Inducible proteolytic inactivation of OPA1 mediated by the OMA1 protease in mammalian cells

A proteolytic cascade ensures that OMA1 cleaves and inactivates mitochondrial fusion protein OPA1 in times of stress, preventing damaged mitochondria from fusing with healthy organelles. (See also companion paper from Ehses et al. in this issue.

Generation of human control iPS cell line CHOPWT10 from healthy adult peripheral blood mononuclear cells

The CHOPWT10 iPS cell line was generated to be used as a control for applications such as in differentiation analyses to the three germ layers and derivative tissues. Peripheral blood mononuclear cells (PBMCs) obtained from a healthy adult male were reprogrammed using the non-integrating Sendai virus expressing Oct3/4, Sox2, c-Myc, and Klf4

Generation of a human Juvenile myelomonocytic leukemia iPSC line, CHOPi001-A, with a mutation in CBL.

Juvenile myelomonocytic leukemia (JMML) is a rare myeloproliferative disorder of early childhood characterized by expansion of clonal myelomonocytic cells and hyperactive Ras/MAPK signaling. The disorder is caused by somatic and/or germline mutations in genes involved in the Ras/MAPK and JAK/STAT signaling pathways, including CBL. Here we describe the generation of an iPSC line with a homozygous CBL c.1111T->C (Y371H) mutation, designated CHOPJMML1854

Generation of a human Juvenile myelomonocytic leukemia iPSC line, CHOPi001-A, with a mutation in CBL

Juvenile myelomonocytic leukemia (JMML) is a rare myeloproliferative disorder of early childhood characterized by expansion of clonal myelomonocytic cells and hyperactive Ras/MAPK signaling. The disorder is caused by somatic and/or germline mutations in genes involved in the Ras/MAPK and JAK/STAT signaling pathways, including CBL. Here we describe the generation of an iPSC line with a homozygous CBL c.1111T->C (Y371H) mutation, designated CHOPJMML1854

Mutation-specific signaling profiles and kinase inhibitor sensitivities of juvenile myelomonocytic leukemia revealed by induced pluripotent stem cells.

Juvenile myelomonocytic leukemia (JMML) is an uncommon myeloproliferative neoplasm driven by Ras pathway mutations and hyperactive Ras/MAPK signaling. Outcomes for many children with JMML remain dismal with current standard-of-care cytoreductive chemotherapy and hematopoietic stem cell transplantation. We used patient-derived induced pluripotent stem cells (iPSCs) to characterize the signaling profiles and potential therapeutic vulnerabilities of PTPN11-mutant and CBL-mutant JMML. We assessed whether MEK, JAK, and PI3K/mTOR kinase inhibitors (i) could inhibit myeloproliferation and aberrant signaling in iPSC-derived hematopoietic progenitors with PTPN11 E76K or CBL Y371H mutations. We detected constitutive Ras/MAPK and PI3K/mTOR signaling in PTPN11 and CBL iPSC-derived myeloid cells. Activated signaling and growth of PTPN11 iPSCs were preferentially inhibited in vitro by the MEKi PD0325901 and trametinib. Conversely, JAK/STAT signaling was selectively activated in CBL iPSCs and abrogated by the JAKi momelotinib and ruxolitinib. The PI3Kδi idelalisib and mTORi rapamycin inhibited signaling and myeloproliferation in both PTPN11 and CBL iPSCs. These findings demonstrate differential sensitivity of PTPN11 iPSCs to MEKi and of CBL iPSCs to JAKi, but similar sensitivity to PI3Ki and mTORi. Clinical investigation of mutation-specific kinase inhibitor therapies in children with JMML may be warranted

The Novel Tail-anchored Membrane Protein Mff Controls Mitochondrial and Peroxisomal Fission in Mammalian Cells

Few components of the mitochondrial fission machinery are known, even though mitochondrial fission is a complex process of vital importance for cell growth and survival. Here, we describe a novel protein that controls mitochondrial fission. This protein was identified in a small interfering RNA (siRNA) screen using Drosophila cells. The human homologue of this protein was named Mitochondrial fission factor (Mff). Mitochondria of cells transfected with Mff siRNA form a closed network similar to the mitochondrial networks formed when cells are transfected with siRNA for two established fission proteins, Drp1 and Fis1. Like Drp1 and Fis1 siRNA, Mff siRNA also inhibits fission induced by loss of mitochondrial membrane potential, it delays cytochrome c release from mitochondria and further progression of apoptosis, and it inhibits peroxisomal fission. Mff and Fis1 are both tail anchored in the mitochondrial outer membrane, but other parts of these proteins are very different and they exist in separate 200-kDa complexes, suggesting that they play different roles in the fission process. We conclude that Mff is a novel component of a conserved membrane fission pathway used for constitutive and induced fission of mitochondria and peroxisomes