Inherited C-terminal TREX1 variants disrupt homology-directed repair to cause senescence and DNA damage phenotypes in Drosophila, mice, and humans.

Age-related microangiopathy, also known as small vessel disease (SVD), causes damage to the brain, retina, liver, and kidney. Based on the DNA damage theory of aging, we reasoned that genomic instability may underlie an SVD caused by dominant C-terminal variants in TREX1, the most abundant 3'-5' DNA exonuclease in mammals. C-terminal TREX1 variants cause an adult-onset SVD known as retinal vasculopathy with cerebral leukoencephalopathy (RVCL or RVCL-S). In RVCL, an aberrant, C-terminally truncated TREX1 mislocalizes to the nucleus due to deletion of its ER-anchoring domain. Since RVCL pathology mimics that of radiation injury, we reasoned that nuclear TREX1 would cause DNA damage. Here, we show that RVCL-associated TREX1 variants trigger DNA damage in humans, mice, and Drosophila, and that cells expressing RVCL mutant TREX1 are more vulnerable to DNA damage induced by chemotherapy and cytokines that up-regulate TREX1, leading to depletion of TREX1-high cells in RVCL mice. RVCL-associated TREX1 mutants inhibit homology-directed repair (HDR), causing DNA deletions and vulnerablility to PARP inhibitors. In women with RVCL, we observe early-onset breast cancer, similar to patients with BRCA1/2 variants. Our results provide a mechanistic basis linking aberrant TREX1 activity to the DNA damage theory of aging, premature senescence, and microvascular disease.

Heterozygous loss-of-function DHX9 variants are associated with neurodevelopmental disorders: Human genetic and experimental evidences.

DExH-box helicases are involved in unwinding of RNA and DNA. Among the 16 DExH-box genes, monoallelic variants of DHX16, DHX30, DHX34, and DHX37 are known to be associated with neurodevelopmental disorders. In particular, DHX30 is well established as a causative gene for neurodevelopmental disorders. Germline variants of DHX9, the closest homolog of DHX30, have not been reported until now as being associated with congenital disorders in humans, except that one de novo heterozygous variant, p.(Arg1052Gln) of the gene was identified during comprehensive screening in a patient with autism; unfortunately, the phenotypic details of this individual are unknown. Herein, we report a patients with a heterozygous de novo missense variant, p.(Gly414Arg) of DHX9 who presented with a short stature, intellectual disability, and ventricular non-compaction cardiomyopathy. The variant was located in the glycine codon of the ATP-binding site, G-C-G-K-T. To assess the pathogenicity of these variants, we generated transgenic Drosophila lines expressing human wild-type and mutant DHX9 proteins: 1) the mutant proteins showed aberrant localization both in the nucleus and the cytoplasm; 2) ectopic expression of wild-type protein in the visual system led to the rough eye phenotype, whereas expression of the mutant proteins had minimal effect; 3) overexpression of the wild-type protein in the retina led to a reduction in axonal numbers, whereas expression of the mutant proteins had a less pronounced effect. Furthermore, in a gene-editing experiment of Dhx9 G416 to R416, corresponding to p.(Gly414Arg) in humans, heterozygous mice showed a reduced body size, reduced emotionality, and cardiac conduction abnormality. In conclusion, we established that heterozygosity for a loss-of-function variant of DHX9 can lead to a new neurodevelopmental disorder.

Detoxification of amyloid ß fibrils by curcumin derivatives and their verification in a Drosophila Alzheimer's model.

Curcumin derivatives B and N were developed as disaggregation agents of amyloid ß (Aß) fibrils. The detoxification provided by each compound at a concentration of 1 µM was observed in neuroblastoma cells. Furthermore, both compounds significantly rescued locomotion dysfunction in an Aß-expressing Drosophila model of Alzheimer's disease.

De novo ARF3 variants cause neurodevelopmental disorder with brain abnormality.

An optimal Golgi transport system is important for mammalian cells. The adenosine diphosphate (ADP) ribosylation factors (ARF) are key proteins for regulating cargo sorting at the Golgi network. In this family, ARF3 mainly works at the trans-Golgi network (TGN), and no ARF3-related phenotypes have yet been described in humans. We here report the clinical and genetic evaluations of two unrelated children with de novo pathogenic variants in the ARF3 gene: c.200A > T (p.Asp67Val) and c.296G > T (p.Arg99Leu). Although the affected individuals presented commonly with developmental delay, epilepsy and brain abnormalities, there were differences in severity, clinical course and brain lesions. In vitro subcellular localization assays revealed that the p.Arg99Leu mutant localized to Golgi apparatus, similar to the wild-type, whereas the p.Asp67Val mutant tended to show a disperse cytosolic pattern together with abnormally dispersed Golgi localization, similar to that observed in a known dominant negative variant (p.Thr31Asn). Pull-down assays revealed that the p.Asp67Val had a loss-of-function effect and the p.Arg99Leu variant had increased binding of the adaptor protein, Golgi-localized, γ-adaptin ear-containing, ARF-binding protein 1 (GGA1), supporting the gain of function. Furthermore, in vivo studies revealed that p.Asp67Val transfection led to lethality in flies. In contrast, flies expressing p.Arg99Leu had abnormal rough eye, as observed in the gain-of-function variant p.Gln71Leu. These data indicate that two ARF3 variants, the possibly loss-of-function p.Asp67Val and the gain-of-function p.Arg99Leu, both impair the Golgi transport system. Therefore, it may not be unreasonable that they showed different clinical features like diffuse brain atrophy (p.Asp67Val) and cerebellar hypoplasia (p.Arg99Leu).

Murahashi coupling polymerization: nickel(II)-N-heterocyclic carbene complex-catalyzed polycondensation of organolithium species of (hetero)arenes.

Revisiting Murahashi coupling, we found that it effectively allows polymerization of lithiated (hetero)arenes by nickel(II)-catalyzed polycondensation. Deprotonative polymerization of 2-chloro-3-substituted thiophene with n-butyllithium gave head-to-tail-type poly(3-substituted thiophene). Poly(1,4-arylene)s were obtained by the reaction of the corresponding dibromides through lithium-bromine exchange. A lithiated thiophene derivative obtained via deprotonative halogen dance also underwent polymerization to afford a bromo-substituted polythiophene.

Concise synthesis of well-defined linear and branched oligothiophenes with nickel-catalyzed regiocontrolled cross-coupling of 3-substituted thiophenes by catalytically generated magnesium amide.

The synthesis of linear and branched oligothiophenes of well-defined structures is performed with regioselective deprotonation of 3-substituted thiophenes and nickel-catalyzed cross-coupling of the thus formed metalated species with a bromothiophene. The reaction of 3-hexylthiophene with EtMgCl and 2,2,6,6-tetramethylpiperidine (TMP-H, 10 mol%) induces the metalation selectively at the 5-position by use of the catalytically generated hindered magnesium amide (TMPMgCl) and the subsequent reaction of a 2-halo-3-hexylthiophene (bromide or chloride) in the presence of a nickel catalyst affords a head-to-tail (HT)-type dimer. By repeating the same sequence, the linear oligothiophene up to a 4-mer is synthesized in good yield. The reaction of 3-hexylthiophene with 2,3-dibromothiophene also takes place to afford a branched oligothiophene 3-mer in quantitative yield. The obtained 3-mer is also metalated at the sterically less-hindered position in a regioselective manner furnishing a 7-mer in >99% yield after a further coupling reaction with 2,3-dibromothiophene. These dendrimers react with several multifunctionalized organic electrophiles, leading to a variety of branched oligothiophenes.

Synthesis of well-defined head-to-tail-type oligothiophenes by regioselective deprotonation of 3-substituted thiophenes and nickel-catalyzed cross-coupling reaction.

Iterative growth of thiophene oligomers by single-step extensions has been realized by regioselective metalation of 3-substituted thiophenes with the Knochel-Hauser base (TMPMgCl·LiCl) and coupling with bromothiophene using a nickel catalyst. Treatment of 3-hexylthiophene with TMPMgCl·LiCl induces metalation at the 5-position selectively. Subsequent addition of 2-bromo-3-hexylthiophene and a nickel catalyst leads to the corresponding bithiophene. The obtained bithiophene is converted to the terthiophene and then to the quaterthiophene by repeating the similar protocol. A concise synthesis of MK-1 and MK-2, which are organic dye molecules bearing an oligothiophene moiety that are used in photovoltaic cells, has been achieved.

C-H functionalization polycondensation of chlorothiophenes in the presence of nickel catalyst with stoichiometric or catalytically generated magnesium amide.

Polymerization of 2-chloro-3-substituted thiophenes proceeded with a stoichiometric amount of magnesium amide, TMPMgCl·LiCl, or a combination of a Grignard reagent and a catalytic amount of secondary amine in the presence of a nickel catalyst. Although the nickel-catalyzed polymerization with NiCl(2)dppe, which exhibited high catalytic activity in the reaction of bromothiophenes, was less effective, use of a nickel catalyst bearing N-heterocyclic carbene as a ligand was found to induce polymerization with controlled molecular weight and molecular weight distribution.

Coordinated sequential action of EGFR and Notch signaling pathways regulates proneural wave progression in the Drosophila optic lobe.

During neurogenesis in the medulla of the Drosophila optic lobe, neuroepithelial cells are programmed to differentiate into neuroblasts at the medial edge of the developing optic lobe. The wave of differentiation progresses synchronously in a row of cells from medial to the lateral regions of the optic lobe, sweeping across the entire neuroepithelial sheet; it is preceded by the transient expression of the proneural gene lethal of scute [l(1)sc] and is thus called the proneural wave. We found that the epidermal growth factor receptor (EGFR) signaling pathway promotes proneural wave progression. EGFR signaling is activated in neuroepithelial cells and induces l(1)sc expression. EGFR activation is regulated by transient expression of Rhomboid (Rho), which is required for the maturation of the EGF ligand Spitz. Rho expression is also regulated by the EGFR signal. The transient and spatially restricted expression of Rho generates sequential activation of EGFR signaling and assures the directional progression of the differentiation wave. This study also provides new insights into the role of Notch signaling. Expression of the Notch ligand Delta is induced by EGFR, and Notch signaling prolongs the proneural state. Notch signaling activity is downregulated by its own feedback mechanism that permits cells at proneural states to subsequently develop into neuroblasts. Thus, coordinated sequential action of the EGFR and Notch signaling pathways causes the proneural wave to progress and induce neuroblast formation in a precisely ordered manner.

Sunspot, a link between Wingless signaling and endoreplication in Drosophila.

The Wingless (Wg)/Wnt signaling pathway is highly conserved throughout many multicellular organisms. It directs the development of diverse tissues and organs by regulating important processes such as proliferation, polarity and the specification of cell fates. Upon activation of the Wg/Wnt signaling pathway, Armadillo (Arm)/beta-catenin is stabilized and interacts with the TCF family of transcription factors, which in turn activate Wnt target genes. We show here that Arm interacts with a novel BED (BEAF and Dref) finger protein that we have termed Sunspot (Ssp). Ssp transactivates Drosophila E2F-1 (dE2F-1) and PCNA expression, and positively regulates the proliferation of imaginal disc cells and the endoreplication of salivary gland cells. Wg negatively regulates the function of Ssp by changing its subcellular localization in the salivary gland. In addition, Ssp was found not to be involved in the signaling pathway mediated by Arm associated with dTCF. Our findings indicate that Arm controls development in part by regulating the function of Ssp.

Roles of human CYP2A6 and 2B6 and rat CYP2C11 and 2B1 in the 10-hydroxylation of (-)-verbenone by liver microsomes.

(-)-Verbenone, a monoterpene bicyclic ketone, is a component of the essential oil from rosemary species such as Rosmarinus officinalis L., Verbena triphylla, and Eucalyptus globulus and is used for an herb tea, a spice, and a perfume. In this study, (-)-verbenone was found to be converted to 10-hydroxyverbenone by rat and human liver microsomal cytochrome p450 (p450) enzymes. The product formation was determined by high-performance liquid chromatography with UV detection at 251 nm. There was a good correlation between activities of coumarin 7-hydroxylation and (-)-verbenone 10-hydroxylation catalyzed by liver microsomes of 16 human samples, indicating that CYP2A6 is a principal enzyme in (-)-verbenone 10-hydroxylation in humans. Human recombinant CYP2A6 and CYP2B6 catalyzed (-)verbenone 10-hydroxylation at Vmax values of 15 and 21 nmol/min/nmol p450 with apparent Km values of 16 and 91 microM, respectively. In contrast, rat CYP2A1 and 2A2 did not catalyze (-)-verbenone 10-hydroxylation at all, suggesting that there were species-related differences in the catalytic properties of human and rat CYP2A enzymes in the metabolism of (-)-verbenone. In the rat, recombinant CYP2C11, CYP2B1, and CYP3A2 catalyzed (-)-verbenone 10-hydroxylation with Vmax and Km ratios (ml/min/nmol p450) of 0.73, 0.20, and 0.03, respectively. Male-specific CYP2C11 was a major enzyme in (-)-verbenone 10-hydroxylation by untreated rat livers, and CYP2B1 catalyzed this reaction in liver microsomes of phenobarbital-treated rats. Rat CYP2C12, a female-specific enzyme, did not catalyze (-)verbenone 10-hydroxylation. These results suggest that human CYP2A6 and rat CYP2C11 are the major catalysts in the metabolism of (-)-verbenone by liver microsomes and that there are species-related differences in human and rat CYP2A enzymes and sex-related differences in male and female rats in the metabolism of (-)-verbenone.

Tissue-specific induction of cytochromes P450 1A1 and 1B1 by polycyclic aromatic hydrocarbons and polychlorinated biphenyls in engineered C57BL/6J mice of arylhydrocarbon receptor gene.

Tissue-specific induction of mRNA of cytochrome P450 (P450 or CYP) 1A1 and 1B1 by polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) was investigated in wild and arylhydrocarbon receptor (AhR)-deficient C57BL/6J mice. Ratios of mRNA expression of CYP1A1 or CYP1B1 over beta-actin were determined and used to compare levels of expression and induction of these P450s by PAHs and PCBs in various organs. CYP1A1 mRNA was detected in control mice at very low levels in liver, lung, heart, kidney, intestine, thymus, testis, uterus, ovary, and brain and was highly induced in these organs by benzo[a]pyrene and 3,4,3',4'-tetrachlorobiphenyl in AhR(+/+) mice. In AhR(+/+) and AhR(-/-) mice, CYP1B1 mRNA was found to be constitutively expressed at significant levels in heart (the ratio of mRNAs of CYP1B1 to beta-actin was approximately 0.6), kidney ( approximately 0.8), intestine ( approximately 0.3), testis ( approximately 0.9), thymus ( approximately 0.4), uterus ( approximately 0.3), ovary ( approximately 1.4), and brain ( approximately 0.4), whereas it was low in liver and lung (the mRNA ratio to beta-actin was <0.2 in these cases). CYP1B1 in the latter two organs was highly induced by PAHs and 3,4,3',4'-tetrachlorobiphenyl in AhR(+/+) mice. The induction of CYP1B1 by PAHs and PCBs was more extensive in organs in which the constitutive expression of CYP1B1 was low. For example, CYP1B1 was induced 9-fold and 10-fold by benzo[a]pyrene and 3,4,3',4'-tetrachlorobiphenyl in livers of male and female mice, respectively, whereas in testis and ovary, the fold induction of CYP1B1 by two inducers was only 1.1 and 1.4, respectively. Liver microsomal xenobiotic oxidation activities were induced by these PAHs and PCBs in male and female AhR(+/+) mice. These results suggest that CYP1A1 and CYP1B1 are differentially regulated in their expression in extrahepatic organs of mice and could be induced by PAHs and PCBs with different extents of induction depending on the inducers used and the organs examined in AhR(+/+) mice. The findings of significant levels of constitutive expression of CYP1B1 in AhR(-/-) mice as well as AhR(+/+) mice in several organs including heart, kidney, thymus, testis, ovary, and brain in AhR(-/-) mice as well as AhR(+/+) mice are of importance in understanding the basis of toxicity and carcinogenesis by chemicals that are metabolized by CYP1B1.

Arylhydrocarbon receptor-dependent induction of liver and lung cytochromes P450 1A1, 1A2, and 1B1 by polycyclic aromatic hydrocarbons and polychlorinated biphenyls in genetically engineered C57BL/6J mice.

Arylhydrocarbon receptor knock-out, AhR(-/-), mice have recently been shown to be rather resistant to benzo[a]pyrene (B[a]P)-induced tumor formation, probably reflecting the inability of these mice to express significant levels of cytochrome P450 (P450 or CYP) 1A1 that activates B[a]P to reactive metabolites (Y. Shimizu, Y. Nakatsuru, M. Ichinose, Y. Takahashi, H. Kume, J. Mimura, Y. Fujii-Kuriyama and T. Ishikawa (2000) PROC: Natl Acad. Sci. USA, 97, 779-782). However, it is not precisely determined whether CYP1B1, another enzyme that is also active in activating B[a]P, plays a role in the B[a]P carcinogenesis in mice. To understand the basis of roles of CYP1A1 and CYP1B1 in the activation of chemical carcinogens, we compared levels of induction of liver and lung CYP1A1, 1A2, and 1B1 by various polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls in AhR(+/+) and AhR(-/-) mice. Liver and lung CYP1A1 and 1B1 mRNAs were highly induced in AhR(+/+) mice by a single intraperitoneal injection of each of the carcinogenic PAHs, such as B[a]P, 7,12-dimethylbenz[a]anthracene, dibenz[a,l]pyrene, 3-methylcholanthrene, 1,2,5,6-dibenzanthracene, benzo[b]fluoranthene, and benzo[a]anthracene and by a co-planar PCB congener 3,4,3',4'-tetrachlorobiphenyl. We also found that 6-aminochrysene, chrysene, benzo[e]pyrene, and 1-nitropyrene weakly induced the mRNA expression of CYP1A1 and 1B1, whereas anthracene, pyrene, and fluoranthene that have been reported to be non-carcinogenic in rodents, were very low or inactive in inducing these P450s. The extents of induction of liver CYP1A2 by these chemicals were less than those of CYP1A1 and 1B1 in AhR(+/-/+/-) mice. In AhR(-/-) mice, there was no induction of these P450s by PAHs and polychlorinated biphenyls. Liver microsomal activities of 7-ethoxyresorufin and 7-ethoxycoumarin O-deethylations and of mutagenic activation of (+/-)-trans-7,8-dihydroxy-7,8-dihydro-B[a]P to DNA-damaging products were found to correlate with levels of CYP1A1 and 1B1 mRNAs in the liver. Our results suggest that carcinogenicity potencies of PAHs may relate to the potencies of these compounds to induce CYP1A1 and 1B1 through AhR-dependent manner and that these induced P450s participate in the activation of B[a]P and related carcinogens causing initiation of cancers in mice.