Profiling 26,000 Aplysia californica neurons by single cell mass spectrometry reveals neuronal populations with distinct neuropeptide profiles

Data-Driven and Machine Learning-Based Framework for Image-Guided Single-Cell Mass Spectrometry

“…Specifically, the goal is to obtain a structured representation pertaining to target variables with supervision. For this purpose, we trained a machine learning model to predict neurons from 6 major types of Aplysia ganglia and acquired SHAP values for each cell. Neurons can be accurately classified based on the peptide content (Figure A), consistent with previous studies on peptide localizations in the Aplysia central nervous system. , UMAP and Leiden clustering on the SHAP values reveal distinct clusters of neurons with respect to ganglion types (Figure B).…”

“…Data-driven methods have long been the major developmental hub for single-cell analysis. Unsupervised and supervised approaches serve as the two common bases for analyzing complex single-cell data sets, especially for RNA-seq data. − Unsupervised data analysis approaches, such as dimensionality reduction and clustering, aim to construct compact and easily interpretable representations from the high-dimensional data. , In contrast, supervised data analysis approaches seek to optimize the prediction of specific output values through learning a set of model weights. , Both unsupervised and supervised approaches have been applied extensively for single-cell MS, with the former focusing on exploratory tasks and the latter differentiating between cell types or phenotypes. − An integrated computational workflow for diverse applications of image-guided MS would standardize the information extracted from data sets collected under various experimental settings.…”

Uncovering biology by single-cell proteomics

“…Neuropeptides are a diverse class of cell-to-cell signaling molecules that are widely expressed throughout the central nervous system, often in a cell-type-specific manner. Recently, a microscopy-guided, high-throughput single-cell matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) approach was developed to investigate the neuropeptide heterogeneity of individual neurons in the central nervous system of the neurobiological model Aplysia californica 32 . In this study, >26,000 neurons from 18 animals were analyzed, and 866 peptides were assigned to 66 prohormones.…”

Characterization of an Aplysia vasotocin signaling system and actions of posttranslational modifications and individual residues of the ligand on receptor activity

“…We sought to study an oxytocin/vasopressin signaling system in the gastropod mollusc Aplysia californica . Aplysia is an experimentally-advantageous system and has provided fundamental insight into the neural basis of motivated behaviors ( Jing and Weiss, 2002 ; Jing et al, 2004 ; Sasaki et al, 2009 ; Jing et al, 2010 ; Sasaki et al, 2013 ; Zhang et al, 2020 ; Bedecarrats et al, 2021 ; Evans et al, 2021 ; Due et al, 2022 ; Wang et al, 2023 ), learning and memory ( Sieling et al, 2014 ; Byrne and Hawkins, 2015 ; Orvis et al, 2022 ) and neuromodulation ( Cropper et al, 2018b ; Zhang et al, 2022 ), including neuropeptides ( Livnat et al, 2016 ; Zhang et al, 2017 ; Do et al, 2018 ; Zhang et al, 2018 ; Chan-Andersen et al, 2022 ) and receptors ( Bauknecht and Jekely, 2015 ; Checco et al, 2018 ; Guo et al, 2022 ; Jiang et al, 2022 ; Zhang et al, 2022 ). The first evidence for the presence of oxytocin/vasopressin-related neuropeptide in protostomes comes from an early immunohistochemical study ( Remy et al, 1979 ), and the later identification of an arginine vasopressin-like diuretic hormone ( Proux et al, 1987 ), both in insects.…”