Transient receptor potential (TRP) genes of the mucolipin subfamily (TRPML1-3 and MCOLN1-3) are presumed to encode ion channel proteins of intracellular endosomes and lysosomes. Mutations in human TRPML1 (mucolipin 1/MCOLN1) result in mucolipidosis type IV, a severe inherited neurodegenerative disease associated with defective lysosomal biogenesis and trafficking. A mutation in mouse TRPML3 (A419P; TRPML3 Va ) results in the varitint-waddler (Va) phenotype. Va mice are deaf, exhibit circling behavior due to vestibular defects, and have variegated/dilute coat color as a result of pigmentation defects. Prior electrophysiological studies of presumed TRPML plasma membrane channels are contradictory and inconsistent with known TRP channel properties. Here, we report that the Va mutation produces a gain-of-function that allows TRPML1 and TRPML3 to be measured and identified as inwardly rectifying, proton-impermeant, Ca 2؉ -permeant cation channels. TRPML3 is highly expressed in normal melanocytes. Melanocyte markers are lost in the Va mouse, suggesting that their variegated and hypopigmented fur is caused by severe alteration of melanocyte function or cell death. TRPML3 Va expression in melanocyte cell lines results in high resting Ca 2؉ levels, rounded, poorly adherent cells, and loss of membrane integrity. We conclude that the Va phenotype is caused by mutation-induced TRPML3 gain-of-function, resulting in cell death.calcium channel ͉ lysosome ͉ mucolipidosis ͉ TRPML ͉ hair T RPML1 is a putative intracellular ion channel that colocalizes with late endosomal/lysosomal markers (1-3). TRPML2 and TRPML3 are less well understood but are also presumed to be primarily intracellular channels that mediate ion fluxes across endosomal membranes (4). TRPML3 is mutated in varitintwaddler (Va and VaJ) mice (5). Mice homozygous or heterozygous for the Va (A419P) mutation are deaf and exhibit circling behavior indicative of a vestibular defect. Heterozygotes display a variegated and dilute coat color, whereas homozygotes are almost white and have reduced viability (6). A second mutation in TRPML3 arising in the original Va stock (A419P; I362T) results in a less-severe (VaJ) phenotype (7).Mucolipin channel function is unclear because of conflicting data from heterologously expressed, presumed TRPML currents. TRPML1 was claimed to underlie nonselective outwardly rectifying monovalent (8) or proton-conducting (9) currents, but neither of these results were reproduced by others (1). Here, we show that the A419P mutation in the presumed segment (S)4-S5 linker results in a constitutively active, inwardly rectifying cation channel that can be measured across the cell's plasma membrane. Mutation of the corresponding amino acids in TRPML1 results in similar overall conductance properties. WT TRPML3 is highly expressed in melanocytes, but these cells are lost in Va/Va mice, as assessed by the disappearance of melanocyte markers. Consistent with the toxicity of TRPML3Va expression in melanocyte cell lines, we hypothesize that the loss of fur ...

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Key Points• Translocations between PD-L1 and the IGH locus represent a genetic mechanism of PD-L1 overexpression in DLBCL.• Genetic alterations in the PD-L1/PDL-2 locus are mainly associated with the non-GCB subtype of DLBCL.Diffuse large B-cell lymphoma (DLBCL) is one of the most common and aggressive types of B-cell lymphoma. Deregulation of proto-oncogene expression after a translocation, most notably to the immunoglobulin heavy-chain locus (IGH), is one of the hallmarks of DLBCL. Using whole-genome sequencing analysis, we have identified the PD-L1/PD-L2 locus as a recurrent translocation partner for IGH in DLBCL. PIM1 and TP63 were also identified as novel translocation partners for PD-L1/PD-L2. Fluorescence in situ hybridization was furthermore used to rapidly screen an expanded DLBCL cohort. Collectively, a subset of samples was found to be affected by gains (12%), amplifications (3%), and translocations (4%) of the PD-L1/PD-L2 locus. RNA sequencing data coupled with immunohistochemistry revealed that these cytogenetic alterations correlated with increased expression of PD-L1 but not of PD-L2. Moreover, cytogenetic alterations affecting the PD-L1/PD-L2 locus were more frequently observed in the non-germinal center B cell-like (non-GCB) subtype of DLBCL. These findings demonstrate the genetic basis of PD-L1 overexpression in DLBCL and suggest that treatments targeting the PD-1-PD-L1/PD-L2 axis might benefit DLBCL patients, especially those belonging to the more aggressive non-GCB subtype. (Blood. 2016;127(24):3026-3034)

Hepatitis B virus (HBV) infection is endemic in some parts of Asia, Africa, and South America and remains to be a significant public health problem in these areas. It is known as a leading risk factor for the development of hepatocellular carcinoma, but epidemiological studies have also shown that the infection may increase the incidence of several types of B-cell lymphoma. Here, by characterizing altogether 275 Chinese diffuse large B-cell lymphoma (DLBCL) patients, we showed that patients with concomitant HBV infection (surface antigen positive [HBsAg]) are characterized by a younger age, a more advanced disease stage at diagnosis, and reduced overall survival. Furthermore, by whole-genome/exome sequencing of 96 tumors and the respective peripheral blood samples and targeted sequencing of 179 tumors from these patients, we observed an enhanced rate of mutagenesis and a distinct set of mutation targets in HBsAg DLBCL genomes, which could be partially explained by the activities of APOBEC and activation-induced cytidine deaminase. By transcriptome analysis, we further showed that the HBV-associated gene expression signature is contributed by the enrichment of genes regulated by BCL6, FOXO1, and ZFP36L1. Finally, by analysis of immunoglobulin heavy chain gene sequences, we showed that an antigen-independent mechanism, rather than a chronic antigenic simulation model, is favored in HBV-related lymphomagenesis. Taken together, we present the first comprehensive genomic and transcriptomic study that suggests a link between HBV infection and B-cell malignancy. The genetic alterations identified in this study may also provide opportunities for development of novel therapeutic strategies.

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