Intra-Laboratory Validation of Alpha-Galactosidase Activity Measurement in Dietary Supplements.

INTRODUCTION: Alpha-galactosidase (α-Gal) is an enzyme responsible for the hydrolyzation of glycolipids and glycoprotein commonly found in dietary sources. More than 20% of the general population suffers from abdominal pain or discomfort caused by intestinal gas and by indigested or partially digested food residuals. Therefore, α-Gal is used in dietary supplements to reduce intestinal gases and help complex food digestion. Marketed enzyme-containing dietary supplements must be produced in accordance with the Food and Drug Administration (FDA) regulations for Current Good Manufacturing Practice (cGMPs). AIM: in this work we illustrated the process used to develop and validate a spectrophotometric enzymatic assay for α-Gal activity quantification in dietary supplements. METHODS: The validation workflow included an initial statistical-phase optimization of materials, reagents, and conditions, and subsequently a comparative study with another fluorimetric assay. A final validation of method performance in terms of specificity, linearity, accuracy, intermediate-precision repeatability, and system precision was then executed. RESULTS AND CONCLUSIONS: The proven method achieved good performance in the quantitative determination of α-Gal activity in commercial food supplements in accordance with the International Council for Harmonisation of Technical Requirements for Pharmaceuticals (ICH) guidelines and is suitable as a rapid in-house quality control test.

In-Depth Glycan Characterization of Therapeutic Glycoproteins by Stepwise PGC SPE and LC-MS/MS.

Glycosylation of biologics, an important factor in pharmacological functions such as efficacy, safety, and biological activity, is easily affected by subtle changes in the cellular environment. Therefore, comprehensive and in-depth glycan characterization of therapeutic glycoproteins should be performed to ensure product quality and process consistency, but it is analytically challenging due to glycan microheterogeneity occurring in the glycan biosynthesis pathway. LC-based chromatographic separation combined with mass spectrometry (MS) has been widely used as a prominent tool for the qualitative and quantitative analysis of glycosylation of therapeutic glycoproteins. However, prior to LC/MS analysis, glycans are selectively captured and fractionated by solid-phase extraction (SPE) utilizing physicochemical characteristics for comprehensive characterization of a wide range of glycan heterogeneity on glycoengineered therapeutic proteins. In particular, porous graphitized carbon (PGC) SPE has been employed as a useful technique for the fractionation of native glycans having different sizes and polarities. Here, we describe a systematic method for comprehensive glycan characterization of therapeutic proteins using stepwise PGC SPE and LC/MS.

Magnetic Resonance Imaging Findings Related to Stroke Risk in Japanese Patients With Fabry Disease.

Background and Purpose- Stroke is the most frequent severe clinical event in patients with Fabry disease. We aimed to evaluate the cerebral magnetic resonance imaging findings of patients with Fabry disease and assess their association with future stroke risk after enzyme replacement therapy (ERT) induction. Methods- We retrospectively reviewed the magnetic resonance imaging findings of 25 patients with Fabry disease. Of these, 12 adult patients without prior stroke or ERT were enrolled to evaluate the association between baseline magnetic resonance imaging findings and stroke occurrence after ERT initiation. We assessed white matter hyperintensities, periventricular hyperintensities, and basilar artery diameter as neuroimaging markers. Results- The mean age of participants was 38.8±16.8 years. Fourteen patients (56.0%) were women. White matter hyperintensities and periventricular hyperintensities were observed in 15 and 13 cases, respectively. The mean basilar artery diameter was 3.2±0.55 mm. Two patients demonstrated old infarct lesions. Three of 12 patients in whom ERT was initiated had symptomatic stroke after baseline magnetic resonance imaging. Of these, 2 developed stroke within 6-month post-ERT initiation. The baseline basilar artery diameter was larger in patients who developed stroke than in those who did not (4.0±0.40 versus 2.9±0.49 mm, P=0.02). Conclusions- Basilar artery diameter may be associated with stroke risk after ERT initiation among Japanese patients with Fabry disease.

Genotype⁻Phenotype Correlation in a New Fabry-Disease-Causing Mutation.

Background: Fabry disease (FD) is a rare X-linked inherited lysosomal storage disorder caused by α-galactosidase A deficiency leading to intracellular glycosphingolipid accumulation. FD manifestation is multisystem, and can differ depending on disease-related genetic variants. Currently, more than 700 different FD-causing mutations have been identified in the human GLA gene. We identified a novel mutation in a Lithuanian family with classical manifestations of Fabry disease, revealing severe effects to the cardiovascular systems of heterozygous women. Case presentation: A 49-year-old woman underwent echocardiography due to progressive dyspnea that lasted seven years, reduced physical activity, and periodic cardiac arrhythmia. Echocardiography revealed left ventricular hypertrophy with normal diastolic function. The patient had experienced acroparesthesia in her upper limbs and abdominal pain since childhood, and in the last decade had experienced mild proteinuria without renal failure. Her renal biopsy was typical for Fabry disease. The patient's brain magnetic resonance imaging (MRI) (T2 flair) showed white matter hyperintensities lesions. DNA sequencing of the proband, her mother and one of her sons showed a novel GLA gene exon 2 mutation, c.270C>G (p.Cys90Trp). All three patients had decreased α-galactosidase A activity and specific FD manifestations. Conclusion: A novel GLA mutation, c.270C>G (p.Cys90Trp), was found in a Lithuanian family with a classical form of Fabry disease in heterozygous women with predominant cardiac involvement. However, the exact manifestation of this mutation is still unclear as it is newly reported and further research must be done.

[The unusual couple: a clinical case of coexistence between aHUS and Fabry's disease].

Atypical hemolytic-uremic syndrome (aHUS) is a rare, potentially lethal (1-4) systemic disorder, capable of affecting both adults and children, causing thrombotic microangiopathy (TMA) (5) that leads to the formation of thrombus within small blood vessels with multiple organ failure. The pathogenesis of the aHUS is part of a sort of chronic and uncontrolled activation of the complement system by genetic mutation of some proteins usually responsible for its self-regulation (6,7). Today, the rapid diagnosis of the disease and the timely start of treatment with eculizumab, improve outcomes of renal failure, stroke and heart attack (8-10). Fabry disease is a rare tesaurismosis, X linked, due to the deficiency of the lysosomal enzyme alpha-galactosidase A (11-13), necessary for the physiological catabolism of glycosphingolipids. Multisystem clinical manifestations lead to a serious degenerative pathology. The diagnostic suspicion based on anamnesis and careful research of the symptoms and then confirmed by the enzymatic dosage of alpha galactosidase or by molecular analysis, allows the early treatment of the patient with enzyme replacement therapy, guaranteeing the resolution and/or slowing down the evolution of the disease, especially in the brain, heart and kidneys. In this report, we describe the clinical case of a patient who is a carrier of both rare diseases.

Detection of Enzymes, Viruses, and Bacteria Using Glucose Meters.

We have developed innovative assays that can detect enzymes rapidly. Paracetamol- or catechol-bearing compounds, when exposed to their respective enzymes, released paracetamol or catechol, which can be detected using a standard glucose meter. This approach was used to detect a number of diverse analytes that include enzymes such as ß-galactosidase and α-mannosidase and pathogens such as influenza viruses, Streptococcus pneumoniae, and E. coli rapidly. The limit of detection for all analytes was extremely low and clinically relevant for influenza viruses. We also demonstrate that glucose oxidase or glucose dehydrogenase is not required because the paracetamol gets oxidized directly on the electrode surface. This indicates that test strips without glucose oxidase or dehydrogenase can be used, and we can detect analytes in the presence of high levels of background glucose. We demonstrate this unique nature of the assay to detect paracetamol in simulated urine and sheep blood without background interference of intrinsic glucose, indicating that glucose meters can be used to detect nonglucose analytes without background glucose interference.

Proteomic analysis of coffee grains exposed to different drying process.

Many biochemical events occur inside grains during post-harvest processes. Several methods have been developed to relate the chemical composition of the coffee grain to the beverage quality, including identification of possible molecular markers for flavor characterizing. This study was aimed at evaluating the changes in the proteomic profile of pulped and natural C. arabica grains dried in a yard or dryer at 60°C. It was observed that fruits dried in a dryer at 60°C showed an altered proteomic profile, with a reduction in the most abundant proteins compared to those yard-dried grains. Among the identified proteins, those involved in the metabolism of sugars and stress response were highlighted. Results have shown that post-harvest processes that impact coffee quality are related to changes in protein abundance, indicating that proteomic analysis may be effective in the identification of biochemical changes in coffee grains subjected to different post-harvest processes.

59-year-old female with breathlessness.

CLINICAL INTRODUCTION: A 59-year-old female underwent an electrocardiogram (ECG) and echocardiographic screening. Her brother died at quite a young age of kidney failure. Resting ECG showed borderline voltage criteria for left ventricular hypertrophy (LVH), with marked widespread T-wave inversion. Echocardiogram was normal, but in consideration of exertional breathlessness and abnormal baseline ECG, she underwent a coronary angiogram, which showed unobstructed coronaries. She was then referred to have a cardiac MR (CMR) for further characterisation. CMR images were acquired with a 1.5 T scanner and the imaging protocol included Steady-State Free Precession (SSFP) cine images (Figure 1A) as well as late gadolinium enhancement (LGE) images in the long-axis and short-axis planes covering the whole left ventricle (Figure 1B). In addition, native and postcontrast T1 mapping (Modified Look-Locker (MOLLI)) images were acquired for further tissue characterisation (Figure 1C and D, respectively). QUESTION: What is the most likely diagnosis based on CMR findings? Anderson-Fabry's disease (AFD)Cardiac amyloidosisGenotype (+), phenotype (-) hypertrophic cardiomyopathy (HCM)Myocardial iron overloadNormal heart.

Múltiples quistes parapiélicos en la enfermedad de Fabry / Multiple parapelvic cysts in Fabry disease

La enfermedad de Fabry es una enfermedad de depósito lisosomal de carácter hereditario, ligada al cromosoma X, causado por el déficit de la enzima alfa-galactosidasa A (alfa-GLA A), lo que conduce a la acumulación de glicoesfingolípidos, principalmente globotriaosilceramida, en los tejidos. Es una enfermedad poco prevalente, y con muy bajo índice de sospecha, por lo que, generalmente, existe un retraso en el diagnóstico y en el tratamiento. Presentamos un caso de un paciente varón afecto de la enfermedad de Fabry, que presentaba múltiples quistes parapiélicos e insuficiencia renal, sin presentar angioqueratomas. El estudio genético mostró una mutación en el gen de alfa-GLA A que no ha sido descrita previamente en el registro de mutaciones, y de novo, ya que no se encontró en otros familiares, además que no fue trasmitida a la descendencia. La presencia de múltiples quistes parapiélicos y su peculiar aspecto fue lo que hizo sospechar el diagnóstico de la enfermedad (AU)

Fabry disease is an inherited, X-linked lysosomal storage disorder caused by deficiency of the enzyme alpha galactosidase A (alpha-GLA A), which leads to glycosphingolipid accumulation, mainly globotriaosylceramide, in tissues. Disease prevalence and the index of suspicion are both low, which tends to result in delayed diagnosis and treatment. We present the case of a male Fabry disease patient who manifested no angiokeratoma lesions but presented multiple parapelvic cysts and renal failure. The genetic study revealed an alpha-GLA A gene mutation that had not been recorded in the mutations registry. The de novo mutation was not found in his relatives and it was not transmitted to his offspring. The large number and peculiar appearance of the parapelvic cysts led to the diagnosis (AU)

Comparación de los pacientes de un registro español de enfermedad de Fabry en dos periodos de tiempo / Comparison of patients from a Spanish Registry of Fabry disease in two periods

Background and objective: Fabry disease (FD) is a rare X-linked lysosomal storage disorder caused by a deficiency of the enzyme alpha-galactosidase A, that leads to multiorgan dysfunction and premature death. Data from the first 24 Spanish patients enrolled on the Fabry Outcome Survey (FOS) were published in 2004, with a significant increase in the number of patients since then. This manuscript analyzes whether the clinical profile or diagnosis of these patients between the 2 periods has changed. Patients and methods: In 2009 the FOS included data from 92 patients. Patients included up to 2003 and those included after that year (68) were compared by sex, regarding age at onset of symptoms and diagnosis, severity and previous misdiagnoses. Similar analysis was performed between the index cases (31) and the other patients. Results: Mean delay in diagnosis was 10 years for both sexes. Male had a classic phenotype, and up to 40% of the females reported symptoms. In females, the enzyme activity seemed to determine disease severity. No differences were observed in any parameter when comparing the patients included in the first period to those included afterwards, nor when comparing index cases with the rest of the patients. Conclusions: Registries like FOS have a great value to deepen our understanding of rare diseases. We confirm that women are not just carriers of the disease. There is still a lack of education and awareness in order to include FD in the differential diagnosis of other processes. Complete family studies would allow early diagnosis of this disorder (AU)

Fundamentos y objetivo: La enfermedad de Fabry (EF) es un raro trastorno lisosomal por déficit de la enzima alfa-galactosidasa A, con herencia ligada al cromosoma X, que ocasiona disfunción multiorgánica y muerte temprana. En 2004 se publicaron las características de los primeros 24 pacientes españoles incluidos en el registro Fabry Outcome Survey (FOS), habiendo aumentado significativamente su número desde entonces. Este trabajo analiza si ha habido cambios en el perfil clínico y diagnóstico de los mismos entre los 2 períodos. Pacientes y método: En 2009 existían en el registro FOS datos de 92 pacientes. Se compararon los pacientes de 2003 con los posteriores (68) respecto a la edad de inicio de los síntomas y de diagnóstico, gravedad y diagnósticos previos erróneos, según sexo. Similar análisis se efectuó entre los casos índice (31) y el resto de pacientes. Resultados:En ambos sexos la demora media del diagnóstico fue de 10 años. Los varones presentan un fenotipo clásico, y hasta un 40% de las mujeres referían síntomas. En estas, la actividad enzimática parece condicionar la gravedad de la enfermedad. No hubo diferencias en los parámetros analizados entre los pacientes del primer período y los posteriores, ni al comparar los casos índice con el resto. Conclusiones: Los registros como el FOS poseen valor para ahondar en el conocimiento de las enfermedades minoritarias. Confirmamos que las mujeres no son meras portadoras de la EF. Todavía falta formación y difusión para incluir la EF en el diagnóstico diferencial de otros procesos. Realizar estudios familiares exhaustivos ayudaría a un diagnóstico más precoz (AU)

Zurich Fabry study - prevalence of Fabry disease in young patients with first cryptogenic ischaemic stroke or TIA.

BACKGROUND AND PURPOSE: The etiology of stroke in young patients remains undetermined in up to half of the cases. Data on prevalence of Fabry disease (FD) in young people with cryptogenic ischaemic stroke are limited and controversial. We aimed to evaluate the frequency of unrecognized FD in a cohort of stroke patients at a tertiary stroke center. METHODS: Patients suffering from first cryptogenic ischaemic stroke or transient ischaemic attack (TIA) at the age of 18-55 years were screened for the presence of FD. We measured the serum activity of α-galactosidase (α-GAL) in all patients. In addition, sequencing of α-GAL gene was performed in men with low enzyme activity and in all women. RESULTS: Between January, 2006, and October, 2009, we recruited 150 patients (102 men, 48 women) with a mean age of 43 ± 9 years at symptom onset (135 ischaemic stroke, 15 TIA). The α-GAL activity was low in nine patients (6%; six men and three women). Genetic sequencing in six men with low enzyme activity and all 48 women detected no α-GAL gene mutation. CONCLUSION: Our study suggests that the yield of screening for FD in patients with first cryptogenic ischaemic stroke or TIA is very low. Further large-scale studies are needed to investigate the importance of FD amongst patients with recurrent cryptogenic strokes.

[Fabry-Anderson disease: current state of knowledge]. / La enfermedad de Fabry-Anderson: estado actual del conocimiento.

Fabry-Anderson disease is a lysosomal storage disease caused by deficiency of the enzyme alpha-galactosidase. This enzymatic defect results in the accumulation of glycosphingolipid into different lines cells. Usually the deficiency is complete, resulting in a multisystem disorder, with injury in different organs, predominantly heart, kidney and nervous system. However, in some patients the enzymatic deficit is partial and causes diverse clinical variants of the disease (renal or cardiac variety), this cause a difficult diagnostic and the absence of real epidemiology data. This review is about the epidemiology, the metabolic defect of this disease, it's molecular and genetics bases, the different forms of clinical presentation and the enzyme replacement therapy.

Frequency of Fabry disease in patients with small-fibre neuropathy of unknown aetiology: a pilot study.

BACKGROUND: Early occurrence of small-fibre neuropathy (SFN) is a common feature of Fabry disease (FD) - an X-linked storage disorder caused by reduced activity of the α-galactosidase A (α-GAL). Although SFN may result from different disorders, the cause is often unclear. Therefore, we investigated the frequency of FD in patients with SFN of unknown aetiology. METHODS: Patients with idiopathic SFN, established by sensory quantitative testing and/or skin biopsy, were examined for mutations in the α-GAL gene. Where mutations in the α-GAL gene were identified, levels of globotriaosylceramide (Gb(3)) were measured in urine and blood and the α-GAL activity was evaluated. When new mutations were detected, a diagnostic work-up was performed as well as a Gb(3) accumulation in the skin, lyso-Gb(3) in blood and Gb(3)_24 in urine were proved. RESULTS: Twenty-four of 29 eligible patients were enrolled in the study. Mutations in the α-GAL gene were observed in five patients. A typical mutation for FD (c.424T>C, [C142R]) was detected in one patient. In four patients, a complex intronic haplotype within the α-GAL gene (IVS0-10C>T [rs2071225], IVS4-16A>G [rs2071397], IVS6-22C>T [rs2071228]) was identified. The relevance of this haplotype in the pathogenesis of FD remains unclear until now. However, these patients showed increased concentrations of Gb(3) and/or lyso-Gb(3), while no further manifestations for FD could be proved. CONCLUSIONS: Fabry disease should be considered in patients with SFN of unknown aetiology, and screening for FD should be included in the diagnostic guidelines for SFN. The significance of the intronic haplotype regarding SFN needs further evaluation.

Promoter-specific lentivectors for long-term, cardiac-directed therapy of Fabry disease.

In Fabry disease a deficiency of α-galactosidase A (α-gal A) activity leads to accumulation of globotriaosylceramide (Gb3) in various tissues including the heart. A specific cardiac variant of Fabry disease has also been described. Previously we have demonstrated the feasibility of gene therapy for Fabry disease. Here, to provide efficient transfer and increased specificity of transgene expression, we synthesized lentiviral vectors (LVs) with myocardial-specific promoters including: α-myosin heavy chain (α-MHC), myosin light chain (MLC2v), and cardiac troponin T (cTnT). Initially, neonatal Balb/c mice were injected with such LV constructs engineering expression of luciferase. One month post-injection, we found specific expression of luciferase in hearts of recipient animals when compared with transgene expression driven by the standard EF1-α promoter. To examine the feasibility of long-term therapy specifically targeting the heart, recombinant LV/α-gal A therapeutic vectors with analogous cardiac promoters were generated and injected into numerous neonatal Fabry mice. No immune response against the corrective α-gal A hydrolase was observed in the treated mice. Serum α-gal A activity of 10-week-old Fabry mice was increased in LV/α-gal A-injected animals compared to controls. In 28-week-old Fabry mice we observed significantly decreased Gb3 accumulation. Neonatal injections with LVs harboring cardiac-specific promoters may thus be an effective long-term treatment strategy for heart manifestations and cardiac variant Fabry disease. These results can be also extended to other progressive pathologies of the heart.

Screening patients with hypertrophic cardiomyopathy for Fabry disease using a filter-paper test: the FOCUS study.

BACKGROUND: Patients with Fabry disease (FD) show left ventricular hypertrophy (LVH) mimicking hypertrophic cardiomyopathy (HCM) of sarcomeric origin and might benefit, if detected early, from specific enzyme replacement therapy. The prevalence of FD in patients with LVH of 13 mm or greater, screened using the leucocyte alpha-galactosidase A (α-gal A) activity test, a technique that is difficult to apply routinely, ranged from 0% to 6%. OBJECTIVE: To screen systematically for FD in patients with a diagnosis of HCM (LVH ≥15 mm) in primary cardiology practice, a validated, physician-friendly α-gal A assay was used on dried blood spots using a filter paper test. DESIGN AND PATIENTS: A cohort of 392 adults (278 men) followed for HCM were screened for FD. A standard blood test was used for confirmation in nine men in whom the α-gal A result was 40% or less. RESULTS: Four men (1.5%; 1.8% of men ≥40 years vs 0% <40 years; all with α-gal A <30%), but no women, were diagnosed with FD. Index cases presented with diffuse but asymmetric LVH, with severe obstruction in one case and frequent high-grade atrioventricular conduction block necessitating a pacemaker in three cases. Family screening identified eight additional cases. Genotyping was performed successfully on DNA extracted from the filter papers. CONCLUSION: In male patients diagnosed as having HCM, pure FD cardiac variants are not exceptional and can be specifically identified using a simple filter-paper test. The sensitivity of this test is low in female patients.

Fabry disease.

Fabry disease (FD) is a progressive, X-linked inherited disorder of glycosphingolipid metabolism due to deficient or absent lysosomal α-galactosidase A activity. FD is pan-ethnic and the reported annual incidence of 1 in 100,000 may underestimate the true prevalence of the disease. Classically affected hemizygous males, with no residual α-galactosidase A activity may display all the characteristic neurological (pain), cutaneous (angiokeratoma), renal (proteinuria, kidney failure), cardiovascular (cardiomyopathy, arrhythmia), cochleo-vestibular and cerebrovascular (transient ischemic attacks, strokes) signs of the disease while heterozygous females have symptoms ranging from very mild to severe. Deficient activity of lysosomal α-galactosidase A results in progressive accumulation of globotriaosylceramide within lysosomes, believed to trigger a cascade of cellular events. Demonstration of marked α-galactosidase A deficiency is the definitive method for the diagnosis of hemizygous males. Enzyme analysis may occasionnally help to detect heterozygotes but is often inconclusive due to random X-chromosomal inactivation so that molecular testing (genotyping) of females is mandatory. In childhood, other possible causes of pain such as rheumatoid arthritis and 'growing pains' must be ruled out. In adulthood, multiple sclerosis is sometimes considered. Prenatal diagnosis, available by determination of enzyme activity or DNA testing in chorionic villi or cultured amniotic cells is, for ethical reasons, only considered in male fetuses. Pre-implantation diagnosis is possible. The existence of atypical variants and the availability of a specific therapy singularly complicate genetic counseling. A disease-specific therapeutic option - enzyme replacement therapy using recombinant human α-galactosidase A - has been recently introduced and its long term outcome is currently still being investigated. Conventional management consists of pain relief with analgesic drugs, nephroprotection (angiotensin converting enzyme inhibitors and angiotensin receptors blockers) and antiarrhythmic agents, whereas dialysis or renal transplantation are available for patients experiencing end-stage renal failure. With age, progressive damage to vital organ systems develops and at some point, organs may start to fail in functioning. End-stage renal disease and life-threatening cardiovascular or cerebrovascular complications limit life-expectancy of untreated males and females with reductions of 20 and 10 years, respectively, as compared to the general population. While there is increasing evidence that long-term enzyme therapy can halt disease progression, the importance of adjunctive therapies should be emphasized and the possibility of developing an oral therapy drives research forward into active site specific chaperones.

Bovine norovirus: carbohydrate ligand, environmental contamination, and potential cross-species transmission via oysters.

Noroviruses (NoV) are major agents of acute gastroenteritis in humans and the primary pathogens of shellfish-related outbreaks. Previous studies showed that some human strains bind to oyster tissues through carbohydrate ligands that are similar to their human receptors. Thus, based on presentation of shared norovirus carbohydrate ligands, oysters could selectively concentrate animal strains with increased ability to overcome species barriers. In comparison with human GI and GII strains, bovine GIII NoV strains, although frequently detected in bovine feces and waters of two estuaries of Brittany, were seldom detected in oysters grown in these estuaries. Characterization of the carbohydrate ligand from a new GIII strain indicated recognition of the alpha-galactosidase (α-Gal) epitope not expressed by humans, similar to the GIII.2 Newbury2 strain. This ligand was not detectable on oyster tissues, suggesting that oysters may not be able to accumulate substantial amounts of GIII strains due to the lack of shared carbohydrate ligand and that they should be unable to contribute to select GIII strains with an increased ability to recognize humans.

Functional analysis of the structural domain of ARF proteins in rice (Oryza sativa L.).

Auxin response factors (ARFs) are key regulators of plant growth and development. Through interaction with auxin/indole acetic acid (Aux/IAA) proteins, they influence the expression of auxin response genes. An ARF gene family has been predicted in rice, but the functions of the individual structural domains of the OsARFs remain obscure. Bioinformatics was used to analyse the position of the DNA-binding domain (DBD), middle region (MR), and C-terminal dimerization domain (CTD) of OsARFs, and experimentally confirmed the presence of a classical monopartite nuclear localization signal (NLS) in the DBD. The DBD was shown to contribute to nuclear localization of OsARF proteins in addition to its known DNA-binding function. Interactions between 14 integrated OsARFs and 15 OsIAA proteins were tested using yeast two-hybrid assays. It was found that eight OsARF activators interacted with the 15 OsIAA proteins, while six OsARF repressors did not. The interactions between the MR+CTD or CTD of 10 OsARFs and 15 OsIAA proteins were also tested and the results were consistent with those of each intact OsARF, although some slight differences in interaction intensity were observed by α-galactosidase quantitative assays. The truncated CTD of OsARF11 did not interact with any OsIAA, implying that the CTD is required for ARF-IAA dimerization, and that the MR influences the interaction intensity in yeast. A subset of the interactions in yeast were also observed in tobacco plants using firefly luciferase complementation imaging assays, indicating that these interactions are specific in plants, and might have a special role in the auxin signalling response. This study provides new insight into the structure of OsARF proteins and ARF-Aux/IAA interactions.