Model Systems Core Services

Sets of human IDD cellular models are derived for each project by reprogramming patient-derived biomaterials to generate induced PSC lines, and by genome engineering of both WT and IDD subject-derived PSCs. The CTC works with investigators to recruit subjects and obtain deidentified biomaterials, which are provided to the CMU for this purpose. Reprogramming and genome engineering is either performed by the CMU or through collaboration with the Genome Engineering and induced Pluripotency Center @WUSTL. The CMU also derives molecular tools to manipulate the activity of IDD genes, which are used in combination with these PSC models.

PSC models are differentiated into a range of IDD-relevant neuronal and organoid types and used to perform cellular and molecular phenotyping, including assessment of:

• cellular physiology, including altered proliferative and apoptotic indices, ER or oxidative stress, and/or cellular metabolism.
• neural progenitor specification, maintenance, and progenitor cell type identity.
• neuronal differentiation, organoid patterning, neuronal cell type identity, and maturation.
• neuronal morphology, neurite extension, synaptogenesis, and migration.
• neuronal function, assessed using electrophysiology and/or multi-electrode array, in pure neuronal populations, organoids, or co-cultures, is performed in collaboration with Dr. Huettner in the NPhyS.
• Genome-wide transcriptomic and/or epigenomic analyses are used to define molecular mechanisms, pathways, and processes altered in IDD models, including acute effects and direct targets. RNA or chromatin sample preparation is performed by the CMU, with sample sequencing performed through the Genome Technology Access Center @WUSTL.
• Targeted or high-throughput screening and other applications.

The workflow above defines cell autonomous, intermediate phenotypes linked to patient affectation.  These cells are useful for small molecule and chemical screening to identify suppressors, and to identify leads for developing interventions for IDD. The CMU performs some of this screening in collaboration with the High-Throughput Screening Core @WUSTL. These models can also be used for many other applications, such as high throughput annotation of variant pathogenicity by complementation assay, to compare phenotypes resulting from many variants of uncertain pathogenicity in an IDD gene.

The directors of the CMUs at WUSTL and University of Wisconsin, Drs. Kroll and Anita Bhattacharyya, co-lead the Cross-IDDRC Cellular Models Group. This group engages CMUs at all 14 US IDDRCs in collaborative projects, some of which focus on cross-IDDRC calibration, benchmarking, and standardization of methods for IDD cellular phenotyping, to ensure reproducibility and enable data meta-analysis across the network. The Cellular Models Group is also building both a biorepository and a data repository for IDD cellular models under study at all 14 IDDRCs. These repositories will enable access to IDD models generated by CMUs throughout the network, and will link these models with accompanying genomic, transcriptomic, and epigenomic data. Banking of these IDD models and data will utilize cross-IDDRC calibrated methods, making these repositories valuable for data meta-analyses and model resource sharing by all 14 IDDRCs. Such meta-analyses can be informative in defining convergent mechanisms that contribute to IDDs involving many different genetic contributors to patient risk.

The ABS offers over 45 individual behavioral tests within the following categories: 1) learning and memory (spatial and nonspatial); 2) motor/sensorimotor functions; 3) alterations in emotionality/motivation; 4) social interactions and behaviors; 5) sensory behavioral functions; 6) depression-like behaviors; and 7) ASD-like behaviors.

The ABS has acquired a wide range of instrumentation to better characterize phenotypes and treatment effects including:

• DigiGait and CatWalk gait analysis systems that use digital footprint videograhic techniques to quantify a large range of relevant metrics. The ABS has recently used the DigiGait in concert with a force-plate actometer/open-field system to provide a full characterization of the disturbances in locomotion and movement patterns in developmental mouse models of cerebellar dysfunction.
• 10 operant chambers for developing a social reinforcement task
• Upgrades for acoustic startle/prepulse inhibition (PPI) to enhance ABS abilities to evaluate the role of sensory loss in cognitive development; and 
• Upgraded conditioned fear test systems to better detect differences in Pavlovian fear conditioning capabilities.

1. Social Operant test: A lack of social motivation has been hypothesized to occur in ASD. Dr. Maloney and members of the Dougherty lab have greatly refined a social operant test in mice³ by quantifying nose pokes that lead to visual access to either a conspecific or just an opening door. Data demonstrate that WT control mice are motivated by the social stimulus to increase nose-pokes over time. Comparing data generated from this test with results from standard operant reward tasks, provides evidence of whether observed deficits in reward are global or specific to social-based behaviors.
2. Observational Fear Learning (OFL) test: Drs. Wozniak, Maloney and Arvin Palanisamy (Peds/Anesthesia) further developed the OFL to assess empathy-like fear responses (freezing) in a rodent observing a conspecific in distress (brief exposure to foot shocks) and whether the observer rodent shows evidence of contextual fear conditioning 24 h after a training trial.
3. Combining behavioral testing with auditory processing analyses to study the effects of early sensory disturbances on cognitive development.
4. Reproductive behavior assessments (breeding success, sexual motivation, and sexual performance) which, when combined with other in-house tests, will be used to evaluate mice with high-grade gliomas treated with epigenetic interventions (in collaboration with Drs. Joshua Rubin and Maloney). We have also improved or standardized: 1) a three-chambered social approach test for rats; 2) the sensorimotor battery for juvenile rats; 3) rotarod testing for juvenile rats; 4) DigiGait for testing juvenile rats; 5) acoustic startle/ppi for juvenile rats.

The ABS is engaged in the ongoing need for assessments of social communication involving ultrasonic vocalization (USV), scent marking, sex-dependent olfactory preference, and the Barnes maze. We are prioritizing acquisition of USV-related equipment to offer the basic maternal isolation-induced USV technique that will allow us to extend its use in olfactory preference testing to monitor responses of males to in estrus female urine and female responses to male urine versus neutral odors. The ABU is purchasing new balance beam equipment and a new virtual optomotor instrumentation system for evaluating visual thresholds in larger rats.        

Basic histopathology approaches for light microscopic evaluation include perfusion fixation, embedding, sectioning and staining of CNS tissues.  The NPS also provides investigator training in these methods and in research design, data analysis and interpretation. Additional procedures offered include DeOlmos cupric silver staining, in situ hybridization, and western blotting.

The NPS has experience with a wide variety of immunohistochemical methods including: activated caspase-3, pERK, TUNEL, NeuN, GFAP, MBP, Ki-67, PCNA, Nestin, BrdU, NR1, GAD, calbindin, ChAT.  The NPS  will develop additional approaches as need arises. Previous work included the development of new methods to assess the developmental neuropathology produced by Zika virus infection, anesthetic drugs, and glucocorticoids. 

The NPS also conducts and/or assists investigators in quantitative tissue analyses using unbiased stereology and unbiased sampling of the brain or brain regions of interest. The NPS is equipped with digital imaging microscopes with electronically driven stages and Microbrightfield software specifically designed to facilitate unbiased stereological quantitative analysis. The NPS also provides ultrastructural analysis of pathological changes in the developing brain. Both Drs. Noguchi and Farber have many years of experience in using the electron microscope to investigate a variety of neuropathological phenomena including viral infection, excitoxicity, and apoptosis.

EEG: Numerous studies have documented the co-existence of seizures with disorders of IDD. In order to evaluate these and other paroxysmal behaviors, the NPhyS established and offers a rodent epilepsy monitoring unit with the capacity to monitor 36 mice using continuous video-EEG monitoring.  Using this technique, the NPhyS has characterized seizures in multiple models of IDD, such as in mouse models of tuberous sclerosis complex, neuronal ceroid lipofuscinosis, and other genetic IDDs.  The NPhyS also developed and offers technically innovative methods to allow serial video-EEG monitoring longitudinally in preweaning neonatal mice. In addition, NPhys performs both qualitative and quantitative (e.g., spike counts, spectral analysis) assessments of abnormalities in interictal background EEG activity, which provide a neurophysiological correlate of encephalopathy;

Seizure threshold testing: This is performed using convulsant drugs, such as pentylenetetrazol or kainate in rodents that do not have spontaneous seizures;

Polysomnograms: Sleep disorders are common in IDD and can exacerbate its symptoms. Using a combination of EEG and EMG, the NPhyS performs sleep studies that characterize the sleep-wake cycle, including the percentage of times in awake, non-REM, and REM states and power spectra analysis. The NPhyS has recently used these methods to identify sleep abnormalities in a mouse model of neurofibromatosis, tuberous sclerosis, and aging.

Somatosensory evoked potentials: Sensory abnormalities are also characteristic of some neurodevelopmental disorders. The NPhyS offers newly developed methods for stimulating median nerve in rodent forepaw and stably recording evoked potentials over somatosensory cortex with epidural electrodes;

Slice and Cellular Electrophysiology: Extracellular field potential recordings and single cell/intracellular recordings are powerful methods for assessing synaptic function and plasticity in neuronal networks and investigating the cellular basis and mechanisms of learning deficits and other brain dysfunction in IDDs.  The NPhyS offers consultation, training, and equipment use to investigators in several fully-equipped electrophysiology rigs available in the MSC for extracellular field potential recording in brain slices and whole-cell patch-clamp recording in slices and cultured cells.

Human PSCs:  Inasmuch as neurons derived from human PSCs are difficult to work with and characterize, Dr. Huettner, a noted expert in this field, works with Dr. Kroll of the Cellular Models Unit to assess IDD patient-derived pure neuronal populations, organoids, or co-cultures using electrophysiology and/or multi-electrode array.