Bruton's tyrosine kinase (Btk) is a nonreceptor tyrosine kinase involved in precursor B (pre-... more Bruton's tyrosine kinase (Btk) is a nonreceptor tyrosine kinase involved in precursor B (pre-B) cell receptor signaling. Here we demonstrate that Btk-deficient mice have an ∼50% reduction in the frequency of immunoglobulin (Ig) λ light chain expression, already at the immature B cell stage in the bone marrow. Conversely, transgenic mice expressing the activated mutant BtkE41K showed increased λ usage. As the κ/λ ratio is dependent on (a) the level and kinetics of κ and λ locus activation, (b) the life span of pre-B cells, and (c) the extent of receptor editing, we analyzed the role of Btk in these processes. Enforced expression of the Bcl-2 apoptosis inhibitor did not alter the Btk dependence of λ usage. Crossing 3-83μδ autoantibody transgenic mice into Btk-deficient mice showed that Btk is not essential for receptor editing. Also, Btk-deficient surface Ig+ B cells that were generated in vitro in interleukin 7-driven bone marrow cultures manifested reduced λ usage. An intrinsic ...
Journal of immunology (Baltimore, Md. : 1950), 1999
Bruton's tyrosine kinase (Btk) is a nonreceptor protein kinase that is defective in X-linked ... more Bruton's tyrosine kinase (Btk) is a nonreceptor protein kinase that is defective in X-linked agammaglobulinemia in humans and in X-linked immunodeficiency in mice. To study the effect of Btk activation in early B cell development in vivo, we have created transgenic mouse strains expressing Btk under the control of the human CD19 promoter region. The transgenic expression of wild-type human Btk corrected all X-linked immunodeficiency features in mice carrying a targeted disruption of the Btk gene. In contrast, expression of an activated form of Btk, the E41K mutant, resulted in an almost complete arrest of B cell development in the immature IgM+IgD- B cell stage in the bone marrow, irrespective of the presence of the endogenous intact Btk gene. Immature B cells were arrested at the progression from IgMlow into IgMhigh cells, which reflects the first immune tolerance checkpoint at which autoreactive B cells become susceptible to apoptosis. As the constitutive activation of Btk is ...
The iroA gene product is an iron limitation-inducible outer membrane protein of Neisseria meningi... more The iroA gene product is an iron limitation-inducible outer membrane protein of Neisseria meningitidis. A spontaneous mutant lacking the gene was unable to bind lactoferrin. Furthermore, Escherichia coli strains expressing the IroA protein were capable of binding lactoferrin. Apparently, the IroA protein functions as a lactoferrin receptor.
Germ line gene transposition technology has been used to generate "libraries" of flies ... more Germ line gene transposition technology has been used to generate "libraries" of flies and worms carrying genomewide mutations. Phenotypic screening and DNA sequencing of such libraries provide functional information resulting from insertional events in target genes. There is also a great need to have a fast and efficient way to generate mouse mutants in vivo to model developmental defects and human diseases. Here we describe an optimized mammalian germ line transposition system active during early mouse spermatogenesis using the Minos transposon. Transposon-positive progeny carry on average more than 2 new transpositions, and 45 to 100% of the progeny carry an insertion in a gene. The optimized Minos-based system was tested in a small rapid dominant functional screen to identify mutated genes likely to cause measurable cardiovascular "disease" phenotypes in progeny/embryos. Importantly this system allows rapid screening for modifier genes.
The use of genetically-modified (GM) animals as research models continues to grow. The completion... more The use of genetically-modified (GM) animals as research models continues to grow. The completion of the mouse genome sequence, together with the high-throughput international effort to introduce mutations across the mouse genome in the embryonic stem (ES) cells ( www.knockoutmouse.org ) facilitates an efficient way to obtain mutated mouse strains as research models. The increasing number of available mutated mouse strains and their combinations, together with the increasing complexity in the targeting approaches used, reinforces the need for guidelines that will provide information about the mouse strains and the robust and reliable methods used for their genotyping. This information, however, should be obtained with a method causing minimal discomfort to the experimental animals. We have, therefore, compiled the present document which summarizes the currently available methods for obtaining genotype information. It provides updated guidelines concerning animal identification, DNA ...
The simian virus 40 (SV40) T antigen is a potent oncogene able to transform many cell types and h... more The simian virus 40 (SV40) T antigen is a potent oncogene able to transform many cell types and has been implicated in leukemia and lymphoma. In this report, we have achieved sporadic SV40 T-antigen expression in mature B cells in mice, by insertion of a SV40 T antigen gene in opposite transcriptional orientation in the immunoglobulin (Ig) heavy (H) chain locus between the D and J(H) segments. SV40 T-antigen expression appeared to result from retention of the targeted germline allele and concomitant antisense transcription of SV40 large T in mature B cells, leading to chronic lymphocytic leukemia (CLL). Although B-cell development was unperturbed in young mice, aging mice showed accumulation of a monoclonal B-cell population in which the targeted IgH allele was in germline configuration and the wild-type IgH allele had a productive V(D)J recombination. These leukemic B cells were IgD(low)CD5(+) and manifested nonrandom usage of V, D, and J segments. V(H) regions were either unmutated, with preferential usage of the VH11 family, or manifested extensive somatic hypermutation. Our findings provide an animal model for B-CLL and show that pathways activated by SV40 T antigen play important roles in the pathogenesis of B-CLL.
Bruton's tyrosine kinase (Btk) is a nonreceptor tyrosine kinase involved in precursor B (pre-... more Bruton's tyrosine kinase (Btk) is a nonreceptor tyrosine kinase involved in precursor B (pre-B) cell receptor signaling. Here we demonstrate that Btk-deficient mice have an ∼50% reduction in the frequency of immunoglobulin (Ig) λ light chain expression, already at the immature B cell stage in the bone marrow. Conversely, transgenic mice expressing the activated mutant BtkE41K showed increased λ usage. As the κ/λ ratio is dependent on (a) the level and kinetics of κ and λ locus activation, (b) the life span of pre-B cells, and (c) the extent of receptor editing, we analyzed the role of Btk in these processes. Enforced expression of the Bcl-2 apoptosis inhibitor did not alter the Btk dependence of λ usage. Crossing 3-83μδ autoantibody transgenic mice into Btk-deficient mice showed that Btk is not essential for receptor editing. Also, Btk-deficient surface Ig+ B cells that were generated in vitro in interleukin 7-driven bone marrow cultures manifested reduced λ usage. An intrinsic ...
Journal of immunology (Baltimore, Md. : 1950), 1999
Bruton's tyrosine kinase (Btk) is a nonreceptor protein kinase that is defective in X-linked ... more Bruton's tyrosine kinase (Btk) is a nonreceptor protein kinase that is defective in X-linked agammaglobulinemia in humans and in X-linked immunodeficiency in mice. To study the effect of Btk activation in early B cell development in vivo, we have created transgenic mouse strains expressing Btk under the control of the human CD19 promoter region. The transgenic expression of wild-type human Btk corrected all X-linked immunodeficiency features in mice carrying a targeted disruption of the Btk gene. In contrast, expression of an activated form of Btk, the E41K mutant, resulted in an almost complete arrest of B cell development in the immature IgM+IgD- B cell stage in the bone marrow, irrespective of the presence of the endogenous intact Btk gene. Immature B cells were arrested at the progression from IgMlow into IgMhigh cells, which reflects the first immune tolerance checkpoint at which autoreactive B cells become susceptible to apoptosis. As the constitutive activation of Btk is ...
The iroA gene product is an iron limitation-inducible outer membrane protein of Neisseria meningi... more The iroA gene product is an iron limitation-inducible outer membrane protein of Neisseria meningitidis. A spontaneous mutant lacking the gene was unable to bind lactoferrin. Furthermore, Escherichia coli strains expressing the IroA protein were capable of binding lactoferrin. Apparently, the IroA protein functions as a lactoferrin receptor.
Germ line gene transposition technology has been used to generate "libraries" of flies ... more Germ line gene transposition technology has been used to generate "libraries" of flies and worms carrying genomewide mutations. Phenotypic screening and DNA sequencing of such libraries provide functional information resulting from insertional events in target genes. There is also a great need to have a fast and efficient way to generate mouse mutants in vivo to model developmental defects and human diseases. Here we describe an optimized mammalian germ line transposition system active during early mouse spermatogenesis using the Minos transposon. Transposon-positive progeny carry on average more than 2 new transpositions, and 45 to 100% of the progeny carry an insertion in a gene. The optimized Minos-based system was tested in a small rapid dominant functional screen to identify mutated genes likely to cause measurable cardiovascular "disease" phenotypes in progeny/embryos. Importantly this system allows rapid screening for modifier genes.
The use of genetically-modified (GM) animals as research models continues to grow. The completion... more The use of genetically-modified (GM) animals as research models continues to grow. The completion of the mouse genome sequence, together with the high-throughput international effort to introduce mutations across the mouse genome in the embryonic stem (ES) cells ( www.knockoutmouse.org ) facilitates an efficient way to obtain mutated mouse strains as research models. The increasing number of available mutated mouse strains and their combinations, together with the increasing complexity in the targeting approaches used, reinforces the need for guidelines that will provide information about the mouse strains and the robust and reliable methods used for their genotyping. This information, however, should be obtained with a method causing minimal discomfort to the experimental animals. We have, therefore, compiled the present document which summarizes the currently available methods for obtaining genotype information. It provides updated guidelines concerning animal identification, DNA ...
The simian virus 40 (SV40) T antigen is a potent oncogene able to transform many cell types and h... more The simian virus 40 (SV40) T antigen is a potent oncogene able to transform many cell types and has been implicated in leukemia and lymphoma. In this report, we have achieved sporadic SV40 T-antigen expression in mature B cells in mice, by insertion of a SV40 T antigen gene in opposite transcriptional orientation in the immunoglobulin (Ig) heavy (H) chain locus between the D and J(H) segments. SV40 T-antigen expression appeared to result from retention of the targeted germline allele and concomitant antisense transcription of SV40 large T in mature B cells, leading to chronic lymphocytic leukemia (CLL). Although B-cell development was unperturbed in young mice, aging mice showed accumulation of a monoclonal B-cell population in which the targeted IgH allele was in germline configuration and the wild-type IgH allele had a productive V(D)J recombination. These leukemic B cells were IgD(low)CD5(+) and manifested nonrandom usage of V, D, and J segments. V(H) regions were either unmutated, with preferential usage of the VH11 family, or manifested extensive somatic hypermutation. Our findings provide an animal model for B-CLL and show that pathways activated by SV40 T antigen play important roles in the pathogenesis of B-CLL.
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Papers by A. Maas