POSTER NO: 247

Identification of the mouse ruby-eye-2(ru2) gene, a canidate gene for human Hermansky-Pudlak Syndrome

¹Qing Zhang, ²Wei Li, ¹Edward K. Novak, ²Huayan Chen, ²Yunsao He, ³Bruce A. Roe, ⁴Neal G. Copeland, ⁴Nancy A. Jenkins, ¹Richard T. Swank
¹Roswell Park Cancer Institute, Department of Molecular and Cellular Biology, Buffalo, NY 14263, USA, ²Zhongshan University, Da An Gene Diagnostic Center, Guangzhou, 510089, P.R. China, ³University of Oklahoma, Department of Chemisty and Biochemisty, Norman, Oklahoma 73019, USA, ⁴National Cancer Institute, Mouse Cancer Genetics Program, Frederick, Maryland, 21702, USA

Hermansky-Pudlak syndrome (HPS) is a recessively inherited, genetically heterogeneous, disease with dysfunction of several related subcellular organelles including platelet dense granules, melanosomes and lysosomes. In the mouse, more than 15 naturally occuring hypopigmentation genes including ruby-eye-2 (ru-2) are associated with mutant phenotypes similar to human HPS. Through a large interspecific backcross the critical region of mouse chromosome 7 containing the ru-2 gene was narrowed to 0.2 centiMorgans. Three BACs spanning this region were completely sequenced. Genes within these BACs were analyzed for mutations by sequencing RT-PCR products and by Northern blotting. Obvious pathological mutations within one of these genes were found in all 3 ruby-eye-2-mutant alleles. One ruby-eye-2 allele (ru-2J) contains a 2-bp insertion in exon 18 which predicts a reading frame shift and a truncated protein. The ru-2 gene encodes a ubiquitously expressed transcript specifying a 1126 amino acid protein. The gene is novel and is not found in lower eukaryotes such as yeast. It is 74% identical to the corresponding human protein. Electron microscopic examination of ru2 eyes revealed markedly decreased numbers of melanosomes, with aberrant morphology, within both the retinal pigment epithelium and choroid. These and related findings in other mouse HPS genes recently identified indicated that a novel class of genes has evolved in higher eukaryotes to regulate the production and/or function of specialized subcellular organelles like melanosomes and platelet dense granules.