with extra-uterine life. Bcl11b has been implicated in a number of disease states including Huntington's disease, Alzheimer's disease, HIV and T-Cell malignancy, amongst others. Bcl11b is a fascinating protein whose critical roles in the CNS and other parts of the body are yet to be fully explicated. This review summarizes the current literature on Bcl11b and its functions in development, health, and disease as well as future directions for research.