Biology subjects

Sakaguchi, A.

Publications and source records attributed to Sakaguchi, A..

3 recordsLinked to original sources

bioRxiv2024

Postnatal xanthine metabolism regulates cardiac regeneration in mammals

Postnatal cardiomyocyte cell cycle withdrawal is a critical step wherein the mammalian heart loses regenerative potential after birth. Here, we conducted interspecies multi-omic comparisons between the mouse heart and that of the opossum, which have different postnatal time-windows for cardiomyocyte cell cycle withdrawal. Xanthine metabolism was activated in both postnatal hearts in parallel with cardiomyocyte cell cycle arrest. The pentose phosphate pathway (PPP) which produces NADPH was found to decrease simultaneously. Postnatal myocardial tissues became oxidized accordingly, and administration of antioxidants to neonatal mice altered the PPP and suppressed the postnatal activation of cardiac xanthine metabolism. These results suggest a redox-dependent postnatal switch from purine synthesis to degradation in the heart. Inhibition of xanthine metabolism in the postnatal heart extended postnatal duration of cardiomyocyte proliferation and maintained postnatal heart regeneration potential in mice. These findings highlight a novel role of xanthine metabolism as a metabolic regulator of cardiac regeneration potential.

developmental biology↗

bioRxiv2021

BITC induces cardiomyocyte proliferation and heart regeneration

Cardiomyocyte proliferation is an evolutionarily conserved mechanism that supports cardiac regeneration in vertebrates. Mammalian cardiomyocytes are arrested from the cell cycle shortly after birth, and therefore mammals lose the ability to regenerate injured myocardium for the rest of their lives. Pharmacological induction of cardiomyocyte proliferation has gained a lot of interest in recent years, as researchers strive to achieve heart tissue regeneration. Here we show that a small chemical, benzyl isothiocyanate (BITC), induced cardiomyocyte proliferation through activation of the cyclin-dependent kinase (CDK) pathway. BITC treatment also allowed heart regeneration in the infarcted neonatal heart, even after the regeneration period in mice. Furthermore, administration of BITC to adult mice in parallel with mild hypoxia (10% O2) induced cell cycle reentry and tissue regeneration in the adult heart. Our findings thus suggest that pharmacological activation of the CDK pathway using BITC, concurrently with the activation of hypoxia-related signaling pathways, may be a promising approach to inducing cardiac regeneration in patients with heart disease.

pharmacology and toxicology↗

bioRxiv2018

DAF-16/Foxo suppresses the transgenerational sterility of prg-1 piRNA mutants via a systemic small RNA pathway

Mutation of the daf-2 insulin/IGF-1 receptor activates the DAF-16/Foxo transcription factor to suppress the transgenerational sterility phenotype of prg-1/piRNA mutants that are deficient for piRNA-mediated genome silencing. As with PRG-1/piRNAs, mutations in the nuclear RNA interference gene nrde-1 compromised germ cell immortality, but deficiency for daf-2 did not suppress the transgenerational sterility of nrde-1 or nrde-4 single mutants or of prg-1; nrde-4 or prg-1; hrde-1 double mutants. NRDE-1 and NRDE-4 promote transcriptional silencing in somatic cells via the nuclear Argonaute protein NRDE-3, which was dispensable for germ cell immortality. However, daf-2 deficiency failed to promote germ cell immortality in prg-1; nrde-3 mutants. Consistently, we found that DAF-16 activity in somatic cells suppressed the transgenerational sterility of prg-1 mutants via the SID-1 dsRNA transmembrane channel that promotes systemic RNAi as well as Dicer, the dsRNA binding protein RDE-4 and the RDRP RRF-3. We conclude that DAF-16 activates a cell-non-autonomous systemic RNAi pathway that promotes small RNA-mediated genome silencing in germ cells to suppress loss of the genomic immune surveillance factor Piwi/PRG-1. Author SummarySmall RNAs can promote genome silencing. The Argonaute protein Piwi interacts with thousands of small RNAs termed piRNAs in germ cells to suppress expression of transposons and foreign genetic elements. However, the Piwi silencing system may be commonly targeted by viral or transposon genomic parasites that seek to suppress the endogenous defences against their expression and replication. Activation of the DAF-16 stress response pathway promotes adult longevity and can also abolish the transgenerational sterility of C. elegans Piwi mutants. We found that DAF-16 accomplishes this by activating a somatic small RNA pathway where small RNAs are initially produced in the soma and are then transported into the germline to suppress expression of a toxic genetic locus in Piwi mutants. Thus, the DAF-16 stress response pathway activates a systemic small RNA cascade to suppress defects in the Piwi/piRNA genome silencing system.

genetics↗