A humanized version of Foxp2 does not affect ultrasonic vocalization in adult mice

A humanized version of Foxp2 affects ultrasonic vocalization in adult female and male mice

The transcription factor FoxP2 is involved in setting up the neuronal circuitry for vocal learning in mammals and birds and is thought to have played a special role in the evolution of human speech and language. It has been shown that an allele with a humanized version of the murine Foxp2 gene changes the ultrasonic vocalization of mouse pups compared to pups of the wild-type inbred strain. Here we tested if this humanized allele would also affect the ultrasonic vocalization of adult female and male mice. In a previous study, in which only male vocalization was considered and the mice were recorded under a restricted spatial and temporal regime, no difference in adult vocalization between genotypes was found. Here, we use a different test paradigm in which both female and male vocalizations are recorded in extended social contact. We found differences in temporal, spectral and syntactical parameters between the genotypes in both sexes, and between sexes. Mice carrying the humanized Foxp2 allele were using higher frequencies and more complex syllable types than mice of the corresponding wildtype inbred strain. Our results support the notion that the humanized Foxp2 allele has a differential effect on mouse ultrasonic vocalization. As mice carrying the humanized version of the Foxp2 gene show effects opposite to those of mice carrying disrupted or mutated alleles of this gene, we conclude that this mouse line represents an important model for the study of human speech and language evolution.

Genetic Mechanisms Underlying Cortical Evolution in Mammals

The remarkable sensory, motor, and cognitive abilities of mammals mainly depend on the neocortex. Thus, the emergence of the six-layered neocortex in reptilian ancestors of mammals constitutes a fundamental evolutionary landmark. The mammalian cortex is a columnar epithelium of densely packed cells organized in layers where neurons are generated mainly in the subventricular zone in successive waves throughout development. Newborn cells move away from their site of neurogenesis through radial or tangential migration to reach their specific destination closer to the pial surface of the same or different cortical area. Interestingly, the genetic programs underlying neocortical development diversified in different mammalian lineages. In this work, I will review several recent studies that characterized how distinct transcriptional programs relate to the development and functional organization of the neocortex across diverse mammalian lineages. In some primates such as the anthropoids, the neocortex became extremely large, especially in humans where it comprises around 80% of the brain. It has been hypothesized that the massive expansion of the cortical surface and elaboration of its connections in the human lineage, has enabled our unique cognitive capacities including abstract thinking, long-term planning, verbal language and elaborated tool making capabilities. I will also analyze the lineage-specific genetic changes that could have led to the modification of key neurodevelopmental events, including regulation of cell number, neuronal migration, and differentiation into specific phenotypes, in order to shed light on the evolutionary mechanisms underlying the diversity of mammalian brains including the human brain.

Impaired Cortical Cytoarchitecture and Reduced Excitability of Deep-Layer Neurons in the Offspring of Diabetic Rats

Maternal diabetes has been related to low verbal task scores, impaired fine and gross motor skills, and poor performance in graphic and visuospatial tasks during childhood. The primary motor cortex is important for controlling motor functions, and embryos exposed to high glucose show changes in cell proliferation, migration, and differentiation during corticogenesis. However, the existing studies do not discriminate between embryos with or without neural tube defects, making it difficult to conclude whether the reported changes are related to neural tube defects or other anomalies. Furthermore, postnatal effects on central nervous system cytoarchitecture and function have been scarcely addressed. Through molecular, biochemical, morphological, and electrophysiological approaches, we provide evidence of impaired primary motor cerebral cortex lamination and neuronal function in pups from diabetic rats, showing an altered distribution of SATB2, FOXP2, and TBR1, impaired cell migration and polarity, and decreased excitability of deep-layer cortical neurons, suggesting abnormalities in cortico-cortical and extra-cortical innervation. Furthermore, phase-plot analysis of action potentials suggests changes in the activity of potassium channels. These results indicate that high-glucose insult during development promotes complex changes in migration, neurogenesis, cell polarity establishment, and dendritic arborization, which in turn lead to reduced excitability of deep-layer cortical neurons.

Studying human and nonhuman primate evolutionary biology with powerful in vitro and in vivo functional genomics tools

In recent years, tools for functional genomic studies have become increasingly feasible for use by evolutionary anthropologists. In this review, we provide brief overviews of several exciting in vitro techniques that can be paired with "-omics" approaches (e.g., genomics, epigenomics, transcriptomics, proteomics, and metabolomics) for potentially powerful evolutionary insights. These in vitro techniques include ancestral protein resurrection, cell line experiments using primary, immortalized, and induced pluripotent stem cells, and CRISPR-Cas9 genetic manipulation. We also discuss how several of these methods can be used in vivo, for transgenic organism studies of human and nonhuman primate evolution. Throughout this review, we highlight example studies in which these approaches have already been used to inform our understanding of the evolutionary biology of modern and archaic humans and other primates while simultaneously identifying future opportunities for anthropologists to use this toolkit to help answer additional outstanding questions in evolutionary anthropology.

Courtship vocalizations: A potential biomarker of adult exposure to endocrine disrupting compounds?

In rodents, male courtship is stimulated by pheromones emitted by the sexually receptive female. In response, the male produces ultrasonic vocalizations, which appear to play a role in female attraction and facilitate copulation. The present review summarizes the main findings on courtship vocalizations and their tight regulation by sex steroid hormones. It describes studies that address the effects of exposure to endocrine disrupting compounds (EDC) on ultrasound production, as changes in hormone levels or their signaling pathways may interfere with the emission of ultrasonic vocalizations. It also discusses the potential use of this behavior as a noninvasive biomarker of adult exposure to EDC.

Evolutionary Changes in Transcriptional Regulation: Insights into Human Behavior and Neurological Conditions

Understanding the biological basis for human-specific cognitive traits presents both immense challenges and unique opportunities. Although the question of what makes us human has been investigated with several different methods, the rise of comparative genomics, epigenomics, and medical genetics has provided tools to help narrow down and functionally assess the regions of the genome that seem evolutionarily relevant along the human lineage. In this review, we focus on how medical genetic cases have provided compelling functional evidence for genes and loci that appear to have interesting evolutionary signatures in humans. Furthermore, we examine a special class of noncoding regions, human accelerated regions (HARs), that have been suggested to show human-lineage-specific divergence, and how the use of clinical and population data has started to provide functional information to examine these regions. Finally, we outline methods that provide new insights into functional noncoding sequences in evolution.

Altered social behavior in mice carrying a cortical Foxp2 deletion

Genetic disruptions of the forkhead box transcription factor FOXP2 in humans cause an autosomal-dominant speech and language disorder. While FOXP2 expression pattern are highly conserved, its role in specific brain areas for mammalian social behaviors remains largely unknown. Here we studied mice carrying a homozygous cortical Foxp2 deletion. The postnatal development and gross morphological architecture of mutant mice was indistinguishable from wildtype (WT) littermates. Unbiased behavioral profiling of adult mice revealed abnormalities in approach behavior towards conspecifics as well as in the reciprocal responses of WT interaction partners. Furthermore mutant mice showed alterations in acoustical parameters of ultrasonic vocalizations, which also differed in function of the social context. Cell type-specific gene expression profiling of cortical pyramidal neurons revealed aberrant regulation of genes involved in social behavior. In particular Foxp2 mutants showed the downregulation of Mint2 (Apba2), a gene involved in approach behavior in mice and autism spectrum disorder in humans. Taken together these data demonstrate that cortical Foxp2 is required for normal social behaviors in mice.

Human Models Are Needed for Studying Human Neurodevelopmental Disorders

The analysis of animal models of neurological disease has been instrumental in furthering our understanding of neurodevelopment and brain diseases. However, animal models are limited in revealing some of the most fundamental aspects of development, genetics, pathology, and disease mechanisms that are unique to humans. These shortcomings are exaggerated in disorders that affect the brain, where the most significant differences between humans and animal models exist, and could underscore failures in targeted therapeutic interventions in affected individuals. Human pluripotent stem cells have emerged as a much-needed model system for investigating human-specific biology and disease mechanisms. However, questions remain regarding whether these cell-culture-based models are sufficient or even necessary. In this review, we summarize human-specific features of neurodevelopment and the most common neurodevelopmental disorders, present discrepancies between animal models and human diseases, demonstrate how human stem cell models can provide meaningful information, and discuss the challenges that exist in our pursuit to understand distinctively human aspects of neurodevelopment and brain disease. This information argues for a more thoughtful approach to disease modeling through consideration of the valuable features and limitations of each model system, be they human or animal, to mimic disease characteristics.

The Molecular Basis of Human Brain Evolution

Humans are a remarkable species, especially because of the remarkable properties of their brain. Since the split from the chimpanzee lineage, the human brain has increased three-fold in size and has acquired abilities for vocal learning, language and intense cooperation. To better understand the molecular basis of these changes is of great biological and biomedical interest. However, all the about 16 million fixed genetic changes that occurred during human evolution are fully correlated with all molecular, cellular, anatomical and behavioral changes that occurred during this time. Hence, as humans and chimpanzees cannot be crossed or genetically manipulated, no direct evidence for linking particular genetic and molecular changes to human brain evolution can be obtained. Here, I sketch a framework how indirect evidence can be obtained and review findings related to the molecular basis of human cognition, vocal learning and brain size. In particular, I discuss how a comprehensive comparative approach, leveraging cellular systems and genomic technologies, could inform the evolution of our brain in the future.

Enhancing our brains: Genomic mechanisms underlying cortical evolution

Our most distinguishing higher cognitive functions are controlled by the cerebral cortex. Comparative studies detail abundant anatomical and cellular features unique to the human developing and adult neocortex. Emerging genomic studies have further defined vast differences distinguishing developing human neocortices from related primates. These human-specific changes can affect gene function and/or expression, and result from structural variations such as chromosomal deletions and duplications, or from point mutations in coding and noncoding regulatory regions. Here, we review this rapidly growing field which aims to identify and characterize genetic loci unique to the human cerebral cortex. We catalog known human-specific genomic changes distinct from other primates, including those whose function has been interrogated in animal models. We also discuss how new model systems and technologies such as single cell RNA sequencing, primate iPSCs, and gene editing, are enabling the field to gain unprecedented resolution into function of these human-specific changes. Some neurological disorders are thought to uniquely present in humans, thus reinforcing the need to comprehensively understand human-specific gene expression in the developing brain.

Evolution of the Human Nervous System Function, Structure, and Development

The nervous system-in particular, the brain and its cognitive abilities-is among humans' most distinctive and impressive attributes. How the nervous system has changed in the human lineage and how it differs from that of closely related primates is not well understood. Here, we consider recent comparative analyses of extant species that are uncovering new evidence for evolutionary changes in the size and the number of neurons in the human nervous system, as well as the cellular and molecular reorganization of its neural circuits. We also discuss the developmental mechanisms and underlying genetic and molecular changes that generate these structural and functional differences. As relevant new information and tools materialize at an unprecedented pace, the field is now ripe for systematic and functionally relevant studies of the development and evolution of human nervous system specializations.

Prenatal stress changes courtship vocalizations and bone mineral density in mice

Stress during the prenatal period has various effects on social and sexual behavior in both human and animal offspring. The present study examines the effects of chronic restraint stress in the second vs third trimester in pregnancy and glucocorticoid receptor (GR) heterozygous mutation on C57BL/6N male offspring's vocal courtship behavior in adulthood by applying a novel analyzing method. Finally, corticosterone and testosterone levels as well as bone mineral density were measured. Prenatal stress in the third, but not in the second trimester caused a significant qualitative change in males' courtship vocalizations, independent of their GR genotype. Bone mineral density was decreased also by prenatal stress exclusively in the third trimester in GR mutant and wildtype mice and - in contrast to corticosterone and testosterone - highly correlated with courtship vocalizations. In Gr^+/- males corticosterone serum levels were significantly increased in animals that had experienced prenatal stress in the third trimester. Testosterone serum levels were overall increased in Gr^+/- males in comparison to wildtypes as a tendency - whereas prenatal stress had no influence. Prenatal stress alters adult males' courtship vocalizations exclusively when applied in the third trimester, with closely related changes in bone mineral density. Bone mineral density seems to reflect best the complex neuroendocrine mechanisms underlying the production of courtship vocalizations. Besides, we demonstrated for the first time elevated basal corticosterone levels in Gr^+/- males after prenatal stress which suggests that the Gr^+/- mouse model of depression might also serve as a model of prenatal stress in male offspring.

Recording Mouse Ultrasonic Vocalizations to Evaluate Social Communication

Mice emit ultrasonic vocalizations in different contexts throughout development and in adulthood. These vocal signals are now currently used as proxies for modeling the genetic bases of vocal communication deficits. Characterizing the vocal behavior of mouse models carrying mutations in genes associated with neuropsychiatric disorders such as autism spectrum disorders will help to understand the mechanisms leading to social communication deficits. We provide here protocols to reliably elicit ultrasonic vocalizations in pups and in adult mice. This standardization will help reduce inter-study variability due to the experimental settings. Pup isolation calls are recorded throughout development from individual pups isolated from dam and littermates. In adulthood, vocalizations are recorded during same-sex interactions (without a sexual component) by exposing socially motivated males or females to an unknown same-sex conspecific. We also provide a protocol to record vocalizations from adult males exposed to an estrus female. In this context, there is a sexual component in the interaction. These protocols are established to elicit a large amount of ultrasonic vocalizations in laboratory mice. However, we point out the important inter-individual variability in the vocal behavior of mice, which should be taken into account by recording a minimal number of individuals (at least 12 in each condition). These recordings of ultrasonic vocalizations are used to evaluate the call rate, the vocal repertoire and the acoustic structure of the calls. Data are combined with the analysis of synchronous video recordings to provide a more complete view on social communication in mice. These protocols are used to characterize the vocal communication deficits in mice lacking ProSAP1/Shank2, a gene associated with autism spectrum disorders. More ultrasonic vocalizations recordings can also be found on the mouseTube database, developed to favor the exchange of such data.

A Mutation Associated with Stuttering Alters Mouse Pup Ultrasonic Vocalizations

A promising approach to understanding the mechanistic basis of speech is to study disorders that affect speech without compromising other cognitive or motor functions. Stuttering, also known as stammering, has been linked to mutations in the lysosomal enzyme-targeting pathway, but how this remarkably specific speech deficit arises from mutations in a family of general "cellular housekeeping" genes is unknown. To address this question, we asked whether a missense mutation associated with human stuttering causes vocal or other abnormalities in mice. We compared vocalizations from mice engineered to carry a mutation in the Gnptab (N-acetylglucosamine-1-phosphotransferase subunits alpha/beta) gene with wild-type littermates. We found significant differences in the vocalizations of pups with the human Gnptab stuttering mutation compared to littermate controls. Specifically, we found that mice with the mutation emitted fewer vocalizations per unit time and had longer pauses between vocalizations and that the entropy of the temporal sequence was significantly reduced. Furthermore, Gnptab missense mice were similar to wild-type mice on an extensive battery of non-vocal behaviors. We then used the same language-agnostic metrics for auditory signal analysis of human speech. We analyzed speech from people who stutter with mutations in this pathway and compared it to control speech and found abnormalities similar to those found in the mouse vocalizations. These data show that mutations in the lysosomal enzyme-targeting pathway produce highly specific effects in mouse pup vocalizations and establish the mouse as an attractive model for studying this disorder.

Knockout of Foxp2 disrupts vocal development in mice

The FOXP2 gene is important for the development of proper speech motor control in humans. However, the role of the gene in general vocal behavior in other mammals, including mice, is unclear. Here, we track the vocal development of Foxp2 heterozygous knockout (Foxp2+/−) mice and their wildtype (WT) littermates from juvenile to adult ages, and observe severe abnormalities in the courtship song of Foxp2+/− mice. In comparison to their WT littermates, Foxp2+/− mice vocalized less, produced shorter syllable sequences, and possessed an abnormal syllable inventory. In addition, Foxp2+/− song also exhibited irregular rhythmic structure, and its development did not follow the consistent trajectories observed in WT vocalizations. These results demonstrate that the Foxp2 gene is critical for normal vocal behavior in juvenile and adult mice, and that Foxp2 mutant mice may provide a tractable model system for the study of the gene’s role in general vocal motor control.

The contribution of ultrasonic vocalizations to mouse courtship

Vocalizations transmit information to social partners, and mice use these signals to exchange information during courtship. Ultrasonic vocalizations from adult males are tightly associated with their interactions with females, and vary as a function of male quality. Work in the last decade has established that the spectrotemporal features of male vocalizations are not learned, but that female attention toward specific vocal features is modified by social experience. Additionally, progress has been made on elucidating how mouse vocalizations are encoded in the auditory system, and on the olfactory circuits that trigger their production. Together these findings provide us with important insights into how vocal communication can contribute to social interactions.

Genomic divergence and brain evolution: How regulatory DNA influences development of the cerebral cortex

The cerebral cortex controls our most distinguishing higher cognitive functions. Human-specific gene expression differences are abundant in the cerebral cortex, yet we have only begun to understand how these variations impact brain function. This review discusses the current evidence linking non-coding regulatory DNA changes, including enhancers, with neocortical evolution. Functional interrogation using animal models reveals converging roles for our genome in key aspects of cortical development including progenitor cell cycle and neuronal signaling. New technologies, including iPS cells and organoids, offer potential alternatives to modeling evolutionary modifications in a relevant species context. Several diseases rooted in the cerebral cortex uniquely manifest in humans compared to other primates, thus highlighting the importance of understanding human brain differences. Future studies of regulatory loci, including those implicated in disease, will collectively help elucidate key cellular and genetic mechanisms underlying our distinguishing cognitive traits.