Biology subjects

Tillman, D. E.

Publications and source records attributed to Tillman, D. E..

5 recordsLinked to original sources

bioRxiv2026

An intrinsically disordered adaptor protein controls the size and composition of EGFR condensates on membranes

Receptor phase separation is common in signaling pathways, yet mechanisms that limit condensate size and drive their dissolution remain poorly understood. For example, phosphorylated EGFR forms large micron-scale condensates in vitro, but assembles into smaller nanoscale clusters in cells, suggesting cellular regulation of condensate size. Here, we show that the intrinsically disordered adaptor protein GAB1 actively dissolves EGFR condensates and re-nucleates smaller, compositionally distinct assemblies in reconstituted supported lipid bilayers and simulations. Dissolution requires unphosphorylated tyrosines within the GAB1 intrinsically disordered region, and tyrosine phosphorylation acts as a regulatory switch that abolishes this activity. GAB1-nucleated assemblies require PH domain-driven oligomerization, which is inhibited by phosphoinositide lipids, linking membrane composition to nucleation. These results uncover two unexpected regulatory features in signaling pathways. First, unphosphorylated tyrosines may function broadly to regulate condensate size or stability, since similar tyrosine-based sequence features are found across hundreds of proteins, including many that function in signal transduction. Additionally, PH domains may play a broader role in protein oligomerization and receptor organization, as an AlphaFold screen reveals dozens of additional PH domains predicted to self-associate. Together, these results establish general mechanisms that function as modular tools for reprogramming signaling through receptor reorganization and may enable new approaches to target such pathways in disease.

biophysics↗

bioRxiv2026

Sequestration of growth cone surface proteins by cytoplasmic Lrrtm2 induces de novo amygdala innervation by cerebral cortex associative neurons

Precise establishment of distinct cerebral cortex circuits is essential for sensorimotor function, high-level cognition, and cross-modality integration and association. Although an increasing set of molecular controls over subtype-specific cortical wiring have been identified, much less is known about how molecules in growth cones (GCs) regulate precise long-range projection of axons through complex environments, or how dysregulation of GC molecular machinery disrupts precision of circuit formation. Here, we discover a generalizable mechanism for regulation of precise circuit wiring by focusing on callosal projection neurons (CPN), which link cortical hemispheres via the corpus callosum. CPN are centrally involved in associative and cognitive function, and are often disrupted in people with autism spectrum disorders (ASD) and intellectual disabilities (ID). We identify dysregulated subcellular CPN GC proteomes in vivo after CPN-specific deletion of Bcl11a/Ctip1, a transcription factor (TF) with variants that cause ASD/ID in humans, and validate localization of dysregulated proteins to CPN GCs ex vivo. We identify that disruption of Lrrtm2 - a canonically postsynaptic transmembrane protein - in CPN GCs specifically induces de novo innervation of the amygdala, an evolutionarily ancient regulator of social behavior, cognition, and anxiety that is abnormally activated in humans with ASD. Mechanistically, we identify that deletion of Bcl11a from CPN disrupts targeting of Lrrtm2 to CPN GC membranes, causing cytoplasmic sequestration of key CPN GC surface proteins, and resulting in aberrant innervation of basolateral amygdala (BLA), which is typically targeted by evolutionarily older archicortex. Together, this work connects deletion of a causal ASD/ID TF, dysregulation of a non-canonical control over GC surface protein remodeling, and formation of a de novo, subtype-specific circuit between cerebral cortex and BLA - similar mechanisms likely generalize across neuron subtypes. These results expand conceptual understanding of how diverse circuits are precisely constructed and potentially evolve, and how coordinated dysregulation of GC molecules can disrupt precise subtype-specific circuitry, contributing to diverse neurodevelopmental and neuropsychiatric disorders.

neuroscience↗

bioRxiv2025

Developmental dynamics and axonal transport of cerebral cortex projection neuron mRNAs in vivo

Appropriate development of long-range nervous system circuitry requires dynamic regulation of subcellular mRNA localization, but little is known about how specific neuron subtypes control this critical process in vivo. Here, we employ an integrated genetic and temporally controlled approach to investigate in vivo developmental mRNA dynamics in somata and axons of a prototypical cerebral cortex projection neuron subtype, callosal projection neurons (CPN), which connect the cortical hemispheres to integrate sensorimotor information, and regulate high-level associative cognition and behavior. We identify cis-regulatory elements that are associated with mRNA turnover in CPN somata, including specific 3 untranslated regions (UTRs), and elucidate distinct modes of axon transport in CPN axons for function-specific mRNA classes. Together, these findings elucidate how developing CPN control subcellular mRNA localization, and how dysregulation of these processes might lead to neurodevelopmental and/or neurodegenerative disorders. More broadly, this work identifies general mRNA localization mechanisms that likely function across projection neuron subtypes, and in other polarized cells.

neuroscience↗

bioRxiv2024

Bcl11b orchestrates subcerebral projection neuron axon development via cell-autonomous, non-cell-autonomous, and subcellular mechanisms

Both cell-intrinsic competency and extracellular cues regulate axon projection, but mechanisms that coordinate these elements remain poorly understood. Subcerebral projection neurons (SCPN) extend their primary axons from cortex through subcortical structures, including the striatum, targeting the brainstem and spinal cord. We identify that the transcription factor Bcl11b/Ctip2 functions in multiple independent neuron populations to control SCPN axon development. Bcl11b expressed by SCPN is required cell-autonomously for axonal outgrowth and efficient entry into the internal capsule within the striatum, while Bcl11b expressed by medium spiny neurons (MSN) non-cell-autonomously regulates SCPN axon fasciculation within the internal capsule and subsequent pathfinding. Further, integrated investigation of Bcl11b-null SCPN with transcriptomic, immunocytochemical, and in vivo growth cone purification approaches identifies that Cdh13 is localized along axons and on growth cone surfaces of SCPN in vivo, and mediates Bcl11b regulation of SCPN axonal outgrowth. Together, these results demonstrate that Bcl11b controls multiple aspects of SCPN axon development by coordinating intrinsic SCPN cell autonomous subcellular mechanisms and extrinsic MSN non-cell-autonomous mechanisms.

neuroscience↗

bioRxiv2022

ASD gene Bcl11a regulates subcellular RNA localization, associative circuitry, and social behavior

Precise, area-specific connectivity of interhemispheric callosal projection neurons (CPN) in the cerebral cortex is critical for sensory, associative, and behavioral functions. CPN circuitry, which connects and integrates the cerebral hemispheres via the corpus callosum, is centrally implicated in autism spectrum disorder (ASD) and intellectual disability (ID). Though transcriptional controls regulating CPN subtype and areal development are partially understood, downstream subcellular molecular machinery that implements CPN circuitry is essentially unknown. Here, we identify that the highly penetrant ASD/ID risk gene Bcl11a/Ctip1 is critical developmentally for appropriate and precise areal targeting of superficial layer CPN (CPNSL) projections, and that its deletion strikingly re-routes some CPNSL projections subcortically, causes dramatic disruption to subcellular CPNSL growth cone (GC) molecular machinery, and disrupts social behavior and cognition in mice. CPNSL-specific embryonic deletion of Bcl11a causes loss of correct homotopic targeting in the contralateral cortex, re-routes a substantial proportion of axonal projections through the anterior commissure, and induces strikingly aberrant, but specific and precise, projections to the basolateral amygdala. Importantly, bilateral deletion of Bcl11a from CPNSL results in abnormal social behavior and working memory. Mechanistically, we identify dysregulation of the CPNSL axonal GC-localized transcriptome in Bcl11a nulls, due to either aberrant transcription or trafficking of individual transcripts. These molecular mis-localizations disrupt axon guidance and CPNSL circuitry formation. Together, this work identifies critical functions for Bcl11a in CPNSL axonal connectivity, development of functional associative-social circuitry, and regulation of subtype-specific subcellular molecular machinery in vivo, revealing novel GC-localized transcripts that regulate precise axonal targeting and circuit formation. These results elucidate development and ASD/ID disease-related circuit disruption of CPNSL, and the importance of understanding circuit-specific subcellular molecular machinery by neurons.

neuroscience↗