The immunoglobulin heavy chain variable gene segment 4-31, IGHV 4-31, is differentially expressed in the brain and lymph nodes of patients with metastatic breast cancer.

One study reported the incidence of central nervous system metastases in breast cancer patients treated with trastuzumab as 34% (1). We mined published microarray data (2-4) to discover genes associated with brain metastasis in breast cancer. We identified significant differential expression of the immunoglobulin heavy chain variable gene segment IGHV 4-31 in the metastases of patients with metastatic breast cancer, both in the lymph nodes and in the brain. We recently described the differential expression of the immunoglobulin light chain kappa constant locus in the brain metastases of patients with metastatic breast cancer (5). These data suggest both heavy and light chain gene segments may potentially be among the loci whose expression is most significantly altered transcriptome-wide when comparing primary tumors of the breast and brain metastases in patients with metastatic breast cancer. IGHV 4-31 may be relevant to the biology underlying colonization of the brain with metastatic breast cancer clones.

Regulation of TCR δ and α repertoires by local and long-distance control of variable gene segment chromatin structure

Murine Tcrd and Tcra gene segments reside in a single genetic locus and undergo recombination in CD4−CD8− (double negative [DN]) and CD4+CD8+ (double positive [DP]) thymocytes, respectively. TcraTcrd locus variable gene segments are subject to complex regulation. Only a small subset of ∼100 variable gene segments contributes substantially to the adult TCRδ repertoire. Moreover, although most contribute to the TCRα repertoire, variable gene segments that are Jα proximal are preferentially used during primary Tcra recombination. We investigate the role of local chromatin accessibility in determining the developmental pattern of TcraTcrd locus variable gene segment recombination. We find variable gene segments to be heterogeneous with respect to acetylation of histones H3 and H4. Those that dominate the adult TCRδ repertoire are hyperacetylated in DN thymocytes, independent of their position in the locus. Moreover, proximal variable gene segments show dramatic increases in histone acetylation and germline transcription in DP thymocytes, a result of super long-distance regulation by the Tcra enhancer. Our results imply that differences in chromatin accessibility contribute to biases in TcraTcrd locus variable gene segment recombination in DN and DP thymocytes and extend the distance over which the Tcra enhancer can regulate chromatin structure to a remarkable 525 kb.

Evidence that Immunoglobulin VH-DJ Recombination Does Not Require Germ Line Transcription of the Recombining Variable Gene Segment

ABSTRACT The importance of V(D)J recombination for generating diversity in the immune system is well established, but the mechanisms which regulate V(D)J recombination are still poorly understood. Although transcription of unrearranged (germ line) immunoglobulin and T-cell receptor gene segments often precedes V(D)J recombination and has been implicated in its control, the actual role of germ line transcripts in V(D)J recombination is not known. We used a sensitive reverse transcription-PCR assay to study immunoglobulin VH germ line transcripts in proB lines from RAG-deficient mice. All 10 VH families analyzed were germ line transcribed, and germ line transcription was found in all of the cell lines examined, indicating that active chromatin was present in the VHregion. However, not all VH families were germ line transcribed in every cell line, and there was a surprising lack of uniformity in the number and family distribution of germ line VH transcripts in individual lines. When V(D)J recombination was activated by restoration of RAG activity, recombinational activity of endogenous VH genes for which germ line transcription was observed could be compared with those of genes for which it was not observed. This analysis revealed multiple examples of endogenous VH gene segments which were rearranged in cells where their germ line transcription was not detectable prior to RAG expression. Thus, our data provide strong support for the idea that V-(D)J recombination does not require germ line transcription of the recombining variable gene segment.