Generation of human midbrain organoids from induced pluripotent stem cells

The development of brain organoids represents a major technological advance in the stem cell field, a novel bridge between traditional 2D cultures and in vivo animal models. In particular, the development of midbrain organoids containing functional dopaminergic neurons producing neuromelanin granules, a by-product of dopamine synthesis, represents a potential new model for Parkinson’s disease. To generate human midbrain organoids, we introduce specific inductive cues, at defined timepoints, during the 3D culture process to drive the stem cells towards a midbrain fate. In this method paper, we describe a standardized protocol to generate human midbrain organoids (hMOs) from induced pluripotent stem cells (iPSCs). This protocol was developed to demonstrate how human iPSCs can be successfully differentiated into numerous, high quality midbrain organoids in one batch. We also describe adaptations for cryosectioning of fixed organoids for subsequent histological analysis.

Development and validation of a sensitive HPLC-HESI-MS/MS method for quantitative determination of bitopertin in rat and marmoset plasma

Bitopertin is a potent glycine transporter 1 (GlyT1) inhibitor that has undergone clinical trials for diverse disorders and has a well-documented pharmacokinetic (PK) profile in humans. Even though pre-clinical studies have demonstrated potential therapeutic effects on cognition and neuropathic pain, the PK profile of bitopertin in the rat has been partly disclosed and no study reporting its PK profile in the common marmoset has been published. The aim of this study was to develop and validate a sensitive and selective high-performance liquid chromatography coupled with heat assisted electrospray ionisation tandem mass spectrometry (HPLC-HESI-MS/MS) assay to quantify bitopertin in the rat (Sprague-Dawley) and the common marmoset (Callithrix jacchus) plasma after administration of 1.0 mg/kg subcutaneously. The analytical method consisted of protein precipitation followed by HPLC-HESI–MS/MS. Chromatographic separation was carried out on a Thermo Scientific Aquasil C18 analytical column (100 x 2.1 mm I.D., 5.0 μm) kept at 50°C using acetonitrile and water both fortified at 0.1% (v/v) with formic acid at a ratio 55:45 as mobile phase with a constant flow rate of 250 μL/min. The calibration function was linear in the range of 0.3-200.0 ng/mL in rat plasma. The intra-day and inter-day precision and accuracy were within ± 15% at all concentrations. The limit of detection (LOD) and quantitation (LOQ) in rat plasma were 0.08 and 0.3 ng/mL, respectively. This method has demonstrated high sensitivity and specificity and was successfully applied to measure bitopertin in rat and marmoset plasma, allowing the investigation of its PK properties in both species.

Effectiveness of a personalized health profile on specificity of self-management goals among people living with HIV in Canada: a protocol for a blinded pragmatic randomized controlled trial

Background: Goal setting is a crucial element in self-management of chronic diseases. Personalized outcome feedback is needed for goal setting, a requirement for behavior change. This study contributes to the understanding of the specificity of patient-formulated self-management goals by testing the effectiveness of a personalized health outcome profile. Objective: To estimate among people living with HIV, to what extent providing feedback on their health outcomes, compared to no feedback, will affect number and specificity of patient-formulated self-management goals. Methods: A personalized health outcome profile has been produced for individuals enrolled in a Canadian HIV Brain Health Now cohort study at cohort entry and at the last recorded visit. Participants will be randomized to receive or not “My Personal Brain Health Dashboard” prior to a goal setting exercise. Self-defined goals in free text will be collected through an online platform. Intervention and control groups will receive instructions on goal setting and tips to improve brain health. A total of 420 participants are needed to detect a rate ratio (number of specific words/numbers of person-goals, intervention:control) of 1.5. Text mining techniques will be used to quantify goal specificity based on word matches with a goal-setting lexicon. The expectation is that the intervention group will set more goals and have more words matching the developed lexical than the control group. The total number of words per person-goals will be calculated for each group and Poisson regression will be used to estimate the rate ratio and 95% confidence intervals and compare rate ratios between men and women using an interaction term. Conclusions: This study will contribute to growing evidence for the value of person-reported health outcomes in tailoring interventions, and will provide a thorough understanding of the quality of person-defined goals using text mining. Trial registration: Clinical Trials NCT04175795, registered on 25th November 2019.

The neuro-toxin MPTP does not prevent reproduction in marmosets

1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a neuro-toxin that has been employed to model Parkinson’s disease in non-human primates for over 3 decades. Despite its use for such a long period, little is known about the effects of MPTP on reproductive function. Here, we report the case of a male marmoset which was able to procreate 1.5 year after having been administered the toxin. We also report on 1 male and 1 female MPTP-lesioned marmosets which produced babies after being housed together for 5 years. These cases suggest that MPTP may not interfere with marmoset reproductive function or that if it does, it may be for a limited period of time.

The neuro-toxin MPTP does not prevent reproduction in marmosets

1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a neuro-toxin that has been employed to model Parkinson’s disease in non-human primates for over 3 decades. Despite its use for such a long period, little is known about the effects of MPTP on reproductive function. Here, we report the case of a male marmoset which was able to procreate 1.5 year after having been administered the toxin. We also report on 1 male and 1 female MPTP-lesioned marmosets which produced babies after being housed together for 5 years. These cases suggests that MPTP may not interfere with marmoset reproductive function or that if it does, it may be for a limited period of time.

Generation of human midbrain organoids from induced pluripotent stem cells

The development of brain organoids represents a major technological advance in the stem cell field, a novel bridge between traditional 2D cultures and in vivo animal models. In particular, the development of midbrain organoids containing functional dopaminergic neurons producing neuromelanin granules, a by-product of dopamine synthesis, represents a potential new model for Parkinson’s disease. To generate human midbrain organoids, we introduce specific inductive cues, at defined timepoints, during the 3D culture process to drive the stem cells towards a midbrain fate. In this method paper, we describe a standardized protocol to generate human midbrain organoids (hMOs) from induced pluripotent stem cells (iPSCs). This protocol was developed to demonstrate how human iPSCs can be successfully differentiated into numerous, high quality midbrain organoids in one batch. We also describe adaptations for cryosectioning of fixed organoids for subsequent histological analysis.

Functional specialization in the middle temporal area for smooth pursuit initiation

Smooth pursuit eye movements have frequently been used to model sensorimotor transformations in the brain. In particular, the initiation phase of pursuit can be understood as a transformation of a sensory estimate of target velocity into an eye rotation. Despite careful laboratory controls on the stimulus conditions, pursuit eye movements are frequently observed to exhibit considerable trial-to-trial variability. In theory, this variability can be caused by the variability in sensory representation of target motion, or by the variability in the transformation of sensory information to motor commands. Previous work has shown that neural variability in the middle temporal (MT) area is likely propagated to the oculomotor command, and there is evidence to suggest that the magnitude of this variability is sufficient to account for the variability of pursuit initiation. This line of reasoning presumes that the MT population is homogeneous with respect to its contribution to pursuit initiation. At the same time, there is evidence that pursuit initiation is strongly linked to a subpopulation of MT neurons (those with strong surround suppression) that collectively generate less motor variability. To distinguish between these possibilities, we have combined human psychophysics, monkey electrophysiology, and computational modeling to examine how the pursuit system reads out the MT population during pursuit initiation. We find that the psychophysical data are best accounted for by a model that gives stronger weight to surround-suppressed MT neurons, suggesting that variability in the initiation of pursuit could arise from multiple sources along the sensorimotor transformation.

MIST: A multi-resolution parcellation of functional brain networks

The functional architecture of the brain is organized across multiple levels of spatial resolutions, from distributed networks to the localized areas they are made of. A brain parcellation that defines functional nodes at multiple resolutions is required to investigate the functional connectome across these scales. Here we present the Multiresolution Intrinsic Segmentation Template (MIST), a multi-resolution group level parcellation of the cortical, subcortical and cerebellar gray matter. The individual MIST parcellations match other published group parcellations in internal homogeneity and reproducibility and perform very well in real-world application benchmarks. In addition, the MIST parcellations are fully annotated and provide a hierarchical decomposition of functional brain networks across nine resolutions (7 to 444 functional parcels). We hope that the MIST parcellation will accelerate research in brain connectivity across resolutions. Because visualizing multiresolution parcellations is challenging, we provide an interactive web interface to explore the MIST. The MIST is also available through the popular nilearn toolbox.

From data sharing to data publishing

Data sharing, i.e. depositing data in research community accessible repositories, is not becoming as rapidly widespread across the life science research community as hoped or expected. I consider the sociological and cultural context of research and lay out why the community should instead move to data publishing with a focus on neuroscience data, and outline practical steps that can be taken to realize this goal.

Functional specialization in the middle temporal area for smooth pursuit initiation

Smooth pursuit eye movements have frequently been used to model sensorimotor transformations in the brain. In particular, the initiation phase of pursuit can be understood as a transformation of a sensory estimate of target velocity into an eye rotation. Despite careful laboratory controls on the stimulus conditions, pursuit eye movements are frequently observed to exhibit considerable trial-to-trial variability. In theory, this variability can be caused by the variability in sensory representation of target motion, or by the variability in the transformation of sensory information to motor commands. Previous work has shown that neural variability in the middle temporal (MT) area is likely propagated to the oculomotor command, and there is evidence to suggest that the magnitude of this variability is sufficient to account for the variability of pursuit initiation. This line of reasoning presumes that the MT population is homogeneous with respect to its contribution to pursuit initiation. At the same time, there is evidence that pursuit initiation is strongly linked to a subpopulation of MT neurons (those with strong surround suppression) that collectively generate less motor variability. To distinguish between these possibilities, we have combined human psychophysics, monkey electrophysiology, and computational modeling to examine how the pursuit system reads out the MT population during pursuit initiation. We find that the psychophysical data are best accounted for by a model that gives stronger weight to surround-suppressed MT neurons, suggesting that variability in the initiation of pursuit could arise from multiple sources along the sensorimotor transformation.