Clinical, molecular, and cellular features of non-Puerto Rican Hermansky-Pudlak syndrome patients of Hispanic descent

Differential expression and alternative splicing analyses of multiple tissues reveal albinism-associated genes in the Wels catfish (Silurus glanis)

Albinism is a widespread departure from a typical body colouration due to altered melanin production. The Wels catfish (Silurus glanis) is among the largest freshwater fish species in the world, and albino individuals occur both in the wild and in aquaculture. Here, we performed transcriptome-wide analysis of albino and normally pigmented S. glanis using four tissues (skin, dorsal fin, whole eye and liver) to identify genes associated with albinism by exploring patterns of differential expression (DE) and differential alternative splicing (DAS). Multi-tissue analyses revealed a large number of genes in skin (n = 1355) and fin (n = 614) tissue associated with the albino phenotype in S. glanis, while the number of DE genes in eye and liver tissues was lower (n = 188, n = 189, respectively). Several DE genes across multiple tissues were detected as the most promising candidates (e.g., hsp4, hsp90b1, raph1, uqcrfs1, adcy-family and wnt-family) potentially causally linked to the albino phenotype in Wels catfish. Moreover, our findings supported earlier observations of physiological differences between albino and normally pigmented individuals, particularly in energy metabolism and immune response. In contrast, there were only a few pigmentation-related genes observed among DAS genes (4 in skin, 2 in fin), the overlap between DAS and DE genes was low (n = 25) and did not include known pigmentation-related genes. This suggests that DAS and DE in Wels catfish are, to a large extent, independent processes, and the observed alternative splicing cases are probably not causally linked with albinism in S. glanis. This work provides the first transcriptome-wide multi-tissue insights into the albinism of Wels catfish and serves as a valuable resource for further understanding the genetic mechanisms of pigmentation in fish.

Hermansky-Pudlak Syndrome and Lung Disease: Pathogenesis and Therapeutics

Hermansky-Pudlak Syndrome (HPS) is a rare, genetic, multisystem disorder characterized by oculocutaneous albinism (OCA), bleeding diathesis, immunodeficiency, granulomatous colitis, and pulmonary fibrosis. HPS pulmonary fibrosis (HPS-PF) occurs in 100% of patients with subtype HPS-1 and has a similar presentation to idiopathic pulmonary fibrosis. Upon onset, individuals with HPS-PF have approximately 3 years before experiencing signs of respiratory failure and eventual death. This review aims to summarize current research on HPS along with its associated pulmonary fibrosis and its implications for the development of novel treatments. We will discuss the genetic basis of the disease, its epidemiology, and current therapeutic and clinical management strategies. We continue to review the cellular processes leading to the development of HPS-PF in alveolar epithelial cells, lymphocytes, mast cells, and fibrocytes, along with the molecular mechanisms that contribute to its pathogenesis and may be targeted in the treatment of HPS-PF. Finally, we will discuss emerging new cellular and molecular approaches for studying HPS, including lentiviral-mediated gene transfer, induced pluripotent stem cells (iPSCs), organoid and 3D-modelling, and CRISPR/Cas9-based gene editing approaches.

Hermansky-Pudlak syndrome pulmonary fibrosis: a rare inherited interstitial lung disease

Pulmonary fibrosis is a progressive interstitial lung disease of unknown aetiology with a poor prognosis. Studying genetic diseases associated with pulmonary fibrosis provides insights into the pathogenesis of the disease. Hermansky-Pudlak syndrome (HPS), a rare autosomal recessive disorder characterised by abnormal biogenesis of lysosome-related organelles, manifests with oculocutaneous albinism and excessive bleeding of variable severity. Pulmonary fibrosis is highly prevalent in three out of 10 genetic types of HPS (HPS-1, HPS-2 and HPS-4). Thus, genotyping of individuals with HPS is clinically relevant. HPS-1 tends to affect Puerto Rican individuals due to a genetic founder effect. HPS pulmonary fibrosis shares some clinical features with idiopathic pulmonary fibrosis (IPF), including dyspnoea, cough, restrictive lung physiology and computed tomography (CT) findings of fibrosis. In contrast to IPF, HPS pulmonary fibrosis generally affects children (HPS-2) or middle-aged adults (HPS-1 or HPS-4) and may be associated with ground-glass opacification in CT scans. Histopathology of HPS pulmonary fibrosis, and not IPF, shows vacuolated hyperplastic type II cells with enlarged lamellar bodies and alveolar macrophages with lipofuscin-like deposits. Antifibrotic drugs approved as treatment for IPF are not approved for HPS pulmonary fibrosis. However, lung transplantation has been performed in patients with severe HPS pulmonary fibrosis. HPS pulmonary fibrosis serves as a model for studying fibrotic lung disease and fibrosis in general.

Periodic albinism of a widely used albino mutant of Xenopus laevis caused by deletion of two exons in the Hermansky-Pudlak syndrome type 4 gene

The periodic albino mutant of Xenopus laevis is a recessive mutant, in which reduced amounts of melanin appear in the retinal pigment epithelium (RPE) and in melanophores at the late embryonic stage, after which both RPE and melanophores gradually depigment. Three types of pigment cells (melanophores, iridophores and xanthophores) have been reported to be affected in this albino. However, the causative gene of the periodic albinism remains unknown. Hermansky–Pudlak syndrome (HPS) is an autosomal recessive disorder that affects humans and mice, which is caused by defective biogenesis of lysosome‐related organelles (LROs). Two subgenomes (L and S) are present in the allotetraploid frog X. laevis. Comparison of genes between the chromosomes 1L and 1S revealed that the HPS type 4 (hps4) gene was present only in chromosome 1L. In the albino mutant, a 1.9 kb genomic deletion in the hps4.L gene including exons 7 and 8 caused a premature stop codon to create a truncated Hps4 protein. Injection of wild‐type hps4.L mRNA into mutant embryos rescued the albino phenotype. These findings indicate that hps4 is a causative gene for the periodic albinism in X. laevis. The phenotype of this mutant should be reassessed from the perspective of LRO biogenesis.

Very Early Onset Inflammatory Bowel Disease: A Clinical Approach With a Focus on the Role of Genetics and Underlying Immune Deficiencies

Very early onset inflammatory bowel disease (VEO-IBD) is defined as IBD presenting before 6 years of age. When compared with IBD diagnosed in older children, VEO-IBD has some distinct characteristics such as a higher likelihood of an underlying monogenic etiology or primary immune deficiency. In addition, patients with VEO-IBD have a higher incidence of inflammatory bowel disease unclassified (IBD-U) as compared with older-onset IBD. In some populations, VEO-IBD represents the age group with the fastest growing incidence of IBD. There are contradicting reports on whether VEO-IBD is more resistant to conventional medical interventions. There is a strong need for ongoing research in the field of VEO-IBD to provide optimized management of these complex patients. Here, we provide an approach to diagnosis and management of patients with VEO-IBD. These recommendations are based on expert opinion from members of the VEO-IBD Consortium (www.VEOIBD.org). We highlight the importance of monogenic etiologies, underlying immune deficiencies, and provide a comprehensive description of monogenic etiologies identified to date that are responsible for VEO-IBD.

Hermansky-Pudlak syndrome: Mutation update

Hermansky-Pudlak syndrome (HPS) is a group of 10 autosomal recessive multisystem disorders, each defined by the deficiency of a specific gene. HPS-associated genes encode components of four ubiquitously expressed protein complexes: Adaptor protein-3 (AP-3) and biogenesis of lysosome-related organelles complex-1 (BLOC-1) through -3. All individuals with HPS exhibit albinism and a bleeding diathesis; additional features occur depending on the defective protein complex. Pulmonary fibrosis is associated with AP-3 and BLOC-3 deficiency, immunodeficiency with AP-3 defects, and gastrointestinal symptoms are more prevalent and severe in BLOC-3 deficiency. Therefore, identification of the HPS subtype is valuable for prognosis, clinical management, and treatment options. The prevalence of HPS is estimated at 1-9 per 1,000,000. Here we summarize 264 reported and novel variants in 10 HPS genes and estimate that ~333 Puerto Rican HPS subjects and ~385 with other ethnicities are reported to date. We provide pathogenicity predictions for missense and splice site variants and list variants with high minor allele frequencies. Current cellular and clinical aspects of HPS are also summarized. This review can serve as a manifest for molecular diagnostics and genetic counseling aspects of HPS.

New Deletions in the Hermansky-Pudlak Syndrome Type 5 Gene in a Japanese Patient

The Hermansky-Pudlak syndrome (HPS) is a rare disease characterized by oculocutaneous albinism and prolonged bleeding. HPS is caused by alterations in HPS1-10 and their related genes, comprising the biogenesis of lysosome-related organelles complex 1–3 and adapter protein 3. Here, we report a Japanese patient with HPS associated with mild hypopigmentation, nystagmus, and impaired visual acuity. Sequencing analyses of the mRNA of this patient revealed new deletions (ΔGA and ΔG) in the HPS5 gene. This was the first case of HPS5 gene deficiency in Japan, and the two above-mentioned deletions have not yet been reported among patients with HPS5.

Identification of novel variants in ten patients with Hermansky-Pudlak syndrome by high-throughput sequencing

Background: Hermansky-Pudlak syndrome (HPS) is a rare inherited platelet disorder characterized by bleeding diathesis, oculocutaneous albinism (OCA) and a myriad of often-serious clinical complications. Methods: We established the clinical and laboratory phenotype and genotype of six unrelated pedigrees comprising ten patients with clinical suspicion of HPS; including platelet aggregation, flow cytometry, platelet dense granule content, electron microscopy and high-throughput sequencing (HTS). Results: The clinical presentation showed significant heterogeneity and no clear phenotype-genotype correlations. HTS revealed two known and three novel disease-causing variants. The Spanish patients carried a homozygous p.Pro685Leufs17* deletion (n = 2) in HPS4, or the novel p.Arg822* homozygous variant (n = 1) in HPS3. In the case of two Turkish sisters, a novel missense homozygous HPS4 variant (p.Leu91Pro) was found. In two Portuguese families, genetic studies confirmed a previously reported nonsense variant (p.Gln103*) in DTNBP1 in three patients and a novel duplication (p.Leu22Argfs*33) in HPS6 in two unrelated patients. Conclusions: Our findings expand the mutational spectrum of HPS, which may help in investigating phenotype-genotype relationships and assist genetic counselling for affected individuals. This approach is a proof of principle that HTS can be considered and used in the first-line diagnosis of patients with biological and clinical manifestations suggestive of HPS. Key messages We established the relationships between the clinical and laboratory phenotype and genotype of six unrelated pedigrees comprising ten patients with clinical suspicion of HPS. Molecular analysis is useful in confirming the diagnosis and may offer some prognostic information that will aid in optimizing monitoring and surveillance for early detection of end-organ damage. This approach is a proof of principle that HTS can be considered and used in the first-line diagnosis of patients with biological and clinical manifestations suggestive of HPS.

Hermansky-Pudlak syndrome type 2 manifests with fibrosing lung disease early in childhood

Background

Hermansky-Pudlak syndrome (HPS), a hereditary multisystem disorder with oculocutaneous albinism, may be caused by mutations in one of at least 10 separate genes. The HPS-2 subtype is distinguished by the presence of neutropenia and knowledge of its pulmonary phenotype in children is scarce.

Methods

Six children with genetically proven HPS-2 presented to the chILD-EU register between 2009 and 2017; the data were collected systematically and imaging studies were scored blinded.

Results

Pulmonary symptoms including dyspnea, coughing, need for oxygen, and clubbing started 3.3 years before the diagnosis was made at the mean age of 8.83 years (range 2-15). All children had recurrent pulmonary infections, 3 had a spontaneous pneumothorax, and 4 developed scoliosis. The frequency of pulmonary complaints increased over time. The leading radiographic pattern was ground-glass opacities with a rapid increase in reticular pattern and traction bronchiectasis between initial and follow-up Computer tomography (CT) in all subjects. Honeycombing and cysts were newly detectable in 3 patients. Half of the patients received a lung biopsy for diagnosis; histological patterns were cellular non-specific interstitial pneumonia, usual interstitial pneumonia-like, and desquamative interstitial pneumonia.

Conclusions

HPS-2 is characterized by a rapidly fibrosing lung disease during early childhood. Effective treatments are required.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0780-z) contains supplementary material, which is available to authorized users.

Hermansky-Pudlak syndrome: Report of two patients with updated genetic classification and management recommendations

Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive disorder caused by mutations in one of nine genes involved in the packaging and formation of specialized lysosomes, including melanosomes and platelet-dense granules. The cardinal features are pigmentary dilution, bleeding diathesis, and accumulation of ceroid-like material in reticuloendothelial cells. Pulmonary fibrosis induced by tissue damage is seen in the most severe forms, and one subtype is characterized by immunodeficiency. We describe two patients with HPS type 1 and review the updated gene-based classification, clinical features, and recommendations for evaluation and follow-up.

Pulmonary Fibrosis in Hermansky-Pudlak Syndrome

Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive genetic disorder characterized by oculocutaneous albinism and a bleeding diathesis due to platelet dysfunction. More than 50% of cases worldwide are diagnosed on the Caribbean island of Puerto Rico. Genetic testing plays a growing role in diagnosis; however, not all patients with HPS have identified genetic mutations. In Puerto Rico, patients with HPS are often identified shortly after birth by their albinism, although the degree of hypopigmentation is highly variable. Ten subtypes have been described. Patients with HPS-1, HPS-2, and HPS-4 tend to develop pulmonary fibrosis in Puerto Rico; 100% of patients with HPS-1 develop HPS-PF. HPS-PF and idiopathic pulmonary fibrosis are considered similar entities (albeit with distinct causes) because both can show similar histological disease patterns. However, in contrast to idiopathic pulmonary fibrosis, HPS-PF manifests much earlier, often at 30-40 years of age. The progression of HPS-PF is characterized by the development of dyspnea and increasingly debilitating hypoxemia. No therapeutic interventions are currently approved by the U.S. Food and Drug Administration for the treatment of HPS and HPS-PF. However, the approval of two new antifibrotic drugs, pirfenidone and nintedanib, has prompted new interest in identifying drugs capable of reversing or halting the progression of HPS-PF. Thus, lung transplantation remains the only potentially life-prolonging treatment. At present, two clinical trials are recruiting patients with HPS-PF to identify biomarkers for disease progression. Advances in the diagnosis and management of these patients will require the establishment of multidisciplinary centers of excellence staffed by experts in this disease.

Clinico-molecular analysis of eleven patients with Hermansky-Pudlak type 5 syndrome, a mild form of HPS

Hermansky-Pudlak syndrome (HPS), first described in 1959, is a rare form of syndromic oculocutaneous albinism associated with bleeding diathesis and in some cases pulmonary fibrosis and granulomatous colitis. All 10 HPS types are caused by defects in vesicle trafficking of lysosome-related organelles (LRO) proteins. The HPS5 protein associates with HPS3 and HPS6 to form the biogenesis of lysosome-related organelles complex-2 (BLOC-2). Here, we report the clinical and genetic data of 11 patients with HPS-5 analyzed in our laboratory. We report 11 new pathogenic variants. The 11 patients present with ocular features that are typical for albinism, with mild hypopigmentation, and with no other major complication, apart from a tendency to bleed. HPS-5 therefore appears as a mild form of HPS, which is often clinically undistinguishable from mild oculocutaneous or ocular forms of albinism. Molecular analysis is therefore required to establish the diagnosis of this mild HPS form, which has consequences in terms of prognosis and of clinical management of the patients.

Cellular and molecular defects in a patient with Hermansky-Pudlak syndrome type 5

Hermansky-Pudlak syndrome (HPS) is a heterogeneous group of genetic disorders typically manifesting with tyrosinase-positive oculocutaneous albinism, bleeding diathesis, and pulmonary fibrosis, in some subtypes. Most HPS subtypes are associated with defects in Biogenesis of Lysosome-related Organelle Complexes (BLOCs), which are groups of proteins that function together in the formation and/or trafficking of lysosomal-related endosomal compartments. BLOC-2, for example, consists of the proteins HPS3, HPS5, and HPS6. Here we present an HPS patient with defective BLOC-2 due to a novel intronic mutation in HPS5 that activates a cryptic acceptor splice site. This mutation leads to the insertion of nine nucleotides in-frame and results in a reduced amount of HPS5 at the transcript and protein level. In studies using skin fibroblasts derived from the proband and two other individuals with HPS-5, we found a perinuclear distribution of acidified organelles in patient cells compared to controls. Our results suggest the role of HPS5 in the endo-lysosomal dynamics of skin fibroblasts.

NGS-based 100-gene panel of hypopigmentation identifies mutations in Chinese Hermansky-Pudlak syndrome patients

Hermansky-Pudlak syndrome (HPS) is a rare recessive disorder characterized by hypopigmentation, bleeding diathesis, and other symptoms due to multiple defects in lysosome-related organelles. Ten HPS subtypes have been identified with mutations in HPS1 to HPS10. Only four patients with HPS-1 have been reported in Chinese population. Using next-generation sequencing (NGS), we have screened 100 hypopigmentation genes and identified four HPS-1, two HPS-3, one HPS-5, and three HPS-6 in Chinese HPS patients with typical ocular or oculocutaneous albinism and the absence of platelet dense granules together with other variable phenotypes. All these patients except one homozygote were compound heterozygotes. Among these mutations, 14 were previously unreported alleles (four in HPS1, three in HPS3, two in HPS5, five in HPS6). Our results demonstrate the feasibility and utility of NGS-based panel diagnostics for HPS. Genotyping of HPS subtypes is a prerequisite for intervention of subtype-specific symptoms.

A cross-sectional examination of visual acuity by specific type of albinism

PURPOSE

Reports of best-corrected visual acuity (BCVA) in albinism are often based on overlapping clinical phenotypes. BCVA in albinism has been shown to improve with age. This study reports a large cross-sectional investigation to determine whether BCVA differs by specific type of albinism when age-corrected.

METHODS

This retrospective review identified 170 individuals with a specific type of albinism identified by mutation(s) in a gene known to cause albinism (for OCA1, OCA2, and Hermansky-Pudlak syndrome ([HPS]) or a specific phenotype (white hair and no melanin pigment in OCA1A; pigmentary mosaicism in the obligate carriers for males with OA1). We recorded optotype binocular BCVA at final follow-up. Patients were age-grouped (2-5 years, 6-14 years, and ≥15 years) for comparison.

RESULTS

The greatest visual acuity deficit was found for OCA1A in all age groups. At age ≥15 years (n = 79), mean BCVA was 20/128 for OCA1A, 20/37 for OCA1B, 20/59 for OCA2, 20/63 for OA1, and 20/121 for HPS. Significant differences between BCVA at ≥15 years were found in the following: OCA1A vs OCA1B, OCA1A vs OCA2, OCA1A vs OA1, OCA1B vs HPS, OCA2 vs HPS, and OA1 vs HPS (P ≤ 0.02).

CONCLUSIONS

This study provides a large sample size and includes only those with a specific type of albinism. BCVA varies by albinism type, and there is overlap in BCVA, particularly in the younger age groups. For ages ≥15 years, there are significant differences in BCVA between several types of albinism.

Hermansky-Pudlak Syndrome

Hermansky-Pudlak syndrome (HPS) is an autosomal recessive disorder that is associated with oculocutaneous albinism, bleeding diatheses, granulomatous colitis, and highly penetrant pulmonary fibrosis in some subtypes, including HPS-1, HPS-2, and HPS-4. HPS pulmonary fibrosis shows many of the clinical, radiologic, and histologic features found in idiopathic pulmonary fibrosis, but occurs at a younger age. Despite knowledge of the underlying genetic defects, there are currently no definitive therapeutic or preventive approaches for HPS pulmonary fibrosis other than lung transplant.

Hermansky-Pudlak syndrome. Overview of clinical and molecular features and case report of a new HPS-1 variant

Hermansky-Pudlak syndrome (HPS) is a rare, autosomal recessive disorder affecting lysosome-related organelles (LRO), including dense platelet granules. HPS causes oculocutaneous hypopigmentation, bleeding diathesis and granulomatous colitis or pulmonary fibrosis. To date, there is no curative treatment and the clinical management depends on the severity of symptoms. A prompt diagnosis of HPS patients could improve their quality of life and clinical management. However, the absence of a specific platelet function test, the wide molecular heterogeneity, and the lack of phenotype-genotype correlations hamper the rapid diagnosis. Nine subtypes of HPS have been identified as a result of mutations in nine genes that codify for proteins involved in formation and shuttle of the LRO. The molecular characterization of patients and knowledge derived from animal models of HPS contribute to the understanding of biogenesis and function of the LRO. This paper describes a patient with a novel homozygous nonsense mutation causing HPS and provides a review of the literature focusing on recent advances in the molecular characterization and physiopathology of HPS.

snow white, a zebrafish model of Hermansky-Pudlak Syndrome type 5

Hermansky-Pudlak Syndrome (HPS) is a set of genetically heterogeneous diseases caused by mutations in one of nine known HPS genes. HPS patients display oculocutaneous hypopigmentation and bleeding diathesis and, depending on the disease subtype, pulmonary fibrosis, congenital nystagmus, reduced visual acuity, and platelet aggregation deficiency. Mouse models for all known HPS subtypes have contributed greatly to our understanding of the disease, but many of the molecular and cellular mechanisms underlying HPS remain unknown. Here, we characterize ocular defects in the zebrafish (Danio rerio) mutant snow white (snw), which possesses a recessive, missense mutation in hps5 (hps5I76N). Melanosome biogenesis is disrupted in snw/hps5 mutants, resulting in hypopigmentation, a significant decrease in the number, size, and maturity of melanosomes, and the presence of ectopic multi-melanosome clusters throughout the mutant retina and choroid. snw/hps5I76N is the first Hps5 mutation identified within the N-terminal WD40 repeat protein-protein binding domain. Through in vitro coexpression assays, we demonstrate that Hps5I76N retains the ability to bind its protein complex partners, Hps3 and Hps6. Furthermore, while Hps5 and Hps6 stabilize each other's expression, this stabilization is disrupted by Hps5I76N. The snw/hps5I76N mutant provides a valuable resource for structure-function analyses of Hps5 and enables further elucidation of the molecular and cellular mechanisms underlying HPS.