Genetic Manipulation of Ret in Mice

Ret^flox-V805A (The Jackson Laboratory, 028548) female and male mice were bred for timed pregnancy. To inhibit Ret tyrosine kinase activity, pregnant female mice were injected i.p. with NA-PP1 (Medchem express, HY-13941/CS-1804) or vehicle (cremaphor/saline/ethanol in 1:7:2 ratio) from E16.5 through E18.5 at the dose of 32.25 mg/kg, 50 mg/kg, and 62.5 mg/kg, respectively. Pups delivered spontaneously E19.5. NA-PP1 was prepared using published methods (37 (link)). Both male and female offspring were used for experiments. To delete Ret in the UB, Tet-O-Cre (103 (link)) and Hoxb7rtTA (The Jackson Laboratory, 036718) mice were crossed into Ret^flox-V805A mice. Tet-O-Cre;Hoxb7rtTA;Ret^flox-V805A mice were bred for timed pregnancy. Pregnant females were given Dox (Henry Schein, 1315046; 2 mg/mL) dissolved in drinking water beginning E15.5, E16.5, or E17.5 through delivery. Several breeders were heterozygous for Hoxb7rtTA and yielded littermate controls without Ret deletion (Tet-O-Cre; Ret^flox-V805A). Offspring were genotyped through Transnetyx core service. Pups with the genotype of Tet-O-Cre;Hoxb7rtTA;Ret Ret^flox-V805A who were exposed to Dox in utero with resultant Ret deletion in the UB were named Ret^UBdel.