Mitochondrial Deoxyribonucleic Acid (mtDNA), Maternal Inheritance, and Their Role in the Development of Cancers: A Scoping Review.

Mitochondrial DNA (mtDNA) is a small, circular, double-stranded DNA inherited from the mother during fertilization. Evolutionary evidence supported by the endosymbiotic theory identifies mitochondria as an organelle that could have descended from prokaryotes. This may be the reason for the independent function and inheritance pattern shown by mtDNA. The unstable nature of mtDNA due to the lack of protective histones, and effective repair systems make it more vulnerable to mutations. The mtDNA and its mutations could be maternally inherited thereby predisposing the offspring to various cancers like breast and ovarian cancers among others. Although mitochondria are considered heteroplasmic wherein variations among the multiple mtDNA genomes are noticed, mothers can have mitochondrial populations that are homoplasmic for a given mitochondrial mutation. Homoplasmic mitochondrial mutations may be transmitted to all maternal offspring. However, due to the complex interplay between the mitochondrial and nuclear genomes, it is often difficult to predict disease outcomes, even with homoplasmic mitochondrial populations. Heteroplasmic mtDNA mutations can be maternally inherited, but the proportion of mutated alleles differs markedly between offspring within one generation. This led to the genetic bottleneck hypothesis, explaining the rapid changes in allele frequency witnessed during the transmission of mtDNA from one generation to the next. Although a physical reduction in mtDNA has been demonstrated in several species, a comprehensive understanding of the molecular mechanisms is yet to be demonstrated. Despite initially thought to be limited to the germline, there is evidence that blockages exist in different cell types during development, perhaps explaining why different tissues in the same organism contain different levels of mutated mtDNA. In this review, we comprehensively discuss the potential mechanisms through which mtDNA undergoes mutations and the maternal mode of transmission that contributes to the development of tumors, especially breast and ovarian cancers.

A comprehensive diffusion-induced stress coupled multiscale modeling and analysis in hard-carbon electrodes of Li-ion batteries.

Particle fracture due to diffusion-induced stress (DIS) in electrodes is a key factor for lithium-ion battery (LIB) failure. Among many ways to minimize DIS, optimization of particle size and C-rates using state of charge (SOC) dependent varying properties can be a noble approach. Herein, a comprehensive multiscale modeling approach has been proposed to optimize the particle size by studying the DIS in hard carbon (HC) particles as the potential anode materials for high-energy LIBs. To accomplish this, density functional theory (DFT) was used to calculate the SOC dependent coefficient of volume expansion (CVE). Similarly, SOC dependent diffusivity and elastic modulus are calculated via molecular dynamics (MD) simulations. These results are transferred to a continuum model to examine the evolution of concentrations and DISs in hard carbon particles of radius 100-1000 nm lithiated at various C-rates (1C, 2C, 5C, and 10C). Our model successfully incorporates the variation of Li+ diffusivity and elastic modulus with SOC and tracks stress relaxation and volume expansion in the particles during lithiation. An optimized particle size has been recommended for hard carbon, considering both stresses for different C-rates. Our study provides a more realistic multiscale modeling framework for optimizing the DIS and can act as a guiding method towards achieving an optimum particle size so that capacity fading due to cracking can be avoided.

T-box3 is a ciliary protein and regulates stability of the Gli3 transcription factor to control digit number.

Crucial roles for T-box3 in development are evident by severe limb malformations and other birth defects caused by T-box3 mutations in humans. Mechanisms whereby T-box3 regulates limb development are poorly understood. We discovered requirements for T-box at multiple stages of mouse limb development and distinct molecular functions in different tissue compartments. Early loss of T-box3 disrupts limb initiation, causing limb defects that phenocopy Sonic Hedgehog (Shh) mutants. Later ablation of T-box3 in posterior limb mesenchyme causes digit loss. In contrast, loss of anterior T-box3 results in preaxial polydactyly, as seen with dysfunction of primary cilia or Gli3-repressor. Remarkably, T-box3 is present in primary cilia where it colocalizes with Gli3. T-box3 interacts with Kif7 and is required for normal stoichiometry and function of a Kif7/Sufu complex that regulates Gli3 stability and processing. Thus, T-box3 controls digit number upstream of Shh-dependent (posterior mesenchyme) and Shh-independent, cilium-based (anterior mesenchyme) Hedgehog pathway function.

Molecular Mechanisms for the Modulation of Selected Inflammatory Markers by Dietary Rice Bran Oil in Rats Fed Partially Hydrogenated Vegetable Fat.

Industrially produced partially hydrogenated vegetable fat (PHVF) contains trans fatty acids (TFA) mostly comprising elaidic acid (EA, 18:1∆9t). Though, the harmful effects of TFA on health have been repeatedly publicized, the fat containing TFA have been continued to be used as a cooking medium in many regions of the world. The adverse effects of PHVF on oxidative stress and inflammatory markers and the possible ameliorative action of rice bran oil (RBO) on these markers were evaluated. Weaning rats were fed a AIN-93 purified diet supplemented with the following lipids: groundnut oil (GNO, 10 wt%), PHVF (10 wt%), RBO (10 wt%), PHVF blended with RBO at 2.5, 5.0 and 7.5 wt% levels. The final concentration of the lipids in the diet was maintained at 10 wt%. Rats were fed these diets for 60 days. They were sacrificed and analyzed for oxidative stress and inflammatory markers. The rats fed PHVF showed lower levels of lipid peroxidation and hepatic antioxidant enzymes. The rats fed PHVF-containing diets showed enhanced levels of interleukin-1ß, C-reactive proteins and also showed enhanced levels of paw inflammation when injected with carrageenan as compared to rats given GNO, RBO or PHVF blended with incremental amounts of RBO. The macrophages from rats fed diet containing PHVF showed up-regulation in the expressions of cytosolic phospholipase A2 (cPLA2), nuclear factor-κB p65, toll like receptor (TLR)-2, TLR-4 and down-regulation in the expressions of peroxisome proliferator activated receptor gamma (PPAR)γ, adiponectin receptor (AdipoR)-1 and AdipoR-2 when compared to rats fed diet containing GNO, RBO and PHVF blended with RBO. It was concluded that dietary PHVF enhance pro-inflammatory markers which can be reduced by judiciously blending PHVF with RBO.

A Dynamic Role of TBX3 in the Pluripotency Circuitry.

Pluripotency represents a cell state comprising a fine-tuned pattern of transcription factor activity required for embryonic stem cell (ESC) self-renewal. TBX3 is the earliest expressed member of the T-box transcription factor family and is involved in maintenance and induction of pluripotency. Hence, TBX3 is believed to be a key member of the pluripotency circuitry, with loss of TBX3 coinciding with loss of pluripotency. We report a dynamic expression of TBX3 in vitro and in vivo using genetic reporter tools tracking TBX3 expression in mouse ESCs (mESCs). Low TBX3 levels are associated with reduced pluripotency, resembling the more mature epiblast. Notably, TBX3-low cells maintain the intrinsic capability to switch to a TBX3-high state and vice versa. Additionally, we show TBX3 to be dispensable for induction and maintenance of naive pluripotency as well as for germ cell development. These data highlight novel facets of TBX3 action in mESCs.

Development, validation of liquid chromatography-tandem mass spectrometry method for simultaneous determination of rosuvastatin and metformin in human plasma and its application to a pharmacokinetic study.

A new, simple and accurate liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for simultaneous determination of rosuvastatin (ROS) and metformin (MET) in human plasma was developed. The assay procedure involved simple protein precipitation with acetonitrile. Following precipitation, fraction of supernatant was decanted and evaporated under gentle stream of nitrogen at 40°C. The residue was reconstituted in mobile phase and injected. The chromatographic separation was achieved with Thermo Hypurity C18 column (50 mm × 4.6 mm, 5 µ) using a mobile phase composition containing 0.1% v/v formic acid in water and acetonitrile (30:70, v/v) at a flow rate of 0.4 mL/min. The total run time was 3.5 min. The method showed good linearity in the range 0.5-200 ng/mL for ROS and 2-2000 ng/mL for MET with correlation coefficient (r) >0.9994 for both the analytes. The intra and inter-day precision values for ROS and MET met the acceptance criteria as per regulatory guidelines. The battery of stability studies viz., bench-top, freeze-thaw and long term stability were performed. The developed method was applied to a pharmacokinetic study.

Coordinated control of senescence by lncRNA and a novel T-box3 co-repressor complex.

Cellular senescence is a crucial tumor suppressor mechanism. We discovered a CAPERα/TBX3 repressor complex required to prevent senescence in primary cells and mouse embryos. Critical, previously unknown roles for CAPERα in controlling cell proliferation are manifest in an obligatory interaction with TBX3 to regulate chromatin structure and repress transcription of CDKN2A-p16INK and the RB pathway. The IncRNA UCA1 is a direct target of CAPERα/TBX3 repression whose overexpression is sufficient to induce senescence. In proliferating cells, we found that hnRNPA1 binds and destabilizes CDKN2A-p16INK mRNA whereas during senescence, UCA1 sequesters hnRNPA1 and thus stabilizes CDKN2A-p16INK. Thus CAPERα/TBX3 and UCA1 constitute a coordinated, reinforcing mechanism to regulate both CDKN2A-p16INK transcription and mRNA stability. Dissociation of the CAPERα/TBX3 co-repressor during oncogenic stress activates UCA1, revealing a novel mechanism for oncogene-induced senescence. Our elucidation of CAPERα and UCA1 functions in vivo provides new insights into senescence induction, and the oncogenic and developmental properties of TBX3.

TBX3 regulates splicing in vivo: a novel molecular mechanism for Ulnar-mammary syndrome.

TBX3 is a member of the T-box family of transcription factors with critical roles in development, oncogenesis, cell fate, and tissue homeostasis. TBX3 mutations in humans cause complex congenital malformations and Ulnar-mammary syndrome. Previous investigations into TBX3 function focused on its activity as a transcriptional repressor. We used an unbiased proteomic approach to identify TBX3 interacting proteins in vivo and discovered that TBX3 interacts with multiple mRNA splicing factors and RNA metabolic proteins. We discovered that TBX3 regulates alternative splicing in vivo and can promote or inhibit splicing depending on context and transcript. TBX3 associates with alternatively spliced mRNAs and binds RNA directly. TBX3 binds RNAs containing TBX binding motifs, and these motifs are required for regulation of splicing. Our study reveals that TBX3 mutations seen in humans with UMS disrupt its splicing regulatory function. The pleiotropic effects of TBX3 mutations in humans and mice likely result from disrupting at least two molecular functions of this protein: transcriptional regulation and pre-mRNA splicing.

N-terminal PDZ-like domain of chromatin organizer SATB1 contributes towards its function as transcription regulator.

The special AT-rich DNA-binding protein 1 (SATB1) is a matrix attachment region (MAR)-binding protein that acts as a global repressor via recruitment of CtBP1:HDAC1-containing co-repressors to its binding targets. The N-terminal PSD95/Dlg-A/ZO-1 (PDZ)-like domain of SATB1 mediates interactions with several chromatin proteins. In the present study, we set out to address whether the PDZ-domain-mediated interactions of SATB1 are critical for its in vivo function as a global repressor. We reasoned that since the N-terminal PDZ-like domain (amino acid residues 1-204) lacks DNA binding activity, it would fail to recruit the interacting partners of SATB1 to its genomic binding sites and hence would not repress the SATB1-regulated genes. Indeed, in vivo MAR-linked luciferase reporter assay revealed that overexpression of the PDZ-like domain resulted in de-repression, indicating that the PDZ-like domain exerts a dominant negative effect on genes regulated by SATB1. Next, we developed a stable dominant negative model in human embryonic kidney (HEK) 293T cells that conditionally expressed the N-terminal 1-204 region harbouring the PDZ-like domain of SATB1. To monitor the effect of sequestration of the interaction partners on the global gene regulation by SATB1, transcripts from the induced and uninduced clones were subjected to gene expression profiling. Clustering of expression data revealed that 600 out of 19000 genes analysed were significantly upregulated upon overexpression of the PDZ-like domain. Induced genes were found to be involved in important signalling cascades and cellular functions. These studies clearly demonstrated the role of PDZ domain of SATB1 in global gene regulation presumably through its interaction with other cellular proteins.

Phosphorylation-dependent regulation of SATB1, the higher-order chromatin organizer and global gene regulator.

The chromatin organizer SATB1 regulates distant genes by selectively tethering matrix attachment regions (MARs) to the nuclear matrix. Post-translational modifications (PTMs) are important regulators of functional activities of proteins. Recently, a phosphorylation-dependent molecular switch that provided insights into the molecular mechanism of transcriptional repression and activation by SATB1 was discovered. SATB1 is specifically phosphorylated by protein kinase C (PKC) at serine 185 in vivo, and this modification leads to repression of transcription by SATB1 via increased association with the histone deacetylase 1 (HDAC1) corepressor. In this chapter, we describe methods for overexpression and purification of full length SATB1 protein and for its in vitro phosphorylation. We also describe method for in vivo phosphorylation of SATB1 upon immunoprecipitation using anti-SATB1. Finally, we describe a functional assay to monitor the effect of phosphorylation on transcription activity of SATB1 in vivo using MAR-linked reporter assay, in the presence and absence of PKC inhibitors.

Acetylation-dependent interaction of SATB1 and CtBP1 mediates transcriptional repression by SATB1.

Special AT-rich binding protein 1 (SATB1) acts as a global regulator of gene expression by recruiting various corepressor or coactivator complexes, thereby establishing a unique chromatin structure at its genomic targets in a context-dependent manner. Although SATB1 acts predominantly as a repressor via recruitment of histone deacetylase 1 (HDAC1) complexes, the precise mechanism of global repression is not clear. Here we report that SATB1 and C-terminal binding protein 1 (CtBP1) form a repressor complex in vivo. The interaction occurs via the CtBP1 interaction consensus motif PVPLS within the PDZ-like domain of SATB1. The acetylation of SATB1 upon LiCl and ionomycin treatments disrupts its association with CtBP1, resulting in enhanced target gene expression. Chromatin immunoprecipitation analysis indicated that the occupancy of CtBP1 and HDAC1 is gradually decreased and the occupancy of PCAF is elevated at the SATB1 binding sites within the human interleukin-2 and mouse c-Myc promoters. Moreover, gene expression profiling studies using cells in which expression of SATB1 and CtBP1 was silenced indicated commonly targeted genes that may be coordinately repressed by the SATB1-CtBP1 complex. Collectively, these results provide a mechanistic insight into the role of SATB1-CtBP1 interaction in the repression and derepression of SATB1 target genes during Wnt signaling in T cells.

PDZ domain-mediated dimerization and homeodomain-directed specificity are required for high-affinity DNA binding by SATB1.

To better understand DNA recognition and transcription activity by SATB1, the T-lineage-enriched chromatin organizer and transcription factor, we have determined its optimal DNA-binding sequence by random oligonucleotide selection. The consensus SATB1-binding sequence (CSBS) comprises a palindromic sequence in which two identical AT-rich half-sites are arranged as inverted repeats flanking a central cytosine or guanine. Strikingly, the CSBS half-site is identical to the conserved element 'TAATA' bound by the known homeodomains (HDs). Furthermore, we show that the high-affinity binding of SATB1 to DNA is dimerization-dependent and the HD also binds in similar fashion. Binding studies using HD-lacking SATB1 and binding target with increased spacer between the two half-sites led us to propose a model for SATB1-DNA complex in which the HDs bind in an antiparallel fashion to the palindromic consensus element via minor groove, bridged by the PDZ-like dimerization domain. CSBS-driven in vivo reporter analysis indicated that SATB1 acts as a repressor upon binding to the CSBS and most of its derivatives and the extent of repression is proportional to SATB1's binding affinity to these sequences. These studies provide mechanistic insights into the mode of DNA binding and its effect on the regulation of transcription by SATB1.

The third dimension of gene regulation: organization of dynamic chromatin loopscape by SATB1.

Compartmentalized distribution of functional components is a hallmark of the eukaryotic nucleus. Technological advances in recent years have provided unprecedented insights into the role of chromatin organization and interactions of various structural-functional components toward gene regulation. SATB1, the global chromatin organizer and transcription factor, has emerged as a key factor integrating higher-order chromatin architecture with gene regulation. Studies in recent years have unraveled the role of SATB1 in organization of chromatin 'loopscape' and its dynamic nature in response to physiological stimuli. SATB1 organizes the MHC class-I locus into distinct chromatin loops by tethering MARs to nuclear matrix at fixed distances. Silencing of SATB1 mimics the effects of IFNgamma treatment on chromatin loop architecture of the MHC class-I locus and altered expression of genes within the locus. At genome-wide level, SATB1 seems to play a role in organization of the transcriptionally poised chromatin.

Displacement of SATB1-bound histone deacetylase 1 corepressor by the human immunodeficiency virus type 1 transactivator induces expression of interleukin-2 and its receptor in T cells.

One hallmark of human immunodeficiency virus type 1 (HIV-1) infection is the dysregulation of cytokine gene expression in T cells. Transfection of T cells with human T-cell leukemia type 1 or 2 transactivator results in the induction of the T-cell-restricted cytokine interleukin-2 (IL-2) and its receptor (IL-2Ralpha). However, no T-cell-specific factor(s) has been directly linked with the regulation of IL-2 and IL-2Ralpha transcription by influencing the promoter activity. Thymocytes from SATB1 (special AT-rich sequence binding protein 1) knockout mice have been shown to ectopically express IL-2Ralpha, suggesting involvement of SATB1 in its negative regulation. Here we show that SATB1, a T-cell-specific global gene regulator, binds to the promoters of human IL-2 and IL-2Ralpha and recruits histone deacetylase 1 (HDAC1) in vivo. SATB1 also interacts with Tat in HIV-1-infected T cells. The functional interaction between HIV-1 Tat and SATB1 requires its PDZ-like domain, and the binding of the HDAC1 corepressor occurs through the same. Furthermore, Tat competitively displaces HDAC1 that is bound to SATB1, leading to increased acetylation of the promoters in vivo. Transduction with SATB1 interaction-deficient soluble Tat (Tat 40-72) and reporter assays using a transactivation-negative mutant (C22G) of Tat unequivocally demonstrated that the displacement of HDAC1 itself is sufficient for derepression of these promoters in vivo. These results suggest a novel mechanism by which HIV-1 Tat might overcome SATB1-mediated repression in T cells.