Novel pheochromocytoma susceptibility loci identified by integrative genomics.

Pheochromocytomas are catecholamine-secreting tumors that result from mutations of at least six different genes as components of distinct autosomal dominant disorders. However, there remain familial occurrences of pheochromocytoma without a known genetic defect. We describe here a familial pheochromocytoma syndrome consistent with digenic inheritance identified through a combination of global genomics strategies. Multipoint parametric linkage analysis revealed identical LOD scores of 2.97 for chromosome 2cen and 16p13 loci. A two-locus parametric linkage analysis produced maximum LOD score of 5.16 under a double recessive multiplicative model, suggesting that both loci are required to develop the disease. Allele-specific loss of heterozygosity (LOH) was detected only at the chromosome 2 locus in all tumors from this family, consistent with a tumor suppressor gene. Four additional pheochromocytomas with a similar genetic pattern were identified through transcription profiling and helped refine the chromosome 2 locus. High-density LOH mapping with single nucleotide polymorphism-based array identified a total of 18 of 62 pheochromocytomas with LOH within the chromosome 2 region, which further narrowed down the locus to <2 cM. This finding provides evidence for two novel susceptibility loci for pheochromocytoma and adds a recessive digenic trait to the increasingly broad genetic heterogeneity of these tumors. Similarly, complex traits may also be involved in other familial cancer syndromes.

Genetic analysis of J-virus and Beilong virus using minireplicons.

J-virus (JPV), isolated from wild mice in Australia, and Beilong virus (BeiPV), originally isolated from human mesangial cells in China and subsequently detected in rat mesangial cells, represent a new group of paramyxoviruses which have exceptionally large genomes (>19 kb) and contain more than six transcriptional units. In this study, minireplicons were employed to assess the taxonomic status of JPV and BeiPV. Our results demonstrated that, whilst the genome replication machineries of JPV and BeiPV can be interchanged, they were not functional when exchanged with that of Nipah virus. These studies indicate that JPV and BeiPV are closely related to each other and support the classification of these two viruses into a separate genus. In addition, the minireplicons were also used to demonstrate that these large-genome viruses also comply with the 'rule of six' and that over-expression of the C protein has a detrimental effect on minigenome replication.

Beilong virus, a novel paramyxovirus with the largest genome of non-segmented negative-stranded RNA viruses.

During a subtraction study on gene expression in human kidney mesangial cells (HMCs), cDNA clones with sequence homology to paramyxovirus P, M and F genes were isolated. Subsequent investigation revealed that this particular HMC line was infected with a previously unknown paramyxovirus. Here, we report the isolation and genome characterization of this new virus, now named Beilong virus (BeV). The genome of BeV is 19,212 nucleotides (nt) in length and is the largest among all known members of the order Mononegavirales. The BeV genome contains eight genes in the order 3'-N-P/V/C-M-F-SH-TM-G-L-5'. The SH and TM genes code for a small hydrophobic protein of 76 aa and a transmembrane protein of 254 aa, respectively. The BeV G gene, at 4527 nt, codes for an attachment protein of 734 aa and contains two additional open reading frames (ORFs) in the 3' half of the gene, coding for putative proteins of 299 and 394 aa in length. Although the exact origin of BeV is presently unknown, we provide evidence indicating that BeV was present in a rat mesangial cell line used in the same laboratory prior to the acquisition of the HMC line, suggesting a potential rodent origin for BeV.