Abstract
C57BL/6J (B6) and DBA/2J (D2) inbred mouse strains are highly variable genetically and differ in a large number of behavioral traits related to striatal function, including depression, anxiety, stress response, and response to drugs of abuse. The genetic basis of these phenotypic differences are, however, unknown. Here, we present a comparison of the striatal proteome between B6 and D2 and relate differences at the protein level to strain differences at the mRNA level. We also leverage a recombinant inbred BXD population derived from B6 and D2 strains to investigate the role of genetic variation on the regulation of mRNA and protein levels. Finally, we test the hypothesis that differential protein expression contributes to differential behavioral responses between the B6 and D2 strain. We detected the expression of over 2,500 proteins in membrane-enriched protein fractions from B6 and D2 striatum. Of these, 160 proteins demonstrated significant differential expression between B6 and D2 strains at a 10% false discovery level, including COMT, GABRA2, and cannabinoid receptor 1 (CNR1)—key proteins involved in synaptic transmission and behavioral response. Similar to previous reports, there was little overlap between protein and transcript levels (25%). However, the overlap was greater (51%) for proteins demonstrating genetic regulation of cognate gene expression. We also found that striatal proteins with significantly higher or lower relative expression in B6 and D2 were enriched for dopaminergic and glutamatergic synapses and processes involved in synaptic plasticity [e.g., long-term potentiation (LTP) and long-term depression (LTD)]. Finally, we validated higher expression of CNR1 in B6 striatum and demonstrated greater sensitivity of this strain to the locomotor inhibiting effects of the CNR1 agonist, Δ9-tetrahydrocannabinol (THC). Our study is the first comparison of differences in striatal proteins between the B6 and D2 strains and suggests that alterations in the striatal proteome may underlie strain differences in related behaviors, such as drug response. Furthermore, we propose that genetic variants that impact transcript levels are more likely to also exhibit differential expression at the protein level.
Highlights
High throughput and low-cost global quantification of proteins is not yet feasible
differentially expressed (DE) proteins with higher relative expression in D2 striatum were significantly enriched for KEGG terms including metabolic pathways, dopaminergic synapse, long-term potentiation (LTP), and cAMP signaling pathway (Figure 3, Supplementary Table S2)
Proteins with higher relative expression in B6 were significantly enriched for KEGG terms related to metabolic pathways, dopaminergic synapse, long-term depression (LTD), and glutamatergic synapse (Figure 3, Supplementary Table S2)
Summary
Advances in generation sequencing technologies have resulted in the ability to identify most sequence variants segregating across genomes and to profile the abundance of most species of transcribed RNA present in a sample at high throughput and low cost. To better understand biological systems and the relationship between genetic variation and behavioral variation, it is essential to identify and quantify all intervening molecular products. Many data sets identifying differential transcript expression among genetically divergent individuals have been generated over the past few decades. Some of these data sets explore the role of genetic variation in regulating transcript expression. The paucity of proteomic data sets represents a severe knowledge gap that limits our understanding of biological systems
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
