We Study the Biology Underlying Cortical Inhibitory Neuron Development and Maturation:

Our lab seeks to uncover how cortical inhibitory neurons are generated, migrate, develop and mature. From the initial programming by transcription factors in progenitor zones until their final destinations in the brain, cortical inhibitory neurons undergo multiple developmental milestones. To this end, we employ a multitude of molecular tools and genetic mouse models to decipher how these complicated processes occur. Our projects range from understanding how key developmental genes normally operate to uncovering the mechanisms that underlie gene dysfunction in Autism Spectrum Disorder (ASD).

Role of Cortical Inhibitory Neurons in Syndromes with High Rates of Autism Spectrum Disorder (ASD):

We want to understand how variants in the genes that cause Neurofibromatosis 1, PTENopathies, Tuberous Sclerosis Complex (TSC) and Desanto-Shinawi Syndrome (DESSH), lead to symptoms in each disorder. While each disorder is distinct, they all have increased rates of ASD and other neuropsychiatric changes. Our lab is investigating how the genes that cause these disorders function in inhibitory neurons and how their disruption alters the development and maturation of these cells. In addition, we are interested in how these genes may work together to control normal brain development and function.

The gene, PTEN, is necessary early in development to establish the correct numbers of specific groups of inhibitory cortical interneurons (Vogt et al., 2015). We observed a reduction in cortical interneurons and aberrant axonal growth of the parvalbumin (PV)+ group when PTEN was deleted from cortical interneuron progenitors (see images below). Notably, the dysfunction of PV+ cortical interneurons has been observed in other ASD animal models, suggesting that this cell type may be important for some symptoms of ASD. We also developed an efficient in vivo screening assay to determine the functional impact of human genetic variants in vivo. This approach is now being used to understand the impact of variants in other genes.  

Fig. 1 P30 NCre cKOs.png
 
Fig. 3 Complementation assay.png

Screening Human Variants Discovered in ASD-Risk Genes:

Our lab utilizes an efficient in vivo screening assay to determine how human variants impact the function of high-risk disease genes in vivo. To this end, we combine lentiviral transduction with genetically-engineered mice to eliminate a given gene in mouse cells and replace it with a normal or variant version of the human gene (Complementation Assay). This allows us to quickly screen the effect of the variant during development and since the modified cells are transplanted back into a mouse, they develop in vivo. 

Currently, we are using the Complementation Assay to uncover how variants in TSC1&2 impact inhibitory interneuron development. In addition, these genes are being conditionally deleted from cortical interneurons in mice to determine their role during development. As we continue to uncover their roles in neuronal cells it may lead to novel insights into the basic development of these cells, disease mechanisms and potential therapeutic options.

 

Fig. 2. P30 Ncre CINs.png

Role of NF1 in Cortical Interneuron Development:

Our initial experiments suggest that loss of NF1 in progenitor cells from the median ganglionic eminence (MGE) results in an increase in total cells from this lineage and a decrease in PV+ interneurons (images to the right). Our lab is currently trying to understand the mechanisms behind these phenotypes. We hope these studies will help elucidate how mutations in NF1 lead to the elevated rates of ASD and alterations in cognitive function associated with the disorder.

 

 

 

SFig. 3. SST PV coloc Nkx2.jpg

Role of TSC Genes in Cortical Interneuron Development:

The genes underlying Tuberous Sclerosis Complex (TSC), TSC1&2, are also inhibitors of the mTOR signaling pathway. Our recent data showed that loss of TSC1 led to an increase of properties associated with parvalbumin+/fast-spiking interneurons, in cells that did not normally have these properties (Malik et al., 2019, figure to the right). We hope to use this knowledge to not only understand how symptoms of TSC arise, but also basic mechanisms of interneuron development and maturation, especially how the parvalbumin+ interneurons assume their mature properties.


Understanding DESSH and potential function of the gene, WAC:

Desanto-Shinawi Syndrome (DESSH) is caused by mutations in the WW domain containing adaptor with Coiled Coil gene, WAC. Shown below, WAC protein is often found in the nucleus of many cell types, suggesting it could be a powerful regulator of gene regulation, although other roles may exist in different parts of the cell. To date, we have generated a mouse lacking one copy of the gene and it recapitulates many symptoms observed in those diagnosed with DESSH (link to manuscript). To determine what brain cell types could be responsible, we have also begun to delete the WAC gene in distinct neuron classes to determine mechanisms relevant to brain development and DESSH. These models will help further understanding of DESSH symptoms as well as test pharmacological agents to establish whether symptoms can be alleviated and/or prevented.