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Metabolism has recently emerged as a major target of genes implicated in the evolutionary expansion of human neocortex. One such gene is the human-specific gene ARHGAP11B . During human neocortex development, ARHGAP11B increases the abundance of basal radial glia, key progenitors for neocortex expansion, by stimulating glutaminolysis (glutamine-to-glutamate-to-alpha-ketoglutarate) in mitochondria. Here we show that the ape-specific protein GLUD2 (glutamate dehydrogenase 2), which also operates in mitochondria and converts glutamate-to-αKG, enhances ARHGAP11B’s ability to increase basal radial glia abundance. ARHGAP11B + GLUD2 double-transgenic bRG show increased production of aspartate, a metabolite essential for cell proliferation, from glutamate via alpha-ketoglutarate and the TCA cycle. Hence, during human evolution, a human-specific gene exploited the existence of another gene that emerged during ape evolution, to increase, via concerted changes in metabolism, progenitor abundance and neocortex size. Cell metabolism has emerged as a major factor implicated in human brain evolution. Here, the authors show that an ape-specific enzyme enhances the ability of a human-specific enzyme to increase glutaminolysis and therefore expand the size of the human neocortex.

Embryo transfer (ET) is a decisive step in the in vitro fertilization process. In most cases, the embryo is transferred to the uterus after several days of in vitro culture. Although studies have identified the beneficial effects of ET on proper embryo development in the earlier stages, this strategy is compromised by the necessity to transfer early embryos (zygotes) back to the fallopian tube instead of the uterus, which requires a more invasive, laparoscopic procedure, termed zygote intrafallopian transfer (ZIFT). Magnetic micromotors offer the possibility to mitigate such surgical interventions, as they have the potential to transport and deliver cellular cargo such as zygotes through the uterus and fallopian tube noninvasively, actuated by an externally applied rotating magnetic field. This study presents the capture, transport, and release of bovine and murine zygotes using two types of magnetic micropropellers, helix and spiral. Although helices represent an established micromotor architecture, spirals surpass them in terms of motion performance and with their ability to reliably capture and secure the cargo during both motion and transfer between different environments. Herein, this is demonstrated with murine oocytes/zygotes as the cargo; this is the first step toward the application of noninvasive, magnetic micromotor‐assisted ZIFT. Spiral micropropellers that capture, transport, and release oocytes and zygotes, actuated solely by a rotating magnetic field, and are transferred between different environments without losing the cargo, are presented. The propulsion and transport performance of the innovative propellers and their advantages over established helical micromotors are demonstrated regarding applicability in a noninvasive alternative concept to laparoscopy, zygote transfer by micromotors.

Michael Breckwoldt and colleagues have developed a new approach to follow the mitochondrial redox potential of neurons with high spatio-temporal resolution. This multiparametric in vivo imaging approach is based on the transgenic expression of a biosensor for glutathione redox potential in neuronal mitochondria, with utility demonstrated in mouse models of amyotrophic lateral sclerosis and spinal cord injury. It should prove useful for studying mitochondrial pathology in neurological disease models. Mitochondrial redox signals have a central role in neuronal physiology and disease. Here we describe a new optical approach to measure fast redox signals with single-organelle resolution in living mice that express genetically encoded redox biosensors in their neuronal mitochondria. Moreover, we demonstrate how parallel measurements with several biosensors can integrate these redox signals into a comprehensive characterization of mitochondrial function. This approach revealed that axonal mitochondria undergo spontaneous 'contractions' that are accompanied by reversible redox changes. These contractions are amplified by neuronal activity and acute or chronic neuronal insults. Multiparametric imaging reveals that contractions constitute respiratory chain–dependent episodes of depolarization coinciding with matrix alkalinization, followed by uncoupling. In contrast, permanent mitochondrial damage after spinal cord injury depends on calcium influx and mitochondrial permeability transition. Thus, our approach allows us to identify heterogeneity among physiological and pathological redox signals, correlate such signals to functional and structural organelle dynamics and dissect the underlying mechanisms.

Regulatory mechanisms controlling the pool size of spleen dendritic cells (DC) remain incompletely understood. DCs are continuously replenished from hematopoietic stem cells, and FLT3-mediated signals cell-intrinsically regulate homeostatic expansion of spleen DCs. Here we show that combining FLT3 and CSF1R-deficiencies results in specific and complete abrogation of spleen DCs in vivo. Spatiotemporally controlled CSF1R depletion reveals a cell-extrinsic and non-hematopoietic mechanism for DC pool size regulation. Lack of CSF1R-mediated signals impedes the differentiation of spleen macrophages of embryonic origin, and the resulted macrophage depletion during development or in adult mice results in loss of DCs. Moreover, embryo-derived macrophages are important for the physiologic regeneration of DC after activation-induced depletion in situ. In summary, we show that the differentiation of DC and their regeneration relies on ontogenetically distinct spleen macrophages, thereby providing a novel regulatory principle that may also be important for the differentiation of other hematopoietic cell types. Dendritic cells (DC) are important regulators of both innate and adaptive immunity, but how the DC pool is homeostatically maintained in vivo is unclear. Here the authors show that combined deficiency of FLT3 and CSF1R impedes the differentiation of spleen macrophages of embryonic origin that are required for DC homeostasis.

The synaptonemal complex (SC) is a proteinaceous, meiosis-specific structure that is highly conserved in evolution. During meiosis, the SC mediates synapsis of homologous chromosomes. It is essential for proper recombination and segregation of homologous chromosomes, and therefore for genome haploidization. Mutations in human SC genes can cause infertility. In order to gain a better understanding of the process of SC assembly in a model system that would be relevant for humans, we are investigating meiosis in mice. Here, we report on a newly identified component of the murine SC, which we named SYCE3. SYCE3 is strongly conserved among mammals and localizes to the central element (CE) of the SC. By generating a Syce3 knockout mouse, we found that SYCE3 is required for fertility in both sexes. Loss of SYCE3 blocks synapsis initiation and results in meiotic arrest. In the absence of SYCE3, initiation of meiotic recombination appears to be normal, but its progression is severely impaired resulting in complete absence of MLH1 foci, which are presumed markers of crossovers in wild-type meiocytes. In the process of SC assembly, SYCE3 is required downstream of transverse filament protein SYCP1, but upstream of the other previously described CE-specific proteins. We conclude that SYCE3 enables chromosome loading of the other CE-specific proteins, which in turn would promote synapsis between homologous chromosomes.

Site-specific recombinases (SSR) are utilized as important genome engineering tools to precisely modify the genome of mice and other model organisms. Reporter mice that mark cells that at any given time had expressed the enzyme are frequently used for lineage tracing and to characterize newly generated mice expressing a recombinase from a chosen promoter. With increasing sophistication of genome alteration strategies, the demand for novel SSR systems that efficiently and specifically recombine their targets is rising and several SSR-systems are now used in combination to address complex biological questions in vivo . Generation of reporter mice for each one of these recombinases is cumbersome and increases the number of mouse lines that need to be maintained in animal facilities. Here we present a mu lti-reporter mouse line for loci-of-recombination ( X ) (MuX) that streamlines the characterization of mice expressing prominent recombinases. MuX mice constitutively express nuclear green fluorescent protein after recombination by either Cre, Flp, Dre or Vika recombinase, rationalizing the number of animal lines that need to be maintained. We also pioneer the use of the Vika/vox system in mice, illustrating its high efficacy and specificity, thereby facilitating future designs of sophisticated recombinase-based in vivo genome engineering strategies.

The FOXP2 gene is required for normal development of speech and language. By isolating and sequencing FOXP2 genomic DNA fragments from a 49,000-year-old Iberian Neandertal and 50 present-day humans, we have identified substitutions in the gene shared by all or nearly all present-day humans but absent or polymorphic in Neandertals. One such substitution is localized in intron 8 and affects a binding site for the transcription factor POU3F2, which is highly conserved among vertebrates. We find that the derived allele of this site is less efficient than the ancestral allele in activating transcription from a reporter construct. The derived allele also binds less POU3F2 dimers than POU3F2 monomers compared with the ancestral allele. Because the substitution in the POU3F2 binding site is likely to alter the regulation of FOXP2 expression, and because it is localized in a region of the gene associated with a previously described signal of positive selection, it is a plausible candidate for having caused a recent selective sweep in the FOXP2 gene.

Background Systemic inflammatory response syndrome (SIRS) is a frequent critical condition in clinical patients marked by dysregulated immune activation and high mortality. Early initiation of appropriate interventions are important for patient outcome, but molecular markers for diagnosis are not SIRS-specific. Methods We performed hematological analyses and health-status assessments on a transgenic disease mouse model that recapitulates elevated epidermal levels of the metalloprotease meprin α (K5Mα) reported in inflammatory skin diseases. In a cohort of intensive care patients that either developed SIRS ( n  = 19) or not ( n  = 29), we measured parameters associated with systemic inflammation and organ function as well as serum meprin α levels. Results K5Mα mice developed fatal SIRS characterized by hypothermia, severe weight loss, hypochromic microcytic anemia, neutrophilic leukocytosis and cytokine release syndrome. Serum concentrations of meprin α correlated with disease progression in K5Mα mice. We detected high meprin α levels in the serum of intensive care patients who developed SIRS but in none of the patients who did not develop SIRS. Serum meprin α levels significantly correlated with clinical parameters like C-reactive protein, procalcitonin and white blood cell count, but unlike all other measured inflammatory parameters allowed a clear identification of SIRS patients. Conclusions We propose serum meprin α levels as a potential biomarker for SIRS. However, we would like to emphasize that due to our limited cohort size subsequent larger-scale, multicentered studies are warranted to validate our findings and potentially provide more detailed insight into whether there is an association between elevated meprin α serum levels and specific causes of SIRS or dysfunction of particular organ systems. Graphical Abstract

T-cell receptor (TCR) signal strength determines selection and lineage fate at the CD4 ⁺CD8 ⁺ double-positive stage of intrathymic T-cell development. Members of the miR-181 family constitute the most abundantly expressed microRNA at this stage of T-cell development. Here we show that deletion of miR-181a/b-1 reduced the responsiveness of double-positive thymocytes to TCR signals and virtually abrogated early invariant natural killer T (iNKT) cell development, resulting in a dramatic reduction in iNKT cell numbers in thymus as well as in the periphery. Increased concentrations of agonist ligand rescued iNKT cell development in miR-181a/b-1 ⁻/⁻ mice. Our results define a critical role of miR-181a/b-1 in early iNKT cell development and show that miR-181a/b-1 sets a TCR signaling threshold for agonist selection.

Transcriptional complexes can polymerize and bind adjacent binding sites. Vinkemeier and colleagues show that STAT1 cooperativity is required downstream of type 2 interferonsignaling but not for type 1 interferon–induced immune responses. STAT1 is an indispensable component of a heterotrimer (ISGF3) and a STAT1 homodimer (GAF) that function as transcription regulators in type 1 and type 2 interferon signaling, respectively. To investigate the importance of STAT1-cooperative DNA binding, we generated gene-targeted mice expressing cooperativity-deficient STAT1 with alanine substituted for Phe77. Neither ISGF3 nor GAF bound DNA cooperatively in the STAT1F77A mouse strain, but type 1 and type 2 interferon responses were affected differently. Type 2 interferon–mediated transcription and antibacterial immunity essentially disappeared owing to defective promoter recruitment of GAF. In contrast, STAT1 recruitment to ISGF3 binding sites and type 1 interferon–dependent responses, including antiviral protection, remained intact. We conclude that STAT1 cooperativity is essential for its biological activity and underlies the cellular responses to type 2, but not type 1 interferon.