A detailed transcriptional map of the chromosome 12p12 tumour suppressor locus

Abstract

Loss of heterozygosity of the short arm of chromosome 12 is a frequent event in a wide range of haematological malignancies and solid tumours. In previous studies, the shortest commonly deleted region was delimited to a 750-kb interval, defined by the markers D12S89 and D12S358, in pre-B acute lymphoblastic leukaemia patients, suggesting the presence of a tumour suppressor locus. Here we report the construction of a transcriptional map that integrates the data obtained by genomic sequence analysis, EST database search, comparative analysis and exon amplification. We identified seven putative transcriptional units as well as six pseudogenes. Four of these candidate genes were already known: ETV6, encoding an ets-like transcription factor, LRP6, a member of the LDL receptor gene family, BCL-G, a recently identified pro-apoptotic gene and MKP-7, encoding a new member of the dual-specificity phosphatase family. The products encoded by the three new genes identified in this study, LOH1CR12, LOH2CR12 and LOH3CR12, have no clear homology to known proteins. The gene predictions were all confirmed by expression analysis using RT ± PCR and Northern blot. This transcriptional map is a crucial step toward the identification of the tumour suppressor gene at 12p12.

Expression mapping at 12p12‐13 in advanced prostate carcinoma

“…While deletion analysis at different tumor sites should be approached with caution, it is interesting that these 3 (BCLG, FLJ10298, DUSP16) also lie within the previously reported leukemia minimal region of deletion. 22 Previous studies confirmed our finding that all 3 genes are expressed in normal prostate, 21 which makes them attractive candidates for a 12p12-13 prostate cancer tumor-suppressor gene (Fig. 2).…”

“…Additional exons have been identified, and it has been hypothesized that additional isoforms may exist; however, they also appear to be expressed only in the testis. 21 Real-time-PCR demonstrated a striking decrease in transcript levels of BCLG in both clinical and cultured prostate carcinomas (Tables III, IV, Fig. 3).…”

“…2). [21][22][23] Two putative genes, LOC121048 and LOC256351, were eliminated from consideration because of lack of corresponding expressed sequences in the NCBI database. Real-time-PCR was used to compare expression levels between normal prostate and xenografts or cell lines.…”

“…Sequencing of representative samples (4 normal prostates, 3 xenografts) revealed that all expressed Bcl-G L , consistent with the previous data demonstrating that only this isoform is expressed in the prostate. 21,34 DUSP16 is a dual-specificity phosphatase that dephosphorylates and thereby inhibits mitogen-activated protein (MAP) kinases. 35,36 DUSP16 has greatest affinity for the MAP kinases Jun N-terminal kinase (JNK) and p38␣/␤ but has less affinity for extracellular signal-regulated kinase (ERK) and p38␥/␦.…”

“…Previous publications and genome sequencing have implicated additional candidate genes within the 12p12-13 region of interest. [21][22][23] Herein, we used deletion mapping to further narrow our region of interest to approximately 500 kb and quantitative real-time PCR to determine relative expression of the 10 candidate genes within the minimal region of deletion.…”