KLF8 is activated by TGF-ß1 via Smad2 and contributes to ovarian cancer progression.

Krüppel-like factor 8 (KLF8) is a transcription factor expressed abnormally in various cancer types and promotes oncogenic transformation. However, the role of KLF8 in ovarian cancer (OC) progression remains unclear. This study reports that transforming growth factor-ß1 (TGF-ß1)/Smad2/KLF8 axis regulates epithelial-mesenchymal transition (EMT) and contributes to OC progression. We analyzed the KLF8 expression in OC cells and tissues, wherein a significant overexpression of KLF8 was observed. Increased KLF8 expressions were correlated with higher cell proliferation, EMT, migration, and invasion and conferred poor clinical outcomes in OC patients. Overexpressed KLF8 increases F-actin polymerization and induces cytoskeleton remodeling of OC cells. Furthermore, a dissection of the molecular mechanism defined that TGF-ß1 triggers KLF8 through the Smad2 pathway and regulates EMT. Pharmacological and genetic inhibition of Smad2 followed by TGF-ß1 treatment failed to activate KLF8 expression and induction of EMT. Using promoter-luciferase reporter assays, we defined that upon TGF-ß1 activation, phosphorylated Smad2 binds and promotes the KLF8 promoter activity, and knockdown of Smad2 inhibits KLF8 promoter activation. Together, these results demonstrate that TGF-ß1 activates KLF8 expression by the Smad2 pathway, and KLF8 contributes to OC progression and may serve as a potential therapeutic strategy for treating OC patients.

AUTS2 Regulates RNA Metabolism and Dentate Gyrus Development in Mice.

Human AUTS2 mutations are linked to a syndrome of intellectual disability, autistic features, epilepsy, and other neurological and somatic disorders. Although it is known that this unique gene is highly expressed in developing cerebral cortex, the molecular and developmental functions of AUTS2 protein remain unclear. Using proteomics methods to identify AUTS2 binding partners in neonatal mouse cerebral cortex, we found that AUTS2 associates with multiple proteins that regulate RNA transcription, splicing, localization, and stability. Furthermore, AUTS2-containing protein complexes isolated from cortical tissue bound specific RNA transcripts in RNA immunoprecipitation and sequencing assays. Deletion of all major functional isoforms of AUTS2 (full-length and C-terminal) by conditional excision of exon 15 caused breathing abnormalities and neonatal lethality when Auts2 was inactivated throughout the developing brain. Mice with limited inactivation of Auts2 in cerebral cortex survived but displayed abnormalities of cerebral cortex structure and function, including dentate gyrus hypoplasia with agenesis of hilar mossy neurons, and abnormal spiking activity on EEG. Also, RNA transcripts that normally associate with AUTS2 were dysregulated in mutant mice. Together, these findings indicate that AUTS2 regulates RNA metabolism and is essential for development of cerebral cortex, as well as subcortical breathing centers.

Long noncoding RNAs in intestinal homeostasis, regeneration, and cancer.

Signaling pathways that regulate homeostasis and regeneration are found to be deregulated in various human malignancies. Accordingly, attempts have been made to target them at the protein level with little success. However, studies using high-throughput sequencing technologies suggest that only about 2% of the genome translates into proteins, whereas about 75% of the genome is transcribed into noncoding RNAs. Among noncoding RNAs, long noncoding RNAs (lncRNAs) have received tremendous attention in recent years as a crucial player in the regulation of almost all cellular processes involved in tissue homeostasis as well as in the development of various malignancies, including intestinal cancer. Emerging evidence suggests that lncRNAs play an instrumental role in the regulation of intestinal stem cells, injury-induced regeneration, and initiation and progression of intestinal tumors. Here, we summarize the recently discovered lncRNAs during intestinal homeostasis, regeneration, and tumorigenesis. We further present lncRNAs as diagnostic and therapeutic markers in intestinal pathologies.

Neuroinvasion of SARS-CoV-2 may play a role in the breakdown of the respiratory center of the brain.

The recent outbreak of the novel coronavirus, SARS-CoV-2, has emerged to be highly pathogenic in nature. Although lungs are considered as the primary infected organs by SARS-CoV-2, some of the other organs, including the brain, have also been found to be affected. Here, we have discussed how SARS-CoV-2 might infect the brain. The infection of the respiratory center in the brainstem could be hypothesized to be responsible for the respiratory failure in many COVID-19 patients. The virus might gain entry through the olfactory bulb and invade various parts of the brain, including the brainstem. Alternatively, the entry might also occur from peripheral circulation into the central nervous system by compromising the blood-brain barrier. Finally, yet another possible entry route could be its dispersal from the lungs into the vagus nerve via the pulmonary stretch receptors, eventually reaching the brainstem. Therefore, screening neurological symptoms in COVID-19 patients, especially toward the breakdown of the respiratory center in the brainstem, might help us better understand this disease.

DNA polymerase eta: A potential pharmacological target for cancer therapy.

In the last two decades, intensive research has been carried out to improve the survival rates of cancer patients. However, the development of chemoresistance that ultimately leads to tumor relapse poses a critical challenge for the successful treatment of cancer patients. Many cancer patients experience tumor relapse and ultimately die because of treatment failure associated with acquired drug resistance. Cancer cells utilize multiple lines of self-defense mechanisms to bypass chemotherapy and radiotherapy. One such mechanism employed by cancer cells is translesion DNA synthesis (TLS), in which specialized TLS polymerases bypass the DNA lesion with the help of monoubiquitinated proliferating cell nuclear antigen. Among all TLS polymerases (Pol η, Pol ι, Pol κ, REV1, Pol ζ, Pol µ, Pol λ, Pol ν, and Pol θ), DNA polymerase eta (Pol η) is well studied and majorly responsible for the bypass of cisplatin and UV-induced DNA damage. TLS polymerases contribute to chemotherapeutic drug-induced mutations as well as therapy resistance. Therefore, targeting these polymerases presents a novel therapeutic strategy to combat chemoresistance. Mounting evidence suggests that inhibition of Pol η may have multiple impacts on cancer therapy such as sensitizing cancer cells to chemotherapeutics, suppressing drug-induced mutagenesis, and inhibiting the development of secondary tumors. Herein, we provide a general introduction of Pol η and its clinical implications in blocking acquired drug resistance. In addition; this review addresses the existing gaps and challenges of Pol η mediated TLS mechanisms in human cells. A better understanding of the Pol η mediated TLS mechanism will not merely establish it as a potential pharmacological target but also open possibilities to identify novel drug targets for future therapy.

Reelin Mediates Hippocampal Cajal-Retzius Cell Positioning and Infrapyramidal Blade Morphogenesis.

We have previously described hypomorphic reelin (Reln) mutant mice, RelnCTRdel, in which the morphology of the dentate gyrus is distinct from that seen in reeler mice. In the RelnCTRdel mutant, the infrapyramidal blade of the dentate gyrus fails to extend, while the suprapyramidal blade forms with a relatively compact granule neuron layer. Underlying this defect, we now report several developmental anomalies in the RelnCTRdel dentate gyrus. Most strikingly, the distribution of Cajal-Retzius cells was aberrant; Cajal-Retzius neurons were increased in the suprapyramidal blade, but were greatly reduced along the subpial surface of the prospective infrapyramidal blade. We also observed multiple abnormalities of the fimbriodentate junction. Firstly, progenitor cells were distributed abnormally; the "neurogenic cluster" at the fimbriodentate junction was absent, lacking the normal accumulation of Tbr2-positive intermediate progenitors. However, the number of dividing cells in the dentate gyrus was not generally decreased. Secondly, a defect of secondary glial scaffold formation, limited to the infrapyramidal blade, was observed. The densely radiating glial fibers characteristic of the normal fimbriodentate junction were absent in mutants. These fibers might be required for migration of progenitors, which may account for the failure of neurogenic cluster formation. These findings suggest the importance of the secondary scaffold and neurogenic cluster of the fimbriodentate junction in morphogenesis of the mammalian dentate gyrus. Our study provides direct genetic evidence showing that normal RELN function is required for Cajal-Retzius cell positioning in the dentate gyrus, and for formation of the fimbriodentate junction to promote infrapyramidal blade extension.

Healthy Gut, Healthy Brain: The Gut Microbiome in Neurodegenerative Disorders.

BACKGROUND: The central nervous system (CNS) known to regulate the physiological conditions of human body, also itself gets dynamically regulated by both the physiological as well as pathological conditions of the body. These conditions get changed quite often, and often involve changes introduced into the gut microbiota which, as studies are revealing, directly modulate the CNS via a crosstalk. This cross-talk between the gut microbiota and CNS, i.e., the gut-brain axis (GBA), plays a major role in the pathogenesis of many neurodegenerative disorders such as Parkinson's disease (PD), Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS) and Huntington's disease (HD). OBJECTIVE: We aim to discuss how gut microbiota, through GBA, regulate neurodegenerative disorders such as PD, AD, ALS, MS and HD. METHODS: In this review, we have discussed the present understanding of the role played by the gut microbiota in neurodegenerative disorders and emphasized the probable therapeutic approaches being explored to treat them. RESULTS: In the first part, we introduce the GBA and its relevance, followed by the changes occurring in the GBA during neurodegenerative disorders and then further discuss its role in the pathogenesis of these diseases. Finally, we discuss its applications in possible therapeutics of these diseases and the current research improvements being made to better investigate this interaction. CONCLUSION: We concluded that alterations in the intestinal microbiota modulate various activities that could potentially lead to CNS disorders through interactions via the GBA.

C-Terminal Region Truncation of RELN Disrupts an Interaction with VLDLR, Causing Abnormal Development of the Cerebral Cortex and Hippocampus.

We discovered a hypomorphic reelin (Reln) mutant with abnormal cortical lamination and no cerebellar hypoplasia. This mutant, RelnCTRdel, carries a chemically induced splice-site mutation that truncates the C-terminal region (CTR) domain of RELN protein and displays remarkably distinct phenotypes from reeler The mutant does not have an inverted cortex, but cortical neurons overmigrate and invade the marginal zone, which are characteristics similar to a phenotype seen in the cerebral cortex of Vldlrnull mice. The dentate gyrus shows a novel phenotype: the infrapyramidal blade is absent, while the suprapyramidal blade is present and laminated. Genetic epistasis analysis showed that RelnCTRdel/Apoer2null double homozygotes have phenotypes akin to those of reeler mutants, while RelnCTRdel/Vldlrnull mice do not. Given that the receptor double knock-out mice resemble reeler mutants, we infer that RelnCTRdel/Apoer2null double homozygotes have both receptor pathways disrupted. This suggests that CTR-truncation disrupts an interaction with VLDLR (very low-density lipoprotein receptor), while the APOER2 signaling pathway remains active, which accounts for the hypomorphic phenotype in RelnCTRdel mice. A RELN-binding assay confirms that CTR truncation significantly decreases RELN binding to VLDLR, but not to APOER2. Together, the in vitro and in vivo results demonstrate that the CTR domain confers receptor-binding specificity of RELN. SIGNIFICANCE STATEMENT: Reelin signaling is important for brain development and is associated with human type II lissencephaly. Reln mutations in mice and humans are usually associated with cerebellar hypoplasia. A new Reln mutant with a truncation of the C-terminal region (CTR) domain shows that Reln mutation can cause abnormal phenotypes in the cortex and hippocampus without cerebellar hypoplasia. Genetic analysis suggested that CTR truncation disrupts an interaction with the RELN receptor VLDLR (very low-density lipoprotein receptor); this was confirmed by a RELN-binding assay. This result provides a mechanistic explanation for the hypomorphic phenotype of the CTR-deletion mutant, and further suggests that Reln mutations may cause more subtle forms of human brain malformation than classic lissencephalies.

Kainic acid-induced seizures activate GSK-3ß in the hippocampus of D2R-/- mice.

Dopamine D2 receptor (D2R) signalling is implicated in limbic seizure propagation and seizure-induced neurodegeneration. D2R-/- mice display increased susceptibility to kainic acid (KA) seizures and seizure-induced apoptosis of hippocampal neurons. Here we further investigated the molecular pathways of KA-induced apoptosis in the D2R-/- hippocampus. Immunoblotting experiments showed a marked induction of caspase 3 in the D2R-/- but not in the wild-type hippocampus, 24 h after the administration of KA. The activation of the Akt/glycogen synthase kinase-3beta (GSK-3beta) pathway that has been implicated in neuronal apoptosis was also studied at the same time. No difference in Akt phosphorylation in the hippocampus was detected between the two genotypes, whereas GSK-3beta phosphorylation was markedly downregulated in D2R-/- mice. Our results suggest that GSK-3beta activation participates, independently of Akt, in the KA-induced apoptosis in the D2R-/- hippocampus.