DNMT3A/TET2/ASXL1 Mutations are an Age-independent Thrombotic Risk Factor in Polycythemia Vera Patients: An Observational Study.

BACKGROUND: Polycythemia vera (PV) patients are classified as high or low thrombotic risk based on age and prior history of thrombosis. Despite adherence to treatment recommendations, vascular events remain frequent, leading us to question whether thrombotic risk stratification could be improved. We previously reported an association between thrombotic events and mutations in DTA genes (DNMT3A, TET2, and ASXL1). The objective of this study was to confirm this observation in a larger series of PV patients. METHODS: PV patients with a minimum follow-up of 3 years were recruited from 8 European centers. Medical history was searched for thrombotic event recorded at any time and next-generation sequencing carried out with a myeloid panel. Multivariable logistic regression evaluated the impact of variables on thrombotic risk. Kaplan-Meier thrombosis-free survival curves were compared by the log rank test. Associations in the total cohort were confirmed in a case-control study to exclude selection bias. RESULTS: Of the 136 patients recruited, 74 (56.1%) had a thrombotic event, with an incidence density of 2.83/100 person-years. In multivariable analysis, DTA mutation was a risk factor for thrombotic event, being predictive for shorter thrombosis-free survival in the whole cohort (p = 0.007), as well as in low-risk patients (p = 0.039) and older patients (p = 0.009), but not for patients with a prediagnostic event. A gender- and age-matched case-control study confirmed the increased risk of thrombotic event for PV patients with a DTA mutation. CONCLUSION: Our results support the use of molecular testing at diagnosis to help predict which PV patients are at higher risk of developing thrombosis.

Shedding light on myopia by studying complete congenital stationary night blindness.

Myopia is the most common eye disorder, caused by heterogeneous genetic and environmental factors. Rare progressive and stationary inherited retinal disorders are often associated with high myopia. Genes implicated in myopia encode proteins involved in a variety of biological processes including eye morphogenesis, extracellular matrix organization, visual perception, circadian rhythms, and retinal signaling. Differentially expressed genes (DEGs) identified in animal models mimicking myopia are helpful in suggesting candidate genes implicated in human myopia. Complete congenital stationary night blindness (cCSNB) in humans and animal models represents an ON-bipolar cell signal transmission defect and is also associated with high myopia. Thus, it represents also an interesting model to identify myopia-related genes, as well as disease mechanisms. While the origin of night blindness is molecularly well established, further research is needed to elucidate the mechanisms of myopia development in subjects with cCSNB. Using whole transcriptome analysis on three different mouse models of cCSNB (in Gpr179-/-, Lrit3-/- and Grm6-/-), we identified novel actors of the retinal signaling cascade, which are also novel candidate genes for myopia. Meta-analysis of our transcriptomic data with published transcriptomic databases and genome-wide association studies from myopia cases led us to propose new biological/cellular processes/mechanisms potentially at the origin of myopia in cCSNB subjects. The results provide a foundation to guide the development of pharmacological myopia therapies.

Can the Gene Expression Profile of Patients with Acute Myeloid Leukemia Predict Complete Remission Following Induction Therapy?

Recent advances in sequencing technologies and genomics have led to the development of several targeted therapies such as BCL2 and Bromodomain and extra-terminal (BET) protein inhibitors for a more personalized treatment of patients with acute myeloid leukemia (AML), yet the majority of patients still receive standard induction chemotherapy. The molecular profiles of patients who are likely to respond to induction therapy and novel directed therapies remain to be determined. The expression of AML-related genes that are targeted by novel therapies such as BCL2 and BRD4, as well as functionally related genes and associated epigenetic modulators (TET2, EZH2, ASXL1, MYC) were analyzed in a series of 176 consecutive AML patients at multiple points during the disease course - diagnosis (Dx), post-induction (PI), complete remission (CR) and relapse (RL) - and their relationship with clinical variables and outcome investigated. Higher TET2 expression was observed PI and at CR compared to Dx, with significantly superior TET2 expression after induction therapy in the group of patients who reached CR compared to those who did not. Thus, the upregulation of TET2 at PI may be a marker of CR in AML patients. On the other hand, cells with high levels of MYC and BCL2 may be vulnerable to BRD4 inhibition.

Predictive indicators of successful tyrosine kinase inhibitor discontinuation in patients with chronic myeloid leukemia.

Clinical trials have demonstrated that some patients with chronic myeloid leukemia (CML) treated for several years with tyrosine kinase inhibitors (TKIs) who have maintained a molecular response can successfully discontinue treatment without relapsing. Treatment free remission (TFR) can be reached by approximately 50% of patients who discontinue. Despite having similar levels of deep molecular response and an identical duration of treatment, the factors that influence the successful discontinuation of CML patients remain to be determined. In this review we will explore the factors identified to date that can help predict whether a patient will successfully achieve TFR. We will also discuss the need for the identification of predictive biomarkers associated with a high probability of achieving TFR for the future personalized identification of patients who are suitable for the discontinuation of TKI treatment.

Neurogenetic asymmetries in the catshark developing habenulae: mechanistic and evolutionary implications.

Analysis of the establishment of epithalamic asymmetry in two non-conventional model organisms, a cartilaginous fish and a lamprey, has suggested that an essential role of Nodal signalling, likely to be ancestral in vertebrates, may have been largely lost in zebrafish. In order to decipher the cellular mechanisms underlying this divergence, we have characterised neurogenetic asymmetries during habenular development in the catshark Scyliorhinus canicula and addressed the mechanism involved in this process. As in zebrafish, neuronal differentiation starts earlier on the left side in the catshark habenulae, suggesting the conservation of a temporal regulation of neurogenesis. At later stages, marked, Alk4/5/7 dependent, size asymmetries having no clear counterparts in zebrafish also develop in neural progenitor territories, with a larger size of the proliferative, pseudostratified neuroepithelium, in the right habenula relative to the left one, but a higher cell number on the left of a more lateral, later formed population of neural progenitors. These data show that mechanisms resulting in an asymmetric, preferential maintenance of neural progenitors act both in the left and the right habenulae, on different cell populations. Such mechanisms may provide a substrate for quantitative variations accounting for the variability in size and laterality of habenular asymmetries across vertebrates.

Identification of Radial Glia Progenitors in the Developing and Adult Retina of Sharks.

Neural stem cells give rise to transient progenitors termed neuroepithelial cells (NECs) and radial glial cells (RGCs). RGCs represent the major source of neurons, glia and adult stem cells in several regions of the central nervous system (CNS). RGCs are mostly transient in mammals, but they are widely maintained in the adult CNS of fishes, where they continue to be morphologically similar to RGCs in the mammalian brain and fulfill similar roles as progenitors and guide for migrating neurons. The retina of fishes offers an exceptional model to approach the study of adult neurogenesis because of the presence of constitutive proliferation from the ciliary marginal zone (CMZ), containing NECs, and from adult glial cells with radial morphology (the Müller glia). However, the cellular hierarchies and precise contribution of different types of progenitors to adult neurogenesis remain unsolved. We have analyzed the transition from NECs to RGCs and RGC differentiation in the retina of the cartilaginous fish Scyliorhinus canicula, which offers a particularly good spatial and temporal frame to investigate this process. We have characterized progenitor and adult RGCs by immunohistochemical detection of glial markers as glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS). We have compared the emergence and localization of glial markers with that of proliferating cell nuclear antigen (PCNA, a proliferation maker) and Doublecortin (DCX, which increases at early stages of neuronal differentiation). During retinal development, GFAP-immunoreactive NECs located in the most peripheral CMZ (CMZp) codistribute with DCX-immunonegative cells. GFAP-immunoreactive RGCs and Müller cells are located in successive more central parts of the retina and codistribute with DCX- and DCX/GS-immunoreactive cells, respectively. The same types of progenitors are found in juveniles, suggesting that the contribution of the CMZ to adult neurogenesis implies a transition through the radial glia (RG) state.

Doublecortin is widely expressed in the developing and adult retina of sharks.

Doublecortin (DCX) is a microtubule-associated protein that has been considered a marker for neuronal precursors and young migrating neurons during the development of the central nervous system and in adult neurogenic niches. The retina of fishes represents an accessible, continuously growing and highly structured (layered) part of the central nervous system and, therefore, offers an exceptional model to extend our knowledge on the possible role of DCX in promoting neurogenesis and migration to appropriate layers. We have analyzed the distribution of DCX in the embryonic and postembryonic retina of a small shark, the lesser spotted dogfish Scyliorhinus canicula, by means of immunohistochemistry. We investigated the relationship between DCX expression and the neurogenic state of DCX-labeled cells by exploring its co-localization with the proliferation marker PCNA (proliferating cell nuclear antigen) and the marker of neuronal differentiation HuC/D. Since radially migrating neurons use radial glial fibers as substrate, we explored the possible correlation between DCX expression and cell migration along radial glia by comparing its expression with that of the glial marker GFAP (glial fibrillary acidic protein). Additionally, we characterized DCX-expressing cells by double immunocytochemistry using antibodies against Calbindin (a marker for mature bipolar and horizontal cells in this species) and Pax6, which has been proposed as a regulator of cell proliferation, cell differentiation, and neuron diversification in the neural retina of sharks. Strong DCX immunoreactivity was observed in immature cells and cell processes, at a time when retinal cells were not yet organized into different laminae. DCX was also found in subsets of mature ganglion, amacrine, bipolar and horizontal cells long after they had exited the cell cycle, a pattern that was maintained in juveniles and adults. Our results on DCX expression in the retina are compatible with a role for DCX in cell migration within the immature retina, and in dynamic neuronal plasticity in the mature retina. We also provide evidence of DCX expression in discrete cells in the retinal pigment epithelium of prehatching embryos and juveniles, which suggest that retinal pigmented epithelial cells in sharks, as in mammals, have an intrinsic capacity to proliferate and differentiate into cells with neural identity.