SUMMARY Chromatin organization and dynamics are integral to global gene transcription. Histone modification influences chromatin status and gene expression. PTEN plays multiple roles in tumor suppression, development and metabolism. Here we report on the interplay of PTEN, histone H1 and chromatin. We show that loss of PTEN leads to dissociation of histone H1 from chromatin and decondensation of chromatin. PTEN deletion also results in elevation of histone H4 acetylation at lysine 16, an epigenetic marker for chromatin activation. We found that PTEN and histone H1 physically interact through their C-terminal domains. Disruption of the PTEN C-terminus promotes the chromatin association of MOF acetyltransferase and induces H4K16 acetylation. Hyperacetylation of H4K16 impairs the association of PTEN with histone H1, which constitutes regulatory feedback that may deteriorate chromatin stability. Our results demonstrate that PTEN controls chromatin condensation, thus influencing gene expression. We propose that PTEN regulates global gene transcription profiling through histones and chromatin remodeling.

Faithful DNA replication is a cornerstone of genomic integrity. PTEN plays multiple roles in genome protection and tumor suppression. Here we report on the importance of PTEN in DNA replication. PTEN depletion leads to impairment of replication progression and stalled fork recovery, indicating an elevation of endogenous replication stress. Exogenous replication inhibition aggravates replication-originated DNA lesions without inducing S-phase arrest in cells lacking PTEN, representing replication stress tolerance. Our analysis reveals the physical association of PTEN with DNA replication forks and PTEN-dependent recruitment of Rad51. PTEN deletion results in Rad51 dissociation from replication forks. Stalled replication forks in Pten null cells can be reactivated by ectopic Rad51 or PTEN, the latter facilitating chromatin loading of Rad51. These data highlight the interplay of PTEN with Rad51 in promoting stalled fork restart. We propose that loss of PTEN may initiate a replication stress cascade that progressively deteriorates through the cell cycle.

SUMMARY Tumor suppressor PTEN controls genomic stability and inhibits tumorigenesis. The N-terminal phosphatase domain of PTEN antagonizes the PI3K/AKT pathway, but its C-terminal function is less defined. Here we describe a knock-in mouse model of a nonsense mutation that results in deletion of the entire Pten C-terminal region, referred to as PtenΔC. Mice heterozygous for PtenΔC develop multiple spontaneous tumors, including cancers and B cell lymphoma. Heterozygous deletion of the Pten C-terminal domain also causes genomic instability and common fragile site rearrangement. We found that Pten C terminal disruption induces p53 and its downstream targets. Simultaneous depletion of p53 promotes metastasis without influencing initiation of tumors, suggesting that p53 mainly suppresses tumor progression. Our data highlight the essential role of the PTEN C-terminus in the maintenance of genomic stability and suppression of tumorigenesis.

The effect of cooling field HFC on the exchange bias field HEB in a spontaneous lamellar ferromagnetic/antiferromagnetic phase separated Y0.2Ca0.8MnO3 has been studied. It is found that with increasing HFC from 1to6T the value of HEB decreases by 37% at 2K and is inversely proportional to the ferromagnetic layer thickness tFM. This suggests that the tuning of HEB by HFC in Y0.2Ca0.8MnO3 arises from the variation of tFM with HFC. This phenomenon is essentially different from other types of magnetic tunings.

PTEN is a powerful tumor suppressor that antagonizes the cytoplasmic PI3K-AKT pathway and suppresses cellular proliferation. PTEN also plays a role in the maintenance of genomic stability in the nucleus. Here we report that PTEN facilitates DNA decatenation and controls a decatenation checkpoint. Catenations of DNA formed during replication are decatenated by DNA topoisomerase II (TOP2), and this process is actively monitored by a decatenation checkpoint in G2 phase. We found that PTEN deficient cells form ultra-fine bridges (UFBs) during anaphase and these bridges are generated as a result of insufficient decatenation. We show that PTEN is physically associated with a decatenation enzyme TOP2A and that PTEN influences its stability through OTUD3 deubiquitinase. In the presence of PTEN, ubiquitination of TOP2A is inhibited by OTUD3. Deletion or deficiency of PTEN leads to down regulation of TOP2A, dysfunction of the decatenation checkpoint and incomplete DNA decatenation in G2 and M phases. We propose that PTEN controls DNA decatenation to maintain genomic stability and integrity.

Rapid advances in genetics are linking mutations on genes to diseases at an exponential rate, yet characterizing the gene-mutation-cell-behavior relationships essential for precision medicine remains a daunting task. More than 350 mutations on BRaf are associated with various tumors, and ∼40 mutations are associated with the neurodevelopmental disorder cardio-facio-cutaneous syndrome (CFC). We developed a fast cost-effective lentivirus-based rapid gene replacement method to interrogate the physiopathology of BRaf and ∼50 disease-linked BRaf mutants, including all CFC-linked mutants. Analysis of simultaneous multiple patch-clamp recordings from 6068 pairs of rat neurons with validation in additional mouse and human neurons and multiple learning tests from 1486 rats identified BRaf as the key missing signaling effector in the common synaptic NMDA-R-CaMKII-SynGap-RasBRaf-MEK-ERK transduction cascade. Moreover, the analysis creates the original big data unveiling three general features of BRaf signaling. This study establishes the first efficient procedure that permits large-scale functional analysis of human disease-linked mutations essential for precision medicine.

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AND INTRODUCTIONMagnetic control of neuronal activity offers many obvious advantages over electric, optogenetic and chemogenetic manipulations. A recent series of highly visible papers reported the development of magnetic actuators (i.e., Magneto, MagR and αGFP−TRPV1/GFP−ferritin) that appeared to be effective in controlling neuronal firing 1-3 , yet their action mechanisms seem to conflict with the principles of physics 4 . We found that neurons expressing Magneto, MagR and αGFP−TRPV1/GFP−ferritin did not respond to magnetic stimuli with any membrane depolarization (let alone action potential firing), although these neurons frequently generated spontaneous action potentials. Because the previous study did not establish the precise temporal correlation between magnetic stimuli and action potentials in recorded neurons 1-3 , the reported magnetically-evoked action potentials are likely to represent mismatched spontaneous firings. RESULTSTo examine the membrane surface incorporation of Magneto, we transfected 293T cells with the P2A-linked wild type TRPV4 (the primogenitor of Magneto2.0), ferritin (the other key element of Magneto2.0) and mCherry, aka TRPV4-P2A-ferritin-P2A-mCherry, or the P2A-linked Magneto2.0 and mCherry, aka Magneto-P2A-mCherry.We then made simultaneous measurements of the magnetic stimulation-and agonist-evoked responses in control non-expressing and TRPV4-P2A-ferritin-P2A-mCherry or Magneto-P2A-mCherry expressing cell pairs (Fig 1a). To determine the precise timing of applied magnetic field, we used an LED illuminator and a photodetector to monitor the exact position of magnets mounted on a Luigs-Neumann JUNIOR COMPACT manipulator. Delivering a K&J N42 neodymium 1/16" block magnet to the position 1,000 μm away from recorded cells generated a 64.5-mT magnetic field (Fig S1). As expected, delivery and withdrawal of the magnet did not induce any current in control and TRPV4-P2A-ferritin-P2A-mCherry expressing cells (Fig 1b-c). In contrast, puff application of TRPV4 agonist, GSK1016790A (GSK101), reliably elicited inward currents in TRPV4-P2A-ferritin-P2A-mCherry expressing cells, but not control non-expressing cells (Fig 1b-c). Additional analysis revealed that GSK101-elicited currents in TRPV4-P2A-ferritin-P2A-mCherry expressing cells had the IV relationship typical of TRPV4, and the currents were blocked by a TRPV4 antagonist GSK205 (Fig S2a-b), indicating TRPV4-specific currents 5 . Surprisingly, neither the magnetic stimuli nor GSK101 induced any significant current in control and