CD4+ regulatory T cells lacking Helios and Eos

The transcriptional regulators that drive regulatory T (Treg) cell development and function remain partially understood. Helios (Ikzf2) and Eos (Ikzf4) are closely-related members of the Ikaros family of transcription factors. They are highly expressed in CD4+ Treg cells and functionally important for Treg cell biology, as mice deficient for either Helios or Eos are susceptible to autoimmune diseases. However, it remains unknown if these factors exhibit specific or partially redundant functions in Treg cells. Here we show that mice with germline deletions of both Ikzf2 and Ikzf4 are not very different from animals with single Ikzf2 or Ikzf4 deletions. Double knockout Treg cells differentiate normally, and efficiently suppress effector T cell proliferation in vitro. Both Helios and Eos are required for optimal Foxp3 protein expression. Surprisingly, Helios and Eos regulate different, largely non-overlapping, sets of genes. Only Helios is required for proper Treg cell aging, as Helios deficiency results in reduced Treg cell frequencies in the spleen of older animals. These results indicate that Helios and Eos are required for distinct aspects of Treg cell function.

Functional specificity of the left ventrolateral prefrontal cortex in positive reappraisal: A single-pulse transcranial magnetic stimulation study

Neuroimage studies have yielded evidence for a correlation between the left ventrolateral prefrontal cortex (VLPFC) and a specific type of cognitive reappraisal strategy, positive reappraisal. However, evidence is still lacking for a direct relation. We used single-pulse transcranial magnetic stimulation (TMS) over the left VLPFC at different time points to investigate the functional specificity of the left VLPFC in the success of positive reappraisal and the timing at which the left VLPC was involved in positive reappraisal. Fifteen participants engaged in a baseline experiment and in TMS experiments. All participants successfully reduced their negative emotional ratings using positive reappraisal in the baseline experiment. In the TMS experiments, participants performed the same task as in the baseline experiment but single-pulse TMS was applied over the left VLPFC at 300 ms or/and 3,300 ms after stimulus onset, as well as over the vertex as a control stimulation. Valence ratings of negative stimuli increased (unpleasantness reduction) when participants reappraised negative stimuli with TMS stimulation over the left VLPFC, regardless of the timing of the stimulation at 300 ms or/and at 3,300 ms after the stimulus onset, relative to the vertex stimulation and the baseline experiment. Our study provided evidence of the functional specificity of the left VLPFC in regulation of negative emotions using positive reappraisal. The left VLPFC was believed to be involved in different stages of positive reappraisal. The prominent facilitation effect of TMS over the left VLPFC makes it possible to consider potential applications in clinical practice for mood disorders.

Unraveling the molecular basis of host cell receptor usage in SARS-CoV-2 and other human pathogenic β-CoVs

The recent emergence of the novel SARS-CoV-2 in China and its rapid spread in the human population has led to a public health crisis worldwide. Like in SARS-CoV, horseshoe bats currently represent the most likely candidate animal source for SARS-CoV-2. Yet, the specific mechanisms of cross-species transmission and adaptation to the human host remain unknown. Here we show that the unsupervised analysis of conservation patterns across the β-CoV spike protein family, using sequence information alone, can provide valuable insights on the molecular basis of the specificity of β-CoVs to different host cell receptors. More precisely, our results indicate that host cell receptor usage is encoded in the amino acid sequences of different CoV spike proteins in the form of a set of specificity determining positions (SDPs). Furthermore, by integrating structural data, in silico mutagenesis and coevolution analysis we could elucidate the role of SDPs in mediating ACE2 binding across the Sarbecovirus lineage, either by engaging the receptor through direct intermolecular interactions or by affecting the local environment of the receptor binding motif. Finally, by the analysis of coevolving mutations across a paired MSA we were able to identify key intermolecular contacts occurring at the spike-ACE2 interface. These results show that effective mining of the evolutionary records held in the sequence of the spike protein family can help tracing the molecular mechanisms behind the evolution and host-receptor adaptation of circulating and future novel β-CoVs.

Speech-accompanying gestures are not processed by the language-processing mechanisms

Speech-accompanying gestures constitute one information channel during communication. Some have argued that processing gestures engages the brain regions that support language comprehension. However, studies that have been used as evidence for shared mechanisms suffer from one or more of the following limitations: they (a) have not directly compared activations for gesture and language processing in the same study and relied on the fallacious reverse inference (Poldrack, 2006) for interpretation, (b) relied on traditional group analyses, which are bound to overestimate overlap (e.g., Nieto-Castañon and Fedorenko, 2012), (c) failed to directly compare the magnitudes of response (e.g., Chen et al., 2017), and (d) focused on gestures that may have activated the corresponding linguistic representations (e.g., "emblems"). To circumvent these limitations, we used fMRI to examine responses to gesture processing in language regions defined functionally in individual participants (e.g., Fedorenko et al., 2010), including directly comparing effect sizes, and covering a broad range of spontaneously generated co-speech gestures. Whenever speech was present, language regions responded robustly (and to a similar degree regardless of whether the video contained gestures or grooming movements). In contrast, and critically, responses in the language regions were low - at or slightly above the fixation baseline - when silent videos were processed (again, regardless of whether they contained gestures or grooming movements). Brain regions outside of the language network, including some in close proximity to its regions, differentiated between gestures and grooming movements, ruling out the possibility that the gesture/grooming manipulation was too subtle. Behavioral studies on the critical video materials further showed robust differentiation between the gesture and grooming conditions. In summary, contra prior claims, language-processing regions do not respond to co-speech gestures in the absence of speech, suggesting that these regions are selectively driven by linguistic input (e.g., Fedorenko et al., 2011). Although co-speech gestures are uncontroversially important in communication, they appear to be processed in brain regions distinct from those that support language comprehension, similar to other extra-linguistic communicative signals, like facial expressions and prosody.

Comparative structure-function features of Hsp70s of Plasmodium falciparum and human origins

The heat shock protein 70 (Hsp70) family of molecular chaperones are crucial for the survival and pathogenicity of the main agent of malaria, Plasmodium falciparum. Hsp70 is central to cellular proteostasis and some of its isoforms are essential for survival of the malaria parasite. In addition, they are also implicated in the development of antimalarial drug resistance. For these reasons, they are thought to be potential drug targets, especially in antimalarial combination therapies. However, their high sequence conservation across species presents a hurdle with respect to their selective targeting. The human genome encodes 17 Hsp70 isoforms while P. falciparum encodes for only 6. The structural architecture of Hsp70s is typically characterized by a highly conserved N-terminal nucleotide-binding domain (NBD) and a less conserved C-terminal substrate-binding domain (SBD). The two domains are connected by a highly conserved linker. In spite of their fairly high sequence conservation, Hsp70s from various species possess unique signature motifs that appear to uniquely influence their function. In addition, their cooperation with co-chaperones further regulates their functional specificity. In the current review, bioinformatics tools were used to identify conserved and unique signature motifs in Hsp70s of P. falciparum versus their human counterparts. We discuss the common and distinctive structure-function features of these proteins. This information is important towards elucidating the prospects of selective targeting of parasite heat shock proteins as part of antimalarial design efforts.

A robust SSFP technique for fMRI at ultra-high field strengths

A non-balanced (nb) SSFP-based fMRI method based on CE-FAST is presented to alleviate some shortcomings of high spatial-specificity techniques commonly used in high static magnetic fields. The proposed sequence does not suffer from the banding artifacts inherent to balanced (b) SSFP, has low geometrical distortions and SAR compared to spin-echo EPI, and in contrast to previous nbSSFP implementations, is applied at a TR, theoretically prescribed for the optimum contrast. Its non-balanced gradient was chosen to just dephase the unwanted signal component (2π dephasing per TR per voxel). 3D data were acquired from nine healthy subjects, who performed a visual-motor task on a 7 Tesla scanner. For comparison, experiments were accompanied by similar bSSFP and spin-echo acquisitions. Consistent activation was achieved in all subjects with theoretically optimal TR, in contrast to previous nbSSFP techniques. The signal stability as well as relative and absolute functional signal changes, were found to be comparable with bSSFP and spin-echo techniques. The results suggest that with suitable modifications, CE-FAST can be regarded as a robust SSFP-based method for high spatial specificity fMRI techniques.

Multifarious determinants of cytokine receptor signaling specificity

Cytokines play crucial roles in regulating immune homeostasis. Two important characteristics of most cytokines are pleiotropy, defined as the ability of one cytokine to exhibit diverse functionalities, and redundancy, defined as the ability of multiple cytokines to exert overlapping activities. Identifying the determinants for unique cellular responses to cytokines in the face of shared receptor usage, pleiotropy, and redundancy will be essential in order to harness the potential of cytokines as therapeutics. Here, we discuss the biophysical (ligand-receptor geometry and affinity) and cellular (receptor trafficking and intracellular abundance of signaling molecules) parameters that contribute to the specificity of cytokine bioactivities. Whereas the role of extracellular ternary complex geometry in cytokine-induced signaling is still not completely elucidated, cytokine-receptor affinity is known to impact signaling through modulation of the stability and kinetics of ternary complex formation. Receptor trafficking also plays an important and likely underappreciated role in the diversification of cytokine bioactivities but it has been challenging to experimentally probe trafficking effects. We also review recent efforts to quantify levels of intracellular signaling components, as second messenger abundance can affect cytokine-induced bioactivities both quantitatively and qualitatively. We conclude by discussing the application of protein engineering to develop therapeutically relevant cytokines with reduced pleiotropy and redirected biological functionalities.

Reverse inference is not a fallacy per se: cognitive processes can be inferred from functional imaging data

When inferring the presence of a specific cognitive process from observed brain activation a kind of reasoning is applied that is called reverse inference. Poldrack (2006) rightly criticized the careless use of reverse inference. As a consequence, reverse inference is assumed as intrinsically weak by many and its validity has been increasingly regarded as limited. Although it is undisputed that the careless use of reverse inference is a problematic practice, the current view of reverse inference is to the author's opinion overly pessimistic. The present manuscript provides a revised formulation of reverse inference that includes an additional conditional constraint that has been previously acknowledged, but so far not implemented: the task-setting. This revised formulation I.) reveals that reverse inference can have high predictive power (as demonstrated by an example estimation) and II.) allows an estimation of reverse inference on the basis of meta-analyses instead of large-scale databases. It is concluded that reverse inference cannot be disregarded as a fallacy per se. Rather, the predictive power of reverse inference can even be "decisive"-dependent on the cognitive process of interest, the specific brain region activated, and the task-setting used.