Gerd A. Blobel

Reactivating the fetal globin genes HBG1 and HBG2 in adult erythroid cells represents a validated therapeutic approach for hemoglobinopathies. Central mediators of the fetal-to-adult hemoglobin transition include the direct transcriptional HBG1/2 repressors BCL11A, LRF, and NFIA/X. Limited-scale screens have expanded the regulatory circuity surrounding fetal globin silencing, but systematic genome-wide dissection of such pathways is lacking. We used a 2-tiered genetic screening strategy, a novel CRISPR-Cas12a–based screening platform followed by a domain-focused CRISPR-Cas9 screen, to interrogate all known human protein-coding genes for their impact on HBG1/2 regulation and erythroid cellular fitness, generating a comprehensive resource for the field. Among the top new hits was protein phosphatase 2A (PP2A) phosphatase activator (PTPA), an activator of the serine-threonine phosphatase PP2A whose loss elevates HBG1/2 levels while preserving erythroid differentiation. Phenotypic rescue experiments revealed that PTPA silences HBG1/2 expression primarily by regulating BCL11A expression. To our knowledge, this study represents the most comprehensive CRISPR dissection of HBG regulation to date, highlighting the power of Cas12a-based genome-scale screening for uncovering disease-relevant pathways.

Polycomb repressive complexes PRC1 and PRC2 regulate diverse developmental processes, including the fetal-to-adult switch in hemoglobin production, a process whose reversal is a goal for the treatment of sickle cell disease and β-thalassemia. PRC inhibitors show promise for various disorders, but use is limited because of pleiotropic PRC activities. We explored whether fetal hemoglobin (HbF) can be reactivated in adult erythroid cells by selective perturbations of PRC1 or PRC2 components without complete loss of PRC function. A high-density CRISPR-Cas9 mutagenesis screen identified a region in the EZH2 subunit where Cas9 induced exon 14 skipping (EZH2Δ14). EZH2Δ14, which lacks a portion of the CXC domain, relieves HbF repression while largely maintaining cellular fitness. EZH2Δ14 retains H3K27 methylation and repression of a PRC target gene subset. Experiments in cells derived from mice bearing human β-globin genes confirm that pathways mediating EZH2 control of HbF expression can function in a mouse model of HBG switching. These findings demonstrate that partial disruption of PRC can yield selective phenotypes, highlighting the therapeutic potential of targeting non-enzymatic domains within chromatin-modifying complexes. Key Points: CRISPR-Cas9 screen across PRC1 and a saturating mutagenesis screen of PRC2 found the EZH2 CXC domain a desirable target for HbF induction the EZH2-CXC domain leads to exon 14 exclusion, resulting in de-repression of HbF but maintenance of cell fitness.

NIPBL promotes chromatin loop extrusion by the cohesin complex until it stalls at convergently oriented CTCF sites, forming structural loops. While a large fraction of loops connecting cis-regulatory elements (CREs) can be maintained in cohesin-depleted cells, whether the loop extrusion process contributes to the de novo establishment of CRE loops remains unclear. To address this question, we characterized the formation of structural and CRE loops in NIPBL-depleted cells during the mitosis-to-G1-phase transition. Structural loop formation was impaired proportionally to loop length. Computational modeling supports these observations, suggesting that NIPBL promotes both cohesin loading and extrusion. Notably, most CRE loops, regardless of length, were established normally upon NIPBL degradation. While a subset of contacts among weak CREs were formed with delayed kinetics in NIPBL-depleted cells, generally gene activation was only mildly impaired. Collectively, our findings suggest that postmitotic establishment of regulatory contacts and gene transcription can occur independently of chromatin loop extrusion.

USP6 mRNA triggers immunostimulatory effects in diverse cancer types

IVT USP6 mRNA recapitulates immunostimulatory effects

Kaplan Meier of Additional Cancers

Cytotoxix Effects of USP6 mRNA via IFN-TRAIL

Immune markers in co-cultured PBMCs

USP6 mRNA triggers immunostimulatory effects in head and neck cancer