Fig. 1

Identification of promoter region for inducing germ cell-specific gene expression in the chicken vasa homologue (CVH) promoter through 5′ deletion assays. a Schematic diagram of the constructed enhanced green fluorescent protein (eGFP) expression vectors with CVH promoters of different sizes. By 5′ deletion assays, six constructs including differently sized 5′ flanking sequences containing the 5′ untranslated region (UTR) were randomly designed. eGFP expression vector of a 250-bp fragment of the CVH promoter containing only the 5′ UTR. b Twenty-four hours after transfection, the expression of eGFP under the control of the differently sized promoters in cultured chicken primordial germ cells (PGCs) was monitored by microscopy. Each fragment used for driving eGFP expression was ligated into the NanoLuc luciferase expression vector (pNL1.2-Basic) to measure promoter activity. Dual luciferase assay of CVH promoter activity in PGCs (c) and DF-1 (d). NanoLuc luciferase expression levels were normalized to the luciferase activity of internal firefly control and are expressed as relative luciferase units. Scale bar = 100 μm. Different letters (a–e) indicate significant differences (P < 0.05)