Abstract:Robust evidence in literature indicates that the morphogenic factor Sonic Hedgehog (Shh) actively orchestrates several aspects of cerebellar development and maturation. During embryogenesis Shh signalling is active in the ventricular germinal zone (VZ) and represents an essential signal for proliferation of VZ-derived progenitors. Later, Purkinje cell (PC)-secreted Shh sustains the amplification of neurogenic niches active during postnatal development: the external granular layer (EGL) and the prospective white matter (PWM) where excitatory granule cells and inhibitory interneurons, respectively, are produced. In addition, Shh signalling acts on Bergmann glia differentiation and during development sustains cerebellar foliation. Here we review the most relevant functions of Shh during cerebellar ontogenesis, underlying the role of this ligand in the development of different cerebellar phenotypes. Keywords: Shh, mitogen, differentiation, cerebellum.Authors declare no conflict of interest. AbstractRobust evidence in literature indicates that the morphogenic factor Sonic Hedgehog (Shh) actively orchestrates several aspects of cerebellar development and maturation. During embryogenesis Shh

Cerebellar reserve refers to the capacity of the cerebellum to compensate for tissue damage or loss of function resulting from many different etiologies. When the inciting event produces acute focal damage (e.g., stroke, trauma), impaired cerebellar function may be compensated for by other cerebellar areas or by extracerebellar structures (i.e., structural cerebellar reserve). In contrast, when pathological changes compromise cerebellar neuronal integrity gradually leading to cell death (e.g., metabolic and immune-mediated cerebellar ataxias, neurodegenerative ataxias), it is possible that the affected area itself can compensate for the slowly evolving cerebellar lesion (i.e., functional cerebellar reserve). Here, we examine cerebellar reserve from the perspective of the three cornerstones of clinical ataxiology: control of ocular movements, coordination of voluntary axial and appendicular movements, and cognitive functions. Current evidence indicates that cerebellar reserve is potentiated by environmental enrichment through the mechanisms of autophagy and synaptogenesis, suggesting that cerebellar reserve is not rigid or fixed, but exhibits plasticity potentiated by experience. These conclusions have therapeutic implications. During the period when cerebellar reserve is preserved, treatments should be directed at stopping disease progression and/or limiting the pathological process. Simultaneously, cerebellar reserve may be potentiated using multiple approaches. Potentiation of cerebellar reserve may lead to compensation and restoration of function in the setting of cerebellar diseases, and also in disorders primarily of the cerebral hemispheres by enhancing cerebellar mechanisms of action. It therefore appears that cerebellar reserve, and the underlying plasticity of cerebellar microcircuitry that enables it, may be of critical neurobiological importance to a wide range of neurological/neuropsychiatric conditions.

Medium spiny neurons (MSNs) are a key population in the basal ganglia network, and their degeneration causes a severe neurodegenerative disorder, Huntington's disease. Understanding how ventral neuroepithelial progenitors differentiate into MSNs is critical for regenerative medicine to develop specific differentiation protocols using human pluripotent stem cells. Studies performed in murine models have identified some transcriptional determinants, including GS Homeobox 2 (Gsx2) and Early B-cell factor 1 (Ebf1). Here, we have generated human embryonic stem (hES) cell lines inducible for these transcription factors, with the aims of (i) studying their biological role in human neural progenitors and (ii) incorporating TF conditional expression in a developmental-based protocol for generating MSNs from hES cells. Using this approach, we found that Gsx2 delays cell-cycle exit and reduces Pax6 expression, whereas Ebf1 promotes neuronal differentiation. Moreover, we found that Gsx2 and Ebf1 combined overexpression in hES cells achieves high yields of MSNs, expressing Darpp32 and Ctip2, in vitro as well in vivo after transplantation. We show that hES-derived striatal progenitors can be transplanted in animal models and can differentiate and integrate into the host, extending fibers over a long distance.he striatum is the largest component of the basal ganglia, it is the hub of converging excitatory connections from the cortex and thalamus, and it originates the direct and indirect pathways, which are distinct basal ganglia circuits involved in motor control (1). In humans, the degeneration of the principal striatal neuronal population, the medium spiny neurons (MSNs), causes a severe neurodegenerative condition, Huntington's disease (HD). A main goal in the field is the study of the mechanisms underlying neuronal specification and degeneration. A large number of studies performed in model organisms, such as the mouse model organism, have provided fundamental insights into brain development, shedding light on genes, signaling pathways, and general rules of brain formation. It is not incidental to point out that obvious speciesspecific differences exist in many aspects between mice and humans (gestation, morphology, and gene expression regulation in time and space). Thus, additional model systems are needed to uncover specific functions of a gene in human development (2, 3). This task is also driven by the need to investigate neurological diseases, such as HD, in a model that more closely resembles human biology.Here, we decided to take advantage of human embryonic stem (hES) cells to develop a model to study the roles of selected transcription factors (TFs) in human striatal development and as a strategy to increase recovery of authentic MSNs for transplantation purposes. During brain development, a set of TFs are expressed in different regions and times and cooperate to establish a dorsalventral and medial-lateral positional identity in progenitor cells and to specify neuronal terminal differentiation. In particular, in...

Sox2 is a transcription factor active in the nervous system, within different cell types, ranging from radial glia neural stem cells to a few specific types of differentiated glia and neurons. Mutations in the human SOX2 transcription factor gene cause various central nervous system (CNS) abnormalities, involving hippocampus and eye defects, as well as ataxia. Conditional Sox2 mutation in mouse, with different Cre transgenes, previously recapitulated different essential features of the disease, such as hippocampus and eye defects. In the cerebellum, Sox2 is active from early embryogenesis in the neural progenitors of the cerebellar primordium; Sox2 expression is maintained, postnatally, within Bergmann glia (BG), a differentiated cell type essential for Purkinje neurons functionality and correct motor control. By performing Sox2 Cre-mediated ablation in the developing and postnatal mouse cerebellum, we reproduced ataxia features. Embryonic Sox2 deletion (with Wnt1Cre) leads to reduction of the cerebellar vermis, known to be commonly related to ataxia, preceded by deregulation of Otx2 and Gbx2, critical regulators of vermis development. Postnatally, BG is progressively disorganized, mislocalized, and reduced in mutants. Sox2 postnatal deletion, specifically induced in glia (with GLAST-CreERT2), reproduces the BG defect, and causes (milder) ataxic features. Our results define a role for Sox2 in cerebellar function and development, and identify a functional requirement for Sox2 within postnatal BG, of potential relevance for ataxia in mouse mutants, and in human patients.

Comorbidity between attention deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) is a frequently reported condition. However, the clinical overlaps between the two disorders are not well characterized. The Child Behavior Checklist (CBCL) is a well-documented measure of emotional and behavioral problems in children and adolescents. The aim of the present study was to evaluate whether CBCL scales were able to detect psychopathological comorbidities as well as emotional and behavioral profiles across three groups of children with ASD, ADHD, and with the co-occurrence of both disorders. The results show that around 30% of participants with ASD exhibited internalizing problems, which was in line with previous findings. Cooccurrence condition showed a clinical intermediate phenotype: relative to ADHD and ASD, youths with co-occurrence of ADHD and ASD phenotype showed respectively lower (p < 0.000) and higher externalizing problems (p < 0.000). No differences emerged in internalizing problems (p > 0.05) across groups. CBCL is a useful measure to study the psychopathological conditions as well as emotional and behavioral profiles associated with ASD, ADHD, and the co-occurrence of ADHD and ASD. The identification of psychopathological and behavioral profiles associated with ASD and ADHD is crucial to perform specific and individualized treatments. Our preliminary findings suggested the existence of an intermediate and independent phenotype between ADHD and ASD that seems to be defined by the externalizing problems. Internalizing problems do not significantly differ between the combined phenotype and the two groups.

Authors' contributionEF and KL performed grafts; EF performed motor training, behavioral, immunohistochemical analyses and stereological counts; MG and EB performed molecular biology and biochemical experiments; EF, FR, KL and AB conceived experiments, EF, KL and AB interpreted data and wrote the manuscript; all the authors reviewed and approved the final manuscript. Highlights• Preventive grafts of Purkinje cells survive despite ongoing host neurodegeneration correlates. Our results demonstrate that, despite a good survival rate and integration of grafted PCs, the adopted grafting protocol could not alleviate the ataxic symptoms in tbl mice. Conversely, preventive motor training increases PCs survival with a moderate positive impact on the motor phenotype.

Despite sleep disturbances are common among youths with Down syndrome (DS), the cognitive and behavioral features associated with sleep problems have not yet been studied extensively. The present study investigated the presence of sleep disturbances in a group of children and adolescents with DS and their cognitive and behavioral correlates. Seventy-one children and adolescents with DS underwent a neuropsychological evaluation, whereas parents completed questionnaires for the screening of the child’s sleep, emotional and behavioral problems. We found no association between sleep disturbances and sex, nonverbal IQ, nor adaptive abilities. However, we found that age was positively associated with disorders in initiating and maintaining sleep (DIMS) and disorders of excessive somnolence (DOES), while body mass index was related with DOES. We also detected a relationship between visual-motor integrations and DIMS, as well as multiple associations between sleep disturbances and psychopathological and behavioral problems, mainly externalizing symptoms. The present study provided a detailed characterization of sleep problems in relation to several features of youths with DS. The proper identification of sleep disturbances profile in the DS population could support the process of clinical evaluation, in particular for psychopathological aspects.

Developmental Dyslexia (DD) is considered a multifactorial deficit. Among the neurocognitive impairments identified in DD, it has been found that memory plays a particularly important role in reading and learning. The present study aims to investigate whether short-term memory (STM) and long-term memory (LTM) deficits could be related to poor reading experience or could be causal factors in DD. To verify that memory deficits in DD did not simply reflect differences in reading experience, 16 children with DD were not only compared to 16 chronological age-matched children (CA) but also to 16 reading level-matched children (RL) in verbal, visual-object, and visual-spatial STM and LTM tasks. Children with DD performed as well as RL, but worse than CA in all STM tasks. Considering LTM, the three groups did not differ in Visual-Object and Visual-Spatial Learning tasks. In the Verbal LTM task, DD recalled significantly fewer words than CA but not RL, while CA and RL showed a similar performance. The present results suggest that when reading experience was equated, children with DD and typical readers did not differ in STM and LTM, especially in the verbal modality, weakening claims that memory has a causal effect in reading impairments.