Programmed spontaneously beating cardiomyocytes in regenerative cardiology.

Stem cells have gained attention as a promising therapeutic approach for damaged myocardium, and there have been efforts to develop a protocol for regenerating cardiomyocytes (CMs). Certain cells have showed a greater aptitude for yielding beating CMs, such as induced pluripotent stem cells, embryonic stem cells, adipose-derived stromal vascular fraction cells and extended pluripotent stem cells. The approach for generating CMs from stem cells differs across studies, although there is evidence that Wnt signaling, chemical additives, electrical stimulation, co-culture, biomaterials and transcription factors triggers CM differentiation. Upregulation of Gata4, Mef2c and Tbx5 transcription factors has been correlated with successfully induced CMs, although Mef2c may potentially play a more prominent role in the generation of the beating phenotype, specifically. Regenerative research provides a possible candidate for cardiac repair; however, it is important to identify factors that influence their differentiation. Altogether, the spontaneously beating CMs would be monumental for regenerative research for cardiac repair.

Artificial intelligence in therapeutic management of hyperlipidemic ocular pathology.

Hyperlipidemia has many ocular manifestations, the most prevalent being retinal vascular occlusion. Hyperlipidemic lesions and occlusions to the vessels supplying the retina result in permanent blindness, necessitating prompt detection and treatment. Retinal vascular occlusion is diagnosed using different imaging modalities, including optical coherence tomography angiography. These diagnostic techniques obtain images representing the blood flow through the retinal vessels, providing an opportunity for AI to utilize image recognition to detect blockages and abnormalities before patients present with symptoms. AI is already being used as a non-invasive method to detect retinal vascular occlusions and other vascular pathology, as well as predict treatment outcomes. As providers see an increase in patients presenting with new retinal vascular occlusions, the use of AI to detect and treat these conditions has the potential to improve patient outcomes and reduce the financial burden on the healthcare system. This article comprehends the implications of AI in the current management strategies of retinal vascular occlusion (RVO) in hyperlipidemia and the recent developments of AI technology in the management of ocular diseases.

Evolution of the genetic code; Evidence from serine codon use disparity in Escherichia coli.

Among the 20 amino acids, three of them-leucine (Leu), arginine (Arg), and serine (Ser)-are encoded by six different codons. In comparison, all of the other 17 amino acids are encoded by either 4, 3, 2, or 1 codon. Peculiarly, Ser is separated into two disparate Ser codon boxes, differing by at least two-base substitutions, in contrast to Leu and Arg, of which codons are mutually exchangeable by a single-base substitution. We propose that these two different Ser codons independently emerged during evolution. In this hypothesis, at the time of the origin of life there were only seven primordial amino acids: Valine (coded by GUX [X = U, C, A or G]), alanine (coded by GCX), aspartic acid (coded by GAY [Y = U or C]), glutamic acid (coded by GAZ [Z = A or G]), glycine (coded by GGX), Ser (coded by AGY), and Arg (coded by CGX and AGZ). All of these were derived from GGX for glycine by single-base substitutions. Later in evolution, another class of Ser codons, UCX, were derived from alanine codons, GCX, distinctly different from the other primordial Ser codon, AGY. From the analysis of the Escherichia coli genome, we find extensive disparities in the usage of these two Ser codons, as some genes use only AGY for Ser in their genes. In contrast, others use only UCX, pointing to distinct differences in their origins, consistent with our hypothesis.

Novel Approaches to Program Cells to Differentiate into Cardiomyocytes in Myocardial Regeneration.

With heart failure (HF) being one of the leading causes of hospitalization and death worldwide, multiple stem cell therapies have been attempted to accelerate the regeneration of the infarct zone. Versatile strategies have emerged to establish the cell candidates of cardiomyocyte lineage for regenerative cardiology. This article illustrates critical insights into the emerging technologies, current approaches, and translational promises on the programming of diverse cell types for cardiac regeneration.

A CUGGU/UUGGU-specific MazF homologue from Methanohalobium evestigatum.

MazF is a sequence-specific endoribonuclease or mRNA interferase, which cleaves RNA at a specific sequence. Since the expression of a specific gene or a group of specific genes can be regulated by MazF, expanding the repertoire of recognition sequences by MazF mRNA interferases is highly desirable for biotechnological and medical applications. Here, we identified a gene for a MazF homologue (MazFme) from Methanohalobium evestigatum, an extremely halophilic archaeon. In order to suppress the toxicity of MazFme to the E. coli cells, the C-terminal half of the cognate antitoxin MazEme was fused to the N-terminal end of MazFme. Since the fusion of the C-terminal half of MazEme to MazFme was able to neutralize MazFme toxicity, the MazEme-MazFme fusion protein was expressed in a large amount without any toxic effects. After purification of the MazEme, the free MazFme RNA cleavage specificity was determined by primer extension and synthetic ribonucleotides, revealing that MazFme is a CUGGU/UUGGU-specific endoribonuclease.

The role of the loop 1 region in MazFbs mRNA interferase from Bacillus subtilis in recognition of the 3' end of the RNA substrate.

MazFbs is an mRNA interferase from Bacillus subtilis specifically recognizing UACAU. The X-ray structure of its complex with an RNA substrate has been also solved. When its amino acid sequence is compared with that of MazFhw, an mRNA interferase from a highly halophilic archaeon, recognizing UUACUCA, the 9-residue loop-1 region is highly homologous except that the V16V17 sequence in MazFbs is replaced with TK in MazFhw. Thus, we examined the role of the VV sequence in RNA substrate recognition by replacing it with TK, GG, AA or LL. The substitution mutants thus constructed showed significant differences in cleavage specificity using MS2 phage RNA. The primer extension analysis of the cleavage sites revealed that the VV sequence plays an important role in the recognition of the 3'-end base of the RNA substrate.

Designing of a single gene encoding four functional proteins.

In the genomes of some organisms such as bacteriophages and bacteria, a DNA sequence is able to encode two different proteins, indicating that genetic information is compacted in DNA twice denser than in usual DNA. In theory, a DNA sequence has a maximal capacity to produce six different mRNAs, however, it is an intriguing question how many of these mRNAs are able to synthesize functional proteins. Here, we design a DNA sequence encoding four collagen-like proteins, two, (Gly-Arg-Pro)n and (Gly-Ala-Pro)n, from a sense mRNA and the other two, also (Gly-Arg-Pro)n and (Gly-Ala-Pro)n from its antisense mRNA, all of which are expected to form triple-helical structures unique to collagens. Other designs such as the combination of (Gly-Arg-Pro)n, (Gly-Val-Pro)n, (Gly-Thr-Pro)n and (Gly-Arg-Pro)n are also possible. The proposed DNA sequence is considered to contain the most compact genetic information ever created.

Characterization of a membrane toxin-antitoxin system, tsaAT, from Staphylococcus aureus.

Bacterial toxin-antitoxin (TA) systems consist of a toxin that inhibits essential cellular processes, such as DNA replication, transcription, translation, or ATP synthesis, and an antitoxin neutralizing their cognate toxin. These systems have roles in programmed cell death, defense against phage, and the formation of persister cells. Here, we characterized the previously identified Staphylococcus aureus TA system, tsaAT, which consists of two putative membrane proteins: TsaT and TsaA. Expression of the TsaT toxin caused cell death and disrupted membrane integrity, whereas TsaA did not show any toxicity and neutralized the toxicity of TsaT. Furthermore, subcellular fractionation analysis demonstrated that both TsaA and TsaT localized to the cytoplasmic membrane of S. aureus expressing either or both 3xFLAG-tagged TsaA and 3xFLAG-tagged TsaT. Taken together, these results demonstrate that the TsaAT TA system consists of two membrane proteins, TsaA and TsaT, where TsaT disrupts membrane integrity, ultimately leading to cell death. Although sequence analyses showed that the tsaA and tsaT genes were conserved among Staphylococcus species, amino acid substitutions between TsaT orthologs highlighted the critical role of the 6th residue for its toxicity. Further amino acid substitutions indicated that the glutamic acid residue at position 63 in the TsaA antitoxin and the cluster of five lysine residues in the TsaT toxin are involved in TsaA's neutralization reaction. This study is the first to describe a bacterial TA system wherein both toxin and antitoxin are membrane proteins. These findings contribute to our understanding of S. aureus TA systems and, more generally, give new insight into highly diverse bacterial TA systems.

Lens Material of the Eyelid Masquerading as Phakomatous Choristoma After Cataract Surgery.

Cataract surgery is the most commonly performed surgery worldwide. While retained lens fragments after cataract surgery are common, to our knowledge, there is no prior case report of the lens material being deposited outside of the eye. Here, we present a case of an elderly patient with an upper eyelid lesion containing a fragment of the basement membrane and proteinaceous lens-like material, initially mistaken as phakomatous choristoma. Phakomatous choristoma is a type of benign congenital tumor consisting of lens tissue, which is thought to be secondary to aberrant migration during lens formation. Upon further review, it was later confirmed to be postoperative capsular material embedded into the eyelid.

A novel gyrase inhibitor from toxin-antitoxin system expressed by Staphylococcus aureus.

Toxin-antitoxin (TA) systems consist of a toxin inhibiting essential cellular functions (such as DNA, RNA and protein synthesis), and its cognate antitoxin neutralizing the toxicity. Recently, we identified a TA system termed TsbA/TsbT in the Staphylococcus aureus genome. The induction of the tsbT gene in Escherichia coli halted both DNA and RNA synthesis, reduced supercoiled plasmid and resulted in increasingly relaxed DNA. These results suggested that DNA gyrase was the target of TsbT. In addition, TsbT inhibited both E. coli and S. aureus DNA gyrase activity and induced linearization of plasmid DNA in vitro. Taken together, these results demonstrate that the TsbT toxin targets DNA gyrase in vivo. Site-directed mutagenesis experiments showed that the E27 and D37 residues in TsbT are critical for toxicity. Secondary structure prediction combining the analysis of vacuum-ultraviolet circular-dichroism spectroscopy and neural network method demonstrated that the 22nd-32nd residues of TsbT form an α-helix structure, and that the E27 residue is located around the centre of the α-helix segment. These findings give new insights not only into S. aureus TA systems, but also into bacterial toxins targeting DNA topoisomerases.

Engineered Vesicles and Hydrogel Technologies for Myocardial Regeneration.

Increased prevalence of cardiovascular disease and potentially life-threatening complications of myocardial infarction (MI) has led to emerging therapeutic approaches focusing on myocardial regeneration and restoration of physiologic function following infarction. Extracellular vesicle (EV) technology has gained attention owing to the biological potential to modulate cellular immune responses and promote the repair of damaged tissue. Also, EVs are involved in local and distant cellular communication following damage and play an important role in initiating the repair process. Vesicles derived from stem cells and cardiomyocytes (CM) are of particular interest due to their ability to promote cell growth, proliferation, and angiogenesis following MI. Although a promising candidate for myocardial repair, EV technology is limited by the short retention time of vesicles and rapid elimination by the body. There have been several successful attempts to address this shortcoming, which includes hydrogel technology for the sustained bioavailability of EVs. This review discusses and summarizes current understanding regarding EV technology in the context of myocardial repair.