Rahul Sinha

All Publications

• Screening for genes that regulate the differentiation of human megakaryocytic lineage cells. Proceedings of the National Academy of Sciences of the United States of America Zhu, F., Feng, M., Sinha, R., Seita, J., Mori, Y., Weissman, I. L. 2018

  Abstract

  Different combinations of transcription factors (TFs) function at each stage of hematopoiesis, leading to distinct expression patterns of lineage-specific genes. The identification of such regulators and their functions in hematopoiesis remain largely unresolved. In this study, we utilized screening approaches to study the transcriptional regulators of megakaryocyte progenitor (MkP) generation, a key step before platelet production. Promising candidate genes were generated from a microarray platform gene expression commons and individually manipulated in human hematopoietic stem and progenitor cells (HSPCs). Deletion of some of the candidate genes (the hit genes) by CRISPR/Cas9 led to decreased MkP generation during HSPC differentiation, while more MkPs were produced when some hit genes were overexpressed in HSPCs. We then demonstrated that overexpression of these genes can increase the frequency of mature megakaryocytic colonies by functional colony forming unit-megakaryocyte (CFU-Mk) assay and the release of platelets after in vitro maturation. Finally, we showed that the histone deacetylase inhibitors could also increase MkP differentiation, possibly by regulating some of the newly identified TFs. Therefore, identification of such regulators will advance the understanding of basic mechanisms of HSPC differentiation and conceivably enable the generation and maturation of megakaryocytes and platelets in vitro.

  View details for DOI 10.1073/pnas.1805434115

  View details for PubMedID 30150396

• Computational correction of index switching in multiplexed sequencing libraries NATURE METHODS Larsson, A. M., Stanley, G., Sinha, R., Weissman, I. L., Sandberg, R. 2018; 15 (5): 305–7

  View details for DOI 10.1038/nmeth.4666

  View details for Web of Science ID 000431372700006

  View details for PubMedID 29702636

• Where Hematopoietic Stem Cells Live: The Bone Marrow Niche ANTIOXIDANTS & REDOX SIGNALING Szade, K., Gulati, G. S., Chan, C. F., Kao, K. S., Miyanishi, M., Marjon, K. D., Sinha, R., George, B. M., Chen, J. Y., Weissman, I. L. 2018

  Abstract

  Hematopoietic stem cells (HSCs) can sustain the production of blood throughout one's lifetime. However, for proper self-renewal of its own population and differentiation to blood, the HSC requires a specialized microenvironment called the "niche." Recent Advances: Recent studies using novel mouse models have shed new light on the cellular architecture and function of the HSC niche. Here, we review the different cells that constitute the HSC niche and the molecular mechanisms that underlie HSC and niche interaction. We discuss the evidence and potential features that distinguish the HSC niche from other microenvironments in the bone marrow. The relevance of the niche in malignant transformation of the HSCs and harboring cancer metastasis to the bone is also outlined. In addition, we address how the niche may regulate reactive oxygen species levels surrounding the HSCs. Critical Issues and Future Directions: We propose future directions and remaining challenges in investigating the niche of HSCs. We discuss how a better understanding of the HSC niche may help in restoring an aged hematopoietic system, fighting against malignancies, and transplanting purified HSCs safely and effectively into patients. Antioxid. Redox Signal. 00, 000-000.

  View details for DOI 10.1089/ars.2017.7419

  View details for Web of Science ID 000419559300001

  View details for PubMedID 29113449

• Antisense oligonucleotides correct the familial dysautonomia splicing defect in IKBKAP transgenic mice. Nucleic acids research Sinha, R., Kim, Y. J., Nomakuchi, T., Sahashi, K., Hua, Y., Rigo, F., Bennett, C. F., Krainer, A. R. 2018; 46 (10): 4833–44

  Abstract

  Familial dysautonomia (FD) is a rare inherited neurodegenerative disorder caused by a point mutation in the IKBKAP gene that results in defective splicing of its pre-mRNA. The mutation weakens the 5' splice site of exon 20, causing this exon to be skipped, thereby introducing a premature termination codon. Though detailed FD pathogenesis mechanisms are not yet clear, correcting the splicing defect in the relevant tissue(s), thus restoring normal expression levels of the full-length IKAP protein, could be therapeutic. Splice-switching antisense oligonucleotides (ASOs) can be effective targeted therapeutics for neurodegenerative diseases, such as nusinersen (Spinraza), an approved drug for spinal muscular atrophy. Using a two-step screen with ASOs targeting IKBKAP exon 20 or the adjoining intronic regions, we identified a lead ASO that fully restored exon 20 splicing in FD patient fibroblasts. We also characterized the corresponding cis-acting regulatory sequences that control exon 20 splicing. When administered into a transgenic FD mouse model, the lead ASO promoted expression of full-length human IKBKAP mRNA and IKAP protein levels in several tissues tested, including the central nervous system. These findings provide insights into the mechanisms of IKBKAP exon 20 recognition, and pre-clinical proof of concept for an ASO-based targeted therapy for FD.

  View details for DOI 10.1093/nar/gky249

  View details for PubMedID 29672717

• Single-cell analysis of early progenitor cells that build coronary arteries. Nature Su, T., Stanley, G., Sinha, R., D'Amato, G., Das, S., Rhee, S., Chang, A. H., Poduri, A., Raftrey, B., Dinh, T. T., Roper, W. A., Li, G., Quinn, K. E., Caron, K. M., Wu, S., Miquerol, L., Butcher, E. C., Weissman, I., Quake, S., Red-Horse, K. 2018

  Abstract

  Arteries and veins are specified by antagonistic transcriptional programs. However, during development and regeneration, new arteries can arise from pre-existing veins through a poorly understood process of cell fate conversion. Here, using single-cell RNA sequencing and mouse genetics, we show that vein cells of the developing heart undergo an early cell fate switch to create a pre-artery population that subsequently builds coronary arteries. Vein cells underwent a gradual and simultaneous switch from venous to arterial fate before a subset of cells crossed a transcriptional threshold into the pre-artery state. Before the onset of coronary blood flow, pre-artery cells appeared in the immature vessel plexus, expressed mature artery markers, and decreased cell cycling. The vein-specifying transcription factor COUP-TF2 (also known as NR2F2) prevented plexus cells from overcoming the pre-artery threshold by inducing cell cycle genes. Thus, vein-derived coronary arteries are built by pre-artery cells that can differentiate independently of blood flow upon the release of inhibition mediated by COUP-TF2 and cell cycle factors.

  View details for DOI 10.1038/s41586-018-0288-7

  View details for PubMedID 29973725

• PD-1 expression by tumour-associated macrophages inhibits phagocytosis and tumour immunity. Nature Gordon, S. R., Maute, R. L., Dulken, B. W., Hutter, G., George, B. M., McCracken, M. N., Gupta, R., Tsai, J. M., Sinha, R., Corey, D., Ring, A. M., Connolly, A. J., Weissman, I. L. 2017; 545 (7655): 495-499

  Abstract

  Programmed cell death protein 1 (PD-1) is an immune checkpoint receptor that is upregulated on activated T cells for the induction of immune tolerance. Tumour cells frequently overexpress the ligand for PD-1, programmed cell death ligand 1 (PD-L1), facilitating their escape from the immune system. Monoclonal antibodies that block the interaction between PD-1 and PD-L1, by binding to either the ligand or receptor, have shown notable clinical efficacy in patients with a variety of cancers, including melanoma, colorectal cancer, non-small-cell lung cancer and Hodgkin's lymphoma. Although it is well established that PD-1-PD-L1 blockade activates T cells, little is known about the role that this pathway may have in tumour-associated macrophages (TAMs). Here we show that both mouse and human TAMs express PD-1. TAM PD-1 expression increases over time in mouse models of cancer and with increasing disease stage in primary human cancers. TAM PD-1 expression correlates negatively with phagocytic potency against tumour cells, and blockade of PD-1-PD-L1 in vivo increases macrophage phagocytosis, reduces tumour growth and lengthens the survival of mice in mouse models of cancer in a macrophage-dependent fashion. This suggests that PD-1-PD-L1 therapies may also function through a direct effect on macrophages, with substantial implications for the treatment of cancer with these agents.

  View details for DOI 10.1038/nature22396

  View details for PubMedID 28514441

• Human AML-iPSCs Reacquire Leukemic Properties after Differentiation and Model Clonal Variation of Disease. Cell stem cell Chao, M. P., Gentles, A. J., Chatterjee, S., Lan, F., Reinisch, A., Corces, M. R., Xavy, S., Shen, J., Haag, D., Chanda, S., Sinha, R., Morganti, R. M., Nishimura, T., Ameen, M., Wu, H., Wernig, M., Wu, J. C., Majeti, R. 2017; 20 (3): 329-344 e7

  Abstract

  Understanding the relative contributions of genetic and epigenetic abnormalities to acute myeloid leukemia (AML) should assist integrated design of targeted therapies. In this study, we generated induced pluripotent stem cells (iPSCs) from AML patient samples harboring MLL rearrangements and found that they retained leukemic mutations but reset leukemic DNA methylation/gene expression patterns. AML-iPSCs lacked leukemic potential, but when differentiated into hematopoietic cells, they reacquired the ability to give rise to leukemia in vivo and reestablished leukemic DNA methylation/gene expression patterns, including an aberrant MLL signature. Epigenetic reprogramming was therefore not sufficient to eliminate leukemic behavior. This approach also allowed us to study the properties of distinct AML subclones, including differential drug susceptibilities of KRAS mutant and wild-type cells, and predict relapse based on increased cytarabine resistance of a KRAS wild-type subclone. Overall, our findings illustrate the value of AML-iPSCs for investigating the mechanistic basis and clonal properties of human AML.

  View details for DOI 10.1016/j.stem.2016.11.018

  View details for PubMedID 28089908

• Deep Sequencing of Urinary RNAs for Bladder Cancer Molecular Diagnostics. Clinical cancer research : an official journal of the American Association for Cancer Research Sin, M. L., Mach, K. E., Sinha, R., Wu, F., Trivedi, D., Altobelli, E., Jensen, K. C., Sahoo, D., Lu, Y., Liao, J. C. 2017

  Abstract

  The majority of bladder cancer patients present with localized disease and are managed by transurethral resection. However, the high rate of recurrence necessitates lifetime cystoscopic surveillance. Developing a sensitive and specific urine-based test would significantly improve bladder cancer screening, detection, and surveillance.RNA-seq was used for biomarker discovery to directly assess the gene expression profile of exfoliated urothelial cells in urine derived from bladder cancer patients (n=13) and controls (n=10). Eight bladder cancer specific and 3 reference genes identified by RNA-seq were quantitated by qPCR in a training cohort of 102 urine samples. A diagnostic model based on the training cohort was constructed using multiple logistic regression. The model was further validated in an independent cohort of 101 urines.418 genes were found to be differentially expressed between bladder cancer and controls. Validation of a subset of these genes was used to construct an equation for computing a probability of bladder cancer score (PBC) based on expression of 3-markers (ROBO1, WNT5A, and CDC42BPB). Setting PBC=0.45 as the cutoff for a positive test, urine testing using the 3-marker panel had overall 88% sensitivity and 92% specificity in the training cohort. The accuracy of the 3-marker panel in the independent validation cohort yielded an area under the curve of 0.87 and overall 83% sensitivity and 89% specificity.Urine-based molecular diagnostics using this 3-marker signature could provide a valuable adjunct to cystoscopy and may lead to a reduction of unnecessary procedures for bladder cancer diagnosis.

  View details for DOI 10.1158/1078-0432.CCR-16-2610

  View details for PubMedID 28193625

• Pharmacological rescue of diabetic skeletal stem cell niches. Science translational medicine Tevlin, R., Seo, E. Y., Marecic, O., McArdle, A., Tong, X., Zimdahl, B., Malkovskiy, A., Sinha, R., Gulati, G., Li, X., Wearda, T., Morganti, R., Lopez, M., Ransom, R. C., Duldulao, C. R., Rodrigues, M., Nguyen, A., Januszyk, M., Maan, Z., Paik, K., Yapa, K., Rajadas, J., Wan, D. C., Gurtner, G. C., Snyder, M., Beachy, P. A., Yang, F., Goodman, S. B., Weissman, I. L., Chan, C. K., Longaker, M. T. 2017; 9 (372)

  Abstract

  Diabetes mellitus (DM) is a metabolic disease frequently associated with impaired bone healing. Despite its increasing prevalence worldwide, the molecular etiology of DM-linked skeletal complications remains poorly defined. Using advanced stem cell characterization techniques, we analyzed intrinsic and extrinsic determinants of mouse skeletal stem cell (mSSC) function to identify specific mSSC niche-related abnormalities that could impair skeletal repair in diabetic (Db) mice. We discovered that high serum concentrations of tumor necrosis factor-α directly repressed the expression of Indian hedgehog (Ihh) in mSSCs and in their downstream skeletogenic progenitors in Db mice. When hedgehog signaling was inhibited during fracture repair, injury-induced mSSC expansion was suppressed, resulting in impaired healing. We reversed this deficiency by precise delivery of purified Ihh to the fracture site via a specially formulated, slow-release hydrogel. In the presence of exogenous Ihh, the injury-induced expansion and osteogenic potential of mSSCs were restored, culminating in the rescue of Db bone healing. Our results present a feasible strategy for precise treatment of molecular aberrations in stem and progenitor cell populations to correct skeletal manifestations of systemic disease.

  View details for DOI 10.1126/scitranslmed.aag2809

  View details for PubMedID 28077677

• Mapping the Pairwise Choices Leading from Pluripotency to Human Bone, Heart, and Other Mesoderm Cell Types CELL Loh, K. M., Chen, A., Koh, P. W., Deng, T. Z., Sinha, R., Tsai, J. M., Barkal, A. A., Shen, K. Y., Jain, R., Morganti, R. M., Shyh-Chang, N., Fernhoff, N. B., George, B. M., Wernig, G., Salomon, R. E., Chen, Z., Vogel, H., Epstein, J. A., Kundaje, A., Talbot, W. S., Beachy, P. A., Ang, L. T., Weissman, I. L. 2016; 166 (2): 451-467

  Abstract

  Stem-cell differentiation to desired lineages requires navigating alternating developmental paths that often lead to unwanted cell types. Hence, comprehensive developmental roadmaps are crucial to channel stem-cell differentiation toward desired fates. To this end, here, we map bifurcating lineage choices leading from pluripotency to 12 human mesodermal lineages, including bone, muscle, and heart. We defined the extrinsic signals controlling each binary lineage decision, enabling us to logically block differentiation toward unwanted fates and rapidly steer pluripotent stem cells toward 80%-99% pure human mesodermal lineages at most branchpoints. This strategy enabled the generation of human bone and heart progenitors that could engraft in respective in vivo models. Mapping stepwise chromatin and single-cell gene expression changes in mesoderm development uncovered somite segmentation, a previously unobservable human embryonic event transiently marked by HOPX expression. Collectively, this roadmap enables navigation of mesodermal development to produce transplantable human tissue progenitors and uncover developmental processes. VIDEO ABSTRACT.

  View details for DOI 10.1016/j.cell.2016.06.011

  View details for Web of Science ID 000380255400021

  View details for PubMedID 27419872

• Developmental cell death programs license cytotoxic cells to eliminate histocompatible partners PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Corey, D. M., rosental, B., Kowarsky, M., Sinha, R., Ishizuka, K. J., Palmeri, K. J., Quake, S. R., Voskoboynik, A., Weissman, I. L. 2016; 113 (23): 6520-6525

  Abstract

  In a primitive chordate model of natural chimerism, one chimeric partner is often eliminated in a process of allogeneic resorption. Here, we identify the cellular framework underlying loss of tolerance to one partner within a natural Botryllus schlosseri chimera. We show that the principal cell type mediating chimeric partner elimination is a cytotoxic morula cell (MC). Proinflammatory, developmental cell death programs render MCs cytotoxic and, in collaboration with activated phagocytes, eliminate chimeric partners during the "takeover" phase of blastogenic development. Among these genes, the proinflammatory cytokine IL-17 enhances cytotoxicity in allorecognition assays. Cellular transfer of FACS-purified MCs from allogeneic donors into recipients shows that the resorption response can be adoptively acquired. Transfer of 1 × 10(5) allogeneic MCs eliminated 33 of 78 (42%) recipient primary buds and 20 of 76 (20.5%) adult parental adult organisms (zooids) by 14 d whereas transfer of allogeneic cell populations lacking MCs had only minimal effects on recipient colonies. Furthermore, reactivity of transferred cells coincided with the onset of developmental-regulated cell death programs and disproportionately affected developing tissues within a chimera. Among chimeric partner "losers," severe developmental defects were observed in asexually propagating tissues, reflecting a pathologic switch in gene expression in developmental programs. These studies provide evidence that elimination of one partner in a chimera is an immune cell-based rejection that operates within histocompatible pairs and that maximal allogeneic responses involve the coordination of both phagocytic programs and the "arming" of cytotoxic cells.

  View details for DOI 10.1073/pnas.1606276113

  View details for Web of Science ID 000377155400052

  View details for PubMedID 27217570

• Hoxb5 marks long-term haematopoietic stem cells and reveals a homogenous perivascular niche NATURE Chen, J. Y., Miyanishi, M., Wang, S. K., Yamazaki, S., Sinha, R., Kao, K. S., Seita, J., Sahoo, D., Nakauchi, H., Weissman, I. L. 2016; 530 (7589): 223-?

  Abstract

  Haematopoietic stem cells (HSCs) are arguably the most extensively characterized tissue stem cells. Since the identification of HSCs by prospective isolation, complex multi-parameter flow cytometric isolation of phenotypic subsets has facilitated studies on many aspects of HSC biology, including self-renewal, differentiation, ageing, niche, and diversity. Here we demonstrate by unbiased multi-step screening, identification of a single gene, homeobox B5 (Hoxb5, also known as Hox-2.1), with expression in the bone marrow that is limited to long-term (LT)-HSCs in mice. Using a mouse single-colour tri-mCherry reporter driven by endogenous Hoxb5 regulation, we show that only the Hoxb5(+) HSCs exhibit long-term reconstitution capacity after transplantation in primary transplant recipients and, notably, in secondary recipients. Only 7-35% of various previously defined immunophenotypic HSCs are LT-HSCs. Finally, by in situ imaging of mouse bone marrow, we show that >94% of LT-HSCs (Hoxb5(+)) are directly attached to VE-cadherin(+) cells, implicating the perivascular space as a near-homogenous location of LT-HSCs.

  View details for DOI 10.1038/nature16943

  View details for Web of Science ID 000369916700040

  View details for PubMedID 26863982

  View details for PubMedCentralID PMC4854608

• Tuning Cytokine Receptor Signaling by Re-orienting Dimer Geometry with Surrogate Ligands CELL Moraga, I., Wernig, G., Wilmes, S., Gryshkova, V., Richter, C. P., Hong, W., Sinha, R., Guo, F., Fabionar, H., Wehrman, T. S., Krutzik, P., Demharter, S., Plo, I., Weissman, I. L., Minary, P., Majeti, R., Constantinescu, S. N., Piehler, J., Garcia, K. C. 2015; 160 (6): 1196-1208

  Abstract

  Most cell-surface receptors for cytokines and growth factors signal as dimers, but it is unclear whether remodeling receptor dimer topology is a viable strategy to "tune" signaling output. We utilized diabodies (DA) as surrogate ligands in a prototypical dimeric receptor-ligand system, the cytokine Erythropoietin (EPO) and its receptor (EpoR), to dimerize EpoR ectodomains in non-native architectures. Diabody-induced signaling amplitudes varied from full to minimal agonism, and structures of these DA/EpoR complexes differed in EpoR dimer orientation and proximity. Diabodies also elicited biased or differential activation of signaling pathways and gene expression profiles compared to EPO. Non-signaling diabodies inhibited proliferation of erythroid precursors from patients with a myeloproliferative neoplasm due to a constitutively active JAK2V617F mutation. Thus, intracellular oncogenic mutations causing ligand-independent receptor activation can be counteracted by extracellular ligands that re-orient receptors into inactive dimer topologies. This approach has broad applications for tuning signaling output for many dimeric receptor systems.

  View details for DOI 10.1016/j.cell.2015.02.011

  View details for Web of Science ID 000351951800018

  View details for PubMedID 25728669

• Identification and specification of the mouse skeletal stem cell. Cell Chan, C. K., Seo, E. Y., Chen, J. Y., Lo, D., McArdle, A., Sinha, R., Tevlin, R., Seita, J., Vincent-Tompkins, J., Wearda, T., Lu, W., Senarath-Yapa, K., Chung, M. T., Marecic, O., Tran, M., Yan, K. S., Upton, R., Walmsley, G. G., Lee, A. S., Sahoo, D., Kuo, C. J., Weissman, I. L., Longaker, M. T. 2015; 160 (1-2): 285-298

  Abstract

  How are skeletal tissues derived from skeletal stem cells? Here, we map bone, cartilage, and stromal development from a population of highly pure, postnatal skeletal stem cells (mouse skeletal stem cells, mSSCs) to their downstream progenitors of bone, cartilage, and stromal tissue. We then investigated the transcriptome of the stem/progenitor cells for unique gene-expression patterns that would indicate potential regulators of mSSC lineage commitment. We demonstrate that mSSC niche factors can be potent inducers of osteogenesis, and several specific combinations of recombinant mSSC niche factors can activate mSSC genetic programs in situ, even in nonskeletal tissues, resulting in de novo formation of cartilage or bone and bone marrow stroma. Inducing mSSC formation with soluble factors and subsequently regulating the mSSC niche to specify its differentiation toward bone, cartilage, or stromal cells could represent a paradigm shift in the therapeutic regeneration of skeletal tissues.

  View details for DOI 10.1016/j.cell.2014.12.002

  View details for PubMedID 25594184

  View details for PubMedCentralID PMC4297645

• Identification of a colonial chordate histocompatibility gene. Science Voskoboynik, A., Newman, A. M., Corey, D. M., Sahoo, D., Pushkarev, D., Neff, N. F., Passarelli, B., Koh, W., Ishizuka, K. J., Palmeri, K. J., Dimov, I. K., Keasar, C., Fan, H. C., Mantalas, G. L., Sinha, R., Penland, L., Quake, S. R., Weissman, I. L. 2013; 341 (6144): 384-387

  Abstract

  Histocompatibility is the basis by which multicellular organisms of the same species distinguish self from nonself. Relatively little is known about the mechanisms underlying histocompatibility reactions in lower organisms. Botryllus schlosseri is a colonial urochordate, a sister group of vertebrates, that exhibits a genetically determined natural transplantation reaction, whereby self-recognition between colonies leads to formation of parabionts with a common vasculature, whereas rejection occurs between incompatible colonies. Using genetically defined lines, whole-transcriptome sequencing, and genomics, we identified a single gene that encodes self-nonself and determines "graft" outcomes in this organism. This gene is significantly up-regulated in colonies poised to undergo fusion and/or rejection, is highly expressed in the vasculature, and is functionally linked to histocompatibility outcomes. These findings establish a platform for advancing the science of allorecognition.

  View details for DOI 10.1126/science.1238036

  View details for PubMedID 23888037

• Isolated pseudo-RNA-recognition motifs of SR proteins can regulate splicing using a noncanonical mode of RNA recognition PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Clery, A., Sinha, R., Anczukow, O., Corrionero, A., Moursy, A., Daubner, G. M., Valcarcel, J., Krainer, A. R., Allain, F. H. 2013; 110 (30): E2802-E2811

  Abstract

  Serine/arginine (SR) proteins, one of the major families of alternative-splicing regulators in Eukarya, have two types of RNA-recognition motifs (RRMs): a canonical RRM and a pseudo-RRM. Although pseudo-RRMs are crucial for activity of SR proteins, their mode of action was unknown. By solving the structure of the human SRSF1 pseudo-RRM bound to RNA, we discovered a very unusual and sequence-specific RNA-binding mode that is centered on one α-helix and does not involve the β-sheet surface, which typically mediates RNA binding by RRMs. Remarkably, this mode of binding is conserved in all pseudo-RRMs tested. Furthermore, the isolated pseudo-RRM is sufficient to regulate splicing of about half of the SRSF1 target genes tested, and the bound α-helix is a pivotal element for this function. Our results strongly suggest that SR proteins with a pseudo-RRM frequently regulate splicing by competing with, rather than recruiting, spliceosome components, using solely this unusual RRM.

  View details for DOI 10.1073/pnas.1303445110

  View details for Web of Science ID 000322112300010

  View details for PubMedID 23836656

• Molecular phylogeny of OVOL genes illustrates a conserved C2H2 zinc finger domain coupled by hypervariable unstructured regions. PloS one Kumar, A., Bhandari, A., Sinha, R., Sardar, P., Sushma, M., Goyal, P., Goswami, C., Grapputo, A. 2012; 7 (6)

  Abstract

  OVO-like proteins (OVOL) are members of the zinc finger protein family and serve as transcription factors to regulate gene expression in various differentiation processes. Recent studies have shown that OVOL genes are involved in epithelial development and differentiation in a wide variety of organisms; yet there is a lack of comprehensive studies that describe OVOL proteins from an evolutionary perspective. Using comparative genomic analysis, we traced three different OVOL genes (OVOL1-3) in vertebrates. One gene, OVOL3, was duplicated during a whole-genome-duplication event in fish, but only the copy (OVOL3b) was retained. From early-branching metazoa to humans, we found that a core domain, comprising a tetrad of C2H2 zinc fingers, is conserved. By domain comparison of the OVOL proteins, we found that they evolved in different metazoan lineages by attaching intrinsically-disordered (ID) segments of N/C-terminal extensions of 100 to 1000 amino acids to this conserved core. These ID regions originated independently across different animal lineages giving rise to different types of OVOL genes over the course of metazoan evolution. We illustrated the molecular evolution of metazoan OVOL genes over a period of 700 million years (MY). This study both extends our current understanding of the structure/function relationship of metazoan OVOL genes, and assembles a good platform for further characterization of OVOL genes from diverged organisms.

  View details for DOI 10.1371/journal.pone.0039399

  View details for PubMedID 22737237

• Spliceosomal Intron Insertions in Genome Compacted Ray-Finned Fishes as Evident from Phylogeny of MC Receptors, Also Supported by a Few Other GPCRs PLOS ONE Kumar, A., Bhandari, A., Sinha, R., Goyal, P., Grapputo, A. 2011; 6 (8)

  Abstract

  Insertions of spliceosomal introns are very rare events during evolution of vertebrates and the mechanisms governing creation of novel intron(s) remain obscure. Largely, gene structures of melanocortin (MC) receptors are characterized by intron-less architecture. However, recently a few exceptions have been reported in some fishes. This warrants a systematic survey of MC receptors for understanding intron insertion events during vertebrate evolution.We have compiled an extended list of MC receptors from different vertebrate genomes with variations in fishes. Notably, the closely linked MC2Rs and MC5Rs from a group of ray-finned fishes have three and one intron insertion(s), respectively, with conserved positions and intron phase. In both genes, one novel insertion was in the highly conserved DRY motif at the end of helix TM3. Further, the proto-splice site MAG↑R is maintained at intron insertion sites in these two genes. However, the orthologs of these receptors from zebrafish and tetrapods are intron-less, suggesting these introns are simultaneously created in selected fishes. Surprisingly, these novel introns are traceable only in four fish genomes. We found that these fish genomes are severely compacted after the separation from zebrafish. Furthermore, we also report novel intron insertions in P2Y receptors and in CHRM3. Finally, we report ultrasmall introns in MC2R genes from selected fishes.The current repository of MC receptors illustrates that fishes have no MC3R ortholog. MC2R, MC5R, P2Y receptors and CHRM3 have novel intron insertions only in ray-finned fishes that underwent genome compaction. These receptors share one intron at an identical position suggestive of being inserted contemporaneously. In addition to repetitive elements, genome compaction is now believed to be a new hallmark that promotes intron insertions, as it requires rapid DNA breakage and subsequent repair processes to gain back normal functionality.

  View details for DOI 10.1371/journal.pone.0022046

  View details for Web of Science ID 000293563300003

  View details for PubMedID 21850219

• Interaction between the RNA binding domains of Ser-Arg splicing factor 1 and U1-70K snRNP protein determines early spliceosome assembly PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Cho, S., Hoang, A., Sinha, R., Zhong, X., Fu, X., Krainer, A. R., Ghosh, G. 2011; 108 (20): 8233-8238

  Abstract

  It has been widely accepted that the early spliceosome assembly begins with U1 small nuclear ribonucleoprotein (U1 snRNP) binding to the 5' splice site (5'SS), which is assisted by the Ser/Arg (SR)-rich proteins in mammalian cells. In this process, the RS domain of SR proteins is thought to directly interact with the RS motif of U1-70K, which is subject to regulation by RS domain phosphorylation. Here we report that the early spliceosome assembly event is mediated by the RNA recognition domains (RRM) of serine/arginine-rich splicing factor 1 (SRSF1), which bridges the RRM of U1-70K to pre-mRNA by using the surface opposite to the RNA binding site. Specific mutation in the RRM of SRSF1 that disrupted the RRM-RRM interaction also inhibits the formation of spliceosomal E complex and splicing. We further demonstrate that the hypo-phosphorylated RS domain of SRSF1 interacts with its own RRM, thus competing with U1-70K binding, whereas the hyper-phosphorylated RS domain permits the formation of a ternary complex containing ESE, an SR protein, and U1 snRNP. Therefore, phosphorylation of the RS domain in SRSF1 appears to induce a key molecular switch from intra- to intermolecular interactions, suggesting a plausible mechanism for the documented requirement for the phosphorylation/dephosphorylation cycle during pre-mRNA splicing.

  View details for DOI 10.1073/pnas.1017700108

  View details for Web of Science ID 000290719600036

  View details for PubMedID 21536904

• Arginine Methylation Controls the Subcellular Localization and Functions of the Oncoprotein Splicing Factor SF2/ASF MOLECULAR AND CELLULAR BIOLOGY Sinha, R., Allemand, E., Zhang, Z., Karni, R., Myers, M. P., Krainer, A. R. 2010; 30 (11): 2762-2774

  Abstract

  Alternative splicing and posttranslational modifications (PTMs) are major sources of protein diversity in eukaryotic proteomes. The SR protein SF2/ASF is an oncoprotein that functions in pre-mRNA splicing, with additional roles in other posttranscriptional and translational events. Functional studies of SR protein PTMs have focused exclusively on the reversible phosphorylation of Ser residues in the C-terminal RS domain. We confirmed that human SF2/ASF is methylated at residues R93, R97, and R109, which were identified in a global proteomic analysis of Arg methylation, and further investigated whether these methylated residues regulate the properties of SF2/ASF. We show that the three arginines additively control the subcellular localization of SF2/ASF and that both the positive charge and the methylation state are important. Mutations that block methylation and remove the positive charge result in the cytoplasmic accumulation of SF2/ASF. The consequent decrease in nuclear SF2/ASF levels prevents it from modulating the alternative splicing of target genes, results in higher translation stimulation, and abrogates the enhancement of nonsense-mediated mRNA decay. This study addresses the mechanisms by which Arg methylation and the associated positive charge regulate the activities of SF2/ASF and emphasizes the significance of localization control for an oncoprotein with multiple functions in different cellular compartments.

  View details for DOI 10.1128/MCB.01270-09

  View details for Web of Science ID 000277558300015

  View details for PubMedID 20308322

• SF2/ASF autoregulation involves multiple layers of post-transcriptional and translational control NATURE STRUCTURAL & MOLECULAR BIOLOGY Sun, S., Zhang, Z., Sinha, R., Karni, R., Krainer, A. R. 2010; 17 (3): 306-U70

  Abstract

  SF2/ASF is a prototypical serine- and arginine-rich protein, with important roles in splicing and other aspects of mRNA metabolism. Splicing factor, arginine/serine-rich 1 (SFRS1), the gene encoding SF2/ASF, is a potent proto-oncogene with abnormal expression in many tumors. We found that SF2/ASF negatively autoregulates its expression to maintain homeostatic levels. We characterized six alternatively spliced SF2/ASF mRNA isoforms: the major isoform encodes full-length protein, whereas the others are either retained in the nucleus or degraded by nonsense-mediated mRNA decay. Unproductive splicing accounts for only part of the autoregulation, which occurs primarily at the translational level. The effect is specific to SF2/ASF and requires RNA recognition motif 2 (RRM2). The ultraconserved 3' untranslated region (UTR) is necessary and sufficient for downregulation. SF2/ASF overexpression shifts the distribution of target mRNA toward monoribosomes, and translational repression is partly independent of Dicer and a 5' cap. Thus, multiple post-transcriptional and translational mechanisms are involved in fine-tuning the expression of SF2/ASF.

  View details for DOI 10.1038/nsmb.1750

  View details for Web of Science ID 000275182700010

  View details for PubMedID 20139984

• The gene encoding the splicing factor SF2/ASF is a proto-oncogene NATURE STRUCTURAL & MOLECULAR BIOLOGY Karni, R., de Stanchina, E., Lowe, S. W., Sinha, R., Mu, D., Krainer, A. R. 2007; 14 (3): 185-193

  Abstract

  Alternative splicing modulates the expression of many oncogene and tumor-suppressor isoforms. We have tested whether some alternative splicing factors are involved in cancer. We found that the splicing factor SF2/ASF is upregulated in various human tumors, in part due to amplification of its gene, SFRS1. Moreover, slight overexpression of SF2/ASF is sufficient to transform immortal rodent fibroblasts, which form sarcomas in nude mice. We further show that SF2/ASF controls alternative splicing of the tumor suppressor BIN1 and the kinases MNK2 and S6K1. The resulting BIN1 isoforms lack tumor-suppressor activity; an isoform of MNK2 promotes MAP kinase-independent eIF4E phosphorylation; and an unusual oncogenic isoform of S6K1 recapitulates the transforming activity of SF2/ASF. Knockdown of either SF2/ASF or isoform-2 of S6K1 is sufficient to reverse transformation caused by the overexpression of SF2/ASF in vitro and in vivo. Thus, SF2/ASF can act as an oncoprotein and is a potential target for cancer therapy.

  View details for DOI 10.1038/nmb1209

  View details for Web of Science ID 000244715200006

  View details for PubMedID 17310252