Disease relevance of CD79B

• Expression of the Ig-associated heterodimer (mb-1 and B29) in Hodgkin's disease [1].
• Aberrations of the B-cell receptor B29 (CD79b) gene in chronic lymphocytic leukemia [2].
• B29 (CD79b) is present in the membrane at a later stage compared to its cytoplasmic expression and found in mature B blasts (B-ALL) that express membrane Ig as it is in normal and leukaemic B lymphocytes [3].
• Jurkat T cells stably expressing micro, kappa, and mb1 efficiently assembled a functional BCR when infected with recombinant vaccinia virus bearing wild-type B29 [4].
• The pattern of methylated CpG ((m)CpG) and C(m)C(A/T)GG B29 promoter methylation observed was similar to that recently reported for epigenetic silencing of an integrated retrovirus [5].

High impact information on CD79B

• The Ig-alpha and Ig-beta proteins form a disulphide-linked alpha/beta heterodimer and are encoded by the mb-1 (ref 9, 10) and B29 genes, respectively [6].
• However, some 20-40% of these B220(+)-CD19- cells also coexpress the NK1.1 surface molecule and do not express genes like VpreB or B29 restricted to the B cell lineage [7].
• We found that efficient transport of IgM to the surface of T cells required coexpression of B29 [8].
• The B29 and mb1 mutations appear at frequencies similar to those of other non-Ig genes but lower than Ig genes [9].
• In contrast, B29 mutations displayed a bimodal distribution resembling the CD95Fas gene, in which promoter distal mutations conferred resistance to apoptosis [9].

Chemical compound and disease context of CD79B

• First-pass hepatic extraction of insulin and hepatic and peripheral contributions to hypoglycemia were compared in conscious dogs during portal infusion of insulin A1, B29 diacetyl insulin, or A1-B29 dodecoyl insulin at 7 and 14 pmol X kg-1 X min-1 [10].

Biological context of CD79B

• The transmembrane forms of all immunoglobulin (Ig) classes are associated with two glycoproteins, mb-1 and B29, that are crucial for signal transduction following antigen binding to the Ig molecule [11].
• Physical linkage of the human growth hormone gene cluster and the CD79b (Ig beta/B29) gene [12].
• Thus, the BCS may function as a tissue-specific LCR or position-dependent insulator specifically countering the influences of the 5' GH LCR and controlling B29 gene expression [13].
• We searched available sequences upstream of the human, mouse, and rat B29 genes and found a highly conserved sequence that fulfills the criteria recently established for non-coding DNA elements potentially involved in gene control [13].
• In the human and rat genomes, the B29 gene is located between the skeletal muscle-specific Na-channel alpha subunit (SCN4A) gene and the pituitary-specific growth hormone (GH-N) gene [13].

Anatomical context of CD79B

• We have investigated the transcription and protein expression of mb-1 and B29 genes during B-cell development [11].
• Transcription and protein expression of mb-1 and B29 genes in human hematopoietic malignancies and cell lines [11].
• B29 transcripts were detectable in these cell samples, but low levels of B29 proteins were only detected in one plasma cell line [11].
• B29 (CD79b) was expressed in the cytoplasm in 65% (15/23) of pre-B-ALL and in 14% (4/28) common-ALL but it was detected in the cell membrane in only three cases of mature B-ALL, being negative in all other B lineage subtypes ALL [3].
• We conclude that association of the four components, Ig-heavy chain (HC) and -light chain (LC), MB-1 and B29, is required and sufficient to permit exit of the BCR complex out of the endoplasmic reticulum (ER) [14].

Associations of CD79B with chemical compounds

• Using bisulfite genomic sequencing we found that in microdissected HRS cells of primary cHL SYK, BOB.1/OBF.1, and CD79B promoters were also hypermethylated [15].
• 4. These results suggested that src-type tyrosine kinases as Fyn and Lyn are responsible for the phosphorylation of MB-1 and B29 heterodimer, but anti-MB-1 stimulation can induce tyrosine phosphorylation reaction mediated by other kinase molecule(s) in the progenitor type cells [16].
• Formalin-fixed paraffin-embedded sections of equine and bovine lymph nodes, spleen, thymus, and Peyer's patches were incubated with monoclonal antibodies to B-lymphocyte markers BLA.36, B29, and mb-1 and T-lymphocyte markers CD3 and CD5 [17].
• By using insulin that has been protected in positions A1 and B29, we have been able to couple the insulin selectively through the B1 amino group to divinyl sulfone-activated agarose [18].
• Secretion of apoBs larger than B29 required the coexpression of MTP and, in the presence of MTP, was oleate-responsive [19].

Regulatory relationships of CD79B

• This differential expression suggests that the B29 gene is insulated or otherwise protected from the regulatory influences of the closely proximal GH LCR [13].
• These observations suggest that B-cell activation induces alternative splicing of mb-1 and B29 transcripts which encode proteins unable to constitute the BCR [20].

Other interactions of CD79B

• CLL cells were identified by 4-color flow cytometric analysis of CD19/CD5/CD79b/CD20 expression in 910 outpatients over 40 years old [21].
• The antigen-recognizing surface membrane-bound immunoglobulin (Ig) molecules on the surface of human and murine B cells are non-covalently associated with a heterodimeric protein complex of Ig-alpha (MB-1) and Ig-beta (B29) [22].
• A flow cytometric assay was developed that can differentiate CLL cells from normal B cells on the basis of their CD19/CD5/CD20/CD79b expression [23].
• Tyrosine phosphorylation of MB-1, B29, and HS1 proteins in human B cells following receptor crosslinking [24].

Analytical, diagnostic and therapeutic context of CD79B

• Sixty human continuous cell lines (35 B-lineage, 11 T-lineage, 11 myeloid-lineage and three non-hematopoietic) and 75 hematopoietic malignancies (55 B-lineage, 12 T-lineage and eight myeloid-lineage), were tested for RNA expression by Northern blotting experiments with the mb-1 pRA3 cDNA probe, and a newly isolated B29 cDNA probe [11].
• Both Oct-1 and Pit-1 bind the B29 3' enhancer in in vitro electrophoretic mobility shift assay and in in vivo chromatin immunoprecipitation analyses [25].
• Two monoclonal antibodies (MoAb) were used in this study by immunocytochemistry and flow cytometry: HM57, against an intracellular epitope of the mb-1(CD79a) chain, and SN8, reacting with an extracellular epitope of B29 (CD79b) [3].
• Genomic Southern blot analysis of human cell lines hybridized with both murine and human B29 cDNAs gives patterns consistent with a single-copy gene occupying a small region of the genomic sequence [26].
• Using human B29 cosmid DNA, we have localized the B29 gene to human chromosome 17q23 via fluorescence in situ hybridization [26].

References