The Endosomal Sorting Complex, ESCRT, has diverse roles in blood progenitor maintenance, lineage choice and immune response.

Most hematological malignancies are associated with reduced expression of one or more components of the Endosomal Sorting Complex Required for Transport (ESCRT). However, the roles of ESCRT in stem cell and progenitor maintenance are not resolved. Parsing signaling pathways in relation to the canonical role of ESCRT poses a challenge. The Drosophila hematopoietic organ, the larval lymph gland, provides a path to dissect the roles of cellular trafficking pathways such as ESCRT in blood development and maintenance. Drosophila has 13 core ESCRT components. Knockdown of individual ESCRTs showed that only Vps28 and Vp36 were required in all lymph gland progenitors. Using the well-conserved ESCRT-II complex as an example of the range of phenotypes seen upon ESCRT depletion, we show that ESCRTs have cell autonomous as well as non-autonomous roles in progenitor maintenance and differentiation. ESCRT depletion also sensitized posterior lobe progenitors to respond to immunogenic wasp infestation. We also identify key heterotypic roles for ESCRT in position-dependent control of Notch activation to suppress crystal cell differentiation. Our study shows that the cargo sorting machinery determines the identity of progenitors and their adaptability to the dynamic microenvironment. These mechanisms for control of cell fate may tailor developmental diversity in multiple contexts.

ISSCR standards for the use of human stem cells in basic research.

The laboratory culture of human stem cells seeks to capture a cellular state as an in vitro surrogate of a biological system. For the results and outputs from this research to be accurate, meaningful, and durable, standards that ensure reproducibility and reliability of the data should be applied. Although such standards have been previously proposed for repositories and distribution centers, no widely accepted best practices exist for laboratory research with human pluripotent and tissue stem cells. To fill that void, the International Society for Stem Cell Research has developed a set of recommendations, including reporting criteria, for scientists in basic research laboratories. These criteria are designed to be technically and financially feasible and, when implemented, enhance the reproducibility and rigor of stem cell research.

Generation of an OCIAD2 overexpressing transgenic human embryonic stem cell line, BJNhem20-OCIAD2-OV.

Overexpression of Ovarian Carcinoma Immunoreactive Antigen Domain containing protein 2 (OCIAD2) was carried out in BJNhem20 human Embryonic Stem Cell line (hESC). A stable line was generated through nucleofection of the plasmid construct pCAG-OCIAD2.

Generation of OCIAD2 homozygous knockout (BJNhem20-OCIAD2-CRISPR-33) and heterozygous knockout (BJNhem20-OCIAD2-CRISPR-40) human embryonic stem cell lines using CRISPR-Cas9 mediated targeting.

Ovarian Carcinoma Immunoreactive Antigen domain containing 2 (OCIAD2) was knocked out by targeting its exon 4 through CRISPR-Cas9 paired nickase strategy to generate two OCIAD2 knockout human embryonic stem cell lines- one homozygous (BJNhem20-OCIAD2-CRISPR-33) and one heterozygous (BJNhem20-OCIAD2-CRISPR-40) for mutant ociad2. Both lines maintain pluripotency, normal karyotype, and trilineage differentiation potential.

Organelle dysfunction upon asrij depletion causes aging-like changes in mouse hematopoietic stem cells.

Aging of the blood system is characterized by increased hematopoietic stem cells (HSCs) and myeloid-biased differentiation leading to higher propensity for hematological malignancies. Unraveling cell-intrinsic mechanisms regulating HSC aging could aid reversal or slowing of aging. Asrij/OCIAD1 is an evolutionarily conserved regulator of hematopoiesis and governs mitochondrial, endosomal, and proteasomal function in mammalian stem cells. Asrij deletion in mice causes loss of HSC quiescence, myeloid skewing, reduced p53 and increased DNA damage, features attributed to aged HSCs. Mechanistically, Asrij controls p53 ubiquitination and degradation and AKT/STAT5 activation. Asrij localizes to endosomes and mitochondria. As decline in organelle structure and function are common hallmarks of aging, we asked whether Asrij regulates organelle function in aged HSCs. We find that chronologically aged wild-type (WT) HSCs had reduced Asrij levels. Expectedly, young asrij KO mice had reduced AcH4K16 levels; however, transcriptome analysis of KO HSCs showed a modest overlap of gene expression with aged WT HSCs. Further, analysis of organelle structure and function in asrij KO mice revealed significant changes, namely damaged mitochondria, elevated ROS; impaired endosomal trafficking seen by increased cleaved Notch1, reduced Rab5; and reduced 26S proteasome activity. Pharmacological correction of mitochondrial and proteasome activity in asrij KO mice restored HSC and myeloid cell frequencies. Furthermore, lysophosphatidic acid-induced Asrij upregulation in aged WT mice rescued mitochondrial and proteasome activity and restored HSC frequency. Our results highlight a new role for Asrij in preventing HSC aging by regulating organelle homeostasis and will help decipher organelle dynamics in HSC longevity.

Intact in situ Preparation of the Drosophila melanogaster Lymph Gland for a Comprehensive Analysis of Larval Hematopoiesis.

Blood cells have a limited lifespan and are replenished by a small number of hematopoietic stem and progenitor cells (HSPCs). Adult vertebrate hematopoiesis occurs in the bone marrow, liver, and spleen, rendering a comprehensive analysis of the entire HSPC pool nearly impossible. The Drosophila blood system is well studied and has developmental, molecular, and functional parallels with that of vertebrates. Unlike vertebrates, post-embryonic hematopoiesis in Drosophila is essentially restricted to the larval lymph gland (LG), a multi-lobed organ that flanks the dorsal vessel. Because the anterior-most or primary lobes of the LG are easy to dissect out, their cellular and molecular characteristics have been studied in considerable detail. The 2-3 pairs of posterior lobes are more delicate and fragile and have largely been ignored. However, posterior lobes harbor a significant blood progenitor pool, and several hematopoietic mutants show differences in phenotype between the anterior and posterior lobes. Hence, a comprehensive analysis of the LG is important for a thorough understanding of Drosophila hematopoiesis. Most studies focus on isolating the primary lobes by methods that generally dislodge and damage other lobes. To obtain preparations of the whole LG, including intact posterior lobes, here we provide a detailed protocol for larval fillet dissection. This allows accessing and analyzing complete LG lobes, along with dorsal vessel and pericardial cells. We demonstrate that tissue architecture and integrity is maintained and provide methods for quantitative analysis. This protocol can be used to quickly and effectively isolate complete LGs from first instar larval to pupal stages and can be implemented with ease.

A Conserved Role for Asrij/OCIAD1 in Progenitor Differentiation and Lineage Specification Through Functional Interaction With the Regulators of Mitochondrial Dynamics.

Mitochondria are highly dynamic organelles whose activity is an important determinant of blood stem and progenitor cell state. Mitochondrial morphology is maintained by continuous fission and fusion and affects stem cell proliferation, differentiation, and aging. However, the mechanism by which mitochondrial morphology and dynamics regulate cell differentiation and lineage choice remains incompletely understood. Asrij/OCIAD1 is a conserved protein that governs mitochondrial morphology, energy metabolism and human embryonic stem cell (hESC) differentiation. To investigate the in vivo relevance of these properties, we compared hESC phenotypes with those of Drosophila hematopoiesis, where Asrij is shown to regulate blood progenitor maintenance by conserved mechanisms. In concordance with hESC studies, we found that Drosophila Asrij also localizes to mitochondria of larval blood cells and its depletion from progenitors results in elongated mitochondria. Live imaging of asrij knockdown hemocytes and of OCIAD1 knockout hESCs showed reduced mitochondrial dynamics. Since key regulators of mitochondrial dynamics actively regulate mitochondrial morphology, we hypothesized that mitochondrial fission and fusion may control progenitor maintenance or differentiation in an Asrij-dependent manner. Knockdown of the fission regulator Drp1 in Drosophila lymph gland progenitors specifically suppressed crystal cell differentiation whereas depletion of the fusion regulator Marf (Drosophila Mitofusin) increased the same with concomitant upregulation of Notch signaling. These phenotypes were stronger in anterior progenitors and were exacerbated by Asrij depletion. Asrij is known to suppress Notch signaling and crystal cell differentiation. Our analysis reveals that synergistic interactions of Asrij with Drp1 and Marf have distinct impacts on lymph gland progenitor mitochondrial dynamics and crystal cell differentiation. Taken together, using invertebrate and mammalian model systems we demonstrate a conserved role for Asrij/OCIAD1 in linking mitochondrial dynamics and progenitor differentiation. Our study sets the stage for deciphering how regulators of mitochondrial dynamics may contribute to functional heterogeneity and lineage choice in vertebrate blood progenitors.

Inclusivity and diversity: Integrating international perspectives on stem cell challenges and potential.

Regenerative medicine has great potential. The pace of scientific advance is exciting and the medical opportunities for regeneration and repair may be transformative. However, concerns continue to grow, relating to problems caused both by unscrupulous private clinics offering unregulated therapies based on little or no evidence and by premature regulatory approval on the basis of insufficient scientific rationale and clinical evidence. An initiative by the InterAcademy Partnership convened experts worldwide to identify opportunities and challenges, with a focus on stem cells. This was designed to be inclusive and consensus outputs reflected the diversity of the global research population. Among issues addressed for supporting research and innovation while protecting patients were ethical assessment; pre-clinical and clinical research; regulatory authorization and medicines access; and engagement with patients, policy makers, and the public. The InterAcademy Partnership (IAP) identified options for action for sharing good practice and building collaboration within the scientific community and with other stakeholders worldwide.

Differential activation of JAK-STAT signaling reveals functional compartmentalization in Drosophila blood progenitors.

Blood cells arise from diverse pools of stem and progenitor cells. Understanding progenitor heterogeneity is a major challenge. The Drosophila larval lymph gland is a well-studied model to understand blood progenitor maintenance and recapitulates several aspects of vertebrate hematopoiesis. However in-depth analysis has focused on the anterior lobe progenitors (AP), ignoring the posterior progenitors (PP) from the posterior lobes. Using in situ expression mapping and developmental and transcriptome analysis, we reveal PP heterogeneity and identify molecular-genetic tools to study this abundant progenitor population. Functional analysis shows that PP resist differentiation upon immune challenge, in a JAK-STAT-dependent manner. Upon wasp parasitism, AP downregulate JAK-STAT signaling and form lamellocytes. In contrast, we show that PP activate STAT92E and remain undifferentiated, promoting survival. Stat92E knockdown or genetically reducing JAK-STAT signaling permits PP lamellocyte differentiation. We discuss how heterogeneity and compartmentalization allow functional segregation in response to systemic cues and could be widely applicable.

Expression, Purification and Crystallization of Asrij, A Novel Scaffold Transmembrane Protein.

Asrij/OCIAD1 is a scaffold transmembrane protein belonging to the Ovarian Carcinoma Immunoreactive Antigen Domain containing protein family. In Drosophila and mouse models, Asrij localizes at the endosomal and mitochondrial membrane and is shown to regulate the stemness of hematopoietic stem cells. Interaction of Asrij with ADP Ribosylation Factor 1 (Arf1) is shown to be crucial for hematopoietic niche function and prohemocyte maintenance. Here, we report the heterologous expression, standardization of detergents and purification methodologies for crystallization of Asrij/OCIAD1. To probe the activity of bacterially expressed Asrij, we developed a protein complementation assay and conclusively show that Asrij and Arf1 physically interact. Further, we find that sophorolipids improve the solubility and monodispersibility of Asrij. Hence, we propose that sophorolipids could be novel additives for stabilization of membrane proteins. To our knowledge, this is the first study detailing methodology for the production and crystallization of a heterologously expressed scaffold membrane protein and will be widely applicable to understand membrane protein structure and function.

The OCIAD protein family: comparative developmental biology and stem cell application.

Over the last two decades, an exponential growth in technologies and techniques available to biologists has provided mind-boggling quantities of data and led to information overload. Yet, answers to fundamental questions such as "how are we made?" and "what keeps us ticking?" remain incomplete. Developmental biology has provided elegant approaches to address such questions leading to enlightening insights. While several important contributions to developmental biology have come from India over the decades, this area of research remains nascent. Here, we review the journey in India, from the discovery of the ociad gene family to decoding its role in development and stem cells. We compare analysis in silico, in vivo and ex vivo, with developmental models such as Drosophila, mouse and stem cells that gave important insight into how these clinically significant genes function.

Asrij/OCIAD1 suppresses CSN5-mediated p53 degradation and maintains mouse hematopoietic stem cell quiescence.

Inactivation of the tumor suppressor p53 is essential for unrestrained growth of cancers. However, only 11% of hematological malignancies have mutant p53. Mechanisms that cause wild-type p53 dysfunction and promote leukemia are inadequately deciphered. The stem cell protein Asrij/OCIAD1 is misexpressed in several human hematological malignancies and implicated in the p53 pathway and DNA damage response. However, Asrij function in vertebrate hematopoiesis remains unknown. We generated the first asrij null (knockout [KO]) mice and show that they are viable and fertile with no gross abnormalities. However, by 6 months, they exhibit increased peripheral blood cell counts, splenomegaly, and an expansion of bone marrow hematopoietic stem cells (HSCs) with higher myeloid output. HSCs lacking Asrij are less quiescent and more proliferative with higher repopulation potential as observed from serial transplantation studies. However, stressing KO mice with sublethal γ irradiation or multiple injections of 5-fluorouracil results in reduced survival and rapid depletion of hematopoietic stem/progenitor cells (HSPCs) by driving them into proliferative exhaustion. Molecular and biochemical analyses revealed increased polyubiquitinated protein levels, Akt/STAT5 activation and COP9 signalosome subunit 5 (CSN5)-mediated p53 ubiquitination, and degradation in KO HSPCs. Further, we show that Asrij sequesters CSN5 via its conserved OCIA domain, thereby preventing p53 degradation. In agreement, Nutlin-3 treatment of KO mice restored p53 levels and reduced high HSPC frequencies. Thus, we provide a new mouse model resembling myeloproliferative disease and identify a posttranslational regulator of wild-type p53 essential for maintaining HSC quiescence that could be a potential target for pharmacological intervention.

Rudhira/BCAS3 couples microtubules and intermediate filaments to promote cell migration for angiogenic remodeling.

Blood vessel formation requires endothelial cell (EC) migration that depends on dynamic remodeling of the cytoskeleton. Rudhira/Breast Carcinoma Amplified Sequence 3 (BCAS3) is a cytoskeletal protein essential for EC migration and sprouting angiogenesis during mouse development and is implicated in metastatic disease. Here, we report that Rudhira mediates cytoskeleton organization and dynamics during EC migration. Rudhira binds to both microtubules (MTs) and vimentin intermediate filaments (IFs) and stabilizes MTs. Rudhira depletion impairs cytoskeletal cross-talk, MT stability, and hence focal adhesion disassembly. The BCAS3 domain of Rudhira is necessary and sufficient for MT-IF cross-linking and cell migration. Pharmacologically restoring MT stability rescues gross cytoskeleton organization and angiogenic sprouting in Rudhira-depleted cells. Our study identifies the novel and essential role of Rudhira in cytoskeletal cross-talk and assigns function to the conserved BCAS3 domain. Targeting Rudhira could allow tissue-restricted cytoskeleton modulation to control cell migration and angiogenesis in development and disease.

Proteomics of Asrij Perturbation in Drosophila Lymph Glands for Identification of New Regulators of Hematopoiesis.

Hematopoiesis is the process of differentiation of precursor blood cells into mature blood cells that is controlled by a complex set of molecular interactions. Understanding hematopoiesis is important for the study of hematological disorders. However, a comprehensive understanding of how physiological and genetic mechanisms regulate blood cell precursor maintenance and differentiation is lacking. Owing to simplicity and ease of genetic analysis, the Drosophila melanogaster lymph gland (LG) is an excellent model to study hematopoiesis. Here, we quantitatively analyzed the LG proteome under genetic conditions that either maintain precursors or promote their differentiation in vivo, by perturbing expression of Asrij, a conserved endosomal regulator of hematopoiesis. Using iTRAQ-based quantitative proteomics, we determined the relative expression levels of proteins in Asrij-knockout and overexpressing LGs from 1500 larval dissections compared with wild type. Our data showed that at least 6.5% of the Drosophila proteome is expressed in wild type LGs. Of the 2133 proteins identified, 780 and 208 proteins were common to previously reported cardiac tube and hemolymph proteomes, respectively, resulting in the identification of 1238 proteins exclusive to the LG. Perturbation of Asrij levels led to differential expression of 619 proteins, of which 27% have human homologs implicated in various diseases. Proteins regulating metabolism, immune system, signal transduction and vesicle-mediated transport were significantly enriched. Immunostaining of representative candidates from the enriched categories and previous reports confirmed 73% of our results, indicating the validity of our LG proteome. Our study provides, for the first time, an in vivo proteomics resource for identifying novel regulators of hematopoiesis that will also be applicable to understanding vertebrate blood cell development.

Synthetic Host-Guest Assembly in Cells and Tissues: Fast, Stable, and Selective Bioorthogonal Imaging via Molecular Recognition.

Bioorthogonal strategies are continuing to pave the way for new analytical tools in biology. Although a significant amount of progress has been made in developing covalent reaction based bioorthogonal strategies, balanced reactivity, and stability are often difficult to achieve from these systems. Alternatively, despite being kinetically beneficial, the development of noncovalent approaches that utilize fully synthetic and stable components remains challenging due to the lack of selectivity in conventional noncovalent interactions in the living cellular environment. Herein, we introduce a bioorthogonal assembly strategy based on a synthetic host-guest system featuring Cucurbit[7]uril (CB[7]) and adamantylamine (ADA). We demonstrate that highly selective and ultrastable host-guest interaction between CB[7] and ADA provides a noncovalent mechanism for assembling labeling agents, such as fluorophores and DNA, in cells and tissues for bioorthogonal imaging of molecular targets. Additionally, by combining with covalent reaction, we show that this CB[7]-ADA based noncovalent interaction enables simultaneous bioorthogonal labeling and multiplexed imaging in cells as well as tissue sections. Finally, we show that interaction between CB[7] and ADA fulfills the demands of specificity and stability that is required for assembling molecules in the complexities of a living cell. We demonstrate this by sensitive detection of metastatic cancer-associated cell surface protein marker as well as by showing the distribution and dynamics of F-actin in living cells.

OCIAD1 Controls Electron Transport Chain Complex I Activity to Regulate Energy Metabolism in Human Pluripotent Stem Cells.

Pluripotent stem cells (PSCs) derive energy predominantly from glycolysis and not the energy-efficient oxidative phosphorylation (OXPHOS). Differentiation is initiated with energy metabolic shift from glycolysis to OXPHOS. We investigated the role of mitochondrial energy metabolism in human PSCs using molecular, biochemical, genetic, and pharmacological approaches. We show that the carcinoma protein OCIAD1 interacts with and regulates mitochondrial complex I activity. Energy metabolic assays on live pluripotent cells showed that OCIAD1-depleted cells have increased OXPHOS and may be poised for differentiation. OCIAD1 maintains human embryonic stem cells, and its depletion by CRISPR/Cas9-mediated knockout leads to rapid and increased differentiation upon induction, whereas OCIAD1 overexpression has the opposite effect. Pharmacological alteration of complex I activity was able to rescue the defects of OCIAD1 modulation. Thus, hPSCs can exist in energy metabolic substates. OCIAD1 provides a target to screen for additional modulators of mitochondrial activity to promote transient multipotent precursor expansion or enhance differentiation.

A double helical motif in OCIAD2 is essential for its localization, interactions and STAT3 activation.

The Ovarian Carcinoma Immunoreactive Antigen domain (OCIAD) - containing proteins OCIAD1/Asrij and OCIAD2, are implicated in several cancers and neurodegenerative diseases. While Asrij has a conserved role in facilitating STAT3 activation for JAK/STAT signaling, the expression and function of OCIAD2 in non-cancerous contexts remains unknown. Here, we report that ociad2 neighbors ociad1/asrij in most vertebrate genomes, and the two genes likely arose by tandem gene duplication, probably somewhere between the Ordovician and Silurian eras. We show that ociad2 expression is higher in the mouse kidney, liver and brain relative to other tissues. OCIAD2 localizes to early endosomes and mitochondria, and interacts with Asrij and STAT3. Knockdown and overexpression studies showed that OCIAD2 is essential for STAT3 activation and cell migration, which could contribute to its role in tumor metastasis. Structure prediction programs, protein disruption studies, biochemical and functional assays revealed a double helical motif in the OCIA domain that is necessary and sufficient for its localization, interactions and STAT3 activation. Given the importance of JAK/STAT signaling in development and disease, our studies shed light on the evolution and conserved function of the OCIA domain in regulating this pathway and will be critical for understanding this clinically important protein family.

Rudhira/BCAS3 is essential for mouse development and cardiovascular patterning.

Rudhira/Breast Carcinoma Amplified Sequence 3 (BCAS3) is a cytoskeletal protein that promotes directional cell migration and angiogenesis in vitro and is implicated in human carcinomas and coronary artery disease. To study the role of Rudhira during development in vivo, we generated the first knockout mouse for rudhira and show that Rudhira is essential for mouse development. Rudhira null embryos die at embryonic day (E) 9.5 accompanied by severe vascular patterning defects in embryonic and extra-embryonic tissues. To identify the molecular processes downstream of rudhira, we analyzed the transcriptome of intact knockout yolk sacs. Genome-wide transcriptome analysis showed that Rudhira functions in angiogenesis and its related processes such as cell adhesion, extracellular matrix organization, peptidase activity and TGFß signaling. Since Rudhira is also expressed in endothelial cells (ECs), we further generated Tie2Cre-mediated endothelial knockout (CKO) of rudhira. CKO embryos survive to E11.5 and similar to the global knockout, display gross vascular patterning defects, showing that endothelial Rudhira is vital for development. Further, Rudhira knockdown ECs in culture fail to sprout in a spheroid-sprouting assay, strongly supporting its role in vascular patterning. Our study identifies an essential role for Rudhira in blood vessel remodeling and provides a mouse model for cardiovascular development.

Networks that link cytoskeletal regulators and diaphragm proteins underpin filtration function in Drosophila nephrocytes.

Insect nephrocytes provide a valuable model for kidney disease, as they are structurally and functionally homologous to mammalian kidney podocytes. They possess an exceptional macromolecular assembly, the nephrocyte diaphragm (ND), which serves as a filtration barrier and helps maintain tissue homeostasis by filtering out wastes and toxic products. However, the elements that maintain nephrocyte architecture and the ND are not understood. We show that Drosophila nephrocytes have a unique cytoplasmic cluster of F-actin, which is maintained by the microtubule cytoskeleton and Rho-GTPases. A balance of Rac1 and Cdc42 activity as well as proper microtubule organization and endoplasmic reticulum structure, are required to position the actin cluster. Further, ND proteins Sns and Duf also localize to this cluster and regulate organization of the actin and microtubule cytoskeleton. Perturbation of any of these inter-dependent components impairs nephrocyte ultrafiltration. Thus cytoskeletal components, Rho-GTPases and ND proteins work in concert to maintain the specialized nephrocyte architecture and function.