Clinical and molecular spectrum of Wiedemann-Steiner syndrome,an emerging member of the chromatinopathy family

Wiedemann-Steiner syndrome (OMIM #605130) is a rare congenital malformation syndrome characterized by hypertrichosis cubiti associated with short stature; consistent facial features, including long eyelashes, thick or arched eyebrows with a lateral flare, wide nasal bridge, and downslanting and vertically narrow palpebral fissures; mild to moderate intellectual disability; behavioral difficulties; and hypertrichosis on the back. It is caused by heterozygous pathogenic variants in KMT2A. This gene has an established role in histone methylation, which explains the overlap of Wiedemann-Steiner syndrome with other chromatinopathies, a heterogeneous group of syndromic conditions that share a common trigger: The disruption of one of the genes involved in chromatin modification, leading to dysfunction of the epigenetic machinery.     

The ‘space’ of friendship: young children's understandings and expressions of friendship in a reception class

The purpose of this study has been to explore young children's understandings and experiences of friendship as these manifested in children's behaviours, in a reception class setting. Drawing on an evolutionary, ecological framework, friendship is seen as not only the expression and further development of social understandings and cognitive advances; more than that, making and maintaining friends is seen as an evolutionary trait and a ‘drive’ to relate to similarly minded others. Through ‘niche picking’, children select the environments and opportunities that suit them in order to develop their dispositions and individual traits. The research employed a participatory design in order to capture the children's views and experiences. It took place in a reception class setting, where children's everyday experiences were observed and discussed with them. The study identified six themes of analysis and offered some suggestions about creating enabling educational environments that allow the ‘space’ for niche construction.     

Deletion of calcineurin from GFAP-expressing astrocytes impairs excitability of cerebellar and hippocampal neurons through astroglial Na+/K+ ATPase

Astrocytes perform important housekeeping functions in the nervous system including maintenance of adequate neuronal excitability, although the regulatory mechanisms are currently poorly understood. The astrocytic Ca²⁺/calmodulin-activated phosphatase calcineurin (CaN) is implicated in the development of reactive gliosis and neuroinflammation, but its roles, including the control of neuronal excitability, in healthy brain is unknown. We have generated a mouse line with conditional knockout (KO) of CaN B1 (CaNB1) in glial fibrillary acidic protein-expressing astrocytes (a stroglial c alcin eurin KO [ACN-KO]). Here, we report that postnatal and astrocyte-specific ablation of CaNB1 did not alter normal growth and development as well as adult neurogenesis. Yet, we found that specific deletion of astrocytic CaN selectively impairs intrinsic neuronal excitability in hippocampal CA1 pyramidal neurons and cerebellar granule cells (CGCs). This impairment was associated with a decrease in after hyperpolarization in CGC, while passive properties were unchanged, suggesting impairment of K⁺ homeostasis. Indeed, blockade of Na⁺/K⁺-ATPase (NKA) with ouabain phenocopied the electrophysiological alterations observed in ACN-KO CGCs. In addition, NKA activity was significantly lower in cerebellar and hippocampal lysates and in pure astrocytic cultures from ACN-KO mice. While no changes were found in protein levels, NKA activity was inhibited by the specific CaN inhibitor FK506 in both cerebellar lysates and primary astroglia from control mice, suggesting that CaN directly modulates NKA activity and in this manner controls neuronal excitability. In summary, our data provide formal evidence for the notion that astroglia is fundamental for controlling basic neuronal functions and place CaN center-stage as an astrocytic Ca²⁺-sensitive switch.