Functional Analysis of a Putatitive Cell Cycle Checkpoint Kinase 1 in Zebrafish Embryogenesis

As an initial approach to examine the function of cell cycle checkpoint kinase 1 (chk1) in embryonic development, a 1.461 Kb long cDNA encoding a zebrafish chk1 (Zchk1) was isolated from the 12-day-old zebrafish cDNA library. DNA sequences of the cDNA shares 87% homology with human chk1 (hchk1). However, the cDNA contains an incomplete open reading frame lacking approximately 100 bp at the 3′-end region. RT-PCR analysis showed that the level of Zchk1 mRNAs was present from 1 cell stage throughout the embryonic development. Whole mount in situ hybridization demonstrated that the mRNA persisted at low level through 50% epiboly, and became restricted in the anterior part of antero-posterior axis in 3 somites, and only in the tail region of primodia 11. Inhibition of the Zchk1 expression by microinjection of Zchk1 anti-sense RNA into 1-4 cell stage embryos caused retardation of embryonic development at late somite stage, which in turn resulted in dorsally rolled tail. Taken together, these results indicate that Zchk1 may be involved in the regulation of cell cycle during embryogenesis as well as in the formation of the dorsoventral axis in the posterior region.