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J Favor

Publications and source records attributed to J Favor.

At least 37 records · Page 2Linked to original sources
PubMed1998

Induction of specific-locus and dominant lethal mutations in male mice by ifosfamide (Holoxan).

Ifosfamide induced dominant lethal mutations in spermatozoa of mice at doses of 200 and 300 mg/kg and in spermatids and spermatocytes at 600 mg/kg. The highest dose also induced specific-locus mutations in post-spermatogonial germ-cell stages of mice but not in spermatogonial stem cells. The nature of the induced mutations suggests they are intergenic. The spermatogenic specificity of ifosfamide in mouse germ cells is similar to that of the structurally related cytostatic drugs cyclophosphamide and trofosfamide. Due to the post-spermatogonial germ cell specificity of ifosfamide, the genetic risk is limited to a few weeks after exposure.

Animals↗
PubMed1998

Loss of heterozygosity at the dilute-short ear (Myo5a-Bmp5) region of the mouse: mitotic recombination or double non-disjunction?

The occurrence of homozygous-viable dilute-short ear (Myo5a-Bmp5) double mutants in mouse specific locus mutation experiments has generally been assumed to be the result of double non-disjunction such that the mutant inherits two copies of chromosome 9 carrying the recessive alleles from the test-stock. A homozygous viable Myo5a-Bmp5 double mutant was recovered recently in our laboratory. We were able to genetically analyse both the Myo5a-Bmp5 region and proximal and distal markers in the original mutant as well as in offspring of the original mutant. Our results indicate the mutational event to be due to mitotic recombination and not double non-disjunction.

Alleles↗
PubMed1998

A mutation in the connexin 50 (Cx50) gene is a candidate for the No2 mouse cataract.

PURPOSE: The No2 cataractous mouse mutant displays a bilateral, congenital, hereditary nuclear opacity of the ocular lens. The aim of this work was to identify and subsequently screen an optimal candidate gene for a mutation correlated and consistent with the observed phenotype. METHODS: The No2 cataract was mapped in relation to genes and microsatellite markers by crossing to the wild mouse strain Mus spretus and then backcrossing to the inbred strain C3H/ HeH. The Cx50 (MP70) protein coding region and flanking sequences were amplified from normal parental as well as heterozygous and homozygous mutant genomic DNAs. These PCR products were then sequenced directly. Sequence data was corroborated by restriction analysis of PCR products. RESULTS: Mapping of the No2 cataract placed it in the vicinity of Gja8, the gene encoding connexin 50 (MP70), a major component of lens fiber gap junctions. Amplification and subsequent sequencing of the Cx50 protein coding regions revealed a single A-->C transversion within codon 47. This sequence change resulted in the creation of an HhaI restriction endonuclease restriction site, allowing for corroboration of the sequence data via restriction analysis using this enzyme. The sequence alteration is also predicted to result in the nonconservative substitution of alanine (Ala) for the normally encoded aspartic acid (Asp) at this position within the polypeptide. CONCLUSIONS: The identified mutation in Gja8 is both correlated and consistent with the cataract observed in the No2 mouse mutant, making it an ideal candidate for the cataract. This study provides the first evidence that a mutation in a lens connexin can result in congenital hereditary cataract, highlighting the importance of lens connexins in maintaining lens transparency.

Animals↗
PubMed1998

The DNA damaging drug cyproterone acetate causes gene mutations and induces glutathione-S-transferase P in the liver of female Big Blue transgenic F344 rats.

The gestagenic and antiandrogenic drug cyproterone acetate (CPA) is mitogenic, tumorigenic and induces DNA-adducts and DNA-repair synthesis in rat liver. Thus CPA is expected to be mutagenic. However in vitro mutagenicity test systems were negative. To examine whether CPA induces mutations in rat liver, the in vivo mutation assay based on Big Blue transgenic F344 rats was employed. Single oral doses of 25, 50, 75, 100 and 200 mg CPA/kg b.w. respectively were administered to female Big Blue rats. Six weeks after treatment, liver DNA was assayed for mutations. At the highest dose, 200 mg CPA/kg b.w., the frequency of (17 +/- 4) x 10(-6) spontaneous mutations was increased to a maximum of (80 +/- 8) x 10(-6) mutations. One-hundred and 75 mg CPA/kg b.w. resulted in mutation frequencies of (35 +/- 5) and (27 +/- 5) x 10(-6), respectively. The mutation frequency at doses of 50 and 25 mg CPA/kg b.w. was similar to that of vehicle treated controls. Statistical analysis of the dose-effect relationship revealed that it was not possible to decide whether a threshold dose exists or not. DNA adducts were analyzed by the 32P-postlabelling technique. The total level of the major and the two minor adducts observed in the autoradiograms increased between doses of 25 to 75 mg CPA/kg b.w. to a maximum of approximately 12,000 +/- 3000 adducts per 10(9) nucleotides. The level did not further increase significantly with 100 and 200 mg CPA/kg b.w. After CPA treatment no preneoplastic liver foci were observed. However, single glutathione-S-transferase placental form (GST-P) positive hepatocytes were observed and the frequency was dependent on the dose. These cells are not supposed to represent initiated cells, since they occurred only transiently after 6 weeks and disappeared thereafter completely. In conclusion, our results demonstrate that CPA is mutagenic in vivo. The mutation frequency increased at high CPA doses, when the increase of the DNA adduct formation had already ceased. This suggests that the mitogenic activity of CPA is required to express the mutations.

Animals↗
PubMed1998

Abnormal eye development associated with Cat4a, a dominant mouse cataract mutation on chromosome 8.

PURPOSE: Cat4a, one of four mutant alleles at the mouse Cat4 locus, causes central corneal opacity and anterior polar cataract in heterozygotes and microphthalmia in homozygotes. The Cat4 locus has been mapped to chromosome 8, 31 cM from the centromere. In this study ocular development of Cat4a mutant mice was investigated to characterize the defects in eye morphogenesis. METHODS: Serial sections from eyes of wild-type, heterozygous, and homozygous littermates were examined by means of light microscopy at selected intervals from embryonic day 11 to postnatal day 1. Eyes of adult heterozygous and homozygous mice also were evaluated histologically. RESULTS: Failure of separation of the lens vesicle from the surface ectoderm was the earliest structural defect observed. In heterozygous embryos, the abnormality was limited to persistent connection of the anterior pole of the lens to the cornea. Adult heterozygotes had defects in the central corneal stroma and endothelium and anterior polar cataracts with or without keratolenticular adhesion. In homozygous embryos, the persistent connection of lens to surface ectoderm was associated with aborted lens development, failure of closure of the optic fissure, and impairment of growth of the eyecup. Microphthalmic eyes of adult homozygous mice had a poorly developed cornea, and the anterior chamber and vitreous compartment were absent. An extensively folded retina and remnants of a degenerated lens filled the interior of the globe. CONCLUSIONS: A developmental defect inhibits separation of the lens vesicle from surface ectoderm in mice heterozygous or homozygous for the Cat4a mutation. In homozygotes subsequent lens and eye morphogenesis are also severely affected. Cat4a shows phenotypical similarity to several other independent mouse mutations including Small eye, a mutation of the Pax6 gene. Cat4 may be one of several genes involved in a common developmental path and may be part of the Pax6-regulated gene cascade governing eye morphogenesis.

Abnormalities, Multiple↗
PubMed1997

Induction of specific-locus and dominant lethal mutations in male mice by 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU).

1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) induced dominant lethal and specific-locus mutations in male mice. For both compounds the germ cell stage sensitive to the induction of dominant lethal mutations was dose dependent. A dose of 5 mg BCNU per kg b.wt. induced dominant lethal mutations primarily in spermatocytes, whereas higher doses of BCNU induced dominant lethals in spermatids and spermatocytes. Following doses of 5 and 10 mg CCNU per kg b.wt. dominant lethals were induced in spermatids and spermatocytes similar to the results for higher doses of BCNU. Higher dose exposure to BCNU and CCNU was associated with dominant lethals expressed as pre-implantation loss (reduction in total number of implants). In addition, higher doses of CCNU showed a cytotoxic effect in differentiating spermatogonia. Both compounds induced specific-locus mutations in post-spermatogonial germ cell stages of mice. However, CCNU increased also the specific-locus mutation frequency in spermatogonia in two out of three experiments. We conclude in analogy with criteria developed by IARC, that BCNU and CCNU are potential human mutagens.

Animals↗
PubMed1997

Identification of a mutation in the MP19 gene, Lim2, in the cataractous mouse mutant To3.

PURPOSE: Lim2, the gene encoding the second most abundant lens specific integral membrane protein, MP19, has recently been proposed as an ideal candidate gene for the cataractous mouse mutant, To3. The aim of this study was to screen the Lim2 gene in the To3 mutant for a genetic lesion that was correlated and consistent with the mutant phenotype. METHODS: Genomic DNA was isolated from both normal mouse parental strains as well as the heterozygous and homozygous To3 cataract mutant. PCR was used to generate overlapping fragments of the entire Lim2 gene from these DNAs. The coding regions, including splice junctions and the translational termination site, of these fragments were then sequenced. RESULTS: A single G -> T transversion was identified within the first coding exon of the Lim2 gene in the To3 mutant DNA. This DNA change results in the nonconservative substitution of a valine for the normally encoded glycine at amino acid 15 of the MP19 polypeptide. CONCLUSIONS: The identified genetic lesion in the Lim2 gene of the cataractous mouse mutant, To3, confirms Lim2 as an ideal candidate gene. Future transgenic experiments should provide proof or disproof of a causative relationship between the identified mutation and the cataractous phenotype. These studies indicate that MP19 may play an important role in both normal lens development and cataractogenesis, and warrants more intense investigation of its role within the ocular lens.

Amino Acid Sequence↗
PubMed1997

The effect of the interval between dose applications on the observed specific-locus mutation rate in the mouse following fractionated treatments of spermatogonia with ethylnitrosourea.

Our earlier analyses have suggested an apparent threshold dose-response for ethylnitrosourea-induced specific-locus mutations in treated spermatogonia of the mouse to be due to a saturable repair process. In the current study a series of fractionated-treatment experiments was carried out in which male (102 x C3H)F1 mice were exposed to 4 x 10, 2 x 40. 4 x 20 or 4 x 40 mg ethylnitrosourea per kg body weight with 24 h between applications; 4 x 40 mg ethylnitrosourea per kg body weight with 72 h between dose applications; and 2 x 40, 4 x 20 and 4 x 40 mg ethylnitrosourea per kg body weight with 168 h between dose applications. For all experiments with 24-h intervals between dose applications, there was no effect due to dose fractionation on the observed mutation rates, indicating the time interval between dose applications to be shorter than the recovery time of the repair processes acting on ethylnitrosourea-induced DNA adducts. In contrast, a fractionation interval of 168 h was associated with a significant reduction in the observed mutation rate due to recovery of the repair process. However, although reduced, the observed mutation rates for fractionation intervals of 168 h were higher than the spontaneous specific-locus mutation rate. These observations contradict the expectation for a true threshold dose response. We interpret this discrepancy to be due to the differences in the predictions of a mathematical abstraction of experimental data and the complexities of the biological system being studied. Biologically plausible explanations of the discrepancy are presented.

Animals↗
PubMed1997

Somatic and germ cell mutagenesis in lambda lacZ transgenic mice treated with acrylamide or ethylnitrosourea.

The transgenic Muta Mouse in vivo mutagenesis assay was employed to determine the activity of acrylamide and ethylnitrosourea in liver and germ cells after 3, 10 and 100 days following treatment. Each cell of the Muta Mouse carries 80 copies of the lambda gt10 phage including the bacterial lacZ gene, which act as the target gene for the mutagenesis assay. Groups of Muta Mice were given a single intraperitoneal injection of 80 or 160 mg/kg ethylnitrosourea or 50 or 100 mg/kg acrylamide. The tissues were prepared 3, 10 or 100 days post treatment. The liver genomic DNA was extracted with the manufacturer's standard protocol, while the genomic germ cell DNA was extracted with 4 different methods due to problems encountered in DNA yields and packaging efficiency. The mutation analysis of the lacZ gene was carried out by the positive selective assay method [Gossen et al. (1989) Proc. Natl. Acad. Sci. USA, 86, 7971-7975; Dean and Myhr (1994) Mutagenesis, 9, 183-185]. There was a slight increase due to treatment of the observed mutation frequencies in the acrylamide liver group for all three assay times. From the day 3 group to the day 100 group a time dependent decrease in all the absolute mutant frequencies was detectable. The ethylnitrosourea liver group showed a time- and dose-dependent increase in the mutant frequencies from day 3 to day 100. No meaningful results were obtained for the germ cell tissue assays due to the low amount of genomic DNA extracted which was not packageable in the lambda lacZ assay. At present for the mutagenesis assay of isolated spermatozoa in our laboratory we would be forced to pool tissues from animals to obtain enough DNA for an assay. Since 'jackpot'-animals may exist [Heddle et al. (1992) Mutation Res., 272, 195-203] the individual animals of such a pooled analysis group must be tested before pooling.

Acrylamide↗
PubMed1997

Genetic mapping of a mouse ocular malformation locus, Tcm, to chromosome 4.

The Tcm mutation in the mouse is an autosomal dominant ocular malformation manifesting as microphthalmia, iris dysplasia, cataract, and coloboma. As a first step to cloning the Tcm gene, we report the localization of the Tcm mutation with respect to known microsatellite markers. Backcross progeny carrying the Tcm mutation were produced by mating Tcm/+ heterozygous mice to normal C57BL/6 partners. Genomic DNA from each mouse was subjected to PCR analysis to identify simple sequence length polymorphisms. Our results locate Tcm to Chr 4 and suggest candidate genes responsible for the Tcm phenotype. Finally, ocular histopathology was done in 3-week-old animals to define the extent of the malformation.

Abnormalities, Multiple↗
PubMed1997

The mouse Cat4 locus maps to chromosome 8 and mutants express lens-corneal adhesion.

Cat4 is the second largest allelism group in the collection of mouse dominant eye mutations recovered in Neuherberg and carriers express anterior polar cataract, central corneal opacity, and lens-corneal adhesions. We have mapped the Cat4 locus of the mouse to central Chromosome (Chr) 8 at position cM 31. Histological characterization of Cat4(a) heterozygotes and homozygotes indicates failure of separation of the lens vesicle from the surface ectoderm. Human anterior segment ocular dysgenesis (ASOD) is autosomal dominant, carriers express an eye phenotype similar to that of Cat4(a) carriers, and it has been mapped to a region of 4q homologous to mouse central Chr 8. Thus, on the basis of phenotype and map position, Cat4 may be a mouse model of human ASOD. The genes Junb, Jund1, Mel, and Zfp42 are discussed as possible candidates for Cat4.

Animals↗
PubMed1997

Mapping of the autosomal dominant cataract mutation (Coc) on mouse chromosome 16.

PURPOSE: To characterize the mouse cataract mutation Coc. METHODS: Coc is an X-radiation-induced autosomal dominant cataract mutation maintained on a murine C3H inbred strain. The affected heterozygotes were outcrossed to C57BL/6, and (C3H Coc/+ x C57BL/6) mice that were Coc/+ were then backcrossed to C57BL/6 to generate a panel of 103 progeny for mapping. For linkage analysis, microsatellites from each autosome were selected. The maximum distance between markers was 30 centimorgans (cM). RESULTS: The initial genome-wide screen of 14 backcrossed progeny indicated that the Coc locus resides on chromosome 16. Further mapping with additional markers from chromosome 16 for all 103 backcrossed progeny positioned Coc between markers D16Mit134 and D16Mit63. This region is syntenic to human chromosome 3. CONCLUSIONS: Mapping of the Coc locus to mouse chromosome 16 provides the positional information necessary to identify the candidate gene responsible for the Coc phenotype. The molecular characterization of the gene disrupted in the Coc mutation will provide insight into the mechanisms involved in cataract formation.

Animals↗
PubMed1996

The mouse Pax2(1Neu) mutation is identical to a human PAX2 mutation in a family with renal-coloboma syndrome and results in developmental defects of the brain, ear, eye, and kidney.

We describe a new mouse frameshift mutation (Pax2(1Neu)) with a 1-bp insertion in the Pax2 gene. This mutation is identical to a previously described mutation in a human family with renal-coloboma syndrome [Sanyanusin, P., McNoe, L. A., Sullivan, M. J., Weaver, R. G. & Eccles, M. R. (1995) Hum. Mol. Genet. 4, 2183-2184]. Heterozygous mutant mice exhibit defects in the kidney, the optic nerve, and retinal layer of the eye, and in homozygous mutant embryos, development of the optic nerve, metanephric kidney, and ventral regions of the inner ear is severely affected. In addition, we observe a deletion of the cerebellum and the posterior mesencephalon in homozygous mutant embryos demonstrating that, in contrast to mutations in Pax5, which is also expressed early in the mid-hindbrain region, loss of Pax2 gene function alone results in the early loss of the mid-hindbrain region. The mid-hindbrain phenotype is similar to Wnt1 and En1 mutant phenotypes, suggesting the conservation of gene regulatory networks between vertebrates and Drosophila.

Abnormalities, Multiple↗
PubMed1996

Two new cataract loci, Ccw and To3, and further mapping of the Npp and Opj cataracts in the mouse.

Many types of inherited early onset cataract are known in both human and mouse. Here we describe the mapping of two novel dominant cataract loci in the mouse genome. Cataract and curly whiskers, Ccw, maps to Chromosome 4, 3.1 +/- 1.1 cM distal to the b (brown) locus. Total opacity 3, To3, maps to Chromosome 7, 7.1 +/- 1.8 cM proximal to p (pink-eyed dilution). The map positions of two other dominant cataract mutants have now been refined by three-point crosses. Nuclear and posterior polar cataract, Npp, maps to the central part of Chromosome 5, 1.4 +/- 0.5 cM distal to We (dominant spotting-extreme, an allele at the Kit locus), and Opaque secondary fiber cell junctions, Opj, maps to the proximal region of Chromosome 16, 9.1 +/- 1.5 cM distal to the marker md (mahoganoid). While there are no obvious candidate genes in the vicinity of the Ccw, Npp, and Opj mutations, To3 lies remarkably close to the recently mapped Lim2 locus, which encodes lens intrinsic membrane protein 2, also called MP19.

Animals↗
PubMed1995

Mutagenesis and human genetic disease: dominant mutation frequencies and a characterization of mutational events in mice and humans.

Dominant deleterious traits are generally regarded to be the most relevant genetic endpoints when the expected increased mutational load of genetic diseases associated with exposure to mutagenic agents is considered in humans. At present, human risk estimation procedures rely on results from laboratory mammal germ-cell mutagenicity experiments as well as on data from human epidemiology and medical genetics. A comparison of the mouse and human data indicates that a small subset of loci, which when mutated result in a dominant phenotype, is contributing disproportionately to the observed mutation frequency. This is likely due to the fact that those loci with an observed high mutation frequency are inherently unstable, the function of such loci is critical, and/or the wild-type phenotype requires two copies of the normal gene (haploinsufficiency). The locus specificity of the observed spontaneous and induced mutation frequencies implies that efforts must be made to closely match those genetic endpoints screened in the mouse with the human genetic endpoints considered relevant in estimating the genetic risk after exposure to mutagenic agents. The contributions to our understanding of the organization, function, and stability of the mouse and human genomes provided by molecular biological techniques should make compliance with this restriction feasible.

Animals↗