Rag1 and Rag2 are required for the somatic rearrangement of immunoglobulin genes and T-cell receptor genes and the subsequent development of B and T cells. We describe the pattern of DNase I hypersensitive sites surrounding the Rag1 gene that accompanies mouse B-cell development and show that one of these sites corresponds to the murine Rag1 promoter. Transcription initiates over a 30 bp region, with approximately 70% of the transcripts initiating within a 5 bp region. The promoter contains neither a consensus TATA box nor an initiator, but does contain an AT rich sequence that could serve as a non-consensus TATA box. The Rag1 promoter directs only negligible levels of expression in transient transfection assays, but when combined with a heterologous enhancer, it is capable of driving significant levels of expression in pre-B cells, pre-T cells, and mature B cells. Methylation interference and mutation analysis reveal that the Rag1 promoter contains binding sites for E-box binding proteins, NF-Y proteins, and Ikaros proteins. These findings are discussed with respect to B-cell development and regulation of differential Rag expression by the promoter in pre-B, pre-T, and CNS cells.

Animals↗

PubMedDate not supplied

Expression of a microinjected immunoglobulin gene in the spleen of transgenic mice.

Transgenic mice were produced by microinjection of a rearranged, functional immunoglobulin kappa gene into fertilized mouse eggs and implantation of the microinjected embryos into foster mothers. Mice that integrated the injected gene were mated and the DNA, RNA and serum kappa chains of their offspring were analysed. The data from offspring of three different transgenic mice indicate that the microinjected gene is expressed in the spleen, but not the liver of mice which inherited the injected gene.

Animals↗

PubMedDate not supplied

High expression of cloned immunoglobulin kappa gene in transgenic mice is restricted to B lymphocytes.

Immunoglobulin genes are normally expressed only in cells of the B lymphocyte lineage after a variable (V) and constant (C) gene rearrangement has occurred. To study the control of immunoglobulin gene expression in a defined situation, we have produced transgenic mice by microinjecting a rearranged mouse immunoglobulin kappa gene (designated pB1-14) into fertilized mouse eggs. We present here the analysis of six different kappa-transgenic mouse lines. All the transgenic mice express the microinjected kappa gene in a completely tissue-specific fashion. Transcripts from pB1-14 are found at a high level in the spleen, but are undetectable in nonlymphoid tissues of testis, liver, kidney, heart, muscle, brain and thyroid gland. In lymphoid cell subpopulations, the level of pB1-14 transcripts is correlated with the relative number of B cells; there is no correlation with the proportion of T lymphocytes. We concluded, therefore, that the microinjected kappa gene contains target sequences for B lymphocyte-specific gene activation signals that override the influence of the integration site.

Animals↗

PubMedDate not supplied

Allelic exclusion and control of endogenous immunoglobulin gene rearrangement in kappa transgenic mice.

Hybridomas were produced from spleen cells of kappa transgenic mice to investigate expression of the transgenic kappa gene, its effect on allelic exclusion and its effect on the control of light-chain gene rearrangement and expression. Our results show that the transgene is expressed normally and that the production of a complete immunoglobulin molecule turns off light-chain gene rearrangement.

Alleles↗