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Interindividual genetic variation affects the susceptibility to and progression of many diseases1,2. However, efforts to study how individual human brains differ in normal development and disease phenotypes are limited by the paucity of faithful cellular human models, and the difficulty of scaling current systems to represent multiple people. Here we present human brain Chimeroids, a highly reproducible, multidonor human brain cortical organoid model generated by the co-development of cells from a panel of individual donors in a single organoid. By reaggregating cells from multiple single-donor organoids at the neural stem cell or neural progenitor cell stage, we generate Chimeroids in which each donor produces all cell lineages of the cerebral cortex, even when using pluripotent stem cell lines with notable growth biases. We used Chimeroids to investigate interindividual variation in the susceptibility to neurotoxic triggers that exhibit high clinical phenotypic variability: ethanol and the antiepileptic drug valproic acid. Individual donors varied in both the penetrance of the effect on target cell types, and the molecular phenotype within each affected cell type. Our results suggest that human genetic background may be an important mediator of neurotoxin susceptibility and introduce Chimeroids as a scalable system for high-throughput investigation of interindividual variation in processes of brain development and disease.

This study aimed to unravel the genetic factors underlying missing heritability in spinocerebellar ataxia type 17 (SCA17) caused by polyglutamine-encoding CAG/CAA repeat expansions in the TBPgene. Alleles with >49 CAG/CAA repeats are fully penetrant. Most patients, however, carry intermediate TBP41-49alleles that show incomplete penetrance.

Objective: The authors investigated the role of genetic factors in 35% C[O.sub.2]-induced panic attacks. Method: Ninety twins recruited from the general population were challenged with one-vital-capacity inhalations of 35% C[O.sub.2]-65% [O.sub.2]. Probandwise concordance rates were calculated and rates compared for monozygotic and for dizygotic twins. Results: A significantly higher concordance was found for 35% C[O.sub.2]-induced panic attacks among monozygotic than dizygotic twins (55.6% versus 12.5%). Conclusions: These results suggest a relevant role of genetic factors in 35% C[O.sub.2]-induced panic attacks.

Diverse types of glutamatergic pyramidal neurons mediate the myriad processing streams and output channels of the cerebral cortex1,2, yet all derive from neural progenitors of the embryonic dorsal telencephalon3,4. Here we establish genetic strategies and tools for dissecting and fate-mapping subpopulations of pyramidal neurons on the basis of their developmental and molecular programs. We leverage key transcription factors and effector genes to systematically target temporal patterning programs in progenitors and differentiation programs in postmitotic neurons. We generated over a dozen temporally inducible mouse Cre and Flp knock-in driver lines to enable the combinatorial targeting of major progenitor types and projection classes. Combinatorial strategies confer viral access to subsets of pyramidal neurons defined by developmental origin, marker expression, anatomical location and projection targets. These strategies establish an experimental framework for understanding the hierarchical organization and developmental trajectory of subpopulations of pyramidal neurons that assemble cortical processing networks and output channels.

The mammalian cerebral cortex has an unparalleled diversity of cell types, which are generated during development through a series of temporally orchestrated events that are under tight evolutionary constraint and are critical for proper cortical assembly and function1,2. However, the molecular logic that governs the establishment and organization of cortical cell types remains unknown, largely due to the large number of cell classes that undergo dynamic cell-state transitions over extended developmental timelines. Here we generate a comprehensive atlas of the developing mouse neocortex, using single-cell RNA sequencing and single-cell assay for transposase-accessible chromatin using sequencing. We sampled the neocortex every day throughout embryonic corticogenesis and at early postnatal ages, and complemented the sequencing data with a spatial transcriptomics time course. We computationally reconstruct developmental trajectories across the diversity of cortical cell classes, and infer their spatial organization and the gene regulatory programs that accompany their lineage bifurcation decisions and differentiation trajectories. Finally, we demonstrate how this developmental map pinpoints the origin of lineage-specific developmental abnormalities that are linked to aberrant corticogenesis in mutant mice. The data provide a global picture of the regulatory mechanisms that govern cellular diversification in the neocortex.

Objective: A functional polymorphism in the transcriptional control region upstream of the coding sequence of the 5-hydroxytryptamine transporter (5-HTT) has been reported. This polymorphism has been shown to influence the antidepressant response to fluvoxamine and paroxetine. The authors tested the hypothesis that the allelic variation of the 5-HTTlinked polymorphic region (5-HTTLPR) could influence the response of depressed patients to total sleep deprivation. Method: Sixty-eight drug-free inpatients with bipolar depression underwent a night of total sleep deprivation. 5-HTTLPR was genotyped in these patients. Changes in perceived mood were rated on a visual analogue scale and analyzed by using repeated measures analysis of covariance. Results: Patients who were homozygotic for the long variant of 5-HTTLPR showed a significantly better mood amelioration after total sleep deprivation than those who were heterozygotic and homozygotic for the short variant. Conclusions: The influence of 5-HTTLPR on response to total sleep deprivation is similar to its observed influence on response to serotonergic drug treatments. This finding supports the hypothesis of a major role for serotonin in the mechanism of action of total sleep deprivation in depression.

L’acidurie 3-méthylglutaconique de type 1 (AMG1) est une pathologie neurométabolique responsable de tableaux neurodeveloppementaux ou de leucodystrophies de l’adulte de sévérité variable. Son spectre clinique reste cependant à définir.

To identify the genetic cause of autosomal dominant spinocerebellar ataxia type 28 (SCA28) with ptosis in 2 Belgian families without AFG3L2point mutations and further extend the clinical spectrum of SCA28 through the study of a brain autopsy, advanced MRI, and cell-based functional assays exploring the underlying disease mechanism.

Generation of neuronal types at the right time, location, and number is essential for building a functional nervous system. Significant progress has been reached in understanding the mechanisms that govern neuronal diversity. Cerebrospinal fluid-contacting neurons (CSF-cNs), an intriguing spinal cord central canal population, are produced during advanced developmental stages, simultaneous with glial and ependymal cells. It is unknown how CSF-cNs are specified after the neurogenesis-to-gliogenesis switch. Here, we identify delayed Ascl1 expression in mouse spinal progenitors during the gliogenic phase as key in CSF-cN differentiation. With fate mappings and time-controlled deletions, we demonstrate that CSF-cNs derive from Ascl1-expressing cells and that Ascl1 triggers late neurogenesis in the amniote spinal cord. Ascl1 abrogation transforms prospective CSF-cN progenitors into ependymocytes. These results demonstrate that late spinal progenitors have the potential to produce neurons and that Ascl1 initiates CSF-cN differentiation, controlling the precise neuronal and nonneuronal composition of the spinal central canal.