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Updated: Jul 23, 2025
Zygote Microinjection for Creating Gene Cassette Knock-in and Flox Alleles in Mice
Published on: June 24, 2022
Generation and characterization of a Dkk4-Cre knock-in mouse line
Houda Khatif1,2,3, Hisham Bazzi1,2,3
1Department of Dermatology and Venereology, University Hospital of Cologne, University of Cologne, Cologne, Germany.
Abstract:
Ectodermal appendages in mammals, such as teeth, mammary glands, sweat glands and hair follicles, are generated during embryogenesis through a series of mesenchymal-epithelial interactions. Canonical Wnt signaling and its inhibitors are implicated in the early steps of ectodermal appendage development and patterning. To study the activation dynamics of the Wnt target and inhibitor Dickkopf4 (Dkk4) in ectodermal appendages, we used CRSIPR/Cas9 to generate a Dkk4-Cre knock-in mouse (Mus musculus) line, where the Cre recombinase cDNA replaces the expression of endogenous Dkk4. Using Cre reporters, the Dkk4-Cre activity was evident at the prospective sites of ectodermal appendages, overlapping with the Dkk4 mRNA expression. Unexpectedly, a predominantly mesenchymal cell population in the embryo posterior also showed Dkk4-Cre activity. Lineage-tracing suggested that these cells are likely derived from a few Dkk4-Cre-expressing cells in the epiblast at early gastrulation. Finally, our analyses of Dkk4-Cre-expressing cells in developing hair follicle epithelial placodes revealed intra- and inter-placodal cellular heterogeneity, supporting emerging data on the positional and transcriptional cellular variability in placodes. Collectively, we propose the new Dkk4-Cre knock-in mouse line as a suitable model to study Wnt and DKK4 inhibitor dynamics in early mouse development and ectodermal appendage morphogenesis.
Insights
Researchers developed a new Dkk4-Cre mouse model to track Wnt signaling dynamics during mammalian ectodermal appendage development. This model reveals Dkk4 activity in developing appendages and unexpected mesenchymal cells, offering insights into developmental processes.
Area of Science:
- Developmental Biology
- Genetics
- Mammalian Embryogenesis
Background:
- Ectodermal appendages (teeth, hair, glands) develop via mesenchymal-epithelial interactions.
- Wnt signaling and its inhibitors are crucial for early ectodermal development and patterning.
Purpose of the Study:
- To investigate the dynamic activation of Dickkopf4 (Dkk4), a Wnt inhibitor, in ectodermal appendages.
- To establish a novel genetic tool for studying Wnt signaling in early development.
Main Methods:
- Generated a Dkk4-Cre knock-in mouse line using CRISPR/Cas9 technology.
- Utilized Cre reporter systems to visualize Dkk4 expression patterns.
- Performed lineage tracing to identify cell origins.
Main Results:
- Dkk4-Cre activity was observed at prospective ectodermal appendage sites, correlating with Dkk4 mRNA expression.
- Unexpected Dkk4-Cre activity was detected in posterior embryonic mesenchymal cells, originating from early epiblast cells.
- Analysis of hair follicle placodes revealed cellular heterogeneity within and between placodes.
Conclusions:
- The Dkk4-Cre mouse line is a valuable model for studying Wnt and Dkk4 inhibitor dynamics in mouse embryogenesis.
- The findings highlight Dkk4's role in ectodermal appendage development and uncover its expression in previously unrecognized mesenchymal populations.
- The study provides insights into cellular heterogeneity within developing ectodermal structures.
