Dynamic proteomic and phosphoproteomic atlas of corticostriatal axons in neurodevelopment

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    Evaluation Summary:

    Knowledge of the protein composition of defined sub-cellular compartments is of key importance for the characterization of protein machines that mediate defined cellular functionalities. The current paper presents a novel mouse line that will serve as a helpful tool in this context - a Cre-inducible APEX2 reporter mouse line for acute ex-vivo proximity biotinylation. The paper documents the successful use of the novel reporter line to assess circuit-specific proteomes and phosphoproteomes in the corticostriatal system during development. The corresponding data largely align with the published record, but potentially new biological insights deduced from bioinformatic analyses of proteomic data were not followed up by experimental validation. In sum, the new APEX2 reporter mouse line will be of substantial interest to researchers in many fields of mammalian biology. The extent of 'new biology' provided is rather limited, but will be of interest to readers in neurodevelopment.

    (This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #2 agreed to share their name with the authors.)

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Abstract

Mammalian axonal development begins in embryonic stages and continues postnatally. After birth, axonal proteomic landscape changes rapidly, coordinated by transcription, protein turnover, and post-translational modifications. Comprehensive profiling of axonal proteomes across neurodevelopment is limited, with most studies lacking cell-type and neural circuit specificity, resulting in substantial information loss. We create a Cre-dependent APEX2 reporter mouse line and map cell-type-specific proteome of corticostriatal projections across postnatal development. We synthesize analysis frameworks to define temporal patterns of axonal proteome and phosphoproteome, identifying co-regulated proteins and phosphorylations associated with genetic risk for human brain disorders. We discover proline-directed kinases as major developmental regulators. APEX2 transgenic reporter proximity labeling offers flexible strategies for subcellular proteomics with cell type specificity in early neurodevelopment, a critical period for neuropsychiatric disease.

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  1. Evaluation Summary:

    Knowledge of the protein composition of defined sub-cellular compartments is of key importance for the characterization of protein machines that mediate defined cellular functionalities. The current paper presents a novel mouse line that will serve as a helpful tool in this context - a Cre-inducible APEX2 reporter mouse line for acute ex-vivo proximity biotinylation. The paper documents the successful use of the novel reporter line to assess circuit-specific proteomes and phosphoproteomes in the corticostriatal system during development. The corresponding data largely align with the published record, but potentially new biological insights deduced from bioinformatic analyses of proteomic data were not followed up by experimental validation. In sum, the new APEX2 reporter mouse line will be of substantial interest to …

  2. Reviewer #1 (Public Review):

    The aim of the present study was to develop and validate a novel mouse model that allows to determine the proteome of defined sub-cellular compartments, and to use this model in order to elucidate the molecular processes that govern the establishment of synaptic contacts between cortical and striatal neurons in the brain. Given that knowledge of the protein composition of defined sub-cellular compartments is of key importance for the characterisation of protein machines that mediate defined cellular functionalities, the establishment of corresponding mouse models to study such issues is of major general interest. The same is true for the development and function of cortico-striatal connectivity in the brain, which plays key roles in multiple major brain processes and is perturbed in many neuropsychiatric …

  3. Reviewer #2 (Public Review):

    This work by Dumrongprechachan and colleagues establishes a new method to isolate and quantify projection-specific axon proteomes using a genetically-targeted biotin ligase approach in the mouse brain. The authors developed a new mouse line that expresses CRE-dependent APEX2 to genetically target proteomes in specific cell types for acute ex vivo biotin labeling. They use this method to interrogate axon proteomes and phosphoproteomes during the development of corticostriatal projections in mice, providing rich datasets that can be mined in the context of future studies into brain circuit development.

    This work is particularly useful for the new Cre-dependent biotin ligase mouse and projection proteomics methodological pipeline. The flexed Rosa26 Apex2 mouse line is robustly characterized and will no doubt …

  4. Reviewer #3 (Public Review):

    In this work, Dumrongprechachan et al. impressively expanded their earlier work on the identification of cell type-specific subcellular proteomes from mouse brain by APEX2 proximity labeling. Instead of using viral expression of APEX2, the authors now created a Cre-dependent APEX2 reporter mouse line using CRISPR knock-in, which can be combined with multiple Cre-driver lines for proteomic applications. Using this novel tool in combination with sophisticated mass spectrometry and elegant bioinformatics, they mapped the temporal dynamics of the axonal proteome in corticostriatal projections (instead of only identifying a static cell type- and compartment-specific proteome) together with its phosphorylation status (instead of only looking at protein abundance). The data will provide a valuable resource on …