International Mammalian Genome Society

17th International Mouse Genome Conference

9-12 November 2003, Braunschweig, Germany


Webb L S
The Jackson Laboratory

Co-Authors: Gwynn B, Ciciotte S L, Smith R S, Peters L L
Institutions: The Jackson Laboratory

Hermansky-Pudlak Syndrome (HPS) is a genetic disorder characterized by defects in three lysosome-related organelles: melanosomes, lysosomes, and platelet dense bodies. The phenotype of HPS includes oculocutaneous albinism, prolonged bleeding, and lysosomal storage disease. HPS is genetically heterogeneous. Fifteen non-allelic mouse models exist for HPS, six of which have counterparts in the human. Many HPS gene products associate in multiprotein complexes involved in the biogenesis of lysosome-related organelles. An exacerbated phenotype often results from crossing animals bearing mutations that act at different stages of LRO biogenesis or encode components of different complexes.

We set up intercrosses between several mutants to determine genetically if the genes are involved affect the same HPS-related pathways. We utilized cappuccino (cno; Chr 5), reduced pigmentation (rp; Chr 7), and ruby eye (ru, Chr 19), all HPS mouse models, and R26W (Chr 7), a recessive mutation that produces a mosaically expressed pigment dilution. Previous studies show that rp and R26W interact.

We examined the offspring to determine melanocyte defects, and measured bleeding time to assess platelet function. Neither ru and cno nor R26W and cno show genetic interaction. However, ru acts semidominantly to affect melanocyte and platelet function in both rp and R26W. These results suggest rp and R26W function in a complex or pathway different from that affected by the ru mutation. Molecular experiments are currently underway to confirm these genetic results and to further elucidate these HPS-related pathways.

Acknowledgement: LSW is supported by the Judith Graham Pool Postdoctoral Fellowship from the National Hemophilia Foundation.

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