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Isolation of a large number of novel mammalian genes by a differential cDNA library screening strategy.

ABSTRACT: As part of the ongoing human and mouse genome projects, the aim of this study was to isolate novel, previously uncharacterized, genes from mouse testis. Two approaches were compared for their effectiveness in isolating novel genes: random, vs differential, complementary DNA (cDNA) cloning methods. In the differential approach, only the cDNA clones containing rare sequences (as determined by preliminary clone hybridization) are further analyzed; in the random approach, cDNA clones are isolated at random from the cDNA library. More than two hundred cDNA clones altogether were analyzed, using a PCR-mediated amplification and sequencing strategy. A comparison of these sequences to nucleic acid and protein sequence databases, revealed that 84% of the isolated rare cDNA clones represented new, previously uncharacterized mouse genes. In contrast, less than 63% of the cDNA clones isolated at random from cDNA libraries, contained novel genes. Thus, the probability of isolating new, previously uncharacterized, mammalian genes from cDNA libraries can be markedly improved by focusing efforts on clones containing rare sequences.

SUBMITTER: Hoog C

PROVIDER: S-EPMC329100 | biostudies-other | 1991 Nov

REPOSITORIES: biostudies-other

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Isolation of a large number of novel mammalian genes by a differential cDNA library screening strategy.

Höög C C

Nucleic acids research 19911101 22

As part of the ongoing human and mouse genome projects, the aim of this study was to isolate novel, previously uncharacterized, genes from mouse testis. Two approaches were compared for their effectiveness in isolating novel genes: random, vs differential, complementary DNA (cDNA) cloning methods. In the differential approach, only the cDNA clones containing rare sequences (as determined by preliminary clone hybridization) are further analyzed; in the random approach, cDNA clones are isolated at ...[more]

PMID: 1659684

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Project description:BackgroundEimeria maxima is one of the most prevalent Eimeria species causing avian coccidiosis, and results in huge economic loss to the global poultry industry. Current control strategies, such as anti-coccidial medication and live vaccines have been limited because of their drawbacks. The third generation anticoccidial vaccines including the recombinant vaccines as well as DNA vaccines have been suggested as a promising alternative strategy. To date, only a few protective antigens of E. maxima have been reported. Hence, there is an urgent need to identify novel protective antigens of E. maxima for the development of neotype anticoccidial vaccines.MethodsWith the aim of identifying novel protective genes of E. maxima, a cDNA expression library of E. maxima sporozoites was constructed using Gateway technology. Subsequently, the cDNA expression library was divided into 15 sub-libraries for cDNA expression library immunization (cDELI) using parasite challenged model in chickens. Protective sub-libraries were selected for the next round of screening until individual protective clones were obtained, which were further sequenced and analyzed.ResultsAdopting the Gateway technology, a high-quality entry library was constructed, containing 9.2 × 106 clones with an average inserted fragments length of 1.63 kb. The expression library capacity was 2.32 × 107 colony-forming units (cfu) with an average inserted fragments length of 1.64 Kb. The expression library was screened using parasite challenged model in chickens. The screening yielded 6 immune protective genes including four novel protective genes of EmJS-1, EmRP, EmHP-1 and EmHP-2, and two known protective genes of EmSAG and EmCKRS. EmJS-1 is the selR domain-containing protein of E. maxima whose function is unknown. EmHP-1 and EmHP-2 are the hypothetical proteins of E. maxima. EmRP and EmSAG are rhomboid-like protein and surface antigen glycoproteins of E. maxima respectively, and involved in invasion of the parasite.ConclusionsOur results provide a cDNA expression library for further screening of T cell stimulating or inhibiting antigens of E. maxima. Moreover, our results provide six candidate protective antigens for developing new vaccines against E. maxima.

Project description:AIM:To gain tumor endothelium associated antigen genes from human liver cancer vascular endothelial cells (HLCVECs) cDNA expression library, so as to find some new possible targets for the diagnosis and therapy of liver tumor. METHODS:HLCVECs were isolated and purified from a fresh hepatocellular carcinoma tissue sample, and were cultured and proliferated in vitro. A cDNA expression library was constructed with the mRNA extracted from HLCVECs. Anti-sera were prepared from immunized BALB/c mice through subcutaneous injection with high dose of fixed HLCVECs, and were then tested for their specificity against HLCVECs and angiogenic effects in vitro, such as inhibiting proliferation and inducing apoptosis of tumor endothelial cells, using immunocytochemistry, immunofluorescence, cell cycle analysis and MTT assays, etc. The identified xenogeneic sera from immunized mice were employed to screen the library of HLCVECs by modified serological analyses of recombinant cDNA expression libraries (SEREX). The positive clones were sequenced and analyzed by bio-informatics. RESULTS:The primary cDNA library consisted of 2 x 10(6) recombinants. Thirty-six positive clones were obtained from 6 x 10(5) independent clones by immunoscreening. Bio-informatics analysis of cDNA sequences indicated that 36 positive clones represented 18 different genes. Among them, 3 were new genes previously unreported, 2 of which were hypothetical genes. The other 15 were already known ones. Series analysis of gene expression (SAGE) database showed that ERP70, GRP58, GAPDH, SSB, S100A6, BMP-6, DVS27, HSP70 and NAC alpha in these genes were associated with endothelium and angiogenesis, but their effects on HLCVECs were still unclear. GAPDH, S100A6, BMP-6 and hsp70 were identified by SEREX in other tumor cDNA expression libraries. CONCLUSION:By screening of HLCVECs cDNA expression library using sera from immunized mice with HLCVECs, the functional genes associated with tumor endothelium or angiogenesis were identified. The modified SEREX, xenogeneic functional serum screening, was demonstrated to be effective for isolation and identification of antigen genes of tumor endothelium, and also for other tumor cell antigen genes. These antigen genes obtained in this study could be a valuable resource for basic and clinical studies of tumor angiogenesis, thus facilitating the development of anti- angiogenesis targeting therapy of tumors.

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Isolation of a large number of novel mammalian genes by a differential cDNA library screening strategy.

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Isolation of a large number of novel mammalian genes by a differential cDNA library screening strategy.

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