Hermansky-Pudlak syndrome (HPS) is an often-fatal autosomal recessive disease in which albinism, bleeding, and lysosomal storage result from defects of diverse cytoplasmic organelles: melanosomes, platelet dense bodies, and lysosomes. HPS is the most common single-gene disorder in Puerto Rico, with an incidence of 1 in 1,800. We have identified the HPS gene by positional cloning, and found homozygous frameshifts in this gene in Puerto Rican, Swiss, Irish and Japanese HPS patients. The HPS polypeptide is a novel transmembrane protein that is likely to be a component of multiple cytoplasmic organelles and that is apparently crucial for their normal development and function. The different clinical phenotypes associated with the different HPS frameshifts we observed suggests that differentially truncated HPS polypeptides may have somewhat different consequences for subcellular function.

Hermansky-Pudlak syndrome (HPS) is a rare, often fatal, autosomal recessive disorder in which albinism, bleeding and lysosomal storage are associated with defects of diverse cytoplasmic organelles, including melanosomes, platelet dense granules and lysosomes. Similar multi-organellar defects occur in the Chediak-Higashi syndrome (CHS), as well as in a large number of different mouse mutants. The HPS gene is located in 10q23, and two genetically distinct mouse loci, pale ear (ep) and ruby-eye (ru), both with mutant phenotypes similar to human HPS, map close together in the homologous region of murine chromosome 19, suggesting that one of these loci might be homologous to human HPS. We recently identified the human HPS gene, which encodes a novel ubiquitously-expressed transmembrane protein of unknown function. Here, we describe characterization of the mouse Hps cDNA and genomic locus, and identification of pathologic Hps gene mutations in ep but not in ru mice, establishing mouse pale ear as an animal model for human HPS. The phenotype of homozygous ep mutant mice encompasses those of both HPS and CHS, suggesting that these disorders may be closely related. In addition, the mouse and human HPS genes both contain a rare 'AT-AC' intron, and comparison of the sequences of this intron in the mouse and human genes identified conserved sequences that suggest a possible role for pre-mRNA secondary structure in excision of this rare class of introns.

Aflatoxins are potent toxic and carcinogenic compounds, produced by Aspergillus parasiticus and A. flavus as secondary metabolites. In this research, a polyketide synthase gene (pksL1), the key gene for aflatoxin biosynthesis initiation in A. parasiticus, has been functionally identified and molecularly characterized. PCRderived DNA probes were used to find the pksL1 gene from subtracted, aflatoxin-related clones. Gene knockout experiments generated four pksL1 disruptants which lost both the ability to produce aflatoxins B1, B2, and G1 and the ability to accumulate norsolorinic acid and all other intermediates of the aflatoxin biosynthetic pathway. A pksL1 DNA probe detected a 6.6-kb poly(A) ؉ RNA transcript in Northern (RNA) hybridizations. This transcript, associated with aflatoxin production, exhibited a regulated expression that was influenced by growth phase, medium composition, and culture temperature. DNA sequencing of pksL1 revealed an open reading frame for a polypeptide (PKSL1) of 2,109 amino acids. Sequence analysis further recognized four functional domains in PKSL1, acyl carrier protein, ␤-ketoacyl-acyl carrier protein synthase, acyltransferase, and thioesterase, all of which are usually present in polyketide synthases and fatty acid synthases. On the basis of these results, we propose that pksL1 encodes the polyketide synthase which synthesizes the backbone polyketide and initiates aflatoxin biosynthesis. In addition, the transcript of pksL1 exhibited heterogeneity at the polyadenylation site similar to that of plant genes.Aflatoxins (AFs) are a group of polyketide-derived mycotoxins produced by certain strains of Aspergillus parasiticus and A. flavus (10, 27). As with other secondary metabolites, the biosynthesis of AFs occurs at the beginning of and during idiophase when growth of the molds has greatly slowed or stopped, while developmental and chemical differentiation ensue (27). AFB 1 , AFB 2 , AFG 1 , and AFG 2 are the most abundant AFs (20). These toxic and carcinogenic compounds frequently contaminate food and feed commodities (3, 36). A typical AF, AFB 1 for example, is produced by the following generally accepted pathway: acetate building blocks (also hexanoate)3anthrone-derivative polyketide3norsolorinic acid (NA)3averanfin3averufin3hydroxyversicolorine3versiconal hemiacetal acetate3versicolorin B3versicolorin A3sterig-matocystin3o-methylsterigmatocystin3AFB 1 (13,15,27,58). NA is polyketide derived and represents the first stable intermediate in AF biosynthesis (34,37). An unstable anthronederivative polyketide has been proposed as a hypothetical intermediate formed prior to NA, but this theoretical polyketide has not been isolated, presumably because it is rapidly oxidized to NA (27).Genes involved in the initial steps of the pathway are still unknown; their identification and characterization are essential to understanding the initiation of AF biosynthesis (15). In the initial steps of AF biosynthesis, there is predicted to be a polyketide synthase (PKS), but the enzyme has not been is...

Hermansky-Pudlak syndrome (HPS) is an autosomal recessive disorder characterized by oculocutaneous albinism, bleeding tendency, and lysosomal ceroid storage disease, associated with defects of multiple cytoplasmic organelles-melanosomes, platelet-dense granules, and lysosomes. HPS is frequently fatal and is the most common single-gene disorder in Puerto Rico. We previously characterized the human HPS cDNA and identified pathologic mutations in the gene in patients with HPS. The HPS protein is a novel apparent transmembrane polypeptide that seems to be crucial for normal organellar development. Here we describe the structural organization, nucleotide sequence, and polymorphisms of the human HPS gene. The gene consists of 20 exons spanning about 30.5 kb in chromosome segment 10q23.1-q23.3. One of the intervening sequences is a member of the novel, very rare class of so-called "AT-AC" introns, defined by highly atypical 5' and 3' splice site and branch site consensus sequences that provide novel targets for possible pathologic gene mutations. This information provides the basis for molecular analyses of patients with HPS and will greatly facilitate diagnosis and carrier detection of this severe disorder.

Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive disorder in which oculocutaneous albinism, bleeding tendency and a ceroid-lipofuscin lysosomal storage disease result from defects of multiple cytoplasmic organelles: melanosomes, platelet dense granules and lysosomes. The HPS polypeptide, a 700 amino acid protein which is unrelated to any known proteins, is likely to be involved in the biogenesis of these different organelles. Here, we show that HPS is a non-glycosylated, non-membrane protein which is a component of two distinct high molecular weight complexes. In non-melanotic cells the HPS protein is contained almost entirely in an approximately 200 kDa complex that is widely distributed throughout the cytosol. In melanotic cells the HPS protein is partitioned between this cytosolic complex and a >500 kDa complex that appears to consist of the approximately 200 kDa complex in association with membranous components. Subcellular fractionation, immunofluorescence and immunoelectron microscopy studies indicate that the membrane-associated HPS complex of melanotic cells is associated with tubulovesicular structures, small non-coated vesicles, and nascent and early-stage melanosomes. These findings suggest that the HPS complex is involved in the biogenesis of early melanosomes.