Survival, mutagenesis, and host cell reactivation in a Chinese hamster ovary cell ERCC1 knock-out mutant

Positive selection-negative selection gene targeting was usedto disrupt the nucleotide excision repair gene ERCC1 in a Chinesehamster ovary cell line, CHO-K1. Southern and Northern analysisshowed that a cell clone isolated by this targeting approach,CHO-7-27, had an ERCC1 gene structure consistent with targeteddisruption of ERCC1 exon V, and did not express ERCC1 mRNA.CHO-7-27 was further characterized with respect to UV and mitomycinC sensitivities, and was shown to exhibit severe mutagen sensitivityphenotypes consistent with those of other CHO cell ERCC1 mutants.Mutation frequency experiments showed that CHO-7-27 was UV-hypermutableat the hypoxanthine-guanine phosphoribosyltransferase locus.Experiments assessing host cell reactivation of viral DNA synthesisfor UV-irradiated adenovirus showed that CHO7-27 exhibited aseverely deficient HCR phenotype similar to that of UV20 cells.Our results demonstrate that CHOK1 cells are hemizygous forthe ERCC1 gene, and show that the comparatively mild mutagensensitivities and lack of severely deficient HCR phenotypesof conventionally derived CHO-K1 ERCC1 mutants, in contrastto the severe phenotypes of CHO-AA8-derived mutants, are notdue to any intrinsic genetic differences between CHO-K1 andCHO-AA8 parental cell lines. ⁴To whom correspondence should be addressed     

成纤维细胞介导白细胞介素6基因疗法对化疗导致的造血损伤的恢复作用

研究了成纤维细胞介导的人白细胞介素６（Ｉｎｔｅｔｒｌｅｕｋｉｎ－６，ＩＬ－６）基因疗法对预先体内注射１５０ｍｇ／ｋｇ５－氟尿嘧啶（５－ＦＵ）所造成的造血损伤小鼠模型的治疗作用。结果发现，外周血血小板数量在移殖高分泌ＩＬ－６成纤维细胞后第１０天开始持续上升，第２２天血小板数量恢复到化疗前水平，中性粒细胞数量也显著增高，但对白细胞恢复没有明显的促进作用。骨髓和脾脏ＣＦＵ－ＧＭ及ＣＦＵ－ＭＫ在体内移殖高分泌ＩＬ－６成纤维细胞后，体外动态观察发现：骨髓和脾脏ＣＦＵ－ＧＭ、ＣＦＵ－ＭＫ在第４～７天左右数量为０，在第１０天左右数量开始上升，于第１６天左右数量显著增高，对ＣＦＵ－ＧＭ、ＣＦＵ－ＭＫ具有明显的恢复作用，ＣＦＵ－Ｓ数量也显著增高。表明成纤维细胞介导的白细胞介素６基因疗法能显著治疗化疗导致的造血损伤，可望为肿瘤放、化疗导致的机体造血损伤提供新的治疗途径。     

Bacterial chemotaxis modulates host cell apoptosis to establish a T-helper cell, type 17 (Th17)-dominant immune response in Helicobacter pylori infection

The host inflammatory response to chronic bacterial infections often dictates the disease outcome. In the case of the gastric pathogen Helicobacter pylori, host inflammatory responses result in outcomes that range from moderate and asymptomatic to more severe with concomitant ulcer or cancers. It was found recently that H. pylori chemotaxis mutants (Che(-)), which lack directed motility but colonize to nearly wild-type levels, trigger less host inflammation. We used these mutants to observe host immune responses that resulted in reduced disease states. Here we report that these mutants are defective for early gastric recruitment of CD4(+) T cells compared with wild-type infection. Furthermore, Che(-) mutant infections lack the T-helper cell, type 17 (Th17) component of the immune response, as measured by cytokine mRNA levels in gastric tissue via intracellular cytokine staining and immunofluorescence. We additionally find that a Che(-) mutant infection results in significantly less host cell apoptosis than does wild-type infection, in accordance with previous observations that T-helper cell, type 17 responses in Citrobacter rodentium infections are driven by concomitant bacterial and apoptotic cell signals. We propose that bacterial chemotaxis allows H. pylori to access a particular host niche that allows the bacteria to express or deliver proapoptotic host cell factors. This report indicates that chemotaxis plays a role in enhancing apoptosis, suggesting bacterial chemotaxis systems might serve as therapeutic targets for infections whose symptoms arise from host cell apoptosis and tissue damage.     

Helicobacter pylori Requires TlpD-Driven Chemotaxis To Proliferate in the Antrum

Different disease outcomes of Helicobacter pylori infection correlate with distinct inflammation patterns. These different inflammatory distributions may be initiated by differences in bacterial localization. One H. pylori property known to affect murine stomach localization is chemotaxis, the ability to move in response to chemical cues. In this report, we used nonchemotactic mutants (Che(-)) to analyze whether chemotaxis is required for initial colonization of particular stomach regions or for subsequent growth therein. We found that H. pylori behaves differently in the corpus, antrum, and corpus-antrum transition zone subregions of the stomach. This outcome suggests that these regions contain unique chemotactic signals. In the corpus, H. pylori utilizes chemotaxis for initial localization but not for subsequent growth. In contrast, in the antrum and the corpus-antrum transition zone, chemotaxis does not help initial colonization but does promote subsequent proliferation. To determine which chemoreceptor is responsible for the corpus-antrum phenotypes, we infected mice with strains lacking each chemoreceptor. Strains lacking TlpA, TlpB, or TlpC displayed only modest deviations from the wild-type phenotype, while strains lacking TlpD resembled the Che(-) mutant in their antral colonization defect and fared even worse than the Che(-) mutant in the corpus. Additional analysis showed that inflammation is worse in the antrum than in the corpus in both wild-type and Che(-) mutant infections. These results suggest that chemotaxis, specifically, that controlled by TlpD, is necessary for H. pylori to survive or grow in the environment of increased inflammation in the antrum.     

Myxoinflammatory fibroblastic sarcoma showing t(2;6)(q31;p21.3) as a sole cytogenetic abnormality

Myxoinflammatory fibroblastic sarcoma (MIFS) is a rare, low-grade sarcoma characterized by distinctive, large, and bizarre Reed--Sternberg--like cells associated with an intense inflammatory infiltrate. The biology of MIFS is still poorly understood, and only two previous cases had been studied cytogenetically. In the present case, analysis of MIFS in the foot of a 53-year-old man revealed the chromosome translocation t(2;6)(q31;p21.3) as the only cytogenetic abnormality. This finding is distinct from the two cases previously reported. Additional studies are needed to verify whether any of these chromosome rearrangements are involved recurrently in MIFS.     

Vitamins: physiology and deficiency states

Approximately half of the people in the United States take vitamin supplements, and some use alarmingly high doses. In this article, physiological functions of vitamins and the effects of vitamin deficiencies are summarized. Common food sources of vitamins are listed and a suggested daily eating guide is provided to assist in proper food intake. Adding vitamin supplements to a poor diet may alleviate some symptoms of deficiency, but cannot compensate for the lack of other nutrients. For optimum health, balanced, wholesome meals are recommended.     

Linking DNA damage and neurodegeneration

Many human pathological conditions with genetic defects in DNA damage responses are also characterized by neurological deficits. These neurological deficits can manifest themselves during many stages of development, suggesting an important role for DNA repair or processing during the development and maintenance of the nervous system. Although the molecular neuropathology associated with such deficits is largely unknown, many of the responsible gene defects have been identified. The current rapid progress in elucidation of molecular details following gene identification should provide further insight into the importance of DNA processing in nervous system function.