An erythroid enhancer of BCL11A subject to genetic variation determines fetal hemoglobin level

Development of Polygenic Risk Score for Persistent Albuminuria in Children and Adults With Sickle Cell Anemia

Albuminuria is associated with high-risk apolipoprotein-L1 variants (APOL1 G1/G2) in patients with sickle cell anemia (SCA). However, this gene variant does not account for all chronic kidney disease (CKD) risk. We hypothesized that we could develop a polygenic risk score (PRS) for CKD in SCA, combining APOL1 G1/G2 with other candidate genes that modify SCA severity and further stratify patients into risk categories based on this risk score. Variants in APOL1, HMOX1 (rs743811), BCL11A (rs1424407), and α-thalassemia (α -3.7) were identified in children with SCA enrolled in the Sickle Cell Clinical Research and Intervention Program longitudinal cohort (SCCRIP). We individually tested the association of these variants with persistent albuminuria, tested a three-variant PRS (PRS-3) (APOL1, BCL11A (rs1424407), and α-3.7), and developed a four-variant PRS (PRS-4) after adding HMOX1 (rs743811) to PRS-3 using the summation of high-risk alleles. An adult SCA cohort from the University of Illinois, Chicago (UIC), was used for validation. Persistent albuminuria was defined as having a urine albumin-to-creatinine ratio (UACR) ≥ 30 mg/g on at least 2 of 3 consecutive measurements. In both cohorts, APOL1 risk variants increased the risk while α-thalassemia protected against persistent albuminuria. PRS-4 was significantly associated with persistent albuminuria (SCCRIP: p = 0.004; UIC: p = 0.00016). When stratifying patients into three and four risk categories based on the PRS, 58% and 86% of the high-risk (PRS-3) and 54% and 89% of very high-risk (PRS-4) categories developed persistent albuminuria cases in the SCCRIP and UIC cohorts, respectively. A PRS may identify high-risk SCA patients for albuminuria. Applying this PRS to guide the early implementation of disease modifiers and renoprotective therapies may help reduce the burden of SCA-related CKD. Trial Registration: NCT02098863.

Advances in Gene Therapy for Sickle Cell Disease: From Preclinical Innovations to Clinical Implementation and Access Challenges

Sickle cell disease (SCD) is a hereditary blood disorder caused by a specific mutation in the β-globin gene, leading to the production of hemoglobin S, which deforms red blood cells, causing occlusion in small blood vessels. This results in pain, anemia, organ damage, infections, and increased stroke risk. Treatment options, including disease-modifying therapies and curative hematopoietic stem cell transplants, have limited accessibility. Recently, autologous gene therapy has emerged as a promising curative option, particularly for SCD. Gene editing techniques such as CRISPR, base editing, and prime editing offer potential to correct this mutation. In this review, we discuss recent preclinical studies and clinical trials of gene and cell therapies, focusing on the progress of FDA-approved treatments like Lyfgenia and Casgevy. We also examine the many challenges, including accessibility, safety, and long-term efficacy, which continue to shape the future of SCD gene therapy.

Current and future treatments for sickle cell disease: From hematopoietic stem cell transplantation to in vivo gene therapy

Sickle cell disease (SCD) is a single-gene disorder caused by a point mutation of the β-globin gene, resulting in hemolytic anemia, acute pain, multiorgan damage, and early mortality. Hydroxyurea is a first-line drug therapy that switches sickle-globin to non-pathogenic γ-globin; however, it requires lifelong oral administration. Allogeneic hematopoietic stem cell (HSC) transplantation allows for a one-time cure for SCD, albeit with histocompatibility limitations. Therefore, autologous HSC gene therapy was developed to cure SCD in a single treatment, without HSC donors. Current HSC gene therapy is based on the ex vivo culture of patients' HSCs with lentiviral gene addition and gene editing, followed by autologous transplantation back to the patient. However, the complexity of the treatment process and high costs hinder the universal application of ex vivo gene therapy. Therefore, the development of in vivo HSC gene therapy, where gene therapy tools are directly administered to patients, is desirable to provide a more accessible, cost-effective solution that can cure SCD worldwide. In this review, we discuss current treatments, including drug therapies, HSC transplantation, and ex vivo gene therapy; the development of gene therapy tools; and progress toward curative in vivo gene therapy in SCD.

Ex vivo modification of hematopoietic stem and progenitor cells for gene therapy

The development of viral vectors has been particularly critical for genetic therapies of hematological diseases. Before the development of retrovirus vectors (RVVs), gene transfer into mammalian cells was accomplished by transduction of DNA plasmids by chemical means and later by electroporation. The main limitation of these methods is the inefficiency of transfer of intact sequences, and particularly with electroporation significant cell death of the manipulated cells. The earliest successful human gene therapy trials utilized γ-RVVs and many of the techniques developed in the 1980s. A breakthrough for the field was the exploitation and development of HIV for transfer vectors, termed lentivirus vectors. In this review, we highlight uses of retro- and lentivirus vectors in monogenic diseases in which hematopoietic stem cells are used in the autologous setting to treat immunodeficiencies, hemoglobinopathies and metabolic diseases. The three authors' perspective represent experiences in the field over four decades that encompasses both basic translational research and development and oversight of early and ongoing gene therapy trials utilizing viral vectors.

Mapping disease loci to biological processes via joint pleiotropic and epigenomic partitioning

Genome-wide association studies (GWAS) have identified thousands of disease-associated loci, yet their interpretation remains limited by the heterogeneity of underlying biological processes. We propose Joint Pleiotropic and Epigenomic Partitioning (J-PEP), a clustering framework that integrates pleiotropic SNP effects on auxiliary traits and tissue-specific epigenomic data to partition disease-associated loci into biologically distinct clusters. To benchmark J-PEP against existing methods, we introduce a metric-Pleiotropic and Epigenomic Prediction Accuracy (PEPA)-that evaluates how well the clusters predict SNP-to-trait and SNP-to-tissue associations using off-chromosome data, avoiding overfitting. Applying J-PEP to GWAS summary statistics for 165 diseases/traits (average N = 290 K ), we attained 16-30% higher PEPA than pleiotropic or epigenomic partitioning approaches with larger improvements for well-powered traits, consistent with simulations; these gains arise from J-PEP's tendency to upweight correlated structure-signals present in both auxiliary trait and tissue data-thereby emphasizing shared components. For type 2 diabetes (T2D), J-PEP identified clusters refining canonical pathological processes while revealing underexplored immune and developmental signals. For hypertension (HTN), J-PEP identified stromal and adrenal-endocrine processes that were not identified in prior analyses. For neutrophil count, J-PEP identified hematopoietic, hepatic-inflammatory, and neuroimmune processes, expanding biological interpretation beyond classical immune regulation. Notably, integrating single-cell chromatin accessibility data refined bulk-based clusters, enhancing cell-type resolution and specificity. For T2D, single-cell data refined a bulk endocrine cluster to pancreatic islet β -cells, consistent with established β -cell dysfunction in insulin deficiency; for HTN, single-cell data refined a bulk endocrine cluster to adrenal cortex cells, consistent with a GO enrichment for neutrophil-mediated inflammation that implicates feedback between aldosterone production in the adrenal gland and local immune signaling. In conclusion, J-PEP provides a principled framework for partitioning GWAS loci into interpretable, tissue-informed clusters that provide biological insights on complex disease.

PRDM16-dependent antigen-presenting cells induce tolerance to gut antigens

The gastrointestinal tract is continuously exposed to foreign antigens in food and commensal microorganisms with potential to induce adaptive immune responses. Peripherally induced T regulatory (pTreg) cells are essential for mitigating inflammatory responses to these agents1-4. Although RORγt+ antigen-presenting cells (APCs) have been shown to programme gut microbiota-specific pTreg cells5-7, their definition remains incomplete, and the APC responsible for food tolerance has remained unknown. Here we identify an APC subset that is required for differentiation of both food- and microbiota-specific pTreg cells and for establishment of oral tolerance. Development and function of these APCs require expression of the transcription factors PRDM16 and RORγt, as well as a unique Rorc(t) cis-regulatory element. Gene expression, chromatin accessibility, and surface marker analysis establish the pTreg-inducing APCs as myeloid in origin, distinct from type 3 innate lymphoid cells, and sharing epigenetic profiles with classical dendritic cells, and designate them PRDM16+RORγt+ tolerizing dendritic cells (tolDCs). Upon genetic perturbation of tolDCs, we observe a substantial increase in food antigen-specific T helper 2 cells in lieu of pTreg cells, leading to compromised tolerance in mouse models of asthma and food allergy. Single-cell analyses of freshly resected mesenteric lymph nodes from a human organ donor, as well as multiple specimens of human intestine and tonsil, reveal candidate tolDCs with co-expression of PRDM16 and RORC and an extensive transcriptome shared with tolDCs from mice, highlighting an evolutionarily conserved role across species. Our findings suggest that a better understanding of how tolDCs develop and how they regulate T cell responses to food and microbial antigens could offer new insights into developing therapeutic strategies for autoimmune and allergic diseases as well as organ transplant tolerance.

A replication study of novel fetal hemoglobin-associated genetic variants in sickle cell disease-only cohorts

Sickle cell disease (SCD) is the most common monogenic disease in the world and is caused by mutations in the β-globin gene (HBB). Notably, SCD is characterized by extreme clinical heterogeneity. Inter-individual variation in fetal hemoglobin (HbF) levels strongly contributes to this patient-to-patient variability, with high HbF levels associated with decreased morbidity and mortality. Genetic association studies have identified and replicated HbF levels-associated variants at three loci: BCL11A, HBS1L-MYB, and HBB. In SCD patients, genetic variation at these three loci accounts for ~ 50% of HbF heritability. Genome-wide association studies (GWAS) in non-anemic and SCD patients of multiple ancestries have identified 20 new HbF-associated variants. However, these genetic associations have yet to be replicated in independent SCD cohorts. Here, we validated the association between HbF levels and variants at five of these new loci (ASB3, BACH2, PFAS, ZBTB7A, and KLF1) in up to 3740 SCD patients. By combining CRISPR inhibition and single-cell transcriptomics, we also showed that sequences near non-coding genetic variants at BACH2 (rs4707609) and KLF1 (rs2242514, rs10404876) can control the production of the β-globin genes in erythroid HUDEP-2 cells. Finally, we analyzed whole-exome sequence data from 1354 SCD patients but could not identify rare genetic variants of large effect on HbF levels. Together, our results confirm five new HbF-associated loci that can be functionally studied to develop new strategies to induce HbF expression in SCD patients.

Transcription factor networks disproportionately enrich for heritability of blood cell phenotypes

Most phenotype-associated genetic variants map to noncoding regulatory regions of the human genome, but their mechanisms remain elusive in most cases. We developed a highly efficient strategy, Perturb-multiome, to simultaneously profile chromatin accessibility and gene expression in single cells with CRISPR-mediated perturbation of master transcription factors (TFs). We examined the connection between TFs, accessible regions, and gene expression across the genome throughout hematopoietic differentiation. We discovered that variants within TF-sensitive accessible chromatin regions in erythroid differentiation, although representing <0.3% of the genome, show a ~100-fold enrichment for blood cell phenotype heritability, which is substantially higher than that for other accessible chromatin regions. Our approach facilitates large-scale mechanistic understanding of phenotype-associated genetic variants by connecting key cis-regulatory elements and their target genes within gene regulatory networks.

An evolving understanding of multiple causal variants underlying genetic association signals

Understanding how genetic variation contributes to phenotypic variation is a fundamental question in genetics. Genome-wide association studies (GWASs) have discovered numerous genetic associations with various human phenotypes, most of which contain co-inherited variants in strong linkage disequilibrium (LD) with indistinguishable statistical significance. The experimental and analytical difficulty in identifying the "causal variant" among the co-inherited variants has traditionally led mechanistic studies to focus on relatively simple loci, where a single functional variant is presumed to explain most of the association signal and affect a target gene. The notion that a single causal variant is responsible for an association signal, while other variants in LD are merely correlated, has often been assumed in functional studies. However, emerging evidence powered by high-throughput experimental tools and context-specific functional databases argues that even a single independent signal may involve multiple functional variants in strong LD, each contributing to the observed genetic association. In this perspective, we articulate this evolving understanding of causal variants through examples from both traditional locus-by-locus approaches and more recent high-throughput functional studies. We then discuss the implications and prospects of this notion in understanding the genetic architecture of complex traits and interpreting the variant-level causality in GWAS follow-up studies.

A differentiated β-globin gene replacement strategy uses heterologous introns to restore physiological expression

β-Hemoglobinopathies are common monogenic disorders. In sickle cell disease (SCD), a single mutation in the β-globin (HBB) gene results in dysfunctional hemoglobin protein, while in β-thalassemia, over 300 mutations distributed across the gene reduce β-globin levels and cause severe anemia. Genetic engineering replacing the whole HBB gene through homology-directed repair (HDR) is an ideal strategy to restore a benign genotype and rescue HBB expression for most genotypes. However, this is technically challenging because (1) the insert must not be homologous to the endogenous gene and (2) synonymous codon-optimized, intron-less sequences may not reconstitute adequate β-globin levels. Here, we developed an HBB gene replacement strategy using CRISPR-Cas9 that successfully addresses these challenges. We determined that a DNA donor containing a diverged HBB coding sequence and heterologous introns to avoid sequence homology provides proper physiological expression. We identified a DNA donor that uses truncated γ-globin introns, results in 34% HDR, and rescues β-globin expression in in vitro models of SCD and β-thalassemia in hematopoietic stem and progenitor cells (HSPCs). Furthermore, while HDR allele frequency dropped in vivo, it was maintained at ∼15%, demonstrating editing of long-term repopulating HSPCs. In summary, our HBB gene replacement strategy offers a differentiated approach by restoring naturally regulated adult hemoglobin expression.

Creating New Cis-Regulatory Elements of HBD to Reactivate Delta-Globin

β-thalassemia and sickle cell disease (SCD) are global monogenic blood system disorders, and reactivated δ-globin is expected to replace missing or abnormal β-globin. With the development of gene editing technology, activating γ-globin for treating β-thalassemia and SCD has been highly successful. However, δ-globin, as another important potential therapeutic target, has few related studies. Gene editing technology introduced cis-acting elements, including NF-Y, KLF1, GATA1, and TAL1, into the regulatory region of HBD, successfully activating the expression of δ-globin. It was confirmed that the activation effect of δ-globin was closely related to the location of the introduced cis-acting elements. In this study, the mutation creates a de novo binding site for KLF1 at -85∼93 bp upstream of the transcription start site of the HBD gene, as well as the site for TAL1 and GATA1 cobinding motifs at -59 to ∼-78 bp, which could effectively activate δ-globin.

Prdm16-dependent antigen-presenting cells induce tolerance to intestinal antigens

The gastrointestinal tract is continuously exposed to foreign antigens in food and commensal microbes with potential to induce adaptive immune responses. Peripherally induced T regulatory (pTreg) cells are essential for mitigating inflammatory responses to these agents1-4. While RORγt+ antigen-presenting cells (RORγt-APCs) were shown to program gut microbiota-specific pTreg5-7, their definition remains incomplete, and the APC responsible for food tolerance has remained elusive. Here, we identify a distinct subset of RORγt-APCs, designated tolerogenic dendritic cells (tDC), required for differentiation of both food- and microbiota-specific pTreg cells and for establishment of oral tolerance. tDC development and function require expression of the transcription factors Prdm16 and RORγt, as well as a unique Rorc(t) cis-regulatory element. Gene expression, chromatin accessibility, and surface marker analysis establish tDC as myeloid in origin, distinct from ILC3, and sharing epigenetic profiles with classical DC. Upon genetic perturbation of tDC, we observe a substantial increase in food antigen-specific T helper 2 (Th2) cells in lieu of pTreg, leading to compromised tolerance in mouse models of asthma and food allergy. Single-cell analyses of freshly resected mesenteric lymph nodes from a human organ donor, as well as multiple specimens of human intestine and tonsil, reveal candidate tDC with co-expression of PRDM16 and RORC and an extensive transcriptome shared with mice, highlighting an evolutionarily conserved role across species. Our findings suggest that a better understanding of how tDC develop and how they regulate T cell responses to food and microbial antigens could offer new insights into developing therapeutic strategies for autoimmune and allergic diseases as well as organ transplant tolerance.

CRISPR: fundamental principles and implications for anaesthesia

Clustered regularly interspaced short palindromic repeats (CRISPR)-based medical therapies are increasingly gaining regulatory approval worldwide. Consequently, patients receiving CRISPR therapy will come under the care of anaesthesiologists. An understanding of CRISPR, its technological implementations, and the characteristics of patients likely to receive this therapy will be essential to caring for this patient population. However, the role of CRISPR in anaesthesiology extends beyond simply caring for patients with prior CRISPR therapy. CRISPR has multiple direct potential applications in anaesthesia, particularly for managing chronic pain and critical illness. Additionally, given the unique skills anaesthesiologists possess, CRISPR potentially allows new roles for anaesthesiologists in the field of oncology. Consequently, CRISPR technology could enable new domains of anaesthetic practice. This review provides a primer on CRISPR for anaesthesiologists and an overview on how the technology could impact the field.

Selecting patients with sickle cell disease for gene addition or gene editing-based therapeutic approaches: Report on behalf of a joint EHA Specialized Working Group and EBMT Hemoglobinopathies Working Party consensus conference

Sickle cell disease (SCD) remains associated with reduced life expectancy and poor quality of life despite improvements observed in the last decades mostly related to comprehensive care, use of hydroxycarbamide, screening to identify patients at risk of strokes, and implementation of safe transfusion protocols. The course of the disease is highly variable, making it difficult to predict severity and response to therapy. Allogeneic hematopoietic stem cell transplantation potentially provides a cure with a relatively low rate of complications, but few patients have an HLA-identical sibling. The hopes of patients and healthcare providers have been raised after the initial excellent results of gene therapy studies. However, there is a strong contrast between the high expectations of families and patients and the limited availability of the product, which is technically complex and very expensive. In light of this consideration and of the limited data available on the long-term efficacy and toxicity of different gene therapy approaches, the European Hematology Association Red Cell & Iron Specialized Working Group (EHA SWG) and the hemoglobinopathy working part of the European Blood & Marrow Transplant (EBMT) Group have prioritized the development of recommendations for selection of patients with SCD who are good candidates for gene therapy. The decision-making algorithm was developed by a panel of experts in hemoglobinopathies and/or transplantation chosen by EHA SWG and EBMT, to discuss the selection of SCD patients for gene therapy and draw notes on the related clinical problems.

Exploratory Review and In Silico Insights into circRNA and RNA-Binding Protein Roles in γ-Globin to β-Globin Switching

β-globin gene cluster regulation involves complex mechanisms to ensure proper expression and function in RBCs. During development, switching occurs as γ-globin is replaced by β-globin. Key regulators, like BCL11A and ZBTB7A, repress γ-globin expression to facilitate this transition with other factors, like KLF1, LSD1, and PGC-1α; these regulators ensure an orchestrated transition from γ- to β-globin during development. While these mechanisms have been extensively studied, circRNAs have recently emerged as key contributors to gene regulation, but their role in β-globin gene cluster regulation remains largely unexplored. Although discovered in the 1970s, circRNAs have only recently been recognized for their functional roles, particularly in interactions with RNA-binding proteins. Understanding how circRNAs contribute to switching from γ- to β-globin could lead to new therapeutic strategies for hemoglobinopathies, such as sickle cell disease and β-thalassemia. This review uses the circAtlas 3.0 database to explore circRNA expressions in genes related to switching from γ- to β-globin expression, focusing on blood, bone marrow, liver, and spleen. It emphasizes the exploration of the potential interactions between circRNAs and RNA-binding proteins involved in β-globin gene cluster regulatory mechanisms, further enhancing our understanding of β-globin gene cluster expression.

Phenotype of sickle cell disease. Correlation of haplotypes and polymorphisms in cluster β, BCL11A, and HBS1L-MYB. Pilot study

Objective/Background

Sickle cell disease (SCD) is a monogenic disease with a highly variable phenotype depending on the amount of fetal hemoglobin (HbF), the main modulator. Variation of HbF levels among patients is genetically regulated. HbF determines both the phenotype of the disease and the response to treatment with the main drug used, hydroxyurea. The efforts of the researchers have focused on discovering the genetic factors responsible for HbF variation, mainly describing the haplotypes of the β cluster and single nucleotide polymorphisms (SNPs) at three different loci: BCL11A, HBS1L-MYB, and the β-globin cluster. This study aimed to determine the possible correlation between the number of SNPs and haplotypes with higher HbF levels in a cohort of patients with SCD. A positive association could explain why certain haplotypes, such as Senegal or Arab-Indian, show higher HbF levels and less severe disease.

Methods

To test this hypothesis, the characterization of haplotypes was performed using the PCR-RFLP technique and genotyping of three SNPs representative of the three loci with the greatest association with HbF variation: XmnI (rs7482144), BCL11A (rs4671393), and HBS1L-MYB (rs9376092).

Results

We found more SNPs in haplotypes related to higher HbF than those with less HbF, although only the SNP XmnI (rs7482144) showed a statistically significant association.

Conclusion

We found a direct correlation between haplotypes and the number of SNPs. Haplotypes with higher levels of HbF and less severe phenotypes showed a higher number of SNPs. Thus, the Benin and Bantu haplotypes traditionally associated with poor prognosis showed the fewest mutated SNPs.

BCL11A +58/+55 enhancer-editing facilitates HSPC engraftment and HbF induction in rhesus macaques conditioned with a CD45 antibody-drug conjugate

Editing the +58 region of the BCL11A erythroid enhancer has shown promise in treating β-globin disorders. To address variations in fetal hemoglobin (HbF) response, we investigated editing both +58 and +55 enhancers. Rhesus macaques transplanted with edited hematopoietic stem/progenitor cells (HSPCs) following busulfan conditioning exhibited durable, high-level (∼90%) editing frequencies post transplantation with sustained HbF reactivation over 4 years, without hematological perturbations. HbF levels were further boosted by stress erythropoiesis or hydroxyurea. Bone marrow analysis revealed that gene edits were predominantly programmed deletions, programmed inversions, and short indels, each disrupting the enhancer core TGN7-9WGATAR half E-box/GATA binding motifs. Nonprogrammed long deletions were disfavored in engrafting cells. CD45 antibody-drug conjugate (ADC) conditioning achieved comparable engraftment and HbF reactivation, whereas lentiviral vector tracking showed polyclonal reconstitution with dynamics similar to animals conditioned with total body irradiation (TBI) or busulfan. Joining CD45-ADC conditioning with combined enhancer editing presents an effective strategy for β-hemoglobinopathies, enabling durable HbF reactivation without chemotherapy.

Gene editing without ex vivo culture evades genotoxicity in human hematopoietic stem cells

Gene editing the BCL11A erythroid enhancer is a validated approach to fetal hemoglobin (HbF) induction for β-hemoglobinopathy therapy, though heterogeneity in edit allele distribution and HbF response may impact its safety and efficacy. Here, we compare combined CRISPR-Cas9 editing of the BCL11A +58 and +55 enhancers with leading gene modification approaches under clinical investigation. Dual targeting of the BCL11A +58 and +55 enhancers with 3xNLS-SpCas9 and two single guide RNAs (sgRNAs) resulted in superior HbF induction, including in sickle cell disease (SCD) patient xenografts, attributable to simultaneous disruption of core half E-box/GATA motifs at both enhancers. Unintended on-target outcomes of double-strand break (DSB) repair in hematopoietic stem and progenitor cells (HSPCs), such as long deletions and centromere-distal chromosome fragment loss, are a byproduct of cellular proliferation stimulated by ex vivo culture. Editing quiescent HSPCs bypasses long deletion and micronuclei formation and preserves efficient on-target editing and engraftment function.

Multiplex generation and single-cell analysis of structural variants in mammalian genomes

Studying the functional consequences of structural variants (SVs) in mammalian genomes is challenging because (i) SVs arise much less commonly than single-nucleotide variants or small indels and (ii) methods to generate, map, and characterize SVs in model systems are underdeveloped. To address these challenges, we developed Genome-Shuffle-seq, a method that enables the multiplex generation and mapping of thousands of SVs (deletions, inversions, translocations, and extrachromosomal circles) throughout mammalian genomes. We also demonstrate the co-capture of SV identity with single-cell transcriptomes, facilitating the measurement of SV impact on gene expression. We anticipate that Genome-Shuffle-seq will be broadly useful for the systematic exploration of the functional consequences of SVs on gene expression, the chromatin landscape, and three-dimensional nuclear architecture, while also initiating a path toward a minimal mammalian genome.

Dias-Logan syndrome with a de novo p.Leu360Profs*212 heterozygous pathogenic variant of BCL11A in a Chinese patient: A case report

Dias-Logan syndrome, also known as intellectual developmental disorder with persistence of fetal hemoglobin (HbF), or BCL11A-related intellectual developmental disorder, is an extremely rare neurogenetic disorder characterized by intellectual disability (ID), delayed psychomotor development, variable dysmorphic features, and asymptomatic persistence of fetal hemoglobin. The prevalence and incidence of this condition are currently unknown. We report an 8-year-old Han Chinese male patient with Dias-Logan syndrome who carries a de novo heterozygous pathogenic variant, c.1078dupC (p.Leu360Profs*212), in the BCL11A gene, leading to ID and γ-globin suppression, identified through trio-based whole exome sequencing (trio-WES). All his blood parameters were normal except for an elevated HbF level, which was 19.9% of total hemoglobin. Given the negative family history for ID, epilepsy, and alcohol consumption, de novo inheritance was presumed. Consequently, trio-WES analysis (parents and child) was conducted as it can identify potential new causal variants in the offspring. So far, a comprehensive understanding of the phenotypic spectrum of Dias-Logan syndrome and the impact of genotypic variation on disease severity is still lacking. Therefore, our case report enriches the existing literature on the clinical spectrum and genotype-phenotype correlations of BCL11A-related syndrome and provides some helpful information for diagnosis, management, and genetic counseling.

Enhancer regulatory networks globally connect non-coding breast cancer loci to cancer genes

BACKGROUND

Genetic studies have associated thousands of enhancers with breast cancer (BC). However, the vast majority have not been functionally characterized. Thus, it remains unclear how BC-associated enhancers contribute to cancer.

RESULTS

Here, we perform single-cell CRISPRi screens of 3513 regulatory elements associated with breast cancer to measure the impact of these regions on transcriptional phenotypes. Analysis of > 500,000 single-cell transcriptomes in two breast cancer cell lines shows that perturbation of BC-associated enhancers disrupts breast cancer gene programs. We observe BC-associated enhancers that directly or indirectly regulate the expression of cancer genes. We also find one-to-multiple and multiple-to-one network motifs where enhancers indirectly regulate cancer genes. Notably, multiple BC-associated enhancers indirectly regulate TP53. Comparative studies illustrate subtype specific functions between enhancers in ER + and ER - cells. Finally, we develop the pySpade package to facilitate analysis of single-cell enhancer screens.

CONCLUSIONS

Overall, we demonstrate that enhancers form regulatory networks that link cancer genes in the genome, providing a more comprehensive understanding of the contribution of enhancers to breast cancer development.

MYB represses ζ-globin expression through upregulating ETO2

Reactivating the embryonic ζ-globin gene represents a potential therapeutic approach to ameliorate the severe clinical phenotype of α-thalassemia and sickle cell disease. The transcription factor MYB has been extensively proven to be a master regulator of the γ-globin gene, but its role in the regulation of ζ-globin remains incompletely understood. Here, we report a mechanistic study on the derepression of ζ-globin both in vivo and in vitro. We show that MYB depletion in mouse models and human hematopoietic stem cells leads to consistent and remarkable reactivation of ζ-globin. Furthermore, multiomics analysis and functional validation of MYB-knockout and wild-type cell lines reveal that ETO2 functions as a novel repressor of ζ-globin through coordination with NuRD nucleosome remodeling and the deacetylation complex to modulate histone deacetylation of ζ-globin. Additionally, we evaluate the clinical significance of these findings by knocking out ETO2 in primary CD34 + cells from nondeletional hemoglobin H patients, which results in a significant increase in ζ-globin expression. The RNA-seq data reveal that key erythroid genes are more co-regulated by Myb and Eto2 than by Myb and Klf1, highlighting a distinctly enhanced erythroid-specific transcriptional impact within the MYB-ETO2 regulatory axis. Compared with ETO2 knockout alone, codepletion of ETO2 and BCL11A did not significantly activate ζ-globin, suggesting that the MYB-ETO2 pathway primarily silences ζ-globin. Our study reveals a linear MYB-ETO2 signaling pathway crucial for ζ-globin repression and offers new targets for treating α-thalassemia and sickle cell disease.

Role of B-Cell Lymphoma/Leukemia 11A in Normal and Malignant Hematopoiesis

B-cell lymphoma/leukemia 11A (BCL11A) is a crucial transcriptional regulator, widely recognized for its role in controlling fetal hemoglobin and its potential as a gene therapy target for inherited hemoglobinopathies. Beyond this, recent studies have also highlighted its key role in the maturation and function of immune cells and erythrocytes, mediated through the regulation of various molecules during hematopoietic development. The dysregulation of BCL11A disrupts downstream molecular pathways, contributing to the development of several hematological malignancies, particularly leukemias. This review provides a comprehensive overview of the role of BCL11A in normal and malignant hematopoiesis, details the hematological disorders associated with its dysregulation and explores the current therapeutic strategies targeting this transcription factor.

[A CRISPR/Cas approach to β-haemoglobinopathies]

Beta-haemoglobinopathies are severe genetic anemias caused by mutations that affect adult haemoglobin production. Many therapeutic approaches aim to reactivate the expression of the fetal hemoglobin genes. To this end, the CRISPR/Cas9 system has recently been used to genetically modify patients' hematopoietic stem/progenitor cells ex vivo and reactivate fetal hemoglobin expression in their erythroid progeny. More than 70 patients with severe β-thalassemia and sickle cell disease have been treated with the Casgevy® therapy. Most have achieved a significant improvement of clinical phenotype, with high editing efficiency in hematopoietic cells associated with normal or near normal hemoglobin levels. While the long-term safety and efficacy of this powerful approach still need to be evaluated, new strategies are being developed to further improve therapeutic outcomes, reduce potential genotoxicity and lower the costs of therapy.

Treating Sickle Cell Disease: Gene Therapy Approaches

Sickle cell disease (SCD) is a hereditary blood disorder characterized by the presence of abnormal hemoglobin molecules and thus distortion (sickling) of the red blood cells. SCD causes chronic pain and organ damage and shortens life expectancy. Gene therapy emerges as a potentially curative approach for people with SCD who lack a matched sibling donor for hematopoietic stem cell transplantation. Here, we review recent progress in gene therapy for SCD and focus on innovative technologies that target the genetic roots of the disease. We also review the challenges associated with gene therapy, including oncogenic risks, and the need for refined delivery methods. Despite these hurdles, the rapidly evolving landscape of gene therapy for SCD raises hope for a paradigm shift in the treatment of this debilitating disease. As research progresses, a deeper understanding of the molecular mechanisms involved and continuous improvements in gene-editing technologies promise to bring gene therapy for SCD closer to mainstream clinical application, offering a transformative, curative option for patients with this genetic disorder.

Gene therapy for sickle cell disease: recent advances, clinical trials and future directions

Sickle cell disease (SCD) is the most common inherited blood disorder worldwide, impacting millions and imposing severe healthcare challenges, particularly in resource-limited regions. Current treatments have variable efficacy and require lifelong adherence. Allogeneic Hematopoietic Stem Cell Transplantation can be curative but comes with significant side effects and limited donor availability limits its widespread applicability. Gene therapy, by addressing the root genetic causes, offers a revolutionary alternative. This article discusses the molecular mechanisms of SCD and β-thalassemia and highlights advancements in gene therapy, such as gene addition via lentiviral vectors and gene editing with CRISPR/Cas9 technology. Clinical trials have brought about significant progress but challenges remain, including leukemogenesis, delivery efficiency and cost. Future efforts must focus on enhancing efficiency, reducing costs, developing nongenotoxic conditioning regimens and methods for in vivo application.

Hotspots and status of Fetal Alpha-Thalassemia from 2009 to 2023: a bibliometric analysis

Objective

to evaluate the research status and development hotspots of fetal α-thalassemia by quantitatively analyzing the diagnostic status, key areas, related management measures and prospects of the disease by bibliometrics.

Methods

The global literature on fetal α-thalassemia and severe α-thalassemia from 2009-2023 in the Web of Science Core Collection (WOSCC) was visually analyzed by VOSviewer and CiteSpace.

Results

(1) The examination of the quantity of publications concerning fetal α-thalassemia indicates a rising tendency prior to 2018, followed by a decrease after 2018. (2)The United States, China, Italy, Thailand have published more papers, and the United States has more collaborating countries such as Italy and China. (3) Chiang Mai University and Harvard University are the top two institutions with the highest contribution. However, Chiang Mai University's H index (12) and citation frequency per article (8.05) are relatively low and the NC (6,342), H index (33) and citations per article (75.42) of Harvard University are higher than those of the other institutions. (4) Tongsong T, Gambari R and Fucharoen S are the top three prolific authors. Fucharoen S emerges as the most frequently cited author with 738 citations, excluding self-citations. (5) HEMOGLOBIN leading with 87 published papers (NC:601,IF: 0.82, H-index: 13), followed by BLOOD(58 papers, Nc: 3755, IF: 25.48, H-index: 40) and BLOOD CELLS MOLECULES AND DISEASES(39 papers, Nc: 729, IF: 2.37, H-index: 16). (6) The most cited article was published in science and the second and third cited articles were featured in the Proceedings of the National Academy of Sciences; the top 3 clusters of co-cited literature are "gene editing", "polymorphisms", "hydroxyurea". (7) Keywords analysis showe that the top two categories of keyword cluster focus on the prenatal diagnosis and the current treatment strategy of the disease, which remain the research hotspots.

Conclusions

Recent research on this topic has primarily focused on prenatal diagnosis and treatment strategies. A particular area of interest is the ongoing research on gene therapy.The advances in non-invasive diagnosis and therapeutic methods will change the current management approaches for fetal severe α-thalassemia in the future.

Safety and efficacy studies of CRISPR-Cas9 treatment of sickle cell disease highlights disease-specific responses

Fetal hemoglobin (HbF) reactivation expression through CRISPR-Cas9 is a promising strategy for the treatment of sickle cell disease (SCD). Here, we describe a genome editing strategy leading to reactivation of HbF expression by targeting the binding sites (BSs) for the lymphoma-related factor (LRF) repressor in the γ-globin promoters. CRISPR-Cas9 treatment in healthy donor (HD) and patient-derived HSPCs resulted in a high frequency of LRF BS disruption and potent HbF synthesis in their erythroid progeny. LRF BS disruption did not impair HSPC engraftment and differentiation but was more efficient in SCD than in HD cells. However, SCD HSPCs showed a reduced engraftment and a myeloid bias compared with HD cells. We detected off-target activity and chromosomal rearrangements, particularly in SCD samples (likely because of the higher overall editing efficiency) but did not impact the target gene expression and HSPC engraftment and differentiation. Transcriptomic analyses showed that the editing procedure results in the up-regulation of genes involved in DNA damage and inflammatory responses, which was more evident in SCD HSPCs. This study provides evidence of efficacy and safety for an editing strategy based on HbF reactivation and highlights the need of performing safety studies in clinically relevant conditions, i.e., in patient-derived HSPCs.

DNA regulatory element cooperation and competition in transcription

Regulation of eukaryotic transcription is a complex process that enables precise temporal and spatial control of gene expression. Promoters, which are cis-regulatory elements (CREs) located proximal to the transcription start site (TSS), selectively integrate regulatory cues from distal CREs, or enhancers, and their associated transcriptional machinery. In this review, we discuss current knowledge regarding CRE cooperation and competition impacting gene expression, including features of enhancer-promoter, enhancer-enhancer, and promoter-promoter interplay. We also provide an overview of recent insights into the underlying molecular mechanisms that facilitate physical and functional interaction of regulatory elements, such as the involvement of enhancer RNAs and biomolecular condensates. [BMB Reports 2024; 57(12): 509-520].

BCL11A expression worsens the prognosis of DLBCL and its co-expression with C-MYC predicts poor survival

Non-Hodgkin's lymphoma (NHL) is a significant global malignancy, with diffuse large B cell lymphoma (DLBCL) being the most prevalent subtype, accounting for 25-50 % of newly diagnosed cases in China. Despite a 60 % survival rate achieved with R-CHOP regiment for DLBCL, approximately 40 % of patients experience relapse or develop resistance to treatment. While the oncogenic transcription factor B-cell chronic lymphocytic leukaemia/lymphoma 11 A (BCL11A) has been implicated in various tumors, its specific role in DLBCL remains unclear. In this study, we conducted retrospective histomorphological and immunophenotypic analyses on paraffin sample tissues and collected fresh tissue samples for protein and mRNA analyses to investigate the relationship between BCL11A and DLBCL. Additionally, we classified DLBCL into subtypes based on cells of origin (COO) and examined the expressions of BCL11A, C-MYC, P53 and other protein expressions to better understand the factors contributing to poor clinical outcomes in DLBCL. Our findings revealed elevated BCL11A expression in DLBCL, with increased expression associated with worse prognosis and higher C-MYC expression. Patients exhibiting co-expression of C-MYC and BCL11A had significantly lower survival rates compared to those with singular expression. Furthermore, BCL11A protein expression levels demonstrated significant associations with P53 and C-MYC protein expression levels in the Germinal Center B-cell-like (GCB) subtype. These findings suggest that BCL11A may serve as a potential prognostic marker and therapeutic target for DLBCL.

CRISPR-based gene therapy for the induction of fetal hemoglobin in sickle cell disease

INTRODUCTION

Sickle cell disease is ameliorated and perhaps can be 'cured' if enough fetal hemoglobin is present in most erythrocytes. Hydroxyurea, which increases fetal hemoglobin levels, is widely available and effective, especially in children. Nevertheless, only cell-based gene therapy can achieve a 'curative' fetal hemoglobin threshold.

AREAS COVERED

We cover the path to modulating fetal hemoglobin gene expression and the use of CRISPR/Cas9 gene editing as a viable clinical modality for treating severe sickle cell disease relying on references obtained from PubMed. Mobilized autologous hematopoietic stem and progenitor cells are engineered with vectors that derepress genes that regulate fetal hemoglobin gene expression. Following myeloablative conditioning, gene-edited cells are reinfused, engrafted, and make large amounts of fetal hemoglobin. Within months, fetal hemoglobin forms more than 40% of the total hemoglobin and hemoglobin levels normalize; symptoms of sickle cell disease disappear.

EXPERT OPINION

Optimistically, these patients are 'cured,' but long term follow-up is needed. Although approved by regulatory agencies and highly efficacious, because of its technical imperatives and cost, this first gene editing therapeutic will be unavailable to most people with severe sickle cell disease. It is highly likely that improved methods of genomic editing will simplify gene therapy, reduce its costs, and lead to its wider applicability.

A tetramer of BCL11A is required for stable protein production and fetal hemoglobin silencing

Down-regulation of BCL11A protein reverses the fetal (HbF, α2γ2) to adult (HbA, α2β2) hemoglobin switch and is exploited in gene-based therapy for hemoglobin disorders. Because of reliance on ex vivo cell manipulation and marrow transplant, such therapies cannot lessen disease burden. To develop new small-molecule approaches, we investigated the state of BCL11A protein in erythroid cells. We report that tetramer formation mediated by a single zinc finger (ZnF0) is required for production of steady-state protein. Beyond its role in protein stability, the tetramer state is necessary for γ-globin gene repression, because an engineered monomer fails to engage a critical co-repressor complex. These aspects of BCL11A protein production identify tetramer formation as a vulnerability for HbF silencing and provide opportunities for drug discovery.

Genetic Modifiers of Hemoglobin Expression from a Clinical Perspective in Hemoglobinopathy Patients with Beta Thalassemia and Sickle Cell Disease

Hemoglobinopathies, namely β-thalassemia and sickle cell disease (SCD), are hereditary diseases, characterized by molecular genetic aberrations in the beta chains of hemoglobin. These defects affect the normal production of hemoglobin with severe anemia due to less or no amount of beta globins in patients with β-thalassemia (quantitative disorder), while SCD is a serious disease in which a mutated form of hemoglobin distorts the red blood cells into a crescent shape at low oxygen levels (qualitative disorder). Despite the revolutionary progress in recent years with the approval of gene therapy and gene editing for specific patients, there is an unmet need for highlighting the mechanisms influencing hemoglobin production and for the development of novel drugs and targeted therapies. The identification of the transcription factors and other genetic modifiers of hemoglobin expression is of utmost importance for discovering novel therapeutic approaches for patients with hemoglobinopathies. The aim of this review is to describe these complex molecular mechanisms and pathways affecting hemoglobin expression and to highlight the relevant investigational approaches or pharmaceutical interventions focusing on restoring the hemoglobin normal function by linking the molecular background of the disease with the clinical perspective. All the associated drugs increasing the hemoglobin expression in patients with hemoglobinopathies, along with gene therapy and gene editing, are also discussed.

Modeling common and rare genetic risk factors of neuropsychiatric disorders in human induced pluripotent stem cells

Recent genome-wide association studies (GWAS) and whole-exome sequencing of neuropsychiatric disorders, especially schizophrenia, have identified a plethora of common and rare disease risk variants/genes. Translating the mounting human genetic discoveries into novel disease biology and more tailored clinical treatments is tied to our ability to causally connect genetic risk variants to molecular and cellular phenotypes. When combined with the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated (Cas) nuclease-mediated genome editing system, human induced pluripotent stem cell (hiPSC)-derived neural cultures (both 2D and 3D organoids) provide a promising tractable cellular model for bridging the gap between genetic findings and disease biology. In this review, we first conceptualize the advances in understanding the disease polygenicity and convergence from the past decade of iPSC modeling of different types of genetic risk factors of neuropsychiatric disorders. We then discuss the major cell types and cellular phenotypes that are most relevant to neuropsychiatric disorders in iPSC modeling. Finally, we critically review the limitations of iPSC modeling of neuropsychiatric disorders and outline the need for implementing and developing novel methods to scale up the number of iPSC lines and disease risk variants in a systematic manner. Sufficiently scaled-up iPSC modeling and a better functional interpretation of genetic risk variants, in combination with cutting-edge CRISPR/Cas9 gene editing and single-cell multi-omics methods, will enable the field to identify the specific and convergent molecular and cellular phenotypes in precision for neuropsychiatric disorders.

Towards functional maps of non-coding variants in cancer

Large scale cancer genomic studies in patients have unveiled millions of non-coding variants. While a handful have been shown to drive cancer development, the vast majority have unknown function. This review describes the challenges of functionally annotating non-coding cancer variants and understanding how they contribute to cancer. We summarize recently developed high-throughput technologies to address these challenges. Finally, we outline future prospects for non-coding cancer genetics to help catalyze personalized cancer therapy.

Zinc finger nuclease-mediated gene editing in hematopoietic stem cells results in reactivation of fetal hemoglobin in sickle cell disease

BIVV003 is a gene-edited autologous cell therapy in clinical development for the potential treatment of sickle cell disease (SCD). Hematopoietic stem cells (HSC) are genetically modified with mRNA encoding zinc finger nucleases (ZFN) that target and disrupt a specific regulatory GATAA motif in the BCL11A erythroid enhancer to reactivate fetal hemoglobin (HbF). We characterized ZFN-edited HSC from healthy donors and donors with SCD. Results of preclinical studies show that ZFN-mediated editing is highly efficient, with enriched biallelic editing and high frequency of on-target indels, producing HSC capable of long-term multilineage engraftment in vivo, and express HbF in erythroid progeny. Interim results from the Phase 1/2 PRECIZN-1 study demonstrated that BIVV003 was well-tolerated in seven participants with SCD, of whom five of the six with more than 3 months of follow-up displayed increased total hemoglobin and HbF, and no severe vaso-occlusive crises. Our data suggest BIVV003 represents a compelling and novel cell therapy for the potential treatment of SCD.

In vivo dissection of the mouse tyrosine catabolic pathway with CRISPR-Cas9 identifies modifier genes affecting hereditary tyrosinemia type 1

Hereditary tyrosinemia type 1 is an autosomal recessive disorder caused by mutations (pathogenic variants) in fumarylacetoacetate hydrolase, an enzyme involved in tyrosine degradation. Its loss results in the accumulation of toxic metabolites that mainly affect the liver and kidneys and can lead to severe liver disease and liver cancer. Tyrosinemia type 1 has a global prevalence of approximately 1 in 100,000 births but can reach up to 1 in 1,500 births in some regions of Québec, Canada. Mutating functionally related "modifier' genes (i.e. genes that, when mutated, affect the phenotypic impacts of mutations in other genes) is an emerging strategy for treating human genetic diseases. In vivo somatic genome editing in animal models of these diseases is a powerful means to identify modifier genes and fuel treatment development. In this study, we demonstrate that mutating additional enzymes in the tyrosine catabolic pathway through liver-specific genome editing can relieve or worsen the phenotypic severity of a murine model of tyrosinemia type 1. Neonatal gene delivery using recombinant adeno-associated viral vectors expressing Staphylococcus aureus Cas9 under the control of a liver-specific promoter led to efficient gene disruption and metabolic rewiring of the pathway, with systemic effects that were distinct from the phenotypes observed in whole-body knockout models. Our work illustrates the value of using in vivo genome editing in model organisms to study the direct effects of combining pathological mutations with modifier gene mutations in isogenic settings.

Hydroxyurea reduces the levels of the fetal globin gene repressors ZBTB7A/LRF and BCL11A in erythroid cells in vitro

Objectives

Hydroxyurea (HU) is the most widely used therapy for adults and children with sickle cell disease (SCD). It is believed to act largely by inducing the transcription of fetal γ-globin genes to generate fetal hemoglobin (HbF), which inhibits the pathological polymerization of sickle hemoglobin (HbS). The mechanisms by which hydroxyurea elevates HbF are unclear. We explored the hypothesis that hydroxyurea induces HbF expression by inhibiting the expression of 2 γ-globin gene repressors, BCL11A and ZBTB7A (also known as LRF), which normally bind the γ-globin gene promoters to inhibit their expression after birth.

Methods

We treated immortalized murine erythroleukemia cells and normal human donor CD34+ hematopoietic stem and progenitor cell-derived erythroblasts with hydroxyurea and measured the effects on globin, BCL11A and ZBTB7A protein and mRNA expression.

Results

Treating murine erythroleukemia cells or human CD34+ hematopoietic stem and progenitor cell-derived erythroblasts with hydroxyurea reduced the protein levels of BCL11A and ZBTB7A compared to the vehicle-treated control. BCL11A mRNA levels were reduced in both cell types upon hydroxyurea treatment. However, ZBTB7A mRNA levels were only reduced in human CD34+ hematopoietic stem and progenitor cell-derived erythroblasts.

Conclusions

Hydroxyurea can act in erythroid cells to reduce the levels and activity of two direct fetal γ-globin transcriptional repressors with accompanying de-repression of the γ-globin genes and induction of HbF, which may explain the mechanism of action leading to amelioration of symptoms in SCD patients treated with this drug.

Gene Therapies for Sickle Cell Disease

Background: Sickle cell disease (SCD) is a prevalent autosomal recessive hemoglobinopathy affecting millions worldwide, particularly individuals of African ancestry. Sickle cell disease is a lifelong condition associated with a negative impact on quality of life and mortality, causing complications such as painful vaso-occlusive episodes, acute chest syndrome, stroke, long-term anemia, and end-organ damage. Currently, there are 4 U.S. Food and Drug Administration (FDA)-approved drugs, including hydroxyurea, l-glutamine, voxelotor, and crizanlizumab, which work to alleviate symptoms and prevent complications associated with SCD, albeit without addressing the underlying cause of SCD. Allogeneic hematopoietic stem cell transplant (HSCT) has shown promise as a curative approach to SCD but is limited by donor availability and associated complications. This paper aims to review the efficacy and safety of exagamglogene autotemcel and lovotibeglogene autotemcel for managing patients with SCD, including their place in therapy, cost, and accessibility in clinical care. Data Sources: The authors searched PubMed and Medline from 2017 to 2024, for primary literature on both exagamglogene autotemcel and lovotibeglogene autotemcel. Results: The authors identified relevant studies and summarized the data on the two gene therapies. Conclusion: Exagamglogene autotemcel and lovotibeglogene autotemcel are two management strategies that address the underlying cause of SCD and provide curative potential for patients with SCD.

Genome Editing Therapy for the Blood: Ex Vivo Success and In Vivo Prospects

Hematopoietic stem cells (HSCs) provide the body with a continuous supply of healthy, functional blood cells. In patients with hematopoietic malignancies, immunodeficiencies, lysosomal storage disorders, and hemoglobinopathies, therapeutic genome editing offers hope for corrective intervention, with even modest editing efficiencies likely to provide clinical benefit. Engineered white blood cells, such as T cells, can be applied therapeutically to address monogenic disorders of the immune system, HIV infection, or cancer. The versatility of CRISPR-based tools allows countless new medical interventions for diseases of the blood, and rapid ex vivo success has been demonstrated in hemoglobinopathies via transplantation of the patient's HSCs following genome editing in a laboratory setting. Here we review recent advances in therapeutic genome editing of HSCs and T cells, focusing on the progress in ex vivo contexts, the promise of improved access via in vivo delivery, as well as the ongoing preclinical efforts that may enable the transition from ex vivo to in vivo administration. We discuss the challenges, limitations, and future prospects of this rapidly developing field, which may one day establish CRISPR as the standard of care for some diseases affecting the blood.

Transcription factor networks disproportionately enrich for heritability of blood cell phenotypes

Most phenotype-associated genetic variants map to non-coding regulatory regions of the human genome. Moreover, variants associated with blood cell phenotypes are enriched in regulatory regions active during hematopoiesis. To systematically explore the nature of these regions, we developed a highly efficient strategy, Perturb-multiome, that makes it possible to simultaneously profile both chromatin accessibility and gene expression in single cells with CRISPR-mediated perturbation of a range of master transcription factors (TFs). This approach allowed us to examine the connection between TFs, accessible regions, and gene expression across the genome throughout hematopoietic differentiation. We discovered that variants within the TF-sensitive accessible chromatin regions, while representing less than 0.3% of the genome, show a ~100-fold enrichment in heritability across certain blood cell phenotypes; this enrichment is strikingly higher than for other accessible chromatin regions. Our approach facilitates large-scale mechanistic understanding of phenotype-associated genetic variants by connecting key cis-regulatory elements and their target genes within gene regulatory networks.

A comprehensive in silico investigation into the pathogenic SNPs in the RTEL1 gene and their biological consequences

The Regulator of Telomere Helicase 1 (RTEL1) gene encodes a critical DNA helicase intricately involved in the maintenance of telomeric structures and the preservation of genomic stability. Germline mutations in the RTEL1 gene have been clinically associated with Hoyeraal-Hreidarsson syndrome, a more severe version of Dyskeratosis Congenita. Although various research has sought to link RTEL1 mutations to specific disorders, no comprehensive investigation has yet been conducted on missense mutations. In this study, we attempted to investigate the functionally and structurally deleterious coding and non-coding SNPs of the RTEL1 gene using an in silico approach. Initially, out of 1392 nsSNPs, 43 nsSNPs were filtered out through ten web-based bioinformatics tools. With subsequent analysis using nine in silico tools, these 43 nsSNPs were further shortened to 11 most deleterious nsSNPs. Furthermore, analyses of mutated protein structures, evolutionary conservancy, surface accessibility, domains & PTM sites, cancer susceptibility, and interatomic interaction revealed the detrimental effect of these 11 nsSNPs on RTEL1 protein. An in-depth investigation through molecular docking with the DNA binding sequence demonstrated a striking change in the interaction pattern for F15L, M25V, and G706R mutant proteins, suggesting the more severe consequences of these mutations on protein structure and functionality. Among the non-coding variants, two had the highest likelihood of being regulatory variants, whereas one variant was predicted to affect the target region of a miRNA. Thus, this study lays the groundwork for extensive analysis of RTEL1 gene variants in the future, along with the advancement of precision medicine and other treatment modalities.

Therapeutic Gene Editing for Hemoglobinopathies

In the last ten years, a consistent number of clinical studies have evaluated different gene approaches for the treatment of patients with sickle cell disease (SCD) and transfusion-dependent β-thalassemia (TDT). Initial studies of gene therapy for hemoglobinopathies involved the use of lentiviral vectors to add functional copies of the gene encoding β-globin in defective CD34 cells; more recently, gene editing techniques have been used involving either CRISPR-Cas9, transcription activation-like effector protein nuclease, zinc finger nuclease, and base editing to either induce fetal hemoglobin production at therapeutic levels or to genetically repair the underlying molecular defect causing the disease. Here, we review recent gene editing studies that have started the development of a new era in the treatment of hemoglobinopathies and, in general, monoallelic hereditary diseases.

Interspecies regulatory landscapes and elements revealed by novel joint systematic integration of human and mouse blood cell epigenomes

Knowledge of locations and activities of cis-regulatory elements (CREs) is needed to decipher basic mechanisms of gene regulation and to understand the impact of genetic variants on complex traits. Previous studies identified candidate CREs (cCREs) using epigenetic features in one species, making comparisons difficult between species. In contrast, we conducted an interspecies study defining epigenetic states and identifying cCREs in blood cell types to generate regulatory maps that are comparable between species, using integrative modeling of eight epigenetic features jointly in human and mouse in our Validated Systematic Integration (VISION) Project. The resulting catalogs of cCREs are useful resources for further studies of gene regulation in blood cells, indicated by high overlap with known functional elements and strong enrichment for human genetic variants associated with blood cell phenotypes. The contribution of each epigenetic state in cCREs to gene regulation, inferred from a multivariate regression, was used to estimate epigenetic state regulatory potential (esRP) scores for each cCRE in each cell type, which were used to categorize dynamic changes in cCREs. Groups of cCREs displaying similar patterns of regulatory activity in human and mouse cell types, obtained by joint clustering on esRP scores, harbor distinctive transcription factor binding motifs that are similar between species. An interspecies comparison of cCREs revealed both conserved and species-specific patterns of epigenetic evolution. Finally, we show that comparisons of the epigenetic landscape between species can reveal elements with similar roles in regulation, even in the absence of genomic sequence alignment.

Scalable assessment of genome editing off-targets associated with genetic variants

Genome editing with RNA-guided DNA binding factors carries risk of off-target editing at homologous sequences. Genetic variants may introduce sequence changes that increase homology to a genome editing target, thereby increasing risk of off-target editing. Conventional methods to verify candidate off-targets rely on access to cells with genomic DNA carrying these sequences. However, for candidate off-targets associated with genetic variants, appropriate cells for experimental verification may not be available. Here we develop a method, Assessment By Stand-in Off-target LentiViral Ensemble with sequencing (ABSOLVE-seq), to integrate a set of candidate off-target sequences along with unique molecular identifiers (UMIs) in genomes of primary cells followed by clinically relevant gene editor delivery. Gene editing of dozens of candidate off-target sequences may be evaluated in a single experiment with high sensitivity, precision, and power. We provide an open-source pipeline to analyze sequencing data. This approach enables experimental assessment of the influence of human genetic diversity on specificity evaluation during gene editing therapy development.

Developing a pill to treat sickle cell disease

A newly identified epigenetic modifier increases fetal hemoglobin in preclinical studies.

Hidden secrets of the cancer genome: unlocking the impact of non-coding mutations in gene regulatory elements

Discoveries in the field of genomics have revealed that non-coding genomic regions are not merely "junk DNA", but rather comprise critical elements involved in gene expression. These gene regulatory elements (GREs) include enhancers, insulators, silencers, and gene promoters. Notably, new evidence shows how mutations within these regions substantially influence gene expression programs, especially in the context of cancer. Advances in high-throughput sequencing technologies have accelerated the identification of somatic and germline single nucleotide mutations in non-coding genomic regions. This review provides an overview of somatic and germline non-coding single nucleotide alterations affecting transcription factor binding sites in GREs, specifically involved in cancer biology. It also summarizes the technologies available for exploring GREs and the challenges associated with studying and characterizing non-coding single nucleotide mutations. Understanding the role of GRE alterations in cancer is essential for improving diagnostic and prognostic capabilities in the precision medicine era, leading to enhanced patient-centered clinical outcomes.