Leukodystrophies are a heterogeneous group of inherited neurodegenerative disorders characterized by abnormal white matter visible by brain imaging. It is estimated that at least 30% to 40% of individuals remain without a precise diagnosis despite extensive investigations. We mapped tremor-ataxia with central hypomyelination (TACH) to 10q22.3-23.1 in French-Canadian families and sequenced candidate genes within this interval. Two missense and one insertion mutations in five individuals with TACH were uncovered in POLR3A, which codes for the largest subunit of RNA polymerase III (Pol III). Because these families were mapped to the same locus as leukodystrophy with oligodontia (LO) and presented clinical and radiological overlap with individuals with hypomyelination, hypodontia and hypogonadotropic hypogonadism (4H) syndrome, we sequenced this gene in nine individuals with 4H and eight with LO. In total, 14 recessive mutations were found in 19 individuals with TACH, 4H, or LO, establishing that these leukodystrophies are allelic. No individual was found to carry two nonsense mutations. Immunoblots on 4H fibroblasts and on the autopsied brain of an individual diagnosed with 4H documented a significant decrease in POLR3A levels, and there was a more significant decrease in the cerebral white matter compared to that in the cortex. Pol III has a wide set of target RNA transcripts, including all nuclear-coded tRNA. We hypothesize that the decrease in POLR3A leads to dysregulation of the expression of certain Pol III targets and thereby perturbs cytoplasmic protein synthesis. This type of broad alteration in protein synthesis is predicted to occur in other leukoencephalopathies such as hypomyelinating leukodystrophy-3, caused by mutations in aminoacyl-tRNA synthetase complex-interacting multifunctional protein 1 (AIMP1).

Kabuki syndrome is a Mendelian intellectual disability syndrome caused by mutations in either of two genes (KMT2D and KDM6A) involved in chromatin accessibility. We previously showed that an agent that promotes chromatin opening, the histone deacetylase inhibitor (HDACi) AR-42, ameliorates the deficiency of adult neurogenesis in the granule cell layer of the dentate gyrus and rescues hippocampal memory defects in a mouse model of Kabuki syndrome (Kmt2d+/βGeo). Unlike a drug, a dietary intervention could be quickly transitioned to the clinic. Therefore, we have explored whether treatment with a ketogenic diet could lead to a similar rescue through increased amounts of beta-hydroxybutyrate, an endogenous HDACi. Here, we report that a ketogenic diet in Kmt2d+/βGeo mice modulates H3ac and H3K4me3 in the granule cell layer, with concomitant rescue of both the neurogenesis defect and hippocampal memory abnormalities seen in Kmt2d+/βGeo mice; similar effects on neurogenesis were observed on exogenous administration of beta-hydroxybutyrate. These data suggest that dietary modulation of epigenetic modifications through elevation of beta-hydroxybutyrate may provide a feasible strategy to treat the intellectual disability seen in Kabuki syndrome and related disorders.

Particular challenges exist for science education in the developing world, where limited resources require curricula designed to balance state-of-the-art knowledge with practical and political considerations in region-specific contexts. Project-based biology teaching is especially difficult to execute due to high infrastructural costs and limited teacher training. Here, we report the results of implementing short, challenging, and low-cost biology courses to high school and college students in Bolivia, designed and taught in collaboration between scientists from developed nations and local science instructors. We find our approach to be effective at transmitting advanced topics in disease modeling, microscopy, genome engineering, neuroscience, microbiology, and regenerative biology. We find that student learning through this approach was not significantly affected by their background, education level, socioeconomic status, or initial interest in the course. Moreover, participants reported a heightened interest in pursuing scientific careers after course completion. These results demonstrate efficacy of participatory learning in a developing nation, and suggest that similar techniques could drive scientific engagement in other developing economies.

Previous studies have shown that brief access to cocaine yields an increase in D2 receptor binding in the medial prefrontal cortex (mPFC), but that extended access to cocaine results in normalized binding of D2 receptors (i.e. the D2 binding returned to control levels). Extended access conditions have also been shown to produce increased expression of the NR2 subunit of the NMDA receptor in the mPFC. These results implicate disrupted glutamate and dopamine function within this area. Therefore, in the present study, we monitored glutamate and dopamine content within the mPFC during, or 24 hrs after, cocaine self-administration, in animals that experienced various amounts of exposure to the drug. Naïve subjects showed decreased glutamate, and increased dopamine, levels within the mPFC during cocaine self-administration. Exposure to 7 lhr daily cocaine self-administration sessions did not alter the response to self-administered cocaine, but resulted in decreased basal dopamine levels. While exposure to 17 lhr sessions also resulted in reduced basal dopamine levels, these animals showed increased dopaminergic, but completely diminished glutamatergic, response to self-administered cocaine. Finally, exposure to 17 cocaine self-administration sessions, the last ten of which being 6h sessions, resulted in diminished glutamatergic response to self-administered cocaine and reduced basal glutamate levels within the mPFC, while normalizing (i.e. causing a return to control levels) both the dopaminergic response to self-administered cocaine as well as basal dopamine levels within this area. These data demonstrate directly that the transition to escalated cocaine use involves progressive changes in dopamine and glutamate function within the mPFC.

The 4H syndrome (hypomyelination, hypodontia, hypogonadotropic hypogonadism) is a newly recognized leukodystrophy. The classical form is characterized by the association of hypomyelination, abnormal dentition, and hypogonadotropic hypogonadism, but the recent identification of 2 genes responsible for the syndrome demonstrates that these 3 main characteristics can be variably combined among “Pol-III related leukodystrophies”. The pathophysiology of this group of diseases is still to be elucidated and there are no neuropathological descriptions of brain tissue. We report the clinical, neuroradiological and neuropathological findings of a patient affected by 4H syndrome with confirmed POLR3A mutations. We found a marked loss of oligodendrocytes varying in severity in different brains regions accompanied by severe loss of myelin, moderately severe loss of axons and patchy perivascular regions of better-preserved white matter. There was relatively mild white matter astrogliosis and microgliosis. A macrophage reaction involving viable, normal-appearing oligodendroglia suggests the possibility of an immunologic process in this disorder. Cortical laminar astrogliosis and mineralization of layers I and II in particular was present. Thus, despite the uniformly hypomyelinating pattern seen on magnetic resonance imaging, neuropathological examination reveals a complex heterogeneous leukodystrophy with prominent neuro-axonal and glial involvement in this disorder.

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Background The cell cycle is a highly conserved, continuous process which controls faithful replication and division of cells. Single-cell technologies have enabled increasingly precise measurements of the cell cycle both as a biological process of interest and as a possible confounding factor. Despite its importance and conservation, there is no universally applicable approach to infer position in the cell cycle with high-resolution from single-cell RNA-seq data. Results Here, we present tricycle, an R/Bioconductor package, to address this challenge by leveraging key features of the biology of the cell cycle, the mathematical properties of principal component analysis of periodic functions, and the use of transfer learning. We estimate a cell-cycle embedding using a fixed reference dataset and project new data into this reference embedding, an approach that overcomes key limitations of learning a dataset-dependent embedding. Tricycle then predicts a cell-specific position in the cell cycle based on the data projection. The accuracy of tricycle compares favorably to gold-standard experimental assays, which generally require specialized measurements in specifically constructed in vitro systems. Using internal controls which are available for any dataset, we show that tricycle predictions generalize to datasets with multiple cell types, across tissues, species, and even sequencing assays. Conclusions Tricycle generalizes across datasets and is highly scalable and applicable to atlas-level single-cell RNA-seq data.

The atmospheric pressure that decreases with altitude affects lung physiology. However, these changes in physiology are not usually considered in ventilator design and testing. We argue that high altitude human populations require special attention to access the international supply of ventilators. Humans are naturally adapted to live at low altitude. Yet,~2% of the world's population permanently live at altitudes above 2500 meters 1. The majority of these populations live in areas that are either poor, such as Ethiopia, Ecuador and Bolivia, or highly controlled, such as Tibet 1. The small market size and low economic power of these regions have left them aside in the design of biomedical equipment, which usually does not consider their special environmental conditions and physiological adaptations. Worldwide, there is a shortage of many goods including intensive care unit (ICU) beds, facemasks, and ventilators due to the COVID-19 pandemic 2. This shortage has led to an international "stock market"-like process of bidding for these goods, in which many countries are left at an extreme disadvantage 3. Several international organizations, including the International Monetary Fund, the World Bank, and others, have been encouraged to provide loans to developing countries, but access to these goods is an issue that goes beyond money. Many countries have enacted export restrictions, and small orders are usually rejected to give preference to large purchases from powerful nations 3. This reduces the capability of less-affluent nations in both treating COVID-19 patients and preventing the further spread of the disease. Diverse pathological mechanisms in COVID-19 are under investigation, and respiratory symptoms predominate in the clinic. Physiologically, SARS-COV-2 cell entry is dependent on the cellular expression of ACE2 and TMPRSS2, and SARS-COV-2 likely binds to, and replicates in epithelial cells after entering the nasal cavity 4. SARS-CoV-2 then spreads from the nasal cavity into the lungs where it primarily infects ciliated epithelial cells that line the conducting airways. As ACE2 expression and receptors are also found in cells outside of the lungs 5 and COVID-19 patients have been reported to suffer from non-lung-related illness 6 , it is likely that SARS-CoV-2 infection is not limited to the nasal cavity and lungs. However, the majority of COVID-19 related deaths are caused by pulmonary illness. Therefore, the lungs are the primary focus of COVID-19 treatment efforts. Ventilators are essential to treat COVID-19, as they are the primary equipment needed to assist the breathing and gas exchange of critically ill patients. To this end, ICU ventilators have become an expensive commodity that most countries have fought to access. These fights have left