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Background: Alpha-methylacyl-CoA racemase (AMACR) deficiency is a rare peroxisomal enzyme deficiency caused by biallelic variants in the AMACR gene. This deficiency leads to the accumulation of toxic bile acid intermediates (R)-trihydroxycholestenoic acid (THCA) and (R)-dihydroxycholestenoic acid (DHCA) and pristanic acid. With less than 20 patients described in literature, the phenotype of AMACR deficiency is poorly defined and no data on the natural history are available., Results: Here we describe a cohort of 12 patients (9 adults and 3 children) with genetically confirmed AMACR deficiency (median age at diagnosis 56 years, range 3-69), followed for an average of 6 years (between 2015 and 2023). Five novel pathogenic variants are described. In 5/9 adult patients, retinitis pigmentosa was detected at a median age of 45 years (range 30-61). The median delay to diagnosis of AMACR deficiency after the diagnosis of retinitis pigmentosa was 24 years (range 0-33). All adult patients subsequently developed neurological signs and symptoms after the age of 40 years; most frequently neuropathy, ataxia and cognitive decline with prior normal cognitive functioning. One patient presented with a stroke-like episode. All adult patients showed a typical MRI pattern involving the thalami and gray matter structures of the pons and midbrain. One patient had a hepatocellular carcinoma at the time of the AMACR deficiency diagnosis and two patients suffered from gallstones. All three included children had elevated liver transaminases as single presenting sign and showed no brain MRI abnormalities., Conclusion: AMACR deficiency can be considered as an adult slowly progressive disease with a predominant neurological phenotype. The main signs comprise retinitis pigmentosa, neuropathy, ataxia and cognitive decline; stroke-like episodes may occur. Recognition of typical MRI abnormalities may facilitate prompt diagnosis. In addition, there is a risk of liver fibrosis/cirrhosis and hepatocellular carcinoma in these patients, requiring active monitoring., (© 2024. The Author(s).)

Alpha-methyl acyl-CoA racemase deficiency (AMACRD) is a rare peroxisomal disorder that results in the accumulation of pristanic acid and 16 cases have been reported in the literature. Here, we present three additional patients, two confirmed by genomic study and one suspected. Three siblings who were born to healthy unrelated parents developed recurrent episodes of encephalopathy, seizures, and behavioral disturbances. In all 3, brain MRI showed lesions in the thalami, cerebral peduncles, and mesencephalic tegmentum, as well as brain volume loss. In addition, one patient had a chronic hemispheric infarct and an acute contralateral infarct, and another had a subacute infarct involving multiple vascular territories without abnormalities on MR angiography., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Renal cell carcinoma (RCC) is derived from renal tubular epithelial cells and is among the 10 most common cancers worldwide. Incidence of renal cell carcinoma is 400,000 individuals worldwide per year. The age of diagnosis is approximately 60years, and twice as many men are diagnosed as women. African Americans have a slightly higher rate of RCC than do White peoples. The reasons for this are not clear. Inherited syndromes in family, long term dialysis, smoking individuals who had quit smoking >10 years prior had a lower risk when compared to those who had quit <10 years. 22.5 pack-year smokers had a more than 50.0% increased RCC risk compared to nonsmokers, high body mass index i.e. 5kg/m2 increase in body mass index (BMI) was found to be strongly associated with RCC. BMI >35kg/m2 is associated with higher incidence of Cancer raise blood pressure- Higher BMI and hypertension were independently shown to increase the long-term risk of RCC in men. A rise of blood pressure of 10mmHg is associated with 10-22 percent risk of RCC. Clear cell carcinoma is the most common variety of renal cell carcinoma as compared to other varieties of renal cell carcinomas (68.0-75.0%). It has also been found that CAIX is positive for all papillary renal cell carcinoma and negative for CK7, AMACR & TEF. We also found that CK7, EMA, CD117 and CAIX are most commonly positive for all chromophobe renal cell carcinoma. It has been found that clear cell carcinoma is the most common variety of renal cell carcinoma as compared to other varieties of renal cell carcinomas (68.0-75.0%). Again it has also been found that CAIX is positive for all papillary renal cell carcinoma and negative for CK7, AMACR and TEF. Here it has been found that chromophobe carcinoma is most commonly positive for CK7, EMA, CD117 and CAIX. In a patient coming with signs and symptoms of renal cell carcinoma can be confirmed with the help of histoimmunological markers and in that case one can plan for a proper planning of management.

Objective: This study aimed to investigate the clinicopathological and molecular characteristics of ELOC(TCEB1)-mutant renal cell carcinoma., Methods: Sanger sequencing was used to assess 32 cases originally diagnosed as clear cell renal cell carcinoma with CK7 positive and/or fibromyomatous stroma. Of these, 4 patients with ELOC(TCEB1) gene mutation were screened, and their clinicopathological data were collected for histomorphological observation, immunohistochemical staining, and follow-up, and relevant pieces of literature were reviewed., Results: The 4 patients with ELOC(TCEB1) mutations were all males and aged between 57 and 64 years (median age: 59 years old). The tumor was located in the renal cortex, with a diameter of 2-3.5 cm. The cross-section was grayish-yellow and grayish brown, solid and nodular, and clearly demarcated from the surrounding tissues. Of the 4 patients, 3 harbored a thick fibrous pseudocapsule rich in smooth muscle and were separated from the surrounding normal renal tissue, and 2 of them showed focal invasion into the pseudocapsule, whereas 1 patient had no capsule but had focal invasion into the surrounding renal parenchyma. The tumor tissues mainly exhibited elongated or branched aciniform or tubular structures, commonly accompanied by interspersed small cystic and focal clustered short papillary structures. The cytoplasm of the tumor cells was rich and lightly stained, and the nuclear grading ranged from 1 to 2. All patients showed loose edema in the stroma, and 2 patients showed a small number of interspersed smooth muscle bundles. All 4 patients showed EMA, CA9, AMACR, and TCEB1 expression, and TCEB1 was mainly located in the nucleus. Vimentin, CK7, and CD10 expressions were observed in most cases; CD117, TFE3, HMB45, and melanA were not expressed in all tumors; the expression rate of Ki67 was 3%- 8%. All 4 patients had a point mutation in ELOC(TCEB1) Y79C. The patients were followed up for 24-93 months (mean 49 months), and all of them survived to date without recurrence or metastasis., Conclusion: ELOC(TCEB1)-mutant renal cell carcinoma is a rare type of renal cell carcinoma, which tends to occur in middle-aged and elderly men. The main characteristics of this tumor are the branching alveolar or tubular structure with clustered short papillae, presence of fibromyomatous stroma, and the expression of CK7, CA9, CD10, and AMACR. Positive TCEB1 nuclear staining may be an important marker and the Sanger sequencing method is helpful for the diagnosis of this type of RCC. Most patients harbor tumors exhibiting low nuclear grade and inert clinical behavior, and a few tumors exhibit high nuclear grade and aggressive characteristics., (Copyright © 2022 Elsevier GmbH. All rights reserved.)

The NAD(P)HX repair system is a metabolite damage repair mechanism responsible for restoration of NADH and NADPH after their inactivation by hydration. Deficiency in either of its two enzymes, NAD(P)HX dehydratase (NAXD) or NAD(P)HX epimerase (NAXE), causes a fatal neurometabolic disorder characterized by decompensations precipitated by inflammatory stress. Clinical findings include rapidly progressive muscle weakness, ataxia, ophthalmoplegia, and motor and cognitive regression, while neuroimaging abnormalities are subtle or nonspecific, making a clinical diagnosis challenging. During stress, nonenzymatic conversion of NAD(P)H to NAD(P)HX increases, and in the absence of repair, NAD(P)H is depleted, and NAD(P)HX accumulates, leading to decompensation; however, the contribution of each to the metabolic derangement is not established. Herein, we summarize the clinical knowledge of NAXE deficiency from 30 cases and lessons learned about disease pathogenesis from cell cultures and model organisms and describe a metabolomics signature obtained by untargeted metabolomics analysis in one case at the time of crisis and after initiation of treatment. Overall, biochemical findings support a model of acute depletion of NAD + , signs of mitochondrial dysfunction, and altered lipidomics. These findings are further substantiated by untargeted metabolomics six months post-crisis showing that niacin supplementation reverses primary metabolomic abnormalities concurrent with improved clinical status., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Alpha-methylacyl-CoA racemase (AMACR) deficiency is a rare peroxisomal disorder causing pristanic acid accumulation. Only 16 cases have been described so far. A female in her seventh decade presented with episodes of dysphasia, headache and sensory disturbance inconsistent with migraine, epilepsy or transient ischaemic attack. An MRI demonstrated unusual changes in the pons, red nuclei, thalami and white matter. Mitochondrial disease was suspected but detailed testing was negative. After eight years of symptoms, she developed a febrile encephalopathy with hemispheric dysfunction, focal convulsive seizures and coma. Her condition stabilised after one month. Lacosamide was continued for seizure prevention. The diagnosis remained elusive until whole genome sequencing revealed AMACR deficiency. Pristanic acid levels were highly elevated and dietary modification was recommended. Genetic peroxisomal disorders can present in older age; our patient is the oldest in the AMACR deficiency literature. Novel features in our case include central apnoea, dystonia and rapid eye movement behaviour disorder., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2022. No commercial re-use. See rights and permissions. Published by BMJ.)

Purpose: Alpha-methylacyl-CoA racemase (AMACR) deficiency is a peroxisomal disorder due to biallelic mutations in AMACR. At least 13 genetically confirmed patients have been reported to date. Seven had obvious pigmentary retinopathy; however, for the other six, no retinal phenotype was mentioned. The purpose of this report is to document subtle retinal findings in an additional affected family., Methods: Retrospective case series (three affected siblings and their unaffected parents)., Results: Three Arab siblings (16, 19, and 22 years old) with prior juvenile cholelithiasis had been diagnosed with AMACR deficiency based on biochemical analysis, whole exome sequencing, and confirmatory segregation analysis (AMACR NM&#95;001167595.1: c.877T>C; p.C293R). For all three, there were no visual complaints, but retinal multimodal imaging and electroretinography suggested subtle retinal dysfunction., Conclusions: Retinal dysfunction is a parameter that should be measured in patients with known or suspected AMACR deficiency even in the absence of visual symptoms. This may be helpful with clinical diagnosis and monitoring response to dietary interventions., (Copyright © 2021 Molecular Vision.)

There is substantial evidence that both N -methyl-D-aspartate receptor (NMDAR) hypofunction and dysfunction of GABAergic neurotransmission contribute to schizophrenia, though the relationship between these pathophysiological processes remains largely unknown. Although models using cell-type-specific genetic deletion of NMDARs have been informative, they display overly pronounced phenotypes extending beyond those of schizophrenia. Here, we used the serine racemase knockout (SRKO) mice, a model of reduced NMDAR activity rather than complete receptor elimination, to examine the link between NMDAR hypofunction and decreased GABAergic inhibition. The SRKO mice, in which there is a >90% reduction in the NMDAR coagonist d-serine, exhibit many of the neurochemical and behavioral abnormalities observed in schizophrenia. We found a significant reduction in inhibitory synapses onto CA1 pyramidal neurons in the SRKO mice. This reduction increases the excitation/inhibition balance resulting in enhanced synaptically driven neuronal excitability without changes in intrinsic excitability. Consistently, significant reductions in inhibitory synapse density in CA1 were observed by immunohistochemistry. We further show, using a single-neuron genetic deletion approach, that the loss of GABAergic synapses onto pyramidal neurons observed in the SRKO mice is driven in a cell-autonomous manner following the deletion of SR in individual CA1 pyramidal cells. These results support a model whereby NMDAR hypofunction in pyramidal cells disrupts GABAergic synapses leading to disrupted feedback inhibition and impaired neuronal synchrony. NEW & NOTEWORTHY Recently, disruption of excitation/inhibition (E/I) balance has become an area of considerable interest for psychiatric research. Here, we report a reduction in inhibition in the serine racemase knockout mouse model of schizophrenia that increases E/I balance and enhances synaptically driven neuronal excitability. This reduced inhibition was driven cell-autonomously in pyramidal cells lacking serine racemase, suggesting a novel mechanism for how chronic NMDA receptor hypofunction can disrupt information processing in schizophrenia.

Prefrontal control of cognitive functions critically depends upon glutamatergic transmission and N-methyl D-aspartate (NMDA) receptors, the activity of which is regulated by dopamine. Yet whether the NMDA receptor coagonist d-serine is implicated in the dopamine-glutamate dialogue in the prefrontal cortex (PFC) and other brain areas remains unexplored. Here, using electrophysiological recordings, we show that d-serine is required for the fine-tuning of glutamatergic neurotransmission, neuronal excitability, and synaptic plasticity in the PFC through the actions of dopamine at D 1 and D 3 receptors. Using in vivo microdialysis, we show that D 1 and D 3 receptors exert a respective facilitatory and inhibitory influence on extracellular levels and activity of d-serine in the PFC, with actions expressed primarily via the cAMP/protein kinase A (PKA) signaling cascade. Further, using functional magnetic resonance imaging (fMRI) and behavioral assessment, we show that d-serine is required for the potentiation of cognition by D 3 R blockade as revealed in a test of novel object recognition memory. Collectively, these results unveil a key role for d-serine in the dopaminergic neuromodulation of glutamatergic transmission and PFC activity, findings with clear relevance to the pathogenesis and treatment of diverse brain disorders involving alterations in dopamine-glutamate cross-talk., Competing Interests: Competing interest statement: M.J.M. and J.-M.R., respectively, were and are full-time employees of Institut de Recherche Servier and have no other interests to declare. S. Schmidt and J.K. are employees of Pronexus Analytical AB but declare no conflicts of interests.

Human methylmalonyl-CoA epimerase (MCEE) catalyzes the interconversion of d-methylmalonyl-CoA and l-methylmalonyl-CoA in propionate catabolism. Autosomal recessive pathogenic variations in MCEE reportedly cause methylmalonic aciduria (MMAuria) in eleven patients. We investigated a cohort of 150 individuals suffering from MMAuria of unknown origin, identifying ten new patients with pathogenic variations in MCEE. Nine patients were homozygous for the known nonsense variation p.Arg47* (c.139C > T), and one for the novel missense variation p.Ile53Arg (c.158T > G). To understand better the molecular basis of MCEE deficiency, we mapped p.Ile53Arg, and two previously described pathogenic variations p.Lys60Gln and p.Arg143Cys, onto our 1.8 Å structure of wild-type (wt) human MCEE. This revealed potential dimeric assembly disruption by p.Ile53Arg, but no clear defects from p.Lys60Gln or p.Arg143Cys. We solved the structure of MCEE-Arg143Cys to 1.9 Å and found significant disruption of two important loop structures, potentially impacting surface features as well as the active-site pocket. Functional analysis of MCEE-Ile53Arg expressed in a bacterial recombinant system as well as patient-derived fibroblasts revealed nearly undetectable soluble protein levels, defective globular protein behavior, and using a newly developed assay, lack of enzymatic activity - consistent with misfolded protein. By contrast, soluble protein levels, unfolding characteristics and activity of MCEE-Lys60Gln were comparable to wt, leaving unclear how this variation may cause disease. MCEE-Arg143Cys was detectable at comparable levels to wt MCEE, but had slightly altered unfolding kinetics and greatly reduced activity. These studies reveal ten new patients with MCEE deficiency and rationalize misfolding and loss of activity as molecular defects in MCEE-type MMAuria., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

Inborn errors of bile acid metabolism are rare causes of neonatal cholestasis and liver disease in older children and adults. The diagnosis should be considered in the context of hyperbilirubinemia with normal serum bile acids and made by urinary liquid secondary ionization mass spectrometry or DNA testing. Cholic acid is an effective treatment of most single-enzyme defects and patients with Zellweger spectrum disorder with liver disease., (Copyright © 2018 Elsevier Inc. All rights reserved.)

NADHX and NADPHX are hydrated and redox inactive forms of the NADH and NADPH cofactors, known to inhibit several dehydrogenases in vitro. A metabolite repair system that is conserved in all domains of life and that comprises the two enzymes NAD(P)HX dehydratase and NAD(P)HX epimerase, allows reconversion of both the S- and R-epimers of NADHX and NADPHX to the normal cofactors. An inherited deficiency in this system has recently been shown to cause severe neurometabolic disease in children. Although evidence for the presence of NAD(P)HX has been obtained in plant and human cells, little is known about the mechanism of formation of these derivatives in vivo and their potential effects on cell metabolism. Here, we show that NAD(P)HX dehydratase deficiency in yeast leads to an important, temperature-dependent NADHX accumulation in quiescent cells with a concomitant depletion of intracellular NAD + and serine pools. We demonstrate that NADHX potently inhibits the first step of the serine synthesis pathway in yeast. Human cells deficient in the NAD(P)HX dehydratase also accumulated NADHX and showed decreased viability. In addition, those cells consumed more glucose and produced more lactate, potentially indicating impaired mitochondrial function. Our results provide first insights into how NADHX accumulation affects cellular functions and pave the way for a better understanding of the mechanism(s) underlying the rapid and severe neurodegeneration leading to early death in NADHX repair-deficient children., (© 2018 Federation of European Biochemical Societies.)

NAD(P)H-hydrate epimerase (EC 5.1.99.6) is known to help repair NAD(P)H hydrates (NAD(P)HX), which are damage products existing as R and S epimers. The S epimer is reconverted to NAD(P)H by a dehydratase; the epimerase facilitates epimer interconversion. Epimerase deficiency in humans causes a lethal disorder attributed to NADHX accumulation. However, bioinformatic evidence suggest caution about this attribution by predicting that the epimerase has a second function connected to vitamin B 6 (pyridoxal 5'-phosphate and related compounds). Specifically, (i) the epimerase is fused to a B 6 salvage enzyme in plants, (ii) epimerase genes cluster on the chromosome with B 6 -related genes in bacteria, and (iii) epimerase and B 6 -related genes are coexpressed in yeast and Arabidopsis The predicted second function was explored in Escherichia coli , whose epimerase and dehydratase are fused and encoded by yjeF The putative NAD(P)HX epimerase active site has a conserved lysine residue (K192 in E. coli YjeF). Changing this residue to alanine cut in vitro epimerase activity by ≥95% but did not affect dehydratase activity. Mutant cells carrying the K192A mutation had essentially normal NAD(P)HX dehydratase activity and NAD(P)HX levels, showing that the mutation had little impact on NAD(P)HX repair in vivo However, these cells showed metabolome changes, particularly in amino acids, which exceeded those in cells lacking the entire yjeF gene. The K192A mutant cells also had reduced levels of 'free' (i.e. weakly bound or unbound) pyridoxal 5'-phosphate. These results provide circumstantial evidence that the epimerase has a metabolic function beyond NAD(P)HX repair and that this function involves vitamin B 6 ., (© 2018 The Author(s).)

Inward migration of cerebellar granule cells (CGCs) after birth is critical for lamination in the cerebellar cortex. N-methyl-d-aspartate (NMDA) subtype of glutamate receptor (NMDAR) tethering CGCs into Bergmann glial fibers mediates the inward movement during the glial-dependent migratory phase. Activation of NMDAR depends on simultaneous binding of the GluN2 subunit by glutamate, and of the GluN1 subunit by d-serine or glycine; d-serine is believed to be an endogenous ligand of NMDAR. We hypothesized that lamination of the cerebellar cortex may be compromised in Srr (the gene for serine racemase (SR)) mutated mice (Srr null ) because of significantly low levels of d-serine per se. Indeed, the external germinal cell layer (EGL) in Srr null was thicker than in sibling wild-type (WT) mice on postnatal day7 (P7), which accords with decreased CGC migration in Srr null mice. However, the cerebellar laminar structure in Srr null mice was normal on P12 and later. Feeding d-serine to pregnant mice abrogated the increased EGL thickness in Srr null mice on P7. To determine the underlying mechanism of abnormal laminar structure during cerebellar development in Srr null mice, we examined NMDAR subunits and their ligands. We found increased GluN2B on P10 and increased glycine during P7-12 in the cerebellar homogenates from Srr null mice compared with the corresponding values from sibling WT mice. In summary, the study revealed how the potential defect in early cerebellar development caused by Srr mutation is circumvented by a compensatory mechanism. This knowledge advances understanding of the adaptation of cerebellar development under the condition of Srr mutation., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Choroidal neovascularization (CNV) is a leading cause of blindness in age-related macular degeneration. Production of vascular endothelial growth factor (VEGF) and macrophage recruitment by retinal pigment epithelial cells (RPE) significantly contributes to the process of CNV in an experimental CNV model. Serine racemase (SR) is expressed in retinal neurons and glial cells, and its product, d-serine, is an endogenous co-agonist of N-methyl-d-aspartate receptor. Activation of the receptor results in production of nitric oxide ( . NO), a molecule that promotes retinal and choroidal neovascularization. These observations suggest possible roles of SR in CNV. With laser-injured CNV mice, we found that inactivation of SR-coding gene (Srr null ) significantly reduced CNV volume, neovascular density, and invading macrophages. We exploited the underlying mechanism in vivo and ex vivo. RPE from wild-type (WT) mice expressed SR. To explore the possible downstream target of SR inactivation, we showed that choroid/RPE homogenates extracted from laser-injured Srr null mice contained less inducible nitric oxide synthase and decreased phospho-VEGFR2 compared to amounts in WT mice. In vitro, inflammation-primed WT RPEs expressed more inducible NOS, produced more . NO and VEGF than did inflammation-primed Srr null RPEs. When co-cultured with inflammation-primed Srr null RPE, significantly fewer RF/6A-a cell line of choroidal endothelial cell, migrated to the opposite side of the insert membrane than did cells co-cultured with pre-treated WT RPE. Altogether, SR deficiency reduces RPE response to laser-induced inflammatory stimuli, resulting in decreased production of a cascade of pro-angiogenic cytokines, including . NO and VEGF, and reduced macrophage recruitment, which contribute synergistically to attenuated angiogenesis., (© 2017 International Society for Neurochemistry.)

We have used mutant mice to probe the roles of the endogenous co-agonists of the NMDA receptor (NMDAR), D-serine and glycine, in fear learning and memory. Serine racemase knockout (SR-/-) mice have less than 15% of wild type forebrain levels of D-serine, whereas glycine transporter 1 heterozygous knockout (GlyT1+/-) mice have elevated synaptic glycine. While cued fear was normal in both delay and trace conditioned mice of both mutant genotypes, contextual fear was affected in trace conditioned subjects: SR-/- mice showed decreased contextual freezing, whereas GlyT1+/- mice showed elevated contextual freezing. These results indicate that endogenous co-agonists of the NMDAR modulate the conditioning of contextual fear responses, particularly in trace conditioning. They further suggest that endogenous glycine can compensate for the D-serine deficiency in cued and contextual fear following delay conditioning., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Peroxisomal disorders are a heterogeneous group of genetic metabolic disorders, caused by a defect in peroxisome biogenesis or a deficiency of a single peroxisomal enzyme. The peroxisomal disorders include the Zellweger spectrum disorders, the rhizomelic chondrodysplasia punctata spectrum disorders, X-linked adrenoleukodystrophy, and multiple single enzyme deficiencies. There are several core phenotypes caused by peroxisomal dysfunction that clinicians can recognize. The diagnosis is suggested by biochemical testing in blood and urine and confirmed by functional assays in cultured skin fibroblasts, followed by mutation analysis. This review describes the phenotype of the main peroxisomal disorders and possible pitfalls in (laboratory) diagnosis to aid clinicians in the recognition of this group of diseases., (Georg Thieme Verlag KG Stuttgart · New York.)

Clear cell papillary renal cell carcinoma (CCPRCC) cases were evaluated for mutations on the following genes: KRAS, NRAS, BRAF, PIK3CA, ALK, ERBB2, DDR2, MAP2K1, RET and EGFR. Four male and three female patients of age 42-74 years were evaluated. All cases were incidentally detected by ultrasound and ranged 1.8-3.5 cm. Microscopic examination showed variably tubulopapillary, tubular acinar, cystic architecture and the characteristic linear arrangement of nuclei. The cells were reactive with CK7 (strong), CA IX (cup-shape) and 34 β E12. CD10, AMACR/RACEMASE and GATA3 were negative. There were no mutations on any of the investigated genes. This preliminary observation supports the concept that CCPRCC might be indeed an indolent tumour worth it to be named as clear cell papillary neoplasm of low potential., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/)

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. Altering the metabolism of immune cells is an attractive strategy to modify their activity during autoimmunity in MS. We investigated the effect of modulating fatty acid metabolism in an animal model of MS, EAE. Alpha-methylacyl-CoA racemase (AMACR) converts R-configuration branched fatty acids into the S-configuration, thereby preparing them for β-oxidation. We observed a significant, disease-dependent elevation of AMACR expression in monocytes and T cells from blood, draining lymph nodes and spleen of EAE mice during the preclinical phase. In vitro analysis revealed that the proliferation of T cells was inhibited in AMACR KO mice, but T-cell polarization was switched toward a pathogenic state involving the production of more IFN-γ and IL-17, but less IL-4. These opposing effects appeared to cancel out each other in vivo, because AMACR KO EAE mice showed a marginal increase in the severity of early clinical symptoms. AMACR was not regulated in the white blood cells of MS patients. Our data show that AMACR is regulated in immune cells during EAE, but it is not a suitable target for the treatment of MS due to its opposing effects., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

One of the key regulators of endochondral ossification is Indian hedgehog (Ihh), which acts as a long-range morphogen in the developing skeletal elements. Previous studies have shown that the distribution and signaling activity of Ihh is regulated by the concentration of the extracellular glycosaminoglycan heparan sulfate (HS). An essential step during biosynthesis of HS is the epimerization of D-glucuronic to L-iduronic acid by the enzyme glucuronyl C5-epimerase (Hsepi or Glce). Here we have investigated chondrocyte differentiation in Glce deficient mice and found increased regions of proliferating chondrocytes accompanied by a delayed onset of hypertrophic differentiation. In addition, we observed increased expression levels of the Ihh target genes Patched1 (Ptch1) and Parathyroid hormone related peptide (Pthrp; Parathyroid hormone like hormone (Pthlh)) indicating elevated Ihh signaling. We further show that Ihh binds with reduced affinity to HS isolated from Glce(-/-) mice. Together our results strongly indicate that not only the level, but also the structure of HS is critical in regulating the distribution and signaling activity of Ihh in chondrocytes., (Copyright © 2015. Published by Elsevier B.V.)

α-Methylacyl-CoA racemase (Amacr) catalyzes the racemization of the 25-methyl group in C27-intermediates in bile acid synthesis and in methyl-branched fatty acids such as pristanic acid, a metabolite derived from phytol. Consequently, patients with Amacr deficiency accumulate C27-bile acid intermediates, pristanic and phytanic acid and display sensorimotor neuropathy, seizures and relapsing encephalopathy. In contrast to humans, Amacr-deficient mice are clinically symptomless on a standard laboratory diet, but failed to thrive when fed phytol-enriched chow. In this study, the effect and the mechanisms behind the development of the phytol-feeding associated disease state in Amacr-deficient mice were investigated. All Amacr-/- mice died within 36weeks on a phytol diet, while wild-type mice survived. Liver failure was the main cause of death accompanied by kidney and brain abnormalities. Histological analysis of liver showed inflammation, fibrotic and necrotic changes, Kupffer cell proliferation and fatty changes in hepatocytes, and serum analysis confirmed the hepatic disease. Pristanic and phytanic acids accumulated in livers of Amacr-/- mice after a phytol diet. Microarray analysis also revealed changes in the expression levels of numerous genes in wild-type mouse livers after two weeks of the phytol diet compared to a control diet. This indicates that detoxification of phytol metabolites in liver is accompanied by activation of multiple pathways at the molecular level and Amacr-/- mice are not able to respond adequately. Phytol causes primary failure in liver leading to death of Amacr-/- mice thus emphasizing the indispensable role of Amacr in detoxification of α-methyl-branched fatty acids., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Schizophrenia is associated with high prevalence of substance abuse. Recent research suggests that dysregulation of N-methyl-d-aspartate receptor (NMDAR) function may play a role in the pathophysiology of both schizophrenia and drug addiction, and thus, may account for this high comorbidity. Our laboratory has developed two transgenic mouse lines that exhibit contrasting NMDAR activity based on the availability of the glycine modulatory site (GMS) agonists d-serine and glycine. Glycine transporter 1 knockdowns (GlyT1(+/-)) exhibit NMDAR hyperfunction, whereas serine racemase knockouts (SR(-/-)) exhibit NMDAR hypofunction. We characterized the behavior of these lines in a cocaine-induced (20 mg/kg) conditioned place preference (CPP) and locomotor sensitization paradigm. Compared with wild-type mice, GlyT1(+/-) mice displayed hastened extinction of CPP and robust cocaine-induced reinstatement. SR(-/-) mice appeared to immediately "forget" the learned preference, because they did not exhibit cocaine-induced reinstatement and also displayed attenuated locomotor sensitization. Treatment of GlyT1(+/-) mice with gavestinel (10 mg/kg on day 1; 5 mg/kg on days 2-17), a GMS antagonist, attenuated cocaine-induced CPP and caused them to immediately "forget" the learned preference. Treatment of SR(-/-) mice with d-serine (300 mg/kg on day 1; 150 mg/kg on days 2-17) to normalize brain levels caused them to avoid the cocaine-paired side of the chamber during extinction. These results highlight NMDAR dysfunction as a possible neural mechanism underlying comorbid schizophrenia and substance abuse. Also, these findings suggest drugs that directly or indirectly activate the NMDAR GMS could be an effective treatment of cocaine abuse., (Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.)

NMDA receptor (NMDAR) hypofunction is a compelling hypothesis for the pathophysiology of schizophrenia, because in part, NMDAR antagonists cause symptoms in healthy adult subjects that resemble schizophrenia. Therefore, NMDAR antagonists have been used as a method to induce NMDAR hypofunction in animals as a pharmacological model of schizophrenia. Serine racemase-null mutant (SR-/-) mice display constitutive NMDAR hypofunction due to the lack of d-serine. SR-/- mice have deficits in tropomyosin-related kinase receptor (TrkB)/Akt signaling and activity regulated cytoskeletal protein (Arc) expression, which mirror what is observed in schizophrenia. Thus, we analyzed these signaling pathways in MK801 sub-chronically (0.15mg/kg; 5days) treated adult wild-type mice. We found that in contrast to SR-/- mice, the activated states of downstream signaling molecules, but not TrkB, increased in MK801 treated mice. Furthermore, there is an age-dependent change in the behavioral reaction of people to NMDAR antagonists. We therefore administered the same dosing regimen of MK801 to juvenile mice and compared them to juvenile SR-/- mice. Our findings demonstrate that pharmacological NMDAR antagonism has different effects on TrkB/Akt signaling than genetically-induced NMDAR hypofunction. Given the phenotypic disparity between the MK801 model and schizophrenia, our results suggest that SR-/- mice more accurately reflect NMDAR hypofunction in schizophrenia., (Copyright © 2015 Elsevier B.V. All rights reserved.)

D-Serine, an N-methyl D-aspartate receptor coagonist, and its regulatory enzymes, D-amino acid oxidase (DAO; degradation) and serine racemase (SR; synthesis), have been implicated in crucial roles of the developing central nervous system, yet the functional position that they play in regulating the availability of d-serine throughout development of the mammalian retina is not well-known. Using capillary electrophoresis and a sensitive method of enantiomeric amino acid separation, we were able to determine total levels of d-serine at specific ages during postnatal development of the mouse retina in two different strains of mice, one of which contained a loss-of-function point mutation for DAO while the other was a SR knockout line. Each mouse line was tested against conspecific wild type (WT) mice for each genetic strain. The universal trend in all WT and transgenic mice was a large amount of total retinal d-serine at postnatal age 2 (P2), followed by a dramatic decrease as the mice matured into adulthood (P70-80). SR knockout mice retinas had 41% less D-serine than WT retinas at P2, and 10 times less as an adult. DAO mutant mice retinas had significantly elevated levels of d-serine when compared to WT retinas at P2 (217%), P4 (223%), P8 (194%), and adulthood (227%).

Cholesterol is catabolized to bile acids by peroxisomal β-oxidation in which the side chain of C27-bile acid intermediates is shortened by three carbon atoms to form mature C24-bile acids. Knockout mouse models deficient in AMACR (α-methylacyl-CoA racemase) or MFE-2 (peroxisomal multifunctional enzyme type 2), in which this β-oxidation pathway is prevented, display a residual C24-bile acid pool which, although greatly reduced, implies the existence of alternative pathways of bile acid synthesis. One alternative pathway could involve Mfe-1 (peroxisomal multifunctional enzyme type 1) either with or without Amacr. To test this hypothesis, we generated a double knockout mouse model lacking both Amacr and Mfe-1 activities and studied the bile acid profiles in wild-type, Mfe-1 and Amacr single knockout mouse line and Mfe-1 and Amacr double knockout mouse lines. The total bile acid pool was decreased in Mfe-1-/- mice compared with wild-type and the levels of mature C24-bile acids were reduced in the double knockout mice when compared with Amacr-deficient mice. These results indicate that Mfe-1 can contribute to the synthesis of mature bile acids in both Amacr-dependent and Amacr-independent pathways.

Both the serotonin and glutamate systems have been implicated in the pathophysiology of schizophrenia, as well as in the mechanism of action of antipsychotic drugs. Psychedelic drugs act through the serotonin 2A receptor (5-HT2AR), and elicit a head-twitch response (HTR) in mice, which directly correlates to 5-HT2AR activation and is absent in 5-HT2AR knockout mice. The precise mechanism of this response remains unclear, but both an intrinsic cortico-cortical pathway and a thalamo-cortical pathway involving glutamate release have been proposed. Here, we used a genetic model of NMDAR hypofunction, the serine racemase knockout (SRKO) mouse, to explore the role of glutamatergic transmission in regulating 5-HT2AR-mediated cellular and behavioral responses. SRKO mice treated with the 5-HT2AR agonist (±)-2,5-dimethoxy-4-iodoamphetamine (DOI) showed a clearly diminished HTR and lower induction of c-fos mRNA. These altered functional responses in SRKO mice were not associated with changes in cortical or hippocampal 5-HT levels or in 5-HT2AR and metabotropic glutamate-2 receptor (mGluR2) mRNA and protein expression. Together, these findings suggest that D-serine-dependent NMDAR activity is involved in mediating the cellular and behavioral effects of 5-HT2AR activation., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Schizophrenia is characterized by reduced hippocampal volume, decreased dendritic spine density, altered neuroplasticity signaling pathways, and cognitive deficits associated with impaired hippocampal function. We sought to determine whether this diverse pathology could be linked to NMDA receptor (NMDAR) hypofunction, and thus used the serine racemase-null mutant mouse (SR(-/-)), which has less than 10% of normal brain D-serine, an NMDAR coagonist. We found that D-serine was necessary for the maintenance of long-term potentiation in the adult hippocampal dentate gyrus and for full NMDAR activity on granule cells. SR(-/-) mice had reduced dendritic spines and hippocampal volume. These morphological changes were paralleled by diminished BDNF/Akt/mammalian target of rapamycin (mTOR) signaling and impaired performance on a trace-conditioning memory task. Chronic D-serine treatment normalized the electrophysiological, neurochemical, and cognitive deficits in SR(-/-) mice. These results demonstrate that NMDAR hypofunction can reproduce the numerous hippocampal deficits associated with schizophrenia, which can be reversed by chronic peripheral D-serine treatment.

The N-methyl-D-aspartate (NMDA)-type glutamate receptor plays a key role in excitatory synaptic transmission. The overactivation of the NMDA receptor has been implicated in the development of epileptic seizures. D-Serine is a coagonist of the NMDA receptor and its biosynthesis is catalyzed by serine racemase (SR). Here, we examined the effect of d-serine deficiency on the seizures induced by a single injection of pentylenetetrazole (PTZ) using SR knockout (KO) mice. We found that, compared with wild-type (WT) mice, SR-KO mice showed the attenuation of seizure expression in terms of a significantly shortened duration of generalized seizures and resistance to generalized clonic-tonic seizures. Consistently, immunohistochemical analysis of c-Fos demonstrated that the numbers of cells expressing c-Fos induced by high-dose PTZ in the cerebral cortex, hippocampal CA1, hippocampal CA3, and the basolateral nucleus of the amygdala in WT mice were significantly higher than those in SR-KO mice. Moreover, PTZ induced an increase in extracellular glutamate level in the dentate gyrus of WT mice at two different time phases. However, such a PTZ-induced increase in glutamate level was completely inhibited in SR-KO mice. The present findings suggest that SR may be a target for the development of new therapeutic strategies for epileptic seizures., (Copyright © 2012 Elsevier B.V. All rights reserved.)

For elucidation of the regulation mechanisms of intrinsic amounts of D-serine (D-Ser) which modulates the neuro-transmission of N-methyl-D-aspartate receptors in the brain, mutant animals lacking serine racemase (SRR) and D-amino acid oxidase (DAO) were established, and the amounts of D-Ser in the tissues and physiological fluids were determined. D-Ser amounts in the frontal brain areas were drastically decreased followed by reduced SRR activity. On the other hand, a moderate but significant decrease in D-Ser amounts was observed in the cerebellum and spinal cord of SRR knock-out (SRR(-/-)) mice compared with those of control mice, although the amounts of D-Ser in these tissues were low. The amounts of D-Ser in the brain and serum were not altered with aging. To clarify the uptake of exogenous D-Ser into the brain tissues, we have determined the D-Ser of SRR(-/-) mice after oral administration of D-Ser for the first time, and a drastic increase in D-Ser amounts in all the tested tissues was observed. Because both DAO and SRR are present in some brain areas, we have established the double mutant mice lacking SRR and DAO for the first time, and the contribution of both enzymes to the intrinsic D-Ser amounts was investigated. In the frontal brain, most of the intrinsic D-Ser was biosynthesized by SRR. On the other hand, half of the D-Ser present in the hindbrain was derived from the biosynthesis by SRR. These results indicate that the regulation of intrinsic D-Ser amounts is different depending on the tissues and provide useful information for the development of treatments for neuronal diseases.

The discovery of large amounts of D-serine in the brain challenged the dogma that only L-amino acids are relevant for eukaryotes. The levels of D-serine in the brain are higher than many L-amino acids and account for as much as one-third of L-serine levels. Several studies in the last decades have demonstrated a role of D-serine as an endogenous agonist of N-methyl-D-aspartate receptors (NMDARs). D-Serine is required for NMDAR activity during normal neurotransmission as well as NMDAR overactivation that takes place in neurodegenerative conditions. Still, there are many unanswered questions about D-serine neurobiology, including regulation of its synthesis, release and metabolism. Here, we review the mechanisms of D-serine synthesis by serine racemase and discuss the lessons we can learn from serine racemase knockout mice, focusing on the roles attributed to D-serine and its cellular origin.

Genome-wide studies may lead to the discovery of genetic variants of potential clinical importance beyond the aims of the study. We performed single nucleotide polymorphism array analysis in a boy with oculocutaneous albinism to identify copy-neutral regions of homozygosity harboring genes involved in melanin biosynthesis. An unanticipated homozygous deletion of chromosome 5p13.3 was discovered, encompassing not only the OCA gene SLC45A2, but also four additional genes. This led to an unexpected presymptomatic diagnosis of alpha-methylacyl-CoA racemase deficiency in the same patient., (Copyright © 2012 Wiley Periodicals, Inc.)

Peroxisome biogenesis and peroxisomal β-oxidation defects are rare inherited metabolic disorders in which several organs can be affected. A panel of mouse models has been created in which genes crucial to these processes were inactivated and the ensuing pathologies studied. In mice with enzyme defects of peroxisomal β-oxidation, the disease state strongly depends on the kind of substrates that are metabolized by the enzyme and the dietary composition. Because mice with generalized biogenesis defects seldom reach adulthood, conditional knockout models were generated to study the consequences of peroxisome deficiency in hepatocytes, different brain cell types and Sertoli cells. Although the precise relationship between the biochemical anomalies and pathologies was often not resolved, the mouse models allowed to document in detail histological abnormalities, metabolic and gene expression deregulations some of which are mediated by PPARα, and to uncover the essential role of peroxisomes in some unsuspected cell types., (Copyright © 2012 Elsevier B.V. All rights reserved.)

D-serine, which is synthesized by the enzyme serine racemase (SR), is a co-agonist at the N-methyl-D-aspartate receptor (NMDAR). Crucial to an understanding of the signaling functions of D-serine is defining the sites responsible for its synthesis and release. In order to quantify the contributions of astrocytes and neurons to SR and D-serine localization, we used recombinant DNA techniques to effect cell type selective suppression of SR expression in astrocytes (aSRCKO) and in forebrain glutamatergic neurons (nSRCKO). The majority of SR is expressed in neurons: SR expression was reduced by ~65% in nSRCKO cerebral cortex and hippocampus, but only ~15% in aSRCKO as quantified by western blots. In contrast, nSRCKO is associated with only modest decreases in D-serine levels as quantified by HPLC, whereas D-serine levels were unaffected in aSRCKO mice. Liver expression of SR was increased by 35% in the nSRCKO, suggesting a role for peripheral SR in the maintenance of brain D-serine. Electrophysiologic studies of long-term potentiation (LTP) at the Schaffer collateral-CA1 pyramidal neuron synapse revealed no alterations in the aSRCKO mice versus wild-type. LTP induced by a single tetanic stimulus was reduced by nearly 70% in the nSRCKO mice. Furthermore, the mini-excitatory post-synaptic currents mediated by NMDA receptors but not by AMPA receptors were significantly reduced in nSRCKO mice. Our findings indicate that in forebrain, where D-serine appears to be the endogenous co-agonist at NMDA receptors, SR is predominantly expressed in glutamatergic neurons, and co-release of glutamate and D-serine is required for optimal activation of post-synaptic NMDA receptors.

There is substantial evidence, both pharmacological and genetic, that hypofunction of the N-methyl-d-aspartate receptor (NMDAR) is a core pathophysiological feature of schizophrenia. There are morphological brain changes associated with schizophrenia, including perturbations in the dendritic morphology of cortical pyramidal neurons and reduction in cortical volume. Our experiments investigated whether these changes in dendritic morphology could be recapitulated in a genetic model of NMDAR hypofunction, the serine racemase knockout (SR-/-) mouse. Pyramidal neurons in primary somatosensory cortex (S1) of SR-/- mice had reductions in the complexity, total length, and spine density of apical and basal dendrites. In accordance with reduced cortical neuropil, SR-/- mice also had reduced cortical volume as compared to wild type mice. Analysis of S1 mRNA by DNA microarray and gene expression analysis revealed gene changes in SR-/- that are associated with psychiatric and neurologic disorders, as well as neurodevelopment. The microarray analysis also identified reduced expression of brain derived neurotrophic factor (BDNF) in SR-/- mice. Follow-up analysis by ELISA confirmed a reduction of BDNF protein levels in the S1 of SR-/- mice. Finally, S1 pyramidal neurons in glycine transporter heterozygote (GlyT1+/-) mutants, which display enhanced NMDAR function, had increased dendritic spine density. These results suggest that proper NMDAR function is important for the arborization and spine density of pyramidal neurons in cortex. Moreover, they suggest that NMDAR hypofunction might, in part, be contributing to the dendritic and synaptic changes observed in schizophrenia and highlight this signaling pathway as a potential target for therapeutic intervention., (Copyright © 2011 Elsevier Inc. All rights reserved.)

D-serine is an endogenous neurotransmitter that binds to the NMDA receptor, thereby increasing the affinity for glutamate, and the potential for excitotoxicity. The primary source of D-serine in vivo is enzymatic racemization by serine racemase (SR). Regulation of D-serine in vivo is poorly understood, but is thought to involve a combination of controlled production, synaptic reuptake by transporters, and intracellular degradation by D-amino acid oxidase (DAO). However, SR itself possesses a well-characterized eliminase activity, which effectively degrades D-serine as well. D-serine is increased two-fold in spinal cords of G93A Cu,Zn-superoxide dismutase (SOD1) mice--the standard model of amyotrophic lateral sclerosis (ALS). ALS mice with SR disruption show earlier symptom onset, but survive longer (progression phase is slowed), in an SR-dependent manner. Paradoxically, administration of D-serine to ALS mice dramatically lowers cord levels of D-serine, leading to changes in the onset and survival very similar to SR deletion. D-serine treatment also increases cord levels of the alanine-serine-cysteine transporter 1 (Asc-1). Although the mechanism by which SOD1 mutations increases D-serine is not known, these results strongly suggest that SR and D-serine are fundamentally involved in both the pre-symptomatic and progression phases of disease, and offer a direct link between mutant SOD1 and a glial-derived toxic mediator., (© 2011 The Authors. Journal of Neurochemistry © 2011 International Society for Neurochemistry.)

Glycine and/or D-serine are obligatory coagonists of the N-methyl-D-aspartate receptor (NMDAR). Serine racemase, the D-serine-synthesizing enzyme, is expressed by astrocytes and Müller cells of the retina, but little is known about its role in retinal signalling. In this study, we utilize a serine racemase knockout (SRKO) mouse to explore the contribution of D-serine to inner-retinal function. Retinal tissue levels of D-serine in SRKO mice are reduced by 85%. Whole-cell recordings from SRKO retinal ganglion cells showed markedly reduced coagonist occupancy of NMDARs and consequently a dramatic reduction in the NMDAR component of light-evoked responses. NMDAR currents in SRKOs could be rescued by applying exogenous coagonist, but SRKO ganglion cells still displayed lower NMDA/AMPA receptor ratios than wild-type (WT) controls when the coagonist site was saturated. Despite having abnormalities in synaptic glutamatergic transmission, SRKO mice displayed no obvious signs of visual impairment in behavioural testing. These findings raise interesting questions about the role of D-serine in inner-retinal function and development.

D-Serine, an endogenous co-agonist of the N-methyl-D-aspartate (NMDA) receptor, plays an important role in mammalian brain neurotransmission, via the NMDA receptor. D-Serine is synthesized from L-serine by the pyridoxal-5' phosphate-dependent enzyme serine racemase (SRR), and D-serine is metabolized by D-amino acid oxidase (DAAO). In this study, we measured levels of the neurotransmission related amino acids, d-serine, L-serine, glycine, glutamine and glutamate in the frontal cortex, hippocampus, striatum and cerebellum as well as in peripheral tissues of blood, heart, pancreas, spleen, liver, kidney, testis, epididymis, heart, lung, muscle and eyeball, in wild-type (WT) and Srr-knockout (Srr-KO) mice. Levels of D-serine in the frontal cortex, hippocampus, and striatum of Srr-KO mice were significantly lower than in WT mice, while levels in the cerebellum stayed the same. In contrast, levels of L-serine, glycine, glutamine and glutamate remained the same in all tested brain regions. In vivo microdialysis using free-moving mice showed that extracellular levels of D-serine in the hippocampus of Srr-KO mice were significantly lower than in WT mice while the other amino acid levels remained the same between mice. In peripheral organs, levels of D-serine in the kidney, testis, and muscle of Srr-KO mice were significantly lower than in WT mice. Tissue levels of the other tested amino acids in peripheral organs were not altered. These results suggest that SRR is the major enzyme responsible for D-serine production in the mouse forebrain, and that other pathways of d-serine production may exist in the brain and peripheral organs., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The N-methyl-d-aspartate receptor (NMDAR) and α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptor (AMPAR) are ionotropic glutamate receptors responsible for excitatory neurotransmission in the brain. These excitatory synapses are found on dendritic spines, with the abundance of receptors concentrated at the postsynaptic density (PSD). We utilized two genetic mouse models, the serine racemase knockout (SR-/-) and the glycine transporter subtype 1 heterozygote mutant (GlyT1+/-), to determine how constitutive NMDAR hypo- and hyperfunction, respectively, affect the glutamate receptor composition of the PSD in the hippocampus and prefrontal cortex (PFC). Using cellular fractionation, we found that SR-/- mice had elevated protein levels of NR1 and NR2A NMDAR subunits specifically in the PSD-enriched fraction from the hippocampus, but not from the PFC. There were no changes in the amounts of AMPAR subunits (GluR1, GluR2), or PSD protein of 95 kDa (PSD95) in either brain region. GlyT1+/- mice also had elevated protein expression of NR1 and NR2A subunits in the PSD, as well as an increase in total protein. Moreover, GlyT1+/- mice had elevated amounts of GluR1 and GluR2 in the PSD, and higher total amounts of GluR1. Similar to SR-/- mice, there were no protein changes observed in the PFC. These findings illustrate the complexity of synaptic adaptation to altered NMDAR function., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Background: The unique cell wall of bacteria of the suborder Corynebacterineae is essential for the growth and survival of significant human pathogens including Mycobacterium tuberculosis and Mycobacterium leprae. Drug resistance in mycobacteria is an increasingly common development, making identification of new antimicrobials a priority. Recent studies have revealed potent anti-mycobacterial compounds, the benzothiazinones and dinitrobenzamides, active against DprE1, a subunit of decaprenylphosphoribose 2' epimerase which forms decaprenylphosphoryl arabinose, the arabinose donor for mycobacterial cell wall biosynthesis. Despite the exploitation of Mycobacterium smegmatis in the identification of DprE1 as the target of these new antimicrobials and its use in the exploration of mechanisms of resistance, the essentiality of DprE1 in this species has never been examined. Indeed, direct experimental evidence of the essentiality of DprE1 has not been obtained in any species of mycobacterium., Methodology/principal Findings: In this study we constructed a conditional gene knockout strain targeting the ortholog of dprE1 in M. smegmatis, MSMEG&#95;6382. Disruption of the chromosomal copy of MSMEG&#95;6382 was only possible in the presence of a plasmid-encoded copy of MSMEG&#95;6382. Curing of this "rescue" plasmid from the bacterial population resulted in a cessation of growth, demonstrating gene essentiality., Conclusions/significance: This study provides the first direct experimental evidence for the essentiality of DprE1 in mycobacteria. The essentiality of DprE1 in M. smegmatis, combined with its conservation in all sequenced mycobacterial genomes, suggests that decaprenylphosphoryl arabinose synthesis is essential in all mycobacteria. Our findings indicate a lack of redundancy in decaprenylphosphoryl arabinose synthesis in M. smegmatis, despite the relatively large coding capacity of this species, and suggest that no alternative arabinose donors for cell wall biosynthesis exist. Overall, this study further validates DprE1 as a promising target for new anti-mycobacterial drugs.

α-Methyl-acyl-CoA-racemase (AMACR) deficiency (OMIM 604489) is a rare peroxisomal disorder with a variable age of onset from infancy to late adulthood. We describe a 45-year-old male with a history of seizures who presented with relapsing encephalopathy. Laboratory studies revealed an elevated serum pristanic acid concentration, an elevated pristanic/phytanic acid ratio, as well as the previously described homozygous mutation in the AMACR gene, c.154T>C, consistent with AMACR deficiency. This homozygous mutation is associated with a variable phenotype ranging from neonatal cholestasis to late-onset sensorimotor neuropathy. Dietary pristanic acid restriction was attempted to improve clinical status and the patient has remained in remission for more than 16 months.

A subset of glutamate receptors that are specifically sensitive to the glutamate analog N-methyl-D-aspartate (NMDA) are molecular coincidence detectors, necessary for activity-dependent processes of neurodevelopment and in sensory and cognitive functions. The activity of these receptors is modulated by the endogenous amino acid D-serine, but the extent to which D-serine is necessary for the normal development and function of the mammalian nervous system was previously unknown. Decreased signaling at NMDA receptors has been implicated in the pathophysiology of schizophrenia based on pharmacological evidence, and several human genes related to D-serine metabolism and glutamatergic neurotransmission have been implicated in the etiology of schizophrenia. Here we show that genetically modified mice lacking the ability to produce D-serine endogenously have profoundly altered glutamatergic neurotransmission, and relatively subtle but significant behavioral abnormalities that reflect hyperactivity and impaired spatial memory, and that are consistent with elevated anxiety.

D-Serine is detected in the brain and acts as a coagonist at the "glycine-site" of the NMDA-type glutamate receptor. Although D-serine can be directly produced from L-serine by serine racemase (SR), the relative contribution of SR in D-serine formation in vivo is not known. Pathological roles of brain D-serine mediating NMDA receptor overactivation are suggested in studies using in vitro culture systems. However, we have recently demonstrated the differential SR protein expression in vivo and in culture. Here, we reported an approximately 90% decrease in forebrain D-serine content in SR knock-out (KO) mice. We also found a reduced neurotoxicity induced by NMDA- and Abeta(1-42)- peptide injections into the forebrain in SR KO mice. These results suggest that SR is the major enzyme for D-serine production in the brain, D-serine is the predominant endogenous coagonist of the NMDA receptor in the forebrain, and D-serine may be involved in controlling the extent of NMDA receptor-mediated neurotoxic insults observed in disorders including Alzheimer's disease. The control of SR activity and D-serine level in the brain may lead to a novel strategy for neuroprotection against various neurodegenerative diseases.