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The maintenance of metabolic homeostasis relies on the ability to flexibly transit between catabolic and anabolic states in response to insulin signaling. Here we show insulin-activated ATM is a critical mediator of this process, facilitating the swift transition between catabolic-and-anabolic fates of glucose by regulating the functional status of PKM2 and HIF1α. In Ataxia-Telangiectasia (A-T), these mechanisms are disrupted, resulting in intrinsic insulin resistance and glucose intolerance. Consequently, cells exhibit a compensatory dependence on glutamine as an alternative metabolite for energy metabolism. Cerebellar degeneration, a hallmark of A-T, is characterized by the pronounced vulnerability of Purkinje cells, attributed to their unexpected sensitivity to insulin. Supplementation with α-ketoglutarate, the α-keto acid backbone of glutamine, has demonstrated potentials in alleviating glutamine dependence and attenuating Purkinje cell degeneration. These findings suggest that peripheral metabolic deficiencies may contribute to sustained neurodegenerative changes in A-T, underscoring the importance of screening, monitoring and addressing these metabolic disruptions in patients. Insulin-activated ataxia-telangiectasia mutated (ATM) regulates glucose metabolism. Here the authors report that its disruption in a mouse model of ataxia-telangiectasia leads to insulin resistance, glutamine dependence, and selective Purkinje cell degeneration, while α-Ketoglutarate supplementation shows promise in mitigating neurodegeneration.

Purkinje cells are one of the major types of neurons that form the neural circuitry in the cerebellum essential for fine control of movement and posture. During development, Purkinje cells also are critically involved in the regulation of proliferation of progenitors of granule cells, the other major type of neurons in the cerebellum. The process that controls differentiation of Purkinje cells from their early precursors is poorly understood. Here we report that two closely related LIM-homeobox genes, Lhx1 and Lhx5, were expressed in the developing Purkinje cells soon after they exited the cell cycle and migrated out of the cerebellar ventricular zone. Double-mutant mice lacking function of both Lhx1 and Lhx5 showed a severe reduction in the number of Purkinje cells. In addition, targeted inactivation of Ldb1, which encodes a cofactor for all LIM-homeodomain proteins, resulted in a similar phenotype. Our studies thus provide evidence that these transcription regulators are essential for controlling Purkinje cell differentiation in the developing mammalian cerebellum.

Early changes in astrocyte energy metabolism are associated with late‐onset Alzheimer's disease (LOAD), but the underlying mechanism remains elusive. A previous study suggested an association between a synonymous SNP (rs1012672, C→T) in LRP6 gene and LOAD; and that is indeed correlated with diminished LRP6 gene expression in the frontal cortex region. The authors show that LRP6 is a unique Wnt coreceptor on astrocytes, serving as a bimodal switch that modulates their metabolic landscapes. The Wnt‐LRP6 mediated mTOR‐AKT axis is essential for sustaining glucose metabolism. In its absence, Wnt switches to activate the LRP6‐independent Ca2+‐PKC‐NFAT axis, resulting in a transcription network that favors glutamine and branched chain amino acids (BCAAs) catabolism over glucose metabolism. Exhaustion of these raw materials essential for neurotransmitter biosynthesis and recycling results in compromised synaptic, cognitive, and memory functions; priming for early changes that are frequently found in LOAD. The authors also highlight that intranasal supplementation of glutamine and BCAAs is effective in preserving neuronal integrity and brain functions, proposing a nutrient‐based method for delaying cognitive and memory decline when LRP6 cell surface levels and functions are suboptimal. Astrocytes are the major brain metabolic workhorses and altered energy metabolism is associated with late‐onset Alzheimer's disease. Differential Wnt downstream signaling modulates the metabolic landscape in these cells. Intranasal supplementation of enhanced demand on glutamine and branched‐chain amino acids may help to preserve neuronal integrity and brain functions; suggesting an alternative nutrient‐based method for delaying cognitive and memory decline.

In protein folding and secretion disorders, activation of endoplasmic reticulum (ER) stress signaling (ERSS) protects cells, alleviating stress that would otherwise trigger apoptosis. Whether the stress-surviving cells resume normal function is not known. We studied the in vivo impact of ER stress in terminally differentiating hypertrophic chondrocytes (HCs) during endochondral bone formation. In transgenic mice expressing mutant collagen X as a consequence of a 13-base pair deletion in Col10a1 (13del), misfolded alpha1(X) chains accumulate in HCs and elicit ERSS. Histological and gene expression analyses showed that these chondrocytes survived ER stress, but terminal differentiation is interrupted, and endochondral bone formation is delayed, producing a chondrodysplasia phenotype. This altered differentiation involves cell-cycle re-entry, the re-expression of genes characteristic of a prehypertrophic-like state, and is cell-autonomous. Concomitantly, expression of Col10a1 and 13del mRNAs are reduced, and ER stress is alleviated. ERSS, abnormal chondrocyte differentiation, and altered growth plate architecture also occur in mice expressing mutant collagen II and aggrecan. Alteration of the differentiation program in chondrocytes expressing unfolded or misfolded proteins may be part of an adaptive response that facilitates survival and recovery from the ensuing ER stress. However, the altered differentiation disrupts the highly coordinated events of endochondral ossification culminating in chondrodysplasia.

The highly conserved and ubiquitously expressed transcription factor Yin Yang 1 ( Yy1 ), was named after its dual functions of both activating and repressing gene transcription. Yy1 plays complex roles in various fundamental biological processes such as the cell cycle progression, cell proliferation, survival, and differentiation. Patients with dominant Yy1 mutations suffer from central nervous system (CNS) developmental defects. However, the role of Yy1 in mammalian CNS development remains to be fully elucidated. The isthmus organizer locates to the mid-hindbrain (MHB) boundary region and serves as the critical signaling center during midbrain and cerebellar early patterning. To study the function of Yy1 in mesencephalon/ rhombomere 1 (mes/r1) neuroepithelium development, we utilized the tissue-specific Cre-LoxP system and generated a conditional knockout mouse line to inactivate Yy1 in the MHB region. Mice with Yy1 deletion in the mes/r1 region displayed cerebellar agenesis and dorsal midbrain hypoplasia. The Yy1 deleted neuroepithelial cells underwent cell cycle arrest and apoptosis, with the concurrent changes of cell cycle regulatory genes expression, as well as activation of the p53 pathway. Moreover, we found that Yy1 is involved in the transcriptional activation of Wnt1 in neural stem cells. Thus, our work demonstrates the involvement of Yy1 in cerebellar agenesis and the critical function of Yy1 in mouse early MHB neuroepithelium maintenance and development.

MicroRNAs (miRNAs) are small non-coding RNAs that play crucial roles in post-transcriptional gene regulation. Poly(A) RNA polymerase D5 (PAPD5) catalyzes the addition of adenosine to the 3′ end of miRNAs. In this study, we demonstrate that the Yin Yang 1 protein, a transcriptional repressor of PAPD5, is recruited to both RNA foci and protein aggregates, resulting in an upregulation of PAPD5 expression in Huntington’s disease (HD). Additionally, we identify a subset of PAPD5-regulated miRNAs with increased adenylation and reduced expression in our disease model. We focus on miR-7-5p and find that its reduction causes the activation of the TAB2-mediated TAK1–MKK4–JNK pro-apoptotic pathway. This pathway is also activated in induced pluripotent stem cell-derived striatal neurons and post-mortem striatal tissues isolated from HD patients. In addition, we discover that a small molecule PAPD5 inhibitor, BCH001, can mitigate cell death and neurodegeneration in our disease models. This study highlights the importance of PAPD5-mediated miRNA dysfunction in HD pathogenesis and suggests a potential therapeutic direction for the disease. PAPD5 is responsible for adenylation of microRNAs. Here, the authors show that elevated level of PAPD5 enhances the adenylation and reduced expression of miR-7-5p . As a result, expression of TAB2, a target of miR-7-5p , is induced triggering neuronal apoptosis in Huntington’s disease.

In the cerebellar cortex, Purkinje cells (PCs) receive signals from different inputs through their extensively branched dendrites and serve as an integration centre. Defects in the dendritic development of PCs thus disrupt cerebellar circuitry and cause ataxia. Here we report that specific inactivation of both Lhx1 and Lhx5 in postnatal PCs results in ataxic mutant mice with abnormal dendritic development. The PCs in the mutants have reduced expression of Espin, an F-actin cytoskeleton regulator. We show that Espin expression is transcriptionally activated by Lhx1/5. Downregulation of Espin leads to F-actin mislocalization, thereby impairing dendritogenesis and dendritic spine maturation in the PCs. The mutant PCs therefore fail to form proper synapses and show aberrant electrophysiological properties. By overexpressing Espin, we can successfully rescue the defects in the mutant PCs. Our findings suggest that Lhx1/5, through regulating Espin expression, control dendritogenesis and spine morphogenesis in postnatal PCs. Purkinje cells (PCs) receive signals from different inputs through their extensively branched dendrites and dysregulation of this process leads to ataxia and other diseases. Here the authors show that the LIM-homeodomain transcription factors Lhx1 and Lhx5 govern dendritogenesis and dendritic spine morphogenesis in postnatal PCs through regulating Espin expression.

Neurodevelopmental disorders (NDDs) affect brain function and development, with 90% lacking approved treatments. Understanding their pathogenic mechanisms is critical for developing precision gene therapies. An autosomal recessive NDD associated with variants in the Mediator complex subunit 27 (MED27) gene is previously identified. The Mediator complex is essential for transcription initiation by bridging transcription factors (TFs) at enhancers to RNA polymerase II at promoters. All patients with MED27 variants exhibit cerebellar hypoplasia or atrophy, underscoring the cerebellum's heightened vulnerability to MED27 dysfunction. To investigate the disease mechanisms, in vitro stem cells carrying patient‐specific MED27 variants and in vivo mouse models with Med27 loss‐of‐function (LoF) are generated. These preclinical models recapitulate key patient phenotypes, including progressive cerebellar atrophy and motor deficits. Molecular analyses reveal that mutant MED27 destabilizes the Mediator complex, impairing its chromatin occupancy and altering chromatin interactions. Comprehensive transcriptomic profiling, including single‐cell resolution spatial transcriptomics, identifies dysregulation of downstream targets regulated by MED27, such as critical master regulatory TFs involved in neurogenesis and cerebellar development. This study elucidates a partial LoF mechanism underlying MED27‐associated NDDs and establishes a prototype for investigating NDDs caused by pathogenic variants in Mediator subunits. MED27 is one of the 26 subunits in the human Mediator complex (MED). Neurodevelopmental disorder‐causing MED27 genetic variants induce instability of MED, leading to disrupted DNA occupancy, altered chromatin interaction, and subsequent transcriptional dysregulation of critical downstream genes, including master regulatory transcription factors essential for early neurogenesis and cerebellar development.

Bone mass is maintained by continuous remodeling through repeated cycles of bone resorption by osteoclasts and bone formation by osteoblasts. This remodeling process is regulated by many systemic and local factors. We identified collagen triple helix repeat containing-1 (Cthrc1) as a downstream target of bone morphogenetic protein-2 (BMP2) in osteochondroprogenitor-like cells by PCR-based suppression subtractive hybridization followed by differential hybridization, and found that Cthrc1 was expressed in bone tissues in vivo. To investigate the role of Cthrc1 in bone, we generated Cthrc1-null mice and transgenic mice which overexpress Cthrc1 in osteoblasts (Cthrc1 transgenic mice). Microcomputed tomography (micro-CT) and bone histomorphometry analyses showed that Cthrc1-null mice displayed low bone mass as a result of decreased osteoblastic bone formation, whereas Cthrc1 transgenic mice displayed high bone mass by increase in osteoblastic bone formation. Osteoblast number was decreased in Cthrc1-null mice, and increased in Cthrc1 transgenic mice, respectively, while osteoclast number had no change in both mutant mice. In vitro, colony-forming unit (CFU) assays in bone marrow cells harvested from Cthrc1-null mice or Cthrc1 transgenic mice revealed that Cthrc1 stimulated differentiation and mineralization of osteoprogenitor cells. Expression levels of osteoblast specific genes, ALP, Col1a1, and Osteocalcin, in primary osteoblasts were decreased in Cthrc1-null mice and increased in Cthrc1 transgenic mice, respectively. Furthermore, BrdU incorporation assays showed that Cthrc1 accelerated osteoblast proliferation in vitro and in vivo. In addition, overexpression of Cthrc1 in the transgenic mice attenuated ovariectomy-induced bone loss. Our results indicate that Cthrc1 increases bone mass as a positive regulator of osteoblastic bone formation and offers an anabolic approach for the treatment of osteoporosis.

Background: Shellfish hypersensitivity is among the most common food allergies. A murine model of IgE-mediated shrimp allergy has been established in our laboratory. The aim of this study is to determine the intestinal histological changes and cytokine expression profile of this model sensitized with the major shellfish allergen tropomyosin. Methods: Female Balb/c mice orally sensitized and challenged with recombinant tropomyosin were sacrificed. Continuous sections of duodenum, jejunum and ileum were prepared using the Swiss roll technique for histological and immunological analysis. Duodenal epithelial cell apoptosis and migration were examined. mRNA expression of IL-4, IL-6, IL-10, IL-13, IL-18 and IFN-γ in intestinal tissue was measured via RT-PCR. Results: In tropomyosin-sensitized and challenged mice, an increased number of eosinophils, mast cells and goblet cells was found 24 h after challenge. There were also increased mast cell and goblet cell numbers at 72 h after challenge, but the level of eosinophils decreased. Differences compared with control mice are most prominent at the duodenum compared to the distal regions. In addition, TUNEL assay indicates a significantly higher apoptosis rate in sensitized mice sacrificed 72 h after challenge, and mRNA expression showed a biased Th2/Th1 cytokine profile and a higher level of murine mast cell protease 1. Conclusions: This study documented a multitude of histological and immunological changes in the gut in a murine model of shrimp allergy. Even without repetitive intragastric challenge, shrimp tropomyosin induces an increase in the number of inflammatory cells to varying degrees within the small intestine. This model provides an important tool for testing new therapeutic interventions.