👤 Yuichiro Izumi

Brain-derived neurotrophic factor (BDNF) plays a pivotal role in neuronal development, synaptic plasticity, and cognitive function, and its dysregulation is implicated in various neurodegenerative and neuropsychiatric disorders. To noninvasively monitor dynamic changes in Bdnf expression in vivo, we developed a novel transgenic mouse line, Bdnf-AkaLuc transgenic (Tg) mice, in which the coding region of BDNF was replaced in a BAC transgene with a mutant luciferase, AkaLuc. This luciferase is optimized for the synthetic substrate AkaLumine, which emits near-infrared bioluminescence suitable for deep-tissue imaging. This engineered bioluminescence imaging (BLI) system, termed AkaBLI, enables robust and highly sensitive detection of bioluminescence in the brains of living mice, significantly outperforming our previous Bdnf-Luciferase Tg model. Using this system, we successfully visualized activity-dependent Bdnf mRNA induction in response to pilocarpine-induced status epilepticus. To overcome the limitations of repeated imaging, we identified optimal BLI intervals and established a hairless Bdnf-AkaLuc Tg line, facilitating long-term longitudinal monitoring. Furthermore, by crossing Bdnf-AkaLuc Tg mice with 5xFAD Alzheimer's disease model mice, we successfully visualized reductions in Bdnf expression in the brains of living 5xFAD mice. Our study introduces a powerful tool for noninvasive, continuous visualization of Bdnf regulation under both physiological and disease-related conditions. This imaging approach holds potential for advancing our understanding of BDNF-related brain function and for evaluating therapeutic strategies targeting BDNF in neurological disorders. Show less

Rosette-forming glioneuronal tumors (RGNTs) are rare, World Health Organization grade 1 tumors that typically arise around the fourth ventricle. However, cerebral hemisphere RGNTs have recently been reported, with some exhibiting clinical features resembling low-grade epilepsy-associated tumor (LEAT). We report a case of multifocal RGNT in a patient with drug-refractory epilepsy. A 14-year-old woman was incidentally found to have multifocal brain tumor involving the left temporal lobe and bilateral thalamus, she developed drug-resistant epilepsy ten years later and underwent surgery. Partial tumor resection and anterior temporal lobectomy were performed. Histopathology revealed a glioneuronal tumor with oligodendroglia-like cells, neurocytic rosette, and perivascular pseudorosette, exhibiting an infiltrative growth pattern extending into the white matter. Genetic analysis revealed Fibroblast Growth Factor Receptor 1 mutation. The methylation profile analysis matched the low-grade glioneuronal tumor class but did not yield to any subclass category. Finally, the tumor was diagnosed as RGNT-like low-grade glioneuronal tumor with dysembryoplastic neuroepithelial tumor (DNT) features. Cases presenting with a LEAT-like clinical course and exhibiting histopathological features of RGNT are often difficult to definitively distinguish from DNT based on histological and genetic findings. Epilepsy-associated RGNT may harbor genetic profiles distinct from those of prototypical RGNTs, highlighting the need for further investigation. Show less

This study aimed to establish variants in CBX1, encoding heterochromatin protein 1β (HP1β), as a cause of a novel syndromic neurodevelopmental disorder. Patients with CBX1 variants were identified, and clinician researchers were connected using GeneMatcher and physician referrals. Clinical histories were collected from each patient. To investigate the pathogenicity of identified variants, we performed in vitro cellular assays and neurobehavioral and cytological analyses of neuronal cells obtained from newly generated Cbx1 mutant mouse lines. In 3 unrelated individuals with developmental delay, hypotonia, and autistic features, we identified heterozygous de novo variants in CBX1. The identified variants were in the chromodomain, the functional domain of HP1β, which mediates interactions with chromatin. Cbx1 chromodomain mutant mice displayed increased latency-to-peak response, suggesting the possibility of synaptic delay or myelination deficits. Cytological and chromatin immunoprecipitation experiments confirmed the reduction of mutant HP1β binding to heterochromatin, whereas HP1β interactome analysis demonstrated that the majority of HP1β-interacting proteins remained unchanged between the wild-type and mutant HP1β. These collective findings confirm the role of CBX1 in developmental disabilities through the disruption of HP1β chromatin binding during neurocognitive development. Because HP1β forms homodimers and heterodimers, mutant HP1β likely sequesters wild-type HP1β and other HP1 proteins, exerting dominant-negative effects. Show less

Liver X receptors (LXR) α and β are a family of nuclear receptors that regulate lipogenesis by controlling the expression of the genes involved in the synthesis of fatty acids. MID1IP1, which encodes MIG12, is a target gene of LXR. MIG12 induces fatty acid synthesis by stimulating the polymerization-mediated activation of acetyl-CoA carboxylase (ACC). Here, we show that LXR's activation stimulates ACC polymerization in HepG2 cells by increasing the expression of MIG12. A knockdown of MID1IP1 abrogated the stimulation completely. The mutations of MIG12's leucine-zipper domain reduced the interaction between MIG12 and ACC, thus decreasing the MIG12's capacity to stimulate ACC polymerization. These results indicate that LXR's activation stimulates lipogenesis not only through the induction of the genes encoding lipogenic enzymes but also through MIG12's stimulation of ACC polymerization. Show less

Macroautophagy/autophagy is a lysosomal degradation system which plays a protective role against kidney injury. RUBCN/Rubicon (RUN domain and cysteine-rich domain containing, Beclin 1-interacting protein) inhibits the fusion of autophagosomes and lysosomes. However, its physiological role in kidney proximal tubular epithelial cells (PTECs) remains uncertain. In the current study, we analyzed the phenotype of newly generated PTEC-specific Show less

HDL-bound ApoM and albumin are protein chaperones for the circulating bioactive lipid, sphingosine 1-phosphate (S1P); in this role, they support essential extracellular S1P signaling functions in the vascular and immune systems. We previously showed that ApoM- and albumin-bound S1P exhibit differences in receptor activation and biological functions. Whether the physiological functions of S1P require chaperones is not clear. We examined ApoM-deficient, albumin-deficient, and double-KO (DKO) mice for circulatory S1P and its biological functions. In albumin-deficient mice, ApoM was upregulated, thus enabling S1P functions in embryonic development and postnatal adult life. The Show less

NFAT5 is an osmoregulated transcription factor that particularly increases expression of genes involved in protection against hypertonicity. Transcription factors often contain unstructured regions that bind co-regulatory proteins that are crucial for their function. The NH2-terminal region of NFAT5 contains regions predicted to be intrinsically disordered. We used peptide aptamer-based affinity chromatography coupled with mass spectrometry to identify protein preys pulled down by one or more overlapping 20 amino acid peptide baits within a predicted NH2-terminal unstructured region of NFAT5. We identify a total of 467 unique protein preys that associate with at least one NH2-terminal peptide bait from NFAT5 in either cytoplasmic or nuclear extracts from HEK293 cells treated with elevated, normal, or reduced NaCl concentrations. Different sets of proteins are pulled down from nuclear vs. cytoplasmic extracts. We used GeneCards to ascertain known functions of the protein preys. The protein preys include many that were previously known, but also many novel ones. Consideration of the novel ones suggests many aspects of NFAT5 regulation, interaction and function that were not previously appreciated, for example, hypertonicity inhibits NFAT5 by sumoylating it and the NFAT5 protein preys include components of the CHTOP complex that desumoylate proteins, an action that should contribute to activation of NFAT5. Show less

Congenital disorders of Glycosylation (CDG) are increasingly emerging as a major underlying etiology for patients with complex neurogenetic malformations and dysmorphic features. We describe a newborn female with arthrogryposis multiplex due to fetal akinesia secondary to CDG-DPAGT1. Pregnancy was complicated by reduced fetal movements. At birth, the patient was evaluated for intrauterine growth restriction, bilateral cataracts, and multiple joint contractures. She had markedly reduced spontaneous movements, hypotonia, weak cry, and poor suck. She had ventilator-dependent central respiratory depression. Brain MRI showed delayed myelination and an incomplete cerebellar vermis. Transferrin isoelectric focusing was suggestive of a type I congenital disorder of glycosylation. Sequencing revealed a homozygous missense mutation in dolichyl-phosphate N-acetylglucosaminephosphotransferase (DPAGT1), exon 3, p.Leu118Val, consistent with DPAGT1-CDG. There have been seventeen previously reported cases of DPAGT1-CDG, including two similar cases with multiple contractures. This case highlights the importance of considering congenital disorders of glycosylation in the differential diagnosis for arthrogryposis. Show less

Hypertrophic cardiomyopathy (HCM), which is inherited as an autosomal dominant trait, is the most prevalent hereditary cardiac disease. Although there are several reports on the systematic screening of mutations in the disease-causing genes in European and American populations, only limited information is available for Asian populations, including Japanese. Genetic screening of disease-associated mutations in 8 genes for sarcomeric proteins, MYH7, MYBPC3, MYL2, MYL3, TNNT2, TNNI3, TPM1, and ACTC, was performed by direct sequencing in 112 unrelated Japanese proband patients with familial HCM; 37 different mutations, including 13 novel ones in 5 genes, MYH7, MYBPC3, TNNT2, TNNI3, and TPM1, were identified in 49 (43.8%) patients. Among them, 3 carried compound heterozygous mutations in MYBPC3 or TNNT2. The frequency of patients carrying the MYBPC3, MYH7, and TNNT2 mutations were 19.6%, 10.7%, and 8.9%, respectively, and the most frequently affected genes in the northeastern and southwestern parts of Japan were MYBPC3 and MYH7, respectively. Several mutations were found in multiple unrelated proband patients, for which the geographic distribution suggested founder effects of the mutations. This study demonstrated the frequency and distribution of mutations in a large cohort of familial HCM in Japan. Show less