Down syndrome (DS) is caused by trisomy of chromosome 21 and characterized by cognitive impairment. Cognitive impairment is associated with impaired neurodevelopment. Imbalances in neurogenic signaling during the critical periods of prenatal and postnatal neurogenesis are likely to affect neurodevelopment, resulting in microcephaly and impaired cognitive function. Gaseous neurotransmitters such as hydrogen sulfide (H2S), carbon monoxide or nitric oxide contribute to neurogenic signaling. One of the genes responsible for the synthesis of H2S (cystathione betasynthase, CBS), is present in chromosome 21. While CBS is overexpressed in DS, the contribution of H2S overproduction for the neural phenotype observed in DS is unknown. We hypothesize that neurogenic signaling can be affected by H2S in at least two ways: a) direct post-translational modification of proteins in cysteine residues, or S-sulfhydration, a mechanism that changes signal transduction during neurodevelopment; b) inhibition of mitochondrial respiration and blocking the developmental switch from glycolysis to oxidative phosphorylation that is necessary for correct neurodevelopment. We have established several induced pluripotent stem cells (iPS) lines obtained from DS individuals, which present higher H2S levels than iPS obtained from healthy individuals. To study the contribution of H2S to the alterations in neurodevelopment in DS, we propose a pilot project with 2 main aims: 1)characterize H2S impact on cellular bioenergetics in iPS human cellular models during neuronal differentiation in neuronal cultures and cerebral organoids 2)identify the S-sulfhydration targets altered in DS during the critical period of neurodevelopment by thiol redox proteomics Investigating the role of H2S during neuronal development may help in devising new strategies to ameliorate/rescue neurodevelopment and the consequent cognitive impairment in DS patients, to improve daily autonomy and inclusion throughout life.

The ability to successfully retrieve memories from our past directly influences how we learn about and interact with the world around us. Therefore, it is critical to understand factors that support rich and successful memory in all individuals. While a lot is known about memory impairments in Down syndrome (DS; Jarrold & Nadel, 2009; Godfrey & Lee, 2018), interventions that may mitigate these memory deficits are not well understood. One potentially modifiable factor that has been shown to enhance memory is sleep (e.g., Diekelmann & Born, 2010; Stickgold, 2005), but several studies have shown that these enhancements do not extend to individuals with DS (Luongo et al., 2021). The current study examines two potential explanations for this disruption: a) that DS is associated with global disruptions to the memory-enhancing mechanisms supported by sleep, and b) that DS is associated with changes in how these mechanisms work, where they are enhanced relative to neurotypical controls for some memories, but weaker for others. In addition to enhancing overall memory, sleep may be particularly well-suited to support emotional memory (e.g., Payne et al., 2008) and has been shown to simultaneously reduce the emotional tone associated with negative events (Walker and ven der Helm, 2009). Such changes can help individuals retain the important details of highly emotional events, while also improving their ability to regulate their emotions. Recent research from our lab suggests that emotional memory may work similarly in individuals with DS and neurotypical controls over a period of wake, but no research has examined these sleeprelated processes. The current study examines these emotional memory processes by comparing the effects of a night’s sleep on emotional and non-emotional content. The results of these studies will help researchers and educators identify potential memory strategies targeted to individuals with DS.

Down Syndrome patients are often described as temperamentally “easy” and sociable but they also present social behavioral problems that affect their daily activity. Down syndrome patients present alterations in the recognition of the expression of fear and other emotions, which impact their social activities and their relationships with their peers, in schools or with their families. However, the alterations in the brain of Down syndrome patients leading to these behavioral dysfunctions are unknown. We can use a task called affective discrimination task to study these alterations in social behavior in mice. Preliminary data indicate that a mouse model of Down syndrome clearly show a deficit in emotional recognition. Other previous studies suggested a direct link between specific brain alterations (i.e. cannabinoid signaling) and Down Syndrome, which can be relevant to the development of social cognitive dysfunctions in neurodevelopmental brain disorders such as Down Syndrome. However, we are still far to know if these specific brain alterations are the cause of the impairment of emotional recognition observed in our mouse model. Our hypothesis is that cannabinoid signaling is involved in the emotional recognition deficits observed in our mouse model of Down Syndrome. We will use behavioral tasks, pharmacology and imaging techniques to investigate the involvement of these brain mechanisms in emotional recognition impairments found in the Down syndrome mouse models. Overall, this proposal represents a pilot project to obtain a proof of concept of the use of drugs acting on cannabinoid signaling to tackle complex social deficits observed in Down syndrome.

DYRK1A is responsible of the cognitive deficits observed in Down syndrome (DS) and in the Dyrk1a haploinsufficiency syndrome (DHS) associated with microcephaly, epilepsy and autism. Both syndromes also present motor control impairments such as unstable postural control with poor inhibitory control of movement, hyperactivity, increased impulsivity and speech production deficit that are associated with a dysfunction of the striatum, a deep-brain nucleus involved in production of voluntary movement, but have been less studied. Analyzing mouse models in which we have change the number of copies of the gene in newborn neurons that will make the striatum, we observed a major impact of Dyrk1a on striatal neurogenesis with absence of one copy of the gene leading to a decrease in striatal volume and absence of the two copies leading to a complete absence of the striatum that resulted to myoclonic dystonia (movement disorder with brief and rapid muscle contractions) in newborn pups. We want to further shed light on Dyrk1a function in striatal neurogenesis and on the impact of Dyrk1a gene dosage perturbation on striatal formation. We propose to use high throughput technologies to identify at the cell-level the molecular deregulation that are triggered by Dyrk1a gene dosage changes with 0 copy to study the gene biological function, 1 copy to model DHS, 2 copies to have the normal condition and 3 copies to model DS.

Defective availability of FOXG1 gene products underlies a large fraction of cases of FOXG1 syndrome, a rare and severe neuropathological entity, for which no cure is presently available. FOXG1 controls embryonic development of the anterior brain and later regulates the activity of anterior brain nerve cells. For this reason, restoring proper levels of products of its expression – even after birth – might at least mitigate consequences of their deficit. Theoretically, this might be cleanly achieved by repair of the damaged FOXG1 gene copy in the living brain. However even the most advanced tools for molecular medicine available nowadays are unable to achieve this goal. As an alternative, we conceived to restore normal levels of FOXG1 gene products, by gently stimulating the healthy copy of the gene, at different levels of the multi-step process leading from the gene to its ultimate protein product. In this way, nerve cells should be still able to dynamically adapt FOXG1 activity levels to their needs. Meanwhile, undesired collateral effects likely originating from a heavier, unilevel intervention might be mitigated. In accord with this design, we have already selected and validated an artificial small RNA, gently stimulating the synthesis of FOXG1-mRNA, while not jeopardizing its natural regulation, in murine and human cells, in vitro and in vivo. Here, we propose to further select a miniset of modified small RNAs, able to stabilize Foxg1-mRNA and and/or increase the synthesis rate of the corresponding protein. The primary selection of these effectors will be run in cultures originating from cerebral cortex of mouse embryos. Next, the best performing effectors will be validated in living mice, upon subcutaneous and intra-cerebroventricular administration, as well as in nerve cells originating from dedifferentiation and subsequent redifferentiation of human skin cells.

We’re trying to find out why kids with Down Syndrome (DS) often get sick more and have different health problems. These kids sometimes need more medical help, stay longer in the hospital, and are at a higher risk of serious respiratory infections. It seems like their body’s defense system, called the immune system, might not be working quite right. Even adults with DS have different health issues, like less chance of certain cancers but more problems with the brain and the immune system. Our project is like detective work to understand how the immune system in people with DS is connected to them getting sick or having a higher risk of infectious and other diseases. Some studies, including ours, found issues in the blood of people with DS, like too many inflammatory molecules and antibodies that can attack their own body. But we don’t know much about what happens in the body’s first defense against germs, like the tonsils. Tonsils are like the body’s gatekeepers, stopping germs from going further into the body. They have special cells that help fight off infections. In kids with DS, these cells don’t seem to be working the way they should. So, we’re going to study these special immune cells in the tonsils of kids with DS using fancy techniques. By doing this, we hope to understand why the immune system in DS is different and how it might be linked to their health problems. Our big goal is to find new ways to help people with DS stay healthy and have a better life.

Developmental and Epileptic Encephalopathy 9 (DEE9) is a neurodevelopmental disorder characterized by epilepsy, cognitive impairment and different behavioural and psychiatric defects. DEE9 is due to mutations in the PCDH19 gene (Xq22.1), which encodes for protocadherin 19 (PCDH19), a protein highly expressed in the brain that promotes calcium- dependent adhesion between cells. The mechanisms behind the disorder are still unknown. In our laboratory, we observed that in mice the deletion of Pcdh19 in inhibitory parvalbumin expressing cells (PV+) causes an increased general spontaneous electric activity compared to controls, suggesting an increased general excitability. We hypothesize that PV+ neurons are involved in the neurological phenotype associated with DEE9. Our objective is to investigate the consequences of Pcdh19-deficiency in PV+ neurons in prefrontal cortex at functional and transcriptional level in mice, thus opening the possibility to identify new targets and to develop novel specific therapies for patients with DEE9. This study will elucidate the role of PV+ cells in DEE9 and provide a novel key to understand DEE9 and to identifying new therapeutic targets.

People with Down syndrome (DS) can also develop a form of Alzheimer’s disease (AD). AD can affect memory and thinking and is a main cause of health problems and even death. Scientists have gotten better at finding the early signs of AD, but it’s still hard to notice small memory changes in the early stage, especially for people with DS who already face cognitive difficulties. However, when testing new treatments for AD in DS, it’s really important to measure how well they work in this early time. In this study, we want to make a new digital test for people with DS. This test will check how well they remember things when given a few chances to learn. We will use a test where they have to remember pairs of things, like names and faces. With a little help from caregivers, around 90 people with DS will try this test on a phone or tablet every day for a week in their homes. We want to see if this test can find small memory problems that show up when AD is there but not causing big problems yet. We will compare the results of those with AD markers in blood to those without. We think this test could be a good way to tell if memory is changing in the early stages of AD in DS and if it’s connected to the markers we find in the blood in such early stages.

Trisomy of human chromosome 21 (HSA21) causes Down Syndrome (DS) through the surplus activity of genes on HSA21. DS spans heart defects, impaired immunity and intellectual disability. People with DS also show accelerated aging, and often develop Alzheimer’s disease by middle age. However, to-date only triple-copy dosage of the amyloid beta precursor (APP) has been implicated conclusively, as it is sufficient to cause Alzheimer’s. How multiple genes contribute to DS is currently unknown, but represents an essential stepping stone towards identifying which cellular pathways could be targeted for therapeutic intervention. In this application, we propose to apply two completely independent mechanisms to correct the overall “dosage” of genes on HSA21 in T21 cells. We propose to use these systems to understand how different cell types in the brain, namely neurons and their support cells (“astrocytes”) respond to increased cellular stress. One such stress is closely linked to how cells generate energy (OS, “oxidative stress”). OS is especially relevant to neurodegenerative changes in DS, due to the way neurons and astrocytes interact to generate energy in the brain. Because neurons depend on astrocytes for a number of vital metabolic and regulatory functions, we address this question using DS-derived human induced pluripotent stem cells (hiPSCs) that can generate just the relevant cell types in a dish. The objectives of this application are to: 1.) untangle how DS neurons and astrocytes generate and respond to OS, and 2.) which HSA21 are involved. We have two independent approaches to repressing HSA21 genes: the first “silences” all of HSA21, whereas the second only represses specific genes at a time. We introduced these systems into DS hiPSCs that also express a fluorescent reporter gene to light up cells experiencing OS. Our overall long-term goal is to learn how DS neurons and astrocytes interact, and how to target OS in DS.