Functional role for Cas cytoplasmic adaptor proteins during cortical axon pathfinding
Jason A. Estep, Alyssa M. Treptow, Payton A. Rao, Patrick Williamson, Wenny Wong, Martin M. Riccomagno
Abstract
Proper neural circuit organization requires individual neurons to project to their targets with high specificity. While several guidance molecules have been shown to mediate axonal fasciculation and pathfinding, less is understood about how neurons intracellularly interpret and integrate these cues. Here we provide genetic evidence that the Crk-Associated Substrate (Cas) family of intracellular adaptor proteins is required for proper fasciculation and guidance of two cortical white matter tracts: the Anterior Commissure (AC) and thalamocortical axons (TCAs).
Introduction
During Central Nervous System (CNS) development, axons often traverse complex routes to meet their synaptic targets, interacting with a diverse array of attractive, repulsive, and permissive cues [1,2]. One developmental mechanism proposed to ensure proper guidance of large tracts is the concept of “pioneer” versus “follower” axons [3–7].
Materials and method
Ethics approval: All animal procedures presented here were performed according to the University of California, Riverside’s Institutional Animal Care and Use Committee (IACUC)-approved guidelines, under protocol A-8.
Results
To investigate the potential roles of Cas family genes during cortical white matter tract formation, we began by assessing the expression of the Cas family paralogues during cortical development. We recently established that transcripts for the paralogues p130Cas, CasL/Nedd9, and Sin/Efs are all expressed in the developing neocortex, with overlapping expression in the subventricular and ventricular zones [43].
Discussion
In this study, we used conditional mouse genetics to assess the cortical-autonomous and neuronal-autonomous roles of Cas genes during forebrain white matter tract formation. Using a Cas triple conditional knockout (Cas TcKO) model, we provide strong genetic evidence that Cas proteins are required in two manners: 1) cortical- and neuronal-autonomously for proper fasciculation of the posterior branch of the Anterior Commissure (pAC) (Figs 3B', 3D and 5), and 2) cortical- and non-neuronal autonomously for thalamocortical axon (TCA) guidance (Figs 3B'', 3H and 5).
Acknowledgments
We would like to thank Dr. Teresa Ubina for critically reading the manuscript and providing helpful comments. We would like to thank Drs. Nave and Goebbels for the Nex-Cre mice. We would also like to thank Drs. Sachiko Seo and Mineo Kurokawa, and Dr. Konstantina Alexandropoulos for sharing the CasL-/- and Sin-/- mouse lines, respectively.
Citation: Estep JA, Treptow AM, Rao PA, Williamson P, Wong W, Riccomagno MM (2025) Functional role for Cas cytoplasmic adaptor proteins during cortical axon pathfinding. PLoS Genet 21(11): e1011941. https://doi.org/10.1371/journal.pgen.1011941
Editor: Ophir Klein, University of California San Francisco, UNITED STATES OF AMERICA
Received: July 2, 2025; Accepted: October 28, 2025; Published: November 7, 2025
Copyright: © 2025 Estep et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the manuscript and its Supporting information files.
Funding: HHS | NIH | National Institute of Neurological Disorders and Stroke (NINDS)(https://www.ninds.nih.gov):(MMR) R01NS139914; California Institute for Regenerative Medicine (CIRM)(https://www.cirm.ca.gov):(AMT) TRANSCEND. The content is solely the responsibility of the authors and does not necessarily represent the official views of the funding agencies. The funders did not play any role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
