Laminins are key extracellular matrix proteins essential for embryonic development and maintenance of blood-brain barrier (BBB) integrity, but their cellular origins in vivo have remained difficult to resolve due to overlapping deposition by multiple cell types. Traditional antibody-based methods cannot distinguish which cells produce specific laminin isoforms, which has hindered comprehensive understanding of laminin biology.
Our researchers have developed a genetically engineered dual-fluorescent reporter mouse line enabling precise cell-specific and developmental stage-dependent visualization of laminin-γ1 expression. This dual-color knock-in model incorporates a loxP-mCherry-polyA-loxP-eGFP cassette into exon 28 of the laminin-γ1 gene, enabling precise visualization of laminin expression. When crossed with the endothelium-specific Cdh5-CreER mouse line, the Laminin-mCherry/eGFP reporter mouse enables precise labeling of laminin-γ1 produced specifically by endothelial cells. Upon tamoxifen administration, Cre recombinase activates recombination in endothelial cells, switching the fluorescent tag from mCherry to eGFP. This allows researchers to distinguish endothelial-derived laminin from laminin produced by other cell types, as both signals co-localize with endogenous laminin-γ1 staining in brain tissue. The model thus provides a powerful tool for dissecting the cellular contributions to laminin deposition in vivo, with high spatial and temporal resolution. This model provides the first tool for real-time imaging of laminin-γ1, allowing for the dissection of its specific roles in various developmental and disease contexts.