The mbl gene encodes the Ig-α signaling subunit of the B cell antigen receptor and is expressed exclusively in B cells beginning at the very early pro-B cell stage in the bone marrow. We examine here ...the efficacy of the mbl gene as a host locus for cre recombinase expression in B cells. We show that by integrating a humanized cre recombinase into the mbl locus we obtain extraordinarily efficient recombination of IoxP sites in the B cell lineage. The results from a variety of reporter genes including the splicing factor SRp20 and the DNA methylase Dnmtl suggest that mbl-cre is probably the best model so far described for pan-B cell-specific cre expression. The availability of a mouse line with efficient cre-mediated recombination at an early developmental stage in the B lineage provides an opportunity to study the role of various genes specifically in B cell development and function.
Background
Rice (
Oryza sativa
L
.)
is one of the major staple food crops consumed globally. However, rice production is severely affected by high salinity levels, particularly at the seedling stage. ...A good solution would be the development of an efficient screening methodology to identify genotypes possessing genes for salt tolerance.
Result
A new salinity tolerance screening technique using rice seedlings in pot-culture was tested. This method controls soil heterogeneity by using pure sand as a growth medium and minimizes unexpected extreme weather conditions with a movable shelter. Seventy-four rice genotypes were screened at three salinity treatments including high salt stress (electrical conductivity (EC) 12 dSm
− 1
), moderate salt stress (EC 6 dSm
− 1
), and control (no salt stress), imposed 1 week after emergence. Several shoot and root morpho-physiological traits were measured at 37 days after sowing. A wide range of variability was observed among genotypes for measured traits with root traits being identified as the best descriptors for tolerance to salt stress conditions. Salt stress response indices (SSRI) were used to classify the 74 rice genotypes; 7 genotypes (9.46%) were identified as salt sensitive, 27 (36.48%) each as low and moderately salt tolerant, and 13 (17.57%) as highly salt tolerant. Genotypes FED 473 and IR85427 were identified as the most salt tolerant and salt sensitive, respectively. These results were further confirmed by principal component analysis (PCA) for accuracy and reliability.
Conclusion
Although tolerant genotypes still need to be confirmed in field studies and tolerance mechanisms identified at the molecular level, information gained from this study could help rice breeders and other scientists to accelerate breeding by selecting appropriate donor parents, progenies and potential genotypes at early growth stages necessary for salinity tolerance research.
The non-receptor protein tyrosine kinase Syk (spleen tyrosine kinase) is an important mediator of signal transduction in B cells. By acting downstream of the B-cell antigen receptor, Syk promotes ...signaling pathways involved in proliferation, differentiation and survival of B cells. To study the oncogenic potential of Syk, we generated a mouse model for the inducible expression of the leukemia-derived TEL-Syk fusion protein exhibiting constitutive kinase activity. To achieve B-cell-specific expression of TEL-Syk in adult mice, we used a tamoxifen-inducible Cre mouse line. This study shows that inducible expression of TEL-Syk in B cells leads to transient proliferation and subsequent plasma cell differentiation. However, it does not lead to B-cell transformation. Instead, Syk activation induces the tumor suppressor B-lymphocyte-induced maturation protein-1 (Blimp-1), which interferes with the expression of the antiapoptotic protein Bcl-2. Combined induction of TEL-Syk with transgenic expression of Bcl-2 results in a severe phenotype and plasma cell expansion. Our results suggest that deregulated Syk activity by itself is not sufficient for the transformation of B cells, as downstream effectors, such as Blimp-1, limit the survival and expansion of the activated B cell.
Precursor-B-cell receptor (pre-BCR) signaling and spleen tyrosine kinase (SYK) recently were introduced as therapeutic targets for patients with B-cell acute lymphoblastic leukemia (B-ALL), but the ...importance of this pathway in B-ALL subsets and mechanism of downstream signaling have not fully been elucidated. Here, we provide new detailed insight into the mechanism of pre-BCR signaling in B-ALL. We compared the effects of pharmacological and genetic disruption of pre-BCR signaling in vitro and in mouse models for B-ALL, demonstrating exquisite dependency of pre-BCR(+) B-ALL, but not other B-ALL subsets, on this signaling pathway. We demonstrate that SYK, PI3K/AKT, FOXO1 and MYC are important downstream mediators of pre-BCR signaling in B-ALL. Furthermore, we define a characteristic immune phenotype and gene expression signature of pre-BCR(+) ALL to distinguish them from other B-ALL subsets. These data provide comprehensive new insight into pre-BCR signaling in B-ALL and corroborate pre-BCR signaling and SYK as promising new therapeutic targets in pre-BCR(+) B-ALL.
The purpose of this study was the appraisal of the clinical and functional consequences of germline mutations within the gene for the IL-2 inducible T-cell kinase, ITK. Among patients with ...Epstein-Barr virus-driven lymphoproliferative disorders (EBV-LPD), negative for mutations in SH2D1A and XIAP (n=46), we identified two patients with R29H or D500T,F501L,M503X mutations, respectively. Human wild-type (wt) ITK, but none of the mutants, was able to rescue defective calcium flux in murine Itk(-/-) T cells. Pulse-chase experiments showed that ITK mutations lead to varying reductions of protein half-life from 25 to 69% as compared with wt ITK (107 min). The pleckstrin homology domain of wt ITK binds most prominently to phosphatidylinositol monophosphates (PI(3)P, PI(4)P, PI(5)P) and to lesser extend to its double or triple phosphorylated derivates (PIP2, PIP3), interactions which were dramatically reduced in the patient with the ITK(R29H) mutant. ITK mutations are distributed over the entire protein and include missense, nonsense and indel mutations, reminiscent of the situation in its sister kinase in B cells, Bruton's tyrosine kinase.
Drought stress is one of the most devastating abiotic factors limiting plant growth and development. Devising an efficient and rapid screening method at the seedling stage is vital in identifying ...genotypes best suited under drought conditions. An experiment was conducted to assess 74 rice genotypes for drought tolerance using specially designed mini-hoop structures. Two treatments were imposed on rice seedlings, including 100% moisture and a 50% moisture regime. Several shoot morpho-physiological traits and root traits were measured and analyzed. The genotypes exhibited a wide range of variability for the measured traits, with the leaf area showing the most significant variation, followed by plant height, tiller number, and shoot dry weight. In contrast, the drought did not significantly affect most root traits. The germplasm was classified into different categories using cumulative drought stress response indices (CDSRI); 19 genotypes (26%) were identified as drought sensitive, and 33 (45%), 15 (20%), and 7 (9%) were determined as low, moderately, and highly drought-tolerant, respectively. Genotypes IR86638 and IR49830 were the most and least drought-tolerant, respectively. Overall, a poor correlation was observed between CDSRI, total shoot traits (R2 = 0.36), and physiological parameters (R2 = 0.10). A strong linear correlation was found between CDSRI and root traits (R2 = 0.81), suggesting that root traits are more crucial and better descriptors in screening for drought tolerance. This study can help rice breeders and scientists to accelerate breeding by adopting a mini-hoop rapid screening method. The tolerant genotypes could serve as appropriate donor parents, progenies, and potential genotypes for developing drought-tolerant commercial cultivars.
Drought is a major abiotic stress factor affecting the growth and development of plants at all stages. Developing a screening tool for identifying drought stress tolerance during seedling ...establishment is important in the deployment of rice varieties suited to water-limited growing environments. An experiment was conducted to evaluate 100 rice genotypes, mostly belonging to the tropical japonica subspecies, for drought stress tolerance using low-cost, pre-fabricated mini-hoop structures. The rice seedlings were subjected to two different soil moisture regimes- control pots managed at 100% and drought pots at 50% field capacity, from 12 to 30 days after sowing (DAS). Several morpho-physiological parameters including root traits were measured to assess the response of genotypes to drought stress. Significant moisture stress × genotype interactions were found for most of the parameters measured. A cumulative drought stress response index (CDSRI) was developed by adding the individual response indices of all cultivars. Based on CDSRI and standard deviation values, 5 and 28 genotypes were identified as highly sensitive and sensitive to drought, respectively, and 45 as moderately sensitive. On the other hand, 16 and 6 genotypes were classified as tolerant and highly tolerant to drought, respectively. Cheniere, a released cultivar, and RU1402174, an experimental breeding line, were identified as the least and most tolerant to drought among the 100 genotypes tested. Significant linear correlation coefficients were obtained between CDSRI and root growth parameters (R2 = 0.91, n = 100) and CDSRI with shoot growth parameters (R2 = 0.48, n = 100), revealing the importance of root traits in studying and identifying drought tolerant lines during the seedling establishment stages in rice. The tolerant rice genotypes identified will be valuable for rice scientists in studying the mechanism for early season drought as well as for rice breeders for developing new genotypes best suited under growing environments prone to early-season drought.
The main aim of this investigation is to study the combined effect of hot-dry weather conditions on the plastic and drying shrinkage of high performance lightweight aggregate concrete (HPLWAC) ...specimens, along with the other properties including, workability, setting time compressive and splitting strength. The experimental program including the use of fixed mix proportions and was carried out in a typical Iraqi summer day (under actual conditions) of different times during the day. The results indicate that the use of lightweight aggregate play a main role in decreasing the effect of hot dry weather on plastic shrinkage, as well as the plastic shrinkage strain of HPLWC specimens cast at 12:00 pm. less than that of normal weight aggregate concrete specimens by about 36.7%. While drying shrinkage of HPLWC specimens at initial ages up to 7 days was low and it increases with a higher rate at later ages.
SRp20 is a member of the highly conserved SR family of splicing regulators. Using a variety of reporter gene constructs, we show that SRp20 regulates alternative splicing of its own mRNA. ...Overexpression of SRp20 results in a reduction in the level of exon 4‐skipped SRp20 transcripts and activates the production of transcripts containing exon 4. These exon 4‐included transcripts encode a truncated protein lacking the C‐terminal RS domain. We provide evidence that SRp20 probably enhances the recognition of the otherwise unused, weak splice acceptor of exon 4. The recognition of exons with weak splice acceptor sites may be a general activity of SRp20. Unexpectedly, ASF/SF2, another member of the SR family, antagonizes the effect of SRp20 on SRp20 pre‐mRNA splicing and suppresses the production of the exon 4‐included form. Our results indicate that ASF/SF2 suppresses the use of the alternative exon 4, most likely by inhibiting the recognition of the splice donor of exon 4. These results demonstrate, for the first time, an auto‐regulatory activity of an SR protein which is antagonized by a second SR protein.
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