In vivo overexpression of frataxin causes toxicity mediated by iron-sulfur cluster deficiency.

Friedreich's ataxia is a rare disorder resulting from deficiency of frataxin, a mitochondrial protein implicated in the synthesis of iron-sulfur clusters. Preclinical studies in mice have shown that gene therapy is a promising approach to treat individuals with Friedreich's ataxia. However, a recent report provided evidence that AAVrh10-mediated overexpression of frataxin could lead to cardiotoxicity associated with mitochondrial dysfunction. While evaluating an AAV9-based frataxin gene therapy using a chicken ß-actin promoter, we showed that toxic overexpression of frataxin could be reached in mouse liver and heart with doses between 1 × 1013 and 1 × 1014 vg/kg. In a mouse model of cardiac disease, these doses only corrected cardiac dysfunction partially and transiently and led to adverse findings associated with iron-sulfur cluster deficiency in liver. We demonstrated that toxicity required frataxin's primary function by using a frataxin construct bearing the N146K mutation, which impairs binding to the iron-sulfur cluster core complex. At the lowest tested dose, we observed moderate liver toxicity that was accompanied by progressive loss of transgene expression and liver regeneration. Together, our data provide insights into the toxicity of frataxin overexpression that should be considered in the development of a gene therapy approach for Friedreich's ataxia.

An Exploration of the Own-Age Effect on Facial Emotion Recognition in Normal Elderly People and Individuals with the Preclinical and Demented Alzheimer's Disease.

BACKGROUND: The issue of whether there exists an own-effect on facial recognition in the elderly remains equivocal. Moreover, currently the literature of this issue in pathological aging is little. OBJECTIVE: Our study was thus to explore the issue in both of healthy older people and patients with ADMethods:In study 1, 27 older and 31 younger healthy adults were recruited; in study 2, 27 healthy older adults and 80 patients (including subjective cognitive decline (SCD), mild cognitive impairment (MCI), and Alzheimer's disease (AD) groups) were recruited. Participants received the Taiwan Facial Emotion Recognition Task (FER Task), and a clinical neuropsychological assessment. RESULTS: No significant differences on the FER test were found among our groups, except for sadness recognition in which our MCI and AD patients' scores were remarkably lower than their healthy counterparts. The own-age effect was not significantly evident in healthy younger and older adults, except for recognizing neutral photos. Our patients with MCI and AD tended to have the effect, particularly for the sad recognition in which the effect was significantly evident in terms of error features (mislabeling it as anger in younger-face and neutral in older-face photos). CONCLUSION: Our results displayed no remarkable own-age effect on facial emotional recognition in the healthy elderly (including SCD). However, it did not appear the case for MCI and AD patients, especially their recognizing those sadness items, suggesting that an inclusion of the FER task particularly involving those items of low-intensity emotion in clinical neuropsychological assessment might be contributory to the early detection of AD-related pathological individuals.

The contribution of vascular risk factors in neurodegenerative disorders: from mild cognitive impairment to Alzheimer's disease.

BACKGROUND: Optimization of vascular risk factor control is emerging as an alternative approach to improve cognitive outcomes in Alzheimer's disease, although its efficacy is still under debate. We aimed to investigate the contribution of vascular risk factors on Alzheimer's biomarkers and conversion rate to dementia in subjects with mild cognitive impairment (MCI) with low cerebral small vessel disease burden. METHODS: Two hundred ninety-five newly diagnosed MCI subjects were enrolled from March 2005 to May 2017 for a cross-sectional assessment of vascular risk factors and Alzheimer's plasma and imaging biomarkers, followed by a cognitive outcome assessment 24 months after enrollment. The association between vascular risk factors and Alzheimer's biomarkers were tested using multivariable linear regression models adjusted with age, gender, education, and APOE ε4 allele. The association between vascular risk factors and conversion to dementia was tested using multivariable logistic regression models adjusted with age, gender, education, and baseline Mini-Mental State Examination (MMSE) score. RESULTS: At baseline, higher low-density lipoprotein (LDL) cholesterol level was associated with more advanced plasma biomarkers, including Aß42/Aß40 ratio (P = 0.012) and tau level (P = 0.001). A history of hypertension was associated with more advanced white matter hyperintensity (P = 0.011), while statin therapy for dyslipidemia was associated with less advanced white matter hyperintensity (P = 0.002). At 24 months, individual vascular risk factor was not significantly associated with cognitive outcome. By contrast, statin therapy for dyslipidemia was associated with reduced conversion to dementia (adjusted OR = 0.191, 95% CI = 0.062~0.586, P = 0.004). CONCLUSIONS: For MCI subjects, dyslipidemia may contribute to AD-related neurodegeneration while hypertension may contribute to vascular pathology. The association between statin therapy for dyslipidemia and reduced conversion to dementia supports further interventional study to evaluate the potential beneficial effect of statin in MCI subjects.

Copper promotes E. coli laccase-mediated TNT biotransformation and alters the toxicity of TNT metabolites toward Tigriopus japonicus.

Although laccase is involved in the biotransformation of 2,4,6-trinitrotoluene (TNT), little is known regarding the effect of E. coli laccase on TNT biotransformation. In this study, E. coli K12 served as the parental strain to construct a laccase deletion strain and two laccase-overexpressing strains. These E. coli strains were used to investigate the effect of laccase together with copper ions on the efficiency of TNT biotransformation, the variety of TNT biotransformation products generated and the toxicity of the TNT metabolites. The results showed that the laccase level was not relevant to TNT biotransformation in the soluble fraction of the culture medium. Conversely, TNT metabolites varied in the insoluble fraction analyzed by thin-layer chromatography (TLC). The insoluble fraction from the laccase-null strain showed fewer and relatively fainter spots than those detected in the wild-type and laccase-overexpressing strains, indicating that laccase expression levels were interrelated determinants of the varieties and amounts of TNT metabolites produced. In addition, the aquatic invertebrate Tigriopus japonicus was used to assess the toxicity of the TNT metabolites. The toxicity of the TNT metabolite mixture increased when the intracellular laccase level in strains increased or when purified E. coli recombinant Laccase (rLaccase) was added to the culture medium. Thus, our results suggest that laccase activity must be considered when performing microbial TNT remediation.

The Social Functioning Scale for Alzheimer's Disease: A Short Informant-based Measure of Functional Status in Patients with Alzheimer's Disease in Taiwan.

OBJECTIVE: Evaluating social-functioning impairments in patients with Alzheimer's disease (AD) objectively is essential for clinical service. However, the existing instruments lack representative content, consensus on purposes of use, and adequate scoring systems and samples. This study was thus to develop a social functioning scale for patients: the Social Functioning Scale for Alzheimer's Disease (SFSAD). METHOD: Questionnaires were analyzed from 142 AD patients, 30 patients with amnestic mild cognitive impairment (aMCI), and 50 normal controls. RESULTS: Based on the literature review and experts' opinions, the final scale includes 20 items in four subscales. The SFSAD showed high internal consistency coefficients (Cronbach's α = .97) and test-retest reliability (r = .99) coefficients. The content validity was desirable, and the criterion-related validity was demonstrated by a significant association with the MMSE, the IADL, and the Barthel ADL. The discriminant validity of the scale was also demonstrated as the level of social-functioning impairment was significantly related to the degree of dementia, and for construct validity, our findings supported the structure of the four-factor hypothesized model. CONCLUSIONS: The SFSAD is thus a practical, psychometrically sound, and easy-to-administer measure to evaluate social functioning of AD and aMCI in brisk clinical settings.

Diminution of context association memory structure in subjects with subjective cognitive decline.

Alzheimer's disease (AD) progresses insidiously from the preclinical stage to dementia. While people with subjective cognitive decline (SCD) have normal cognitive performance, some may be in the preclinical stage of AD. Neurofibrillary tangles appear first in the transentorhinal cortex, followed by the entorhinal cortex in the clinically silent stage of AD. We expected the earliest changes in subjects with SCD to occur in medial temporal subfields other than the hippocampal proper. These selective structural changes would affect specific memory subcomponents. We used the Family Picture subtest of the Wechsler Memory Scale-III, which was modified to separately compute character, activity, and location subscores for episodic memory subcomponents. We recruited 43 subjects with SCD, 44 subjects with amnesic mild cognitive impairment, and 34 normal controls. MRI was used to assess cortical thickness, subcortical gray matter volume, and fractional anisotropy. The results demonstrated that SCD subjects showed significant cortical atrophy in their bilateral parahippocampus and perirhinal and the left entorhinal cortices but not in their hippocampal regions. SCD subjects also exhibited significantly decreased mean fractional anisotropy in their bilateral uncinate fasciculi. The diminution of cortical thickness over the mesial temporal subfields corresponded to brain areas with early tangle deposition, and early degradation of the uncinate fasciculus was in accordance with the retrogenesis hypothesis. The parahippocampus and perirhinal cortex contribute mainly to context association memory while the entorhinal cortex, along with the uncinate fasciculus, contributes to content-related contextual memory. We proposed that context association and related memory structures are vulnerable in the SCD stage.

Arbitrary and semantic associations in subjective memory impairment and amnestic mild cognitive impairment among Taiwanese individuals: A cross-sectional study.

BACKGROUND/PURPOSE: Researchers have recently proposed a preclinical stage of dementia of Alzheimer's type (DAT), referred to as subjective memory impairment (SMI), with the aim of developing methods for the early detection of DAT and subsequent intervention. It has been proposed that the objective memory functions of individuals with SMI are normal; however, arbitrary and semantic associations are both used to describe the processes of memory. No previous studies have investigated these processes among individuals with SMI. METHODS: Cross-sectional analysis was used to compare the memory function of individuals with SMI, amnestic mild cognitive impairment (aMCI), or DAT. One hundred and eighty-three participants were recruited from the Memory Clinic of National Taiwan University Hospital and communities in northern Taiwan, including individuals with no memory complaints (HC, n = 30) and individuals with SMI (n = 61), aMCI-single domain (n = 24), aMCI-multiple domain (n = 33), or DAT (n = 35). The Word Sequence Learning Test (WSLT) was used to assess the formation of arbitrary associations and the Logical Memory subtest of the Wechsler Memory Scale-Third Edition was used to assess the formation of semantic associations. RESULTS: Compared to the HC group, the SMI group performed poorly only on the WSLT, whereas the other groups performed poorly on both of the memory tasks. This study demonstrated that SMI individuals tend to perform poorly in the formation of arbitrary associations. CONCLUSION: Our findings suggest that tasks requiring arbitrary associations may provide greater sensitivity in the detection cognitive changes associated with preclinical DAT.

Lysosomal integral membrane protein-2 as a phospholipid receptor revealed by biophysical and cellular studies.

Lysosomal integral membrane protein-2 (LIMP-2/SCARB2) contributes to endosomal and lysosomal function. LIMP-2 deficiency is associated with neurological abnormalities and kidney failure and, as an acid glucocerebrosidase receptor, impacts Gaucher and Parkinson's diseases. Here we report a crystal structure of a LIMP-2 luminal domain dimer with bound cholesterol and phosphatidylcholine. Binding of these lipids alters LIMP-2 from functioning as a glucocerebrosidase-binding monomer toward a dimeric state that preferentially binds anionic phosphatidylserine over neutral phosphatidylcholine. In cellular uptake experiments, LIMP-2 facilitates transport of phospholipids into murine fibroblasts, with a strong substrate preference for phosphatidylserine. Taken together, these biophysical and cellular studies define the structural basis and functional importance of a form of LIMP-2 for lipid trafficking. We propose a model whereby switching between monomeric and dimeric forms allows LIMP-2 to engage distinct binding partners, a mechanism that may be shared by SR-BI and CD36, scavenger receptor proteins highly homologous to LIMP-2.

Hippocampal atrophy but not white-matter changes predicts the long-term cognitive response to cholinesterase inhibitors in Alzheimer's disease.

INTRODUCTION: This study aimed to investigate the feasibility of predicting the long-term effects of cholinesterase inhibitors (ChEI) with common clinical neuroimaging parameters of Alzheimer's disease, including medial temporal lobe atrophy (MTA) and white matter hyperintensity (WMH). METHOD: A cohort of 353 patients with very mild to moderate Alzheimer's disease received cholinesterase inhibitors and were followed for a median of 46.6 months. Baseline clinical data, including age, educational level, Clinical Dementia Rating (CDR), Taiwanese Mental State Examination (TMSE), and visual scoring for MTA and WMH were tested as possible predictive factors that influence the survival from a TMSE decline of at least 3 points. RESULTS: During the follow-up period, 162(46%) patients had a significant TMSE decline. Patients with age-adjusted prominent MTA had a significantly shorter TMSE-decline free interval than those without (43.4 ± 4.5 months vs. 68.2 ± 9.5 months, log rank test p-value =0.001). However, the severity of WMH does not significantly influence cognitive outcomes. Cox regression analysis identified that younger age at the time of starting ChEI (p < 0.0005) and higher total MTA scores (p = 0.002) predict a more rapid TMSE decline under ChEI therapy. CONCLUSIONS: Younger age at the time of starting ChEI and higher visual scoring of MTA may imply a more advanced Alzheimer's pathology. WMH load is not a prognostic indicator of treatment response to ChEI.

Distinct Patterns and Clinical Implications of Semantic Memory Deterioration Among Patients With MCI.

Limited research has investigated the effects of executive dysfunction on semantic memory deterioration among patients with amnestic mild cognitive impairment (aMCI). This study examined the cognitive performance of 181 participants from various MCI subgroups, a group of mildly impaired individuals with dementia of the Alzheimer type (DAT) and a group of individuals with subjective memory impairment on various semantic memory tasks. The aMCI-single domain (aMCI-sd) group displayed poor performance on a semantic memory task requiring relatively higher degrees of effortful retrieval, and participants in the aMCI-multiple domain (aMCI-md) group, who also suffered with mild executive dysfunction displayed poor performance on all semantic memory tasks, similar to the DAT group. The nonamnestic MCI (non-a-MCI)-single domain group displayed normal performance across all semantic tasks, whereas the non-a-MCI-multiple domain group displayed a pattern similar to that of the aMCI-sd group. aMCI-sd patients who displayed poor performance on the semantic memory task had higher risk of conversion to DAT, whereas poor performance on tasks requiring relatively less effortful retrieval was associated with higher risk of conversion in the aMCI-md group. Thus, executive function may relate to deterioration of semantic memory retrieval processes. Such patterns of semantic memory impairment could be valuable for characterization of cognitive differences among MCI patients.

Temperature-dependent variations in sulfate-reducing communities associated with a terrestrial hydrocarbon seep.

Terrestrial hydrocarbon seeps are an important source of naturally emitted methane over geological time. The exact community compositions responsible for carbon cycling beneath these surface features remain obscure. As sulfate reduction represents an essential process for anoxic organic mineralization, this study collected muddy fluids from a high-temperature hydrocarbon seep in Taiwan and analyzed community structures of sulfate-supplemented sediment slurries incubated anoxically at elevated temperatures. The results obtained demonstrated that sulfate consumption occurred between 40°C and 80°C. Dominant potential sulfate reducers included Desulfovibrio spp., Desulfonatronum spp., Desulforhabdus spp., and Desulfotomaculum spp. at 40°C, Thermodesulfovibrio spp. at 50°C, Thermodesulfovibrio spp. and Thermacetogenium spp. at 60°C, Thermacetogenium spp. and Archaeoglobus spp. at 70°C, and Archaeoglobus spp. at 80°C. None of these potential sulfate reducers exceeded 7% of the community in the untreated sample. Since no exogenous electron donor was provided during incubation, these sulfate reducers appeared to rely on the degradation of organic matter inherited from porewater and sediments. Aqueous chemistry indicated that fluids discharged in the region represented a mixture of saline formation water and low-salinity surface water; therefore, these lines of evidence suggest that deeply-sourced, thermophilic and surface-input, mesophilic sulfate-reducing populations entrapped along the subsurface fluid transport could respond rapidly once the ambient temperature is adjusted to a range close to their individual optima.

Plasma Aß but not tau is related to brain PiB retention in early Alzheimer's disease.

Recent advances in biomarkers provide the possibility of early or preclinical diagnosis of Alzheimer's pathology. Currently, decreased levels of Aß-42 and increased levels of tau proteins in cerebral spinal fluid are considered reliable biomarkers of Alzheimer's disease (AD); however, little evidence exists for the use of amyloid and tau protein levels in the plasma as useful biomarkers. We investigated the potential use of plasma biomarkers to diagnose AD and explored their relationships with brain Aß deposition in amyloid imaging. We used an immunomagnetic reduction assay to measure the plasma levels of Aß40, Aß42, and tau proteins in 20 older control participants and 25 participants who had either mild cognitive impairment due to AD or early AD dementia. All participants received (11)C-labeled Pittsburgh compound B PET scans. The sensitivity of the plasma tau level at the cutoff value of 28.27 pg/mL was 92%, and the specificity was 100%; the sensitivity of the Aß42/40 ratio at the cutoff value of 0.3693 was 84%, and the specificity was 100%. Regression analyses of the effects of plasma protein levels on brain amyloid retention, as determined by standard uptake value ratios in either side of the frontal, parietal, and temporal lobes and the precuneus, are predicted only by ratios of plasma Aß42/40 (R(2) 0.326-0.449, all p < 0.001) but not by plasma tau levels. Plasma Aß in terms of Aß42/40 might provide an indirect estimation of Aß deposition in the brain.

Spatial variations of community structures and methane cycling across a transect of Lei-Gong-Hou mud volcanoes in eastern Taiwan.

This study analyzed cored sediments retrieved from sites distributed across a transect of the Lei-Gong-Hou mud volcanoes in eastern Taiwan to uncover the spatial distributions of biogeochemical processes and community assemblages involved in methane cycling. The profiles of methane concentration and carbon isotopic composition revealed various orders of the predominance of specific methane-related metabolisms along depth. At a site proximal to the bubbling pool, the methanogenic zone was sandwiched by the anaerobic methanotrophic zones. For two sites distributed toward the topographic depression, the methanogenic zone overlaid the anaerobic methanotrophic zone. The predominance of anaerobic methanotrophy at specific depth intervals is supported by the enhanced copy numbers of the ANME-2a 16S rRNA gene and coincides with high dissolved Fe/Mn concentrations and copy numbers of the Desulfuromonas/Pelobacter 16S rRNA gene. Assemblages of 16S rRNA and mcrA genes revealed that methanogenesis was mediated by Methanococcoides and Methanosarcina. pmoA genes and a few 16S rRNA genes related to aerobic methanotrophs were detected in limited numbers of subsurface samples. While dissolved Fe/Mn signifies the presence of anaerobic metabolisms near the surface, the correlations between geochemical characteristics and gene abundances, and the absence of aerobic methanotrophs in top sediments suggest that anaerobic methanotrophy is potentially dependent on iron/manganese reduction and dominates over aerobic methanotrophy for the removal of methane produced in situ or from a deep source. Near-surface methanogenesis contributes to the methane emissions from mud platform. The alternating arrangements of methanogenic and methanotrophic zones at different sites suggest that the interactions between mud deposition, evaporation, oxidation and fluid transport modulate the assemblages of microbial communities and methane cycling in different compartments of terrestrial mud volcanoes.

Theory of mind in patients with temporal lobe epilepsy.

Theory of mind (ToM) is a crucial aspect of social cognition and is mediated by a complex neural network. Studies on temporal lobe epilepsy (TLE) suggest that its neuropathological involvement includes several brain regions. Some regions seem to overlap the neural network responsible for ToM, and this overlap provides an opportunity to explore ToM in TLE patients. Another concern is psychosocial problems in TLE, and the study of ToM in TLE could serve as a basis for further understanding the nature of such psychosocial disturbances. Studies on whether TLE patients evidence ToM deficit, however, are scant and controversial. Consequently, we examine whether ToM deficit is evident in TLE. Thirty-one TLE patients and 24 matched controls were recruited and completed four tasks measuring different levels of ToM: false belief, faux pas recognition, processing of implied meanings, and cartoon ToM. The patients were impaired in both basic and advanced ToM. Right TLE had a more wide-ranging picture of deficit than left TLE. ToM appears to be vulnerable to TLE, especially on the right side. Since ToM might contribute to patients' psychosocial adjustment, we thus suggest that a ToM measure be included in regular neuropsychological assessments of such patients.

Cross-cultural effect on suboptimal effort detection: an example of the Digit Span subtest of the WAIS-III in Taiwan.

Suppressed Digit Span performance has been proposed as an embedded indicator for suboptimal effort detection in neuropsychological evaluations in Western societies, particularly in the USA. However, its effectiveness in Chinese countries remains unexplored. The purposes of this study were first to explore normative Digit Span performance patterns between the Taiwan and American standardization samples, then to examine performances of patients with traumatic brain injury and with psychiatric diseases on the embedded measures (the Digit Span Scaled Score, Vocabulary minus Digit Span difference score, Reliable Digit Span, and the longest string of digits forward and backward) through retrospective data analysis. The normative Digit Span performance differs between the two cultural populations. Although litigating and nonlitigating participants perform differently on these measures, further prospective studies are needed to explore this issue with comprehensive external corroborating validity data.

Neuropsychological profile in patients with early stage of Parkinson's disease in Taiwan.

Given the importance of early detection and intervention for disease management, determining the vulnerable neuropsychological function in patients with early-stage Parkinson's disease (PD) is a priority. Here, we describe the neuropsychological pattern in early-stage PD patients with mild cognitive impairment (PD-MCI) and dementia (PDD) in Taiwanese population. The neuropsychological performance of 94 patients with PD was compared with that of 84 healthy controls (HCs) and available normative data, using a comprehensive neuropsychological assessment including tests of executive, memory, psychomotor speed, attention, visuospatial, and language functions. Our results showed that PD patients performed significantly worse on executive function (i.e., category of card sorting) and psychomotor speed (i.e., processing speed index). Up to 46.8% were classified as PD-MCI and the majority of those having single-domain impairment (68.2%); 9.6% met the consensus diagnostic criteria for PDD. Accordingly, we suggest that early-stage PD patients have cognitive dysfunction predominately in the anterior brain. Further follow-up study to determine how many percent of PD-MCI develop PDD is important. The effect of neurocognitive rehabilitation on executive function is also valuable in the subsequence study.

Metabolic stratification driven by surface and subsurface interactions in a terrestrial mud volcano.

Terrestrial mud volcanism represents the prominent surface geological feature, where fluids and hydrocarbons are discharged along deeply rooted structures in tectonically active regimes. Terrestrial mud volcanoes (MVs) directly emit the major gas phase, methane, into the atmosphere, making them important sources of greenhouse gases over geological time. Quantification of methane emission would require detailed insights into the capacity and efficiency of microbial metabolisms either consuming or producing methane in the subsurface, and establishment of the linkage between these methane-related metabolisms and other microbial or abiotic processes. Here we conducted geochemical, microbiological and genetic analyses of sediments, gases, and pore and surface fluids to characterize fluid processes, community assemblages, functions and activities in a methane-emitting MV of southwestern Taiwan. Multiple lines of evidence suggest that aerobic/anaerobic methane oxidation, sulfate reduction and methanogenesis are active and compartmentalized into discrete, stratified niches, resembling those in marine settings. Surface evaporation and oxidation of sulfide minerals are required to account for the enhanced levels of sulfate that fuels subsurface sulfate reduction and anaerobic methanotrophy. Methane flux generated by in situ methanogenesis appears to alter the isotopic compositions and abundances of thermogenic methane migrating from deep sources, and to exceed the capacity of microbial consumption. This metabolic stratification is sustained by chemical disequilibria induced by the mixing between upward, anoxic, methane-rich fluids and downward, oxic, sulfate-rich fluids.

Rap1gap2 regulates axon outgrowth in olfactory sensory neurons.

Olfactory sensory neurons (OSNs) extend their axons from the nasal epithelium to their odorant receptor-dependent locations in the olfactory bulb. Previous studies have identified several membrane proteins along the projection pathway, and on OSN axons themselves, which regulate this process; however, little is known about the signaling mechanisms through which these factors act. We have identified and characterized Rap1gap2, a novel small GTPase regulator, in OSNs during early postnatal mouse development. Rap1gap2 overexpression limits neurite outgrowth and branching in Neuro-2a cells, and counteracts Rap1-induced augmentation of neurite outgrowth. Rap1gap2 expression is developmentally regulated within OSNs, with high expression in early postnatal stages that ultimately drops to undetectable levels by adulthood. This temporal pattern coincides with an early postnatal plastic period of OSN innervation refinement at the OB glomerular layer. Rap1gap2 stunts OSN axon outgrowth when overexpressed in vitro, while knock-down of Rap1gap2 transcript results in a significant increase in axon length. These results indicate an important role of Rap1gap2 in OSN axon growth dynamics during early postnatal development.

Microbial methane cycling in a terrestrial mud volcano in eastern Taiwan.

Microbial communities responsible for methane cycling in mud volcanoes onshore are poorly characterized. This study analysed bubbling fluids and cored sediments retrieved from a mud volcano in eastern Taiwan. The pore water profiles revealed that methane concentrations generally increased with depth and changed dramatically at different depth intervals at different sites. The methane concentrations were inversely correlated with Fe(2+)/Mn(2+) concentrations and δ(13)C values of methane, marking iron/manganese-methane transition zones in the sediment cores. Archaeal communities were dominated by ANME-2a members and methylotrophic methanogens, whereas bacterial communities consisted primarily of Proteobacteria, Firmicutes and Bacteroidetes. The 16S rRNA gene copy numbers of ANME-2a and Desulfuromonas/Pelobacter populations varied by two to three orders of magnitude along the profile and exhibited a pattern comparable with those of Fe(2+) and δ(13)C values of methane. These lines of evidence suggest a coupling between anaerobic methanotrophy and metal reduction in the metal-methane transition zones under sulfate-deficient conditions, a metabolic scheme contrasting with that observed in marine cold seeps. Anaerobic methanotrophs proliferate by removing methane produced from in situ methanogenesis and originating from the deep source. Methane finally emitted into the atmosphere is quantitatively and isotopically altered by various microbial processes compartmentalized at different depth intervals.