Clinical and Functional Characterization of a Novel URAT1 Dysfunctional Variant in a Pediatric Patient with Renal Hypouricemia

Renal hypouricemia (RHUC) is caused by an inherited defect in the main (reabsorptive) renal urate transporters, URAT1 and GLUT9. RHUC is characterized by decreased concentrations of serum uric acid and an increase in its excretion fraction. Patients suffer from hypouricemia, hyperuricosuria, urolithiasis, and even acute kidney injury. We report the clinical, biochemical, and genetic findings of a pediatric patient with hypouricemia. Sequencing analysis of the coding region of SLC22A12 and SLC2A9 and a functional study of a novel RHUC1 variant in the Xenopus expression system were performed. The proband showed persistent hypouricemia (67–70 µmol/L; ref. range 120–360 µmol/L) and hyperuricosuria (24–34%; ref. range 7.3 ± 1.3%). The sequencing analysis identified common non-synonymous allelic variants c.73G > A, c.844G > A, c.1049C > T in the SLC2A9 gene and rare variants c.973C > T, c.1300C > T in the SLC22A12 gene. Functional characterization of the novel RHUC associated c.973C > T (p. R325W) variant showed significantly decreased urate uptake, an irregular URAT1 signal on the plasma membrane, and reduced cytoplasmic staining. RHUC is an underdiagnosed disorder and unexplained hypouricemia warrants detailed metabolic and genetic investigations. A greater awareness of URAT1 and GLUT9 deficiency by primary care physicians, nephrologists, and urologists is crucial for identifying the disorder.

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Cloning and functional characterization of an uncoupling protein homolog in hummingbirds

Physiological Genomics ◽

10.1152/physiolgenomics.2001.5.3.137 ◽

2001 ◽

Vol 5 (3) ◽

pp. 137-145 ◽

Cited By ~ 56

Author(s):

CLAUDIA R. VIANNA ◽

THILO HAGEN ◽

CHEN-YU ZHANG ◽

ERIC BACHMAN ◽

OLIVIER BOSS ◽

...

Keyword(s):

Uncoupling Protein ◽

Expression System ◽

Functional Characterization ◽

Pectoral Muscle ◽

Mitochondrial Fraction ◽

Mrna Levels ◽

Coding Region ◽

Reading Frame ◽

Rapid Amplification

The cDNA of an uncoupling protein (UCP) homolog has been cloned from the swallow-tailed hummingbird, Eupetomena macroura. The hummingbird uncoupling protein (HmUCP) cDNA was amplified from pectoral muscle (flight muscle) using RT-PCR and primers for conserved domains of various known UCP homologs. The rapid amplification of cDNA ends (RACE) method was used to complete the cloning of the 5′ and 3′ ends of the open reading frame. The HmUCP coding region contains 915 nucleotides, and the deduced protein sequence consists of 304 amino acids, being ∼72, 70, and 55% identical to human UCP3, UCP2, and UCP1, respectively. The uncoupling activity of this novel protein was characterized in yeast. In this expression system, the 12CA5-tagged HmUCP fusion protein was detected by Western blot in the enriched mitochondrial fraction. Similarly to rat UCP1, HmUCP decreased the mitochondrial membrane potential as measured in whole yeast by uptake of the fluorescent potential-sensitive dye 3′,3-dihexyloxacarbocyanine iodide. The HmUCP mRNA is primarily expressed in skeletal muscle, but high levels can also be detected in heart and liver, as assessed by Northern blot analysis. Lowering the room’s temperature to 12–14°C triggered the cycle torpor/rewarming, typical of hummingbirds. Both in the pectoral muscle and heart, HmUCP mRNA levels were 1.5- to 3.4-fold higher during torpor. In conclusion, this is the first report of an UCP homolog in birds. The data indicate that HmUCP has the potential to function as an UCP and could play a thermogenic role during rewarming.

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Harnessing a Transient Gene Expression System in Nicotiana benthamiana to Explore Plant Agrochemical Transporters

Plants ◽

10.3390/plants10030524 ◽

2021 ◽

Vol 10 (3) ◽

pp. 524

Author(s):

Bingqi Wu ◽

Zhiting Chen ◽

Xiaohui Xu ◽

Ronghua Chen ◽

Siwei Wang ◽

...

Keyword(s):

Gene Expression ◽

Transient Expression ◽

Nicotiana Benthamiana ◽

Heterologous Gene Expression ◽

Expression System ◽

Functional Characterization ◽

Transient Gene Expression ◽

High Mobility ◽

Gene Expression System

Functional characterization of plant agrichemical transporters provided an opportunity to discover molecules that have a high mobility in plants and have the potential to increase the amount of pesticides reaching damage sites. Agrobacterium-mediated transient expression in tobacco is simple and fast, and its protein expression efficiency is high; this system is generally used to mediate heterologous gene expression. In this article, transient expression of tobacco nicotine uptake permease (NtNUP1) and rice polyamine uptake transporter 1 (OsPUT1) in Nicotiana benthamiana was performed to investigate whether this system is useful as a platform for studying the interactions between plant transporters and pesticides. The results showed that NtNUP1 increases nicotine uptake in N. benthamiana foliar discs and protoplasts, indicating that this transient gene expression system is feasible for studying gene function. Moreover, yeast expression of OsPUT1 apparently increases methomyl uptake. Overall, this method of constructing a transient gene expression system is useful for improving the efficiency of analyzing the functions of plant heterologous transporter-encoding genes and revealed that this system can be further used to study the functions of transporters and pesticides, especially their interactions.

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Rhinella marina oocytes: a suitable alternative expression system for functional characterization of aquaglyceroporins

Scientific Reports ◽

10.1038/s41598-018-37069-6 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 2

Author(s):

Vania Rojas ◽

Yulexi Y. Ortiz ◽

Sheridan Rodríguez ◽

Vladimir Araque ◽

Alexis Rodríguez-Acosta ◽

...

Keyword(s):

Expression System ◽

Functional Characterization ◽

Suitable Alternative ◽

Rhinella Marina ◽

Alternative Expression

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Functional Characterization of Glycosylation-Deficient Human P-Glycoprotein Using A Vaccinia Virus Expression System

The Journal of Membrane Biology ◽

10.1007/s002320001020 ◽

2000 ◽

Vol 173 (3) ◽

pp. 203-214 ◽

Cited By ~ 72

Author(s):

J.J. Gribar ◽

M. Ramachandra ◽

C.A. Hrycyna ◽

S. Dey ◽

S.V. Ambudkar

Keyword(s):

Vaccinia Virus ◽

Expression System ◽

Functional Characterization ◽

P Glycoprotein ◽

Virus Expression

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Identification and functional characterization of a missense mutation in resistin in two patients with severe obesity and insulin resistance

Acta Endocrinologica ◽

10.1530/eje-10-1080 ◽

2011 ◽

Vol 164 (6) ◽

pp. 927-936 ◽

Cited By ~ 2

Author(s):

Sigri Beckers ◽

Fenna de Freitas ◽

Doreen Zegers ◽

An Verrijken ◽

Armand V Peeters ◽

...

Keyword(s):

Missense Mutation ◽

Functional Characterization ◽

Mutant Protein ◽

Morbidly Obese ◽

Male Body ◽

Coding Region ◽

Obese Adults ◽

Obese Mother

ObjectiveIn this study, we hypothesized that mutations in the resistin encoding gene, RETN, may cause a monogenic form of obesity.Design/methodsWe screened the coding region of RETN in 81 morbidly obese adults, 263 overweight and obese children/adolescents, and 116 healthy lean subjects. In vitro experiments include qPCR, ELISA, and western blot for WT and mutant resistin transfected into 3T3-L1 adipocytes.ResultsMutation analysis identified five sequence variants in our patient populations: 3′-UTR +87 G/A, 3′-UTR +100 A/G, T73T, IV3-61 C/A, and C78S. In our control population, we only found the 3′-UTR +87 G/A variant. We started functional experiments for the C78S mutation that was found in a 20-year-old obese male (body mass index (BMI)=39.7 kg/m2) and his obese mother (BMI=31.9 kg/m2). In vitro testing demonstrated that the mutation does not impair mRNA expression. We identified a 100-fold lower extracellular protein concentration for mutant resistin compared with WT levels using a resistin ELISA on cell culture medium (P=4.87×10−6). We also detected a decreased intracellular concentration for the mutant protein (tenfold lower relative levels, P=0.007). The plasma resistin levels of the proband and his mother, however, did not differ significantly from lean control individuals.ConclusionsIn conclusion, we identified the first missense mutation in resistin in a morbidly obese proband and his obese mother. Functional testing of the mutant protein suggests that the C78S mutant protein is degraded, possibly resulting in a decreased extracellular concentration, which may predispose to obesity.

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