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The activated JAK2/STAT pathway is characteristic of myeloproliferative neoplasms (MPNs). The pleckstrin 2 (PLEK2) signalosome is downstream of the JAK2/STAT5 pathway and plays an important role in MPN development. The detailed molecular composition of this signalosome is unclear. Here, we reveal peptidylprolyl isomerase-like 2 (PPIL2) as a critical component of the complex in regulating human and murine erythropoiesis. PPIL2 was a direct target of STAT5 and was upregulated in patients with MPN and in a Jak2V617F MPN mouse model. Mechanistically, PPIL2 interacted with and catalyzed p53 polyubiquitination and proteasome-mediated degradation to promote cell growth. Ppil2 deficiency, or inhibition by cyclosporin A, led to a marked upregulation of p53 in vivo and ameliorated myeloproliferative phenotypes in Jak2V617F mice. Cyclosporin A also markedly reduced JAK2-mutated erythroid and myeloid proliferation in an induced pluripotent stem cell-derived human bone marrow organoid model. Our findings reveal PPIL2 as a critical component of the PLEK2 signalosome in driving MPN pathogenesis through negative regulation of p53, thus providing a target and opportunity for drug repurposing using cyclosporin A to treat MPNs.

Deleterious germline DDX41 variants constitute the most common inherited predisposition disorder linked to myeloid neoplasms (MNs), yet their role in MNs remains unclear. Here we show that DDX41 is essential for erythropoiesis but dispensable for other hematopoietic lineages. Ddx41 knockout in early erythropoiesis is embryonically lethal, while knockout in late-stage terminal erythropoiesis allows mice to survive with normal blood counts. DDX41 deficiency induces a significant upregulation of G-quadruplexes (G4), which co-distribute with DDX41 on the erythroid genome. DDX41 directly binds to and resolves G4, which is significantly compromised in MN-associated DDX41 mutants. G4 accumulation induces erythroid genome instability, ribosomal defects, and p53 upregulation. However, p53 deficiency does not rescue the embryonic death of Ddx41 hematopoietic-specific knockout mice. In parallel, genome instability also activates the cGas-Sting pathway, impairing survival, as cGas deficiency rescues the lethality of hematopoietic-specific Ddx41 knockout mice. This is supported by data from a DDX41-mutated MN patient and human iPSC-derived bone marrow organoids. Our study establishes DDX41 as a G4 resolvase, essential for erythroid genome stability and suppressing the cGAS-STING pathway. Germline DDX41 mutations are linked to myeloid neoplasms, but their roles in the disease is unclear. Here, the authors show that DDX41 resolves G-quadruplex structures to maintain erythroid genome stability and prevent cGAS-mediated cell death. These functions are lost in disease-associated variants.

Myeloproliferative neoplasms (MPNs) are characterized by the activated JAK2/STAT pathway. Pleckstrin-2 (Plek2) is a downstream target of the JAK2/STAT5 pathway and is overexpressed in patients with MPNs. We previously revealed that Plek2 plays critical roles in the pathogenesis of JAK2-mutated MPNs. The nonessential roles of Plek2 under physiologic conditions make it an ideal target for MPN therapy. Here, we identified first-in-class Plek2 inhibitors through an in silico high-throughput screening approach and cell-based assays, followed by the synthesis of analogs. Plek2-specific small-molecule inhibitors showed potent inhibitory effects on cell proliferation. Mechanistically, Plek2 interacts with and enhances the activity of Akt through the recruitment of downstream effector proteins. The Plek2-signaling complex also includes Hsp72, which protects Akt from degradation. These functions were blocked by Plek2 inhibitors via their direct binding to the Plek2 dishevelled, Egl-10 and pleckstrin (DEP) domain. The role of Plek2 in activating Akt signaling was further confirmed in vivo using a hematopoietic-specific Pten-knockout mouse model. We next tested Plek2 inhibitors alone or in combination with an Akt inhibitor in various MPN mouse models, which showed significant therapeutic efficacies similar to that seen with the genetic depletion of Plek2. The Plek2 inhibitor was also effective in reducing proliferation of CD34-positive cells from MPN patients. Our studies reveal a Plek2/Akt complex that drives cell proliferation and can be targeted by a class of antiproliferative compounds for MPN therapy.

mDia formin proteins regulate the dynamics and organization of the cytoskeleton through their linear actin nucleation and polymerization activities. We previously showed that mDia1 deficiency leads to aberrant innate immune activation and induces myelodysplasia in a mouse model, and mDia2 regulates enucleation and cytokinesis of erythroblasts and the engraftment of hematopoietic stem and progenitor cells (HSPCs). However, whether and how mDia formins interplay and regulate hematopoiesis under physiological and stress conditions remains unknown. Here, we found that both mDia1 and mDia2 are required for HSPC regeneration under stress, such as serial plating, aging, and reconstitution after myeloid ablation. We showed that mDia1 and mDia2 form hetero-oligomers through the interactions between mDia1 GBD-DID and mDia2 DAD domains. Double knockout of mDia1 and mDia2 in hematopoietic cells synergistically impaired the filamentous actin network and serum response factor-involved transcriptional signaling, which led to declined HSPCs, severe anemia, and significant mortality in neonates and newborn mice. Our data demonstrate the potential roles of mDia hetero-oligomerization and their non-rodent functions in the regulation of HSPCs activity and orchestration of hematopoiesis.

Summary MicroRNAs (miRNAs) are 20‐24 nucleotides (nt) small RNAs functioning in eukaryotes. The length and sequence of miRNAs are not only related to the biogenesis of miRNAs but are also important for downstream physiological processes like ta‐siRNA production. To investigate these roles, it is informative to create small mutations within mature miRNA sequences. We used both TALENs (transcription activator‐like effector nucleases) and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR‐associated protein 9 (Cas9) to introduce heritable base pair mutations in mature miRNA sequences. For rice, TALEN constructs were built targeting five different mature miRNA sequences and yielding heritable mutations. Among the resulting mutants, mir390 mutant showed a severe defect in the shoot apical meristem (SAM), a shootless phenotype, which could be rescued by the wild‐type MIR390. Small RNA sequencing showed the two base pair deletion in mir390 substantially interfered with miR390 biogenesis. In Arabidopsis, CRISPR/Cas9‐mediated editing of the miR160* strand confirmed that the asymmetric structure of miRNA is not a necessary determinant for secondary siRNA production. CRISPR/Cas9 with double‐guide RNAs successfully generated mir160a null mutants with fragment deletions, at a higher efficiency than a single‐guide RNA. The difference between the phenotypic severity of miR160a mutants in Col‐0 versus Ler backgrounds highlights a diverged role for miR160a in different ecotypes. Overall, we demonstrated that TALENs and CRISPR/Cas9 are both effective in modifying miRNA precursor structure, disrupting miRNA processing and generating miRNA null mutant plants.

The activated JAK2/STAT pathway is characteristic of myeloproliferative neoplasms (MPNs). Pleckstrin-2 (PLEK2) signalosome is downstream of the JAK2/STAT5 pathway and plays an important role in MPN development. The detailed molecular composition of this signalosome is unclear. Here, we revealed peptidylprolyl isomerase-like 2 (PPIL2) as a critical component of the complex in regulating human and murine erythropoiesis. PPIL2 was a direct target of STAT5 and was upregulated in MPN patients and a Jak2V617F MPN mouse model. Mechanistically, PPIL2 interacted with and catalyzed p53 polyubiquitination and proteasome-mediated degradation to promote cell growth. Ppil2 deficiency, or inhibition by cyclosporin A, led to a marked upregulation of p53 in vivo and ameliorated myeloproliferative phenotypes in Jak2V617F mice. Cyclosporin A also markedly reduced JAK2 mutated erythroid and myeloid proliferation in an induced pluripotent stem cell-derived human bone marrow organoid model. Our findings revealed PPIL2 as a critical component of the PLEK2 signalosome in driving MPN pathogenesis through negatively regulating p53, thus providing a target and an opportunity for drug repurposing by using cyclosporin A to treat MPNs.The activated JAK2/STAT pathway is characteristic of myeloproliferative neoplasms (MPNs). Pleckstrin-2 (PLEK2) signalosome is downstream of the JAK2/STAT5 pathway and plays an important role in MPN development. The detailed molecular composition of this signalosome is unclear. Here, we revealed peptidylprolyl isomerase-like 2 (PPIL2) as a critical component of the complex in regulating human and murine erythropoiesis. PPIL2 was a direct target of STAT5 and was upregulated in MPN patients and a Jak2V617F MPN mouse model. Mechanistically, PPIL2 interacted with and catalyzed p53 polyubiquitination and proteasome-mediated degradation to promote cell growth. Ppil2 deficiency, or inhibition by cyclosporin A, led to a marked upregulation of p53 in vivo and ameliorated myeloproliferative phenotypes in Jak2V617F mice. Cyclosporin A also markedly reduced JAK2 mutated erythroid and myeloid proliferation in an induced pluripotent stem cell-derived human bone marrow organoid model. Our findings revealed PPIL2 as a critical component of the PLEK2 signalosome in driving MPN pathogenesis through negatively regulating p53, thus providing a target and an opportunity for drug repurposing by using cyclosporin A to treat MPNs.

Engineered TALENs (Transcription activator-like effector nucleases) and CRISPR/Cas (clustered regularly interspaced short palindromic repeats/ CRISPR-associated proteins) as genetic toolbox have been widely used in basic and applied biological researches. Here we use TALENs and CRISPR/Cas9 to target miRNA genes and Argonaute (AGO) genes for gene knockouts and study their functions in rice. We successfully knocked out 5 miRNA genes and recovered phenotypic mutant plants using TALENs. The efficient assembling of TALENs constructs and their versatility provided us a very useful toolbox to study miRNA gene functions. In addition, we used CRISPR/Cas9 system to target AGO genes in rice. We successfully generated single-gene knockouts for all 19 AGO genes and several multi-gene mutants of gene clades through multiplex targeting of CRISPR system in rice. Some mutants were characterized at molecular and morphological levels. The results demonstrate TALEN and CRISPR/Cas9 mediated gene editing are robust genetic tools that enable functional genomics.

How to deliver therapy into brain remains a headache-causing question for hundreds of years. Even with modern gene therapy, the delivery through blood brain barrier is still challenging. Here, I reviewed recent development in gene therapies, especially CRISPR/Cas9, and their delivery method into brain. AAV9 and exosomes are introduced as the two most promising tools. By comparing the two systems, some advantages and disadvantages of each system were talked. I also raised several possible new directions in gene delivery research.

[...]it has been scolded for years that some talented scientists behave abusively in the lab. [...]Dr. He has considered the off-target effects of CRISPR/Cas9 system, but the single-cell sequencing technology used to exclude off-target effects, which can only cover 80% of the whole genome, was not sufficient to ensure safety 5. [...]the truncated C-C chemokine receptor 5 (CCR5) in Nana (-4, +1) is completely different from the CCR5A32 discovered in European, leaving potential risks of creating a toxic protein and unwanted effects that are impossible to foresee. [...]besides the fact that Lulu's genes cannot possibly give her protection against HIV, researchers have already developed multiple strategies to protect newborn from vertical transmission 6. [...]in Dr. He's research, it is the twins' father infected with HIV.