Study of Mid-Blastula Transition of zebrafish embryos

Sox31 is a member of the zebrafish SoxB1 subfamily, and its expression can be detected both pre- and post-MBT. To distinguish the function of its maternal and zygotic transcripts, a splice blocking morpholino (Sb MO) was designed to interfere with the processing of new, zygotically synthesised mRNAs without interfering with mRNAs of maternal origin. Developmental arrest was observed in Sb MO which could not bypass MBT. Mid-Blastula Transition (MBT) functions as a time window for zygotic genome activation and maternal mRNA degradation. To uncover whether the “zygotic up” and “maternal down” event during MBT is retarded in Sb morphants, we performed microarray experiment at the end of MBT (about 4.3 hours post fertilication/4.3 hpf) to compare mRNAs from Sb morphants and control embryos. In one experiment, three flocks of zebrafish eggs were injected with the Sox19b morpholino immediately after fertilization, while another three control populations were injected with placebo. At 4.3 hpf, these six flocks of embryos were sent for gene expression profiling with six Affymetrix Zebrafish Genome Arrays. In another experiment, we compared two wildtype embryo samples at 4h (post-MBT) against two wildtype samples at 2.5 h (pre-MBT).