Biology subjects

Luikart, B. W.

Publications and source records attributed to Luikart, B. W..

6 recordsLinked to original sources

bioRxiv2026

Scaling of Neuronal Growth and Excitability Through Separable mTORC1 and mTORC2 Pathways

As neurons grow, they must regulate intrinsic excitability to maintain an appropriate level of spiking based on synaptic inputs. Using gene knockouts, phosphoproteomics, and electrophysiology we show PTEN regulates neuronal growth and intrinsic excitability through separable downstream mechanisms. Pten loss induces cellular hypertrophy, increased excitatory synaptic input, reduced fast afterhyperpolarization, and burst firing. Deleting the mTORC1 scaffold, Raptor, rescues overgrowth and synaptic input but fails to normalize firing, while deleting Akt or the mTORC2 scaffold, Rictor, restores firing without rescuing growth. This dissociation identifies an AKT-mTORC2 mechanism that regulates voltage-gated calcium and BK potassium channels to set spike repolarization and burst firing. In vivo, Pten knockout produces altered network synchrony, lethal seizures, and impaired object and location behavior; Raptor co-deletion display non-lethal hyperexcitability with improved object-location coupling. The biological and pathophysiological significance of these mechanisms is demonstrated by overlap of the PTEN-regulated phosphoproteome with ASD and epilepsy.

neuroscience↗

bioRxiv2026

PTEN Subcellular Localization Dictates Function

Mutations in phosphatase and tensin homolog (PTEN) drive unregulated activation of the phosphatidylinositol-3-kinase (PI3K) pathway, resulting in neuronal hypertrophy, and are strongly associated with autism spectrum disorder (ASD). Several PTEN mutations alter subcellular localization, yet how localization governs PTEN function in developing neurons remains unclear. Although PTEN has been reported broadly distributed throughout neurons, here, live imaging of HaloTagged PTEN reveals dynamically regulated localization, suggesting spatial control of its signaling. We then used retroviral-mediated genetic manipulation to delete endogenous Pten in developing hippocampal neurons while simultaneously expressing PTEN fused to defined localization motifs, allowing us to directly test how subcellular targeting regulates neuronal morphology. Loss of Pten produces neurons characterized by enlarged somata, more elaborate dendritic arbors, and increased spine density, length, and head area. Nuclear-excluded PTEN fully rescued these phenotypes, whereas targeting PTEN to filopodia via fusion to the FBAR domain of srGAP3 or to the postsynaptic density via Homer1C corrected or corrected all morphological abnormalities in PTEN-deficient neurons and simplified dendritic arborization compared to wild-type. In contrast, nuclear-localized PTEN produced only partial rescue, normalizing soma size and spine head area but not dendritic complexity or spine density. These findings indicate that PTEN acts locally to restrain growth and structural connectivity, whereas regulation of spine head size can be mediated by PTEN both inside and outside the nucleus, potentially through transcriptional or splicing-dependent mechanisms. Together, our results identify subcellular localization as a critical determinant of PTEN function and reveal spatially distinct mechanisms through which PTEN sculpts neuronal development.

neuroscience↗

bioRxiv2023

Single-cell analysis of the nervous system at small and large scales with instant partitions

Single-cell RNA sequencing is a new frontier across all biology, particularly in neuroscience. While powerful for answering numerous neuroscience questions, limitations in sample input size, and initial capital outlay can exclude some researchers from its application. Here, we tested a recently introduced method for scRNAseq across diverse scales and neuroscience experiments. We benchmarked against a major current scRNAseq technology and found that PIPseq performed similarly, in line with earlier benchmarking data. Across dozens of samples, PIPseq recovered many brain cell types at small and large scales (1,000-100,000 cells/sample) and was able to detect differentially expressed genes in an inflammation paradigm. Similarly, PIPseq could detect expected and new differentially expressed genes in a brain single cell suspension from a knockout mouse model; it could also detect rare, virally-la-belled cells following lentiviral targeting and gene knockdown. Finally, we used PIPseq to investigate gene expression in a nontraditional model species, the little skate (Leucoraja erinacea). In total, PIPSeq was able to detect single-cell gene expression changes across models and species, with an added benefit of large scale capture and sequencing of each sample.

neuroscience↗

bioRxiv2023

Dual impact of PTEN mutation on CSF dynamics and cortical networks via the dysregulation of neural precursors and their interneuron descendants

Expansion of the cerebrospinal fluid (CSF)-filled cerebral ventricles (ventriculomegaly) is the quintessential feature of congenital hydrocephalus (CH) but also seen in autism spectrum disorder (ASD) and several neuropsychiatric diseases. PTEN is frequently mutated in ASD; here, we show PTEN is a bona fide risk gene for the development of ventriculomegaly, including neurosurgically-treated CH. Pten-mutant hydrocephalus is associated with aqueductal stenosis due to the hyperproliferation of periventricular Nkx2.1+ neural precursors (NPCs) and CSF hypersecretion from inflammation-dependent choroid plexus hyperplasia. The hydrocephalic Pten-mutant cortex exhibits ASD-like network dysfunction due to impaired activity of Nkx2.1+ NPC-derived inhibitory interneurons. Raptor deletion or post-natal Everolimus corrects ventriculomegaly, rescues cortical deficits, and increases survival by antagonizing mTORC1-dependent Nkx2.1+ cell pathology. These results implicate a dual impact of PTEN mutation on CSF dynamics and cortical networks via the dysregulation of NPCs and their interneuron descendants. These data identify a non-surgical treatment target for hydrocephalus and have implications for other developmental brain disorders. HIGHLIGHTSO_LIPTEN de novo mutations are associated with cerebral ventriculomegaly in autism spectrum disorder (ASD) and congenital hydrocephalus (CH). C_LIO_LIPten-mutant hydrocephalus is associated with aqueductal stenosis due to the hyperproliferation of medial ganglionic eminence Nkx2.1+ neural precursors and CSF hypersecretion from inflammation-induced choroid plexus hyperplasia. C_LIO_LIThe hydrocephalic Pten-mutant cortex exhibits ASD-like network dysfunction due to impaired activity of Nkx2.1+ NPC-derived inhibitory interneurons. C_LIO_LImTORC1 inhibition via Raptor deletion or early post-natal treatment with rapamycin or everolimus increases survival and ameliorates Pten-mutant ventriculomegaly and cortical pathology. C_LI

neuroscience↗

bioRxiv2023

TCF4 mutations disrupt synaptic function through dysregulation of RIMBP2 in patient-derived cortical neurons

Genetic variation in the transcription factor 4 (TCF4) gene is associated with risk for a variety of developmental and psychiatric conditions, which includes a syndromic form of ASD called Pitt Hopkins Syndrome (PTHS). TCF4 encodes an activity-dependent transcription factor that is highly expressed during cortical development and in animal models is shown to regulate various aspects of neuronal development and function. However, our understanding of how disease-causing mutations in TCF4 confer pathophysiology in a human context is lacking. Here we show that cortical neurons derived from patients with TCF4 mutations have deficits in spontaneous synaptic transmission, network excitability and homeostatic plasticity. Transcriptomic analysis indicates these phenotypes result from altered expression of genes involved in presynaptic neurotransmission and identifies the presynaptic binding protein, RIMBP2 as the most differentially expressed gene in PTHS neurons. Remarkably, TCF4-dependent deficits in spontaneous synaptic transmission and network excitability were rescued by increasing RIMBP2 expression in presynaptic neurons. Together, these results identify TCF4 as a critical transcriptional regulator of human synaptic development and plasticity and specifically identifies dysregulation of presynaptic function as an early pathophysiology in PTHS.

neuroscience↗

bioRxiv2022

Single-cell RNA sequencing of conditional Pten knockout neurons in mice

PTEN is a well-known tumor suppressor whose mutations are also strongly associated with Autism Spectrum Disorder (ASD). The activity and function of PTEN in neurons have been studied extensively in various settings, whereas animal models offer the best opportunity to experimentally modify and test the role of PTEN in neuronal development in vivo. On the molecular level, PTENs importance in the mTOR pathways suppression is well-known but many other interactions have been suggested and yet others likely remain undiscovered. Therefore, to systematically explore the regulatory landscape downstream of PTEN on the genetic level, we have set out to establish a singlecell RNA sequencing (scRNA-seq) workflow to measure gene expression changes as a result of knocking out the Pten gene in vivo. We were able to collect brain tissue from four conditionally knocked out mouse samples and dissociate them into single live cells, which were subsequently flow-sorted and a scRNA-seq library was prepared. All of these steps were completed in a single day, yielding sequencing data from hundreds of cells suitable for cell clustering, cell type identification, and differential expression measurements. Having demonstrated its feasibility, this approach promises to aid hypothesis generation and discovery in mapping the function of Pten as well other genes whose regulatory networks remain to be fully defined.

neuroscience↗