Subtle Changes in the Levels of BCL-2 Proteins Cause Severe Craniofacial Abnormalities

Manipulating gene expression levels in mammalian cell factories: An outline of synthetic molecular toolboxes to achieve multiplexed control

Mammalian cells have developed dedicated molecular mechanisms to tightly control expression levels of their genes where the specific transcriptomic signature across all genes eventually determines the cell's phenotype. Modulating cellular phenotypes is of major interest to study their role in disease or to reprogram cells for the manufacturing of recombinant products, such as biopharmaceuticals. Cells of mammalian origin, for example Chinese hamster ovary (CHO) and Human embryonic kidney 293 (HEK293) cells, are most commonly employed to produce therapeutic proteins. Early genetic engineering approaches to alter their phenotype have often been attempted by "uncontrolled" overexpression or knock-down/-out of specific genetic factors. Many studies in the past years, however, highlight that rationally regulating and fine-tuning the strength of overexpression or knock-down to an optimum level, can adjust phenotypic traits with much more precision than such "uncontrolled" approaches. To this end, synthetic biology tools have been generated that enable (fine-)tunable and/or inducible control of gene expression. In this review, we discuss various molecular tools used in mammalian cell lines and group them by their mode of action: transcriptional, post-transcriptional, translational and post-translational regulation. We discuss the advantages and disadvantages of using these tools for each cell regulatory layer and with respect to cell line engineering approaches. This review highlights the plethora of synthetic toolboxes that could be employed, alone or in combination, to optimize cellular systems and eventually gain enhanced control over the cellular phenotype to equip mammalian cell factories with the tools required for efficient production of emerging, more difficult-to-express biologics formats.

Cell death

Cell death supports morphogenesis during development and homeostasis after birth by removing damaged or obsolete cells. It also curtails the spread of pathogens by eliminating infected cells. Cell death can be induced by the genetically programmed suicide mechanisms of apoptosis, necroptosis, and pyroptosis, or it can be a consequence of dysregulated metabolism, as in ferroptosis. Here, we review the signaling mechanisms underlying each cell-death pathway, discuss how impaired or excessive activation of the distinct cell-death processes can promote disease, and highlight existing and potential therapies for redressing imbalances in cell death in cancer and other diseases.

Genetic variants in BCL-2 family genes influence the risk of non-syndromic cleft lip with or without cleft palate

BACKGROUND

The BCL-2 family is crucial for cell death regulation and is involved in development, tissue homeostasis, and immunity. This study aimed to investigate the association between genetic variants in BCL-2 family genes and non-syndromic cleft lip with or without cleft palate (NSCL/P) risk.

METHODS

A two-stage case-control study was conducted in this association study. Gene-based analysis using Multi-marker Analysis of GenoMic Annotation was performed in the first stage cohort, which included 565 cases and 1269 controls. A logistic regression model was employed to assess the effect of single nucleotide polymorphisms (SNPs) on susceptibility to NSCL/P. Candidate SNPs were replicated by extra dbGaP case-parent trios. Haploreg, RegulomeDB, and UCSC Genome Browser were used to identify enhancer effects of promising SNPs. Bulk RNA sequencing data obtained from the Gene Expression Omnibus was used to identify co-expressed genes. Single-cell RNA sequencing dataset was used to infer the cell population of the candidate gene. The "Monocle" package was used to analyze the pseudotime cell trajectories.

RESULTS

Rs3943258 located in the enhancer region was associated with the risk of NSCL/P (Pmeta  = 5.66 × 10-04 ) and exhibited an eQTL effect for BCL2 (P = 3.96 × 10-02 ). Co-expression and pathway enrichment analysis revealed that genes related to Bcl2 were significantly enriched in the PI3K-Akt signaling pathway, MAPK signaling pathway, and Wnt signaling pathway. Five cell clusters were identified in single-cell RNA sequencing, and Bcl2 was mainly located in the mesenchyme.

CONCLUSION

The rs3943258 located within BCL2 was probably related to NSCL/P susceptibility.

Creation of distinctive Bax-lipid complexes at mitochondrial membrane surfaces drives pore formation to initiate apoptosis

Apotosis is an essential process tightly regulated by the Bcl-2 protein family where proapoptotic Bax triggers cell death by perforating the mitochondrial outer membrane. Although intensively studied, the molecular mechanism by which these proteins create apoptotic pores remains elusive. Here, we show that Bax creates pores by extracting lipids from outer mitochondrial membrane mimics by formation of Bax/lipid clusters that are deposited on the membrane surface. Time-resolved neutron reflectometry and Fourier transform infrared spectroscopy revealed two kinetically distinct phases in the pore formation process, both of which were critically dependent on cardiolipin levels. The initially fast adsorption of Bax on the mitochondrial membrane surface is followed by a slower formation of pores and Bax-lipid clusters on the membrane surface. Our findings provide a robust molecular understanding of mitochondrial membrane perforation by cell-killing Bax protein and illuminate the initial phases of programmed cellular death.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

Emerging mitochondrial-mediated mechanisms involved in oligodendrocyte development

Oligodendrocytes are the myelinating glia of the central nervous system and are generated after oligodendrocyte progenitor cells (OPCs) transition into pre-oligodendrocytes and then into myelinating oligodendrocytes. Myelin is essential for proper signal transmission within the nervous system and axonal metabolic support. Although the intrinsic and extrinsic factors that support the differentiation, survival, integration, and subsequent myelination of appropriate axons have been well investigated, little is known about how mitochondria-related pathways such as mitochondrial dynamics, bioenergetics, and apoptosis finely tune these developmental events. Previous findings suggest that changes to mitochondrial morphology act as an upstream regulatory mechanism of neural stem cell (NSC) fate decisions. Whether a similar mechanism is engaged during OPC differentiation has yet to be elucidated. Maintenance of mitochondrial dynamics is vital for regulating cellular bioenergetics, functional mitochondrial networks, and the ability of cells to distribute mitochondria to subcellular locations, such as the growing processes of oligodendrocytes. Myelination is an energy-consuming event, thus, understanding the interplay between mitochondrial dynamics, metabolism, and apoptosis will provide further insight into mechanisms that mediate oligodendrocyte development in healthy and disease states. Here we will provide a concise overview of oligodendrocyte development and discuss the potential contribution of mitochondrial mitochondrial-mediated mechanisms to oligodendrocyte bioenergetics and development.

Making the head: Caspases in life and death

The term apoptosis, as a way of programmed cell death, was coined a half century ago and since its discovery the process has been extensively investigated. The anatomy and physiology of the head are complex and thus apoptosis has mostly been followed in separate structures, tissues or cell types. This review aims to provide a comprehensive overview of recent knowledge concerning apoptosis-related molecules involved in the development of structures of head with a particular focus on caspases, cysteine proteases having a key position in apoptotic pathways. Since many classical apoptosis-related molecules, including caspases, are emerging in several non-apoptotic processes, these were also considered. The largest organ of the head region is the brain and its development has been extensively investigated, including the roles of apoptosis and related molecules. Neurogenesis research also includes sensory organs such as the eye and ear, efferent nervous system and associated muscles and glands. Caspases have been also associated with normal function of the skin and hair follicles. Regarding mineralised tissues within craniofacial morphogenesis, apoptosis in bones has been of interest along with palate fusion and tooth development. Finally, the role of apoptosis and caspases in angiogenesis, necessary for any tissue/organ development and maintenance/homeostasis, are discussed. Additionally, this review points to abnormalities of development resulting from improper expression/activation of apoptosis-related molecules.

BCL-2 protein family: attractive targets for cancer therapy

Acquired resistance to cell death is a hallmark of cancer. The BCL-2 protein family members play important roles in controlling apoptotic cell death. Abnormal over-expression of pro-survival BCL-2 family members or abnormal reduction of pro-apoptotic BCL-2 family proteins, both resulting in the inhibition of apoptosis, are frequently detected in diverse malignancies. The critical role of the pro-survival and pro-apoptotic BCL-2 family proteins in the regulation of apoptosis makes them attractive targets for the development of agents for the treatment of cancer. This review describes the roles of the various pro-survival and pro-apoptotic members of the BCL-2 protein family in normal development and organismal function and how defects in the control of apoptosis promote the development and therapy resistance of cancer. Finally, we discuss the development of inhibitors of pro-survival BCL-2 proteins, termed BH3-mimetic drugs, as novel agents for cancer therapy.

Loss of TAF8 causes TFIID dysfunction and p53-mediated apoptotic neuronal cell death

Mutations in genes encoding general transcription factors cause neurological disorders. Despite clinical prominence, the consequences of defects in the basal transcription machinery during brain development are unclear. We found that loss of the TATA-box binding protein-associated factor TAF8, a component of the general transcription factor TFIID, in the developing central nervous system affected the expression of many, but notably not all genes. Taf8 deletion caused apoptosis, unexpectedly restricted to forebrain regions. Nuclear levels of the transcription factor p53 were elevated in the absence of TAF8, as were the mRNAs of the pro-apoptotic p53 target genes Noxa, Puma and Bax. The cell death in Taf8 forebrain regions was completely rescued by additional loss of p53, but Taf8 and p53 brains failed to initiate a neuronal expression program. Taf8 deletion caused aberrant transcription of promoter regions and splicing anomalies. We propose that TAF8 supports the directionality of transcription and co-transcriptional splicing, and that failure of these processes causes p53-induced apoptosis of neuronal cells in the developing mouse embryo.

The manipulation of apoptosis for cancer therapy using BH3-mimetic drugs

Apoptosis is a form of programmed cell death that is regulated by the balance between prosurvival and proapoptotic BCL-2 protein family members. Evasion of apoptosis is a hallmark of cancer that arises when this balance is tipped in favour of survival. One form of anticancer therapeutic, termed 'BH3-mimetic drugs', has been developed to directly activate the apoptosis machinery in malignant cells. These drugs bind to and inhibit specific prosurvival BCL-2 family proteins, thereby mimicking their interaction with the BH3 domains of proapoptotic BCL-2 family proteins. The BCL-2-specific inhibitor venetoclax is approved by the US Food and Drug Administration and many regulatory authorities worldwide for the treatment of chronic lymphocytic leukaemia and acute myeloid leukaemia. BH3-mimetic drugs targeting other BCL-2 prosurvival proteins have been tested in preclinical models of cancer, and drugs targeting MCL-1 or BCL-X_L have advanced into phase I clinical trials for certain cancers. As with all therapeutics, efficacy and tolerability need to be carefully balanced to achieve a therapeutic window whereby there is significant anticancer activity with an acceptable safety profile. In this Review, we outline the current state of BH3-mimetic drugs targeting various prosurvival BCL-2 family proteins and discuss emerging data regarding primary and acquired resistance to these agents and approaches that may overcome this. We highlight issues that need to be addressed to further advance the clinical application of BH3-mimetic drugs, both alone and in combination with additional anticancer agents (for example, standard chemotherapeutic drugs or inhibitors of oncogenic kinases), for improved responses in patients with cancer.

Programmed Cell Death Not as Sledgehammer but as Chisel: Apoptosis in Normal and Abnormal Craniofacial Patterning and Development

Coordination of craniofacial development involves an complex, intricate, genetically controlled and tightly regulated spatiotemporal series of reciprocal inductive and responsive interactions among the embryonic cephalic epithelia (both endodermal and ectodermal) and the cephalic mesenchyme — particularly the cranial neural crest (CNC). The coordinated regulation of these interactions is critical both ontogenetically and evolutionarily, and the clinical importance and mechanistic sensitivity to perturbation of this developmental system is reflected by the fact that one-third of all human congenital malformations affect the head and face. Here, we focus on one element of this elaborate process, apoptotic cell death, and its role in normal and abnormal craniofacial development. We highlight four themes in the temporospatial elaboration of craniofacial apoptosis during development, namely its occurrence at (1) positions of epithelial-epithelial apposition, (2) within intra-epithelial morphogenesis, (3) during epithelial compartmentalization, and (4) with CNC metameric organization. Using the genetic perturbation of Satb2, Pbx1/2, Fgf8, and Foxg1 as exemplars, we examine the role of apoptosis in the elaboration of jaw modules, the evolution and elaboration of the lambdoidal junction, the developmental integration at the mandibular arch hinge, and the control of upper jaw identity, patterning and development. Lastly, we posit that apoptosis uniquely acts during craniofacial development to control patterning cues emanating from core organizing centres.

Molecular mechanisms of cell death in neurological diseases

Tightly orchestrated programmed cell death (PCD) signalling events occur during normal neuronal development in a spatially and temporally restricted manner to establish the neural architecture and shaping the CNS. Abnormalities in PCD signalling cascades, such as apoptosis, necroptosis, pyroptosis, ferroptosis, and cell death associated with autophagy as well as in unprogrammed necrosis can be observed in the pathogenesis of various neurological diseases. These cell deaths can be activated in response to various forms of cellular stress (exerted by intracellular or extracellular stimuli) and inflammatory processes. Aberrant activation of PCD pathways is a common feature in neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS), Alzheimer's disease, Parkinson's disease, and Huntington's disease, resulting in unwanted loss of neuronal cells and function. Conversely, inactivation of PCD is thought to contribute to the development of brain cancers and to impact their response to therapy. For many neurodegenerative diseases and brain cancers current treatment strategies have only modest effect, engendering the need for investigations into the origins of these diseases. With many diseases of the brain displaying aberrations in PCD pathways, it appears that agents that can either inhibit or induce PCD may be critical components of future therapeutic strategies. The development of such therapies will have to be guided by preclinical studies in animal models that faithfully mimic the human disease. In this review, we briefly describe PCD and unprogrammed cell death processes and the roles they play in contributing to neurodegenerative diseases or tumorigenesis in the brain. We also discuss the interplay between distinct cell death signalling cascades and disease pathogenesis and describe pharmacological agents targeting key players in the cell death signalling pathways that have progressed through to clinical trials.

Deciphering the complexity of sperm transcriptome reveals genes governing functional membrane and acrosome integrities potentially influence fertility

Deciphering sperm transcriptome is the key to understanding the molecular mechanisms governing peri-fertilization, embryonic development, and pregnancy establishment. This study aimed to profile sperm transcriptome to identify signature transcripts regulating male fertility. Semen samples were collected from 47 bulls with varied fertility rates. The sperm total RNA was isolated (n = 8) and subjected to transcriptome sequencing. Based on the expression pattern obtained from RNA profiling, the bulls were grouped (p = 0.03) into high-fertile and sub-fertile, and signature transcripts controlling sperm functions and fertility were identified. The results were validated using the OMIM database, qPCR, and sperm function tests. The sperm contains 1100 to 1700 intact transcripts, of which BCL2L11 and CAPZA3 were abundant and associated (p < 0.05) with spermatogenesis and post-embryonic organ morphogenesis. The upregulated genes in the acrosome integrity and functional membrane integrity groups had a close association with the fertility rate. The biological functions of these upregulated genes (p < 0.05) in the high-fertile bulls were associated with spermatogenesis (AFF4 and BRIP1), sperm motility (AK6 and ATP6V1G3), capacitation and zona binding (AGFG1), embryo development (TCF7 and AKIRIN2), and placental development (KRT19). The transcripts involved in pathways regulating embryonic development such as translation (EEF1B2 and MTIF3, p = 8.87E-05) and nonsense-mediated decay (RPL23 and RPL7A, p = 5.01E-27) were upregulated in high-fertile bulls. The identified transcripts may significantly impact oocyte function, embryogenesis, trophectoderm development, and pregnancy establishment. In addition, the study also reveals that the genes governing sperm functional membrane integrity and acrosome integrity have a prospective effect on male fertility.

It's time to die: BH3 mimetics in solid tumors

The removal of cells by apoptosis is an essential process regulating tissue homeostasis. Cancer cells acquire the ability to circumvent apoptosis and survive in an unphysiological tissue context. Thereby, the Bcl-2 protein family plays a key role in the initiation of apoptosis, and overexpression of the anti-apoptotic Bcl-2 proteins is one of the molecular mechanisms protecting cancer cells from apoptosis. Recently, small molecules targeting the anti-apoptotic Bcl-2 family proteins have been identified, and with venetoclax the first of these BH3 mimetics has been approved for the treatment of leukemia. In solid tumors the anti-apoptotic Bcl-2 family proteins Mcl-1 and Bcl-xL are frequently overexpressed or genetically amplified. In this review, we summarize the role of Mcl-1 and Bcl-xL in solid tumors and compare the different BH3 mimetics targeting Mcl-1 or Bcl-xL.

FGF signaling regulates development by processes beyond canonical pathways

In this study, Ray et al. investigated the signaling mechanisms by which FGFs function in development, using cranial neural crest cells and craniofacial development as a readout, and generated an allelic series of knock-in Fgfr1 and Fgfr2 mouse strains carrying point mutations that disrupt binding of signaling effectors, and a kinase-dead allele of Fgfr2 that broadly phenocopies the null mutant. They established combinatorial roles of Fgfr1 and Fgfr2 in development and uncoupled novel FGFR kinase-dependent cell adhesion properties from canonical intracellular signaling.

FGFs are key developmental regulators that engage a signal transduction cascade through receptor tyrosine kinases, prominently engaging ERK1/2 but also other pathways. However, it remains unknown whether all FGF activities depend on this canonical signal transduction cascade. To address this question, we generated allelic series of knock-in Fgfr1 and Fgfr2 mouse strains, carrying point mutations that disrupt binding of signaling effectors, and a kinase dead allele of Fgfr2 that broadly phenocopies the null mutant. When interrogated in cranial neural crest cells, we identified discrete functions for signaling pathways in specific craniofacial contexts, but point mutations, even when combined, failed to recapitulate the single or double null mutant phenotypes. Furthermore, the signaling mutations abrogated established FGF-induced signal transduction pathways, yet FGF functions such as cell–matrix and cell–cell adhesion remained unaffected, though these activities did require FGFR kinase activity. Our studies establish combinatorial roles of Fgfr1 and Fgfr2 in development and uncouple novel FGFR kinase-dependent cell adhesion properties from canonical intracellular signaling.

Systematic use of synthetic 5'-UTR RNA structures to tune protein translation improves yield and quality of complex proteins in mammalian cell factories

Predictably regulating protein expression levels to improve recombinant protein production has become an important tool, but is still rarely applied to engineer mammalian cells. We therefore sought to set-up an easy-to-implement toolbox to facilitate fast and reliable regulation of protein expression in mammalian cells by introducing defined RNA hairpins, termed 'regulation elements (RgE)', in the 5'-untranslated region (UTR) to impact translation efficiency. RgEs varying in thermodynamic stability, GC-content and position were added to the 5'-UTR of a fluorescent reporter gene. Predictable translation dosage over two orders of magnitude in mammalian cell lines of hamster and human origin was confirmed by flow cytometry. Tuning heavy chain expression of an IgG with the RgEs to various levels eventually resulted in up to 3.5-fold increased titers and fewer IgG aggregates and fragments in CHO cells. Co-expression of a therapeutic Arylsulfatase-A with RgE-tuned levels of the required helper factor SUMF1 demonstrated that the maximum specific sulfatase activity was already attained at lower SUMF1 expression levels, while specific production rates steadily decreased with increasing helper expression. In summary, we show that defined 5'-UTR RNA-structures represent a valid tool to systematically tune protein expression levels in mammalian cells and eventually help to optimize recombinant protein expression.

Neuronal cell life, death, and axonal degeneration as regulated by the BCL-2 family proteins

Axonal degeneration and neuronal cell death are fundamental processes in development and contribute to the pathology of neurological disease in adults. Both processes are regulated by BCL-2 family proteins which orchestrate the permeabilization of the mitochondrial outer membrane (MOM). MOM permeabilization (MOMP) results in the activation of pro-apoptotic molecules that commit neurons to either die or degenerate. With the success of small-molecule inhibitors targeting anti-apoptotic BCL-2 proteins for the treatment of lymphoma, we can now envision the use of inhibitors of apoptosis with exquisite selectivity for BCL-2 family protein regulation of neuronal apoptosis in the treatment of nervous system disease. Critical to this development is deciphering which subset of proteins is required for neuronal apoptosis and axon degeneration, and how these two different outcomes are separately regulated. Moreover, noncanonical BCL-2 family protein functions unrelated to the regulation of MOMP, including impacting necroptosis and other modes of cell death may reveal additional potential targets and/or confounders. This review highlights our current understanding of BCL-2 family mediated neuronal cell death and axon degeneration, while identifying future research questions to be resolved to enable regulating neuronal survival pharmacologically.

BioID-based proteomic analysis of the Bid interactome identifies novel proteins involved in cell-cycle-dependent apoptotic priming

Apoptotic priming controls the commitment of cells to apoptosis by determining how close they lie to mitochondrial permeabilisation. Variations in priming are important for how both healthy and cancer cells respond to chemotherapeutic agents, but how it is dynamically coordinated by Bcl-2 proteins remains unclear. The Bcl-2 family protein Bid is phosphorylated when cells enter mitosis, increasing apoptotic priming and sensitivity to antimitotic drugs. Here, we report an unbiased proximity biotinylation (BioID) screen to identify regulators of apoptotic priming in mitosis, using Bid as bait. The screen primarily identified proteins outside of the canonical Bid interactome. Specifically, we found that voltage-dependent anion-selective channel protein 2 (VDAC2) was required for Bid phosphorylation-dependent changes in apoptotic priming during mitosis. These results highlight the importance of the wider Bcl-2 family interactome in regulating the temporal control of apoptotic priming.

The third model of Bax/Bak activation: a Bcl-2 family feud finally resolved?

Bax and Bak, two functionally similar, pro-apoptotic proteins of the Bcl-2 family, are known as the gateway to apoptosis because of their requisite roles as effectors of mitochondrial outer membrane permeabilization (MOMP), a major step during mitochondria-dependent apoptosis. The mechanism of how cells turn Bax/Bak from inert molecules into fully active and lethal effectors had long been the focal point of a major debate centered around two competing, but not mutually exclusive, models: direct activation and indirect activation. After intensive research efforts for over two decades, it is now widely accepted that to initiate apoptosis, some of the BH3-only proteins, a subclass of the Bcl-2 family, directly engage Bax/Bak to trigger their conformational transformation and activation. However, a series of recent discoveries, using previously unavailable CRISPR-engineered cell systems, challenge the basic premise that undergirds the consensus and provide evidence for a novel and surprisingly simple model of Bax/Bak activation: the membrane (lipids)-mediated spontaneous model. This review will discuss the evidence, rationale, significance, and implications of this new model.

Factors influencing different types of malocclusion and arch form-A review

AIM

This review intends to highlight malocclusion as a multifactorial issue and review the different factors that influence different types of malocclusion and arch form.

METHODS

An online article search was performed on the factors influencing malocclusion and arch form from January 1990 through April 2020. The search was performed within the Google, Rutgers library, PubMed, MEDLINE databases via OVID using the keywords mentioned in the PubMed and MeSH headings for the English language published articles January 1990 through April 2020, which evaluated different factors that influence malocclusion and arch form.

RESULTS

Of the 300 articles found in initial search results, 31 articles met the inclusion criteria set for this review. These 31 studies were directly related to the factors that impact malocclusion and different arch forms.

CONCLUSION

Genetic inheritance, genetic mutations, age, gender, ethnicity, dental anomalies like macrodontia, congenital diseases, muscular diseases, hormone imbalance, and human behaviour are all factors that influence malocclusion and arch forms. The elements within the individual's control like behaviours can aid in preventing malocclusion. However, it seems as if the underlying reason for most of these factors indicates that malocclusion is a by-product of genetics and pathology.

Combined reduction in the expression of MCL-1 and BCL-2 reduces organismal size in mice

The intrinsic apoptotic pathway is controlled by the BCL-2 family of proteins, which exhibit either a pro-death or pro-survival function. Gene knockout studies revealed that different pro-survival BCL-2 proteins are critical for the survival of distinct cell types, although overlapping functions amongst such proteins have also been identified. In the process of studying mice lacking single alleles of Mcl-1 (Mcl-1^+/−), Bcl-2 (Bcl-2^+/−), or both in combination (Mcl-1^+/−Bcl-2^+/−), we observed that Mcl-1^+/−Bcl-2^+/− mice weighed less when compared with their wild-type littermates as they aged. Body composition analysis demonstrated that while fat mass was similar to wild-type controls, lean mass was significantly reduced in Mcl-1^+/−, Bcl-2^+/−, and, most strikingly in Mcl-1^+/−Bcl-2^+/− mice. The weights of several tissues including the heart, tibialis anterior, and kidney were likewise reduced in Mcl-1^+/−Bcl-2^+/− mice. When lean mass and specific tissue weights were expressed relative to body weight, these differences were no longer significant, indicating that that Mcl-1^+/−Bcl-2^+/− mice, and to a lesser extent Mcl-1^+/− and Bcl-2^+/− mice, are smaller than their wild-type counterparts. Consistently, the anal-naso length was reduced in Mcl-1^+/−Bcl-2^+/− mice. While minor reductions in size were observed in female Mcl-1^+/−Bcl-2^+/− mice, these effects were most prominent in males. Notably, Mcl-1^+/−Bcl-2^+/− males had markedly smaller testes even after accounting for differences in body weight. Collectively, these data reveal that combined loss of a single allele of Mcl-1 and Bcl-2, while not overtly impairing organismal development, leads to a reduction in animal size.

Toward Targeting Antiapoptotic MCL-1 for Cancer Therapy

Apoptosis is critical for embryonic development, tissue homeostasis, and the removal of infected or otherwise dangerous cells. It is controlled by three subgroups of the BCL-2 protein family—the BH3-only proteins that initiate cell death; the effectors of cell killing, BAX and BAK; and the antiapoptotic guardians, including MCL-1 and BCL-2. Defects in apoptosis can promote tumorigenesis and render malignant cells refractory to anticancer therapeutics. Activation of cell death by inhibiting antiapoptotic BCL-2 family members has emerged as an attractive strategy for cancer therapy, with the BCL-2 inhibitor venetoclax leading the way. Large-scale cancer genome analyses have revealed frequent amplification of the locus encoding antiapoptotic MCL-1 in human cancers, and functional studies have shown that MCL-1 is essential for the sustained survival and expansion of many types of tumor cells. Structural analysis and medicinal chemistry have led to the development of three distinct small-molecule inhibitors of MCL-1 that are currently undergoing clinical testing.

The essentials of developmental apoptosis

Apoptotic cells are commonly observed in a broad range of tissues during mammalian embryonic and fetal development. Specific requirements and functions of programmed cell death were inferred from early observations. These inferences did not hold up to functional proof for a requirement of apoptosis for normal tissue development in all cases. In this review, we summarize how the appraisal of the importance of developmental apoptosis has changed over the years, in particular with detailed functional assessment, such as by using gene-targeted mice lacking essential initiators or mediators of apoptosis. In recent years, the essentials of developmental apoptosis have emerged. We hypothesize that apoptosis is predominantly required to balance cell proliferation. The two interdependent processes—cell proliferation and apoptosis—together more powerfully regulate tissue growth than does each process alone. We proposed that this ensures that tissues and cell populations attain the appropriate size that allows fusion in the body midline and retain the size of cavities once formed. In addition, a limited number of tissues, albeit not all previously proposed, rely on apoptosis for remodeling, chiefly aortic arch remodeling, elimination of supernumerary neurons, removal of vaginal septa, and removal of interdigital webs in the formation of hands and feet.

Context-specific regulation of cell survival by a miRNA-controlled BIM rheostat

Knockout of the ubiquitously expressed miRNA-17∼92 cluster in mice produces a lethal developmental lung defect, skeletal abnormalities, and blocked B lymphopoiesis. A shared target of miR-17∼92 miRNAs is the pro-apoptotic protein BIM, central to life-death decisions in mammalian cells. To clarify the contribution of miR-17∼92:Bim interactions to the complex miR-17∼92 knockout phenotype, we used a system of conditional mutagenesis of the nine Bim 3' UTR miR-17∼92 seed matches. Blocking miR-17∼92:Bim interactions early in development phenocopied the lethal lung phenotype of miR-17∼92 ablation and generated a skeletal kinky tail. In the hematopoietic system, instead of causing the predicted B cell developmental block, it produced a selective inability of B cells to resist cellular stress; and prevented B and T cell hyperplasia caused by Bim haploinsufficiency. Thus, the interaction of miR-17∼92 with a single target is essential for life, and BIM regulation by miRNAs serves as a rheostat controlling cell survival in specific physiological contexts.

Emerging approaches to target mitochondrial apoptosis in cancer cells

Apoptosis is a highly conserved programme for removing damaged and unwanted cells. Apoptosis in most cells is coordinated on mitochondria by the Bcl-2 family of proteins. The balance between pro- and anti-apoptotic Bcl-2 family proteins sets a threshold for mitochondrial apoptosis, a balance that is altered during cancer progression. Consequently, avoidance of cell death is an established cancer hallmark. Although there is a general perception that tumour cells are more resistant to apoptosis than their normal counterparts, the realities of cell death regulation in cancer are more nuanced. In this review we discuss how a profound understanding of this control has led to new therapeutic approaches, including the new class of BH3-mimetics, which directly target apoptosis as a vulnerability in cancer. We discuss recent findings that highlight the current limitations in our understanding of apoptosis and how these novel therapeutics work.

Rhodiola crenulata attenuates apoptosis and mitochondrial energy metabolism disorder in rats with hypobaric hypoxia-induced brain injury by regulating the HIF-1α/microRNA 210/ISCU1/2(COX10) signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Rhodiola crenulata, a traditional Tibetan medicine, has shown promise in the treatment of hypobaric hypoxia (HH)-induced brain injury. However, the underlying mechanisms remain unclear. This study investigated the protective effects of R. crenulata aqueous extract (RCAE) on HH-induced brain injury in rats.

MATERIALS AND METHODS

An animal model of high-altitude hypoxic brain injury was established in SD rats using an animal decompression chamber for 24 h. Serum and hippocampus levels of superoxide dismutase (SOD), malondialdehyde (MDA), glutathione (GSH), oxidized glutathione (GSSG), and lactate dehydrogenase (LDH) were then determined using commercial biochemical kits. Neuron morphology and vitality were also evaluated using H&E and Nissl staining, and TUNEL staining was used to examine apoptosis. Gene and protein expression of HIF-1α, microRNA 210, ISCU1/2, COX10, Apaf-1, cleaved Caspase-3, Caspase-3, Bax, Bcl-2, and Cyto-c were determined by western blot, immunohistochemical and qRT-PCR analysis.

RESULTS

RCAE administration attenuated HH-induced brain injury as evidenced by decreased levels of MDA, LDH, and GSSG, increased GSH and SOD, improvements in hippocampus histopathological changes, increased cell vitality and ATP level, and reduced apoptotic cell numbers. RCAE treatment also enhanced HIF-1α, ISCU1/2, COX10, and Bcl-2 protein expression, while dramatically inhibiting expression of Apaf-1, Bax, Cyto-c, and cleaved Caspase-3. Treatment also increased gene levels of HIF-1α, microRNA 210, ISCU1/2, and COX10, and decreased Caspase-3 gene production.

CONCLUSIONS

RCAE attenuated HH-induced brain injury by regulating apoptosis and mitochondrial energy metabolism via the HIF-1α/microRNA 210/ISCU1/2 (COX10) signaling pathway.

MOZ directs the distal-less homeobox gene expression program during craniofacial development

Oral clefts are common birth defects. Individuals with oral clefts who have identical genetic mutations regularly present with variable penetrance and severity. Epigenetic or chromatin-mediated mechanisms are commonly invoked to explain variable penetrance. However, specific examples of these are rare. Two functional copies of the MOZ (KAT6A, MYST3) gene, encoding a MYST family lysine acetyltransferase chromatin regulator, are essential for human craniofacial development, but the molecular role of MOZ in this context is unclear. Using genetic interaction and genomic studies, we have investigated the effects of loss of MOZ on the gene expression program during mouse development. Among the more than 500 genes differentially expressed after loss of MOZ, 19 genes had previously been associated with cleft palates. These included four distal-less homeobox (DLX) transcription factor-encoding genes, Dlx1, Dlx2, Dlx3 and Dlx5 and DLX target genes (including Barx1, Gbx2, Osr2 and Sim2). MOZ occupied the Dlx5 locus and was required for normal levels of histone H3 lysine 9 acetylation. MOZ affected Dlx gene expression cell-autonomously within neural crest cells. Our study identifies a specific program by which the chromatin modifier MOZ regulates craniofacial development.

Long-Chain Non-Coding RNA (lncRNA) MT1JP Suppresses Biological Activities of Lung Cancer by Regulating miRNA-423-3p/Bim Axis

<strong>BACKGROUND</strong> This study aimed to explain the effects and mechanism of MT1JP in lung cancer development and treatment. <strong>MATERIAL AND METHODS</strong> Thirty non-small cell lung cancer (NSCLC) (stages I-II, 17 cases; stages III-IV, 13 cases) and adjacent normal tissues were obtained. MT1JP and miRNA-423-3p levels were assessed by <i>in situ</i> hybridization and Bim protein expression by immunohistochemistry, and the correlations determined were analyzed. Cell proliferation was determined using MTT and colony formation assay, and cell apoptosis was measured using flow cytometry. A549 cell invasion and migration were assessed by Transwell migration and scratch wound healing assays. Relative mRNA and protein expressions were assessed using real-time polymerase chain reaction and western blotting. Correlations between miRNA-423-3p and Bim protein were investigated using luciferase activity assay, and Bim protein expression was evaluated using western blotting. <strong>RESULTS</strong> MT1JP, miRNA-423-3p, and Bim expressions in NSCLC cancer tissues and those in adjacent cancer tissues were significantly different (<i>P</i><0.01 or <i>P</i><0.001) with increasing stage. Compared with those in the normal control (NC) group, cell proliferation rates were significantly suppressed (<i>P</i><0.01 or <i>P</i><0.001) and cell apoptosis rates significantly increased (<i>P</i><0.01 or <i>P</i><0.001) in the miRNA inhibitor and lncRNA+miRNA inhibitor groups. Invasion cell numbers and wound healing rates were also significantly inhibited in the miRNA inhibitor and lncRNA+miRNA inhibitor groups (<i>P</i><0.01 or <i>P</i><0.001) compared with those in the NC group. <strong>CONCLUSIONS</strong> The lncRNA MT1JP suppresses NSCLC biological activities by regulating the miRNA-423-3p/Bim axis.