Presentation Information
[P04-588]Spatiotemporal Transcriptomic Mapping of the Acanthopleura japonica Radula Reveals Stage-Specific Molecular Control of Iron Biomineralization
○BINTA J.J JALLOW1, Yuto Kubo1, Koki Okada1, David Kisailus2, Michiko Nemoto3 (1. 1Graduate School of Environmental, Life, Natural Science and Technology, Okayama University; Okayama 700-8530, Japan. (Japan), 2. 2Department of Materials Science and Engineering, University of California at Irvine; Irvine, CA 92697, USA. (USA), 3. 3Faculty of Environmental, Life, Natural Science and Technology, Okayama University; Okayama 700-8530, Japan. (Japan))
Keywords:
Acanthopleura japonica,Transcriptome analysis,Differential gene expression,Biomineralization
[Purpose]Chitons are marine molluscs belonging to the class Polyplacophora that inhabit intertidal zones. Their radula is a specialized biomineralized feeding organ exhibiting a spatially organised progression of tooth maturation from immature to fully mineralized ultra-hard structures, which function to scrape rocky surfaces for feeding. Recently, we identified a chiton-specific novel protein RTMP1 that regulates iron oxide deposition in chiton teeth (Science, 2025). However, the molecular mechanism underlying a coordinated radula mineralization process remains poorly understood. In this study, we compared transcriptomes across the four distinct stages of radula tooth mineralization in the chiton Acanthopleura japonica to identify key differentially expressed genes associated with this process.
[Method]RNA was extracted from four distinct regions corresponding to different stages along the radula of A. japonica and sequenced. The reads were aligned to the A. japonica reference genome (GigaByte, 2024) using Bowtie2, and read counts were obtained. Raw data were processed, and differential gene expression analysis was performed using the DESeq2 package in R. Gene expression levels were normalized as transcripts per million (TPM), and differentially expressed genes were further analyzed using Gene Ontology (GO) enrichment analysis with the clusterProfiler package in R.
[Results]Transcriptomic analysis of the four stages of radula mineralization in A. japonica yielded over 450 million clean reads and 28,010 protein-coding genes annotated in five databases. PCA and correlation analysis showed distinct stage-specific clustering and high reproducibility. Differential gene expression analysis revealed sequential transcriptional shifts, with the most significant changes observed between the S1 vs. S4 comparison (2,294 DEGs) and the S1 vs. S2 comparison (1,524 DEGs). GO enrichment analysis revealed stage-specific functional shifts during radula mineralization. In the early stage (S1 vs. S2), genes upregulated in S1 compared with S2 were significantly enriched in extracellular space (CC), chitin binding (MF), and neuron differentiation (BP), suggesting active extracellular matrix formation and tissue differentiation processes. In contrast, genes upregulated in S2 were enriched in cation channel complex (CC), transmembrane transporter activity (MF), and transmembrane transport (BP), indicating a transition in ion transport regulation during early mineralization. In the S1 vs. S4 comparison, enriched GO terms included carbohydrate metabolic process (BP), chitin binding (MF), extracellular region (CC), transmembrane transport (BP), calcium ion binding (MF), and extracellular space (CC), indicating extensive matrix remodeling and dynamic regulation of ion transport during radula mineralization.
[Consideration]
[Conclusion]The results provide new insights into the molecular mechanisms underlying a coordinated radula mineralization process.
[Method]RNA was extracted from four distinct regions corresponding to different stages along the radula of A. japonica and sequenced. The reads were aligned to the A. japonica reference genome (GigaByte, 2024) using Bowtie2, and read counts were obtained. Raw data were processed, and differential gene expression analysis was performed using the DESeq2 package in R. Gene expression levels were normalized as transcripts per million (TPM), and differentially expressed genes were further analyzed using Gene Ontology (GO) enrichment analysis with the clusterProfiler package in R.
[Results]Transcriptomic analysis of the four stages of radula mineralization in A. japonica yielded over 450 million clean reads and 28,010 protein-coding genes annotated in five databases. PCA and correlation analysis showed distinct stage-specific clustering and high reproducibility. Differential gene expression analysis revealed sequential transcriptional shifts, with the most significant changes observed between the S1 vs. S4 comparison (2,294 DEGs) and the S1 vs. S2 comparison (1,524 DEGs). GO enrichment analysis revealed stage-specific functional shifts during radula mineralization. In the early stage (S1 vs. S2), genes upregulated in S1 compared with S2 were significantly enriched in extracellular space (CC), chitin binding (MF), and neuron differentiation (BP), suggesting active extracellular matrix formation and tissue differentiation processes. In contrast, genes upregulated in S2 were enriched in cation channel complex (CC), transmembrane transporter activity (MF), and transmembrane transport (BP), indicating a transition in ion transport regulation during early mineralization. In the S1 vs. S4 comparison, enriched GO terms included carbohydrate metabolic process (BP), chitin binding (MF), extracellular region (CC), transmembrane transport (BP), calcium ion binding (MF), and extracellular space (CC), indicating extensive matrix remodeling and dynamic regulation of ion transport during radula mineralization.
[Consideration]
[Conclusion]The results provide new insights into the molecular mechanisms underlying a coordinated radula mineralization process.
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