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The 13th Symposium on Polar Science/Ordinary sessions [OG] Polar geosciences, Wed. 16 Nov.

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.

The 13th Symposium on Polar Science/Ordinary sessions [OG] Polar geosciences, Wed. 16 Nov.

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.

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

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.

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.

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.

The 11th Symposium on Polar Science/Ordinary sessions: [OG] Polar Geosciences, Wed. 2 Dec.

The 11th Symposium on Polar Science/Ordinary sessions: [OG] Polar Geosciences, Poster presentations, Mon. 16 Nov. - Fri. 18 Dec.

The 11th Symposium on Polar Science/Ordinary sessions: [OG] Polar Geosciences, Poster presentations, Mon. 16 Nov. - Fri. 18 Dec.

The 11th Symposium on Polar Science/Ordinary sessions: [OM] Polar Meteorology and Glaciology, Poster presentations, Mon. 16 Nov. - Fri. 18 Dec.

Ultrasound can be clearly perceived by bone-conduction, and this "bone-conducted ultrasound (BCU)" can transmit speech information by using amplitude modulation (AM). Further, BCU can be perceived not only on the head but also on the distal parts of the body like the neck, trunk and arms. This "distantly-presented BCU" can be applied to the novel interface that can transmit sound information selectively to specific users who touches the vibrator. However, the ability to transmit sound information of distantly-presented BCU is unclear. First, to assess frequency discrimination ability, difference limens for frequency (DLFs) of the distantly-presented AM-BCU were measured with/without a low-pass masking noise that masked the self-demodulated components generated by the nonlinearity of biological tissues. DLFs comparable to that of air-conducted sounds were observed, whereas DLFs significantly increased above 1 kHz under the masking condition. These results suggest that practical frequency discrimination ability can be obtained even when BCUs were presented to distal body parts. Additionally, it is indicated that the demodulated components may contribute to transmitting frequency information above 1 kHz. Second, monosyllable articulation and word intelligibility tests were conducted in Japanese. The intelligibility and articulation at the neck were 55% and 38% respectively, whereas they decreased as the stimulus placement gets farther from the head. The results suggest the distantly-presented BCU device can be applied to transmission of speech information.

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.

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.

Higuchi et al. identify recessive mutations in the mitochondrial gene, cytochrome c oxidase assembly factor 7 (COA7) in four unrelated patients with an axonal-type motor and sensory neuropathy with ataxia. Genetic, histopathological, radiological and functional data support a causative role for loss-of-function COA7 mutations in the observed phenotype., Several genes related to mitochondrial functions have been identified as causative genes of neuropathy or ataxia. Cytochrome c oxidase assembly factor 7 (COA7) may have a role in assembling mitochondrial respiratory chain complexes that function in oxidative phosphorylation. Here we identified four unrelated patients with recessive mutations in COA7 among a Japanese case series of 1396 patients with Charcot-Marie-Tooth disease (CMT) or other inherited peripheral neuropathies, including complex forms of CMT. We also found that all four patients had characteristic neurological features of peripheral neuropathy and ataxia with cerebellar atrophy, and some patients showed leukoencephalopathy or spinal cord atrophy on MRI scans. Validated mutations were located at highly conserved residues among different species and segregated with the disease in each family. Nerve conduction studies showed axonal sensorimotor neuropathy. Sural nerve biopsies showed chronic axonal degeneration with a marked loss of large and medium myelinated fibres. An immunohistochemical assay with an anti-COA7 antibody in the sural nerve from the control patient showed the positive expression of COA7 in the cytoplasm of Schwann cells. We also observed mildly elevated serum creatine kinase levels in all patients and the presence of a few ragged-red fibres and some cytochrome c oxidase-negative fibres in a muscle biopsy obtained from one patient, which was suggestive of subclinical mitochondrial myopathy. Mitochondrial respiratory chain enzyme assay in skin fibroblasts from the three patients showed a definitive decrease in complex I or complex IV. Immunocytochemical analysis of subcellular localization in HeLa cells indicated that mutant COA7 proteins as well as wild-type COA7 were localized in mitochondria, which suggests that mutant COA7 does not affect the mitochondrial recruitment and may affect the stability or localization of COA7 interaction partners in the mitochondria. In addition, Drosophila COA7 (dCOA7) knockdown models showed rough eye phenotype, reduced lifespan, impaired locomotive ability and shortened synaptic branches of motor neurons. Our results suggest that loss-of-function COA7 mutation is responsible for the phenotype of the presented patients, and this new entity of disease would be referred to as spinocerebellar ataxia with axonal neuropathy type 3.