Evolutionary analysis of the anti-viral STAT2 gene of primates and rodents: Signature of different stages of an arms race.

STAT2 plays a strategic role in defending viral infection through the signaling cascade involving the immune system initiated after type I interferon release. Many flaviviruses target the inactivation or degradation of STAT2 as a strategy to impair this host's line of defense. Primates are natural reservoirs for a range of disease-causing flaviviruses (e.g., Zika, Dengue, and Yellow Fever virus), while rodents appear less susceptible. We analyzed the STAT2 coding sequence of 28 Rodentia species and 49 Primates species. Original data from 19 Platyrrhini species were sequenced for the SH2 domain of STAT2 and included in the analysis. STAT2 has many sites whose variation can be explained by positive selection, measurement by two methods (PALM indicated 12, MEME 61). Both evolutionary tests significantly marked sites 127, 731, 739, 766, and 780. SH2 is under evolutionary constraint but presents episodic positive selection events within Rodentia: in one of them, a moderately radical change (serine > arginine) at position 638 is found in Peromyscus species, and can be implicated in the difference in susceptibility to flaviviruses within Rodentia. Some other positively selected sites are functional such as 5, 95, 203, 251, 782, and 829. Sites 251 and 287 regulate the signaling mediated by the JAK-STAT2 pathway, while 782 and 829 create a stable tertiary structure of STAT2, facilitating its connection with transcriptional co-activators. Only three positively selected sites, 5, 95, and 203, are recognized members who act on the interface between STAT2 and flaviviruses NS5 protein. We suggested that due to the higher evolutionary rate, rodents are, at this moment, taking some advantage in the battle against infections for some well-known Flaviviridae, in particular when compared to primates. Our results point to dynamics that fit with a molecular evolutionary scenario shaped by a thought-provoking virus-host arms race.

Comparative Genomics Identifies Putative Interspecies Mechanisms Underlying Crbn-Sall4-Linked Thalidomide Embryopathy.

The identification of thalidomide-Cereblon-induced SALL4 degradation has brought new understanding for thalidomide embryopathy (TE) differences across species. Some questions, however, regarding species variability, still remain. The aim of this study was to detect sequence divergences between species, affected or not by TE, and to evaluate the regulated gene co-expression in a murine model. Here, we performed a comparative analysis of proteins experimentally established as affected by thalidomide exposure, evaluating 14 species. The comparative analysis, regarding synteny, neighborhood, and protein conservation, was performed in 42 selected genes. Differential co-expression analysis was performed, using a publicly available assay, GSE61306, which evaluated mouse embryonic stem cells (mESC) exposed to thalidomide. The comparative analyses evidenced 20 genes in the upstream neighborhood of NOS3, which are different between the species who develop, or not, the classic TE phenotype. Considering protein sequence alignments, RECQL4, SALL4, CDH5, KDR, and NOS2 proteins had the biggest number of variants reported in unaffected species. In co-expression analysis, Crbn was a gene identified as a driver of the co-expression of other genes implicated in genetic, non-teratogenic, limb reduction defects (LRD), such as Tbx5, Esco2, Recql4, and Sall4; Crbn and Sall4 were shown to have a moderate co-expression correlation, which is affected after thalidomide exposure. Hence, even though the classic TE phenotype is not identified in mice, a deregulatory Crbn-induced mechanism is suggested in this animal. Functional studies are necessary, especially evaluating the genes responsible for LRD syndromes and their interaction with thalidomide-Cereblon.

Evolutionary analysis of the Musashi family: What can it tell us about Zika?

Despite worldwide research efforts since 2015, Zika virus infection and its consequences are not fully understood yet. Nowadays, it is known that microcephaly is only one of the possible outcomes of being infected by ZIKV during the early stages of life. Musashi 1 (MSI1) is an RNA-binding protein that is involved in neurodevelopmental processes. Also, ZIKV genome (a single-stranded positive-sense RNA) uses MSI1 for its replication. Here we perform an evolutionary analysis of MSI1 coding sequence and their orthologs in vertebrate species. We added original sequencing data from selected regions of interest (RNA-binding domains-RBDs of MSI1) of sixteen Platyrrhini (or New World monkeys), known to have high evolutionary rates. The Musashi family (MF) includes MSI2, TARDBP, DAZAP1, HNRNPD, HNRNPDL, and HNRNPAB, which do not interact with the virus but are critical RNA-binding proteins that act on many regulatory processes ubiquitously. We found that all sixteen primate species have the RBD1 of MSI1 conserved. While the general code sequences of MF genes are under purifying selection, the evolution of regulatory mechanisms, especially alternative splicing, seems to be a frequent phenomenon in these genes. Different isoforms differ in the N-terminal region and it affects protein size. Existing MSI1 isoforms probably diverge in their binding affinity, the kinetics of interaction, and other aspects when in the MSI1-ZIKV complex. It is a signal that some RBD-containing MSI1 isoforms can be incompatible to ZIKV binding and replication. Consequently, the chance of ZIKV successfully infecting host cells could also be associated with alternative splicing and expression of ZIKV-compatible MSI1 isoforms in both inter and intraspecific levels.