Label-Free Quantification (LFQ) of Fecal Proteins for Potential Pregnancy Detection in Polar Bears

• Published in: Life
• Main Authors: Erin Curry, Megan E. Philpott, Jessye Wojtusik, Wendy D. Haffey, Michael A. Wyder, Kenneth D. Greis, Terri L. Roth
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2022
• Subjects: wildlife; non-invasive monitoring; pseudopregnancy; embryonic diapause; fecal proteomics; Science; Q; Ursus maritimus
• Online Access: https://doi.org/10.3390/life12060796; https://doaj.org/article/2f90669015e5469987f60f9dab887635

Reliable pregnancy diagnostics would be beneficial for monitoring polar bear ( Ursus maritimus ) populations both in situ and ex situ, but currently there is no method of non-invasive pregnancy detection in this species. Recent reports in several carnivore species described the identification of fecal proteins that may serve as pregnancy biomarkers; however, repeatability has been limited. The objective of the current analysis was to utilize an unbiased, antibody-free, label-free method for the identification and quantification of fecal proteins to determine if differences associated with pregnancy are detectable in polar bears. Protein was extracted from fecal samples ( n = 48) obtained from parturient ( n = 6) and non-parturient ( n = 6) profiles each at four timepoints: pre-breeding season, embryonic diapause, early placental pregnancy, and mid-placental pregnancy. Protein was prepared and analyzed on the Thermo Orbitrap Eclipse nanoLC-MS/MS system. A total of 312 proteins was identified and quantified; however, coefficients of variation (CV) were high for both abundance ratio variability (384.8 ± 61.0% SEM) and within group variability (86.8 ± 1.5%). Results of this study suggest that the inconsistencies in specific protein concentrations revealed previously by antibody-based assays may not be due to that methodology’s limitations, but rather, are reflective of true variation that exists among samples.