Positional cloning studies of a tumor suppressor gene locus at human chromosome 6q26-q27 in B-cell non-Hodgkin's lymphoma

• Main Author: Hauptschein, Robert Scott
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-1998
• Subjects: Genetics; Oncology; Pathology
• ISBN: 0599089873; 9780599089877

Previous cytogenetic studies of multiple human tumor types, including B-cell non-Hodgkin's lymphoma (B-NHL), have reported frequent deletions on the long arm of chromosome 6, suggesting the presence of one or more tumor suppressor genes (TSGs) at this locus. Deletion mapping of a series of B-NHL cases described two independent regions of minimal molecular deletion (RMDs) at 6q25-q27 (RMD-1) and 6q21-6q23 (RMD-2). To facilitate positional cloning of the TSG corresponding to B-NHL RMD-1, a comprehensive physical map including a yeast artificial chromosome contig was constructed across 6q26-q27 encompassing RMD-1. Further loss of constitutional heterozygosity analysis of critical B-NHL cases refined RMD-1 between markers D6S186 and D6S227, including approximately 5-9 Mb. Several approaches were undertaken to examine candidate TSG loci within the large genomic extent of B-NHL RMD-1. First, AF6 was assessed as a candidate TSG and was provisionally excluded in a subset of B-NHL by mutational and functional analyses. Second, a locus at D6S347, demonstrating a putative localized homozygous deletion in a single tumor case, was subjected to a detailed structural molecular characterization. This lesion was defined as a unique interlocus gene conversion-like event, and adjacent genes were also identified. Finally, a consensus region of minimal loss in multiple tumor types (D6S193-D6S297) was recognized internal to B-NHL RMD-1. Using a variety of gene discovery strategies including exon trapping and genomic sequencing, several candidate gene sequences spanning this consensus region were identified and partially characterized. Notably, a novel, alternatively spliced form of the RPS6KA2 gene was cloned which crossed the consensus interval. This gene and the other putative transcriptional units provide a framework for future examination of their potential as TSGs.