Genetic Mouse Models for TRPM7 Research

MIP-Cre/ERT and Trpm7^tm1Clph (Trpm7^fl/fl) mice were obtained from The Jackson Laboratory. Trpm7tm1.1MkmaC56BL/6 (K1646R, Trpm7^R/R) mice were provided by Masayuki Matsushita (Okayama University Medical School, Okayama, Japan). Trpm7^fl/fl mice (60 (link)) and Trpm7^R/R mice (61 (link)) were reported previously. Mice were backcrossed to C57BL/6 (≥6 generations). Mice were housed in ventilated cages at the animal facility of the Walther Straub Institute of Pharmacology and Toxicology, LMU Munich, Munich, Germany. Trpm7^fl/fl and MIP-Cre/ERT mice were bred to obtain age- and sex-matched homozygous Trpm7^fl/fl MIP-Cre/ERT mice. To induce Cre activity in β cells of adult mice, 8-week-old male Trpm7^fl/fl MIP-Cre/ERT mice were injected i.p. with tamoxifen in corn oil (2 mg/d/mouse for 5 consecutive days). Negative controls were Trpm7^fl/fl MIP-Cre/ERT mice, which received just injections of corn oil. Heterozygous K1646R animals were bred to obtain age- and sex-matched homozygous WT and homozygous Trpm7^R/R mice. For genotyping, DNA was extracted from ear fragments using the Mouse Direct PCR Kit (Biotool). DNA samples were analyzed by PCR using a set of allele-specific oligonucleotides (Metabion). Sequence information is provided in Supplemental Table 2. Genotyping of Trpm7^fl/fl and Trpm7^R/R mice was performed as previously described (3 (link)). Inheritance of MIP-Cre/ERT transgene was determined by PCR using the following conditions: 94°C for 2 minutes followed by 94°C for 15 seconds, 60°C for 15 seconds, 72°C for 10 seconds, last 3 steps repeated for 30 cycles, and 72°C for 2 minutes.
Male and female mice were fed chow diet or diabetogenic diet (Research Diets, D12451), containing 45% kcal from fat, beginning at 8 weeks of age. Mice were single- or group-housed on a 12-hour light/12-hour dark cycle at 22°C with free access to food and water. Mice were maintained under these conditions for a maximum of 36 weeks.