JIP2 haploinsufficiency contributes to neurodevelopmental abnormalities in human pluripotent stem cell-derived neural progenitors and cortical neurons.

Phelan-McDermid syndrome (also known as 22q13.3 deletion syndrome) is a syndromic form of autism spectrum disorder and currently thought to be caused by heterozygous loss of SHANK3. However, patients most frequently present with large chromosomal deletions affecting several additional genes. We used human pluripotent stem cell technology and genome editing to further dissect molecular and cellular mechanisms. We found that loss of JIP2 (MAPK8IP2) may contribute to a distinct neurodevelopmental phenotype in neural progenitor cells (NPCs) affecting neuronal maturation. This is most likely due to a simultaneous down-regulation of c-Jun N-terminal kinase (JNK) proteins, leading to impaired generation of mature neurons. Furthermore, semaphorin signaling appears to be impaired in patient NPCs and neurons. Pharmacological activation of neuropilin receptor 1 (NRP1) rescued impaired semaphorin pathway activity and JNK expression in patient neurons. Our results suggest a novel disease-specific mechanism involving the JIP/JNK complex and identify NRP1 as a potential new therapeutic target.

Direct lineage conversion of adult mouse liver cells and B lymphocytes to neural stem cells.

Overexpression of transcription factors has been used to directly reprogram somatic cells into a range of other differentiated cell types, including multipotent neural stem cells (NSCs), that can be used to generate neurons and glia. However, the ability to maintain the NSC state independent of the inducing factors and the identity of the somatic donor cells remain two important unresolved issues in transdifferentiation. Here we used transduction of doxycycline-inducible transcription factors to generate stable tripotent NSCs. The induced NSCs (iNSCs) maintained their characteristics in the absence of exogenous factor expression and were transcriptionally, epigenetically, and functionally similar to primary brain-derived NSCs. Importantly, we also generated tripotent iNSCs from multiple adult cell types, including mature liver and B cells. Our results show that self-maintaining proliferative neural cells can be induced from nonectodermal cells by expressing specific combinations of transcription factors.

Detailed analysis of the genetic and epigenetic signatures of iPSC-derived mesodiencephalic dopaminergic neurons.

Induced pluripotent stem cells (iPSCs) hold great promise for in vitro generation of disease-relevant cell types, such as mesodiencephalic dopaminergic (mdDA) neurons involved in Parkinson's disease. Although iPSC-derived midbrain DA neurons have been generated, detailed genetic and epigenetic characterizations of such neurons are lacking. The goal of this study was to examine the authenticity of iPSC-derived DA neurons obtained by established protocols. We FACS purified mdDA (Pitx3 (Gfp/+) ) neurons derived from mouse iPSCs and primary mdDA (Pitx3 (Gfp/+) ) neurons to analyze and compare their genetic and epigenetic features. Although iPSC-derived DA neurons largely adopted characteristics of their in vivo counterparts, relevant deviations in global gene expression and DNA methylation were found. Hypermethylated genes, mainly involved in neurodevelopment and basic neuronal functions, consequently showed reduced expression levels. Such abnormalities should be addressed because they might affect unambiguous long-term functionality and hamper the potential of iPSC-derived DA neurons for in vitro disease modeling or cell-based therapy.

Characterisation of the RNA interference response against the long-wavelength receptor of the honeybee.

Targeted knock-down is the method of choice to advance the study of sensory and brain functions in the honeybee by using molecular techniques. Here we report the results of a first attempt to interfere with the function of a visual receptor, the long-wavelength-sensitive (L-) photoreceptor. RNA interference to inhibit this receptor led to a reduction of the respective mRNA and protein. The interference effect was limited in time and space, and its induction depended on the time of the day most probably because of natural daily variations in opsin levels. The inhibition did not effectively change the physiological properties of the retina. Possible constraints and implications of this method for the study of the bee's visual system are discussed. Overall this study underpins the usefulness and feasibility of RNA interference as manipulation tool in insect brain research.

Induced pluripotent stem cell technology and direct conversion: new possibilities to study and treat Parkinson's disease.

Recent developments in in vitro disease modeling and regenerative medicine have placed induced pluripotent stem cells (iPSCs) in the center of attention as a unique source to study Parkinson's disease. After only 5 years of intensive research, human iPSCs can be generated without viral integration and under xeno-free conditions. This, combined with increasingly sophisticated methods to differentiate iPSCs into functional dopaminergic (DA) neurons, led us to recapitulate the most important findings concerning the use of iPSC technology as a prospective tool to treat symptoms of Parkinson's disease as well as to obtain insight in disease related cell pathogenesis. Moreover, we touch upon some of the latest discoveries in which patient-derived autologous DA neurons come into even more direct reach thanks to a method that allows transdifferentiation of fibroblasts into DA neurons.