Myeloid Lineage Research Articles

Immune‐mediated haemolytic anaemia with severe thrombocytopenia in a Pembroke Welsh Corgi

AbstractAn 8‐year‐old, female, spayed Pembroke Welsh Corgi presented for a 3‐day history of worsening lethargy and pale pink mucous membranes. Hematological analysis revealed a normocytic, normochromic, regenerative anaemia, positive saline agglutination and marked thrombocytopenia, supportive of a diagnosis of immune‐mediated haemolytic anaemia and thrombocytopenia, either as a secondary result of immune‐mediated haemolytic anaemia or an additional immune‐mediated process. Due to continued decreases in packed cell volume despite immunosuppressive therapy and packed red blood cell transfusion, euthanasia was elected. Gross postmortem examination revealed cutaneous and visceral petechiae to ecchymoses, visceral icterus, and moderate splenomegaly. Microscopically, the bone marrow was hypercellular with moderate to marked increase in numbers of erythroid lineage cells relative to myeloid lineage cells. Few macrophages displayed erythrophagia. Given the drastically worsening thrombocytopenia, immune‐mediated thrombocytopenia was considered more likely, but this could not be entirely verified. This presentation of immune‐mediated haemolytic anaemia with thrombocytopenia illustrates the clinical diagnosis and management of immune‐mediated haematological diseases in dogs.

Clinical and research updates on the VISTA immune checkpoint: immuno-oncology themes and highlights.

Immune checkpoints limit the activation of the immune system and serve an important homeostatic function but can also restrict immune responses against tumors. Inhibition of specific immune checkpoint proteins such as the B7:CD28 family members programmed cell death protein-1 (PD-1) and cytotoxic T-lymphocyte antigen-4 (CTLA-4) has transformed the treatment of various cancers by promoting the anti-tumor activation of immune cells. In contrast to these effects, the V-domain immunoglobulin suppressor of T-cell activation (VISTA) regulates the steady state of the resting immune system and promotes homeostasis by mechanisms distinct from PD-1 and CTLA-4. The effects of VISTA blockade have been shown to include a decrease in myeloid suppression coupled with proinflammatory changes by mechanisms that are separate and distinct from other immune checkpoint proteins; in some preclinical studies these immune effects appear synergistic. Given the potential benefits of VISTA blockade in the context of cancer therapy, the second Annual VISTA Symposium was convened virtually on September 23, 2022, to review new research from investigators and immuno-oncology experts. Discussions in the meeting extended the knowledge of VISTA biology and the effects of VISTA inhibition, particularly on cells of the myeloid lineage and resting T cells, as three candidate anti-VISTA antibodies are in, or nearing, clinical development.

Multimodal cartography of human lymphopoiesis reveals B and T/NK/ILC lineages are subjected to differential regulation

The developmental cartography of human lymphopoiesis remains incompletely understood. Here, we establish a multimodal map demonstrating that lymphoid specification follows independent direct or stepwise hierarchic routes converging toward the emergence of newly characterized CD117lo multi-lymphoid progenitors (MLPs) that undergo a proliferation arrest before entering the CD127- (NK/ILC/T) or CD127+ (B)lymphoid pathways. While the differentiation of CD127- early lymphoid progenitors is mainly driven by Flt3 signaling, emergence of their CD127+ counterparts is regulated cell-intrinsically and depends exclusively on the divisional history of their upstream precursors, including hematopoietic stem cells. Further, transcriptional mapping of differentiation trajectories reveals that whereas myeloid granulomonocytic lineages follow continuous differentiation pathways, lymphoid trajectories are intrinsically discontinuous and characterized by sequential waves of cell proliferation allowing pre-commitment amplification of lymphoid progenitor pools. Besides identifying new lymphoid specification pathways and regulatory checkpoints, our results demonstrate that NK/ILC/T and B lineages are under fundamentally distinct modes of regulation. (149 words).

Morphological Spectrum of Bone Marrow Aspirates in Infections: A Clinico-Hematological Analysis

Abstract Context: Bone marrow examination (BME) is an invaluable tool for cases with pyrexia of unknown origin and pancytopenia. However, it is under-utilized for diagnosing infectious etiology and there is a paucity of literature regarding its role in infective pathology. Aims: This study aims to bring to light the role of BME in diagnosing infectious pathology. Settings and Design: A retrospective study was carried out on bone marrow aspirates (BMAs) sent to the hematology department over the past 4 years. Clinical details, peripheral smears and BMA were retrieved from the records and analyzed. Subjects and Methods: Leishman-stained peripheral smears and BMA were studied along with bone marrow biopsy wherever feasible. Results: A total of 52 cases were studied. The most common clinical presentation was fever, clinical finding was splenomegaly and hematological finding was anemia. Based on the morphological findings in combination with clinical history, cases were categorized into–parasitic (26.9%), viral (23.1%), tubercular (11.5%), and nonspecific infections (38.5%). Parasites such as Leishmania donovani, microfilaria, plasmodium falciparum, and vivax were reported in 14/52 (27%) cases. Associated BMA findings were plasmacytosis, eosinophilia, reactive lymphocytosis, or dyserythopoiesis. In 38% (20/52) cases, no specific cause of infection was found in the bone marrow. These patients showed histiocytosis, hemophagocytosis, maturation arrest in myeloid lineage, relative myeloid hyperplasia, dysmyelopoiesis, toxic granulation/vacuolation in myeloid cells, lymphocytosis, increased plasma cells or monocytosis in marrow. Conclusions: Increased histiocytes, hemophagocytosis, dysplastic changes, maturation arrest, relative myeloid hyperplasia or reactive plasmacytosis, lymphocytosis, and monocytosis are BMA features which must alert the pathologist towards an infectious disease process, a knowledge of these changes can help extend the scope of BME beyond hemato-lymphoid malignancies.

BCR::ABL1 negative myeloproliferative neoplasms: A review focused on essential thrombocythemia and polycythemia vera.

The classical myeloproliferative neoplasms are divided into chronic myeloid leukemia, and the Philadelphia negative polycythemia vera, essential thrombocythemia and primary myelofibrosis. These are heterogenous diseases, originating from the clonal proliferation of myeloid stem cells, resulting in increased mature cell numbers in one or more myeloid lineages. The most commonly seen mutations in the Philadelphia negative myeloproliferative neoplasms include those in Janus kinase, myeloproliferative leukemia protein and the calreticulin genes. Philadelphia negative myeloproliferative neoplasms occur infrequently, with a combined annual incidence of 2.58 per 100,000. There are many overlapping symptoms of Philadelphia negative MPNs, such as fatigue, night sweats, hepatosplenomegaly and circulatory symptoms due to increased cell numbers. Total Symptom Score of the MPN Symptom Assessment Form is used to assess symptom burden on patients. The most worrisome complications are thrombo-hemorrhagic events, and risk stratification is especially important as treatment of disease is based on their category. Phlebotomy and aspirin are the mainstay of treatment in low-risk polycythemia vera and essential thrombocythemia patients, whereas high-risk disease calls for additional cytoreduction, usually with hydroxyurea.

Immunomodulatory Properties of Citrus limon Extracts on BALB/c Mouse Lymphoid and Myeloid Lineage Cells

Immunomodulatory Properties of Citrus limon Extracts on BALB/c Mouse Lymphoid and Myeloid Lineage Cells

Induction of mitochondrial recycling reverts age-associated decline of the hematopoietic and immune systems.

Aging compromises hematopoietic and immune system functions, making older adults especially susceptible to hematopoietic failure, infections and tumor development, and thus representing an important medical target for a broad range of diseases. During aging, hematopoietic stem cells (HSCs) lose their blood reconstitution capability and commit preferentially toward the myeloid lineage (myeloid bias)1,2. These processes are accompanied by an aberrant accumulation of mitochondria in HSCs3. The administration of the mitochondrial modulator urolithin A corrects mitochondrial function in HSCs and completely restores the blood reconstitution capability of 'old' HSCs. Moreover, urolithin A-supplemented food restores lymphoid compartments, boosts HSC function and improves the immune response against viral infection in old mice. Altogether our results demonstrate that boosting mitochondrial recycling reverts the aging phenotype in the hematopoietic and immune systems.

T cell differentiation drives the negative selection of pathogenic mitochondrial DNA variants.

Pathogenic mitochondrial DNA (mtDNA) single-nucleotide variants are a common cause of adult mitochondrial disease. Levels of some variants decrease with age in blood. Given differing division rates, longevity, and energetic requirements within haematopoietic lineages, we hypothesised that cell-type-specific metabolic requirements drive this decline. We coupled cell-sorting with mtDNA sequencing to investigate mtDNA variant levels within progenitor, myeloid, and lymphoid lineages from 26 individuals harbouring one of two pathogenic mtDNA variants (m.3243A>G and m.8344A>G). For both variants, cells of the T cell lineage show an enhanced decline. High-throughput single-cell analysis revealed that decline is driven by increasing proportions of cells that have cleared the variant, following a hierarchy that follows the current orthodoxy of T cell differentiation and maturation. Furthermore, patients with pathogenic mtDNA variants have a lower proportion of T cells than controls, indicating a key role for mitochondrial function in T cell homeostasis. This work identifies the ability of T cell subtypes to selectively purify their mitochondrial genomes, and identifies pathogenic mtDNA variants as a new means to track blood cell differentiation status.

Complementary and countervailing actions of Jak2 and Ikk2 in hematopoiesis in mice

Hyperactivation of JAK2 kinase is a unifying feature of human Ph- myeloproliferative neoplasms (MPNs), most commonly due to the JAK2 V617F mutation. Mice harboring a homologous mutation in the Jak2 locus exhibit a phenotype resembling polycythemia vera. NFκB pathway hyperactivation is present in myeloid neoplasms, including MPNs, despite scarcity of mutations in NFκB pathway genes. To determine the impact of NFκB pathway hyperactivation in conjunction with Jak2 V617F, we utilized Ikk2 (Ikk2-CA) mice. Pan-hematopoietic Ikk2-CA alone produced depletion of hematopoietic stem cells and B cells. When combined with the Jak2 V617F mutation, Ikk2-CA rescued the polycythemia vera phenotype of Jak2 V617F. Likewise, Jak2 V617F ameliorated defects in hematopoiesis produced by Ikk2-CA. Single-cell RNA sequencing of hematopoietic stem and progenitor cells revealed multiple genes antagonistically regulated by Jak2 and Ikk2, including subsets whose expression was altered by Jak2 V617F and/or Ikk2-CA but partly or fully rectified in the double mutant. We hypothesize that Jak2 promotes hematopoietic stem cell population self-renewal, whereas Ikk2 promotes myeloid lineage differentiation, and biases cell fates at several branch points in hematopoiesis. Jak2 and Ikk2 both regulate multiple genes affecting myeloid maturation and cell death. Therefore, the presence of dual Jak2 and NFκB hyperactivation may present neomorphic therapeutic vulnerabilities in myeloid neoplasms.

CRISPR/dCas9 DNA methylation editing is heritable during human hematopoiesis and shapes immune progeny

Aging is associated with an abnormal increase in DNA methylation (DNAm) in human gene promoters, including in bone marrow stem cells. DNAm patterns are further perturbed in hematological malignancies such as acute myeloid leukemia but the physiological significance of such epigenetic changes is unknown. Using epigenetic editing of human stem/progenitor cells (HSPCs), we show that p15 methylation affects hematopoiesis in vivo. We edited the CDKN2B (p15) promoter and ARF (p14) using dCas9-3A3L and observed DNAm spreading beyond the gRNA location. We find that despite a transient delivery system, DNAm is maintained during myeloid differentiation in vitro, and hypermethylation of the p15 promoter reduces gene expression. In vivo, edited human HSPCs can engraft the bone marrow of mice and targeted DNAm is maintained in HSPCs long term. Moreover, epigenetic changes are conserved and inherited in both myeloid and lymphoid lineages. Although the proportion of myeloid (CD33+) and lymphoid (CD19+) cells is unaffected, monocyte (CD14+) populations decreased and granulocytes (CD66b+) increased in mice engrafted with p15 hypermethylated HSPCs. Monocytes derived from p15 hypermethylated HSPCs appear to be activated and show increased inflammatory transcriptional programs. We believe these findings have clinical relevance since we found p15 promoter methylation in the peripheral blood of patients with clonal hematopoiesis. Our study shows DNAm can be targeted and maintained in human HSPCs and demonstrated functional relevance of aberrant DNAm on the p15 locus. As such, other aging-associated aberrant DNAm may impact hematopoiesis in vivo.

Current therapies for classic myeloproliferative neoplasms: A focus on pathophysiology and supportive care.

This article concisely evaluates current therapies that have received regulatory approval for the treatment of classic myeloproliferative neoplasms (MPNs). Pertinent pathophysiology and supportive care are discussed. Emerging therapies are also briefly described. MPNs are a heterogeneous group of diseases characterized by acquired abnormalities of hematopoietic stem cells (HSCs), resulting in the generation of transformed myeloid progenitor cells that overproduce mature and immature cells within the myeloid lineage. Mutations in JAK2 and other driver oncogenes are central to the genetic variability of these diseases. Cytoreductive therapies such as hydroxyurea, anagrelide, interferon, and therapeutic phlebotomy aim to lower the risk of thrombotic events without exposing patients to an increased risk of leukemic transformation. However, no comparisons can be made between these therapies, as reduction of thrombotic risk has not been used as an endpoint. On the other hand, Janus kinase (JAK) inhibitors such as ruxolitinib, fedratinib, pacritinib, and momelotinib (an investigational agent at the time of writing) directly target the constitutively activated JAK-signal transducer and activator of transcription (JAK-STAT) pathway of HSCs in the bone marrow. Mutations of genes in the JAK-STAT signaling pathway provide a unifying understanding of MPNs, spur therapeutic innovations, and represent opportunities for pharmacists to optimize mitigation strategies for both disease-related and treatment-related adverse effects. Treatment options for MPNs span a wide range of disease mechanisms. The growth of targeted therapies holds promise for expanding the treatment arsenal for these rare, yet complex diseases and creates opportunities to optimize supportive care for affected patients.

Longitudinal Analysis of Leukocyte Total and Differential Count of Rhesus Macaques (Macaca mulatta) after Total-Body Irradiation.

Archival data of leukocyte count and the differentials obtained from control and irradiated Rhesus Macaques (Macaca mulatta) were statistically analyzed to understand the long-term effect of ionizing radiation exposure. Nine animals received total-body irradiation (TBI) of 7.2-8.4 Gy at 3-4 years old. Twelve animals served as age-matched controls with no radiation exposure. The complete blood cell count dataset was obtained during regular health exams every 2-6 months for 8 years from their age of 8 to 17 years old. Linear mixed models for leukocyte, neutrophil, lymphocyte, and monocyte counts and their percentages were successfully developed. Estimated marginal means calculated based on the models revealed statistically significant elevations in leukocyte and neutrophil counts and neutrophil percentages in irradiated animals compared to the controls. Lymphocyte percentage was significantly lower in irradiated animals. Longitudinal trends for both control and irradiated animals were consistent with expected trends of aging in hematopoiesis, which is skewed towards production of myeloid lineage cells such as neutrophils and monocytes rather than lymphoid cells. Longitudinal trends from irradiated animals suggested the age-related increase in neutrophils and decrease in lymphocytes were stronger than in the controls, although the difference did not reach statistical significance. The mechanism of the long-term effects in the hematopoietic system were not investigated. However, the results suggest ionizing radiation causes long-term effects on some of the factors implicated in hematopoietic aging, possibly inducing early-onset or accelerated aging in the hematopoietic system. Extended analysis with observations including before and after the follow-up period in this study will be beneficial to understand the timeline and features of the long-term response.

Systemic administration of STING agonist promotes myeloid cells maturation and antitumor immunity through regulating hematopoietic stem and progenitor cell fate.

STING is a pivotal mediator of effective innate and adaptive anti-tumor immunity; however, intratumoral administration of STING agonists have shown limited therapeutic benefit in clinical trials. The systemic effect of the intravenous delivery of STING agonists in cancer is not well-defined. Here, we demonstrated that systemic administration of STING agonist inhibited melanoma growth, improved inflammatory effector cell infiltration, and induced bone marrow mobilization and extramedullary hematopoiesis, causing widespread changes in immune components in the peripheral blood. The systemically administered STING agonist promoted HSC expansion and influenced lineage fate commitment, which was manifested as the differentiation of HSPCs was skewed toward myeloid cells at the expense of B-cell lymphopoiesis and erythropoiesis. Transcriptome analysis revealed upregulation of myeloid lineage differentiation-related and type I interferon-related genes. This myeloid-biased differentiation promoted the production and maturation of myeloid cells toward an activated phenotype. Furthermore, depletion of Gr-1+ myeloid cells attenuated the anti-tumor immunity of STING agonist. Our findings reveal the anti-tumor mechanism of systemic administration of STING agonist that involves modulating HSPC differentiation and promoting myeloid cells maturation. Our study may help explain the limited clinical activity of STING agonists administered intratumorally.

Innate Immune System in the Context of Radiation Therapy for Cancer.

Radiation therapy (RT) remains an integral component of modern oncology care, with most cancer patients receiving radiation as a part of their treatment plan. The main goal of ionizing RT is to control the local tumor burden by inducing DNA damage and apoptosis within the tumor cells. The advancement in RT, including intensity-modulated RT (IMRT), stereotactic body RT (SBRT), image-guided RT, and proton therapy, have increased the efficacy of RT, equipping clinicians with techniques to ensure precise and safe administration of radiation doses to tumor cells. In this review, we present the technological advancement in various types of RT methods and highlight their clinical utility and associated limitations. This review provides insights into how RT modulates innate immune signaling and the key players involved in modulating innate immune responses, which have not been well documented earlier. Apoptosis of cancer cells following RT triggers immune systems that contribute to the eradication of tumors through innate and adoptive immunity. The innate immune system consists of various cell types, including macrophages, dendritic cells, and natural killer cells, which serve as key mediators of innate immunity in response to RT. This review will concentrate on the significance of the innate myeloid and lymphoid lineages in anti-tumorigenic processes triggered by RT. Furthermore, we will explore essential strategies to enhance RT efficacy. This review can serve as a platform for researchers to comprehend the clinical application and limitations of various RT methods and provides insights into how RT modulates innate immune signaling.

SDPS-34 SCREENING TUMOR INFILTRATING LEUKOCYTES IN GLIOBLASTOMA REVEALS A CORRELATION WITH EGFR POSITIVE TUMOR CELLS WITH PROGNOSTIC IMPLICATIONS

Abstract Glioblastoma (GBM) is a grade IV brain tumor that is difficult to manage and associated with high rates of relapse and mortality. Treatment failures are attributed to the blood-brain barrier, increased tumor vascularity, tumor heterogeneity, numerous molecular mutations, and an immunosuppressive microenvironment. The immune microenvironment is comprised of tumor-infiltrating leucocytes (TILs), including several immunosuppressive cell types such as myeloid derived suppressor cells (MDSCs) (immature TILs of myeloid lineage). These tumor supporting immune cells augment the microenvironment and create conditions for immune suppression, contributing to tumor progression and negatively impacting patient survival. The aim of this study was to characterize the TILs in individual patients and correlate these findings with treatment course and survival. We hypothesized that a higher prevalence of MDSCs in tumors would be associated with lower survival rates. In order to investigate this, tumor specimens were collected from GBM patients who underwent tumor resection at Corewell Health (IRB# 2020-024). Fresh GBM samples were collected into tumor storage solution and immediately dissociated into single cell suspensions using a GentleMACS dissociator. The subsequent single cell suspension was stained with a panel of antibodies for TILs and tumor surface markers EGFR and PDGFRA. Flow cytometric analysis of these specimen revealed that the TILs comprising the tumor microenvironment were primarily dominated by CD11b+ myeloid cells, with prevalent MDSCs negatively associated with survival in our study group. Interestingly, MDSCs were negatively correlated with EGFR+ tumor cells while CD3+ T cells were positively correlated. In addition, patients previously treated with either temozolomide or bevacizumab had significantly different TIL immunophenotypes. Together, these data suggest that screening approaches utilizing these techniques may elucidate how tumor cells and TILs may be interacting and reacting to treatment and may provide additional diagnostic and prognostic avenues ultimately leading to improved outcomes for these patients.

Analysis of Tumor Microenvironment Changes after Neoadjuvant Chemotherapy with or without Bevacizumab in Advanced Ovarian Cancer (GEICO-89T/MINOVA Study).

The aim of our study was to elucidate the impact of bevacizumab added to neoadjuvant chemotherapy (NACT) on the tumor immune microenvironment and correlate the changes with the clinical outcome of the patients. IHC and multiplex immunofluorescence for lymphoid and myeloid lineage markers were performed in matched tumor samples from 23 patients with ovarian cancer enrolled in GEICO 1205/NOVA clinical study before NACT and at the time of interval cytoreductive surgery. Our results showed that the addition of bevacizumab to NACT plays a role mainly on lymphoid populations at the stromal compartment, detecting a significant decrease of CD4+ T cells, an increase of CD8+ T cells, and an upregulation in effector/regulatory cell ratio (CD8+/CD4+FOXP3+). None of the changes observed were detected in the intra-epithelial site in any arm (NACT or NACT-bevacizumab). No differences were found in myeloid lineage (macrophage-like). The percentage of Treg populations and effector/regulatory cell ratio in the stroma were the only two variables significantly associated with progression-free survival (PFS). The addition of bevacizumab to NACT did not have an impact on PFS in the GEICO 1205 study. However, at the cellular level, changes in CD4+, CD8+ lymphocyte populations, and CD8+/CD4+FOXP3 ratio have been detected only at the stromal site. On the basis of our results, we hypothesize about the existence of mechanisms of resistance that could prevent the trafficking of T-effector cells into the epithelial component of the tumor as a potential explanation for the lack of efficacy of ICI in the first-line treatment of advanced epithelial ovarian cancer. See related commentary by Soberanis Pina and Oza, p. 12.

Early activation of inflammatory pathways in UBA1-mutated hematopoietic stem and progenitor cells in VEXAS

VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome is a pleiotropic, severe autoinflammatory disease caused by somatic mutations in the ubiquitin-like modifier activating enzyme 1 (UBA1) gene. To elucidate VEXAS pathophysiology, we performed transcriptome sequencing of single bone marrow mononuclear cells and hematopoietic stem and progenitor cells (HSPCs) from VEXAS patients. HSPCs are biased toward myeloid (granulocytic) differentiation, and against lymphoid differentiation in VEXAS. Activation of multiple inflammatory pathways (interferons and tumor necrosis factor alpha) occurs ontogenically early in primitive hematopoietic cells and particularly in the myeloid lineage in VEXAS, and inflammation is prominent in UBA1-mutated cells. Dysregulation in protein degradation likely leads to higher stress response in VEXAS HSPCs, which positively correlates with inflammation. TCR usage is restricted and there are increased cytotoxicity and IFN-γ signaling in Tcells. In VEXAS syndrome, both aberrant inflammation and myeloid predominance appear intrinsic to hematopoietic stem cells mutated in UBA1.

Functional role of SAP18 protein: From transcriptional repression to splicing regulation.

Sin3 associated protein 18 (SAP18) is an evolutionary conserved protein, originally discovered in a complex with the transcriptional regulatory protein, Sin3. Subsequent investigations revealed SAP18 as an integral splicing component of the exon junction complex (EJC)-associated apoptosis-and splicing-associated protein (ASAP)/PNN-RNPS1-SAP18 (PSAP) complex. In association with Sin3, SAP18 contributes toward transcriptional repression of genes implicated in embryonic development, stress response, human immunodeficiency virus type 1 replication, and tumorigenesis. As a part of EJC, SAP18 mediates alternative splicing events and suppresses the cryptic splice sites present within flanking regions of exon-exon junctions. In this review, we provide a thorough discussion on SAP18, focussing on its conserved dual role in transcriptional regulation and messenger RNA splicing. Recent research on the involvement of SAP18 in the emergence of cancer and human disorders has also been highlighted. The potential of SAP18 as a therapeutic target is also discussed in these recent studies, particularly related to malignancies of the myeloid lineage.

Myeloid lineage switch following CD7-targeted chimeric antigen receptor T-cell therapy in relapsed/refractory T-cell acute lymphoblastic leukemia.

Not available.

ThPOK is a critical multifaceted regulator of myeloid lineage development.

The transcription factor ThPOK (encoded by Zbtb7b) is well known for its role as a master regulator of CD4 lineage commitment in the thymus. Here, we report an unexpected and critical role of ThPOK as a multifaceted regulator of myeloid lineage commitment, differentiation and maturation. Using reporter and knockout mouse models combined with single-cell RNA-sequencing, progenitor transfer and colony assays, we show that ThPOK controls monocyte-dendritic cell versus granulocyte lineage production during homeostatic differentiation, and serves as a brake for neutrophil maturation in granulocyte lineage-specified cells through transcriptional regulation of lineage-specific transcription factors and RNA via altered messenger RNA splicing to reprogram intron retention.