An aetiological Foxp2 mutation causes aberrant striatal activity and alters plasticity during skill learning.

Mutations in the human FOXP2 gene cause impaired speech development and linguistic deficits, which have been best characterised in a large pedigree called the KE family. The encoded protein is highly conserved in many vertebrates and is expressed in homologous brain regions required for sensorimotor integration and motor-skill learning, in particular corticostriatal circuits. Independent studies in multiple species suggest that the striatum is a key site of FOXP2 action. Here, we used in vivo recordings in awake-behaving mice to investigate the effects of the KE-family mutation on the function of striatal circuits during motor-skill learning. We uncovered abnormally high ongoing striatal activity in mice carrying an identical mutation to that of the KE family. Furthermore, there were dramatic alterations in striatal plasticity during the acquisition of a motor skill, with most neurons in mutants showing negative modulation of firing rate, starkly contrasting with the predominantly positive modulation seen in control animals. We also observed striking changes in the temporal coordination of striatal firing during motor-skill learning in mutants. Our results indicate that FOXP2 is critical for the function of striatal circuits in vivo, which are important not only for speech but also for other striatal-dependent skills.

Negative regulation of neural stem/progenitor cell proliferation by the Pten tumor suppressor gene in vivo.

The mechanisms controlling neural stem cell proliferation are poorly understood. Here we demonstrate that the PTEN tumor suppressor plays an important role in regulating neural stem/progenitor cells in vivo and in vitro. Mice lacking PTEN exhibited enlarged, histoarchitecturally abnormal brains, which resulted from increased cell proliferation, decreased cell death, and enlarged cell size. Neurosphere cultures revealed a greater proliferation capacity for tripotent Pten-/- central nervous system stem/progenitor cells, which can be attributed, at least in part, to a shortened cell cycle. However, cell fate commitments of the progenitors were largely undisturbed. Our results suggest that PTEN negatively regulates neural stem cell proliferation.

Mice carrying a humanized Foxp2 knock-in allele show region-specific shifts of striatal Foxp2 expression levels.

Genetic and clinical studies of speech and language disorders are providing starting points to unravel underlying neurobiological mechanisms. The gene encoding the transcription factor FOXP2 has been the first example of a gene involved in the development and evolution of this human-specific trait. A number of autosomal-dominant FOXP2 mutations are associated with developmental speech and language deficits indicating that gene dosage plays an important role in the disorder. Comparative genomics studies suggest that two human-specific amino acid substitutions in FOXP2 might have been positively selected during human evolution. A knock-in mouse model carrying these two amino acid changes in the endogenous mouse Foxp2 gene (Foxp2hum/hum) shows profound changes in striatum-dependent behaviour and neurophysiology, supporting a functional role for these changes. However, how this affects Foxp2 expression patterns in different striatal regions and compartments has not been assessed. Here, we characterized Foxp2 protein expression patterns in adult striatal tissue in Foxp2hum/hum mice. Consistent with prior reports in wildtype mice, we find that striatal neurons in Foxp2hum/hum mice and wildtype littermates express Foxp2 in a range from low to high levels. However, we observe a shift towards more cells with higher Foxp2 expression levels in Foxp2hum/hum mice, significantly depending on the striatal region and the compartment. As potential behavioural readout of these shifts in Foxp2 levels across striatal neurons, we employed a morphine sensitization assay. While we did not detect differences in morphine-induced hyperlocomotion during acute treatment, there was an attenuated hyperlocomotion plateau during sensitization in Foxp2hum/hum mice. Taken together, these results suggest that the humanized Foxp2 allele in a mouse background is associated with a shift in striatal Foxp2 protein expression pattern.

The structure of innate vocalizations in Foxp2-deficient mouse pups.

Heterozygous mutations of the human FOXP2 gene are implicated in a severe speech and language disorder. Aetiological mutations of murine Foxp2 yield abnormal synaptic plasticity and impaired motor-skill learning in mutant mice, while knockdown of the avian orthologue in songbirds interferes with auditory-guided vocal learning. Here, we investigate influences of two distinct Foxp2 point mutations on vocalizations of 4-day-old mouse pups (Mus musculus). The R552H missense mutation is identical to that causing speech and language deficits in a large well-studied human family, while the S321X nonsense mutation represents a null allele that does not produce Foxp2 protein. We ask whether vocalizations, based solely on innate mechanisms of production, are affected by these alternative Foxp2 mutations. Sound recordings were taken in two different situations: isolation and distress, eliciting a range of call types, including broadband vocalizations of varying noise content, ultrasonic whistles and clicks. Sound production rates and several acoustic parameters showed that, despite absence of functional Foxp2, homozygous mutants could vocalize all types of sounds in a normal temporal pattern, but only at comparably low intensities. We suggest that altered vocal output of these homozygotes may be secondary to developmental delays and somatic weakness. Heterozygous mutants did not differ from wild-types in any of the measures that we studied (R552H ) or in only a few (S321X ), which were in the range of differences routinely observed for different mouse strains. Thus, Foxp2 is not essential for the innate production of emotional vocalizations with largely normal acoustic properties by mouse pups.

LRRTM1 on chromosome 2p12 is a maternally suppressed gene that is associated paternally with handedness and schizophrenia.

Left-right asymmetrical brain function underlies much of human cognition, behavior and emotion. Abnormalities of cerebral asymmetry are associated with schizophrenia and other neuropsychiatric disorders. The molecular, developmental and evolutionary origins of human brain asymmetry are unknown. We found significant association of a haplotype upstream of the gene LRRTM1 (Leucine-rich repeat transmembrane neuronal 1) with a quantitative measure of human handedness in a set of dyslexic siblings, when the haplotype was inherited paternally (P=0.00002). While we were unable to find this effect in an epidemiological set of twin-based sibships, we did find that the same haplotype is overtransmitted paternally to individuals with schizophrenia/schizoaffective disorder in a study of 1002 affected families (P=0.0014). We then found direct confirmatory evidence that LRRTM1 is an imprinted gene in humans that shows a variable pattern of maternal downregulation. We also showed that LRRTM1 is expressed during the development of specific forebrain structures, and thus could influence neuronal differentiation and connectivity. This is the first potential genetic influence on human handedness to be identified, and the first putative genetic effect on variability in human brain asymmetry. LRRTM1 is a candidate gene for involvement in several common neurodevelopmental disorders, and may have played a role in human cognitive and behavioral evolution.

[Implant size and soft tissue behavior in different facial areas. An experimental study]. / Implantatgrösse und Weichteilverhalten an verschiedenen Gesichtsregionen. Eine experimentelle Studie.

In order to predict augmentation results reliably in facial contour improvement, the thickness of the soft tissue and its deformation was reliably determined in 15 fresh cadavers after subperiostal insertion of self-made silicon implants ranging from 2 to 14 mm in diameter. Direct percutaneous measurements were made on the forehead, dorsum of the nose, malar bone, angle of the mandible, and the chin. Each region was subdivided into three zones. In 50 normal-weight subjects, the thickness of the facial soft tissues was also recorded sonographically with the aforementioned measuring points. The soft-tissue diameters decreased in the following order: malar region (8-14 mm), chin angle of the mandible-forehead dorsum of the nose (1-2 mm). In the malar region, the angle of the mandible and chin, there was a step-wise, significant compression of the soft tissues, which reduced the augmentation effect by up to 20% after subperiostal insertion of implants of up to 8 mm in diameter. Larger implant diameters (10-14 mm) no longer increased the compression effect. The thickness of the facial soft tissues at the implantation site was of decisive importance, since it defines the degree of buffer capacity. Preoperative sonographic measurement of soft-tissue thickness could therefore help to predict the augmentation result better; in the presence of a thick soft-tissue mantle (from 10 mm), we recommend selecting a 20% greater implant thickness in order to equalize the buffer effect and to avoid subcontouring.