HPS4 Research Articles

Clinical, Molecular, and Cellular Features of Non-Puerto Rican Hermansky–Pudlak Syndrome Patients of Hispanic Descent

Hermansky-Pudlak syndrome is an autosomal recessive condition characterized by a bleeding diathesis and hypopigmentation of the skin, hair and eyes. Some HPS patients develop other complications such as granulomatous colitis and/or a fatal pulmonary fibrosis. Eight genes have been associated with the condition, resulting in subtypes HPS-1 through HPS-8. The HPS gene products are involved in the biogenesis of specialized lysosome-related organelles such as melanosomes, platelet delta granules and others. HPS1 and HPS4 form a stable complex named BLOC-3, and patients with BLOC-3 or AP-3 deficiency develop pulmonary fibrosis. Therefore, it is important to subtype each HPS patient. HPS type 1 (HPS-1) occurs frequently on the island Puerto Rico due to a founder mutation. Here, we describe seven mutations, six of which are previously unreported, in the HPS1, HPS4 and HPS5 genes among patients of Mexican, Uruguayan, Honduran, Cuban, Venezuelan and Salvadoran ancestries. Our findings demonstrate that the diagnosis of HPS should be considered in Hispanic patients with oculocutaneous albinism and bleeding symptoms. Moreover, such patients should not be assumed to have the HPS-1 subtype typical of northwest Puerto Rican patients. We recommend molecular HPS subtyping in such cases, since it may have significant implications for prognosis and intervention.

Patients with Hermansky-Pudlak Syndrome Show Various Phenotypes Caused by Novel Mutations,

Abstract 3286▪▪This icon denotes a clinically relevant abstract Background:Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive disorder causing oculocutaneous albinism, bleeding disorder and ceroid lipofuscinosis. Platelets from HPS patients are characterized by impaired secretion of dense (δ)-bodies (CD63). Neutropenia and susceptibility to recurrent infections were exclusively observed in HPS2 patients so far. There are eight known human HPS genes (HPS1-HPS8), each leading to a particular clinical HPS subtype (HPS1-HPS8). Patients/Results:The patients show a typical HPS phenotype concerning oculocutaneous albinism and bleeding symptoms. In vivo-, in vitro bleeding time and platelet aggregometry analyses revealed impaired platelet function. We identified HPS3 in two Turkish brothers and HPS2 in a girl from the United Emirates. Both brothers with HPS3 demonstrated absence of platelet δ-granule secretion measured by flow cytometry analysis. A novel 1 bp-deletion in the HPS3 gene was identified in both brothers. In addition, one brother with HPS3 demonstrated psychomotoric retardation. MRI scan revealed cranial gliosis. Interestingly, array-CGH analysis revealed a 0.7 Mb deletion on chromosome 17 which had not been identified in the other brother and which seems to have caused the cranial gliosis.The girl with HPS2 suffered from life-threatening bleeding after tonsillectomy leading to severe asphyxia, resuscitation and finally, to mental retardation. Flow cytometry analysis demonstrated impaired platelet δ-granule secretion with a typical pattern for HPS2. CD63 expression was already increased on resting platelets, but there was only little increase after thrombin stimulation. Interestingly, only a NK-CD107 partial degranulation defect was diagnosed. So far, clinical symptoms of immunodeficiency are not obvious. Molecular genetic analyses revealed a novel 2 bp-deletion in the last exon of HPS2 leading to a frameshift and a prolonged altered protein. The location of the deletion at the very C-terminal end may prevent a complete loss of the HPS2 protein leading to a less pronounced severity of immunodeficiency as in other HPS2 patients. Conclusion:Patients with oculocutaneous albinism should be investigated for increased clinical bleeding symptoms. In case of increased bleeding symptoms, analyses of primary hemostasis should be initiated to confirm HPS. Using flow cytometry analyses HPS2 can be distinguished from the other subtypes of HPS. Molecular genetic investigations should be performed to differentiate the various subtypes of HPS which is important for therapy and prognosis. The HPS3 patient`s mental retardation seemed to be caused by an additional deletion. The identification of the molecular genetic defect helps to understand the patients` various clinical phenotypes. Disclosures:Zieger:Novo Nordisk: Research Funding.

Novel mutations in the HPS1 gene among Puerto Rican patients

Hermansky-Pudlak syndrome (HPS) is a disorder of oculocutaneous albinism (OCA) and platelet storage pool deficiency. Eight different disease-causing genes have been identified, whose gene products are thought to be involved in the biogenesis of lysosome-related organelles. HPS type 1 (HPS-1) is the most common HPS subtype in Puerto Rico, with a frequency of 1:1800 in the northwest of the island due to a founder mutation, i.e. a 16-bp duplication in exon 15 of the HPS1 gene (c.1472_1487dup16; p.H497QfsX90). We identified three Puerto Rican HPS-1 patients who carried compound heterozygous HPS1 mutations. One patient was heterozygous for c.937G>A, causing a missense mutation (p.G313S) at the 3 splice junction of exon 10. This mutation resulted in activation of a cryptic intronic splice site causing an aberrantly spliced HPS1 mRNA that included 144-bp of intronic sequence, producing 11 novel amino acids followed by a stop codon. The other two patients were heterozygous for the previously reported c.972delC in HPS1, resulting in a frameshift and a premature stop codon (p.M325WfsX6). These findings indicate that, among Puerto Ricans, other HPS1 mutations apart from the 16-bp duplication should be considered in the analysis of this population.

A Comprehensive Analysis Reveals Mutational Spectra and Common Alleles in Chinese Patients with Oculocutaneous Albinism

Oculocutaneous albinism (OCA) is a heterogeneous recessive disorder with hypopigmentation in the skin, hair, and eyes. At least 16 genes have been identified as causative genes for human OCA. No comprehensive analysis has been conducted to study the spectral distribution of OCA in Chinese patients. We screened 127 unrelated and unselected Chinese OCA patients for mutations in the TYR, OCA2, TYRP1, SLC45A2, and HPS1 genes. We found that the spectrum of mutational genes and alleles of OCA is population specific. OCA1 is the most common (70.1% of cases) form of Chinese OCA, whereas OCA2, OCA4, and HPS1 account for 10.2%, 12.6%, and 1.6%, respectively. No apparent pathological mutation of TYRP1 has been found. Thirty-eight previously unreported mutational alleles were identified from these OCA patients and were not found in 100 nonalbinism subjects. Of the TYR mutational alleles, 81.1% were clustered on exons 1 and 2. Ten common alleles account for 74.6% of the mutational TYR alleles in Chinese OCA1 patients. The p.D160H allele accounts for 55.6% of the mutational SLC45A2 alleles in Chinese OCA4 patients. These results provide useful information for the establishment of an optimized strategy of gene diagnosis and genetic counseling of Chinese OCA patients.

Genetic determinants of hair and eye colours in the Scottish and Danish populations

BackgroundEye and hair colour is highly variable in the European population, and is largely genetically determined. Both linkage and association studies have previously been used to identify candidate genes underlying this variation. Many of the genes found were previously known as underlying mutant mouse phenotypes or human genetic disease, but others, previously unsuspected as pigmentation genes, have also been discovered.ResultsWe assayed the hair of a population of individuals of Scottish origin using tristimulus colorimetry, in order to produce a quantitative measure of hair colour. Cluster analysis of this data defined two groups, with overlapping borders, which corresponded to visually assessed dark versus red/light hair colour. The Danish population was assigned into categorical hair colour groups. Both cohorts were also assessed for eye colour. DNA from the Scottish group was genotyped at SNPs in 33 candidate genes, using 384 SNPs identified by HapMap as representatives of each gene. Associations found between SNPs and colorimetric hair data and eye colour categories were replicated in a cohort of the Danish population. The Danish population was also genotyped with SNPs in 4 previously described pigmentation genes. We found replicable associations of hair colour with the KITLG and OCA2 genes. MC1R variation correlated, as expected, with the red dimension of colorimetric hair colour in Scots. The Danish analysis excluded those with red hair, and no associations were found with MC1R in this group, emphasising that MC1R regulates the colour rather than the intensity of pigmentation. A previously unreported association with the HPS3 gene was seen in the Scottish population. However, although this replicated in the smaller cohort of the Danish population, no association was seen when the whole study population was analysed.ConclusionsWe have found novel associations with SNPs in known pigmentation genes and colorimetrically assessed hair colour in a Scottish and a Danish population.

The first case report of a Chinese Hermansky–Pudlak syndrome patient with a novel mutation on HPS1 gene

Hermansky–Pudlak syndrome (HPS; OMIM 203300) is an autosomal recessive and a genetically heterogeneous disorder characterized by oculocutaneous albinism (OCA), bleeding tendency, and ceroid deposition which may cause lung fibrosis, colitis, and cardiomyopathy. Patients with HPS often die in their middle ages [1]. The hallmark of pathological features of HPS is the disrupted biogenesis of lysosome-related organelles (LROs), such as melanosomes and platelet dense granules [2]. The identification of the first HPS gene, HPS1, in 1996 [3] prompts the identification of seven other HPS genes (HPS2–HPS8) during the past decade [2].

A large analphoid invdup(3)(q22.3qter) marker chromosome characterized by array-CGH in a child with malformations, mental retardation, ambiguous genitalia and Blaschko's lines

We report a new case of mosaic chromosome 3-derived marker chromosome, present in fibroblasts but not in lymphocytes, found in a child with malformations, mental retardation and ambiguous genitalia. Cytogenetic and molecular analysis showed that the supernumerary invdup(3)(q22.3qter) chromosome was negative at FISH with alpha satellite probe. The presence of a functional neocentromere was confirmed by immunofluorescence with antibodies to centromere proteins (CENPs). Definition of the marker breakpoints has been done through array-CGH. The skin of the patient presented dyschromic areas ordered along Blaschko's lines. The invdup(3q) marker chromosome was present only in fibroblasts from the dark skin biopsy, while lymphocytes and fibroblasts from the normal skin showed a normal male karyotype. Expression of the HPS3 gene (MIM: 606118) was more than two times higher in dark skin fibroblasts. Neocentromeres are most often observed on chromosomal arm fragments that have separated from an endogenous centromere, and therefore actually confer mitotic stability to what would have been acentric fragments. To our knowledge, this invdup(3q) analphoid marker is the largest among the several reported so far. Parental origin and possible mode of formation have been defined by DNA polymorphisms studies. The size of the duplicated marker chromosome and its frequency and tissue distribution may be relevant to the severity of the propositus’ phenotype.

Genetic Testing for Oculocutaneous Albinism Type 1 and 2 and Hermansky–Pudlak Syndrome Type 1 and 3 Mutations in Puerto Rico

Hermansky-Pudlak syndrome (HPS) (MIM #203300) is a heterogeneous group of autosomal recessive disorders characterized by oculocutaneous albinism (OCA), bleeding tendency, and lysosomal dysfunction. HPS is very common in Puerto Rico (PR), particularly in the northwest part of the island, with a frequency of approximately 1:1,800. Two HPS genes and mutations have been identified in PR, a 16-base pair (bp) duplication in HPS1 and a 3,904-bp deletion in HPS3. In Puerto Ricans with more typical OCA, the most common mutation of the tyrosinase (TYR) (human tyrosinase (OCA1) gene) gene was G47D. We describe screening 229 Puerto Rican OCA patients for these mutations, and for mutations in the OCA2 gene. We found the HPS1 mutation in 42.8% of cases, the HPS3 deletion in 17%, the TYR G47D mutation in 3.0%, and a 2.4-kb deletion of the OCA2 gene in 1.3%. Among Puerto Rican newborns, the frequency of the HPS1 mutation is highest in northwest PR (1:21; 4.8%) and lower in central PR (1:64; 1.6%). The HPS3 gene deletion is most frequent in central PR (1:32; 3.1%). Our findings provide insights into the genetics of albinism and HPS in PR, and provide the basis for genetic screening for these disorders in this minority population.

Transcriptome Differences Between the Frontal Cortex and Hippocampus of Wild-Type and Humanized Presenilin-1 Transgenic Mice

Objective The authors investigated the differences between the frontal cortical (Fc) and hippocampal (Hc) transcriptomes of wild type (wt mPS1), humanized presenilin-1 (PS1 [wt hPS1]) and Alzheimer-disease (AD)–linked ΔE9 hPS1 mutant mice. Methods Using high-density oligonucleotide arrays, they recently performed transcriptome profiling of wt mPS1, wt hPS1, and ΔE9 hPS1 mutant mice. Whereas these studies analyzed the commonalities of gene expression patterns and commonly-regulated genes across the two brain areas and across the animal models, the current study focused on the gene-expression differences across Fc and Hc, two critical AD-affected brain regions. Results The data revealed that in the wild-type mice, there are significant transcriptome differences between the Fc and the Hc tissue, and these expression differences are maintained in humanized transgenic mice carrying the wt hPS1 gene or ΔE9 hPS1 mutation. Also, they provide evidence that a subset of genes show disturbed regional Fc–Hc gene-expression ratios in the transgenic mice carrying the ΔE9 hPS1 mutation. Some of these genes, including stearoyl-Coenzyme A desaturase-2 (Scd2) and Prostaglandin D2 synthase (Ptgds), have been previously implicated in the pathology of AD. Conclusions Data suggest that disturbed gene-expression ratios between cortical regions may be an important event in altered brain physiology. The authors investigated the differences between the frontal cortical (Fc) and hippocampal (Hc) transcriptomes of wild type (wt mPS1), humanized presenilin-1 (PS1 [wt hPS1]) and Alzheimer-disease (AD)–linked ΔE9 hPS1 mutant mice. Using high-density oligonucleotide arrays, they recently performed transcriptome profiling of wt mPS1, wt hPS1, and ΔE9 hPS1 mutant mice. Whereas these studies analyzed the commonalities of gene expression patterns and commonly-regulated genes across the two brain areas and across the animal models, the current study focused on the gene-expression differences across Fc and Hc, two critical AD-affected brain regions. The data revealed that in the wild-type mice, there are significant transcriptome differences between the Fc and the Hc tissue, and these expression differences are maintained in humanized transgenic mice carrying the wt hPS1 gene or ΔE9 hPS1 mutation. Also, they provide evidence that a subset of genes show disturbed regional Fc–Hc gene-expression ratios in the transgenic mice carrying the ΔE9 hPS1 mutation. Some of these genes, including stearoyl-Coenzyme A desaturase-2 (Scd2) and Prostaglandin D2 synthase (Ptgds), have been previously implicated in the pathology of AD. Data suggest that disturbed gene-expression ratios between cortical regions may be an important event in altered brain physiology.

High Frequency of Hermansky–Pudlak Syndrome Type 1 (HPS1) Among Japanese Albinism Patients and Functional Analysis of HPS1 Mutant Protein

Hermansky-Pudlak syndrome (HPS) is an autosomal recessive disorder characterized by oculocutaneous albinism (OCA), bleeding tendency, and lysosomal accumulation of ceroid-like material. Seven genetically distinct subtypes of HPS are known in humans; most are rare outside of Puerto Rico. Here, we describe the analysis of the HPS1 gene in 24 Japanese OCA patients who lacked mutations in the four genes known to cause OCA (TYR/OCA1, P/OCA2, TYRP1/OCA3, and MATP/OCA4), and the identification of eight different HPS1 mutations in ten of these patients, four of which were novel (W583X, L668P, 532insC, 1691delA). An IVS5+5G --> A splice consensus mutation was particularly frequent, the result of a founder effect for this allele in Japanese patients. Functional analysis by transfection of the L668P variant into Hps1-mutant melan-ep mouse melanocytes showed that this missense substitution is pathologic, resulting in an Hps-1 protein that is unable to assemble into the biogenesis of lysosome-related organelles complex-3.

Association of the Hermansky-Pudlak syndrome type-3 protein with clathrin

BackgroundHermansky-Pudlak syndrome (HPS) is a disorder of lysosome-related organelle biogenesis characterized by oculocutaneous albinism and prolonged bleeding. These clinical findings reflect defects in the formation of melanosomes in melanocytes and dense bodies in platelets. HPS type-3 (HPS-3) results from mutations in the HPS3 gene, which encodes a 1004 amino acid protein of unknown function that contains a predicted clathrin-binding motif (LLDFE) at residues 172–176.ResultsClathrin was co-immunoprecipitated by HPS3 antibodies from normal but not HPS3 null melanocytes. Normal melanocytes expressing a GFP-HPS3 fusion protein demonstrated partial co-localization of GFP-HPS3 with clathrin following a 20°C temperature block. GFP-HPS3 in which the predicted clathrin-binding domain of HPS3 was mutated (GFP-HPS3-delCBD) did not co-localize with clathrin under the same conditions. Immunoelectron microscopy of normal melanocytes expressing GFP-HPS3 showed co-localization of GFP-HPS3 with clathrin, predominantly on small vesicles in the perinuclear region. In contrast, GFP-HPS3-delCBD did not co-localize with clathrin and exhibited a largely cytoplasmic distribution.ConclusionHPS3 associates with clathrin, predominantly on small clathrin-containing vesicles in the perinuclear region. This association most likely occurs directly via a functional clathrin-binding domain in HPS3. These results suggest a role for HPS3 and its protein complex, BLOC-2, in vesicle formation and trafficking.

Ultrastructural Features of Trafficking Defects Are Pronounced in Melanocytic Nevus in Hermansky–Pudlak Syndrome Type 1

Hermansky-Pudlak syndrome (HPS) is an autosomal recessive disorder characterized by oculocutaneous albinism, a bleeding disorder, and ceroid lipofuscinosis in the lungs and gut. HPS is genetically heterogeneous and the most common variant, HPS type 1, is caused by mutations in HPS1 gene. The protein encoded by HPS1 is considered to facilitate the trafficking of melanocyte-specific gene products into the premelanosome. We report the ultrastructural findings in a melanocytic nevus seen in a 17-y-old Japanese female patient with HPS1 who is a compound heterozygote of HPS1 mutations, including a novel mutation. Electron microscopy of a pinkish papule corresponding to the melanocytic nevus revealed markedly aberrant, immature melanosomes, large membranous structures, and giant melanosomes in the vicinity of trans-Golgi network, the characteristic abnormalities because of protein trafficking defects in HPS1. These ultrastructural features were far more clearly demonstrated in the nevus cells than in the epidermal melanocytes. Thus, ultrastructural analysis of nevus cells may be an additional diagnostic tool for HPS1 and could give us important clues to further understanding of the pathomechanisms of HPS.

Detection of hemizygosity in Hermansky - Pudlak syndrome by quantitative real-time PCR

Hermansky-Pudlak syndrome (HPS) is an autosomal recessive disorder characterized by oculocutaneous albinism, a bleeding diathesis and, in some patients, pulmonary fibrosis or granulomatous colitis. HPS is associated with biosynthesis defects of melanosomes, platelet-dense bodies, and lysosomes. There are seven genetic HPS subtypes; HPS-1 is the most common. We used a real-time quantitative PCR (qPCR) approach to investigate six HPS-1 patients, previously assigned as having homozygous mutations in the HPS1 gene. HPS1 gene copy numbers, calculated by use of a comparative Ct method, revealed that one patient was in fact hemizygous for her c.1189delC (S396delC) HPS1 mutation. The causative deletion/insertion was 13,966 bp in size, with defined breakpoints, and involved an adjacent gene (C10orf33). A mechanism of formation is proposed for the deletion/insertion, and both multiplex and qPCR indicated that the deletion/insertion was present in the patient, her brother, and her father. qPCR amplification is valuable for detecting deletions too small to be identified by fluorescence in situ hybridization. This demonstration of hemizygosity, performed using genomic DNA, can eliminate concerns about non-paternity and can verify the diagnosis of an autosomal recessive disorder when a DNA alteration appears to be homozygous by standard PCR and sequencing methods, and its pathogenicity is in doubt.

Melanocytes Derived from Patients with Hermansky–Pudlak Syndrome Types 1, 2, and 3 Have Distinct Defects in Cargo Trafficking

Hermansky-Pudlak Syndrome (HPS) is a genetically heterogeneous disorder in which mutations in one of several genes interrupts biogenesis of melanosomes, platelet dense bodies, and lysosomes. Affected patients have oculocutaneous albinism, a bleeding diathesis, and sometimes develop granulomatous colitis or pulmonary fibrosis. In order to assess the role of HPS genes in melanosome biogenesis, melanocytes cultured from patients with HPS subtypes 1, 2, or 3 were assessed for the localization of various melanocyte proteins. Tyrosinase, Tyrp1, and Dct/Tyrp2 were atypically and distinctly expressed in HPS-1 and HPS-3 melanocytes, whereas only tyrosinase showed an atypical distribution in HPS-2 melanocytes. The HPS1 and AP3B1 (i.e., HPS-2) gene products showed no expression in HPS-1 and HPS-2 melanocytes, respectively, whereas HPS-3 melanocytes exhibited normal expression for both proteins. In normal human melanocytes, the HPS1 protein was expressed as an approximately 80 kDa molecule with both granular and reticular intracellular profiles. In HPS-1, lysosome associated membrane protein 1 (LAMP1), and LAMP3 were localized to abnormal large granules; in HPS-2, all LAMPs exhibited a normal granular expression; and in HPS-3, LAMP1, and LAMP3 exhibited a distinct less granular and more floccular pattern. In contrast, the expressions of Rab 27, transferrin, and cKit were unaffected in all three HPS genotypes. These data demonstrate that the three initially identified subtypes of human HPS exhibit distinct defects in the trafficking of various melanocyte-specific proteins.

Hermansky-Pudlak Syndrome with a Novel Mutation

We report a case of Hermansky-Pudlak syndrome (HPS) with a novel mutation in the HPS1 gene. This case showed oculocutaneous albinism and lysosomal ceroid accumulation, however platelet dysfunction was not observed. Histopathological findings of the biopsied lung tissue were compatible with HPS. Sequencing analysis showed the insertion of C in the codon 178 (739 bp) of the HPS1 gene forming a stop codon at codon 181. To the best of our knowledge, this is a novel HPS1 gene mutation.

Hermansky-Pudlak Syndrome with Interstitial Pneumonia without Mutation of HSP1 Gene

A 57-year-old man with occulocutaneous albinism was admitted to our hospital because of exertional dyspnea and an abnormal shadow on chest roentgenogram. Chest CT revealed diffuse interstitial shadows with reticulonodular opacities in the bilateral whole lung fields and his pulmonary function test was consistent with a restrictive finding. Histologically, intraluminal diffuse fibrosis and interstitial fibrosis existed and ceroid-like materials within alveolar macrophages were demonstrated in a transbronchial lung biopsy specimen. In addition, because platelet dysfunction and ceroid-like materials within the reticuloendothelial cells of urine and bone marrow aspiration were recognized, we made a diagnosis of Hermansky-Pudlak syndrome (HPS). Gene analysis of the patient's peripheral blood cells did not reveal that he was a compound homogeneity for HPS1 gene mutations. Concerning treatment, although corticosteroid therapy was administered, his clinical symptoms and abnormal chest shadow have not changed.

Inflammatory response and cathepsins in silica-exposed Hermansky-Pudlak syndrome model pale ear mice.

Hermansky-Pudlak syndrome (HPS) is a hereditary disorder involving the sorting processes of intracellular organelles such as lysosomes of reticuloendothelial cells. Pale ear (ep) mouse is known to have the HPS1 gene mutation, which is seen in patients with HPS and pulmonary fibrosis. As pulmonary fibrosis is not spontaneously observed in ep mice, we hypothesized that external stimuli are necessary for the genetic predisposition of its development. We used silica as the external stimulus to induce the alveolar macrophage-mediated inflammatory response and evaluated the pathological changes of the lung and biochemical analysis of collagenolytic lysosomal enzymes cathepsins L and B in ep mice. Treatment with silica induced the following: persistent accumulation of activated macrophages; delayed clearance of silica from alveolar spaces; and increased collagen fibers in alveolar tissues, which were shown with trichrome staining in ep mice. The comparison of bronchoalveolar lavage cells between the naïve ep and control mice revealed: decreased enzymatic activities but increased antigenic levels of cathepsins L and B, resulting in significantly lower ratios of activity to antigen; increased ceroid deposits and cathepsin L antigens in lysosomes; and no abnormal forms of cathepsins were detected. After silica instillation, activities of cathepsin L in the ep mice increased but ratios of activity to antigen were still significantly low. These phenomena induced by silica suggest that external stimuli bring forth fibrogenesis in the animal models or humans that have HPS1 gene mutation.

Aberrant lung structure, composition, and function in a murine model of Hermansky-Pudlak syndrome.

Hermansky-Pudlak syndrome (HPS) is a genetically heterogeneous inherited disease causing hypopigmentation and prolonged bleeding times. An additional serious clinical problem of HPS is the development of lung pathology, which may lead to severe lung disease and premature death. No cure for the disease exists, and previously, no animal model for the HPS lung abnormalities has been reported. A mouse model of HPS, which is homozygously recessive for both the Hps1 (pale ear) and Hps2 (pearl) genes, exhibits striking abnormalities of lung type II cells. Type II cells and lamellar bodies of this mutant are greatly enlarged, and the lamellar bodies are engorged with surfactant. Mutant lungs accumulate excessive autofluorescent pigment. The air spaces of mutant lungs contain age-related elevations of inflammatory cells and foamy macrophages. In vivo measurement of lung hysteresivity demonstrated aberrant lung function in mutant mice. All these features are similar to the lung pathology described in HPS patients. Morphometry of mutant lungs indicates a significant emphysema. These mutant mice provide a model to further investigate the lung pathology and therapy of HPS. We hypothesize that abnormal type II cell lamellar body structure/function may predict future lung pathology in HPS.

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.

Hermansky-Pudlak syndrome type 1: gene organization, novel mutations, and clinical-molecular review of non-Puerto Rican cases

Hermansky-Pudlak syndrome (HPS) is an autosomal recessive disorder causing oculocutaneous albinism and a platelet storage pool deficiency, reflecting defective biosynthesis and/or processing of melanosomes and platelet dense bodies. Four human genes (HPS1, ADTB3A, HPS3, HPS4) are associated with four subtypes of HPS. The most common is HPS-1. A 16-bp duplication in exon 15 of the HPS1 gene causes HPS-1 in 450 northwest Puerto Rican patients; 13 other HPS1 mutations have been reported in non-Puerto Rican patients. We screened 26 HPS patients, who lacked a molecular diagnosis, for HPS1 defects and identified six patients with six different HPS1 mutations. Four novel mutations were discovered, including the first HPS1 missense mutation, 922T>C, in exon 8. This mutation, along with 624delG in exon 6, preserve RNA transcription, while 561delC in exon 5 and [1581delA;1594C>A] in exon 14 produce no RNA on northern blot. One of six adult patients developed pulmonary fibrosis, and two patients ages 16 and 17 have granulomatous colitis. These complications are common among Puerto Rican HPS-1 patients but have not appeared in HPS-2 or HPS-3 patients. The diagnosis of HPS-1, available only on molecular grounds, has important prognostic and treatment implications.