In addition to their role in gastric acid secretion, parietal cells secrete a number of growth factors that may influence the differentiation of other gastric lineages. Indeed, oxyntic atrophy is considered the most significant correlate with increased risk for gastric adenocarcinoma. We studied the alterations in gastric mucosal lineages elicited by acute oxyntic atrophy induced by treatment of C57BL/6 and gastrin-deficient mice with the parietal cell protonophore [S-(R*,S*)]-N-[1-(1,3-benzodioxol-5-yl)butyl]-3,3-diethyl-2-[4-[(4-methyl-1-piperazinyl)carbonyl]phenoxy]-4-oxo-1-azetidinecarboxamide (DMP-777). In both wild-type and gastrin knockout mice, DMP-777 elicited the rapid loss of parietal cells within 2 days of treatment. In wild-type mice, oxyntic atrophy was accompanied by a rapid increase in 5-bromo-2'-deoxyuridine-labeled proliferative cells and attendant increase in surface cell numbers. However, gastrin knockout mice did not demonstrate significant foveolar hyperplasia and showed a blunted proliferative response. After 7 days of treatment in wild-type mice, a second proliferative population emerged at the base of fundic glands along with the development of a mucous cell metaplasia expressing TFF2/spasmolytic polypeptide (SPEM). However, in gastrin knockout mice, SPEM expressing both TFF2 mRNA and protein developed after only 1 day of DMP-777 treatment. In wild-type mice, all changes induced by DMP-777 were reversed 14 days after cessation of treatment. In gastrin-deficient mice, significant SPEM was still present 14 days after the cessation of treatment. The results indicate that foveolar hyperplasia requires the influence of gastrin, whereas SPEM develops in response to oxyntic atrophy independent of gastrin, likely through transdifferentiation of chief cells.

Background & Aims-Loss of gastric parietal cells is a critical precursor to gastric metaplasia and neoplasia. However, the origin of metaplasia remains obscure. Acute parietal cell loss in gastrin-deficient mice treated with DMP-777 leads to the rapid emergence of Spasmolytic polypeptide/TFF2-expressing metaplasia (SPEM) from the bases of fundic glands. We have now sought to characterize more definitively the pathway for emergence of SPEM.

␣-Tocopherol transfer protein (␣-TTP), a cytosolic protein that specifically binds ␣-tocopherol, is known as a product of the causative gene in patients with ataxia that is associated with vitamin E deficiency. Targeted disruption of the ␣-TTP gene revealed that ␣-tocopherol concentration in the circulation was regulated by ␣-TTP expression levels. Male ␣-TTP ؊/؊ mice were fertile; however, placentas of pregnant ␣-TTP ؊/؊ females were severely impaired with marked reduction of labyrinthine trophoblasts, and the embryos died at mid-gestation even when fertilized eggs of ␣-TTP ؉/؉ mice were transferred into ␣-TTP ؊/؊ recipients. The use of excess ␣-tocopherol or a synthetic antioxidant (BO-653) dietary supplement by ␣-TTP ؊/؊ females prevented placental failure and allowed full-term pregnancies. In ␣-TTP ؉/؉ animals, ␣-TTP gene expression was observed in the uterus, and its level transiently increased after implantation (4.5 days postcoitum). Our results suggest that oxidative stress in the labyrinth region of the placenta is protected by vitamin E during development and that in addition to the hepatic ␣-TTP, which governs plasma ␣-tocopherol level, the uterine ␣-TTP may also play an important role in supplying this vitamin.Vitamin E (␣-tocopherol) is the most potent lipid-soluble antioxidant in biological membranes, where it contributes to membrane stability. Patients with ataxia and isolated vitamin E deficiency (AVED) 1 have low or undetectable serum vitamin E concentrations and exhibit neurological dysfunction and muscular weakness. It is now established that ␣-tocopherol transfer protein (␣-TTP), a cytosolic liver protein known to specifically bind to ␣-tocopherol (1), is defective in AVED patients (2), indicating that ␣-TTP is a major determinant of plasma ␣-tocopherol level. Although ␣-tocopherol was initially identified as an anti-sterility factor to prevent abortion (3), the mechanism of action and the molecules responsible for its antisterility effect remain unknown. One of the reasons for this is that vitamin E is difficult to deplete from tissues and requires elaborate manipulations to cause deficiency symptoms to occur in experimental animals. In this study, we established a mouse model lacking ␣-TTP by targeted mutagenesis. This animal model for human AVED patients is suitable for examination of the complex pathophysiology of diseases associated with vitamin E deficiency and/or caused by oxidative stress. Here we examined the role of ␣-TTP in pregnancy and embryogenesis using our new animal model. MATERIALS AND METHODSGeneration of ␣-TTP Knockout Mice-An ␣-TTP targeting vector was constructed from an 8.8-kb ␣-TTP genome fragment encompassing exon 1. We inserted a fragment of PGK-neo cassette into the SmaI-SmaI site positioned 5Ј and 3Ј to exon 1 and flanked a 1.8-kb fragment of HSV-tk gene downstream of exon 2. AB2.2-Prime ES cells (Lexicon Genetics) or A3-1 ES (4) cells were transfected by electroporation with a linearized targeting vector. G418/gancyclovir-resistant clones were screened by PCR, and...

Might DNA sequence variation reflect germline genetic activity and underlying chromatin structure? Using two strains of medaka (Japanese killifish, Oryzias latipes), we compared genomic sequence and mapped ~37.3 million nucleosome cores from medaka Hd-rR blastulae, together with 11,654 representative transcription start sites from six embryonic stages. We observed a ~200-bp periodic pattern of genetic variation downstream of transcription start sites; the rate of insertions and deletions longer than 1bp peaked at positions approximately +200, +400, and +600bp, while the point mutation rate showed corresponding valleys. This ~200-bp periodicity was correlated with the chromatin structure, with nucleosome occupancy minimized at positions 0, +200, +400, and +600bp. These data exemplify the potential for genetic activity (transcription) and chromatin structure to contribute in molding the DNA sequence on an evolutionary timescale.Mutation and repair characteristics of DNA sequence in experimental systems have been shown in a number of cases to reflect structures in chromatin. For one well-studied experimental system, UV-treated yeast (S. cerevisiae), repair rates for a set of DNA nucleosome core regions are lower than in the surrounding linker regions (1-4). Correlations between chromatin structure and mutation rates have also been suggested in analysis of human and yeast genomes *joint corresponding authors. One-sentence summary: Sequence variation in the DNA Japanese killifish, Oryzias latipes, shows a periodic pattern downstream of transcription start sites that is strongly correlated with chromatin structure.