Temporal and Molecular Characteristics of Mutations Induced by Ethylnitrosourea in Germ Cells Isolated from Seminiferous Tubules and in Spermatozoa of lacZ Transgenic Mice

• Published in: Proceedings of the National Academy of Sciences - PNAS 1995-08, Vol.92 (16), p.7485-7489
• Main Authors: Douglas, George R., Jiao, Jianli, Gingerich, John D., Gossen, Jan A., Soper, Lynda M.
• Format: Article
• Language: English
• Subjects: Adducts; Animals; Base Composition; Base Sequence; DNA; DNA - chemistry; DNA - drug effects; DNA - genetics; Ethylnitrosourea - toxicity; Genetic mutation; Genetics; Germ cells; Lac Operon; Male; Mice; Mice, Transgenic; Molecular Sequence Data; Mutagenesis; Mutation; Point Mutation; Reproductive system; Rodents; Seminiferous tubules; Seminiferous Tubules - cytology; Spermatozoa; Spermatozoa - drug effects; Spermatozoa - metabolism; Stem cells; Time Factors; Transgenic animals; Vas deferens; Vas Deferens - cytology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.92.16.7485

The lacZ transgenic mouse (Muta mouse) model was used to examine the timing of ethylnitrosourea (ENU)-induced mutations in germ cells. The spectrum of mutations was also determined. Animals received five daily treatments with ENU at 50 mg/kg and were sampled at times up to 55 days after treatment. In mixed germ-cell populations isolated from seminiferous tubules, there was little increase in the mutant frequency 5 days after treatment; subsequently, there was a continuous increase until the maximum (17.5-fold above background) was reached by ≈35 days. In the spermatozoa, an increase in mutant frequency was not seen until 20 days after treatment, with the maximum (4.3-fold above background) being achieved no sooner than ≈35 days. Based on the timing of sampling, these data demonstrate the detection of both spermatogonial and postspermatogonial mutations. The most prominent feature of the ENU-induced basepair mutations in testicular germ cells sampled 55 days after treatment is that 70% are induced in A·T base pairs, compared to only 16% in spontaneous mutations. These findings are consistent with comparable data from ENU studies using assays for inherited germ-cell mutations in mice. This study has demonstrated the utility and potential of the transgenic mouse lacZ model (Muta mouse) for the detection and study of germ-cell mutations and provides guidance in the selection of simplified treatment and sampling protocols.