Life cycle of Ciona intestinalis

Recent whole-genome studies and in-depth expressed sequence tag (EST) analyses have identified most of the developmentally relevant genes in the urochordate, Ciona intestinalis. In this study, we made use of a large-scale oligo-DNA microarray to further investigate and identify genes with specific or correlated expression profiles. This large-scale oligo-DNA microarray for C. intestinalis should facilitate the understanding of global gene expression and gene networks during the development and ageing of a basal chordate. Keywords: gene expression, development, ageing, life cycle We collected 15 test samples for the developmental stages, comprising fertilized eggs (FE), 2-cell, 4-cell, 8-cell, 16-cell, 32-cell, and 64-cell embryos, and early gastrulae (EG), late gastrulae (LG), early neurulae (EN), embryos at the initial tailbud (ITB), early tailbud (ETB), middle tailbud (MTB), late tailbud (LTB) stages, and larvae (LV). For the adult, we collected samples from 4 different stages, comprising juveniles (JN), 1.5 month-old (1.5M) adults, 2.5 month-old (2.5M) adults and 4.0 month-old (4.0M) adults. Juveniles were collected 2 weeks after metamorphosis. At that time, the juveniles have a small body size but most of the adult organs, except for the ovary and testis. Adults of 1.5M are pre-maturation stage; they do not yet have mature gonads. Adults of 2.5M are in the period of reproduction, and have mature gonads, eggs and sperm. Adults of 4.0M still have gonads but have lost their reproductive capacity. Two different RNA targets for microarray hybridization were used. Namely, for the developmental stages, RNA from fertilized eggs was used as a reference sample and RNA from the 14 stages of embryogenesis was used as test sample. In the adult stages, RNA combinations of adjacent stages were used, i.e. larvae vs. juveniles, juveniles vs. 1.5M adults, 1.5M vs. 2.5M adults, and 2.5M vs. 4.0M adults. In all of the RNA combinations, the hybridization was performed twice by reversing dyes (dye swap).