Classification and challenges in the histopathological diagnosis of peripheral T-cell lymphomas, emphasis on the WHO-HAEM5 updates

Mature T-cell lymphomas represent neoplastic expansions of T-cell lymphocytes with a post-thymic derivation. Most of these tumors feature aggressive clinical behavior and challenging histopathological diagnosis and classification. Novel findings in the genomic landscape of T-cell lymphomas are helping to improve the understanding of the biology and the molecular mechanisms that underly its clinical behavior. The most recent WHO-HAEM5 classification of hematolymphoid tumors introduced novel molecular and histopathological findings that will aid in the diagnostic classification of this group of neoplasms. The current review article summarizes the most relevant diagnostic features of peripheral T-cell lymphomas with an emphasis on the updates that are incorporated at the WHO-HAEM5

Aurora-A and Polo-Like Kinases are Important Diagnostic and Therapeutic Markers in Hodgkin Lymphoma and Mimics

Background: Aurora-A (AA) and Polo-like kinases (PLK) are mitotic kinases that regulate the G2/M phase of the cell cycle. It has been demonstrated that AA acts as an upstream regulator of PLK, mediating its phosphorylation in the presence of a cofactor named Bora. PLK is activated by AA to promote checkpoint recovery in mitosis. AA and PLK are implicated in the tumorigenesis of solid tumors, and, recently, in B- and T-cell non Hodgkin lymphomas (NHL). They play a key role in tumor proliferation and disease progression in highly aggressive B-cell NHL. They also serve as indicators of disease activity and are thus attractive potential therapeutic targets. Expression of AA and/or PLK has not yet been assessed in Classic Hodgkin Lymphoma (CHL) and its mimics. This study assesses AA and PLK expression in different CHL types, such as nodular sclerosis type, mixed cellularity type, and lymphocyte rich type, and their mimics: nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) and primary mediastinal B-cell lymphoma (PMBL).Design:We assessed 27 CHL cases, 16 NLPHL cases, and 8 PMBL cases for AA and PLK expression by immunohistochemistry. CHL cases included the following: 8 mixed cellularity CHL, 1 lymphocyte rich CHL, and 18 nodular sclerosis CHL. A mouse monoclonal AA-antibody (1:1000 dilution, Abcam, UK) and a PLK-antibody (1:500 dilution, Cell Signaling Technologies, USA) were used. Each case was semi-quantitatively graded for percentage of positive cells (\u3c50% vs. \u3e50%), for staining intensity (1-3+), and for localization (nuclear vs. cytoplasmic). Immunohistochemical analysis was performed independently by 2 pathologists (KMH and KVI). Statistical analysis was performed using Fisher\u27s exact test.Results:AA was expressed in 100% of CHL and NLPHL cases. AA stained predominantly cytoplasm of tumor cells in both NLPHL and CHL. PLK was expressed in 100% of NLPHL and 96% of CHL cases (1 mixed cellularity type CHL did not stain for PLK). PLK showed both nuclear and cytoplasmic staining for both NLPHL and CHL. In contrast, only 37% of PMBL cases were positive for AA and PLK (Table 1). In the CHL group, cases with more than 50% of tumor cells expressing PLK tended to present with higher stage and extranodal disease. In the NLPHL group, PLK correlated with higher stage (III-IV) disease at presentation (p=0.044). No statistically significant differences were found in either intensity or localization of AA or PLK within or between NLPHL and CHL cohorts.Aurora-A PositiveAurora-A NegativePLK PositivePLK NegativeClassic Hodgkin Lymphoma270261Nodular Lymphocyte Predominant Hodgkin Lymphoma160160Primary Mediastinal B-cell Lymphoma3535Table 1. AA and PLK positivity in CHL, NLPHL, and PMBL.AA was expressed in CHL but not PMBL (p=0.0002)PLK was expressed in CHL but not PMBL (p=0.0009)AA was expressed in NLPHL but not PMBL (p=0.0013)PLK was expressed in NLPHL but not PMBL (p=0.0013). Conclusion: AA and PLK are commonly expressed in CHL and NLPHL but not in PMBL. Thus, they are useful markers in the distinction of CHL or NLPHL from PMBL. PLK is a useful marker for the prognostication of NLPHL. AA and PLK are attractive potential therapeutic targets in the treatment of CHL and NLPHL. Additional studies are underway to characterize an array of hematopoietic lesions known to overlap with CHL.https://scholarlycommons.henryford.com/merf2019clinres/1027/thumbnail.jp

Three novel polymorphic microsatellite markers for the glaucoma locus GLC1B by datamining tetranucleotide repeats on chromosome 2p12-q12

In order to identify new markers around the glaucoma locus GLC1B as a tool to refine its critical region at 2p11.2-2q11.2, we searched the critical region sequence obtained from the UCSC database for tetranucleotide (GATA)n and (GTCT)n repeats of at least 10 units in length. Three out of four potential microsatellite loci were found to be polymorphic, heterozygosity ranging from 64.56% to 79.59%. The identified markers are useful not only for GLC1B locus but also for the study of other disease loci at 2p11.2-2q11.2, a region with scarcity of microsatellite markers

Interaction of retinitis pigmentosa GTPase regulator (RPGR) with RAB8A GTPase: implications for cilia dysfunction and photoreceptor degeneration

Defects in biogenesis or function(s) of primary cilia are associated with numerous inherited disorders (called ciliopathies) that may include retinal degeneration phenotype. The cilia-expressed gene RPGR (retinitis pigmentosa GTPase regulator) is mutated in patients with X-linked retinitis pigmentosa (XLRP) and encodes multiple protein isoforms with a common N-terminal domain homologous to regulator of chromosome condensation 1 (RCC1), a guanine nucleotide exchange factor (GEF) for Ran GTPase. RPGR interacts with several ciliopathy proteins, such as RPGRIP1L and CEP290; however, its physiological role in cilia-associated functions has not been delineated. Here, we report that RPGR interacts with the small GTPase RAB8A, which participates in cilia biogenesis and maintenance. We show that RPGR primarily associates with the GDP-bound form of RAB8A and stimulates GDP/GTP nucleotide exchange. Disease-causing mutations in RPGR diminish its interaction with RAB8A and reduce the GEF activity. Depletion of RPGR in hTERT-RPE1 cells interferes with ciliary localization of RAB8A and results in shorter primary cilia. Our data suggest that RPGR modulates intracellular localization and function of RAB8A. We propose that perturbation of RPGR–RAB8A interaction, at least in part, underlies the pathogenesis of photoreceptor degeneration in XLRP caused by RPGR mutations

Rpgrip1 is required for rod outer segment development and ciliary protein trafficking in zebrafish

The authors would like to thank the Royal Society of London, the National Eye Research Centre, the Visual Research Trust, Fight for Sight, the W.H. Ross Foundation, the Rosetrees Trust, and the Glasgow Children’s Hospital Charity for supporting this work. This work was also supported by the Deanship of Scientific Research at King Saud University for funding this research (Research Project) grant number ‘RGP – VPP – 219’.Mutations in the RPGR-interacting protein 1 (RPGRIP1) gene cause recessive Leber congenital amaurosis (LCA), juvenile retinitis pigmentosa (RP) and cone-rod dystrophy. RPGRIP1 interacts with other retinal disease-causing proteins and has been proposed to have a role in ciliary protein transport; however, its function remains elusive. Here, we describe a new zebrafish model carrying a nonsense mutation in the rpgrip1 gene. Rpgrip1homozygous mutants do not form rod outer segments and display mislocalization of rhodopsin, suggesting a role for RPGRIP1 in rhodopsin-bearing vesicle trafficking. Furthermore, Rab8, the key regulator of rhodopsin ciliary trafficking, was mislocalized in photoreceptor cells of rpgrip1 mutants. The degeneration of rod cells is early onset, followed by the death of cone cells. These phenotypes are similar to that observed in LCA and juvenile RP patients. Our data indicate RPGRIP1 is necessary for rod outer segment development through regulating ciliary protein trafficking. The rpgrip1 mutant zebrafish may provide a platform for developing therapeutic treatments for RP patients.Publisher PDFPeer reviewe

\u3cem\u3eRPGRIP1\u3c/em\u3e and Cone-Rod Dystrophy in Dogs

Cone–rod dystrophies (crd) represent a group of progressive inherited blinding diseases characterized by primary dysfunction and loss of cone photoreceptors accompanying or preceding rod death. Recessive crd type 1 was described in dogs associated with an RPGRIP1 exon 2 mutation, but with lack of complete concordance between genotype and phenotype. This review highlights role of the RPGRIP1, a component of complex protein networks, and its function in the primary cilium, and discusses the potential mechanisms of genotype–phenotype discordance observed in dogs with the RPGRIP1 mutation

The N-terminal region of centrosomal protein 290 (CEP290) restores vision in a zebrafish model of human blindness

The gene coding for centrosomal protein 290 (CEP290), a large multidomain protein, is the most frequently mutated gene underlying the non-syndromic blinding disorder Leber's congenital amaurosis (LCA). CEP290 has also been implicated in several cilia-related syndromic disorders including Meckel–Gruber syndrome, Joubert syndrome, Senor–Loken syndrome and Bardet–Biedl syndrome (BBS). In this study, we characterize the developmental and functional roles of cep290 in zebrafish. An antisense oligonucleotide [Morpholino (MO)], designed to generate an altered cep290 splice product that models the most common LCA mutation, was used for gene knockdown. We show that cep290 MO-injected embryos have reduced Kupffer's vesicle size and delays in melanosome transport, two phenotypes that are observed upon knockdown of bbs genes in zebrafish. Consistent with a role in cilia function, the cep290 MO-injected embryos exhibited a curved body axis. Patients with LCA caused by mutations in CEP290 have reduced visual perception, although they present with a fully laminated retina. Similarly, the histological examination of retinas from cep290 MO-injected zebrafish revealed no gross lamination defects, yet the embryos had a statistically significant reduction in visual function. Finally, we demonstrate that the vision impairment caused by the disruption of cep290 can be rescued by expressing only the N-terminal region of the human CEP290 protein. These data reveal that a specific region of the CEP290 protein is sufficient to restore visual function and this region may be a viable gene therapy target for LCA patients with mutations in CEP290

Gelsolin dysfunction causes photoreceptor loss in induced pluripotent cell and animal retinitis pigmentosa models

Mutations in the Retinitis Pigmentosa GTPase Regulator (RPGR) cause X-linked RP (XLRP), an untreatable, inherited retinal dystrophy that leads to premature blindness. RPGR localises to the photoreceptor connecting cilium where its function remains unknown. Here we show, using murine and human induced pluripotent stem cell models, that RPGR interacts with and activates the actin-severing protein gelsolin, and that gelsolin regulates actin disassembly in the connecting cilium, thus facilitating rhodopsin transport to photoreceptor outer segments. Disease-causing RPGR mutations perturb this RPGR-gelsolin interaction, compromising gelsolin activation. Both RPGR and Gelsolin knockout mice show abnormalities of actin polymerisation and mislocalisation of rhodopsin in photoreceptors. These findings reveal a clinically-significant role for RPGR in the activation of gelsolin, without which abnormalities in actin polymerisation in the photoreceptor connecting cilia cause rhodopsin mislocalisation and eventual retinal degeneration in XLRP.Mutations in the Retinitis Pigmentosa GTPase Regulator (RPGR) cause retinal dystrophy, but how this arises at a molecular level is unclear. Here, the authors show in induced pluripotent stem cells and mouse knockouts that RPGR mediates actin dynamics in photoreceptors via the actin-severing protein, gelsolin

Functional Analysis of Retinitis Pigmentosa 2 (RP2) Protein Reveals Variable Pathogenic Potential of Disease-Associated Missense Variants

Genetic mutations are frequently associated with diverse phenotypic consequences, which limits the interpretation of the consequence of a variation in patients. Mutations in the retinitis pigmentosa 2 (RP2) gene are associated with X-linked RP, which is a phenotypically heterogenic form of retinal degeneration. The purpose of this study was to assess the functional consequence of disease-associated mutations in the RP2 gene using an in vivo assay. Morpholino-mediated depletion of rp2 in zebrafish resulted in perturbations in photoreceptor development and microphthalmia (small eye). Ultrastructural and immunofluorescence analyses revealed defective photoreceptor outer segment development and lack of expression of photoreceptor-specific proteins. The retinopathy phenotype could be rescued by expressing the wild-type human RP2 protein. Notably, the tested RP2 mutants exhibited variable degrees of rescue of rod versus cone photoreceptor development as well as microphthalmia. Our results suggest that RP2 plays a key role in photoreceptor development and maintenance in zebrafish and that the clinical heterogeneity associated with RP2 mutations may, in part, result from its potentially distinct functional relevance in rod versus cone photoreceptors