Expression And Function Of A Human Heart Developmental Candidate Gene FBL5

Cardiovascular diseases have become one of the most serious diseases that threaten human beings. It is a critical prerequisite to understand the normal progress of cardiovascular development and the mechanisms underlying the causes of this kind of diseases.In previous work, we performed yeast two-hybrid screen and obtained FBL5 as a binding partner of FoxP4. FBL5 belongs to F-box protein family.This protein family constitute one of the four subunits of ubiquitin protein ligase complex called SCFs (SKP-cullin-F-box), which governs ubiquitin-proteasome pathway. Recent study showed that ubiquitin-proteasome pathway is related to cardiovascular diseases.In order to promote our understanding the expression and function of FBL5, the full-length cDNA was isolated from a human brain cDNA library. Using immunofluorescence staining, FBL5 alone distributes in the cytoplasm and still distributes in the cytoplasm when FoxP4 was coexpressed in COS-7 cells.Luciferase assay showed that FBL5 is a transcriptional inhibitor,and can inhibit the regulation activity of SRFUsing bioinformatics we found the zebrafish homologous gene of FBL5. A fragment of FBL5 was amplified by the PCR and inserted into pGEM-T. Antisense digoxigenin-labeled riboprobe was prepared using this construct. Whole-mount in situ hybridization revealed FBL5 expression in the heart, the brain and the bones. Injection of zebrafish embryos with a morpholino directed against FBL5 resulted in embryos with a notochord and an unlooped heart tube. The in situ hybridization assay used embryos injected with FBL5-MO or FoxP4-MO at 48hpf, showed that FBL5 expression decreased in FBL5-MO and FoxP4-MO samples. Conclusion, FBL5 have important function in the zebrafish heart development.