A Time-Course Transcriptomic Resource for Early Embryogenesis in Lethenteron reissneri

Continuous developmental transcriptomic data remain limited for jawless vertebrates. We generated an RNA-seq time series spanning 2 h post-fertilization (hpf; fertilization stage) to 10 days post-fertilization (dpf; hatching stage) in Lethenteron reissneri, with 14 developmental stages and three biological replicates per stage. We examined global expression patterns, differential expression between adjacent stages, functional enrichment, and stage-level co-expression, and assessed representative expression trends using reverse transcription quantitative PCR (RT-qPCR). Gene-expression profiles changed progressively across development. One notable interval was 2.5-3 dpf (late blastula to early gastrula), when upregulated genes were broadly enriched for germ-layer formation, axial patterning, neural development, and morphogenesis rather than the RNA-processing, ribosome-biogenesis, and translation terms prominent at earlier stages. Stage-level co-expression analysis identified a module enriched for development-related terms, and differential expression, functional annotation, and temporal profiles were used to compile a list of 154 candidate developmental genes. This study provides a continuous transcriptomic resource for early L. reissneri embryogenesis and a temporal framework for subsequent studies of lamprey development.