MOLECULAR CLONING AND EXPRESSION PATTERN OF ZAR1 AND ZAR1L IN THE ZEBRAFISH

Maternal mRNAs, which are expressed in oocytes, play an important role in the success of early embryonicdevelopment. Zygote arrest 1 (Zar1) and Zar1-like (Zar1L) are the oocyte-specific maternal genes that function at theoocyte-to-embryo transition in mouse. Zar1 and Zar1L are conserved in evolution, but the expression patterns of Zar1and Zar1L are diverse in animal kingdom. In this experiment, the full length of Zar1L cDNA was cloned from the zebrafishovary by RACE. The expression patterns of Zar1 and Zar1L in different tissues, developing oocytes and embryogenesiswere checked by RT-PCR. The full-length cDNA of Zar1L was 1146 bp, which comprised a 20 bp 5′ untranslatedregion (UTR), a 190 bp 3′-UTR; a 936 bp open reading frame (ORF) encoding a 311 amino acids peptide.Structurally, the Zar1L protein contained an atypical PHD motif (plant homeo domain) and two C4 type zinc finger inthe C-terminal, and showed 74% homology to known counterparts from mammals and birds. In gene structure, Zar1 andZar1L had four exons, each of the two genes exons were relatively similar in size. It showed that zebrafish Zar1 andZar1L gene belonged to two different genes, and it might be the ancestors of the same source gene duplication andevolution. Zar1 and Zar1L were expressed at a similar pattern, and both of them were ovary specific. The expressions ofZar1 and Zar1L did not change during oogenesis. Both Zar1 and Zar1L mRNA were maternal deposited, and the expressionlevels of both genes were high in the early embryos till gastrulation. A significant decrease of Zar1L occurredat gastrula, while Zar1 decreased apparently at neurula. However, both Zar1 and Zar1L were expressed in the wholeprocess of embryonic development till hatching. The consistency expression level of Zebrafish Zar1 and Zar1L impliedthat the function of the two genes were basically the same. The results suggested that Zar1 and Zar1L were maternalfactors for mid-blastula transition, and Zar1 and Zar1L might have other important roles during embryonic development.