Emergence of crucial evidence catalyzing the origin tracing of SARS-CoV-2.

Since the emergence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), its genetic and geographical origins remain unclear, resulting in suspicions about its natural origin. In one of our previous studies, we reported the presence of a furin cleavage site RRAR in the junction region between S1 and S2 subunits of the spike protein, which was discovered as the first crucial clue for the origin tracing of SARS-CoV-2. In the present study, we conducted an integrative analysis of new genome data from bat Sarbecovirus strains reported after the COVID-19 outbreak. The primary results included the identification of BANAL-20-52, Rp22DB159, and S18CXBatR24 as three close relatives of SARS-CoV-2 and the successful detection of seven out of nine key genomic features (designated as RC0-7 and ORF8) observed in wild types of SARS-CoV-2 in the three close relatives from Laos, Vietnam, and Yunnan province of China, respectively. The most significant contribution of the present study lies in the detection of RC1 in wild genotype in a bat Sarbecovirus population BANAL-20-52 belonging to. Encoding a segment of the NSP3 protein, RC1 was discovered as the second crucial clue for the origin tracing of SARS-CoV-2. Although RC0, encoding the junction furin cleavage site, remains undetected outside of the SARS-CoV-2 genome, Feuang of Laos is the sole place where eight of the nine wild-type features (RC1-7 and ORF8) have been detected.

Re-analysis of single-cell RNA-seq data reveals the origin and roles of cycling myeloid cells.

Cycling myeloid cells (CMCs) are often detected from various tissues using single-cell RNA sequencing (scRNA-seq) datasets, however, their research value was not noticed before. For the first time, our study preliminarily revealed the origin, differentiation, and roles of CMCs in physiological processes. Particularly, subgroup a of cycling myeloid cells (aCMCs) were conclusively identified as belonging to a specific cell type. In an active state, aCMCs rapidly proliferate during the early stages of an embryonic development. With an individual maturing, most aCMCs differentiate into specialized cells, while a small portion of them enter an inactive or dormant state. Under pathological conditions, aCMCs restore their proliferative and differentiation capacities via activation or revival. The present study has set the stage for future research on CMCs by linking them with progenitors of immune cells, and provided a crucial starting point to understand the origin, differentiation, and roles of CMCs in various physiological and pathological processes, particularly those related to traumatic injury, cancer, and pathogen infection, leading to develop targeted therapies or interventions.