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Mouse Impact is the sole imprinted gene mapped to chromosome 18 to date. Despite its remarkable evolutionary conservation, human IMPACT was shown to escape genomic imprinting. Here we identified Hrh4 and Osbpl1 as the distal and proximal nearest neighbors of Impact, respectively, and found that both genes are expressed biallelically. Thus, in contrast with most imprinted genes, Impact fails to show apparent physical clustering with other imprinted genes. Since Impact not only lies in an intergenic region but also consists of 11 exons, it does not seem to be an imprinted gene generated by a retrotransposition. Hazardous effects of overexpressed Impact, a genomic segment containing paralogues of Hrh4 and Osbpl1 but not of Impact, and enhanced promoter activity in the mouse led us to propose an alternative model. This model assumes that segmental duplication followed by enhancement of the promoter activity in the lineage to mouse is responsible for the species-specific imprinting of Impact. [ABSTRACT FROM PUBLISHER]

The sparkling enope squid,Watasenia scintillans, is a deep-sea mollusk inhabiting the western part of the Pacific Ocean. It has the peculiar ability to illuminate its body without the involvement of other organisms. In this study, we extracted the brain DNA from a single squid female caught in the Japan Sea and determined the complete genome sequence of its mitochondrial DNA using the Illumina sequencing platform. The circular sequence is 20,089 bp in length. Using the next-generation sequencing data, we also estimated the mean copy number of mitochondria per cell in the brain to be 108 by comparing the depths of the read data in the nuclear and mitochondrial genomes. The haploid genome size was calculated to be 4.78 Gb. Six heteroplasmy sites were also identified, together with their allele frequencies, in this individual. Our methodology is shown to be useful in mitochondrion-related studies. [ABSTRACT FROM PUBLISHER]

Lampreys are eel-like jawless fishes evolutionarily positioned between invertebrates and vertebrates, and have been used as model organisms to explore vertebrate evolution. In this study we determined the complete genome sequence of the mitochondrial DNA of the Japanese river lamprey,Lethenteron japonicum, using next-generation sequencers. The sequence was 16,272 bp in length. The gene content and order were identical to those of the sea lamprey,Petromyzon marinus, which has been the reference among lamprey species. However, the sequence similarity was less than 90%, suggesting the need for the whole-genome sequencing ofL. japonicum. [ABSTRACT FROM PUBLISHER]

Context: Primary adrenal insufficiency (PAI) is a life-threatening condition characterized by the inability of the adrenal cortex to produce sufficient steroid hormones. E3 ubiquitin protein ligase zinc and ring finger 3 (ZNRF3) is a negative regulator of Wnt/β-catenin signaling. R-spondin 1 (RSPO1) enhances Wnt/β-catenin signaling via binding and removal of ZNRF3 from the cell surface., Objective: This work aimed to explore a novel genetic form of PAI., Methods: We analyzed 9 patients with childhood-onset PAI of biochemically and genetically unknown etiology using array comparative genomic hybridization. To examine the functionality of the identified single-exon deletions of ZNRF3 exon 2, we performed three-dimensional (3D) structure modeling and in vitro functional studies., Results: We identified various-sized single-exon deletions encompassing ZNRF3 exon 2 in 3 patients who showed neonatal-onset adrenal hypoplasia with glucocorticoid and mineralocorticoid deficiencies. Reverse-transcriptase polymerase chain reaction (RT-PCR) analysis showed that the 3 distinct single-exon deletions were commonly transcribed into a 126-nucleotide deleted mRNA and translated into 42-amino acid deleted protein (ΔEx2-ZNRF3). Based on 3D structure modeling, we predicted that interaction between ZNRF3 and RSPO1 would be disturbed in ΔEx2-ZNRF3, suggesting loss of RSPO1-dependent activation of Wnt/β-catenin signaling. Cell-based functional assays with the TCF-LEF reporter showed that RSPO1-dependent activation of Wnt/β-catenin signaling was attenuated in cells expressing ΔEx2-ZNRF3 as compared with those expressing wild-type ZNRF3., Conclusion: We provided genetic evidence linking deletions encompassing ZNRF3 exon 2 and congenital adrenal hypoplasia, which might be related to constitutive inactivation of Wnt/β-catenin signaling by ΔEx2-ZNRF3., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Endocrine Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Fusion genes involving MEF2D have recently been identified in precursor B-cell acute lymphoblastic leukemia, mutually exclusive of the common risk stratifying genetic abnormalities, although their true incidence and associated clinical characteristics remain unknown. We identified 16 cases of acute lymphoblastic leukemia and 1 of lymphoma harboring MEF2D fusions, including MEF2D-BCL9 (n=10), MEF2D-HNRNPUL1 (n=6), and one novel MEF2D-HNRNPH1 fusion. The incidence of MEF2D fusions overall was 2.4% among consecutive precursor B-cell acute lymphoblastic leukemia patients enrolled onto a single clinical trial. They frequently showed a cytoplasmic μ chain-positive pre-B immunophenotype, and often expressed an aberrant CD5 antigen. Besides up- and down-regulation of HDAC9 and MEF2C , elevated GATA3 expression was also a characteristic feature of MEF2D fusion-positive patients. Mutations of PHF6 , recurrent in T-cell acute lymphoblastic leukemia, also showed an unexpectedly high frequency (50%) in these patients. MEF2D fusion-positive patients were older (median age 9 years) with elevated WBC counts (median: 27,300/ml) at presentation and, as a result, were mostly classified as NCI high risk. Although they responded well to steroid treatment, MEF2D fusion-positive patients showed a significantly worse outcome, with 53.3% relapse and subsequent death. Stem cell transplantation was ineffective as salvage therapy. Interestingly, relapse was frequently associated with the presence of CDKN2A/CDKN2B gene deletions. Our observations indicate that MEF2D fusions comprise a distinct subgroup of precursor B-cell acute lymphoblastic leukemia with a characteristic immunophenotype and gene expression signature, associated with distinct clinical features., (Copyright© 2019 Ferrata Storti Foundation.)

Arc is a unique immediate early gene (IEG) whose expression is induced as synapses are modified during learning. Newly-synthesized Arc mRNA is rapidly transported throughout dendrites and localizes near recently activated synapses. Arc mRNA levels are regulated by rapid degradation, which is accelerated by synaptic activity in a translation-dependent process. One possible mechanism is nonsense-mediated mRNA decay (NMD), which depends on the presence of a splice junction in the 3'UTR. Here, we test this hypothesis using transgenic mice that express EGFP-Arc . Because the transgene was constructed from Arc cDNA, it lacks intron structures in the 3'UTR that are present in the endogenous Arc gene. NMD depends on the presence of proteins of the exon junction complex (EJC) downstream of a stop codon, so EGFP-Arc mRNA should not undergo NMD. Assessment of Arc mRNA rundown in the presence of the transcription inhibitor actinomycin-D confirmed delayed degradation of EGFP-Arc mRNA. EGFP-Arc mRNA and protein are expressed at much higher levels in transgenic mice under basal and activated conditions but EGFP-Arc mRNA does not enter dendrites efficiently. In a physiological assay in which cycloheximide (CHX) was infused after induction of Arc by seizures, there were increases in endogenous Arc mRNA levels consistent with translation-dependent Arc mRNA decay but this was not seen with EGFP-Arc mRNA. Taken together, our results indicate: (1) Arc mRNA degradation occurs via a mechanism with characteristics of NMD; (2) rapid dendritic delivery of newly synthesized Arc mRNA after induction may depend in part on prior splicing of the 3'UTR.

Fusion genes involving ZNF384 have recently been identified in B-cell precursor acute lymphoblastic leukemia, and 7 fusion partners have been reported. We further characterized this type of fusion gene by whole transcriptome sequencing and/or polymerase chain reaction. In addition to previously reported genes, we identified BMP2K as a novel fusion partner for ZNF384 Including the EP300-ZNF384 that we reported recently, the total frequency of ZNF384-related fusion genes was 4.1% in 291 B-cell precursor acute lymphoblastic leukemia patients enrolled in a single clinical trial, and TCF3-ZNF384 was the most recurrent, with a frequency of 2.4%. The characteristic immunophenotype of weak CD10 and aberrant CD13 and/or CD33 expression was revealed to be a common feature of the leukemic cells harboring ZNF384-related fusion genes. The signature gene expression profile in TCF3-ZNF384-positive patients was enriched in hematopoietic stem cell features and related to that of EP300-ZNF384-positive patients, but was significantly distinct from that of TCF3-PBX1-positive and ZNF384-fusion-negative patients. However, clinical features of TCF3-ZNF384-positive patients are markedly different from those of EP300-ZNF384-positive patients, exhibiting higher cell counts and a younger age at presentation. TCF3-ZNF384-positive patients revealed a significantly poorer steroid response and a higher frequency of relapse, and the additional activating mutations in RAS signaling pathway genes were detected by whole exome analysis in some of the cases. Our observations indicate that ZNF384-related fusion genes consist of a distinct subgroup of B-cell precursor acute lymphoblastic leukemia with a characteristic immunophenotype, while the clinical features depend on the functional properties of individual fusion partners., (Copyright© Ferrata Storti Foundation.)

Context: Pseudohypoparathyroidism type 1b (PHP-1b) results from methylation defects at the G protein stimulatory α subunit (GNAS) exon A/B-differentially methylated region (DMR). Although microduplications in the GNAS region were recently identified in two PHP-1b patients, genetic information on these patients remained fragmentary., Case Description: A 20-year-old Japanese male and his mother presented with hypocalcemia and elevated blood levels of intact PTH. The proband had a maternal uncle who was previously diagnosed with PHP-1b. Methylation-specific multiplex ligation-dependent probe amplification, array-based comparative genomic hybridization, pyrosequencing, fluorescence in situ hybridization, and whole-genome sequencing were performed for this family. The proband, mother, and uncle carried maternally derived approximately 133-kb duplication-triplication-duplication rearrangements at 20q13.32 involving NESP55, NESPAS, XLαs, and exon A/B-DMR but not STX16 or the Gsα coding region. These individuals exhibited partial methylation defects of NESP55-, NESPAS-, and XLαs-DMRs, which were ascribable to the increased copy numbers of these regions retaining the maternally derived methylation pattern and loss of methylation of exon A/B-DMR, which was inexplicable by the copy-number alterations. Fusion junctions of the rearrangement resided within non-repeat sequences and were accompanied by short-templated insertions., Conclusions: Our results indicate that maternally derived copy-number gains in the GNAS region mediated by nonhomologous end-joining and/or by break-induced replication can underlie autosomal dominant PHP-1b. These rearrangements likely affect methylation of exon A/B-DMR by disconnecting or disrupting its cis-acting regulator(s). This study provides a novel example of human disorders resulting from functional disturbance in the cis-regulatory machinery of DNA methylation.

The Illumina's Infinium HumanMethylation450 (HM450) BeadChip array provides a simultaneous examination of DNA methylation status of more than 480,000 CpG sites in the human genome. Its relatively simple protocol is achieved by employing a hybridization methodology followed by single-base extension reactions. However, nucleotide variations among individuals in the hybridization probe sequences can affect the results, i.e. estimates of methylation levels. To investigate possible effects of maternal nutritional conditions on the extent of epigenetic alterations in utero, we examined genome-wide DNA methylation profiles of 33 chorionic villi samples collected in Japan (GEO accession number GSE62733), and revealed using Smirnov-Grubbs' outlier test that epigenetic alterations accumulate in placentas under adverse in utero environments. In that study, we compiled a list of HM450 probes overlapping with the reported nucleotide variants in the Phase 3 dataset (release 20130502) of the 1000 Genomes Project. We excluded the probes whose sequences overlapped with variants with minor allele frequency (MAF) higher than 1% in the Japanese population from identified methylation outliers, to diminish the number of outliers that could have been spuriously identified due to variants at/near the target CpG sites. We herein compiled lists of HM450 probes with MAF information of the African, European, American, South Asian and East Asian populations, in addition to the Japanese population. The provided lists are useful for methylome analyses for human populations using the HM450 BeadChip arrays.