Functional characterization of Lmo2-Cre transgenic zebrafish.

Cre/loxP system is a powerful tool to manipulate the genome. Transgenic animals expressing Cre recombinase in specific tissues or cells have been widely used for conditional gene targeting, lineage tracing, and other genetic analyses. In zebrafish, the transgenic line with stable expression of Cre in specific tissues and cell subtypes has not been generated and its functional activity remains to be defined. Here we report the establishment of a stable transgenic fish Tg(zlmo2:Cre), which specifically expresses Cre in the primitive hematopoietic progenitors and vascular endothelial cells, under the control of lmo2 promoter. Our result shows that the Cre expression pattern recapitulates the endogenous lmo2 expression pattern during embryogenesis. Crossing of the Tg(zlmo2:Cre) line with another established transgenic reporter line Tg(zlmo2:loxP-DsRed-loxP-EGFP), induces a robust recombination activity in hematopoietic progenitors and vascular endothelial cells. Thus, the Tg(zlmo2:Cre) transgenic line provides an invaluable tool to dissect genetic pathways in hematopoietic development and diseases.

Wang L ，Zhang Y ，Zhou T ，Fu YF ，Du TT ，Jin Y ，Chen Y ，Ren CG ，Peng XL ，Deng M ，Liu TX ... -  《DEVELOPMENTAL DYNAMICS》

Regulation of the lmo2 promoter during hematopoietic and vascular development in zebrafish.

Zhu H ，Traver D ，Davidson AJ ，Dibiase A ，Thisse C ，Thisse B ，Nimer S ，Zon LI ... -  《DEVELOPMENTAL BIOLOGY》

Generation of oocyte-specifically expressed cre transgenic zebrafish for female germline excision of loxP-flanked transgene.

In this communication, we report the generation of a cre transgenic zebrafish line under an oocyte-specific promoter, zp3. The transgenic line Tg(zp3:cre; krt8:rfp) also contains a co-integrated rfp transgene under the skin epithelial promoter krt8 to allow selection of cre transgenic fish based on RFP fluorescence in the skin. We demonstrated in this transgenic line that cre mRNA was specifically expressed in growing oocytes like endogenous zp3 mRNA. When Tg(zp3:cre; krt8:rfp) was crossed with a loxP transgenic line, the floxed DNA was specifically eliminated from female, but not male, germline. Tg(zp3:cre; krt8:rfp) fish also have maternal cre mRNA in early embryos to cause Cre-mediated recombination; this feature can be used to activate other loxP transgenic lines in early embryos. Furthermore, after crossing with another loxP transgenic line, Tg(EF:loxP-mCherry-loxP-egfp), we confirmed that our cre line was capable of activating a loxP-blocked EGFP reporter gene by both maternal and oocyte-expressed Cre.

Liu X ，Li Z ，Emelyanov A ，Parinov S ，Gong Z ... -  《DEVELOPMENTAL DYNAMICS》

The 5' zebrafish scl promoter targets transcription to the brain, spinal cord, and hematopoietic and endothelial progenitors.

The stem cell leukemia (SCL) gene encodes a basic helix-loop-helix transcription factor and is essential for embryonic angiogenesis, hematopoietic stem cell specification, and erythrocyte maturation. Here, we report the isolation and characterization of the zebrafish scl promoter. We show that a 5-kilobase (kb) genomic fragment immediately upstream of the translation start site is capable of targeting the enhanced green fluorescence protein (EGFP) expression to the anterior and posterior lateral mesoderm where the endogenous scl normally expresses. Detailed analysis of the stable transgenic fish reveals that this 5-kb upstream sequence is sufficient to direct the EGFP transcription to the brain, spinal cord, and hematopoietic-endothelial progenitors, possibly the hemangioblast, but not primitive erythrocyte, suggesting that the zebrafish scl transcription in hematopoietic-endothelial progenitors and erythrocyte is regulated by distinct cis element(s). Our study has defined the cis regulatory element(s) for zebrafish scl expression in the brain, spinal cord, and hematopoietic-endothelial progenitors and established a valuable transgenic line Tg(5'5kbscl:EGFP) for studying hematopoietic lineage development.

Jin H ，Xu J ，Qian F ，Du L ，Tan CY ，Lin Z ，Peng J ，Wen Z ... -  《DEVELOPMENTAL DYNAMICS》

Zebrafish scl functions independently in hematopoietic and endothelial development.

Dooley KA ，Davidson AJ ，Zon LI 《DEVELOPMENTAL BIOLOGY》