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PubMed1993

Hermansky-Pudlak syndrome in a Swiss population.

Tyrosinase-positive albinism, previously diagnosed as Hermansky-Pudlak Syndrome (HPS), has been examined in four generations from a village of the canton Valais, Switzerland. Homozygotes, obligate heterozygotes and putative heterozygotes in this geneology yielded lower than normal membrane-associated thioredoxin reductase (TR) activities compared with normal family members and controls. All of the homozygotes and 50% of each the obligate and putative heterozygotes showed an increase in bleeding time associated with storage-pool-deficient platelets lacking dense bodies. The TR activity profile and the platelet-dense body deficiency in the Swiss albinos was the same as that in the HPS population from Puerto Rico. However, in albinos from Puerto Rico, there is an accumulation of ceroid/lipofuscin-like pigment in lysosomal structures causing tissue damage, and, upon kidney involvement, this leads to increased urinary dolichol excretion. Approximately half of the Puerto Rican HPS cases had clinical evidence of storage disease with restrictive lung disease, granulomatous colitis, kidney failure and cardiomyopathy. By comparison, the Swiss HPS geneology had a normal life expectancy with no significant evidence for ceroid accumulation or urinary dolichol excretion. An examination of antioxidant enzymes, catalase, TR and glutathione reductase in epidermal suction blisters from Swiss HPS homozygotes showed a similar result for catalase and TR levels to the depigmented epidermis of patients with vitiligo, except that intracellular TR was found to be calcium free in HPS compared with vitiligo. Intracellular glutathione reductase levels were highest in HPS. Both the Swiss and Puerto Rican HPS homozygotes and heterozygotes have giant melanosomes in skin melanocytes.

Adolescent↗
PubMed1990

The RIIIS/J inbred mouse strain as a model for von Willebrand disease.

Mice of the RIIIS/J inbred strain have prolonged bleeding times (greater than 15 minutes) after experimental injury when compared with normal C57BL/6J mice (1.8 minutes) and other strains of mice. The prolonged bleeding time was accompanied by normal platelet counts. Platelet aggregation with collagen and agglutination with ristocetin were not significantly altered in RIIIS/J mice. Also, platelets from RIIIS/J mice had normal serotonin content and normal numbers of dense granules by electron microscopy. Thus, the bleeding abnormality is not due to platelet storage pool deficiency as has been found in several other mouse mutants. The activated partial thromboplastin time (APTT) which plasma from RIIIS/J mice was prolonged compared with normal mice, and factor VIII:C activity and von Willebrand antigen levels were one half to one third that of normal mouse plasma. Factor XI activity was also significantly deficient (levels at 42% to 64% of normal). Plasma of RIIIS/J mice contained the full complement of multimers of von Willebrand factor, although each multimer was lower in concentration compared with that in normal mice. Platelet alpha-granule von Willebrand antigen levels were similar to those of normal mice. The prolonged bleeding time of RIIIS/J mice was corrected by treatment with desmopressin. Heterozygous C57BL/6J x RIIIS/J F1 animals had low plasma von Willebrand antigen levels like the RIIIS/J parent and had variable bleeding times. Inheritance of the bleeding tendency was as an incomplete dominant, autosomal trait. These data indicate the RIIIS/J strain is a suitable animal model for type IA von Willebrand disease.

Animals↗
PubMed1999

Dermatologic manifestations of Hermansky-Pudlak syndrome in patients with and without a 16-base pair duplication in the HPS1 gene.

BACKGROUND: Hermansky-Pudlak syndrome (HPS) consists of oculocutaneous albinism, a platelet storage pool deficiency, and lysosomal accumulation of ceroid lipofuscin. Patients with HPS from northwest Puerto Rico are homozygous for a 16-base pair (bp) duplication in exon 15 of HPS1, a gene on chromosome 10q23 known to cause the disorder. OBJECTIVE: To determine the dermatologic findings of patients with HPS. DESIGN: Survey of inpatients with HPS by physical examination. SETTING: National Institutes of Health Clinical Center, Bethesda, Md (a tertiary referral hospital). PATIENTS: Sixty-five patients aged 3 to 54 years were diagnosed on the basis of the absence of platelet dense bodies in individuals with albinism and a bleeding diathesis. The presence of a 16-bp duplication in HPS1 was determined by polymerase chain reaction amplification; 40 patients were homozygous for the duplication and 25 lacked the duplication. All patients with the duplication were from northwest Puerto Rico; all patients without the duplication were non-Puerto Rican except 4 from central Puerto Rico. RESULTS: Both patients homozygous for the 16-bp duplication and patients without the duplication displayed skin color ranging from white to light brown. Patients with the duplication, as well as those lacking the duplication, had hair color ranging from white to brown and eye color ranging from blue to brown. New findings in both groups of patients with HPS were melanocytic nevi with dysplastic features, acanthosis nigricans-like lesions in the axilla and neck, and trichomegaly. Eighty percent of patients with the duplication exhibited features of solar damage, including multiple freckles, stellate lentigines, actinic keratoses, and, occasionally, basal cell or squamous cell carcinomas. Only 8% of patients lacking the 16-bp duplication displayed these findings. As a group, the patients with the duplication lived closer to the equator than those without the duplication. CONCLUSION: Patients with HPS exhibit wide variation in pigmentation and dermatologic findings.

Adolescent↗
PubMed2006

Platelets and platelet adhesion support angiogenesis while preventing excessive hemorrhage.

Platelets contain both pro- and antiangiogenic factors, but their regulatory role in angiogenesis is poorly understood. Although previous studies showed that platelets stimulate angiogenesis in vitro, the role of platelets in angiogenesis in vivo is largely uncharacterized. To address this topic, we used two in vivo approaches, the cornea micropocket assay and the Matrigel model, in four animal models: thrombocytopenic, Lyst(bg) (platelet storage pool deficiency), glycoprotein (GP) Ibalpha/IL4R transgenic (lacking extracellular GPIbalpha, the receptor for von Willebrand factor as well as other adhesive and procoagulant proteins), and FcgammaR(-/-) (lacking functional GPVI, the collagen receptor) mice. Adult mice were rendered thrombocytopenic by i.p. administration of an antiplatelet antibody. The number of growing vessels in the thrombocytopenic mice was lower in the cornea assay, and they showed significantly increased appearance of hemorrhage compared with mice treated with control IgG. The thrombocytopenic mice also showed more protein leakage and developed hematomas in the Matrigel model. GPIbalpha/IL4R transgenic mice presented increased hemorrhage in both assays, but it was less severe than in the platelet-depleted mice. FcgammaR(-/-) and Lyst(bg) mice showed no defect in experimental angiogenesis. Intravital microscopy revealed a >3-fold increase in platelet adhesion to angiogenic vessels of Matrigel compared with mature quiescent skin vessels. Our results suggest that the presence of platelets not only stimulates angiogenic vessel growth but also plays a critical role in preventing hemorrhage from the angiogenic vessels. The adhesion function of platelets, as mediated by GPIbalpha, significantly contributes to the process.

Animals↗
PubMed2001

Hermansky-Pudlak syndrome and Chediak-Higashi syndrome: disorders of vesicle formation and trafficking.

The rare autosomal recessive metabolic disorders Hermanky-Pudlak syndrome (HPS) and Chediak-Higashi syndrome (CHS)share the clinical findings of oculocutaneous albinism and a platelet storage pool deficiency. In addition, HPS exhibits ceroid lipofuscinosis and CHS is characterized by infections and an accelerated phase. The two disorders result from defects in vesicles of lysosomal lineage. Of the two known HPS-causing genes, HPS1 has no recognizable function, while ADTB3A codes for a subunit of an adaptor complex responsible for new vesicle formation from the trans-Golgi network. Other HPS-causing genes are likely to exist. The only known CHS-causing gene, LYST, codes for a large protein of unknown function. In general, HPS appears to be a disorder of vesicle formation and CHS a defect in vesicle trafficking. These diseases and their variants mirror a group of mouse hypopigmentation mutants. The gene productsinvolved will reveal how the melanosome, platelet dense body, and lysosome are formed and trafficked within cells.

Animals↗
PubMed1988

Pulmonary artery pressure in rats with hereditary platelet function defect.

Pulmonary vasoactivity of several biochemical components produced or stored in platelet was the justification for the study of pulmonary artery pressure in fawn-hooded rats (FHR) with hereditary platelet storage pool deficiency. Anesthetized (pentobarbital 35 mg kg-1 i.p.) FHR had higher right ventricular systolic pressure compared with normal Wistar rats (NWR) matched in sex and age (57.7 +/- 6.8 vs. 34.8 +/- 1.2 mm Hg; p less than 0.01). The incidence of higher pulmonary artery pressure (greater than means + 2 SD of NWR) was 68% among FHR. A significant difference was recorded between FHR and NWR in the relative weight of the right ventricle (0.092 +/- 0.021 vs. 0.048 +/- 0.001 g/100 g; p less than 0.05). Rise in pulmonary artery pressure in FHR after 4 weeks of normobaric hypoxia was found to be comparable to that seen posthypoxically in NWR. Morphological consequences of pulmonary hypertension, ranging from moderate medial hypertrophy of small arteries to muscularization of pulmonary arterioles, were recorded in about 50% of FHR with increased pulmonary artery pressure.

Animals↗
PubMed2004

Identification of snapin and three novel proteins (BLOS1, BLOS2, and BLOS3/reduced pigmentation) as subunits of biogenesis of lysosome-related organelles complex-1 (BLOC-1).

Biogenesis of lysosome-related organelles complex-1 (BLOC-1) is a ubiquitously expressed multisubunit protein complex required for the normal biogenesis of specialized organelles of the endosomal-lysosomal system, such as melanosomes and platelet dense granules. The complex is known to contain the coiled-coil-forming proteins, Pallidin, Muted, Cappuccino, and Dysbindin. The genes encoding these proteins are defective in inbred mouse strains that serve as models of Hermansky-Pudlak syndrome (HPS), a genetic disorder characterized by hypopigmentation and platelet storage pool deficiency. In addition, mutation of human Dysbindin causes HPS type 7. Here, we report the identification of another four subunits of the complex. One is Snapin, a coiled-coil-forming protein previously characterized as a binding partner of synaptosomal-associated proteins 25 and 23 and implicated in the regulation of membrane fusion events. The other three are previously uncharacterized proteins, which we named BLOC subunits 1, 2, and 3 (BLOS1, -2, and -3). Using specific antibodies to detect endogenous proteins from human and mouse cells, we found that Snapin, BLOS1, BLOS2, and BLOS3 co-immunoprecipitate, and co-fractionate upon size exclusion chromatography, with previously known BLOC-1 subunits. Furthermore, steady-state levels of the four proteins are significantly reduced in cells from pallid mice, which carry a mutation in Pallidin and display secondary loss of other BLOC-1 subunits. Yeast two-hybrid analyses suggest a network of binary interactions involving all of the previously known and newly identified subunits. Interestingly, the HPS mouse model strain, reduced pigmentation, carries a nonsense mutation in the gene encoding BLOS3. As judged from size exclusion chromatographic analyses, the reduced pigmentation mutation affects BLOC-1 assembly less severely than the pallid mutation. Mutations in the human genes encoding Snapin and the BLOS proteins could underlie novel forms of HPS.

Animals↗
PubMed1989

Chediak-Higashi syndrome: prenatal diagnosis by fetal blood examination in the feline model of the disease.

Chediak-Higashi syndrome (CHS) is an autosomal recessive disease of humans, mink, cattle, mice, killer whales, cats, and blue and silver foxes. The disease is characterized by incomplete oculocutaneous albinism, recurrent and severe pyogenic infections, a bleeding tendency secondary to a platelet storage pool deficiency, and enlarged granules in many types of cells. Humans with CHS usually die during childhood. It has been suggested that the prenatal diagnosis of CHS should be possible by the demonstration of enlarged granules in neutrophils of fetal blood. We tested this hypothesis using 20 cat fetuses obtained 18 days at prepartum. Two litters (6 fetuses) were from CHS to CHS matings and four litters (14 fetuses) were from CHS male to heterozygous female matings. Fetuses were identified as CHS or phenotypically normal by histologic examination of the size of melanin granules in the ciliary body and by the size of periodic acid-Schiff-positive granules in renal tubular epithelial cells. The diameter of the peroxidase-positive granules in neutrophils of the 15 CHS fetuses ranged from 0.3 to 3.0 microns whereas those of the five normal fetuses ranged from 0.3 to 1.0 micron. All 20 fetuses were correctly classified as CHS or phenotypically normal. These data indicate that examination of the size of fetal blood neutrophil granules can be used to diagnose CHS prenatally.

Animals↗
PubMed2003

Genetic and phenotypic analysis of the mouse mutant mh2J, an Ap3d allele caused by IAP element insertion.

Mocha (mh), a mouse model for Hermansky-Pudlak syndrome (HPS), is characterized by platelet storage pool deficiency, pigment dilution, and deafness as well as neurological abnormalities. The trans-Golgi/endosome adaptor-related complex AP-3 is missing in mh mice owing to a deletion in the gene encoding the delta subunit. Mice mutant for a second allele, mh(2J), are as hyperactive as mh, and display both spike wave absence and generalized tonic clonic seizures, but have less coat color dilution, no hearing loss, and no hypersynchronized EEG. Here we show that the mh(2J) mutation is due to an IAP element insertion in the Ap3d gene leading to a C-terminally truncated protein. Despite correct assembly of the AP-3 complex and localization to the trans-Golgi network and endosomes, AP-3 function in neurons remains impaired. While mh mice show a severe reduction of vesicular zinc (TIMM staining) owing to mislocalization and degradation of the Zinc transporter ZnT-3, the TIMM and ZnT-3 staining patterns in mh(2J) varies, with normal expression in hippocampal mossy fibers, but abnormal patterns in neocortex. These results indicate that the N-terminal portion of the delta subunit is sufficient for AP-3 complex assembly and subcellular localization to the TGN/endosomes, while subsequent function is regulated in part by cell-specific interactions with the C-terminal portion.

Animals↗
PubMed2003

Hermansky-Pudlak syndrome type 4 (HPS-4): clinical and molecular characteristics.

Hermansky-Pudlak syndrome (HPS) is an autosomal recessive disorder of oculocutaneous albinism and bleeding attributable to storage-pool-deficient platelets. Although at least 14 mouse models of HPS exist, the human disorders that comprise HPS, i.e., HPS-1, HPS-2, HPS-3, and HPS-4, are recognized to result from mutations in four genes, viz., HPS1, ADTB3A, HPS3, and HPS4, respectively. To characterize further the recently identified HPS-4 disease on molecular and clinical grounds, we first identified the genomic organization of HPS4, located on chromosome 22q11.2-q12.2, including its intron/exon boundaries. We found that HPS4 produces at least two alternatively spliced mRNA transcripts that differ at their 5'-ends. Next, we performed an extensive analysis of 22 unassigned HPS patients (i.e., not having HPS-1, HPS-2, or HPS-3 disease). Using single-strand conformation polymorphism, we determined that seven of the 22 patients had HPS-4. In these seven individuals, we identified five different HPS4 mutations, including one frameshift insertion, one missense, and three nonsense mutations. Three alleles in two patients contained the previously reported Q698insAAGCA frameshift. Three HPS4 mutations were newly described. Four alleles in three patients contained R217X, and two siblings were compound heterozygotes for E138X and E222X. Clinically, our HPS-4 patients exhibited iris transillumination, variable hair and skin pigmentation, absent platelet dense bodies, and occasional pulmonary fibrosis and granulomatous colitis, a severe phenotype similar to that of patients with HPS-1.

Adolescent↗
PubMed2000

Characterization of a partial pseudogene homologous to the Hermansky-Pudlak syndrome gene HPS-1; relevance for mutation detection.

The HPS-1 gene is the first gene found to be responsible for the autosomal recessive disorder Hermansky-Pudlak syndrome (HPS). HPS is characterized by oculocutaneous albinism, a platelet storage pool deficiency, and ceroid lipofuscinosis. The HPS-1 gene has been mapped to chromosome 10q23.1-23.3 and encodes a 79-kDa protein of unknown function with no homology to any known protein. A sequence database search has revealed that a portion of clone HS 1119A7 shows high sequence similarity to HPS-1 cDNA. By performing sequence alignments and PCR amplification of cDNA from several human tissues, we have shown that part of this clone consists of an unprocessed partial HPS-1 pseudogene located on chromosome 22q12.2-12.3. The pseudogene contains several intact HPS-1 exons and shows 95% sequence homology to the HPS-1 cDNA. Exon 6 of the pseudogene has 100% sequence homology to exon 6 of HPS-1 itself. In the pseudogene, this exon is surrounded by portions of both its normal flanking introns. These data provide the first characterization of an HPS-1 pseudogene, called HPS1-psi1. During amplification of exon 6 of the HPS-1 gDNA for mutation identification, the pseudogene might also be amplified, leading to a false positive for mutation. In addition, amplification of specific parts of the HPS-1 cDNA (e.g., exons 2-5) for mutation detection might lead to false positives for mutations, if the cDNA is contaminated with gDNA. This calls for caution when employing these screening approaches.

Albinism, Oculocutaneous↗
PubMed2002

Effect of pirfenidone on the pulmonary fibrosis of Hermansky-Pudlak syndrome.

Hermansky-Pudlak syndrome (HPS) consists of oculocutaneous albinism, a platelet storage pool deficiency and, in patients with HPS1 gene mutations, a progressive, fatal pulmonary fibrosis. We investigated the safety and efficacy of an antifibrotic agent, pirfenidone (800 mg, t.i.d.), in treating 21 adult Puerto Rican HPS patients, including 20 homozygous for the same HPS1 mutation. Patients were examined every 4 months for up to 44 months in a randomized, placebo-controlled trial, with rate of change in pulmonary function values as outcome parameters. Using the complete data set of 130 patient admissions, a repeated measures model showed that 11 pirfenidone-treated patients lost FVC at a rate 5% of predicted ( approximately 400 mL) per year slower than 10 placebo-treated patients (p=0.001). A random coefficients model showed no significant difference. However, using data restricted to patients with an initial FVC >50% of predicted, both models showed the pirfenidone group losing FVC (p<0.022), FEV(1) (p<0.0007), TLC (p<0.001), and DL(CO) (p<0.122) at a rate approximately 8%/year slower than the placebo group. Clinical and laboratory side effects were similar in the two groups. Pirfenidone appears to slow the progression of pulmonary fibrosis in HPS patients who have significant residual lung function.

Adult↗
PubMed2002

Hermansky-Pudlak syndrome: vesicle formation from yeast to man.

The disorders known as Hermansky-Pudlak syndrome (HPS) are a group of genetic diseases resulting from abnormal formation of intracellular vesicles. In HPS, dysfunction of melanosomes results in oculocutaneous albinism, and absence of platelet dense bodies causes a bleeding diathesis. In addition, some HPS patients suffer granulomatous colitis or fatal pulmonary fibrosis, perhaps due to mistrafficking of a subset of lysosomes. The impaired function of specific organelles indicates that the causative genes encode proteins operative in the formation of certain vesicles. Four such genes, HPS1, ADTB3A, HPS3, and HPS4, are associated with the four known subtypes of HPS, i.e. HPS-1, HPS-2, HPS-3, and HPS-4. ADTB3A codes for the beta 3 A subunit of adaptor complex-3, known to assist in vesicle formation from the trans-Golgi network or late endosome. However, the functions of the HPS1, HPS3, and HPS4 gene products remain unknown. These three genes arose with the evolution of mammals and have no homologs in yeast, reflecting their specialized function. In contrast, all four known HPS-causing genes have homologs in mice, a species with 14 different models of HPS, i.e. hypopigmentation and a platelet storage pool deficiency. Pursuit of the mechanism of mammalian vesicle formation and trafficking, impaired in HPS, relies upon investigation of these mouse models as well as studies of protein complexes involved in yeast vacuole formation.

Animals↗
PubMed2000

Hermansky-Pudlak syndrome and related disorders of organelle formation.

Hermansky-Pudlak syndrome (HPS) consists of a group of genetically heterogeneous disorders which share the clinical findings of oculocutaneous albinism, a platelet storage pool deficiency, and some degree of ceroid lipofuscinosis. Related diseases share some of these findings and may exhibit other symptoms and signs but the underlying defect in the entire group of disorders involves defective intracellular vesicle formation, transport or fusion. Two HPS-causing genes, HPS1 and ADTB3A, have been isolated but the function of only the latter has been determined. ADTB3A codes for the beta 3A subunit of adaptor complex-3, responsible for vesicle formation from the trans-Golgi network (TGN). The many HPS patients who do not have HPS1 or ADTB3A mutations have their disease because of mutations in other genes. Candidates for these HPS-causing genes include those responsible for mouse models of HPS or for the 'granule' group of eye color genes in Drosophila. Each gene responsible for a subset of HPS or a related disorder codes for a protein which almost certainly plays a pivotal role in vesicular trafficking, inextricably linking clinical and cell biological interests in this group of diseases.

Animals↗
PubMed1996

A fusion pore phenotype in mast cells of the ruby-eye mouse.

Using patch-clamp capacitance and amperometric techniques, we have identified an exocytotic phenotype that affects the function of the fusion pore, the molecular structure that connects the lumen of a secretory vesicle with the extracellular environment during exocytosis. Direct observation of individual exocytotic events in mast cells from the ruby-eye mouse (ru/ru) showed a 3-fold increase in the fraction and duration of transient fusion events with respect to wild-type mice. The fraction of the total fusion events that were transient increased from 0.22 +/- 0.02 (wild type) to 0.65 +/- 0.02 (ru/ru), and the average duration of these events increased from 418 +/- 32 ms (wild type) to 1207 +/- 89 ms (ru/ru). We also show that this phenotype can reduce and delay an evoked secretory response by causing the fusion of vesicles that have been previously emptied by repeated cycles of transient fusion. The exocytotic phenotype that we describe here may be a cause of diseases like platelet storage pool deficiency and prolonged bleeding times for which the ruby-eye mouse serves as an animal model. Furthermore, the identification of the gene causing the fusion pore phenotype reported here will illuminate the molecular mechanisms regulating exocytotic fusion.

Animals↗
PubMed1987

Chediak-Higashi syndrome.

The use of cytochemical, electron microscopic, immunofluorescent, and tissue culture techniques has led to important advances in our understanding of the mechanisms underlying the pathogenesis of the Chediak-Higashi syndrome (CHS). This rare and fatal autosomal recessive disorder is clinically characterized by partial albinism, frequent pyogenic infections, and an accelerated lymphohistiocytic phase. The pathological hallmark of CHS is the presence in all white blood cells of massive lysosomal inclusions, which are formed through a combined process of fusion, cytoplasmic injury, and phagocytosis. The abnormal inclusions exhibit both azurophilic and specific granular markers, and are probably responsible for most of the impaired leukocyte and other cell functions in CHS patients. In addition, a selective profound natural killer (NK) cell function and platelet storage pool deficiencies have been described in these patients. Impaired microtubule assembly and functions, mediated by abnormal intracellular cyclic nucleotide levels, which could be corrected by treatment with ascorbic acid, were suggested to be the pathophysiological basis for CHS abnormalities. However, some recent studies have questioned this cytoskeletal model, which is suggested to be rather a secondary manifestation of CHS.

Antineoplastic Agents↗
PubMed1990

Albinism and Hermansky-Pudlak syndrome in Puerto Rico.

Five types of oculocutaneous albinism and two types of ocular albinism were found among 349 Puerto Rican albinos. The most prevalent type of albinism was the Hermansky-Pudlak syndrome (HPS). HPS was observed in five of every six albinos in Puerto Rico. The prevalence of HPS was highest in the northwestern quarter of the island, affecting approximately one in 1,800 persons, and approximately one in 22 are carriers of the gene. HPS is an autosomal recessively inherited triad of a tyrosinase-positive type of albinism, a hemorrhagic diathesis due to storage pool deficient platelets and accumulation of ceroid in tissues. The pigmentary phenotype of HPS albinos resembled that of any other type of oculocutaneous or ocular albinism. The most reliable method of diagnosing HPS is by a deficiency of platelet dense bodies observed by electron microscopy. The accumulation of ceroid in the tissues is associated with fibrotic restrictive lung disease and granulomatous enteropathic disease. The enteropathic disorder resembles Crohn's disease and with few exceptions, had its onset after 13 years of age. The major causes of death were fibrotic restrictive pulmonary disease, hemorrhagic episodes and sequelae of granulomatous enteropathic disease. Menometrorrhagia was common in women with HPS. No immune deficiency was found in HPS patients. The majority of patients with HPS had visual acuities of 20/200 or worse and consequently were legally blind. Albinos of all types, including HPS, lacked binocular vision due to nearly complete crossing of the optic tracts.

Albinism, Ocular↗