CRISPR/Cas9-mediated efficient and precise targeted integration of donor DNA harboring double cleavage sites in Xenopus tropicalis

Differential expression of foxo genes during embryonic development and in adult tissues of Xenopus tropicalis

The forkhead-box transcription factors of O subfamily (FOXO) play important roles in regulation of various biological functions. We cloned foxo1, foxo3, foxo4, and foxo6 from Xenopus tropicalis (hereafter X. tropicalis), and examined their expression in embryos and adult tissues. Maternal transcripts of foxo1 and foxo3 genes are detected within the animal half of the early embryo, their zygotic transcripts show distinct patterns. At late tailbud stages, foxo1 expression is observed mainly in eye, brain, branchial arches, and pronephros. In addition to eye, brain, branchial arches and pronephros, foxo3 expression is also evident in heart and somites. Foxo4 expression was not detected in oocytes. At late tailbud stages, foxo4 is mainly expressed in eye, brain, branchial arches and otic vesicle. Foxo6 expression was not detectable until stage 36, with a specific expression in nasal pits. Obvious expression of foxo1, foxo3 and foxo4, but not foxo6, is detected by RT-PCR both in oocytes and in embryos at examined stages. The expression of foxo1, foxo3 and foxo4 is observed in all tested adult tissues including heart, muscle, liver, lung, stomach and small intestine, while foxo6 is only detectable in stomach and small intestine. The differential expression pattern of foxo genes suggests that they exert distinct functions during embryonic development and in various organs of X. tropicalis.

Developmental expression patterns of fosl genes in Xenopus tropicalis

Fos-like antigens (Fosl) including Fosl1 and Fosl2 exclusively heterodimerize with Jun members to form AP-1 complex, thereby participating in various cellular progresses including cell cycle regulation. However, expression patterns of these two genes during embryonic development remains largely unknown. In the present study, both temporal and spatial expression patterns of fosl1 and fosl2 were examined during embryonic development of Xenopus tropicalis. Real-time quantitative PCR results showed that the expression of the two genes was increased from stage 2 to stage 42. However, expression level of fosl1 is much higher than that of fosl2 at stage 42. Whole-mount in situ hybridization showed that fosl1 was expressed in eyes, branchial arch, notochord, otic vesicle, and liver. However, fosl2 was expressed in lung primordium from stage 34 to stage 38, in addition to the moderate expression in eyes and branchial arch at stage 42. Thus, the developmental expression patterns of these two fosl genes is different in Xenopus embryos. These results provide a basis for further functional study of these two genes.