SEARCH · PubMed Health

Results for “Transgene segregation bias”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

7 recordsLinked to original sources

PubMed2026

Inducing fixation of transgenic alleles in open-pollinated populations.

The progeny of chlorsulfuron-resistant forage rape (Brassica napus L. subsp. napus, cv. Giant) and potato (Solanum tuberosum L. cv. Iwa) plants hemizygous for a single transgenic locus were screened for transgene segregation following an application of either water or chlorsulfuron. The transgenic locus contained three transgenes conferring kanamycin resistance (NOS-NPTII-NOS), β-glucuronidase (GUS) activity (35S-GUS-OCS), and chlorsulfuron resistance (a complete acetohydroxyacid synthase gene with a proline197 to serine substitution). In the absence of the herbicide application, plants segregated for GUS activity as expected for single locus inheritance. However, the progeny of plants sprayed with chlorsulfuron exhibited a highly distorted segregation for GUS activity, with a significant excess of transgenic progeny. Inducing such biased segregation provides a simple treatment to rapidly drive the fixation of transgenic alleles to homozygosity in open pollinated populations during seed increases of new cultivars.

Alleles↗

PubMed1996

Transgenic grain legumes obtained by in planta electroporation-mediated gene transfer.

Electroporation-mediated gene transfer into intact plant tissues was demonstrated in pea, cowpea, lentil, and soybean plants. Transient expression of a chimeric gus reporter gene was used to monitor the uptake and expression of the introduced DNA in electroporated nodal axillary buds in vivo. The branches that grew out of the nodal meristems were chimeric and expressed the introduced gene up to 20 d after electroporation. Transgenic R1 pea, lentil, and cowpea plants were recovered from seeds originating on these chimeric branches as shown by Southern blot hybridization and GUS expression. Transgenic R2 soybean and lentil plants were also obtained. Segregation ratios in these populations showed a strong bias against transgene presence or expression.

DNA, Plant↗

PubMed2002

[Studies on the distorted segregation of foreign genes in transgenic rice progenies].

The segregation mode of transgenes was investigated in the transgenic progenies of three rice varieties (lines) produced by Agrobacterium-mediated transformation. The transgenic lines all contained the Bacillus thuringiensis cry1Ab gene, under the control of a maize ubiquitin promoter, and linked in tandem with gusA and hpt genes. PCR analysis showed the transgenes cry1Ab and gusA co-segregated in all self and crossed progenies tested. Therefore, GUS bio-assay of leaf or endosperm tissues was used to monitor transgene segregation in the experiment. It was found that the ratio of positive to negative plants was significantly smaller than 3:1 in all heterozygous plants derived progenies, which implied the segregation biased from typical Mendelian mode for a single dominant gene. Less GUS positive plants, and consequently less homozygous transgenic lines than expected were recovered from the self progenies. Transgenic heterozygous plants (+/-) were crossed as female or male parent to conventional rice varieties (-/-), and the ratio of gusA positive (+/-) to negative (-/-) plants was investigated in test F1 population. When used as female parent, the segregation fit to 1:1, but significantly smaller than 1:1 when used as male parent. The seed-set of transgenic Nipponbare progeny was investigated individually for GUS positive and negative plants. It was found that the positive plants had an average seed-set of 64.5%, significantly lower than that of negative plants (77.9%). The biological and genetic basis of distorted segregation of transgenes was discussed and deduced on the basis of above results, and the authors are inclined to ascribe these phenomena to the poor competitive ability of pollens carrying transgenes.

Bacillus thuringiensis Toxins↗

PubMed2005

Transposable element insertion location bias and the dynamics of gene drive in mosquito populations.

Some vector-borne disease control strategies using transgenic mosquitoes require transgene spread to high frequency in populations. Transposable elements (TEs) are DNA sequences that replicate and transpose within the genomes of other organisms and may therefore be represented in the next generation in higher frequencies than predicted by Mendelian segregation. This over-representation has allowed some TEs to spread through natural populations. Transgenes incorporated within a TE sequence are expected to be driven into populations as long as there is a positive balance between fitness costs and over-representation. Models have been used to examine parameters that affect this balance but did not take into account biased insertion of TEs to linked sites in the genome. A simulation model was created to examine the impact of insertion bias on TE spread in mosquito populations. TEs that induce no fitness costs are predicted to increase in frequency over a wide range of parameter values but spread is slower for lower levels of transposition and non-local movement. If TEs are costly, high proportions of local movement can slow or halt spread. To function as a robust transgene drive mechanism a TE should replicate and transpose > 10%/insert/generation, induce < 1% fitness cost/insert, and move preferentially to unlinked sites in the genome.

Animals↗

PubMed1992

T cell receptor alpha-chain influences reactivity to Mls-1 in V beta 8.1 transgenic mice.

Most, but not all, V beta 8.1+ T cells respond to M1s-1 and are clonally deleted in the thymus of M1s-1-expressing animals. To formally examine the role of the TCR alpha-chain in reactivity and tolerance to M1s-1, we have analyzed M1s-1 reactivity in a large panel of CD4+ hybridomas generated from TCR V beta 8.1 transgenic mice, that express an identical, potentially M1s-1-reactive beta-chain. The data show that the alpha-chain strongly influences the M1s-1 reactivity of the hybridomas and that the differences in reactivity had relevance for tolerance. Thus, V alpha 11+ hybridiomas were biased toward M1s-1 reactivity and V alpha 11+ T cells were correspondingly absent from the peripheral repertoire of M1s-1-expressing transgenic mice. V alpha 2+ hybridomas, on the other hand, were biased against M1s-1 reactivity, and V alpha 2+ T cells were correspondingly amplified in the M1s-1-expressing transgenic mice. Structural analysis of the alpha-chains revealed that the M1s-1 reactivity of the V alpha 11+ hybridomas segregated precisely with family member, such that V alpha 11.1+ hybridomas were M1s-1-reactive and V alpha 11.3+ hybridomas were not M1s-1-reactive. On the other hand, there was not a clear correlation between family member and M1s-1 reactivity in the V alpha 2+ hybridomas. The hybridomas also showed striking variation in their reactivity to staphylococcal enterotoxin B (SEB), and the SEB reactivity of the V alpha 11+ hybridomas correlated precisely with family member and with M1s-1 reactivity. In contrast, there was not a clear correlation with V alpha 2+ alpha-chain structure and SEB reactivity. Also, there was no correlation between M1s-1 reactivity and SEB reactivity in individual V alpha 2+ hybridomas, suggesting that the recognition of the two superantigens by the same TCR is not equivalent. Taken together, these data define a role for the TCR alpha-chain in superantigen reactivity and T cell tolerance, and provide a structural explanation for the different fates of M1s-1-reactive T cells in normal and transgenic mice.

Amino Acid Sequence↗

PubMed2004

Reinvestigation of an endogenous meiotic drive system in the mosquito, Aedes aegypti (Diptera: Culicidae).

We have initiated efforts to determine the molecular basis for the M(D) meiotic drive system in the mosquito, Aedes aegypti. The effect of the M(D) gene is a highly male-biased sex ratio, but varies depending on the frequency and sensitivity of a susceptible responder m(s) allele. The M(D) system has potential as a mechanism for driving trangenes for pathogen resistance into natural Ae. aegypti populations. Because all previously existing laboratory strains carrying the M(D) gene have been lost, we have selected for a new strain, T37, that carries a strong driver. Matings between T37 males and drive-susceptible m(s) females result in progeny with highly biased sex ratios, wherein only approximately 14.7% females are produced. We discuss the potential for identifying M(D) candidate genes based on comparisons with the well-described Drosophila melanogaster segregation distorter (SD) meiotic drive system and considerations for release of transgenic Ae. aegypti into natural populations where M(D) and insensitive m3 alleles are likely segregating.

Aedes↗

PubMed1999

Selection at multiple checkpoints focuses V(H)12 B cell differentiation toward a single B-1 cell specificity.

Phosphatidyl choline (PtC)-specific B cells segregate to the B-1 subset, where they comprise up to 10% of the B-1 repertoire. About half express V(H)12 and Vkappa4/5H and are restricted in V(H)CDR3. We have previously reported that anti-PtC V(H)CDR3 is enriched among V(H)12-expressing cells by selective elimination of pre-B cells. We report here a bias for Vkappa4/5H expression among V(H)12-expressing B cells, even among those that do not bind PtC and are not B-1. This is due in part to an inability of V(H)12 to associate with many light (L) chains but must also be due to a selective advantage in survival or clonal expansion in the periphery for Vkappa4/5H-expressing cells. Thus, the bias for Vkappa4/5H expression is independent of PtC binding, and, as segregation to B-1 occurs after Ig gene expression, it precedes segregation to the B-1 subset. In 6-1 mice, splenic B-1 cells reside in follicles but segregate to follicles distinct from those that contain B-2 cells. These data indicate that selection at multiple developmental checkpoints ensures the co-expression of an anti-PtC V(H)CDR3 and L chain in a high frequency of V(H)12 B cells. This focus toward specificity for PtC facilitates the development of a large anti-PtC B-1 repertoire.

Amino Acid Sequence↗