Kieran, N. W. | Search bioRxiv

bioRxiv2023

MerTK mediates the immunologically silent uptake of alpha-synuclein fibrils by human microglia

MerTK is a receptor tyrosine kinase that mediates the immunologically silent phagocytic uptake of diverse types of cellular debris. Highly expressed on the surface of microglial cell, MerTK is of importance in brain development, homeostasis, plasticity, and disease. Yet, involvement of this receptor in the clearance of protein aggregates that accumulate with aging and in neurodegenerative diseases has yet to be defined. The current study explored the function of MerTK in the microglial uptake of alpha-synuclein fibrils which play a causative role in the pathobiology of synucleinopathies. Using human primary and induced pluripotent stem cell-derived microglia, the MerTK- dependence of alpha-synuclein fibril internalization was investigated in vitro. Relevance of this pathway to synucleinopathies was assessed by analyzing MerTK expression in patient-derived cells and tissues. Pharmacological inhibition of MerTK and siRNA-mediated MERTK knockdown both caused a decreased rate of alpha-synuclein fibril internalization by human microglia. Consistent with the immunologically silent nature of MerTK-mediated phagocytosis, alpha-synuclein fibril internalization did not induce secretion of pro-inflammatory cytokines from microglia. In addition, burden analysis in two independent patient cohorts revealed a significant association between rare functionally deleterious MERTK variants and Parkinsons disease in one of the cohorts (p = 0.002). Accordingly, MERTK expression was significantly upregulated in nigral microglia from Parkinsons disease/Lewy body dementia patients compared to those from non-neurological control donors in a single-nuclei RNA-sequencing dataset (p = 5.08x10-21), and MerTK protein expression positively correlated with alpha-synuclein level in human cortex lysates (p = 0.0029). Taken together, our findings define a novel role for MerTK in mediating the uptake of alpha-synuclein aggregates by human microglia, with possible involvement in limiting alpha-synuclein spread in synucleinopathies such as Parkinsons disease.

cell biology↗

bioRxiv2020

Integrated analysis of high throughput transcriptomic data revealed specific gene expression signature of cardiomyocytes

Acquiring a specific transcriptomic signature of the human and mouse cardiomyocyte (CM) will greatly increase our understanding of their biology and associated diseases that remain the most deadly across the world. In this study, using comprehensive transcriptomic mining of 91 cell types over 877 samples from bulk RNA-sequencing, single cell RNA-sequencing, and microarray techniques, we describe a unique 118-gene signature of human and mouse primary CMs. Once we had access to this CM-specific gene signature, we investigated the spatial heterogeneity of CMs throughout the heart tissue. Moreover, we compared the CM-specific gene signature to that of CMs derived from 10 differentiation protocols, and we identified the protocols that generate cells most similar to primary CMs. Finally, we looked at the specific differences between primary and differentiated CMs and found that differentiated cells underexpress genes related to CM development and maturity. The differentiated cells conversely overexpressed cell cycle-related genes, resulting in the progenitor features that remain in differentiated CMs compared to primary adult CMs. The presence of histone post translational modification H3K27ac from ChIP sequencing data sets were used to confirm transcriptomic findings. To the best of our knowledge, this is the most comprehensive study to date that unravels the unique transcriptomic signature of primary and differentiated CMs. This study provides important insights into our understanding of CM biology and the molecular mechanisms that make them such a unique cell type. Moreover, the specific transcriptomic signature of CMs could be used in developmental studies, stem cell therapy, regenerative medicine, and drug screening assays.

cell biology↗