Aritoshi Iida

Transposon-like human element (THE1) repeats are classified as part of the ERVL (endogenous retrovirus-like) -MaLR family and were previously thought to be remnants derived from retroviral infections in the germ cells of ancient primates. At present, at least 60,561 THE1 repeats have been mapped in the human genome, and they are divided into four subfamilies: THE1A, THE1B, THE1C, and THE1D. Although these repeats are largely silenced in somatic cells through multiple mechanisms, some of them are known to influence gene functions and genomic structures, particularly under disease conditions. Recently, we happened to identify the CIR1 driven from THE1B in the individuals with sarcoid myopathy (SM), which is characterized by the non-caseating granulomatous inflammation recognized in skeletal muscles biopsy. Retrotrans-genomics based on the COFFEE method showed that various THE1B fusion transcripts (THE1B/FTs) and retrotransposon–associated genomic dynamics in muscle of SM, including (1) splicing of THE1B to neighborhood exons, (2) expression of THE1B associated long noncoding RNAs in the intergenic regions, (3) ectopic expression of tissue specific transcripts driven by THE1B in SM, and (4) identification of a read through transcript, SIRPB1-SIRPD. Seven of eight THE1B/FTs downregulated by tofacitinib in cutaneous sarcoidosis were confined to the granuloma associated macrophage in sarcoidosis. The remaining transcript, SMFT4 exhibited stronger expression in mesenchymal stem cells. In addition, ectopic co-expression of canonical and LINE1 and THE1A-exonizing IL23R transcripts were identified in SM. This directory of THE1B/FTs in SM may serve as a fundamental molecular basis for understanding the pathogenesis of sarcoidosis.

Sarcoidosis is a heterogenous inflammatory disease with complex genetic susceptibilities. Multi-ethnic genome-wide association studies have validated the association of sarcoidosis susceptibilities with single nucleotide variants on interleukin 23 receptor gene (IL23R), which is highly expressed in adrenal gland and testis, but not in skeletal muscle. Here we report concomitant ectopic expression of a canonical IL23R transcript and alternative polyadenylation of intron 6 of IL23R, leading to novel aberrant transcripts containing two retrotransposons, LINE1 (L1PA16) and THE1A, in the 3’ untranslated region (IL23R^L1-THE1A), in sarcoid myopathy (SM) compared with non-SM disease controls. RT-qPCR confirmed the expression of both transcripts in an additional sample set, including 14 SM and 29 non-SM. We also observed expression of both transcripts in T cells by single-nucleus RNA-sequencing. These findings should serve as an additional resource for investigating the role of IL23R transcript variants in the genetic background of sarcoidosis susceptibility and other inflammatory diseases.

ADSS1 myopathy, previously known as adenylosuccinate synthetase‐like 1 (ADSSL1) myopathy, is an autosomal recessive muscle disease caused by variants in ADSS1 (adenylosuccinate synthase 1). ADSS1 myopathy is complicated by respiratory muscle weakness or cardiomyopathy as well as limb muscle weakness. We analyzed two siblings with ADSS1 myopathy, both harboring compound heterozygous pathogenic variants (c.781G>A/c.919delA) in ADSS1 and provided details of their phenotypes together with muscle imaging and autopsy findings. Although it was reported that ADSS1 myopathy usually began with lower limb muscle weakness, our cases showed early involvement of the cervical paraspinal muscle, triceps brachii muscle, flexor digitorum superficialis and profundus muscles, rectus abdominis muscle, gluteus maximus and medius muscles, and cardiomyopathy. While a previous study reported that the trunk and hip muscles were relatively spared, atrophy of paraspinal muscles, gluteus medius and maximus muscles, and adductor muscles were observed. Our two siblings allowed for long‐term follow‐up and will be useful reference cases. We evaluated the frequency of fibers with nemaline bodies in various autopsied muscles and found that the ratio of fibers with nemaline bodies was lower compared to other nemaline myopathies. Postmortem examination revealed, for the first time, nemaline bodies in the diaphragm and myocardium, associated with respiratory failure and cardiomyopathy.

Transposon-like human element 1B (THE1B) originates from ancient retroviral sequences integrated into the primate genome approximately 50 million years ago, now accounting for at least 27,233 copies in the human genome, suggesting their extensive influence on human genomic architecture. Here we report identification of 19 THE1B fusion transcripts through short- and long-read RNA-seq analysis, 15 of which are previously unmapped, showing elevated expression in 16 individuals with sarcoid myopathy (SM), as compared to 400 controls with various other muscle diseases. Analysis of publicly available RNA-seq data indicated a correlation between the reduced expression of eight THE1B fusion transcripts and clinical improvement in individuals with cutaneous sarcoidosis receiving tofacitinib treatment. Single-cell or single-nucleus RNA-seq analyses of sarcoidosis not only confirmed these transcripts but also revealed a novel read-through transcript, SIRPB1-SIRPD, and TREM2.1, predominantly in granuloma-associated macrophages. The expression profiles of THE1B fusion transcripts in tuberculosis (TB) significantly differed from SM in single-cell RNA-seq data, suggesting that the differences between TB’s caseous granulomas and sarcoidosis’s non-caseous granulomas might be linked to disparate expression patterns of THE1B fusion transcripts. Our retrotrans-genomics approach has not only identified the genomic landscape of sarcoidosis but also provided new insights into its etiology.

The Japanese archipelago is a terminal location for human migration, and the contemporary Japanese people represent a unique population whose genomic diversity has been shaped by multiple migrations from Eurasia. We analyzed the genomic characteristics that define the genetic makeup of the modern Japanese population from a population genetics perspective from the genomic data of 9,287 samples obtained by high-coverage whole-genome sequencing (WGS) by the National Center Biobank Network. The dataset comprised populations from the Ryukyu Islands and other parts of the Japanese archipelago (Hondo). The Hondo population underwent two episodes of population decline during the Jomon period, corresponding to the Late Neolithic, and the Edo period, corresponding to the Early Modern era, while the Ryukyu population experienced a population decline during the shell midden period of the Late Neolithic in this region. Haplotype analysis suggested increased allele frequencies for genes related to alcohol and fatty acid metabolism, which were reported as loci that had experienced positive natural selection. Two genes related to alcohol metabolism were found to be 12,500 years out of phase with the time when they began to increase in the allele frequency; this finding indicates that the genomic diversity of Japanese people has been shaped by events closely related to agriculture and food production.

Circadian rhythm sleep–wake disorders (CRSWDs) are characterized by an inability to fall asleep and awaken at desired times. A subtype of CRSWDs, non-24-hour sleep–wake rhythm disorder (N24SWD), exhibits a free-running pattern of sleep–wake cycles that are not synchronized with the external 24-hour day. N24SWD occurs commonly in visually impaired individuals and rarely in sighted individuals. We have shown that the intrinsic circadian period (τ) determined under a forced desynchrony protocol is longer in sighted individuals with N24SWD than intermediate-type controls [ 1]. Therefore, it appears that prolonged τ and/or impaired entrainment mechanisms contribute to the pathogenesis of N24SWD. Some clock gene variants are associated with CRSWDs and transgenic animals carrying human clock variants exhibit altered τ [ 2]. These findings suggest that clock gene variants might disrupt the circadian clock system and lead to the onset of CRSWDs.

The Japanese archipelago is a terminal location for human migration, and the contemporary Japanese people represent a unique population whose genomic diversity has been shaped by multiple migrations from Eurasia. Through high-coverage whole-genome sequencing (WGS) analysis of 9,850 samples from the National Center Biobank Network, we analyzed the genomic characteristics that define the genetic makeup of the modern Japanese population from a population genetics perspective. The dataset comprised populations from the Ryukyu Islands and other parts of the Japanese archipelago (Hondo). Low frequency detrimental or pathogenic variants were found in these populations. The Hondo population underwent two episodes of population decline during the Jomon period, corresponding to the Late Neolithic, and the Edo period, corresponding to the Early Modern era, while the Ryukyu population experienced a population decline during the shell midden period of the Late Neolithic in this region. Genes related to alcohol and lipid metabolism were affected by positive natural selection. Two genes related to alcohol metabolism were found to be 12,500 years out of phase with the time when they began to be affected by positive natural selection; this finding indicates that the genomic diversity of Japanese people has been shaped by events closely related to agriculture and food production. Author summary The human population in the Japanese archipelago exhibits significant genetic diversity, with the Ryukyu Islands and other parts of the archipelago (Hondo) having undergone distinct evolutionary paths that have contributed to the genetic divergence of the populations in each region. In this study, whole genome sequencing of healthy individuals from national research hospital biobanks was utilized to investigate the genetic diversity of the Japanese population. Haplotypes were inferred from the genomic data, and a thorough population genetic analysis was conducted. The results indicated not only genetic differentiation between Hondo and the Ryukyu Islands, but also marked differences in past population size. In addition, gene genealogies were inferred from the haplotypes, and the patterns were scrutinized for evidence of natural selection. This analysis revealed unique traces of natural selection in East Asian populations, many of which were believed to be linked to dietary changes brought about by agriculture and food production.

DnaJ homolog, subfamily B, member 4, a member of the heat shock protein 40 chaperones encoded by DNAJB4 , is highly expressed in myofibers. We identified a heterozygous c.270 T>A (p.F90L) variant in DNAJB4 in a family with a dominantly inherited distal myopathy, in which affected members have specific features on muscle pathology represented by the presence of cytoplasmic inclusions and the accumulation of desmin, p62, HSP70 and DNAJB4 predominantly in type 1 fibers. Both Dnajb4- F90L knock-in and knockout mice developed muscle weakness and recapitulated the patient muscle pathology in the soleus muscle, where DNAJB4 has the highest expression. These data indicate that the identified variant is causative resulting in defective chaperone function and selective muscle degeneration in specific muscle fibers. This study demonstrates the importance of DNAJB4 in skeletal muscle proteostasis by identifying the associated chaperonopathy.

Missense variants in RNA-binding proteins (RBPs) underlie a spectrum of disease phenotypes, including amyotrophic lateral sclerosis, frontotemporal dementia, and inclusion body myopathy. Here, we present ten independent families with a severe, progressive muscular dystrophy, reminiscent of oculopharyngeal muscular dystrophy (OPMD) but of much earlier onset, caused by heterozygous frameshift variants in the RBP hnRNPA2/B1. All disease-causing frameshift mutations abolish the native stop codon and extend the reading frame, creating novel transcripts that escape nonsense-mediated decay and are translated to produce hnRNPA2/B1 protein with the same neomorphic C-terminal sequence. In contrast to previously reported disease-causing missense variants in HNRNPA2B1, these frameshift variants do not increase the propensity of hnRNPA2 protein to fibrillize. Rather, the frameshift variants have reduced affinity for the nuclear import receptor karyopherin β2, resulting in cytoplasmic accumulation of hnRNPA2 protein in cells and in animal models that recapitulate the human pathology. Thus, we expand the phenotypes associated with HNRNPA2B1 to include an early-onset form of OPMD caused by frameshift variants that alter its nucleocytoplasmic transport dynamics.