Cadherin-7 enhances Sonic Hedgehog signalling by preventing Gli3 repressor formation during neural tube patterning

The role of Shh signalling pathway in central nervous system development and related diseases

Sonic hedgehog (Shh) plays important roles in developmental of vertebrate animal central nervous system (CNS), and Gli is its downstream signal molecule. Shh signalling is essential for pattern formation, cell-fate specification, axon guidance, proliferation, survival and differentiation of neurons in CNS development. The abnormal signalling pathway of Shh leads to the occurrence of many nervous system diseases. The mechanism of Shh signalling is complex and remains incompletely understood. Nevertheless, studies have revealed that Shh signalling pathway is classified into canonical and non-canonical pathways. Here we review the role of the Shh signalling pathway and its impact in CNS development and related diseases. Specifically, we discuss the role of Shh in the spinal cord and brain development, cell differentiation and proliferation in CNS and related diseases such as brain tumour, Parkinson's diseases, epilepsy, autism, depression and traumatic brain injury. We also highlight future directions of research that could help to clarify the mechanisms and consequences of Shh signalling in the process of CNS development and related diseases. SIGNIFICANCE OF THE STUDY: This review summarized the role of Shh signalling pathway in CNS development and related diseases such as brain tumour, Parkinson's diseases, epilepsy, autism, depression and traumatic brain injury. It also presented the author's opinions on the future research direction of Shh signalling pathway.

Cell Adhesion-Mediated Actomyosin Assembly Regulates the Activity of Cubitus Interruptus for Hematopoietic Progenitor Maintenance in Drosophila

The actomyosin network is involved in crucial cellular processes including morphogenesis, cell adhesion, apoptosis, proliferation, differentiation, and collective cell migration in Drosophila, Caenorhabditiselegans, and mammals. Here, we demonstrate that Drosophila larval blood stem-like progenitors require actomyosin activity for their maintenance. Genetic loss of the actomyosin network from progenitors caused a decline in their number. Likewise, the progenitor population increased upon sustained actomyosin activation via phosphorylation by Rho-associated kinase. We show that actomyosin positively regulates larval blood progenitors by controlling the maintenance factor Cubitus interruptus (Ci). Overexpression of the maintenance signal via a constitutively activated construct (ci.HA) failed to sustain Ci-155 in the absence of actomyosin components like Zipper (zip) and Squash (sqh), thus favoring protein kinase A (PKA)-independent regulation of Ci activity. Furthermore, we demonstrate that a change in cortical actomyosin assembly mediated by DE-cadherin modulates Ci activity, thereby determining progenitor status. Thus, loss of cell adhesion and downstream actomyosin activity results in desensitization of the progenitors to Hh signaling, leading to their differentiation. Our data reveal how cell adhesion and the actomyosin network cooperate to influence patterning, morphogenesis, and maintenance of the hematopoietic stem-like progenitor pool in the developing Drosophila hematopoietic organ.