The history of ice melting and the viscoelastic properties of the mantle heavily influence Antarctic crustal deformation caused by Glacial Isostatic Adjustment (GIA). The interaction between ice history and mantle viscosity further complicates the complex Antarctic GIA. Nonetheless, geodetic observations, such as GNSS, are crucial for constraints on the GIA model parameters. For over two decades, the Japanese Antarctic Research Expedition (JARE) has been using GNSS and absolute gravity measurements to obtain data along the coast of Lützow-Holm Bay, primarily at Syowa Station. This study examines the geodetic signals associated with GIA from observations along the Lützow-Holm Bay coastline in East Antarctica, and we also conduct GIA simulations based on the recent report of rapid ice thinning in the target region during the mid-Holocene. Based on geomorphological surveys and surface exposure ages, Kawamata et al. (2020: QSR) showed that the region experienced rapid ice thinning of over 400 m from about 9 to 6 ka. Representative deglaciation models, such as ICE-6G, do not account for this rapid thinning process. Therefore, we investigate the variability of the geodetic signals using the ice history, including this rapid thinning. Our predictions demonstrate that incorporating the modified ice history results in consistent outcomes with the observations. This finding supports the notion that rapid ice melting occurred in the Holocene and suggests that geodetic observations can help constrain this region's ice sheet melting process. Additionally, we will present a possibility of the readvance following the rapid retreat based on the precise GIA modelling.

Understanding East Antarctic Ice Sheet dynamics during the mid-Holocene remains challenging due to complex climate interactions. Using Global Navigation Satellite System observations and glacial isostatic adjustment modeling, we investigate the ice-sheet history in the Lützow–Holmbukta region. Here we show that scenarios incorporating modest (65–100 m) ice-sheet re-thickening following previously documented rapid thinning of ~ 400 m between 9 and 6 ka provide improved agreement with geodetic observations compared with global deglaciation models. Our analysis constrains the rheological structure beneath East Antarctica, suggesting a lithospheric thickness of 50–70 km, upper mantle viscosities of 5–7 × 1020 Pa s, and lower mantle viscosities of 6–80 × 1021 Pa s, which show excellent agreement with independent constraints from effective elastic thickness studies and are broadly compatible with seismological estimates. These findings highlight the need to incorporate regional ice-sheet histories when investigating past ice-sheet dynamics, which is essential for understanding present-day behavior and predicting future responses to climate change.

The Gravity Recovery and Climate Experiment (GRACE) has revealed spatiotemporal mass changes in the Antarctic Ice Sheet. However, GRACE data must be corrected for the gravity changes due to glacial isostatic adjustment (GIA). Here we investigate the sensitivity of GIA-induced gravity changes in Antarctica to the lithospheric thickness and upper mantle viscosity using a one-dimensional (1-D) model that assumes a radially varying Earth structure. The sensitivity is assessed using several Antarctic ice-history models that have been widely used to correct GRACE data. The results indicate a trade-off between lithospheric thickness and upper mantle viscosity in evaluating the Antarctic GIA correction. This trade-off exists for all ice-history models; however, the reason for the trade-off differs among models. Furthermore, since there is a sharp contrast in the Earth structure between West and East Antarctica, the adopted ice histories are separated into West and East Antarctic components to examine their contributions to the Antarctic GIA correction. We consider 1-D Earth structures that are averaged from the seismically derived three-dimensional Earth structure for West and East Antarctica. These results indicate that the contributions of the East and West Antarctic loads do not significantly affect the GIA corrections for the West and East Antarctic regions, respectively, and that the trade-off between lithospheric thickness and upper mantle viscosity results in minimal divergence in the assessment of the Antarctic GIA correction between the averaged Earth models of West and East Antarctica. Therefore, the contrast in Earth structure beneath Antarctica may have a limited effect on the ice-mass change estimates for the entire Antarctic Ice Sheet.

The liquid water around the Antarctic Ice Sheet plays a key role in modulating both the vulnerability of ice shelves to hydrofracturing and ice discharge from outlet glaciers. Therefore, it needs to be adequately constrained for precise future projections of ice-mass loss and global sea-level rise. Although glacial lake outburst floods (GLOFs) pose one of the greatest risks in glacierized mountainous regions, any long-term monitoring of Antarctic ice-marginal lakes and their associated potential for GLOFs has been neglected until recently owing to the limited number of such events reported in Antarctica. Here we present direct evidence of repeated GLOFs from Lake Kaminotani-Ike, an ice-sheet-dammed lake in East Antarctica, via an analysis of historical aerial photographs and recent satellite data. Two GLOFs occurred in 1969–1971 and 2017, with discharge volumes of (8.6 ± 1.5) × 107 and (7.1 ± 0.4) × 107 m3, respectively, making them two of the largest GLOFs in Antarctica. A southerly oceanward pathway beneath the ice sheet is the most likely drainage route of these GLOF events based on the available surface- and bed-elevation datasets. Furthermore, the 2017 event occurred during the austral winter, thereby implying the possibility of year-round active subglacial networks in Antarctica. Our results highlight that studies on Antarctic ice-marginal lakes provide an opportunity to better understand Antarctic hydrological processes and emphasize the need for both detailed monitoring of ice-marginal lakes and detailed surveying of the subglacial environments of the Antarctic Ice Sheet.

We have shown that the flow velocity of Shirase Glacier can be estimated by applying the offset tracking method to the amplitude images derived from the phased array type L-band synthetic aperture radar type-2 (PALSAR-2) onboard the Advanced Land Observing Satellite-2. Although the offset tracking is widely used, the method is sometimes not applicable effectively and the reason is not always clear. Here, we consider a possibility of ionospheric contamination and show the validation results of the estimated flow velocity applied the offset tracking method to the PALSAR-2 data, based on in-situ measurement of the flow velocity from the GNSS receiver on the autonomous phase-sensitive radio echo sounder simultaneously with the PALSAR-2 observation. As a result, the ionospheric contamination can yield a spurious error of ±0.2 km a −1 . After statistically removing the erroneous pairs, the RMSE was 0.049 km a −1 derived from the flow velocity error between the in-situ measurement results and estimated from satellite, and the estimated flow velocity obtained using PALSAR-2 data is proved to be in good agreement with the ground truth. Obtained spatial and temporal variations reveal signature of glacier dynamics, which prove the efficacy of the offset tracking method. The obtained ice-flow velocity increases rapidly from the upstream region to the coast, but its velocity is roughly constant over a region, 10-km long about the grounding line (GL), then gradually tends to increase again downstream from the GL. This trend has continued largely unchanged over24 years since 1996.

The Antarctic ice mass loss is accelerating due to recent global warming. Changes in Antarctic ice mass have been observed as the gravity change by GRACE (Gravity Recovery and Climate Experiment) satellites. However, the gravity signal includes both the component of the ice mass change and the component of the solid Earth response to surface mass change (Glacial Isostatic Adjustment, GIA). Evaluating the GIA-induced gravity change requires viscoelastic Earth structure and ice history from the last deglaciation.Antarctica is characterized by lateral heterogeneity of seismic velocity structure. West Antarctica shows relatively low seismic velocities, suggesting low viscosity regions in the upper mantle. On the other hand, East Antarctica shows relatively high seismic velocities, suggesting thick lithosphere. Here we examine the sensitivities of GIA-induced gravity change in Antarctica to upper mantle viscosity and lithosphere thickness using spherically symmetric Earth models.Results indicate that the gravity field change depends on both the upper mantle viscosity profile and the lithosphere thickness. In particular, the long-wavelength gravity field changes become dominant in the adoption of viscoelastic models with a low viscosity layer beneath the elastic lithosphere. The same trend is also shown in the adoption of viscoelastic models with a thick lithosphere, and there is a trade-off between the structure of the low viscosity layer and the thickness of the lithosphere. This trade-off may reduce the effect of the lateral variations in Earth structure beneath Antarctica on the estimate of Antarctic ice sheet mass change.

Background: Dentatorubral-pallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disorder caused by the unstable expansion of CAG repeats encoding polyglutamine stretches in DRPLA gene (ATN1). DRPLAp, the gene product of ATN1, is located in the nucleus and has been shown to function as a transcriptional coregulator. Its target genes, however, remain largely unknow. Aim: To elucidate the physiological functions of DRPLAp based on determination of the target genes regulated by wild-type DRPLAp. Methods: Using the cultured cells expressing wild-type full-length DRPLA cDNA (Q19) encoding DRPLAp under the control of the doxycycline (Dox)-On system, we searched for genes whose expression levels were regulated by wild-type DRPLAp (Q19). Results: On the basis of detailed RNA-seq analyses, we identified seven up-regulated genes and five down-regulated genes in Q19 cells. In gene ontology analysis, the up-regulated differentially expressed genes formed clusters featuring skeletal system morphogenesis, transcriptional regulation, and RNA metabolism, which is consistent with the recent report that the mutations in ATN1 lead to recognizable facial form and variable congenital anomalies. Conclusion: These findings support that DRPLAp may play a role as a transcriptional coregulator involved in the regulation of development.

In this study, Japanese and Han Chinese individuals (n = 32, each) were genotyped for 261 autosomal STRs, and allele frequencies were calculated for each locus in each population. The average number of alleles for all loci in Japanese and Han Chinese populations was 6.65 and 6.56, respectively. The tests for deviations from HWE performed using an exact test showed that the number of STRs (P > 0.05) in Japanese and Han Chinese populations was 236 and 241, respectively. Calculation of forensic parameters showed heterozygosity, and the exclusion means in the Japanese population were 0.7185 and 4813 and those in the Han Chinese population were 0.7308 and 0.5008. In addition, population genetic analyses, such as principal component analysis and factorial correspondence analysis, were performed and a differential formula with likelihood ratios was applied for various number of STR loci based on the effectiveness of differentiation between the two populations. Accordingly, this study suggests that statistical differentiation between genetically close populations, such as the Japanese and Han Chinese populations, is possible if approximately 40-50 effective STR loci are analyzed.

The redistribution of the near-surface solid Earth due to glacial isostatic adjustment (GIA), which is the ongoing response of the solid Earth due to changes in the ice-ocean load following the Last Glacial Maximum, has a direct impact on the inferred Antarctic Ice Sheet (AIS) mass balance from gravimetric data acquired during the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) missions. However, sparse in-situ observation networks across Antarctica have led to the inability to effectively constrain the GIA effect. Here, we analyze the mass change patterns across Antarctica via independent component analysis (ICA), a statistics-based blind source separation method to extract signals from complex datasets, in an attempt to reduce uncertainties in the glacial isostatic adjustment (GIA) effects and improve understanding of AIS mass balance. The results reveal that GIA signal could be directly separated from GRACE/GRACE-FO observations without introducing any external model. Although the GIA signal cannot be completely isolated, the correlation coefficients between ICA-separated GIA, and the ICE-5G and ICE-6G models are 0.692 and 0.691, respectively. The study demonstrates the possibility of extracting GIA effects directly from GRACE/GRACE-FO observations.

Here we qualitatively analyse the mass change patterns across Antarctica via independent component analysis (ICA), a statistics-based blind source separation method to extract signals from complex data sets, in an attempt to reduce uncertainties in the glacial isostatic adjustment (GIA) effects and improve understanding of Antarctic Ice Sheet (AIS) mass-balance. We extract the six leading independent components from gravimetric data acquired during the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) missions. The results reveal that the observed continental-scale mass changes can be effectively separated into several spatial patterns that may be dominated by different physical processes. Although the hidden independent physical processes cannot be completely isolated, some significant signals, such as glacier melt, snow accumulation, periodic climatic signals, and GIA effects, can be determined without introducing any external information. We also observe that the time period of the analysed data set has a direct impact on the ICA results, as the impacts of extreme events, such as the anomalously large snowfall events in the late 2000s, may cause dramatic spatial and temporal changes in the ICA results. ICA provides a unique and informative approach to obtain a better understanding of both AIS-scale mass changes and specific regional-scale spatiotemporal signal variations.

日本南極地域観測隊の測地定常観測による有人航空機で撮影されたアーカイブ空中写真に対し,Structure from Motion多視点ステレオ写真測量(Structure from Motion with Multi-View Stereo Photogrammetry: SfM–MVS)処理を行うことで,精密な数値表層モデル(Digital Surface Model: DSM)の作成を試みた.その結果,東南極宗谷海岸のスカルブスネスにおいて,氷食微地形や基盤岩の節理といった微起伏をも判読可能なDSMを作成できた.作成したDSMには,SfM-MVS処理特有の歪みが確認されたが,歪みの3次元曲面トレンドを推定し補正することによって,歪みを軽減することができた.また,今回作成したDSM(画像取得年1993年)と国土地理院作成のDSM(画像取得年2009年)の比較から,露岩上の氷河湖において各DSMの平均二乗誤差を大きく上回る20 m以上の水位変動が起きたことが明らかとなった.本手法で作成したDSMは,地形研究はもちろん氷床質量収支や氷床縁監視などの地球環境変動研究の基礎データとして応用が期待できる.

We conducted gravity observations in Antarctica at Jang Bogo Station (JBS) during the 2019-2020 Austral summer season using an FG5-210 absolute gravimeter (AG) and a LaCoste & Romberg (LCR) Model D-58 relative gravimeter. Absolute gravity measurements were successfully made at reference gravity point JBSAG1 and newly established gravity point JBSAG2, yielding about 19,000 and 14,400 drops of data, respectively, with measurement precisions better than 0.4 mu Gal (1 mu Gal = 10(-8) m s(-2)). In addition, relative gravity measurements were conducted at 10 other newly established gravity points, with accuracies better than 10 mu Gal, to supplement the absolute gravity data. Superconducting gravimeter (SG) observation with an iGrav-021 instrument has been underway at JBS since 2016. Since an SG is a relative gravimeter, the calibration of the scale factor is essential for long-term gravity monitoring. In addition, the D-58 instrument was required for scale factor calibration. To calibrate the scale factors of these gravimeters, we first estimated a value for the iGrav-021 using parallel observations with the FG5-210 instrument. The D-58 scale factor was then estimated indirectly from parallel observations with the iGrav-021. These calibrations should ensure accurate gravity monitoring in future work.

Geological reconstruction of the retreat history of the East Antarctic Ice Sheet (EAIS) since the Last Glacial Maximum (LGM) is essential for understanding the response of the ice sheet to global climatic change and the mechanisms of retreat, including a possible abrupt melting event. Such information is key for constraining climatic and ice-sheet models that are used to predict future Antarctic Ice Sheet AIS melting. However, data required to make a detailed reconstruction of the history of the EAIS involving changes in its thickness and lateral extent since the LGM remain sparse. Here, we present a new detailed ice-sheet history for the southern Soya Coast, Lfitzow-Holm Bay, East Antarctica, based on geomorphological observations and surface exposure ages. Our results demonstrate that the ice sheet completely covered the highest peak of Skarvsnes (400 m a.s.l.) prior to similar to 9 ka and retreated eastward by at least 10 km during the Early to Mid-Holocene (ca. 9 to 5 ka). The timing of the abrupt ice-sheet thinning and retreat is consistent with the intrusion of modified Circumpolar Deep Water (mCDW) into deep submarine valleys in Lfitzow-Holm Bay, as inferred from fossil foraminifera records of marine sediment cores. Thus, we propose that the mechanism of the abrupt thinning and retreat of the EAIS along the southern Soya Coast was marine ice-sheet instability caused by mCDW intrusion into deep submarine valleys. Such abrupt ice-sheet thinning and retreat with similar magnitude and timing have also been reported from Enderby Land, East Antarctica. Our findings suggest that abrupt thinning and retreat as a consequence of marine ice-sheet instability and intrusion of mCDW during the Early to Mid-Holocene may have led to rapid icesurface lowering of hundreds of meters in East Antarctica. (C) 2020 The Author(s). Published by Elsevier Ltd.

The purpose of geomorphological studies in East Antarctica is to understand past fluctuations of the Antarctic Ice Sheet, which is essential to constrain ice sheet models and predict future behavior of the East Antarctic Ice Sheet. Here we show a deglacial history of Skarvsnes, at the southern part of the Soya Coast, East Antarctica based on a geomorphological field survey and newly obtained surface exposure ages. Bedrock higher than ca. 250 m a.s.l. at the northwest part of Skarvsnes (Skjegget) is weathered extensively, whereas bedrock below ca. 250 m a.s.l. is relatively unweathered. The degree of weathering of bedrock above 250 m a.s.l. is similar to that at the northern part of the Soya Coast, which is thought to have been ice-free throughout the last glacial period. Therefore, a clear difference in the degree of weathering depending on altitude probably indicates the lower limit of the ice sheet elevation during the last glacial period at Skarvsnes. Judging from the multiple directions of glacial striae, the ice sheet covering the area retreated while changing flow direction under the influence of the bedrock topography after the last glacial period. Since ca. 9 ka, the ice sheet is thought to have thinned and eventually divided into two major ice streams (northward and southward) that were obstructed by a 362 m a.s.l. mountain (Shirasuso-Yama), at the southeastern part of Skarvsnes. However, the timing of the initiation of the ice sheet retreat and its duration remain unclear. Therefore, additional surface exposure ages from various areas and heights at Skarvsnes are required for a detailed reconstruction of the ice retreat history and to understand its mechanism.

Our objective was to investigate the frequency of KIF5A variants in amyotrophic lateral sclerosis (ALS) and the clinical characteristics of familial ALS (FALS) associated with variants in KIF5A. Whole-exome sequence analysis was performed for a Japanese series of 43 families with FALS and 444 patients with sporadic ALS (SALS), in whom causative variants had not been identified. We compared the frequencies of rare variants (MAF < 0.01) in KIF5A, including missense and loss of function (LoF) variants, between ALS and control subjects (n = 1163). Clinical characteristics of patients with FALS carrying pathogenic variants in KIF5A were also described. LoF variants were identified only in the probands of two families with FALS, both of which were 3′ splice-site variants leading to exon skipping and an altered C-terminal domain, located in the mutational hotspot causing FALS, and were considered to be pathogenic for FALS. Rare missense variants in KIF5A were identified in five patients with SALS (1.13%) and 11 control subjects (0.95%, carrier frequency), which were not significantly different. Consequently, the pathogenic LoF variants in KIF5A accounted for 2.1% of all FALS families in this study. These patients suffered from ALS characteristically associated with the predominant involvement of upper motor neuron. In conclusion, we identified two pathogenic splice-site variants in KIF5A in the probands in two Japanese families with FALS, which altered the C-terminal region of KIF5A. Our findings broaden the phenotype spectrum of ALS associated with variants in KIF5A in the Japanese series.

Since the establishment in 2013, GGOS Japan, formerly known as GGOS Working Group of Japan, has actively contributed to domestic and international space-geodetic activities. Until it was established, six Japanese agencies with their own backgrounds and missions had individually conducted geodetic observations of GNSS, VLBI, SLR, DORIS and gravimetry in Japan and Antarctica. GGOS Japan was established to strengthen the collaboration between the agencies and to get connected to international organizations such as IAG and GGOS. Its core members consist of a chair, a secretary, a lead of the outreach working group, a lead of the DOI working group and representatives of five core techniques. It is supported by tens of people in Japan and also by its parent entity, IAG subcommittee in Japan. This presentation will cover our achievement such as assembling our site list, hosting various domestic/international meetings, planning a special issue in a domestic journal, producing its leaflet and website and so on. Since 2017 it has been approved as an GGOS Affiliate and it is remarkable that Basara Miyahara was elected as GGOS President in 2019.

Intracranial artery stenosis (ICAS) is the most common cause of ischemic stroke worldwide. RNF213 single nucleotide variant c.14429G > A (p.Arg4810Lys, rs112735431) was recently reported to be associated with ICAS in East Asians. However, the disease susceptibility of other RNF213 variants has not been clarified. This study comprehensively investigated ICAS-associated RNF213 variants in a pool of 168 Japanese ICAS patients and 1,194 control subjects. We found 138 nonsynonymous germline variants by target resequencing of all coding exons in RNF213. Association study between ICAS patients and control subjects revealed that only p.Arg4810Lys had significant association with ICAS (P = 1.5 × 10–28, odds ratio = 29.3, 95% confidence interval 15.31–56.2 [dominant model]). Fourteen of 138 variants were rare variants detected in ICAS patients not harboring p.Arg4810Lys variant. Two of these rare variants (p.Cys118Arg and p.Leu2356Phe) consistent with variants previously reported in moyamoya disease patients characterized by stenosis of intracranial artery and association with RNF213, and three rare variants (p.Ser193Gly, p.Val1817Leu, and p.Asp3329Tyr) were found neither in control subjects and Single Nucleotide Polymorphism Database. The present findings may improve our understanding of the genetic background of intracranial artery stenosis.

Loss-of-function (LoF) variants in NEK1 have recently been reported to be associated with amyotrophic lateral sclerosis (ALS). In this study, we investigated the association of NEK1 LoF variants with an increased risk of sporadic ALS (SALS) and the clinical characteristics of patients with SALS carrying LoF variants in a Japanese case series. Whole-exome sequencing analysis was performed for a series of 446 SALS patients in whom pathogenic variants in familial ALS-causative genes have not been identified and 1163 healthy control subjects in our Japanese series. We evaluated LoF variants, defined as nonsense, splice-site disrupting single-nucleotide variants (SNVs), or short insertion/deletion (indel) variants predicted to cause frameshifts in NEK1. We identified seven NEK1 LoF variants in patients with SALS (1.57%), whereas only one was identified in control subjects (0.086%) (P = 0.00073, Fisher’s exact test). This finding is consistent with those in recent reports from other regions in the world. In conclusion, we demonstrated that NEK1 LoF variants are also associated with an increased risk of SALS in the Japanese population.

Antarctica is one of the most rapidly mass changing areas with poor ground observation data on Earth. Considering the dominant uncertainty in Glacial Isostatic Adjustment (GIA) effects for the Antarctic Ice Sheet (AIS) mass balance, we analyze mass change patterns of Antarctica qualitatively using a statistics-based blind source separation method named Independent Component Analysis (ICA). We extract the 6 leading independent components using gravimetric data derived from the Gravity Recovery and Climate Experiment (GRACE) mission and GRACE Follow-On (GRACE-FO) mission. The results show that the whole continental mass changes can be effectively separated into several spatial patterns that could be dominated by different physical processes. Although the hidden independent physical processes cannot be completely separated, some significant signals such as glacial melting components, snow accumulation components, periodic climatic components, and GIA effects could be determined without introducing any external information. We also found that the time period of the employed data sets has a direct impact on ICA results. This suggested that some impacts of extreme events, such as rapid increases of snowfall in the late 2000s might cause dramatic changes spatially and temporally. In general, ICA provides a special view for a better understanding of AIS mass changes and specific regional researches.

Noncoding repeat expansions cause various neuromuscular diseases, including myotonic dystrophies, fragile X tremor/ataxia syndrome, some spinocerebellar ataxias, amyotrophic lateral sclerosis and benign adult familial myoclonic epilepsies. Inspired by the striking similarities in the clinical and neuroimaging findings between neuronal intranuclear inclusion disease (NIID) and fragile X tremor/ataxia syndrome caused by noncoding CGG repeat expansions in FMR1 , we directly searched for repeat expansion mutations and identified noncoding CGG repeat expansions in NBPF19 ( NOTCH2NLC ) as the causative mutations for NIID. Further prompted by the similarities in the clinical and neuroimaging findings with NIID, we identified similar noncoding CGG repeat expansions in two other diseases: oculopharyngeal myopathy with leukoencephalopathy and oculopharyngodistal myopathy, in LOC642361 / NUTM2B-AS1 and LRP12 , respectively. These findings expand our knowledge of the clinical spectra of diseases caused by expansions of the same repeat motif, and further highlight how directly searching for expanded repeats can help identify mutations underlying diseases.