Biology subjects

Dave, B. M.

Publications and source records attributed to Dave, B. M..

3 recordsLinked to original sources

bioRxiv2026

Convergence on BRAF and MAPK Signaling in Glioma Development in a P53-ENU model

Pediatric high-grade gliomas (HGGs) are aggressive and lethal brain tumors that account for 15- 20% of all pediatric central nervous system (CNS) malignancies and remain largely incurable. These tumors, despite having mutational targets that activate MAPK signaling, are frequently resistant to targeted therapies in their malignant states, but often show responses when they are in lower grade form. These findings suggest a need to identify and intercept early tumorigenic events that arise in earlier tumor developmental stages. To investigate the molecular events in glioma progression, we developed and characterized a NestinCre/+;Trp53fl/fl mouse model combined with in utero exposure to the classic chemical mutagen N-ethyl-N-nitrosourea (ENU). This model mimics the context of genetic predisposition paired with an environmental genotoxic insult, and mice with loss of TRP53 in early neural precursors who are exposed to ENU at embryonic day 13.5 reproducibly develop HGGs postnatally that retain features of the human tumors. By sampling discrete lesions at premalignant, early, and late stages, we observed progressive increases in genetic complexity, stemness features, and immune signatures across tumor evolution. Notably, a recurrent Braf mutation emerged in a majority of early lesions and persisted in advanced tumors, consistent with the occurrence of BRAFV600E mutations in human gliomas that arise in children and undergo transition from lower grade to higher grade stages. Additional components of the RAS-RAF-MAPK signaling cascade, including Kras, Nras and Nf1 were found to be mutated at the late tumor stage, indicating convergent activation of this pathway in this model. Cell lines derived from early lesions responded to BRAF inhibitors, but cells from endpoint tumors were less responsive. Together, this model reveals aspects of the molecular and cellular evolution of glioma development in vivo, and identifies RAS-MAPK signaling as a critical molecular bottleneck selected for the ENU-induced mutations. This genetic-environmental model may be valuable to understanding key determinants of glioma initiation and progression, and for evaluating new therapies that limit MAPK signaling.

cancer biology↗

bioRxiv2023

Directed differentiation of human hindbrain neuroepithelial stem cells recapitulates cerebellar granule neurogenesis

Cerebellar granule neurons (CGNs) are the most abundant neurons in the human brain and modulate cerebellar output to the motor cortex. Dysregulation of CGN development underlies movement disorders and medulloblastomas. It is suspected that these disorders arise in progenitor states of the CGN lineage, for which human models are lacking. Here, we have differentiated human hindbrain neuroepithelial stem (hbNES) cells to CGNs in vitro using soluble growth factors, recapitulating key progenitor states in the lineage. We show that hbNES cells are not lineage committed and retain rhombomere 1 (r1) regional identity. Upon differentiation, hbNES cells first transit through a rhombic lip (RL) progenitor state at day 7, demonstrating human specific sub-ventricular cell identities. This RL state is followed by an ATOH1+ CGN progenitor state at day 14. By the end of a 56-day differentiation procedure, we obtain mature neurons expressing CGN markers GABAAa6 and vGLUT2. These neurons generate spontaneous and evoked action potentials. A small fraction of endpoint neurons were unipolar brush cells (UBC). We noted maintenance of a RL population throughout differentiation, as is consistent with human development. We show that sonic hedgehog (SHH) promotes {gamma}-aminobutyric acid (GABA)-ergic lineage specification and is a positive regulator of CGN progenitor proliferation. Interestingly, we observed that functional neuronal maturation is impaired by either elevated or absent SHH signaling. Impaired maturation under high SHH levels represents the potential of our system to model cerebellar tumorigenesis. Further, our data suggest a potential pro-differentiation role of SHH within a certain concentration range. Our work is, to our knowledge, the first detailed temporal characterization of the complete human CGN lineage in vitro. Our system recapitulates developmentally relevant progenitor states and is a new tool to model this specific cerebellar lineage, and how it may be disrupted to cause human disease.

developmental biology↗

bioRxiv2021

Disruption of the autism-associated gene SCN2A alters synaptic development and neuronal signaling in patient iPSC-glutamatergic neurons

SCN2A is an autism spectrum disorder (ASD) risk gene and encodes a voltage-gated sodium channel. However, the impact of autism-associated SCN2A de novo variants on human neuron development is unknown. We studied SCN2A using isogenic SCN2A-/- induced pluripotent stem cells (iPSCs), and patient-derived iPSCs harboring a p.R607* or a C-terminal p.G1744* de novo truncating variant. We used Neurogenin2 to generate excitatory glutamatergic neurons and found that SCN2A+/p.R607* and SCN2A-/- neurons displayed a reduction in synapse formation and excitatory synaptic activity using multielectrode arrays and electrophysiology. However, the p.G1744* variant, which leads to early-onset seizures in addition to ASD, altered action-potential dynamics but not synaptic activity. Proteomic and functional analysis of SCN2A+/p.R607* neurons revealed defects in neuronal morphology and bioenergetic pathways, which were not present in SCN2A+/p.G1744* neurons. Our study reveals that SCN2A de novo variants can have differential impact on human neuron function and signaling. HIGHTLIGHTS- Isogenic SCN2A-/- neurons display intrinsic hyperexcitability and impaired excitatory synapse function - SCN2A+/p.R607* variant reduces excitatory synapse function in patient neurons - C-terminal SCN2A+/p.G1744* variant enhances action potential properties but not synaptic transmission in patient neurons - SCN2A+/p.R607* variant display impacts on morphological and bioenergetic signaling networks through proteomic and functional analysis eTOC- Brown et al. examined Autism-associated SCN2A variants using patient-derived iPSC NGN2-neurons. They discover that genetic variants differentially impact neuronal development and synaptic function, and highlight neuronal and bioenergetic signaling networks underlying SCN2A loss-of-function.

neuroscience↗