Meox2 cre

Adult mice of both sexes were used. For compatibility with other projects in the laboratory, the PV-Cre (Jackson 017320) and DAT-Cre (Jackson 006660) used were also heterozygous for the FLP-dependent tdTomato reporter line Ai65F (Daigle et al., 2018 (link)); obtained in this case by crossing the Cre− and FLP-dependent tdTomato double-reporter line Ai65D (Madisen et al., 2015 (link); Jackson Laboratory 021875) to the Cre deleter line Meox2-Cre (Tallquist and Soriano, 2000 (link); Jackson Laboratory 003755), then breeding out the Meox2-Cre allele, resulting in a reporter line for which only FLP is required for expression of tdTomato). For those mice in which RVΔG-4FLPo was used, the reporter allele was necessary for reporting RV activity; for those in which RVΔG-4mCherry was used, the presence of this reporter allele was irrelevant. For Cre-negative control injections using RVΔG-4FLPo, the Ai65F line was used. For Cre-negative control injections using RVΔG-4mCherry, either Ai65F or the Cre-dependent reporter line Ai14 (Madisen et al., 2010 (link)) was used; in these cases, the presence of the reporter alleles was again irrelevant.

Daam1^Floxand Daam2^LacZ mice were reported previously [53 (link)]. Daam1^FloxNeo/+heterozygotes were crossed with ACTB-flpe to remove the PGK-neo cassette. The resultant Daam1^Flox/+ mice were crossed with ACTB-cre to generate the Daam1 mutant allele (Daam1^Δ/+). The Daam1 mutant allele with PGK-neo cassette (Daam1^ΔNeo/+) was generated by Daam1^FloxNeo/+ heterozygotes crossed with ACTB-cre to remove the Exon6.
Vangl2^Lp/+, ACT-flpe and Meox2-Cre mice were purchased from Jackson Labs. C57BL6 (Ly5.1 and Ly5.2) mice were provided by Charles River Laboratories. The Wnt5a knockout [54 (link)] and ACNB-cre [55 (link)] mice were obtained from the originating labs.
This study was carried out in compliance with the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. The protocol was approved by Frederick National Lab Animal Care and Use Committee (Proposal #17–408). Rodents were euthanized by CO₂ inhalation in accordance with the most recent AVMA Guidelines on Euthanasia. For the harvesting of viable embryonic tissue, the embryos were harvested, placed in cold PBS, cooled down on ice and decapitated before harvesting of fetal livers.