Electrophoretically detected germinal mutations induced in the mouse by ethylnitrosourea.

Abstract

Male DBA/2J and C57BL/6J mice were treated with ethylnitrosourea (EtNU) at a dose of 250 mg/kg of body weight. After a sterile period of 11 weeks, the treated animals were mated with untreated females; treated DBA with C57 and treated C57 with DBA. A small control group of untreated males was established, and a larger control group from earlier experiments was also used for comparison Electrophoretic analysis has demonstrated genetic alterations in a wide variety of organisms, and the approach is currently being used to screen for mutations in human populations (6, 7). This paper presents the results of the application of the electrophoretic approach to the detection ofgerminal mutations induced by EtNU. MATERIALS AND METHODSThe two strains of mice used-C57BL/6J and DBA/2J-were purchased from The Jackson Laboratory. Seventy DBA male mice were injected with a solution of EtNU and subsequently mated with C57 females. Likewise, 70 C57 males were injected and mated with DBA females. Only one death occurred among the treated males following treatment. A small control series, 10 animals from each strain, were injected with buffer only and mated in the same way. Additional control data were obtained from previous experiments (8, 9).The EtNU was obtained from Bio-Clinical Laboratories (Bohemia, NY). Before injection, it was dissolved in 0.05 M sodium phosphate buffer (pH 4.0) at 25 mg/ml. The solution, volume adjusted to deliver a dose of 250 mg/kg of body weight, was administered by intraperitoneal injection. All injections were completedwithin 10 min ofpreparation ofthe solution. Controls received only buffer. The first trial matings were attempted 5 or 6 weeks after injection; when the sterile period ended (10.5 + 1.0 weeks after injection), a regular schedule of mating was established according to which the males were each placed with a pair of females in mating cages for 1 week. At the end of that time, each male was placed with a different pair offemales. The schedule was maintained for several months to produce F1 animals. The offspring were weaned at m24 days of age and used for electrophoretic analysis when =-8-10 weeks old.The sample material for electrophoretic studies consisted of erythrocyte lysates and kidney homogenates. The samples were obtained surgically, so the animals were alive and available for mating to determine heritability ofthe detected variations. The parent animals and all of their F1 progeny were examined by the same set of techniques. Methods for sample preparation, electrophoresis, and gel staining have been described (8). The techniques allow genetic variation to be detected at 21 loci, which are of two types.For one set of 10 loci, there are electrophoretic differences between the strains determined by alternative homozygous alleles in the two strains. These loci are Mod-i, Es-i, Es-3, Idh-1, Hbb, Pep-3, Gpd-i, Gpi-i, Pgm-i, and Pgm-3. Loci of this type are especially useful because they make it possible to tell from which parent a newly arisen mutational event originated.The ot...

Recovery of induced mutations for X chromosome-linked muscular dystrophy in mice.

“…Moreover, since ENU has been most frequently associated with point mutations rather than deletions or chromosomal rearrangements, it will be fruitful to ask whether the induced mutations identify similar mutational effects at the molecular level or whether dystrophin gene function is impaired differently in each mutant. The recovery of three more mutant alleles among 1600 progeny is relatively high compared with ENUinduced mutations recovered for other loci (8,11). However, this frequency may be a reflection of the relatively large size of the dystrophin locus and its 14-kilobase transcript.…”

“…Male mice treated with one intraperitoneal dose of ENU transmit germ-line mutations to progeny at a frequency as high as 1 mutation per 700 loci tested (8)(9)(10)(11). In this report, we describe the results of our use of ENU to produce muscular dystrophy mutations in mice.…”

N-ethyl-N-nitrosourea-induced null mutation at the mouse Car-2 locus: an animal model for human carbonic anhydrase II deficiency syndrome.

“…Blood and kidney samples from the (C57BL/6J x DBA/2J)F1 progeny were screened for variations at 32 loci by starch gel electrophoresis and broad-range isoelectric focusing, as described elsewhere (18,19). CA II in F1 animals appears as two bands (i.e., CA Ila and CA Ilb) on the broad-range focusing gels.…”

History of the science of mutagenesis from a personal perspective

“…It was fortunate that Bill Russell had just found that ENU was an extremely potent chemical mutagen in spermatogonia [Russell et al, 1979]. Frank Johnson and Susan Lewis started experiments at RTI to study the mutagenicity of ENU in the BSLMS [Johnson and Lewis, 1981;Lewis et al, 1985]. They were successful, and several papers resulted from their work [Johnson and Lewis, 1981;Popp et al, 1983].…”