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

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 postmortem 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 mineralbinding 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.

Insights into the Differential Preservation of Bone Proteomes in Inhumed and Entombed Cadavers from Italian Forensic Caseworks

“…It is not possible to exclude, as indicated previously, that other factors able to affect PTMs may be associated with the physicochemical and structural properties of the proteins as well as with both interskeletal and interindividual variability. 3 , 5 Therefore, more systematic models should be created to fully untangle the biochemistry on the accumulation of PTMs in different burial environments.…”

“… 1 , 3 , 4 There are also intrinsic biological factors that can affect post-mortem changes such as body size, age, and trauma. 5 All of these variables must be considered when developing estimation methods for forensic purposes. One of the most commonly utilized methods for PMI estimation is the evaluation of the formation of adipocere.…”

“… 12 , 13 Among the biomolecular methods, proteomics is attracting great interest in the forensic community, despite representing a relatively new field that needs further evaluations and validations before its application to forensic investigations. 5 , 14 − 18 The analysis of the proteome offers a large pool of potential biomarkers with different physicochemical and biological properties that could allow the development of statistical models capable of accounting for intrinsic and extrinsic taphonomic variables, reducing biases in PMI estimation, and increasing its accuracy.…”

The Texas State Donated Skeletal Collection at the Forensic Anthropology Center at Texas State

“…To date, several methods related to the biological profile have been developed or tested using the TXSTDSC. Age estimation methods ranging from the use of gross morphological indicators of age with the application of Sugeno fuzzy integrals [10,11] to DNA methylation [12] and proteomic changes [13] have been studied using the TXSTDSC. The collection is ideal for studies focused on a geriatric population and the development of methods for extending age-at-death estimation beyond 50 plus years.…”

“…An additional important contribution for forensic anthropological research is the accompanying taphonomic data for most of the skeletal remains in the TXSTDSC. This allows researchers to examine the taphonomic influence on morphoscopic and chemical indicators used to develop the biological profile and postmortem interval [13,[26][27][28][29] as well as to distinguish postmortem damage from perimortem trauma. Since some donors provide consent for advanced research, novel and ground-breaking approved studies focused on thermal, ballistic, sharp, and blunt force trauma are possible [30,31].…”