PPAR-gamma agonist pioglitazone recovers mitochondrial quality control in fibroblasts from PITRM1-deficient patients

Introduction: Biallelic variants in PITRM1 are associated with a slowly progressive syndrome characterized by intellectual disability, spinocerebellar ataxia, cognitive decline and psychosis. The pitrilysin metallopeptidase 1 (PITRM1) is a mitochondrial matrix enzyme, which digests diverse oligopeptides, including the mitochondrial targeting sequences (MTS) that are cleaved from proteins imported across the inner mitochondrial membrane by the mitochondrial processing peptidase (MPP). Mitochondrial peptidases also play a role in the maturation of Frataxin, the protein affected in Friedreich’s ataxia. Recent studies in yeast indicated that the mitochondrial matrix protease Ste23, which is a homologue of the human insulin-degrading enzyme (IDE), cooperates with Cym1 (homologue of PITRM1) to ensure the proper functioning of the preprotein processing machinery. In humans, IDE could be upregulated by Peroxisome Proliferator-Activated Receptor Gamma (PPARG) agonists.Methods: We investigated preprotein processing, mitochondrial membrane potential and MTS degradation in control and patients’, and we evaluated the pharmacological effect of the PPARG agonist Pioglitazone on mitochondrial proteostasis.Results: We discovered that PITRM1 dysfunction results in the accumulation of MTS, leading to the disruption and dissipation of the mitochondrial membrane potential. This triggers a feedback inhibition of MPP activity, consequently impairing the processing and maturation of Frataxin. Furthermore, we found that the pharmacological stimulation of PPARG by Pioglitazone upregulates IDE and also PITRM1 protein levels restoring the presequence processing machinery and improving Frataxin maturation and mitochondrial function.Discussion: Our findings provide mechanistic insights and suggest a potential pharmacological strategy for this rare neurodegenerative mitochondrial disease

Adsorptive uptake of water by semisolid secondary organic aerosols

Aerosol climate effects are intimately tied to interactions with water. Here we combine hygroscopicity measurements with direct observations about the phase of secondary organic aerosol (SOA) particles to show that water uptake by slightly oxygenated SOA is an adsorption-dominated process under subsaturated conditions, where low solubility inhibits water uptake until the humidity is high enough for dissolution to occur. This reconciles reported discrepancies in previous hygroscopicity closure studies. We demonstrate that the difference in SOA hygroscopic behavior in subsaturated and supersaturated conditions can lead to an effect up to about 30% in the direct aerosol forcinghighlighting the need to implement correct descriptions of these processes in atmospheric models. Obtaining closure across the water saturation point is therefore a critical issue for accurate climate modeling.Peer reviewe

Single Nucleotide Polymorphisms That Increase Expression of the Guanosine Triphosphatase RAC1 Are Associated With Ulcerative Colitis

BACKGROUND & AIMS: RAC1 is a GTPase that has an evolutionarily conserved role in coordinating immune defenses, from plants to mammals. Chronic inflammatory bowel diseases (IBD) are associated with dysregulation of immune defenses. We studied the role of RAC1 in IBD using human genetic and functional studies and animal models of colitis. METHODS: We used a candidate gene approach to HapMap-Tag single nucleotide polymorphisms (SNPs) in a discovery cohort; findings were confirmed in 2 additional cohorts. RAC1 mRNA expression was examined from peripheral blood cells of patients. Colitis was induced in mice with conditional disruption of Rac1 in phagocytes by administration of dextran sulphate sodium (DSS). RESULTS: We observed a genetic association between RAC1 with ulcerative colitis (UC) in a discovery cohort, 2 independent replication cohorts, and in combined analysis for the SNPs rs10951982 (Pcombined UC = 3.3 × 10–8, odds ratio [OR]=1.43 [1.26–1.63]) and rs4720672 (Pcombined UC=4.7 × 10–6, OR=1.36 [1.19–1.58]). Patients with IBD who had the rs10951982 risk allele had increased expression of RAC1, compared to those without this allele. Conditional disruption of Rac1 in macrophage and neutrophils of mice protected them against DSS-induced colitis. CONCLUSION: Studies of human tissue samples and knockout mice demonstrated a role for the GTPase RAC1 in the development of UC; increased expression of RAC1 was associated with susceptibility to colitis

The spinal muscular atrophy with pontocerebellar hypoplasia gene VRK1 regulates neuronal migration through an amyloid-β precursor protein-dependent mechanism

Spinal muscular atrophy with pontocerebellar hypoplasia (SMA-PCH) is an infantile SMA variant with additional manifestations, particularly severe microcephaly. We previously identified a nonsense mutation in Vaccinia-related kinase 1 (VRK1), R358X, as a cause of SMA-PCH. VRK1-R358X is a rare founder mutation in Ashkenazi Jews, and additional mutations in patients of different origins have recently been identified.VRK1is a nuclear serine/threonine protein kinaseknownto play multiple roles in cellular proliferation, cell cycle regulation, and carcinogenesis. However, VRK1 was not known to have neuronal functions before its identification as a gene mutated in SMA-PCH. Here we show that VRK1-R358X homozygosity results in lack of VRK1 protein, and demonstrate a role for VRK1 in neuronal migration and neuronal stem cell proliferation. Using shRNA in utero electroporation in mice, we show that Vrk1 knockdown significantly impairs cortical neuronal migration, and affects the cell cycle of neuronal progenitors. Expression of wild-type human VRK1 rescues both proliferation and migration phenotypes. However, kinase-dead human VRK1 rescues only the migration impairment, suggesting the role of VRK1 in neuronal migration is partly noncatalytic. Furthermore, we found that VRK1 deficiency in human and mouse leads to downregulation of amyloid-β precursor protein (APP), a known neuronal migration gene. APP overexpression rescues the phenotype caused by Vrk1 knockdown, suggesting that VRK1 affects neuronal migration through an APP-dependent mechanism.This study was supported by grants from the Israel Science Foundation (Grant 702/13 to P.R. and E.L.-L., and Grant 47/10 and 322/13 to O.R. and T.S.); by the Minerva Foundation with funding from the Federal German Ministry for Education and Research, the Jérôme Lejeune Foundation, the Benoziyo Center for Neurological diseases, the Kekst Family Center for Medical Genetics, and the David and Fela Shapell Family Center for Genetic Disorders Research (to O.R.); by the JAE (Programa Junta para la Amplición de Estudios) Consejo Superior de Investigaciones Científicas Fondo Social Europeo fellowship (to L.C.); by the Ministerio de Educación, Ciencia e Innovación (SAF2010-14935 and SAF2013-44810R, to P.A.L.); and by Kutxa-Fundación Inbiomed (to P.A.L.).Peer Reviewe

VRK1 regulates Cajal body dynamics and protects coilin from proteasomal degradation in cell cycle

Cajal bodies (CBs) are nuclear organelles associated with ribonucleoprotein functions and RNA maturation. CBs are assembled on coilin, its main scaffold protein, in a cell cycle dependent manner. The Ser-Thr VRK1 (vaccinia-related kinase 1) kinase, whose activity is also cell cycle regulated, interacts with and phosphorylates coilin regulating assembly of CBs. Coilin phosphorylation is not necessary for its interaction with VRK1, but it occurs in mitosis and regulates coilin stability. Knockdown of VRK1 or VRK1 inactivation by serum deprivation causes a loss of coilin phosphorylation in Ser184 and of CBs formation, which are rescued with an active VRK1, but not by kinase-dead VRK1. The phosphorylation of coilin in Ser184 occurs during mitosis before assembly of CBs. Loss of coilin phosphorylation results in disintegration of CBs, and of coilin degradation that is prevented by proteasome inhibitors. After depletion of VRK1, coilin is ubiquitinated in nuclei, which is partly mediated by mdm2, but its proteasomal degradation occurs in cytosol and is prevented by blocking its nuclear export. We conclude that VRK1 is a novel regulator of CBs dynamics and stability in cell cycle by protecting coilin from ubiquitination and degradation in the proteasome, and propose a model of CB dynamics.L. C. and M. S-G. were funded by JAE-CSIC-Fondo Social Europeo fellowships. This work was supported by grants from Ministerio de Ciencia e Innovación (SAF2010-14935), Ministerio de Economía y Competitividad (SAF2013-44810R, SAF2014-57791-REDC), and Junta de Castilla y León-Consejería de Educación (CSI002U14) to P.A.L;and grant (702/13) from the Israel Science Foundation to P.R. and E.L.L.Peer reviewe

(TA)(n) UDP-glucuronosyltransferase 1A1 promoter polymorphism in nigerian neonates

Nigerian neonates have a high incidence of bilirubin encephalopathy. Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency is prevalent in this population. (TA)(7) promoter polymorphism in the gene encoding the bilirubin conjugating enzyme UDP-glueuronosyltransferase 1A1 (UGT1A1) potentiates hyperbilirubinemia in G-6-PD deficient neonates. We studied (TA)(n) allele frequency to determine, at least in part, its contribution to the frequency and severity of hyperbilirubinemia. DNA was extracted from umbilical cord blood of sequentially born Nigerian neonates and the (TA)(n) UGT1A1 promoter sequence determined. The (TA)(n) allele distribution was compared with reported adults of varying African ancestry and Sephardic Jewish neonates. Among 88 Nigerian neonates, (TA)(6) and (TA)(7) alleles were almost equally distributed (0.46 and 0.43, respectively). Some individuals with (TA)(5) and (TA)(8) sequences were encountered. Allele distribution was similar to that of the African ancestry population but differed from the Sephardic Jewish newborns, in whom the (TA)(6)/(TA)(7) distribution was 0.65/0.35. Whereas 45% of Nigerian alleles and 50% of African ancestry alleles, respectively, included a (TA)(7) or (TA)(8) sequence, only 35% of Jewish alleles were (TA)(7) (p < 0.001), and no (TA)(8) alleles were encountered. The high frequency of (TA)(n) promoter polymorphism, coupled with G-6-PD deficiency, may contribute to the pathogenesis of extreme neonatal hyperbilirubinemia in Nigeria

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background: PGD for fragile X syndrome (FRAX) is inefficient, probably owing to fewer oocytes, poor embryo quality and difficulties in genetic analysis. We investigated IVF -PGD in FRAX mutation carriers compared with controls, looking at the effects of oocyte and embryo number/quality on live birth outcome. methods: We performed IVF -PGD in 27 patients with the FRAX mutation and 33 controls with other genetic diseases. Genetic testing was by multiplex PCR. results: Seventy-nine and 108 IVF -PGD cycles were started in FRAX mutation carriers and controls, respectively. Twenty-two patients had a premutation (CGG repeat number 60 -200) and five had a full mutation (300-2000 CGG repeats). FRAX patients required higher doses of gonadotrophins (6788 + 2379 versus 4360 + 2330, P , 0.001) but had lower peak serum estradiol levels (8166 + 5880 versus 10 211 + 4673, P ¼ 0.03) and fewer oocytes retrieved (9.8 + 6 versus 14 + 8, P ¼ 0.01). The cancelation rate (unsatisfactory ovarian response) was higher in the FRAX group than in the control group (13 versus 1%, P , 0.001). When embryos were transferred, ongoing pregnancy/live birth rates per transfer were similar (29 versus 36%, P ¼ 0.54). conclusions: Ovarian dysfunction in FRAX carriers is more prevalent and profound than previously appreciated, with a high cancelation rate and reduced efficiency of PGD. The main determinant for successful PGD for FRAX is ovarian dysfunction. When embryo transfer is possible, the results are comparable to PGD for other monogenic diseases

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background: PGD for fragile X syndrome (FRAX) is inefficient, probably owing to fewer oocytes, poor embryo quality and difficulties in genetic analysis. We investigated IVF -PGD in FRAX mutation carriers compared with controls, looking at the effects of oocyte and embryo number/quality on live birth outcome. methods: We performed IVF -PGD in 27 patients with the FRAX mutation and 33 controls with other genetic diseases. Genetic testing was by multiplex PCR. results: Seventy-nine and 108 IVF -PGD cycles were started in FRAX mutation carriers and controls, respectively. Twenty-two patients had a premutation (CGG repeat number 60 -200) and five had a full mutation (300-2000 CGG repeats). FRAX patients required higher doses of gonadotrophins (6788 + 2379 versus 4360 + 2330, P , 0.001) but had lower peak serum estradiol levels (8166 + 5880 versus 10 211 + 4673, P ¼ 0.03) and fewer oocytes retrieved (9.8 + 6 versus 14 + 8, P ¼ 0.01). The cancelation rate (unsatisfactory ovarian response) was higher in the FRAX group than in the control group (13 versus 1%, P , 0.001). When embryos were transferred, ongoing pregnancy/live birth rates per transfer were similar (29 versus 36%, P ¼ 0.54). conclusions: Ovarian dysfunction in FRAX carriers is more prevalent and profound than previously appreciated, with a high cancelation rate and reduced efficiency of PGD. The main determinant for successful PGD for FRAX is ovarian dysfunction. When embryo transfer is possible, the results are comparable to PGD for other monogenic diseases

Non-invasive prenatal diagnosis using cell-free fetal DNA in maternal plasma from PGD pregnancies

Preimplantation genetic diagnosis (PGD) is usually used to establish a non-affected pregnancy for those couples facing a genetic risk of having an affected child. However, an invasive test is still recommended to all PGD patients due to the risk of misdiagnosis. The discovery of cell-free fetal DNA in maternal plasma provides the possibility for noninvasive prenatal diagnosis. Studies have shown that fetal single-gene disorders can be detected in cell-free fetal DNA by the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) assay with single-allele base extension reaction (SABER) approach or by the size-fractionation approach, whereby cell-free fetal DNA is enriched on the basis of its smaller size compared with maternal DNA fragments. Recent studies have indicated that a combination of the two approaches increases the accuracy of detection. This study combined the two methods and examined fetal paternally inherited gene mutations in maternal plasma obtained from four PGD-conducted pregnancies. The presence or absence of mutations was correctly detected in all cases. This combined method could be used for risk-free prenatal diagnosis of diseases caused by single-gene mutations, and in particular for couples who undergo PGD who opt not to perform invasive prenatal confirmation due to the risk of abortion