The promise of the BRAIN initiative: NIH strategies for understanding neural circuit function.

New neurotechnologies fueled by the BRAIN Initiative now allow investigators to map, monitor and modulate complex neural circuits, enabling the pursuit of research questions previously considered unapproachable. Yet it is the convergence of molecular neuroscience with the new systems neuroscience that promises the greatest future advances. This is particularly true for our understanding of nervous system disorders, some of which have known molecular drivers or pathology but result in unknown perturbations in circuit function.

Nicotinamide Pathway-Dependent Sirt1 Activation Restores Calcium Homeostasis to Achieve Neuroprotection in Spinocerebellar Ataxia Type 7.

Sirtuin 1 (Sirt1) is a NAD-dependent deacetylase capable of countering age-related neurodegeneration, but the basis of Sirt1 neuroprotection remains elusive. Spinocerebellar ataxia type 7 (SCA7) is an inherited CAG-polyglutamine repeat disorder. Transcriptome analysis of SCA7 mice revealed downregulation of calcium flux genes accompanied by abnormal calcium-dependent cerebellar membrane excitability.

Metabolic and Organelle Morphology Defects in Mice and Human Patients Define Spinocerebellar Ataxia Type 7 as a Mitochondrial Disease.

Spinocerebellar ataxia type 7 (SCA7) is a retinal-cerebellar degenerative disorder caused by CAG-polyglutamine (polyQ) repeat expansions in the ataxin-7 gene. As many SCA7 clinical phenotypes occur in mitochondrial disorders, and magnetic resonance spectroscopy of patients revealed altered energy metabolism, we considered a role for mitochondrial dysfunction. Studies of SCA7 mice uncovered marked impairments in oxygen consumption and respiratory exchange.

CCP1 promotes mitochondrial fusion and motility to prevent Purkinje cell neuron loss in mice.

A perplexing question in neurodegeneration is why different neurons degenerate. The Purkinje cell degeneration () mouse displays a dramatic phenotype of degeneration of cerebellar Purkinje cells. Loss of CCP1/Nna1 deglutamylation of tubulin accounts for neurodegeneration, but the mechanism is unknown.

Hormone-induced and DNA demethylation-induced relief of a tissue-specific and developmentally regulated block in transcriptional elongation.

Genome-wide studies have revealed that genes commonly have a high density of RNA polymerase II just downstream of the transcription start site. This has raised the possibility that genes are commonly regulated by transcriptional elongation, but this remains largely untested in vivo, particularly in vertebrates. Here, we show that the proximal promoter from the Rhox5 homeobox gene recruits polymerase II and begins elongating in all tissues and cell lines that we tested, but it only completes elongation in a tissue-specific and developmentally regulated manner.

Identification of the SCA21 disease gene: remaining challenges and promising opportunities.

This scientific commentary refers to ‘TMEM240 mutations cause spinocerebellar ataxia 21 with mental retardation and severe cognitive impairment’, by Delplanque . (doi: 10.1093/brain/awu202).

The expanding world of stem cell modeling of Huntington's disease: creating tools with a promising future.

Deconstructing the mechanistic basis of neurodegenerative disorders, such as Huntington's disease (HD), has been a particularly challenging undertaking, relying mostly on post-mortem tissue samples, non-neural cell lines from affected individuals, and model organisms. Two articles recently published in Cell Stem Cell report first the generation and characterization of induced pluripotent stem cell (iPSC)-derived models for HD, and second, the genetic correction of a disease-causing CAG expansion mutation in iPSCs from individuals with HD. Taken together, these two studies provide a framework for the production and validation of iPSC materials for human neurodegenerative disease research and yield crucial tools for investigating future therapies.