A quantum coherent spin in hexagonal boron nitride at ambient conditions.

Solid-state spin-photon interfaces that combine single-photon generation and long-lived spin coherence with scalable device integration-ideally under ambient conditions-hold great promise for the implementation of quantum networks and sensors. Despite rapid progress reported across several candidate systems, those possessing quantum coherent single spins at room temperature remain extremely rare. Here we report quantum coherent control under ambient conditions of a single-photon-emitting defect spin in a layered van der Waals material, namely, hexagonal boron nitride. We identify that the carbon-related defect has a spin-triplet electronic ground-state manifold. We demonstrate that the spin coherence is predominantly governed by coupling to only a few proximal nuclei and is prolonged by decoupling protocols. Our results serve to introduce a new platform to realize a room-temperature spin qubit coupled to a multiqubit quantum register or quantum sensor with nanoscale sample proximity.

Coherence protection of spin qubits in hexagonal boron nitride.

Spin defects in foils of hexagonal boron nitride are an attractive platform for magnetic field imaging, since the probe can be placed in close proximity to the target. However, as a III-V material the electron spin coherence is limited by the nuclear spin environment, with spin echo coherence times of ∽100 ns at room temperature accessible magnetic fields. We use a strong continuous microwave drive with a modulation in order to stabilize a Rabi oscillation, extending the coherence time up to ∽ 4µs, which is close to the 10 µs electron spin lifetime in our sample. We then define a protected qubit basis, and show full control of the protected qubit. The coherence times of a superposition of the protected qubit can be as high as 0.8 µs. This work establishes that boron vacancies in hexagonal boron nitride can have electron spin coherence times that are competitive with typical nitrogen vacancy centres in small nanodiamonds under ambient conditions.

Excited State Spectroscopy of Boron Vacancy Defects in Hexagonal Boron Nitride Using Time-Resolved Optically Detected Magnetic Resonance.

We report optically detected magnetic resonance (ODMR) measurements of an ensemble of spin-1 negatively charged boron vacancies in hexagonal boron nitride. The photoluminescence decay rates are spin-dependent, with intersystem crossing rates of 1.02 ns-1 and 2.03 ns-1 for the mS = 0 and mS = ±1 states, respectively. Time gating the photoluminescence enhances the ODMR contrast by discriminating between different decay rates. This is particularly effective for detecting the spin of the optically excited state, where a zero-field splitting of |DES| = 2.09 GHz is measured. The magnetic field dependence of the photoluminescence exhibits dips corresponding to the ground (GSLAC) and excited-state (ESLAC) anticrossings and additional anticrossings due to coupling with nearby spin-1/2 parasitic impurities. Comparison to a model suggests that the anticrossings are mediated by the interaction with nuclear spins and allows an estimate of the ratio of the singlet to triplet spin-dependent relaxation rates of κ0/κ1 = 0.34.

Stimulated Emission Depletion Spectroscopy of Color Centers in Hexagonal Boron Nitride.

We demonstrate the use of Stimulated Emission Depletion (STED) spectroscopy to map the electron-optical-phonon sideband of the ground state of the radiative transition of color centers in hexagonal boron nitride emitting at 2.0-2.2 eV, with in-plane linear polarization. The measurements are compared to photoluminescence of excitation (PLE) spectra that maps the electron-optical-phonon sideband of the excited state. The main qualitative difference is a red-shift in the longitudinal optical phonon peak associated with E 1u symmetry at the zone center. We compare our results to theoretical work on different defect species in hBN and find they are consistent with a carbon-based defect.

Optical Gating of Photoluminescence from Color Centers in Hexagonal Boron Nitride.

We report on multicolor excitation experiments with color centers in hexagonal boron nitride at cryogenic temperatures. We demonstrate controllable optical switching between bright and dark states of color centers emitting around 2 eV. Resonant, or quasi-resonant, excitation of photoluminescence also pumps the color center, via a two-photon process, into a dark state, where it becomes trapped. Repumping back into the bright state has a step-like spectrum with a defect-dependent threshold between 2.25 and 2.6 eV. This behavior is consistent with photoionization and charging between optically bright and dark states of the defect. Furthermore, a second zero phonon line, detuned by +0.4 eV, is observed in absorption with orthogonal polarization to the emission, evidencing an additional energy level in the color center.

Matriptase-2 deficiency protects from obesity by modulating iron homeostasis.

Alterations in iron status have frequently been associated with obesity and other metabolic disorders. The hormone hepcidin stands out as a key regulator in the maintenance of iron homeostasis by controlling the main iron exporter, ferroportin. Here we demonstrate that the deficiency in the hepcidin repressor matriptase-2 (Tmprss6) protects from high-fat diet-induced obesity. Tmprss6 -/- mice show a significant decrease in body fat, improved glucose tolerance and insulin sensitivity, and are protected against hepatic steatosis. Moreover, these mice exhibit a significant increase in fat lipolysis, consistent with their dramatic reduction in adiposity. Rescue experiments that block hepcidin up-regulation and restore iron levels in Tmprss6-/- mice via anti-hemojuvelin (HJV) therapy, revert the obesity-resistant phenotype of Tmprss6-/- mice. Overall, this study describes a role for matritpase-2 and hepcidin in obesity and highlights the relevance of iron regulation in the control of adipose tissue function.

Inkjet-Printed Nanocavities on a Photonic Crystal Template.

The last decade has witnessed the rapid development of inkjet printing as an attractive bottom-up microfabrication technology due to its simplicity and potentially low cost. The wealth of printable materials has been key to its widespread adoption in organic optoelectronics and biotechnology. However, its implementation in nanophotonics has so far been limited by the coarse resolution of conventional inkjet-printing methods. In addition, the low refractive index of organic materials prevents the use of "soft-photonics" in applications where strong light confinement is required. This study introduces a hybrid approach for creating and fine tuning high-Q nanocavities, involving the local deposition of an organic ink on the surface of an inorganic 2D photonic crystal template using a commercially available high-resolution inkjet printer. The controllability of this approach is demonstrated by tuning the resonance of the printed nanocavities by the number of printer passes and by the fabrication of photonic crystal molecules with controllable splitting. The versatility of this method is evidenced by the realization of nanocavities obtained by surface deposition on a blank photonic crystal. A new method for a free-form, high-density, material-independent, and high-throughput fabrication technique is thus established with a manifold of opportunities in photonic applications.

Mutations in CHD2 cause defective association with active chromatin in chronic lymphocytic leukemia.

Great progress has recently been achieved in the understanding of the genomic alterations driving chronic lymphocytic leukemia (CLL). Nevertheless, the specific molecular mechanisms governing chromatin remodeling in CLL are unknown. Here we report the genetic and functional characterization of somatic mutations affecting the chromatin remodeler CHD2, one of the most frequently mutated genes in CLL (5.3%) and in monoclonal B lymphocytosis (MBL, 7%), a B-cell expansion that can evolve to CLL. Most of the mutations affecting CHD2, identified by whole-exome sequencing of 456 CLL and 43 MBL patients, are either truncating or affect conserved residues in functional domains, thus supporting a putative role for CHD2 as a tumor suppressor gene. CHD2 mutants show altered nuclear distribution, and a chromodomain helicase DNA binding protein 2 (CHD2) mutant affected in its DNA-binding domain exhibits defective association with active chromatin. Clinicobiological analyses show that most CLL patients carrying CHD2 mutations also present mutated immunoglobulin heavy chain variable region genes (IGHVs), being the most frequently mutated gene in this prognostic subgroup. This is the first study providing functional evidence supporting CHD2 as a cancer driver and opens the way to further studies of the role of this chromatin remodeler in CLL.

A critical role for murine transferrin receptor 2 in erythropoiesis during iron restriction.

Effective erythropoiesis requires an appropriate supply of iron and mechanisms regulating iron homeostasis and erythropoiesis are intrinsically linked. Iron dysregulation, typified by iron-deficiency anaemia and iron overload, is common in many clinical conditions and impacts the health of up to 30% of the world's population. The proteins transmembrane protease, serine 6 (TMPRSS6; also termed matriptase-2), HFE and transferrin receptor 2 (TFR2) play important and opposing roles in systemic iron homeostasis, by regulating expression of the iron regulatory hormone hepcidin. We have performed a systematic analysis of mice deficient in these three proteins and show that TMPRSS6 predominates over HFE and TFR2 in hepcidin regulation. The phenotype of mice lacking TMPRSS6 and TFR2 is characterized by severe anaemia and extramedullary haematopoiesis in the spleen. Stress erythropoiesis in these mice results in increased expression of the newly identified erythroid iron regulator erythroferrone, which does not appear to overcome the hepcidin overproduction mediated by loss of TMPRSS6. Extended analysis reveals that TFR2 plays an important role in erythroid cells, where it is involved in terminal erythroblast differentiation and the regulation of erythropoietin. In conclusion, we have identified an essential role for TFR2 in erythropoiesis that may provide new targets for the treatment of anaemia.

Nonsense mutations in the shelterin complex genes ACD and TERF2IP in familial melanoma.

BACKGROUND: The shelterin complex protects chromosomal ends by regulating how the telomerase complex interacts with telomeres. Following the recent finding in familial melanoma of inactivating germline mutations in POT1, encoding a member of the shelterin complex, we searched for mutations in the other five components of the shelterin complex in melanoma families. METHODS: Next-generation sequencing techniques were used to screen 510 melanoma families (with unknown genetic etiology) and control cohorts for mutations in shelterin complex encoding genes: ACD, TERF2IP, TERF1, TERF2, and TINF 2. Maximum likelihood and LOD [logarithm (base 10) of odds] analyses were used. Mutation clustering was assessed with χ(2) and Fisher's exact tests. P values under .05 were considered statistically significant (one-tailed with Yates' correction). RESULTS: Six families had mutations in ACD and four families carried TERF2IP variants, which included nonsense mutations in both genes (p.Q320X and p.R364X, respectively) and point mutations that cosegregated with melanoma. Of five distinct mutations in ACD, four clustered in the POT1 binding domain, including p.Q320X. This clustering of novel mutations in the POT1 binding domain of ACD was statistically higher (P = .005) in melanoma probands compared with population control individuals (n = 6785), as were all novel and rare variants in both ACD (P = .040) and TERF2IP (P = .022). Families carrying ACD and TERF2IP mutations were also enriched with other cancer types, suggesting that these variants also predispose to a broader spectrum of cancers than just melanoma. Novel mutations were also observed in TERF1, TERF2, and TINF2, but these were not convincingly associated with melanoma. CONCLUSIONS: Our findings add to the growing support for telomere dysregulation as a key process associated with melanoma susceptibility.

Matriptase-2 is essential for hepcidin repression during fetal life and postnatal development in mice to maintain iron homeostasis.

Iron is an essential element required for development and survival of all living organisms. In fetuses, maternofetal iron transfer across the placenta is essential for growth and development. In neonates, efficient intestinal iron absorption is required to scavenge as much iron as possible from the low-iron-content milk. During these periods, efficient iron mobilization is ensured by the downregulation of the iron regulatory hormone hepcidin by as-yet uncharacterized molecular mechanisms. Here we demonstrate that the recently described hepcidin repressor-the serine protease matriptase-2 (encoded by Tmprss6)-is responsible for this repression throughout development, with its deficiency leading to increased hepcidin levels triggering iron deficiency and anemia starting in utero. This result might have implications for a better understanding of iron homeostasis during early development in iron-refractory iron deficiency anemia patients, who present with microcytic anemia caused by hyperhepcidinemia, and of questions about the role of matriptase-2 in human neonates.

POT1 loss-of-function variants predispose to familial melanoma.

Deleterious germline variants in CDKN2A account for around 40% of familial melanoma cases, and rare variants in CDK4, BRCA2, BAP1 and the promoter of TERT have also been linked to the disease. Here we set out to identify new high-penetrance susceptibility genes by sequencing 184 melanoma cases from 105 pedigrees recruited in the UK, The Netherlands and Australia that were negative for variants in known predisposition genes. We identified families where melanoma cosegregates with loss-of-function variants in the protection of telomeres 1 gene (POT1), with a proportion of family members presenting with an early age of onset and multiple primary tumors. We show that these variants either affect POT1 mRNA splicing or alter key residues in the highly conserved oligonucleotide/oligosaccharide-binding (OB) domains of POT1, disrupting protein-telomere binding and leading to increased telomere length. These findings suggest that POT1 variants predispose to melanoma formation via a direct effect on telomeres.

Cell-cell adhesion genes CTNNA2 and CTNNA3 are tumour suppressors frequently mutated in laryngeal carcinomas.

Laryngeal squamous cell carcinoma is a frequent and significant cause of morbidity and mortality. Here we explore the biological basis of this aggressive tumour, and identify two cell-cell adhesion genes as recurrently mutated in this malignancy. We first perform exome sequencing of four laryngeal carcinomas and their matched normal tissues. Among the 569 genes found to present somatic mutations, and based on their recurrence or functional relevance in cancer, we select 40 for further validation in 86 additional laryngeal carcinomas. We detect frequent mutations (14 of 90, 15%) in CTNNA2 and CTNNA3-encoding α-catenins. Functional studies reveal an increase in the migration and invasive ability of head and neck squamous cell carcinoma cells producing mutated forms of CTNNA2 and CTNNA3 or in cells where both α-catenins are silenced. Analysis of the clinical relevance of these mutations demonstrates that they are associated with poor prognosis. We conclude that CTNNA2 and CTNNA3 are tumour suppressor genes frequently mutated in laryngeal carcinomas.

New roles for OMA1 metalloprotease: From mitochondrial proteostasis to metabolic homeostasis.

The mitochondrial quality control system is essential for the preservation and regulation of mitochondrial function. This system is formed by a complex machinery that controls and maintains protein function and regulates mitochondrial morphology through a coordinated system of continual fusion and fission events. Impairments in the mitochondrial quality control system through either mutation or deficiency in any of its components, can lead to mitochondrial dysfunction. However, the physiological consequences of these deficiencies remain unknown in most cases. Here, we briefly review the role of the OPA1-OMA1 system in mitochondrial biology, and summarize our recent report on the generation and phenotypic characterization of a model deficient in OMA1, an ATP-independent mitochondrial metalloprotease that participates in mitochondrial quality control. Interestingly, Oma1-deficient mice display an obesity phenotype, characterized by hepatic steatosis, decrease in energy expenditure and defective thermogenic regulation. In addition, our study has provided in vivo evidence of OMA1 function as a mitochondrial quality control protease, inactivating OPA1 under stress conditions and inhibiting mitochondrial fusion. Further, we have demonstrated the essential role of the OMA1-OPA1 system for brown adipose function and how this system regulates metabolic homeostasis in mice.

The genomic landscape of chronic lymphocytic leukemia: clinical implications.

A precise understanding of the genomic and epigenomic features of chronic lymphocytic leukemia (CLL) may benefit the study of the disease's staging and treatment. While recent reports have shed some light on these aspects, several challenges need to be addressed before translating this research into clinical practice. Thus, even the best candidate driver genes display low mutational rates compared to other tumors. This means that a large percentage of cases do not display clear tumor-driving point mutations, or show candidate driving point mutations with no obvious biochemical relationship to the more frequently mutated genes. This genomic landscape probably reflects either an unknown underlying biochemical mechanism playing a key role in CLL or multiple biochemical pathways independently driving the development of this tumor. The elucidation of either scenario will have important consequences on the clinical management of CLL. Herein, we review the recent advances in the definition of the genomic landscape of CLL and the ongoing research to characterize the underlying biochemical events that drive this disease.

POT1 mutations cause telomere dysfunction in chronic lymphocytic leukemia.

Chronic lymphocytic leukemia (CLL) is the most frequent leukemia in adults. We have analyzed exome sequencing data from 127 individuals with CLL and Sanger sequencing data from 214 additional affected individuals, identifying recurrent somatic mutations in POT1 (encoding protection of telomeres 1) in 3.5% of the cases, with the frequency reaching 9% when only individuals without IGHV@ mutations were considered. POT1 encodes a component of the shelterin complex and is the first member of this telomeric structure found to be mutated in human cancer. Somatic mutation of POT1 primarily occurs in gene regions encoding the two oligonucleotide-/oligosaccharide-binding (OB) folds and affects key residues required to bind telomeric DNA. POT1-mutated CLL cells have numerous telomeric and chromosomal abnormalities that suggest that POT1 mutations favor the acquisition of the malignant features of CLL cells. The identification of POT1 as a new frequently mutated gene in CLL may facilitate novel approaches for the clinical management of this disease.

Functional analysis of sucrase-isomaltase mutations from chronic lymphocytic leukemia patients.

Next-generation sequencing techniques have emerged as powerful tools for the understanding of cancer genomes. In recent years, whole-exome and whole-genome sequencing strategies have enabled the annotation of a comprehensive mutation landscape of chronic lymphocytic leukemia (CLL), the most frequent leukemia in western countries. Several recurrently mutated genes have been identified, with a subset being validated as neoplastic drivers. Still, a main challenge remains for the differentiation between driver and passenger mutations among candidates as well as for the functional description of the newly discovered leukemogenic genes that could be utilized for personalized anti-tumor strategies. In this scenario, we have identified the metabolic enzyme sucrase-isomaltase (SI) as one of the most frequently mutated genes in a cohort of 105 CLL patients. Here, we demonstrate that these SI mutations result in loss of enzyme function by preventing the biosynthesis of catalytically competent SI at the cell surface. Transcriptome analyses of RNA from CLL patients with SI loss-of-function mutations have uncovered gene expression patterns that depict ample metabolic reprogramming, pinpointing SI as a putative player in the cancer-associated metabolic switch. These results highlight SI as a relevant target for clinical evaluation in future CLL studies.

Next-generation sequencing reveals the secrets of the chronic lymphocytic leukemia genome.

The study of the detailed molecular history of cancer development is one of the most promising techniques to understand and fight this diverse and prevalent disease. Unfortunately, this history is as diverse as cancer itself. Therefore, even with next-generation sequencing techniques, it is not easy to distinguish significant (driver) from random (passenger) events. The International Cancer Genome Consortium (ICGC) was formed to solve this fundamental issue by coordinating the sequencing of samples from 50 different cancer types and/or sub-types that are of clinical and societal importance. The contribution of Spain in this consortium has been focused on chronic lymphocytic leukemia (CLL). This approach has unveiled new and unexpected events in the development of CLL. In this review, we introduce the approaches utilized by the consortium for the study of the CLL genome and discuss the recent results and future perspectives of this work.

Nuclear lamina defects cause ATM-dependent NF-κB activation and link accelerated aging to a systemic inflammatory response.

Alterations in the architecture and dynamics of the nuclear lamina have a causal role in normal and accelerated aging through both cell-autonomous and systemic mechanisms. However, the precise nature of the molecular cues involved in this process remains incompletely defined. Here we report that the accumulation of prelamin A isoforms at the nuclear lamina triggers an ATM- and NEMO-dependent signaling pathway that leads to NF-κB activation and secretion of high levels of proinflammatory cytokines in two different mouse models of accelerated aging (Zmpste24(-/-) and Lmna(G609G/G609G) mice). Causal involvement of NF-κB in accelerated aging was demonstrated by the fact that both genetic and pharmacological inhibition of NF-κB signaling prevents age-associated features in these animal models, significantly extending their longevity. Our findings provide in vivo proof of principle for the feasibility of pharmacological modulation of the NF-κB pathway to slow down the progression of physiological and pathological aging.