RESUMEN
Peste des petits ruminants virus (PPRV) is an important agent of contagious, acute and febrile viral diseases in small ruminants, while its evolutionary dynamics related to codon usage are still lacking. Herein, we adopted information entropy, the relative synonymous codon usage values and similarity indexes and codon adaptation index to analyze the viral genetic features for 45 available whole genomes of PPRV. Some universal, lineage-specific, and gene-specific genetic features presented by synonymous codon usages of the six genes of PPRV that encode N, P, M, F, H and L proteins reflected evolutionary plasticity and independence. The high adaptation of PPRV to hosts at codon usages reflected high viral gene expression, but some synonymous codons that are rare in the hosts were selected in high frequencies in the viral genes. Another obvious genetic feature was that the synonymous codons containing CpG dinucleotides had weak tendencies to be selected in viral genes. The synonymous codon usage patterns of PPRV isolated during 2007-2008 and 2013-2014 in China displayed independent evolutionary pathway, although the overall codon usage patterns of these PPRV strains matched the universal codon usage patterns of lineage IV. According to the interplay between nucleotide and synonymous codon usages of the six genes of PPRV, the evolutionary dynamics including mutation pressure and natural selection determined the viral survival and fitness to its host.
RESUMEN
Tissue mechanics provides an appropriate niche for cell growth and functions. Integrin proteins play a pivotal role in mechanosensing associated with both extracellular matrix and intracellular cytoskeleton proteins. Endocytosis of integrin ß1 of BMMSCs on collagen I-coated soft substrates promotes cell differentiation, providing a mechanism that cell senses elasticity through integrin. To determine whether other integrin subunits act the same way in BMMSCs, we carried on immunocytochemical staining and biotin labeling experiments to assay their subcellular distribution on stiff and soft hydrogels. Our results indicate that, consistent with our previous studies conducted on ß1 integrin, more integrin α1 and α2 were internalized on collagen I-coated soft substrates compared with stiff substrate counterparts. This internalization is mainly mediated by caveolin-dependent endocytosis and would involve in soft matrix-promoted neurogentic lineage commitment. Cells on hydrogels coated by fibronectin and laminin, respective ligands of integrin α5 and α6, demonstrated no apparent soft substrate inducing endocytosis of these two subunits. These findings suggest that integrin-mediated mechanosensing is coupling with ECM ligands.