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Summary A promising approach to understanding the mechanistic basis of speech is to study disorders that affect speech without compromising other cognitive or motor functions. Stuttering, also known as stammering, has been linked to mutations in the lysosomal enzyme-targeting pathway, but how this remarkably specific speech deficit arises from mutations in a family of general “cellular housekeeping” genes is unknown. To address this question, we asked whether a missense mutation associated with human stuttering causes vocal or other abnormalities in mice. We compared vocalizations from mice engineered to carry a mutation in the Gnptab (N-acetylglucosamine-1-phosphotransferase subunits alpha/beta) gene with wild-type littermates. We found significant differences in the vocalizations of pups with the human Gnptab stuttering mutation compared to littermate controls. Specifically, we found that mice with the mutation emitted fewer vocalizations per unit time and had longer pauses between vocalizations and that the entropy of the temporal sequence was significantly reduced. Furthermore, Gnptab missense mice were similar to wild-type mice on an extensive battery of non-vocal behaviors. We then used the same language-agnostic metrics for auditory signal analysis of human speech. We analyzed speech from people who stutter with mutations in this pathway and compared it to control speech and found abnormalities similar to those found in the mouse vocalizations. These data show that mutations in the lysosomal enzyme-targeting pathway produce highly specific effects in mouse pup vocalizations and establish the mouse as an attractive model for studying this disorder. [ABSTRACT FROM AUTHOR]

The pre-mRNA life cycle requires intron processing; yet, how intron-processing defects influence splicing and gene expression is unclear. Here, we find that TTDN1/MPLKIP, which is encoded by a gene implicated in non-photosensitive trichothiodystrophy (NP-TTD), functionally links intron lariat processing to spliceosomal function. The conserved TTDN1 C-terminal region directly binds lariat debranching enzyme DBR1, whereas its N-terminal intrinsically disordered region (IDR) binds the intron-binding complex (IBC). TTDN1 loss, or a mutated IDR, causes significant intron lariat accumulation, as well as splicing and gene expression defects, mirroring phenotypes observed in NP-TTD patient cells. A Ttdn1 -deficient mouse model recapitulates intron-processing defects and certain neurodevelopmental phenotypes seen in NP-TTD. Fusing DBR1 to the TTDN1 IDR is sufficient to recruit DBR1 to the IBC and circumvents the functional requirement for TTDN1. Collectively, our findings link RNA lariat processing with splicing outcomes by revealing the molecular function of TTDN1. [Display omitted] • TTDN1 associates with DBR1 and promotes RNA lariat debranching in cells • TTDN1 links DBR1 to the intron-binding complex (IBC) • Loss of TTDN1 causes defects in splicing and in length-dependent gene expression • Ttdn1 Δ/Δ mice recapitulate neurodevelopmental phenotypes of trichothiodystrophy Townley et al. demonstrate that TTDN1 is involved in RNA processing, linking the lariat debranching enzyme to a spliceosomal complex. This function of TTDN1 is shown to be critical for proper splicing and transcription, and Ttdn1 loss in mice leads to phenotypes seen in patients with trichothiodystrophy. [ABSTRACT FROM AUTHOR]

Summary Pathological evidence for selective four-repeat (4R) tau deposition in certain dementias and exon 10-positioned MAPT mutations together suggest a 4R-specific role in causing disease. However, direct assessments of 4R toxicity have not yet been accomplished in vivo. Increasing 4R-tau expression without change to total tau in human tau-expressing mice induced more severe seizures and nesting behavior abnormality, increased tau phosphorylation, and produced a shift toward oligomeric tau. Exon 10 skipping could also be accomplished in vivo, providing support for a 4R-tau targeted approach to target 4R-tau toxicity and, in cases of primary MAPT mutation, eliminate the disease-causing mutation. [ABSTRACT FROM AUTHOR]

Summary: Tau aggregation occurs in neurodegenerative diseases including Alzheimer’s disease and many other disorders collectively termed tauopathies. trans-cellular propagation of tau pathology, mediated by extracellular tau aggregates, may underlie pathogenesis of these conditions. P301S tau transgenic mice express mutant human tau protein and develop progressive tau pathology. Using a cell-based biosensor assay, we screened anti-tau monoclonal antibodies for their ability to block seeding activity present in P301S brain lysates. We infused three effective antibodies or controls into the lateral ventricle of P301S mice for 3 months. The antibodies markedly reduced hyperphosphorylated, aggregated, and insoluble tau. They also blocked development of tau seeding activity detected in brain lysates using the biosensor assay, reduced microglial activation, and improved cognitive deficits. These data imply a central role for extracellular tau aggregates in the development of pathology. They also suggest that immunotherapy specifically designed to block trans-cellular aggregate propagation will be a productive treatment strategy. [Copyright &y& Elsevier]

Fibroblast growth factor 14 (FGF14) belongs to a distinct subclass of FGFs that is expressed in the developing and adult CNS. We disrupted the Fgf14 gene and introduced an Fgf14N-β-Gal allele that abolished Fgf14 expression and generated a fusion protein (FGF14N-β-gal) containing the first exon of FGF14 and β-galactosidase. Fgf14-deficient mice were viable, fertile, and anatomically normal, but developed ataxia and a paroxysmal hyperkinetic movement disorder. Neuropharmacological studies showed that Fgf14-deficient mice have reduced responses to dopamine agonists. The paroxysmal hyperkinetic movement disorder phenocopies a form of dystonia, a disease often associated with dysfunction of the putamen. Strikingly, the FGF14N-β-gal chimeric protein was efficiently transported into neuronal processes in the basal ganglia and cerebellum. Together, these studies identify a novel function for FGF14 in neuronal signaling and implicate FGF14 in axonal trafficking and synaptosomal function. [Copyright &y& Elsevier]

Mutations in DNA methyltransferase 3A (DNMT3A) have been detected in autism and related disorders, but how these mutations disrupt nervous system function is unknown. Here, we define the effects of DNMT3A mutations associated with neurodevelopmental disease. We show that diverse mutations affect different aspects of protein activity but lead to shared deficiencies in neuronal DNA methylation. Heterozygous DNMT3A knockout mice mimicking DNMT3A disruption in disease display growth and behavioral alterations consistent with human phenotypes. Strikingly, in these mice, we detect global disruption of neuron-enriched non-CG DNA methylation, a binding site for the Rett syndrome protein MeCP2. Loss of this methylation leads to enhancer and gene dysregulation that overlaps with models of Rett syndrome and autism. These findings define the effects of DNMT3A haploinsufficiency in the brain and uncover disruption of the non-CG methylation pathway as a convergence point across neurodevelopmental disorders., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

Mutations of the transcriptional regulator PHF6 cause the X-linked intellectual disability disorder Börjeson-Forssman-Lehmann syndrome (BFLS), but the pathogenesis of BFLS remains poorly understood. Here, we report a mouse model of BFLS, generated using a CRISPR-Cas9 approach, in which cysteine 99 within the PHD domain of PHF6 is replaced with phenylalanine (C99F). Mice harboring the patient-specific C99F mutation display deficits in cognitive functions, emotionality, and social behavior, as well as reduced threshold to seizures. Electrophysiological studies reveal that the intrinsic excitability of entorhinal cortical stellate neurons is increased in PHF6 C99F mice. Transcriptomic analysis of the cerebral cortex in C99F knockin mice and PHF6 knockout mice show that PHF6 promotes the expression of neurogenic genes and represses synaptic genes. PHF6-regulated genes are also overrepresented in gene signatures and modules that are deregulated in neurodevelopmental disorders of cognition. Our findings advance our understanding of the mechanisms underlying BFLS pathogenesis., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

The mammalian Sir2 ortholog Sirt1 plays an important role in metabolic regulation. However, the role of Sirt1 in the regulation of aging and longevity is still controversial. Here we demonstrate that brain-specific Sirt1-overexpressing (BRASTO) transgenic mice show significant life span extension in both males and females, and aged BRASTO mice exhibit phenotypes consistent with a delay in aging. These phenotypes are mediated by enhanced neural activity specifically in the dorsomedial and lateral hypothalamic nuclei (DMH and LH, respectively), through increased orexin type 2 receptor (Ox2r) expression. We identified Nk2 homeobox 1 (Nkx2-1) as a partner of Sirt1 that upregulates Ox2r transcription and colocalizes with Sirt1 in the DMH and LH. DMH/LH-specific knockdown of Sirt1, Nkx2-1, or Ox2r and DMH-specific Sirt1 overexpression further support the role of Sirt1/Nkx2-1/Ox2r-mediated signaling for longevity-associated phenotypes. Our findings indicate the importance of DMH/LH-predominant Sirt1 activity in the regulation of aging and longevity in mammals., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Evidence is emerging that the PGC-1 coactivators serve a critical role in skeletal muscle metabolism, function, and disease. Mice with total PGC-1 deficiency in skeletal muscle (PGC-1α(-/-)β(f/f/MLC-Cre) mice) were generated and characterized. PGC-1α(-/-)β(f/f/MLC-Cre) mice exhibit a dramatic reduction in exercise performance compared to single PGC-1α- or PGC-1β-deficient mice and wild-type controls. The exercise phenotype of the PGC-1α(-/-)β(f/f/MLC-Cre) mice was associated with a marked diminution in muscle oxidative capacity, together with rapid depletion of muscle glycogen stores. In addition, the PGC-1α/β-deficient muscle exhibited mitochondrial structural derangements consistent with fusion/fission and biogenic defects. Surprisingly, the proportion of oxidative muscle fiber types (I, IIa) was not reduced in the PGC-1α(-/-)β(f/f/MLC-Cre) mice. Moreover, insulin sensitivity and glucose tolerance were not altered in the PGC-1α(-/-)β(f/f/MLC-Cre) mice. Taken together, we conclude that PGC-1 coactivators are necessary for the oxidative and mitochondrial programs of skeletal muscle but are dispensable for fundamental fiber type determination and insulin sensitivity., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Sanfilippo syndrome type B (MPS IIIB) is a lysosomal storage disease resulting from a deficiency of N-acetyl-glucosaminidase (NAGLU) activity. In an attempt to correct the disease in the murine model of MPS IIIB, neonatal mice were treated with intracranial AAV2/5-NAGLU (AAV), syngeneic bone marrow transplant (BMT), or both (AAV/BMT). All treatments resulted in some improvement in clinical phenotype. Adeno-associated viral (AAV) treatment resulted in improvements in lifespan, motor function, hearing, time to activity onset, and daytime activity level, but no reduction of lysosomal storage. BMT resulted in improved hearing by 9 months, and improved circadian measures, but had no effect on lifespan, motor function, or central nervous system (CNS) lysosomal storage. AAV/BMT treatment resulted in improvements in hearing, time to activity onset, motor function, and reduced CNS lysosomal storage, but had no effect on lifespan. Combination therapy compared to either therapy alone resulted in synergistic effects on hearing and CNS lysosomal inclusions but antagonistic effects on motor function and lifespan. AAV alone is more efficacious than BMT or AAV/BMT treatment for lifespan. BMT was the least efficacious treatment by all measures. CNS-directed AAV treatment alone appears to be the preferred treatment, combining the most efficacy with the least toxicity of the approaches assessed.

The neuronal ceroid lipofuscinoses (Batten disease) are a group of inherited neurodegenerative diseases characterized by the progressive intralysosomal accumulation of autofluorescent material in many cells, visual defects, seizures, cognitive deficits, and premature death. Infantile neuronal ceroid lipofuscinosis (INCL) has the earliest onset ( approximately 1.5 years of age) and is caused by a deficiency in the lysosomal enzyme palmitoyl protein thioesterase-1 (PPT1). Currently there is no effective treatment for children with INCL. In this study, newborn PPT1-deficient mice received two (cortex), four (cortex and hippocampus), or six (cortex, hippocampus, and cerebellum) bilateral intracranial injections of AAV2-PPT1. The AAV-treated animals had localized increases in PPT1 activity, decreased autofluorescent material, improved histologic parameters, and increased brain mass. In addition, the treated animals had dose-dependent improvements in a battery of behavioral tests and improved interictal electroencephalographic tracings. However, there was neither a significant decrease in seizure frequency nor an increase in longevity even in INCL animals receiving six injections. These data suggest that early treatment of INCL using gene transfer techniques can be efficacious. However, higher levels or a broader distribution of PPT1 expression, or both, will be required for more complete correction of this neurodegenerative disease.