Concomitant sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman Disease) and diffuse large B-cell lymphoma: a case report

IntroductionSinus histiocytosis with massive lymphadenopathy, also known as Rosai-Dorfman Disease, is a rare and benign source of lymphadenopathy first described in 1969, which mimics neoplastic processes. This disease commonly presents in children and young adults with supra-diaphragmatic lymphadenopathy or extranodal lesions consisting of tissue infiltrates composed of a polyclonal population of histiocytes. Since its description greater than 400 cases have been described, sometimes in patients with a variety of treated and untreated neoplastic diseases. However, the literature contains reports of only 19 cases of Rosai-Dorfman Disease in association with lymphomas, Hodgkin's or non-Hodgkin's. The majority of these cases have the two diagnoses, malignant lymphoma and Rosai-Dorfman Disease, separated in time. Interestingly, infradiaphragmatic lymphadenopathy was a feature in the majority of previously reported cases of Rosai-Dorfman Disease and non-Hodgkin's lymphoma.Case presentationThis report provides details of a case with co-existing sinus histiocytosis with massive lymphadenopathy and diffuse large B cell non-Hodgkin's lymphoma. This case is the fifth described case of simultaneous Rosai-Dorfman Disease and concurrent non-Hodgkin's lymphoma. Unfortunately, the diagnosis of a clinically aggressive diffuse large B cell lymphoma was made at autopsy. The aggressive biological behavior of the diffuse large B cell lymphoma in this patient may have been related to the underlying immune dysregulation believed to be part of the pathophysiology of Rosai-Dorfman Disease.ConclusionTaken together this report and the preceding reports of Rosai-Dorfman Disease and non-Hodgkin's lymphoma suggests that in cases with a diagnosis of Rosai-Dorfman Disease in the setting of prominent infradiaphragmatic lymphadenopathy, clinicians should maintain a high index of suspicion for the presence of occult non-Hodgkin's lymphoma especially if the clinical course is atypical for classic Rosai-Dorfman Disease

Intronic L1 Retrotransposons and Nested Genes Cause Transcriptional Interference by Inducing Intron Retention, Exonization and Cryptic Polyadenylation

Transcriptional interference has been recently recognized as an unexpectedly complex and mostly negative regulation of genes. Despite a relatively few studies that emerged in recent years, it has been demonstrated that a readthrough transcription derived from one gene can influence the transcription of another overlapping or nested gene. However, the molecular effects resulting from this interaction are largely unknown.Using in silico chromosome walking, we searched for prematurely terminated transcripts bearing signatures of intron retention or exonization of intronic sequence at their 3' ends upstream to human L1 retrotransposons, protein-coding and noncoding nested genes. We demonstrate that transcriptional interference induced by intronic L1s (or other repeated DNAs) and nested genes could be characterized by intron retention, forced exonization and cryptic polyadenylation. These molecular effects were revealed from the analysis of endogenous transcripts derived from different cell lines and tissues and confirmed by the expression of three minigenes in cell culture. While intron retention and exonization were comparably observed in introns upstream to L1s, forced exonization was preferentially detected in nested genes. Transcriptional interference induced by L1 or nested genes was dependent on the presence or absence of cryptic splice sites, affected the inclusion or exclusion of the upstream exon and the use of cryptic polyadenylation signals.Our results suggest that transcriptional interference induced by intronic L1s and nested genes could influence the transcription of the large number of genes in normal as well as in tumor tissues. Therefore, this type of interference could have a major impact on the regulation of the host gene expression

Characterization of LINE-1 Ribonucleoprotein Particles

The average human genome contains a small cohort of active L1 retrotransposons that encode two proteins (ORF1p and ORF2p) required for their mobility (i.e., retrotransposition). Prior studies demonstrated that human ORF1p, L1 RNA, and an ORF2p-encoded reverse transcriptase activity are present in ribonucleoprotein (RNP) complexes. However, the inability to physically detect ORF2p from engineered human L1 constructs has remained a technical challenge in the field. Here, we have employed an epitope/RNA tagging strategy with engineered human L1 retrotransposons to identify ORF1p, ORF2p, and L1 RNA in a RNP complex. We next used this system to assess how mutations in ORF1p and/or ORF2p impact RNP formation. Importantly, we demonstrate that mutations in the coiled-coil domain and RNA recognition motif of ORF1p, as well as the cysteine-rich domain of ORF2p, reduce the levels of ORF1p and/or ORF2p in L1 RNPs. Finally, we used this tagging strategy to localize the L1–encoded proteins and L1 RNA to cytoplasmic foci that often were associated with stress granules. Thus, we conclude that a precise interplay among ORF1p, ORF2p, and L1 RNA is critical for L1 RNP assembly, function, and L1 retrotransposition

Epigenomic plasticity within populations: its evolutionary significance and potential

Epigenetics has progressed rapidly from an obscure quirk of heredity into a data-heavy ‘omic’ science. Our understanding of the molecular mechanisms of epigenomic regulation, and the extent of its importance in nature, are far from complete, but in spite of such drawbacks, population-level studies are extremely valuable: epigenomic regulation is involved in several processes central to evolutionary biology including phenotypic plasticity, evolvability and the mediation of intragenomic conflicts. The first studies of epigenomic variation within populations suggest high levels of phenotypically relevant variation, with the patterns of epigenetic regulation varying between individuals and genome regions as well as with environment. Epigenetic mechanisms appear to function primarily as genome defences, but result in the maintenance of plasticity together with a degree of buffering of developmental programmes; periodic breakdown of epigenetic buffering could potentially cause variation in rates of phenotypic evolution