Biology subjects

Shiraishi, A.

Publications and source records attributed to Shiraishi, A..

4 recordsLinked to original sources

bioRxiv2024

Stimulatory and inhibitory G-protein signaling relays drive cAMP accumulation for timely metamorphosis in the chordate Ciona

Larvae of the ascidian Ciona initiate metamorphosis tens of minutes after adhesion to a substratum via their adhesive organ. The gap between adhesion and metamorphosis initiation is suggested to ensure the rigidity of adhesion, allowing Ciona to maintain settlement after losing locomotive activity through metamorphosis. The mechanism producing the gap is unknown. Here, by combining gene functional analyses, pharmacological analyses, and live imaging, we propose that the gap represents the time required for sufficient cAMP accumulation to trigger metamorphosis. Not only the Gs pathway but also the Gi and Gq pathways are involved in the initiation of metamorphosis in the downstream signaling cascade of the neurotransmitter GABA, the known initiator of Ciona metamorphosis. The mutual crosstalk of stimulatory and inhibitory G-proteins functions as the accelerator and brake for cAMP production, ensuring the faithful initiation of metamorphosis at an appropriate time and in the right situation.

developmental biology↗

bioRxiv2023

Pax3 and Pax7 function in combination with Mitf to generate melanophores and xanthophores in medaka and zebrafish

Neural crest cells generate numerous derivatives, including pigment cells, and are a model for studying how fate specification from multipotent progenitors is controlled. In mammals, the core gene regulatory network (GRN) for melanocytes (their only pigment cell-type) contains three transcription factors Sox10, Pax3 and Mitf, with the latter considered a master regulator of melanocyte development. In teleosts, which have three to four pigment cell types (melanophores, iridophores and xanthophores, plus leucophores e.g. in medaka), GRNs governing fate specification are poorly understood, although Mitf function is considered conserved. Here, we show that the regulatory relationships between Sox10, Pax3 and Mitf are conserved in zebrafish, but the role for Mitf is more complex than previously emphasised, affecting xanthophore development too. Similarly, medaka Mitf is necessary for melanophore, xanthophore and leucophore formation. Furthermore, expression patterns and mutant phenotypes of pax3 and pax7 suggest that Pax3 and Pax7 act sequentially, activating mitf expression. Pax7 modulates Mitf function, driving co-expressing cells to differentiate as xanthophores and leucophores rather than melanophores. We propose that pigment cell fate specification is better considered as resulting from the combinatorial activity of Mitf with other transcription factors.

developmental biology↗

bioRxiv2023

In vivo long-term voltage imaging by genetically encoded voltage indicator reveals spatiotemporal dynamics of spinal cord neuronal populations during development

One of the central questions in neural development is how individual neurons assemble functional networks. To address this, it is essential to elucidate how coordinated activity emerges during development. However, tracking the functional maturation of neuronal populations over time remains challenging, as it requires long-term, non-invasive monitoring of membrane potential dynamics. Here, we developed a voltage imaging approach for zebrafish embryos using genetically encoded voltage indicators (GEVIs), enabling fast, direct and cell-type-specific measurements of membrane potentials from defined neuronal populations in a non-invasive manner. Using this approach, we detected coordinated voltage changes in spinal motor neurons with high spatiotemporal resolution. Depolarization and hyperpolarization events were observed at the population, single-cell, and subcellular levels. Notably, long-term voltage imaging revealed the early emergence and progressive maturation of membrane potential dynamics, characterized by increased firing rate, coupling strength and axonal outgrowth. This optical approach constitutes a significant advancement in the study of neural development, providing a powerful tool for investigating the spatiotemporal dynamics of neuronal populations in vivo.

neuroscience↗

bioRxiv2021

Comparative analysis of transcriptomic profiles among ascidians, zebrafish, and mice: insights from tissue-specific gene expression

Tissue/organ-specific genes (TSGs) are important not only for understanding organ development and function, but also for investigating the evolutionary lineages of organs in animals. Here, we investigate the TSGs of 9 adult tissues of an ascidian, Ciona intestinalis Type A (Ciona robusta), which lies in the important position of being the sister group of vertebrates. RNA-seq and qRT-PCR identified the Ciona TSGs in each tissue, and BLAST searches identified their homologs in zebrafish and mice. Tissue distributions of the vertebrate homologs were analyzed and clustered using public RNA-seq data for 12 zebrafish and 30 mouse tissues. Among the vertebrate homologs of the Ciona TSGs in the neural complex, 48% and 63% showed high expression in the zebrafish and mouse brain, respectively, suggesting that the central nervous system is evolutionarily conserved in chordates. In contrast, vertebrate homologs of Ciona TSGs in the ovary, pharynx, and intestine were not consistently highly expressed in the corresponding tissues of vertebrates, suggesting that these organs have evolved in Ciona-specific lineages. Intriguingly, more TSG homologs of the Ciona stomach were highly expressed in the vertebrate liver (17-29%) and intestine (22-33%) than in the mouse stomach (5%). Expression profiles for these gene suggest that the biological roles of the Ciona stomach are distinct from those of their vertebrate counterparts. Collectively, Ciona tissues were categorized into 3 groups: i) high similarity to the corresponding vertebrate tissues (neural complex and heart), ii) low similarity to the corresponding vertebrate tissues (ovary, pharynx, and intestine), and iii) low similarity to the corresponding vertebrate tissues, but high similarity to other vertebrate tissues (stomach, endostyle, and siphons). The present study provides transcriptomic catalogs of adult ascidian tissues and significant insights into the evolutionary lineages of the brain, heart, and digestive tract of chordates.

evolutionary biology↗