Human Bone Proteomes before and after Decomposition: Investigating the Effects of Biological Variation and Taphonomic Alteration on Bone Protein Profiles and the Implications for Forensic Proteomics.

Hayley L Mickleburgh,Haruka Mizukami,Sefora Starace,Noemi Procopio,Daniel J Wescott,Federica Sellitto,David O Carter,Andrea Bonicelli,Edward C Schwalbe

doi:10.1021/acs.jproteome.0c00992

Abstract

Bone proteomic studies using animal proxies and skeletonized human remains have delivered encouraging results in the search for potential biomarkers for precise and accurate post-mortem interval (PMI) and the age-at-death (AAD) estimation in medico-legal investigations. The development of forensic proteomics for PMI and AAD estimation is in critical need of research on human remains throughout decomposition, as currently the effects of both inter-individual biological differences and taphonomic alteration on the survival of human bone protein profiles are unclear. This study investigated the human bone proteome in four human body donors studied throughout decomposition outdoors. The effects of ageing phenomena (in vivo and post-mortem) and intrinsic and extrinsic variables on the variety and abundancy of the bone proteome were assessed. Results indicate that taphonomic and biological variables play a significant role in the survival of proteins in bone. Our findings suggest that inter-individual and inter-skeletal differences in bone mineral density (BMD) are important variables affecting the survival of proteins. Specific proteins survive better within the mineral matrix due to their mineral-binding properties. The mineral matrix likely also protects these proteins by restricting the movement of decomposer microbes. New potential biomarkers for PMI estimation and AAD estimation were identified. Future development of forensic bone proteomics should include standard measurement of BMD and target a combination of different biomarkers.

Highlights

Estimations of the time elapsed since death and the age-at-death (AAD) are crucial in the forensic investigation of unidentified human remains
We aimed to investigate the effects of taphonomy and biological variation on the recovery and variability of the human bone proteome and evaluate potential avenues to develop a broadly applicable, standardized method of postmortem interval (PMI) and AAD estimation in human remains in advanced state of decomposition.[35]
To the best of our knowledge, the present study is the only one conducted to date that has included such samples from controlled decomposition experiments, allowing us to examine the effects of taphonomic processes such as diagenesis and bioerosion on the bone protein profiles

Summary

Introduction

Estimations of the time elapsed since death (post-mortem interval, PMI) and the age-at-death (AAD) are crucial in the forensic investigation of unidentified human remains. This information is important to distinguish between historical remains (>100 years old) and remains of medico-legal relevance (≤100 years old)[1,2] and to narrow the search of missing persons for identification purposes.[3,4] High precision, accuracy, and objectivity of PMI and AAD estimation methods are essential in order to be considered admissible in a court of law. PMI estimation often relies on visual assessment of gross morphological changes of the body during decomposition,[5−7] even though the rate of these changes is known to be highly variable.[8,9] Accuracy of the PMI estimation decreases as decomposition progresses, and interobserver reliability differs depending on the method and the experience of the researcher.[9,10] Biochemical techniques have shown promising results in the search for a precise and accurate method to estimate late PMI in human bone; these methods are yet to be validated for use in forensic contexts.[11−14]

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Results

Conclusion