Molybdenum Cofactor Sulfurase Research Articles

Studying the role of Bombyx mori molybdenum cofactor sulfurase in Bombyx mori nucleopolyhedrovirus infection.

Molybdenum cofactor sulfurase (MoCoS) is a key gene involved in the uric acid metabolic pathway that activates xanthine dehydrogenase to synthesise uric acid. Uric acid is harmful to mammals but plays crucial roles in insects, one of which is the immune responses. However, the function of Bombyx mori MoCoS in response to BmNPV remains unclear. In this study, BmMoCoS was found to be relatively highly expressed in embryonic development, gonads and the Malpighian tubules. In addition, the expression levels of BmMoCoS were significantly upregulated in three silkworm strains with different levels of resistance after virus infection, suggesting a close link between them. Furthermore, RNAi and overexpression studies showed that BmMoCoS was involved in resistance to BmNPV infection, and its antivirus effects were found to be related to the regulation of uric acid metabolism, which was uncovered by inosine- and febuxostat-coupled RNAi and overexpression. Finally, the BmMoCoS-mediated uric acid pathway was preliminarily confirmed to be a potential target to protect silkworms from BmNPV infection. Overall, this study provides new evidence for elucidating the molecular mechanism of silkworms in response to BmNPV infection and new strategies for the prevention of viral infections in sericulture.

Three cases of xanthinuria identified by gas chromatography/mass spectrometry‐based urine metabolomics

IntroductionEarly diagnosis of patients with urolithiasis or hypouricemia owing to inborn errors of hypoxanthine metabolism is important in preventing renal failure or drug‐induced toxicity.Case presentationWe identified three patients with xanthinuria using gas chromatography/mass spectrometry‐based urine metabolomics: a 72‐year‐old male with bladder stone, a severe hypouricemic 59‐year‐old female with type 2 diabetes mellitus, and an 8‐year and 9‐month‐old female who was first discovered to harbor a mutation in the xanthine dehydrogenase gene using whole‐exome sequencing, but had a normal molybdenum cofactor sulfurase gene. Hydantoin‐5‐propionate was detected in the first and third patients but not in the second, suggesting that the first and second patients had type I and II xanthinuria, respectively.ConclusionGas chromatography/mass spectrometry‐based metabolomics can be used for undiagnosed patients with xanthinuria, identification of the type of xanthinuria without allopurinol loading, and the quick functional evaluation of mutations in the xanthinuria‐related genes.

Phylogenetic relationships of the woodlouse flies (Diptera: Rhinophorinae) and the cluster flies (Diptera: Polleniidae).

Phylogenetic relationships within the oestroid subclades Rhinophorinae (Calliphoridae) and Polleniidae were reconstructed for the first time, applying a Sanger sequencing approach using the two protein-coding nuclear markers CAD (carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase; 1794 bp) and MCS (molybdenum cofactor sulfurase; 2078 bp). Three genera of Polleniidae and nineteen genera of Rhinophorinae were analyzed together with a selection of taxa representing the major lineages of Oestroidea (non-rhinophorine Calliphoridae, Oestridae, Sarcophagidae, Tachinidae). The selected markers provide good resolution and moderate to strong support of the distal branches, but weak support for several deeper nodes. Polleniidae (cluster flies) emerge as monophyletic and their sister-group relationship to Tachinidae is confirmed. Morinia Robineau-Desvoidy as currently circumscribed emerges as paraphyletic with regard to Melanodexia Williston, and Pollenia Robineau-Desvoidy is the sister taxon of the Morinia-Melanodexia clade. We propose a classification with two subfamilies, Moriniinae Townsend (including Morinia, Melanodexia, and Alvamaja Rognes), and Polleniinae Brauer & Bergenstamm (including Pollenia, Dexopollenia Townsend, and Xanthotryxus Aldrich). Anthracomyza Malloch and Nesodexia Villeneuve are considered as Oestroidea incertae sedis pending further study. Rhinophorinae (woodlouse flies) emerge as monophyletic and sister to a clade composed of (Ameniinae + (Ameniinae + Phumosiinae)), and a tribal classification is proposed with the subfamily divided into Rhinophorini Robineau-Desvoidy, 1863 and Phytonini Robineau-Desvoidy, 1863 (the Stevenia-group and the Phyto-group of authors, respectively). Oxytachina Brauer & Bergenstamm, 1891, stat. rev. is resurrected to contain nine Afrotropical rhinophorine species currently assigned to genus Rhinomorinia Brauer & Bergenstamm, 1891: Oxytachina approximata (Crosskey, 1977) comb. nov., O. atra (Bischof, 1904) comb. nov., O. bisetosa (Crosskey, 1977) comb. nov., O. capensis (Brauer & Bergenstamm, 1893) comb. nov., O. scutellata (Crosskey, 1977) comb. nov., O. setitibia (Crosskey, 1977) comb. nov., O. verticalis (Crosskey, 1977) comb. nov., O. vittata Brauer & Bergenstamm, 1891, and O. xanthocephala (Bezzi, 1908) comb. nov.

First phylogenetic analysis of the Nearctic madicolous midges of the genus Androprosopa Mik (Diptera: Thaumaleidae)

Molecular phylogenetic analyses were conducted to infer relationships between the eastern and western Nearctic Androprosopa Mik and amongst the considerably more diverse western Nearctic species. Fresh, molecular-grade material was obtained for all Nearctic Androprosopa species except two Mexican species, An. sonorensis (Arnaud & Boussy) and An. zempoala Sinclair & Huerta, that eluded capture. Molecular sequences from two nuclear protein-coding genes, big zinc finger (BZF) and molybdenum cofactor sulfurase (MCS), were sampled from representatives of several outgroup and ingroup taxa and analyzed phylogenetically using maximum likelihood criteria to confirm identifications of females and immatures using a barcoding approach, test species boundaries among morphologically similar species, and infer relationships among more morphologically disparate groups. Resulting phylogenies suggest the following with significant node (bootstrap) support: (1) the eastern Nearctic Androprosopa species form the sister group to the lineage comprised of all sampled Palearctic thaumaleids, i.e., An. larvata (Mik), An. striata (Okada), and Thaumalea testacea Ruthe; (2) the aforementioned lineage is the sister group to the clade comprised of western Nearctic Androprosopa species; (3) the western Nearctic Androprosopa species form three multispecies lineages, two of which can be further divided into three or more well founded species groups. Our results suggest that Androprosopa as currently defined is paraphyletic. Additionally, we propose several new species groups within the western Nearctic Androprosopa based on molecular and morphological data.

Candidate causative variant for xanthinuria in a Domestic Shorthair cat.

Xanthinuria is a clinically significant form of urolithiasis in cats with poor clinical outcomes and limited treatment options. In humans, xanthinuria has an autosomal recessive mode of inheritance, with variants in xanthine dehydrogenase (XDH) and molybdenum cofactor sulfurase (MOCOS) responsible for cases. While causative genetic variants have not been identified in the domestic cat, a recessive mode of inheritance has been suggested. DNA was extracted from EDTA-stabilised blood obtained from a Domestic Shorthair cat with clinically confirmed xanthinuria. Whole-genome sequencing and variant assessment in XDH and MOCOS identified XDH:c.2042C>T (XDH:p.(A681V)) as a candidate causative variant for xanthinuria in this cat. The variant is located in a highly conserved part of the molybdenum-pterin co-factor domain, responsible for catalysing the hydroxylation of hypoxanthine to xanthine and uric acid. Variants in this domain of XDH have been shown to disrupt enzyme function and to cause xanthinuria in other species. When assessed in the wider cat population, the variant had an allele frequency of 15.8%, with 0.9% of the animals assessed homozygous for the alternative allele. Cats diagnosed with xanthinuria should be tested for this variant to validate its clinical relevance in the wider population.

Deletion of Mocos Induces Xanthinuria with Obstructive Nephropathy and Major Metabolic Disorders in Mice.

Xanthinuria type II is a rare autosomal purine disorder. This recessive defect of purine metabolism remains an under-recognized disorder. Mice with targeted disruption of the molybdenum cofactor sulfurase (Mocos) gene were generated to enable an integrated understanding of purine disorders and evaluate pathophysiologic functions of this gene which is found in a large number of pathways and is known to be associated with autism. Mocos-deficient mice die with 4 weeks of age due to renal failure of distinct obstructive nephropathy with xanthinuria, xanthine deposits, cystic tubular dilation, Tamm-Horsfall (uromodulin) protein (THP) deposits, tubular cell necrosis with neutrophils, and occasionally hydronephrosis with urolithiasis. Obstructive nephropathy is associated with moderate interstitial inflammatory and fibrotic responses, anemia, reduced detoxification systems, and important alterations of the metabolism of purines, amino acids, and phospholipids. Conversely, heterozygous mice expressing reduced MOCOS protein are healthy with no apparent pathology. Mocos-deficient mice develop a lethal obstructive nephropathy associated with profound metabolic changes. Studying MOCOS functions may provide important clues about the underlying pathogenesis of xanthinuria and other diseases requiring early diagnosis.

Multiple variants in XDH and MOCOS underlie xanthine urolithiasis in dogs

Hereditary xanthinuria is a rare autosomal recessive disease caused by missense and loss of function variants in the xanthine dehydrogenase (XDH) or molybdenum cofactor sulfurase (MOCOS) genes. The aim of this study was to uncover variants underlying risk for xanthinuria in dogs. Affected dogs included two Manchester Terriers, three Cavalier King Charles Spaniels, an English Cocker Spaniel, a Dachshund, and a mixed-breed dog. Four putative causal variants were discovered: an XDH c.654G > A splice site variant that results in skipping of exon 8 (mixed-breed dog), a MOCOS c.232G > T splice site variant that results in skipping of exon 2 (Manchester Terriers), a MOCOS p.Leu46Pro missense variant (Dachshund), and a MOCOS p.Ala128Glyfs*30 frameshift variant that results in a premature stop codon (Cavalier King Charles Spaniels and English Cocker Spaniel). The two splice site variants suggest that the regions skipped are critical to the respective enzyme function, though protein misfolding is an alternative theory for loss of function. The MOCOS p.Leu46Pro variant has not been previously reported in human or other animal cases and provides novel data supporting this residue as critical to MOCOS function. All variants were present in the homozygous state in affected dogs, indicating an autosomal recessive mode of inheritance. Allele frequencies of these variants in breed-specific populations ranged from 0 to 0.18. In conclusion, multiple diverse variants appear to be responsible for hereditary xanthinuria in dogs.

Genome-wide association study and inbreeding depression on body size traits in Qira black sheep (Ovis aries).

Qira black sheep is a famous indigenous sheep breed in China. The objectives of this study are to identify candidate genes related to body size, and to estimate the level of inbreeding depression on body size based on runs of homozygosity in Qira black sheep. Here, 188 adult Qira black sheep were genotyped with a high density (630K) SNP chip and genome-wide association study for body weight and body size traits (including withers height, body slanting length, tail length, chest girth, chest width, and chest depth) were performed using an additive linear model. In consequence, 12 genome- and chromosome-wide significant SNPs and, accordingly, six candidate genes involved in muscle differentiation, metabolism and cell processes were identified. Of them, ZNF704 (zinc finger protein 704) was identified for body weight; AK2 (adenylate kinase 2) and PARK2 (parkin RBR E3 ubiquitin protein ligase) for tail length; MOCOS (molybdenum cofactor sulfurase) and ELP2 (elongator acetyltransferase complex subunit 2) for chest width; and MFAP1 (microfibril associated protein 1) for chest girth. Additionally, inbreeding depressions on body size were observed in the current herd. These results will provide insightful understandings into the genetic mechanisms of adult body size, and into the conservation and utilization of Qira black sheep.

A Single Nucleotide Polymorphism Within Molybdenum Cofactor Sulfurase Gene Is Associated With Neuropsychiatric Conditions.

BackgroundMolybdenum cofactor sulfurase (MOCOS) is an enzyme participating in purine metabolism. The aim of current study was to evaluate the role of a single nucleotide polymorphism (SNP) in the coding gene (rs594445) in mood disorders and methamphetamine addiction.MethodsThis SNP was genotyped in 200 persons with methamphetamine addiction, 85 patients with bipolar disorder 1 (BP1), 78 patients with BP2, 33 patients with major depressive disorder (MDD) and 200 age-/sex-matched normal subjects using the tetra-primer amplification-refractory mutation system (ARMS)-PCR technique.ResultsThe rs594445 was associated with methamphetamine addiction in co-dominant model [A/A vs C/C: OR (95% CI) = 0.466 (0.252–0.864), P-value = 0.014; C/A vs C/C: OR (95% CI) = 0.641 (0.418–0.981), P-value = 0.04]. This SNP was also associated with this trait in dominant model [OR (95% CI) = 0.591 (0.398–0.879), P-value = 0.009]. The A allele of rs594445 had a protective role against methamphetamine addiction [A vs C: OR (95% CI) = 0.645 (0.48–0.866), P-value = 0.004]. The rs594445 was associated with BP1 in co-dominant model [C/A vs C/C: OR (95% CI) = 0.423 (0.230–0.778), P-value = 0.005]. However, the associations were insignificant in other inheritance models.ConclusionFinally, there were no significant associations between the mentioned SNP and risk of BP2 or MDD in any inheritance model. The present project highlights the role rs594445 in two psychiatric conditions and implies the presence of common genetic factors for these disorders.

The rs594445 in MOCOS gene is associated with risk of autism spectrum disorder.

Molybdenum cofactor sulfurase (MOCOS) gene encodes an enzyme which is involved in purine metabolism. Recent experiments have shown down-regulation of MOCOS in adult nasal olfactory stem cells of individuals with autism spectrum disorder (ASD). In the current study, we genotyped two single nucleotide polymorphisms (SNPs) within coding regions of MOCOS gene (rs594445 and rs1057251) in 406 ASD patients and 411 age and sex-matched controls. The A allele of the rs594445 SNP was more prevalent among ASD cases compared with controls (OR (95% CI) = 1.33 (1.07-1.64), adjusted P value = 0.02). This SNP was associated with risk of ASD in co-dominant (AA vs. CC: OR (95% CI) = 2.00 (1.22-3.23), adjusted P value = 0.04) and recessive (AA vs. CC + AC: OR (95% CI) = 1.86 (1.16-2.98), adjusted P value = 0.02) models. The other SNP was not associated with risk of ASD in any inheritance model. There was no LD between rs594445 and rs1057251 SNPs (D' = 0.03, r2= 0.14). The C T haplotype (rs594445 and rs1057251, respectively) had a protective role against ASD (OR (95% CI) = 0.76 (0.62-0.92), adjusted P value = 0.02). Other estimated haplotypes distributed equally between cases and controls. Based on the results of current study, the rs594445 SNP might be regarded as a risk locus for ASD in Iranian population.

Insights into stress responses in mandarins triggered by Bacillus subtilis cyclic lipopeptides and exogenous plant hormones upon Penicillium digitatum infection.

Bacillus subtilis CLP extract activates defense gene expression and increases the unique protein production involving in pathways of ISR, SAR, ubiquitin-proteasome system, and glycolysis for stress responses in flavedo tissues. Cyclic lipopeptides (CLPs) of Bacillus subtilis ABS-S14 had ability to activate plant defensive pathways, increase resistance and control green mold rot caused by Penicillium digitatum in mandarin fruit. The current study investigated transcriptional and proteomic data to highlight the unique induction effect of CLPs produced by B. subtilis ABS-S14 on the defense mechanism of mandarins in response to P. digitatum attack, and their differences from those following the exogenous plant hormone application. The proteomic patterns of the flavedo tissues as affected by Bacillus CLP extract, salicylic acid (SA), methyl jasmonate (MeJA), and ethephon (Et) were explored. qPCR analysis revealed the great effects of CLP extract in enhancing the transcription of PAL, ACS1, GLU, POD, and PR1. Tryptic peptides by LC-MS analysis between treatments with and without fungal infection were compared. B. subtilis CLP extract empowered the plant's immune response to wound stress by the significant production of calmodulin-binding receptor-like cytoplasmic kinase 2, molybdenum cofactor sulfurase, and NAD+-dependent glyceraldehyde-3-phosphate dehydrogenase. Ubiquitin carrier protein abundance was developed only in the treated flavedo with CLP extract coupled with P. digitatum infection. The gene expression and overall proteome findings involving pathways of ubiquitin proteasome system, ISR, SAR, and energy production provide a new insight into the molecular mechanisms of the antagonist B. subtilis ABS-S14 inducing resistance against green mold in mandarins.

Arabidopsis molybdenum cofactor sulfurase ABA3 contributes to anthocyanin accumulation and oxidative stress tolerance in ABA-dependent and independent ways

Arabidopsis ABA3 is an enzyme involved in the synthesis of the sulfurated form of the molybdenum (Mo) cofactor (MoCo), which is required for the enzymatic activity of so-called Mo enzymes such as aldehyde oxidase (AO) and xanthine dehydrogenase (XDH). It has been reported that AO and XDH are essential for the biosynthesis of the bioactive compounds, ABA and allantoin, respectively. However, aba3 mutants often exhibit pleiotropic phenotypes that are not explained by defects in ABA and/or allantoin biosynthesis, leading us to hypothesize that ABA3 regulates additional metabolic pathways. To reveal the currently unidentified functions of ABA3 we compared transcriptome and metabolome of the Arabidopsis aba3 mutant with those of wild type and a typical ABA-deficient mutant aba2. We found that endogenous levels of anthocyanins, members of the flavonoid group, were significantly lower in the aba3 mutant than in the wild type or the aba2 mutant under oxidative stress. In contrast, mutants defective in the AO and XDH holoenzymes accumulated significantly higher levels of anthocyanins when compared with aba3 mutant under the same conditions. Our findings shed light on a key role of ABA3 in the ABA- and allantoin-independent accumulation of anthocyanins during stress responses.

Thiopurine-induced toxicity is associated with dysfunction variant of the human molybdenum cofactor sulfurase gene (xanthinuria type II)

BackgroundThe aim of our study was to identify the genetic background of thiopurine-induced toxicity in a patient with a wild-type thiopurine methyltransferase genotype and activity. A 38-year-old Caucasian woman presented with cutaneous necrotizing vasculitis pancytopenia one month after starting azathioprine therapy. MethodsDuring a routine biochemical follow-up of the patient, undetectable serum uric acid (<10 μl) was observed. A high performance liquid chromatography analysis of urinary purines revealed increased levels of xanthine (137 mmol/mol creatinine). The suspected diagnosis of hereditary xanthinuria, a rare autosomal recessive disorder of the last two steps of purine metabolism, was confirmed by sequence analysis. ResultsAn analysis of XDH/XO and AOX1 revealed common polymorphisms, while analysis of the MOCOS gene identified a rare homozygous variant c.362C > T. Dysfunction of this variant was confirmed by significantly decreased xanthine dehydrogenase/oxidase activity in the patient's plasma (<2% of control mean activity). ConclusionsWe present a biochemical, enzymatic, and molecular genetic case study suggesting an important association between a hitherto undescribed dysfunction variant in the MOCOS gene and thiopurine-induced toxicity. The identified variant c.362C > T results in slower thiopurine metabolism caused by inhibition of 6-mercaptopurine oxidation (catabolism) to 6-thioxanthine and 6-thiouric acid, which increases the formation of the nucleotide 6-thioguanine, which is toxic. This is the first clinical case to identify the crucial role of the MOCOS gene in thiopurine intolerance and confirm the impact of genetic variability of purine enzymes on different therapeutic outcomes in patients undergoing thiopurine treatment.

A frameshift mutation in MOCOS is associated with familial renal syndrome (xanthinuria) in Tyrolean Grey cattle.

BackgroundRenal syndromes are occasionally reported in domestic animals. Two identical twin Tyrolean Grey calves exhibited weight loss, skeletal abnormalities and delayed development associated with kidney abnormalities and formation of uroliths. These signs resembled inherited renal tubular dysplasia found in Japanese Black cattle which is associated with mutations in the claudin 16 gene. Despite demonstrating striking phenotypic similarities, no obvious presence of pathogenic variants of this candidate gene were found. Therefore further analysis was required to decipher the genetic etiology of the condition.ResultsThe family history of the cases suggested the possibility of an autosomal recessive inheritance. Homozygosity mapping combined with sequencing of the whole genome of one case detected two associated non-synonymous private coding variants: A homozygous missense variant in the uncharacterized KIAA2026 gene (g.39038055C > G; c.926C > G), located in a 15 Mb sized region of homozygosity on BTA 8; and a homozygous 1 bp deletion in the molybdenum cofactor sulfurase (MOCOS) gene (g.21222030delC; c.1881delG and c.1782delG), located in an 11 Mb region of homozygosity on BTA 24. Pathogenic variants in MOCOS have previously been associated with inherited metabolic syndromes and xanthinuria in different species including Japanese Black cattle. Genotyping of two additional clinically suspicious cases confirmed the association with the MOCOS variant, as both animals had a homozygous mutant genotype and did not show the variant KIAA2026 allele. The identified genomic deletion is predicted to be highly disruptive, creating a frameshift and premature termination of translation, resulting in severely truncated MOCOS proteins that lack two functionally essential domains. The variant MOCOS allele was absent from cattle of other breeds and approximately 4% carriers were detected among more than 1200 genotyped Tyrolean Grey cattle. Biochemical urolith analysis of one case revealed the presence of approximately 95% xanthine.ConclusionsThe identified MOCOS loss of function variant is highly likely to cause the renal syndrome in the affected animals. The results suggest that the phenotypic features of the renal syndrome were related to an early onset form of xanthinuria, which is highly likely to lead to the progressive defects. The identification of the candidate causative mutation thus enables selection against this pathogenic variant in Tyrolean Grey cattle.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-016-0904-4) contains supplementary material, which is available to authorized users.

Olfactory stem cells reveal MOCOS as a new player in autism spectrum disorders.

With an onset under the age of 3 years, autism spectrum disorders (ASDs) are now understood as diseases arising from pre- and/or early postnatal brain developmental anomalies and/or early brain insults. To unveil the molecular mechanisms taking place during the misshaping of the developing brain, we chose to study cells that are representative of the very early stages of ontogenesis, namely stem cells. Here we report on MOlybdenum COfactor Sulfurase (MOCOS), an enzyme involved in purine metabolism, as a newly identified player in ASD. We found in adult nasal olfactory stem cells of 11 adults with ASD that MOCOS is downregulated in most of them when compared with 11 age- and gender-matched control adults without any neuropsychiatric disorders. Genetic approaches using in vivo and in vitro engineered models converge to indicate that altered expression of MOCOS results in neurotransmission and synaptic defects. Furthermore, we found that MOCOS misexpression induces increased oxidative-stress sensitivity. Our results demonstrate that altered MOCOS expression is likely to have an impact on neurodevelopment and neurotransmission, and may explain comorbid conditions, including gastrointestinal disorders. We anticipate our discovery to be a fresh starting point for the study on the roles of MOCOS in brain development and its functional implications in ASD clinical symptoms. Moreover, our study suggests the possible development of new diagnostic tests based on MOCOS expression, and paves the way for drug screening targeting MOCOS and/or the purine metabolism to ultimately develop novel treatments in ASD.

Cloning and functional validation of molybdenum cofactor sulfurase gene from Ammopiptanthus nanus.

The molybdenum cofactor sulfurase gene ( AnMCSU ) was cloned from xerophytic desert plant Ammopiptanthus nanus and validated for its function of tolerance toward abiotic stresses by heterologous expression in Arabidopsis thaliana. Molybdenum cofactor sulfurase participates in catalyzing biosynthesis of abscisic acid, which plays a crucial role in the response of plants to abiotic stresses. In this study, we cloned molybdenum cofactor sulfurase gene (AnMCSU) from a super-xerophytic desert plant, Ammopiptanthus nanus, by using rapid amplification of cDNA ends method. This gene has a total length of 2544 bp, with a 5'- and a 3'-untranslated region of 167 and 88 bp, and an open reading frame of 2289 bp, which encodes an 84.85 kDa protein of 762 amino acids. The putative amino acid sequence shares high homology and conserved amino acid residues crucial for the function of molybdenum cofactor sulfurases with other leguminous species. The encoded protein of the AnMCSU gene was located in the cytoplasm by transient expression in Nicotiana benthamiana. The result of real-time quantitative PCR showed that the expression of the AnMCSU gene was induced by heat, dehydration, high salt stresses, and ABA induction, and inhibited by cold stress. The heterologous expression of the AnMCSU gene significantly enhanced the tolerance of Arabidopsis thaliana to high salt, cold, osmotic stresses, and abscisic acid induction. All these results suggest that the AnMCSU gene might play a crucial role in the adaptation of A. nanus to abiotic stress and has potential to be applied to transgenic improvement of commercial crops.

Using Next-Generation Sequencing to Identify a Mutation in Human MCSU that is Responsible for Type II Xanthinuria

Background: Hypouricemia is caused by various diseases and disorders, such as hepatic failure, Fanconi renotubular syndrome, nutritional deficiencies and genetic defects. Genetic defects of the molybdoflavoprotein enzymes induce hypouricemia and xanthinuria. Here, we identified a patient whose plasma and urine uric acid levels were both extremely low and aimed to identify the pathogenic gene and verify its mechanism. Methods: Using next-generation sequencing (NGS), we detected a mutation in the human molybdenum cofactor sulfurase (MCSU) gene that may cause hypouricemia. We cultured L02 cells, knocked down MCSU with RNAi, and then detected the uric acid and MCSU concentrations, xanthine oxidase (XOD) and xanthine dehydrogenase (XDH) activity levels, and xanthine/hypoxanthine concentrations in cell lysates and culture supernatants. Results: The NGS results showed that the patient had a mutation in the human MCSU gene. The in vitro study showed that RNAi of MCSU caused the uric acid, human MCSU concentrations, the XOD and XDH activity levels among cellular proteins and culture supernatants to be extremely low relative to those of the control. However, the xanthine/hypoxanthine concentrations were much higher than those of the control. Conclusions: We strongly confirmed the pathogenicity of the human MCSU gene.

Barley molybdenum cofactor sulfurase (MCSU): sequencing, modeling, and its comparison to other higher plants

Molybdenum cofactor sulfurases (MCSUs) are important enzymes for plant development and response to environmental queues, including processes such as nitrogen metabolism and regulation of the abscisic acid levels in plant tissues. We cloned and sequenced MCSU gene from barley and performed in silico comparison with rice, tomato, and Arabidopsis. Physico-chemical properties and subcellular predictions were found to be similar in different plant species. All MCSUs had three critical domains: aminotransferase class-V (Pfam: PF00266), MOSC N-terminal beta barrel (Pfam: PF03476), and MOSC (Pfam: PF03473). Secondary structure analysis revealed that random coils were the most abundant, followed by α-helices and extended strands. Predicted binding sites of MCSUs were different in barley and Arabidopsis , whereas rice and tomato showed the same pattern. A conserved triple-cysteine motif was detected in all MCSUs with cys438-cys440-cys445, cys431-cys433-cys438, cys428-cys430-cys435, and cys425-cys427-cys432 in barley, rice, Arabidopsis, and tomato, respectively. Furthermore, a 3D structure analysis indicated that structural divergences were present in all MCSUs, even in the core domain structure. Phylogenetic analysis of MCSUs revealed that monocot-dicot divergence was clearly observed with high bootstrap values. The results of this study will contribute to the understanding of MCSU genes and proteins in plants. The data of this study will also constitute a scientific basis for wet-lab and in silico studies of MCSUs.

Overexpression of EsMcsu1 from the halophytic plant Eutrema salsugineum promotes abscisic acid biosynthesis and increases drought resistance in alfalfa (Medicago sativa L.).

The stress phytohormone abscisic acid (ABA) plays pivotal roles in plants' adaptive responses to adverse environments. Molybdenum cofactor sulfurases influence aldehyde oxidase activity and ABA biosynthesis. In this study, we isolated a novel EsMcsu1 gene encoding a molybdenum cofactor sulfurase from Eutrema salsugineum. EsMcus1 transcriptional patterns varied between organs, and its expression was significantly upregulated by abiotic stress or ABA treatment. Alfalfa plants that overexpressed EsMcsu1 had a higher ABA content than wild-type (WT) plants under drought stress conditions. Furthermore, levels of reactive oxygen species (ROS), ion leakage, and malondialdehyde were lower in the transgenic plants than in the WT plants after drought treatment, suggesting that the transgenic plants experienced less ROS-mediated damage. However, the expression of several stress-responsive genes, antioxidant enzyme activity, and osmolyte (proline and total soluble sugar) levels in the transgenic plants were higher than those in the WT plants after drought treatment. Therefore, EsMcsu1 overexpression improved drought tolerance in alfalfa plants by activating a series of ABA-mediated stress responses.

Sulfate availability affects ABA levels and germination response to ABA and salt stress in Arabidopsis thaliana

Sulfur-containing compounds play a critical role in the response of plants to abiotic stress factors including drought. The phytohormone abscisic acid (ABA) is the key regulator of responses to drought and high-salt stress. However, our knowledge about interaction of S-metabolism and ABA biosynthesis is scarce. Here we report that sulfate supply affects synthesis and steady-state levels of ABA in Arabidopsis wild-type seedlings. By using different mutants of the sulfate uptake and reduction pathway, we confirmed the impact of sulfate supply on steady-state ABA content in Arabidopsis and demonstrated that this impact was due to cysteine availability. Loss of the chloroplast sulfate transporter3;1 function (sultr3;1) resulted in significantly decreased aldehyde oxidase (AO) activity and ABA levels in seedlings and seeds. These mutant phenotypes could be reverted by exogenous application of cysteine or ectopic expression of SULTR3;1. In addition the sultr3;1 mutant showed a decrease of xanthine dehydrogenase activity, but not of nitrate reductase, strongly indicating that in seedlings cysteine availability limits activity of the molybdenum co-factor sulfurase, ABA3, which requires cysteine as the S-donor for sulfuration. Transcription of ABA3 and NCED3, encoding another key enzyme of the ABA biosynthesis pathway, was regulated by S-supply in wild-type seedlings. In contrast, ABA up-regulated the transcript level of SULTR3;1 and other S-metabolism-related genes. Our results provide evidence for a significant co-regulation of S-metabolism and ABA biosynthesis that operates to ensure sufficient cysteine for AO maturation and highlights the importance of sulfur for stress tolerance of plants.