Visualization of basement membranes by a nidogen-based fluorescent reporter in mice

Col4a2-eGFPmouse model reveals the molecular and functional dynamics of basement membrane remodelling in hair follicle morphogenesis

“…In this mouse model, crossing heterozygous mice produces homozygous mice only 1% of the time, and they exhibit syndactyly and testis dysplasia. Another mouse line, expressing mCherry-tagged human nidogen-1 under the Rosa26-CAG promoter, has been generated and used to label BMs, but unclear BM signals and non-BM-like signals were also observed in several tissues 20 . These studies underscore the difficulties in generating mice that express fluorescently tagged, functionally normal BM proteins.…”

“…These properties include 1) large modular structures, 2) specialized intracellular transport and secretory mechanisms, 3) post-translational processing, 4) the assembly of supramolecular complexes, 5) complex molecular interactions and 6) unique extracellular physicochemical environments, such as redox status. While a few individuals of C. elegans and Drosophila have been manipulated to express fluorescently tagged endogenous BM proteins with normal functions 14,18 , mice expressing fluorescent tag-fused core BM proteins have exhibited functional abnormalities [19][20][21] . Therefore, generating mice that express endogenous core BM proteins fused with a fluorescent tag while maintaining normal function remains a major challenge.…”

An mTurq2-Col4a1 mouse model allows for live visualization of mammalian basement membrane development

“…However, until recently, the key bottleneck in our understanding of mammalian, and indeed vertebrate BMs, has been the lack of models in which endogenous BM components are labeled. Several attempts to generate such models have been unsuccessful ( Shaw et al, 2020 ), and in vivo studies have relied upon knock-in reporters, which do not necessarily reflect endogenous protein expression and can be expressed ectopically and/or interfere with native protein function ( Yamaguchi et al, 2022 ; Sztal et al, 2011 ; Futaki et al, 2023 ). The recent success by Morgner et al (2023) in generating a Lamb1-Dendra2 mouse model provided a proof-of-principle that fluorescently tagging BM components in mice is feasible, and in this study, we have advanced one step further by generating a mouse line in which the BM ubiquitous COL4A1 is labeled.…”

“…Several attempts to visualize the vertebrate BM in vivo have been made, for example, the lamC1:lamC1-sfGFP zebrafish line recapitulates the reported mRNA expression pattern of endogenous lamC1 , but the tag itself is not inserted into the endogenous genomic locus and the fusion protein is expressed as an additional copy ( Yamaguchi et al, 2022 ; Sztal et al, 2011 ). Similarly, Futaki et al (2023) have generated a R26-CAG-Nid1-mCherry mouse line in which the BM can be visualized in vivo; however, again this tag is not inserted in the endogenous locus; the fusion protein is expressed from a ubiquitous promoter that drives ectopic expression of Nid1-mCherry and causes reduced localization of endogenous Nid1. More recently, Morgner et al (2023) generated an endogenous Lamb1-Dendra2 mouse model in which heterozygous animals have fluorescently labeled laminin β-1-containing BMs, which enabled tumor-cell mediated BM turnover to be measured using intravital microscopy.…”