Mutator activity in uvs mutants of Aspergillus nidulans

The mechanism of electroacupuncture for depression on basic research: a systematic review

BACKGROUND

Electroacupuncture (EA) is generally accepted as a safe and harmless treatment option for alleviating depression. However, there are several challenges related to the use of EA. Although EA has been shown to be effective in treating depression, the molecular mechanism is unclear.

OBJECTIVE

To reveal the therapeutic effect of EA and its possible mechanism in the treatment of depression.

SEARCH STRATEGY

We performed a systematic search according to PRISMA guidelines. We electronically searched PubMed, Web of Science (WOS), the China National Knowledge Infrastructure (CNKI), Wanfang Data Information Site and the VIP information database for animal studies in English published from the inception of these databases to December 31, 2019.

INCLUSION CRITERIA

Electronic searches of PubMed, WOS, the CNKI, Wanfang and the VIP database were conducted using the following search terms: (depression OR depressive disorder OR antidepressive), (rat OR mouse) AND (acupuncture OR EA).

DATA EXTRACTION AND ANALYSIS

The data were extracted primarily by one author, and a follow-up review was conducted by the other authors.

RESULTS

Twenty-eight articles met the inclusion criteria. The most commonly used method for inducing depression in animal models was 21 days of chronic unpredictable mild stress. For the depression model, the most commonly selected EA frequency was 2 Hz. Among the 28 selected studies, 11 studies observed depression-related behaviors and used them as indicators of EA efficacy. The other 17 studies focused on mechanisms and assessed the indexes that exhibited abnormalities that were known to result from depression and then returned to a normal range after EA treatment. Treatment of depression by EA involves multiple therapeutic mechanisms, including inhibition of HPA axis hyperactivity and inflammation, regulation of neuropeptides and neurotransmitters, modulation of the expression of particular genes, restoration of hippocampal synaptic plasticity, increased expression of BDNF, and regulation of several signaling pathways.

CONCLUSIONS

This review reveals that the mechanisms underlying the effect of acupuncture involve multiple pathways and targets, suggesting that acupuncture is a wholistic treatment for people rather than for diseases. Our findings also explain why acupuncture can treat various disorders in addition to depression.

Aspergillus nidulans as a model system to characterize the DNA damage response in eukaryotes

Interest in DNA repair in Aspergillus nidulans had mainly grown out of studies of three different biological processes, namely mitotic recombination, inducible responses to detrimental environmental changes, and genetic control of the cell cycle. Ron Morris started the investigation of the genetic control of the cell cycle by screening hundreds of cell cycle temperature sensitive Aspergillus mutants. The sequencing and innovative analysis of these genes revealed not only several components of the cell cycle machinery that are directly involved in checkpoint response, but also components required for DNA replication and DNA damage response machinery. Here, we will provide an overview about currently known aspects of the DNA damage response in A. nidulans. Emphasis is put on analyzed mutants that are available and review epistatic relationships and other interactions among them. Furthermore, a comprehensive list of A. nidulans genes involved in different processes of the DNA damage response, as identified by homology of genome sequences with well-characterized human and yeast DNA repair genes, is shown.

The uvsI gene of Aspergillus nidulans required for UV-mutagenesis encodes a homolog to REV3, a subunit of the DNA polymerase zeta of yeast involved in translesion DNA synthesis

Defects in the uvsI gene of Aspergillus nidulans resulted in high UV sensitivity and reductions of spontaneous and UV-induced reversion of certain alleles, uvsl;uvsA double mutants exhibited high methyl methane sulfonate (MMS)-sensitivity in contrast to the slight sensitivity of the component single mutants. Using such a double mutant as recipient, a clone complementing uvsI501 has been isolated from a chromosome III specific library. The deduced amino acid sequence from the 1.1-kb sequenced region, a part of the 5.2-kb DNA fragment showing uvsI-complementing activity, had a 62% identity with REV3 of yeast. Disruptants of the cloned gene demonstrated the same level of sensitivity to UV light as uvsI and failed to complement uvsI501 in heterozygous diploids.

uvsI mutants defective in UV mutagenesis define a fourth epistatic group of uvs genes in Aspergillus

Three UV-sensitive mutations of A. nidulans, uvsI, uvsJ and uvsA, were tested for epistatic relationships with members of the previously established groups, here called the "UvsF", "UvsC", and "UvsB" groups. uvsI mutants are defective for spontaneous and induced reversion of certain point mutations and differ also for other properties from previously analyzed uvs types. They are very sensitive to the killing effects of UV-light and 4-NQO (4-nitro-quinoline-N-oxide) but not to MMS (methylmethane sulfonate). When double- and single-mutant uvs strains were compared for sensitivity to these three agents, synergistic or additive effects were found for uvsI with all members of the three groups. The uvsI gene may therefore represent a fourth epistatic group, possibly involved in mutagenic repair. On the other hand, uvsJ was clearly epistatic with members of the UvsF group and fitted well into this group also by phenotype. The uvsA gene was tentatively assigned to the UvsC group. uvsA showed epistatic interactions with uvsC in all tests, and like UvsC-group mutants is UV-sensitive mainly in dividing cells. However, the uvsA mutation does not cause the defects in recombination and UV mutagenesis typical for this group.

An uvsB mutant of Aspergillus nidulans with high variable spontaneous mutation and intergenic mitotic recombination frequencies

An UV-sensitive mutant has been isolated with a new technique which allows isolation of UV-sensitive and UV-non-mutable mutants in Aspergillus nidulans. This mutant is an allele of the known uvsB gene but shows some features not previously described in the alleles so far isolated. Its more important characteristics are: (1) Frequency of mitotic intergenic recombination is strongly increased in uvs/uvs diploids and it is highly variable in different clones: it varies from a minimum of 40-fold to a maximum of about 1000-fold in comparison with uvs+/uvs+ strains. (2) The frequency of mitotic intergenic recombination is increased also in the heterozygous diploids. (3) The frequency of spontaneous mutation is higher and highly variable in different subclones: it may be increased up to 1000-fold.

Genetic analysis of DNA repair in Aspergillus: evidence for different types of MMS-sensitive hyperrec mutants

To identify genes which affect DNA repair and possibly recombination in Aspergillus nidulans, mutants hypersensitive to methyl methanesulphonate (MMS) were induced with ultraviolet light (UV) or gamma-rays. About half of them contained associated translocations and many were hypersensitive to UV and/or defective in meiosis. Two are alleles of the known uvsB gene while most others define new genes. In addition, among available uvs mutants many were found to be MMS-sensitive. Some of the various uncharacterized ones were identified as alleles of known uvs, but 5 of them were mapped in 2 new genes, uvsH and uvsJ. To identify functional and epistatic groups, mutants from each uvs gene were tested for effects on recombination and mutation, and double mutant uvs strains were compared for UV survival to their component single mutant strains. 3 epistatic pairs were identified, (1) uvsF and H, (2) uvsB and D, and (3) uvsC and E. Conclusive interpair tests were difficult, because such double mutant combinations were frequently lethal or nearly so. The first pair, uvsF and H, shared some of the properties of excision-defective mutants, both uvs being very highly sensitive to UV for mutation as well as survival. But unlike such mutants, uvsH was also sensitive to gamma-rays and defective in meiosis. Both uvs showed normal levels of meiotic recombination, but greatly increased spontaneous mitotic crossing-over, being the most "hyperrec" types among all uvs. The second pair, uvsB and uvsC, which was similarly hyperrec showed only slight increases of UV-induced mutation (less than 2-fold). As a main effect, these uvs caused very high frequencies of unbalanced, unstable segregants from diploid conidia (30 X), but few of these were recognizable aneuploids. The third pair, uvsC and E, which are known to be rec- for gene conversion, caused reduced mitotic crossing-over in diploids and increased levels of haploid segregants. These mutants are spontaneous mutators, but showed less UV-induced mutation than wild-type controls.

UV-induced recessive lethals in uvs strains of Neurospora which are deficient in UV mutagenesis

The frequencies of spontaneous and UV-induced recessive lethal mutations were compared for UV-sensitive and wild-type heterokaryons of Neurospora crassa. These heterokaryons were homokaryotic either for one of two alleles of uvs-3, or for uvs-6 or uvs+. For uvs-3, which is known to have mutator effects, spontaneous recessive lethals were found to be 4-6 times more frequent than observed in uvs+. After correction for clonal distribution of spontaneous mutants, an observed 2-fold increase for uvs-6 was not statistically significant and may have been due to chance occurrence of a few large clones of mutants. Treatment with low doses of UV (50-200 J/m2) produced very similar overall rates of increase for recessive lethals in uvs and uvs+ heterokaryons. This means, that in contrast to results obtained when mutation to ad-3 was measured, both uvs-3 alleles showed highly significant increases for recessive lethals when treated with UV. It is proposed that certain types of UV damage may be processed into recessive lethal mutations by an alternate mechanism from that responsible for viable mutations.

Genetic and environmental modification of gene expression in the brlA12 variegated position effect mutant of Aspergillus nidulans

ThebrlA12variegated position effect mutant is particularly suited for tests of environmental and genetic influences on variegation, but out of a large number of substances added to the medium, only salts at high concentrations and methylamine significantly increased expression of this gene. Medium shifting experiments showed thatbrlA12activity could be switched on late, but once active, was rarely switched off again during conidiation. SeparatebrlA12clones in heterokaryons were activated independently. SomebrlA12-specific suppressor mutants, including those at loci giving almost complete suppression, have been studied. One class of suppressors also confers inability to utilize galactose as carbon source and comparison with other, pre-existing mutants showed that thebrlA12phenotype was either suppressed or enhanced by mutants with complex phenotypes involving galactose utilization, molybdate resistance, acid phosphatase production and sulphur metabolism. Tests for the involvement of DNA methylation inbrlA12expression gave negative results.

Mutational synergism between p-fluorophenylalanine and UV in Coprinus lagopus

Previous studies have shown that the amino acid analogue p-fluorophenylalanine (PFP) is mutagenic to Coprinus lagopus due to its incorporation into proteins [32]. Spontaneous mutations, PFP and UV mutagenesis and PFP/UV synergism have been studied in a UV resistant strain and in two complementing UV sensitive mutant strains. By comparison to the UV resistant strain, one UV sensitive strain shows normal spontaneous mutations, 1.4% PFP-induced mutations and 50-fold UV mutagenesis. The second UV sensitive strain has 19-fold spontaneous mutation frequency, 8% PFP induced mutations and slightly elevated UV mutagenesis. In all 3 strains the PFP/UV synergism is comparable (4--5 times the arithmetic expected). The results indicate that PFP mutagenesis is due to the incorporation of PFP into enzymes normally functioning in the organism but which also participate in UV repair mechanisms. A model is proposed for UV repair which is based on a PFP sensitive excision repair system of at least two enzymes, and alternative "error proof" pathway which is not suscetible to PFP and an "error prone" pathway which is responsible for UV mutagenesis and is susceptible to PFP as shown by the PFP/UV synergism. Because PFP is given before UV treatment, this implies a UV inducible cofactor and a PFP sensitive enzyme which only functions after UV activation.

The mutagenicity of amino acid analogues in Coprinus lagopus

The amino acid analoguesp-fluorophenylalanine (PFP) and ethionine (ETH) are strongly mutagenic inCoprinus lagopus. The most pronounced effect was found with suppressor mutations of themet-1locus. PFP, at a concentration of 2·4 × 10−4M, increased the mutation frequency 500 fold and ETH, at a concentration of 2·4 × 10−3M, 30 fold over the spontaneous mutation frequency. From the spectrum of suppressors of themet-1locus and the dominant revertants of thead-82locus, induced by analogue treatments, it was concluded that both analogues induce single base-change mutations. The dose response curves follow a sigmoid plot, revealing that within a certain range of analogue concentrations, muta-genesis is strongly dose dependent.

Using analogue resistant mutants, it has been shown that PFP mutagenesis is a function of its incorporation into protein. However, ETH mutagenesis is independent of protein incorporation but can be correlated with the degree of ethylation of nucleic acids. The synergistic effect PFP and ETH supports the evidence of the different mutagenic actions of the two analogues.