Sun X H
Department of Cell Biology, Kaplan Comprehensive Cancer Center New York University Medical Center, New York 10016.
Cell. 1994 Dec 2;79(5):893-900. doi: 10.1016/0092-8674(94)90078-7.
The Id proteins are inhibitors of the basic-helix-loop-helix (bHLH) transcription factors. In the B cell lineage, the Id1 and Id2 genes are expressed in pro-B cells and down-regulated during differentiation. To determine the role of bHLH proteins and the significance of down-regulation of Id genes in B cell development, transgenic mice constitutively expressing the Id1 gene were generated. Their phenotype suggests that B cell development is impaired at an early stage. Primarily, these mice have few B220+ IgM+ mature B or B220+ CD43- pre-B cells in the bone marrow, reduced frequencies of V(D)J and V kappa J kappa recombination of the immunoglobulin loci, and lower expression levels of the immunoglobulin, RAG-1, RAG-2, and lambda 5 genes.
Id蛋白是碱性螺旋-环-螺旋（bHLH）转录因子的抑制剂。在B细胞谱系中，Id1和Id2基因在pro-B细胞中表达，并在分化过程中下调。为了确定bHLH蛋白的作用以及Id基因下调在B细胞发育中的意义，构建了组成型表达Id1基因的转基因小鼠。它们的表型表明B细胞发育在早期受到损害。主要表现为，这些小鼠骨髓中几乎没有B220+IgM+成熟B细胞或B220+CD43-前B细胞，免疫球蛋白基因座的V(D)J和VκJκ重组频率降低，免疫球蛋白、RAG-1、RAG-2和λ5基因的表达水平较低。
