Developmental protein kinase C hyper-activation results in microcephaly and behavioral abnormalities in zebrafish

Orexins/Hypocretins: Gatekeepers of Social Interaction and Motivation

Ever since the discovery of the brain's orexin/hypocretin system, most research was directed toward unveiling its contribution to the normal functioning of individuals. The investigation of reward-seeking behaviors then gained a lot of attention once the distribution of orexinergic neurons was revealed. Here, we discuss findings on the involvement of orexins in social interaction, a natural reward type. While some studies have succeeded in defining the relationship between orexin and social interaction, the controversy regarding its nature (direct or inverse relation) raises questions about what aspects have been overlooked until now. Upon examining the literature, we identified a research gap concerning conditions influencing the impact of orexins on social behavior expression. In this review, we introduce a number of factors (e.g., stress, orexin's source) that must be considered while studying the role of orexins in social interaction. Furthermore, we refer to published research to investigate the stage at which orexins affect social interaction and we highlight the nucleus accumbens (NAc) shell's role in social interaction and other rewarding behaviors. Finally, the underlying orexin molecular pathway influencing social motivation in particular illnesses is proposed. We conclude that orexin's impact on social interaction is multifactorial and depends on specific conditions available at a time.

Protein kinase C beta relieves autism-like behavior in EN2 knockout mice via upregulation of the FTO/PGC-1α/UCP1 axis

Increasing evidence suggests that disruption of neuron activity contributes to the autistic phenotype. Thus, we aimed in this study to explore the role of protein kinase C beta (PKCβ) in the regulation of neuron activity in an autism model. The expression of PKCβ in the microarray data of autism animal models was obtained from the Gene Expression Omnibus database. Then, mice with autism-like behavior were prepared in EN2 knockout (^-/- ) mice. The interaction between PKCβ on fat mass and obesity-associated protein (FTO) as well as between PGC-1α and uncoupling protein 1 (UCP1) were characterized. The effect of FTO on the N⁶ -methyladenosine (m6A) modification level of proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) was assayed. Following transfection of overexpressed PKCβ and/or silenced UCP1, effects of PKCβ and UCP1 in autism-like behaviors in EN2^-/- mice were analyzed. Results showed that PKCβ was downregulated in EN2^-/- mouse brain tissues or neurons. PKCβ promoted the expression and stability of FTO, which downregulated the m6A modification level of PGC-1α to promote its expression. Moreover, PGC-1α positively targeted the expression of UCP1. PKCβ knockdown enhanced sociability and spatial exploration ability, and reduced neuron apoptosis in EN2^-/- mouse models of autism, which was reversed by UCP1 overexpression. Collectively, PKCβ overexpression leads to activation of the FTO/m6A/PGC-1α/UCP1 axis, thus inhibiting neuron apoptosis and providing neuroprotection in mice with autism-like behavior.

Experimental Models to Study Autism Spectrum Disorders: hiPSCs, Rodents and Zebrafish

Autism Spectrum Disorders (ASD) affect around 1.5% of the global population, which manifest alterations in communication and socialization, as well as repetitive behaviors or restricted interests. ASD is a complex disorder with known environmental and genetic contributors; however, ASD etiology is far from being clear. In the past decades, many efforts have been put into developing new models to study ASD, both in vitro and in vivo. These models have a lot of potential to help to validate some of the previously associated risk factors to the development of the disorder, and to test new potential therapies that help to alleviate ASD symptoms. The present review is focused on the recent advances towards the generation of models for the study of ASD, which would be a useful tool to decipher the bases of the disorder, as well as to conduct drug screenings that hopefully lead to the identification of useful compounds to help patients deal with the symptoms of ASD.

RRP7A links primary microcephaly to dysfunction of ribosome biogenesis, resorption of primary cilia, and neurogenesis

Primary microcephaly (MCPH) is characterized by reduced brain size and intellectual disability. The exact pathophysiological mechanism underlying MCPH remains to be elucidated, but dysfunction of neuronal progenitors in the developing neocortex plays a major role. We identified a homozygous missense mutation (p.W155C) in Ribosomal RNA Processing 7 Homolog A, RRP7A, segregating with MCPH in a consanguineous family with 10 affected individuals. RRP7A is highly expressed in neural stem cells in developing human forebrain, and targeted mutation of Rrp7a leads to defects in neurogenesis and proliferation in a mouse stem cell model. RRP7A localizes to centrosomes, cilia and nucleoli, and patient-derived fibroblasts display defects in ribosomal RNA processing, primary cilia resorption, and cell cycle progression. Analysis of zebrafish embryos supported that the patient mutation in RRP7A causes reduced brain size, impaired neurogenesis and cell proliferation, and defective ribosomal RNA processing. These findings provide novel insight into human brain development and MCPH.

The RRP7A a gene is involved in ribosome biogenesis. Here the authors report a homozygous missense mutation segregating with primary microcephaly, and show that this occurs via functional defects in both nucleoli and primary cilia disrupting cell proliferation and neurogenesis.