Detection of BCR-ABL kinase domain mutations in CD34+ cells from newly diagnosed chronic phase CML patients and their association with imatinib resistance

BCR-ABL kinase domain (KD) mutations, the most common cause of imatinib resistance, are infrequently detected in newly diagnosed chronic-phase chronic myeloid leukemia (CP-CML) patients. Recent studies indicate pre-existing mutations (PEMs) can be detected in a higher percentage of CML patients using CD34+ stem/progenitor cells, and these mutations may correlate with imatinib resistance. We investigated KD mutations in CD34+ stem cells from 100 CP-CML patients by multiplex ASO-PCR and sequencing ASO-PCR products at the time of diagnosis. PEMs were detected in 32/100 patients and included F311L, M351T, and T315I. After a median follow-up of 30 months (range 8-48), all patients with PEMs exhibited imatinib resistance. Of 68 patients without PEMs, 24 developed imatinib resistance. Mutations were detected in 21 of these patients by ASO-PCR and KD sequencing. All 32 patients with PEMs had the same mutations. In imatinib-resistant patients without PEMs, we detected F311L, M351T, Y253F, and T315I mutations. All imatinib-resistant patients without T315I and Y253F mutations responded to imatinib dose escalation. In conclusion, BCR-ABL PEMs can be detected in a substantial number of CP-CML patients when investigated using CD34+ stem/progenitor cells. These mutations are associated with imatinib resistance, and mutation testing using CD34+ cells may facilitate improved, patient-tailored treatment

The effect of alternative splicing on key regulators of the integrated stress response

Indiana University-Purdue University Indianapolis (IUPUI)The protein kinase General control non-derepressible-2 (GCN2) is a key regulator of the Integrated stress response that responds to various stress signals, including nutritional deprivation. As a result of high levels of uncharged tRNAs during amino acid depletion, GCN2 phosphorylates serine-51 of the α subunit of eukaryotic initiation factor-2 (eIF2), a translation factor that delivers initiator tRNA to ribosomes. Phosphorylation of eIF2α inhibits general translation, which conserves energy and nutrients and facilitates reprogramming of gene expression for remediation of stress damage. Phosphorylation of eIF2α also directs preferential translation of specific transcription factors, such as ATF4. ATF4 reprograms gene expression to alleviate stress damage; however, under chronic stress, ATF4 directs the transcriptional expression of CHOP, which can trigger apoptosis. Because multiple stresses can induce eIF2α phosphorylation and translational control in mammals, this pathway is referred to as the Integrated stress response. GCN2 and CHOP are subject to alternative splicing that results in multiple transcripts that differ in the 5'-end of the gene transcripts. However, the effect of the different GCN2 and CHOP isoforms on their function and regulation have not been investigated. Our data suggests that GCN2 is alternatively spliced into five different transcripts and the beta isoform of GCN2 is most abundant. Also alternative splicing of CHOP creates two CHOP transcripts with different 5'-leaders encoding inhibitory upstream open reading frames that are critical for translational control of CHOP during stress. This study suggests that alternative splicing can play an integral role in the implementation and regulation of key factors in the Integrated stress response

RNA markers enable phenotypic test of antibiotic susceptibility in Neisseria gonorrhoeae after 10 minutes of ciprofloxacin exposure

Antimicrobial-resistant Neisseria gonorrhoeae is an urgent public-health threat, with continued worldwide incidents of infection and rising resistance to antimicrobials. Traditional culture-based methods for antibiotic susceptibility testing are unacceptably slow (1–2 days), resulting in the use of broad-spectrum antibiotics and the further development and spread of resistance. Critically needed is a rapid antibiotic susceptibility test (AST) that can guide treatment at the point-of-care. Rapid phenotypic approaches using quantification of DNA have been demonstrated for fast-growing organisms (e.g. E. coli) but are challenging for slower-growing pathogens such as N. gonorrhoeae. Here, we investigate the potential of RNA signatures to provide phenotypic responses to antibiotics in N. gonorrhoeae that are faster and greater in magnitude compared with DNA. Using RNA sequencing, we identified antibiotic-responsive transcripts. Significant shifts (>4-fold change) in transcript levels occurred within 5 min of antibiotic exposure. We designed assays for responsive transcripts with the highest abundances and fold changes, and validated gene expression using digital PCR. Using the top two markers (porB and rpmB) we correctly determined the antibiotic susceptibility and resistance of 49 clinical isolates after 10 min exposure to ciprofloxacin. RNA signatures are therefore promising as an approach on which to build rapid AST devices for N. gonorrhoeae at the point-of-care, which is critical for disease management, surveillance, and antibiotic stewardship efforts

In vitro expanded human CD4+CD25+ regulatory T cells suppress effector T cell proliferation.

Regulatory T cells (Tregs) have been shown to be critical in the balance between autoimmunity and tolerance and have been implicated in several human autoimmune diseases. However, the small number of Tregs in peripheral blood limits their therapeutic potential. Therefore, we developed a protocol that would allow for the expansion of Tregs while retaining their suppressive activity. We isolated CD4+CD25 hi cells from human peripheral blood and expanded them in vitro in the presence of anti-CD3 and anti-CD28 magnetic Xcyte Dynabeads and high concentrations of exogenous Interleukin (IL)-2. Tregs were effectively expanded up to 200-fold while maintaining surface expression of CD25 and other markers of Tregs: CD62L, HLA-DR, CCR6, and FOXP3. The expanded Tregs suppressed proliferation and cytokine secretion of responder PBMCs in co-cultures stimulated with anti-CD3 or alloantigen. Treg expansion is a critical first step before consideration of Tregs as a therapeutic intervention in patients with autoimmune or graft-versus-host disease

Epigenetic Modifications in the Biology of Nonalcoholic Fatty Liver Disease: The Role of DNA-Hydroxymethylation and TET Proteins

The 5-Hydroxymethylcytosine (5-hmC) is an epigenetic modification whose role in the pathogenesis of metabolic-related complex diseases remains unexplored; 5-hmC appears to be prevalent in the mitochondrial genome. The Ten-Eleven-Translocation (TET) family of proteins is responsible for catalyzing the conversion of 5-methylcytosine to 5-hmC. We hypothesized that epigenetic editing by 5-hmC might be a novel mechanism through which nonalcoholic fatty liver disease (NAFLD)-associated molecular traits could be explained. Hence, we performed an observational study to explore global levels of 5-hmC in fresh liver samples of patients with NAFLD and controls (n = 90) using an enzyme-linked-immunosorbent serologic assay and immunohistochemistry. We also screened for genetic variation in TET 1–3 loci by next generation sequencing to explore its contribution to the disease biology. The study was conducted in 2 stages (discovery and replication) and included 476 participants. We observed that the amount of 5-hmC in the liver of both NAFLD patients and controls was relatively low (up to 0.1%); a significant association was found with liver mitochondrial DNA copy number (R = 0.50, P = 0.000382) and PPARGC1A-mRNA levels (R = −0.57, P = 0.04). We did not observe any significant difference in the 5-hmC nuclear immunostaining score between NAFLD patients and controls; nevertheless, we found that patients with NAFLD (0.4 ± 0.5) had significantly lower nonnuclear-5-hmC staining compared with controls (1.8 ± 0.8), means ± standard deviation, P = 0.028. The missense p.Ile1123Met variant (TET1-rs3998860) was significantly associated with serum levels of caspase-generated CK-18 fragment-cell death biomarker in the discovery and replication stage, and the disease severity (odds ratio: 1.47, 95% confidence interval: 1.10–1.97; P = 0.005). The p.Ile1762Val substitution (TET2-rs2454206) was associated with liver PPARGC1A-methylation and transcriptional levels, and Type 2 diabetes. Our results suggest that 5-hmC might be involved in the pathogenesis of NAFLD by regulating liver mitochondrial biogenesis and PPARGC1A expression. Genetic diversity at TET loci suggests an “epigenetic” regulation of programmed liver-cell death and a TET-mediated fine-tuning of the liver PPARGC1A-transcriptional program.Fil: Pirola, Carlos José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Médicas. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; ArgentinaFil: Scian, Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Médicas. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; ArgentinaFil: Fernández Gianotti, Tomás. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Médicas. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; ArgentinaFil: Dopazo, Hernán Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Rohr, Cristian Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: San Martino, Julio. Provincia de Buenos Aires. Ministerio de Salud. Hospital Municipal Dr. Diego Thompson; ArgentinaFil: Castaño, Gustavo Osvaldo. Gobierno de la Ciudad de Buenos Aires. Hospital "Dr. Abel Zubizarreta"; ArgentinaFil: Sookoian, Silvia Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Médicas. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; Argentin

A2BP1 as a novel susceptible gene for primary biliary cirrhosis in Japanese patients

Primary biliary cirrhosis (PBC) is a complex autoimmune liver disease with an etiology that remains to be conclusively elucidated. As such, we screened the human genome for genes that might influence PBC susceptibility or resistance using 400 microsatellite markers. A strong candidate gene indicated by susceptibility microsatellite markers was further evaluated by association analysis using single nucleotide polymorphisms (SNPs). A total of 126 patients with PBC and 95 healthy Japanese controls were enrolled. Four candidate susceptible regions and seven candidate protective regions were statistically associated with PBC. Because the D16S423 marker on chromosome 16p showed the strongest evidence of linkage, the protein-coding gene ataxin 2-binding protein 1 (A2BP1) lying 27 kb on the centromeric side of D16S423 was targeted as a candidate susceptible gene. Seven SNPs (rs17139207, rs12926282, rs17139244, rs6500742, rs4146812, rs4124065, and rs889699) in the A2BP1 gene were genotyped in patients and controls. The rs17139244 SNP was found to be weakly associated with PBC in an additive model. The genotype frequency of the major C allele at rs6500742 was significantly associated with PBC, compared with healthy controls. This study showed a total of 11 candidate PBC susceptibility or resistance regions. In particular, the A2BP1 gene might play a pivotal role for susceptibility to PBC.ArticleHUMAN IMMUNOLOGY. 71(5):520-524 (2010)journal articl

The Expanding Landscape of Alternative Splicing Variation in Human Populations.

Alternative splicing is a tightly regulated biological process by which the number of gene products for any given gene can be greatly expanded. Genomic variants in splicing regulatory sequences can disrupt splicing and cause disease. Recent developments in sequencing technologies and computational biology have allowed researchers to investigate alternative splicing at an unprecedented scale and resolution. Population-scale transcriptome studies have revealed many naturally occurring genetic variants that modulate alternative splicing and consequently influence phenotypic variability and disease susceptibility in human populations. Innovations in experimental and computational tools such as massively parallel reporter assays and deep learning have enabled the rapid screening of genomic variants for their causal impacts on splicing. In this review, we describe technological advances that have greatly increased the speed and scale at which discoveries are made about the genetic variation of alternative splicing. We summarize major findings from population transcriptomic studies of alternative splicing and discuss the implications of these findings for human genetics and medicine

A novel human-specific splice isoform alters the critical C-terminus of Survival Motor Neuron protein

Spinal muscular atrophy (SMA), a leading genetic disease of children and infants, is caused by mutations or deletions of Survival Motor Neuron 1 (SMN1) gene. SMN2, a nearly identical copy of SMN1, fails to compensate for the loss of SMN1 due to skipping of exon 7. SMN2predominantly produces SMNΔ7, an unstable protein. Here we report exon 6B, a novel exon, generated by exonization of an intronic Alu-like sequence of SMN. We validate the expression of exon 6B-containing transcripts SMN6B and SMN6BΔ7 in human tissues and cell lines. We confirm generation of SMN6B transcripts from both SMN1 and SMN2. We detect expression of SMN6B protein using antibodies raised against a unique polypeptide encoded by exon 6B. We analyze RNA-Seq data to show that hnRNP C is a potential regulator of SMN6B expression and demonstrate that SMN6B is a substrate of nonsense-mediated decay. We show interaction of SMN6B with Gemin2, a critical SMN-interacting protein. We demonstrate that SMN6B is more stable than SMNΔ7 and localizes to both the nucleus and the cytoplasm. Our finding expands the diversity of transcripts generated from human SMN genes and reveals a novel protein isoform predicted to be stably expressed during conditions of stress