MERTK mutation update in inherited retinal diseases

MER tyrosine kinase (MERTK) encodes a surface receptor localized at the apical membrane of the retinal pigment epithelium. It plays a critical role in photoreceptor outer segment internalization prior to phagocytosis. Mutations in MERTK have been associated with severe autosomal recessive retinal dystrophies in the RCS rat and in humans. We present here a comprehensive review of all reported MERTK disease causing variants with the associated phenotype. In addition, we provide further data and insights of a large cohort of 1,195 inherited retinal dystrophies (IRD) index cases applying state‐of‐the‐art genotyping techniques and summarize current knowledge. A total of 79 variants have now been identified underlying rod‐cone dystrophy and cone‐rod dystrophy including 11 novel variants reported here. The mutation spectrum in MERTK includes 33 missense, 12 nonsense, 12 splice defects, 12 small deletions, 2 small insertion–deletions, 3 small duplications, and 2 exonic and 3 gross deletions. Altogether, mutations in MERTK account for ～2% of IRD cases with a severe retinal phenotype. These data are important for current and future therapeutic trials including gene replacement therapy or cell‐based therapy.     

Distribution of Anopheles daciae and other Anopheles maculipennis complex species in Serbia

Parasitology Research - Malaria is one of the most severe health problems facing the world today. Until the mid-twentieth century, Europe was an endemic area of malaria, with the Balkan countries...     

Future Directions for Research on Early Intervention for Young Children at Risk for Social Anxiety

Anxiety disorders are common among young children, with earlier onset typically associated with greater severity and persistence. A stable behaviorally inhibited (BI) temperament and subsequent shyness and social withdrawal (SW) place children at increased risk of developing anxiety disorders, particularly social anxiety. In this Future Directions article, we briefly review developmental and clinical research and theory that point to parenting and peer interactions as key moderators of both the stability of BI/SW and risk for later anxiety, and we describe existing interventions that address early BI/SW and/or anxiety disorders in young children. We recommend that future research on early intervention to disrupt the trajectory of anxiety in children at risk (a) be informed by both developmental science and clinical research, (b) incorporate multiple levels of analysis (including both individual and contextual factors), (c) examine mediators that move us closer to understanding how and why treatments work, (d) be developed with the end goal of dissemination, (e) examine moderators of outcome toward the goal of treatment efficiency, (f) consider transdiagnostic or modular approaches, (g) integrate technology, and (h) consider cultural norms regarding BI/SW/anxiety and parenting.     

Allogeneic Stem Cell Transplantation from HLA-Mismatched Donors for Pediatric Patients with Acute Lymphoblastic Leukemia Treated According to the 2003 BFM and 2007 International BFM Studies: Impact of Disease Risk on Outcomes

Allogeneic hematopoietic stem cell transplantation (HSCT) is beneficial for pediatric patients with relapsed or (very) high-risk acute lymphoblastic leukemia (ALL) in remission. A total of 1115 consecutive patients were included in the ALL SCT 2003 BFM study and the ALL SCT 2007 I-BFM study and were stratified according to relapse risk (standard versus high versus very high risk of relapse) and donor type (matched sibling versus matched donor versus mismatched donor). A total of 148 patients (60% boys; median age, 8.7 years; B cell precursor ALL, 75%) were transplanted from mismatched donors, which was defined as either less than 9/10 HLA-compatible donors or less than 5/6 unrelated cord blood after myeloablative conditioning regimen (total body irradiation based, 67%) for high relapse risk (HRR; n?=?42) or very HRR (VHRR) disease (n?=?106). The stem cell source was either bone marrow (n?=?31), unmanipulated peripheral stem cells (n?=?28), T cell ex vivo depleted peripheral stem cells (n?=?59), or cord blood (n?=?25). The median follow-up was 5.1 years. The 4-year rates of overall survival (OS) and event-free survival were 56%?±?4% and 52%?±?4%, respectively, for the entire cohort. Patients transplanted from mismatched donors for HRR disease obtained remarkable 4-year OS and event-free survival values of 82%?±?6% and 80%?±?6%, respectively, whereas VHRR patients obtained values of 45%?±?5% and 42%?±?5% (P?<?.001), respectively. The cumulative incidence of relapse was 29%?±?4% and that of nonrelapse mortality 19%?±?3%. The cumulative incidence of limited and extensive chronic graft-versus-host disease was 13%?±?3% and 15%?±?4%, respectively, among the 120 patients living beyond day 100. Multivariate analysis showed that OS was lower for transplanted VHRR patients (P?=?.002; hazard ratio [HR], 3.62; 95% confidence interval [CI], 1.60 to 8.20) and for patients beyond second complete remission (CR2) versus first complete remission (P?<?.001; HR, 3.68; 95% CI, 1.79 to 7.56); relapse occurred more frequently in patients with VHRR disease (P?=?.026; HR, 3.30; 95% CI, 1.16 to 9.60) and for those beyond CR2 (P?=?.005; HR, 4.16; 95% CI, 1.52 to 10.59). Nonrelapse mortality was not significantly higher for cytomegalovirus-positive recipients receiving cytomegalovirus-negative grafts (P?=?.12; HR, 1.96; 95% CI, .84 to 4.58). HSCT with a mismatched donor is feasible in pediatric ALL patients but leads to inferior results compared with HSCT with better matched donors, at least for patients transplanted for VHRR disease. The results are strongly affected by disease status. The main cause of treatment failure is still relapse, highlighting the urgent need for interventional strategies after HSCT for patients with residual leukemia before and/or after transplantation     

CHILD syndrome: A modified pathogenesis‐targeted therapeutic approach

Congenital Hemidysplasia with Ichthyosiform nevus and Limb Defects (CHILD syndrome) is a rare X‐linked dominant genodermatosis caused by mutations in the NAD(P) dependent steroid dehydrogenase‐like protein gene. Its defect leads to accumulation of toxic metabolic intermediates upstream from the pathway block and to the deficiency of bulk cholesterol, probably leading to altered keratinocyte membrane function, resulting in the phenotype seen in CHILD syndrome. Symptomatic treatment using emollients and retinoids to reduce scaling has long been used until recently, whereby new therapeutic means based on the pathogenesis‐targeted therapy have been developed. We subsequently chose to use the same pathogenesis‐based therapy using a 2% cholesterol and 2% lovastatin cream with or without glycolic acid in two of our patients. Improvement in CHILD skin lesions was seen as early as 4 weeks after initiation. The addition of glycolic acid helped improve the penetrance of the cholesterol and lovastatin cream into the thick waxy scales. Our study confirms the efficacy of the pathogenesis‐targeted therapy and introduces the possibility of modifying its formula by adding glycolic acid in order to improve the treatment.

     

E1 of α-ketoglutarate dehydrogenase defends Mycobacterium tuberculosis against glutamate anaplerosis and nitroxidative stress

Enzymes of central carbon metabolism (CCM) in Mycobacterium tuberculosis (Mtb) make an important contribution to the pathogen’s virulence. Evidence is emerging that some of these enzymes are not simply playing the metabolic roles for which they are annotated, but can protect the pathogen via additional functions. Here, we found that deficiency of 2-hydroxy-3-oxoadipate synthase (HOAS), the E1 component of the α-ketoglutarate (α-KG) dehydrogenase complex (KDHC), did not lead to general metabolic perturbation or growth impairment of Mtb, but only to the specific inability to cope with glutamate anaplerosis and nitroxidative stress. In the former role, HOAS acts to prevent accumulation of aldehydes, including growth-inhibitory succinate semialdehyde (SSA). In the latter role, HOAS can participate in an alternative four-component peroxidase system, HOAS/dihydrolipoyl acetyl transferase (DlaT)/alkylhydroperoxide reductase colorless subunit gene (ahpC)-neighboring subunit (AhpD)/AhpC, using α-KG as a previously undescribed source of electrons for reductase action. Thus, instead of a canonical role in CCM, the E1 component of Mtb’s KDHC serves key roles in situational defense that contribute to its requirement for virulence in the host. We also show that pyruvate decarboxylase (AceE), the E1 component of pyruvate dehydrogenase (PDHC), can participate in AceE/DlaT/AhpD/AhpC, using pyruvate as a source of electrons for reductase action. Identification of these systems leads us to suggest that Mtb can recruit components of its CCM for reactive nitrogen defense using central carbon metabolites.The bacterium Mycobacterium tuberculosis (Mtb), which causes tuberculosis, has plagued humanity since antiquity (1), is estimated to infect one-third of the population today, and is the leading cause of death by a bacterium. This success as a pathogen reflects Mtb’s metabolic plasticity and resistance to host immunity (2, 3). Recent evidence suggests that certain enzymes of central carbon metabolism (CCM) can mediate both of these facets of Mtb’s adaptation to the host (4–8). Here, we demonstrate that Rv1248c, recently named 2-hydroxy-3-oxoadipate synthase (HOAS) (9), is one such enzyme.Rv1248c was first annotated as the thiamin diphosphate (ThDP)-dependent E1 component (SucA) of a canonical α-ketoglutarate (α-KG) dehydrogenase complex (KDHC) that produces succinyl CoA (SucCoA) via oxidative decarboxylation of α-KG with concomitant transfer of the resulting succinyl group to CoA (10). Classically, KDHC, composed of three enzymes, joins the oxidative and reductive half-cycles of the TCA cycle (SI Appendix, Fig. S1). The TCA cycle generates high-energy phosphate bonds and biosynthetic precursors of amino acids, nucleotides, and fatty acids (11). However, KDHC activity was not detected in Mtb lysates, and the gene product annotated as the lipoamide-bearing E2 component [Rv2215, dihydrolipoyl succinyl transferase (SucB)] functions as the E2 component dihydrolipoyl acetyl transferase (DlaT) of the pyruvate dehydrogenase complex (PDHC) (5, 12, 13). The Mtb genome does not encode another SucB (12), and KDHC activity could not be demonstrated with purified recombinant Rv1248c plus DlaT and E3 [lipoamide dehydrogenase (Lpd)] in a manner similar to cognate proteins from other actinomycetes (14). Rv1248c by itself produces succinate semialdehyde (SSA) from nonoxidative decarboxylation of α-KG in vitro, and Mtb’s succinate semialdehyde dehydrogenases (SSADHs) can generate succinate from SSA, completing a modified TCA cycle (13). Subsequently, activity-based metabolomic profiling revealed yet another function of Rv1248c that predominated over SSA production: decarboxylation of α-KG, followed by carboligation with glyoxylate to form 2-hydroxy-3-oxoadipate (HOA). Thus, Rv1248c was renamed HOAS (9). Decarboxylation of α-KG is the first step in all three reactions. The Mycobacterium smegmatis α-ketoglutarate decarboxylase (MsKGD) homolog was found to catalyze all three reactions in vitro, with augmentation of catalysis by acetyl CoA (AcCoA)-mediated allosteric modulation (15), whereas Mtb HOAS showed a kinetic preference for the HOAS pathway in vitro (16).HOAS activity is regulated in Mtb by glycogen accumulation regulator A (GarA), whose activity is controlled, in turn, by Ser/Thr kinases PknG and PknB (SI Appendix, Fig. S1B). GarA also regulates glutamate dehydrogenase (GDH) and glutamate synthase/glutamine oxoglutarate aminotransferase (17). Coregulation of these three enzymes by GarA calls attention to the contribution of HOAS to Mtb’s metabolism of glutamate. Glutamate serves as an anaplerotic substrate entering the TCA cycle as α-KG and is also a key intermediate in nitrogen assimilation and metabolism (18, 19).Despite extensive studies, the physiological function of HOAS in Mtb and its contribution to virulence remain unknown. Here, we brought genetics, metabolomics, enzymology, and mouse models of infection to bear on that question, using the hoas deletion mutant in Mtb and the deletion mutant complemented in three ways: with the WT allele, with an allele with a point mutation that abrogates catalysis, or with an allele with a point mutation that is insensitive to allosteric regulation by AcCoA. In standard culture conditions, Δhoas showed no defect in growth or changes in levels of CCM metabolites, arguing against Mtb’s reliance on the conventional function of KDHC. However, situational stresses revealed striking phenotypes in Δhoas, indicative of a defensive role of HOAS against products arising from metabolism of glutamate and against reactive nitrogen intermediates (RNIs). Mechanistic analysis of the latter phenotype revealed a previously undescribed route to antioxidant defense mediated by substrates and enzymes of CCM.