A comprehensive series of Irx cluster mutants reveals diverse roles in facial cartilage development.

Proper function of the vertebrate skeleton requires the development of distinct articulating embryonic cartilages. Irx transcription factors are arranged in co-regulated clusters that are expressed in the developing skeletons of the face and appendages. IrxB cluster genes are required for the separation of toes in mice and formation of the hyoid joint in zebrafish, yet whether Irx genes have broader roles in skeletal development remains unclear. Here, we perform a comprehensive loss-of-function analysis of all 11 Irx genes in zebrafish. We uncover conserved requirements for IrxB genes in formation of the fish and mouse scapula. In the face, we find a requirement for IrxAb genes and irx7 in formation of anterior neural crest precursors of the jaw, and for IrxBa genes in formation of endodermal pouches and gill cartilages. We also observe extensive joint loss and cartilage fusions in animals with combinatorial losses of Irx clusters, with in vivo imaging revealing that at least some of these fusions arise through inappropriate chondrogenesis. Our analysis reveals diverse roles for Irx genes in the formation and later segmentation of the facial skeleton.

MicroRNA expression profiling of adult hippocampal neural stem cells upon cell death reveals an autophagic cell death-like pattern.

Adult hippocampal neural (HCN) stem cells promptly undergo irreversible autophagic cell death (ACD) if deprived of insulin in culture. Small, non-coding microRNAs (miRNA) play an important role in regulating biological processes, including proliferation and cell death. However, there have been no reports thus far regarding miRNA involvement in the induction of adult HCN stem cell death under insulin-deprived conditions, for which we performed a microarray-based analysis to examine the expression signature of miRNAs in adult rat HCN stem cells. Three independent specimens per culture condition either with or without insulin were prepared and a miRNA microarray analysis carried out. A total of 12 exhibited significantly altered expression levels upon cell death due to the absence of insulin when compared to HCN stem cells cultured with insulin present (cut-off limit; p < 0.05 and fold-change >1.3) The resulting volcano plot showed that, among these miRNAs, seven were upregulated and five were downregulated. The upregulated miRNAs were capable of modulating HCN stem cell death. Caspase-3 activity analysis, LC3 conversion, and TEM of autophagosome formation consistently suggested that ACD, not apoptosis, was most likely the mechanism affecting HCN cell death. As such, we have come to term these miRNAs, "HCN stem cell-specific autophagic cell death regulators." Taken together, our data suggest that the miRNA expression profile of HCN stem cells is altered during ACD occurring due to insulin deprivation and that differentially expressed miRNAs are involved in HCN stem cell viability. Detailed explorations of the underlying mechanisms regarding HCN stem cell viability modulation by these miRNAs would be beneficial in further understanding the physiological features of adult HCN stem cells and are currently being investigated.

Mifepristone/RU486 acts in Drosophila melanogaster females to counteract the life span-shortening and pro-inflammatory effects of male Sex Peptide.

Males with null mutation of Sex Peptide (SP) gene were compared to wild-type males for the ability to cause physiological changes in females that could be reversed by mifepristone. Males from wild-type strains decreased median female life span by average -51%. Feeding mifepristone increased life span of these females by average +106%. In contrast, SP-null males did not decrease female life span, and mifepristone increased median life span of these females by average +14%, which was equivalent to the effect of mifepristone in virgin females (average +16%). Expression of innate immune response transgenic reporter (Drosocin-GFP) was increased in females mated to wild-type males, and this expression was reduced by mifepristone. In contrast, SP-null males did not increase Drosocin-GFP reporter expression in the female. Similarly, mating increased endogenous microbial load, and this effect was reduced or absent in females fed mifepristone and in females mated to SP-null males; no loss of intestinal barrier integrity was detected using dye-leakage assay. Reduction of microbial load by treating adult flies with doxycycline reduced the effects of both mating and mifepristone on life span. Finally, mifepristone blocked the negative effect on life span caused by transgenic expression of SP in virgin females. The data support the conclusion that the majority of the life span-shortening, immune-suppressive and pro-inflammatory effects of mating are due to male SP, and demonstrate that mifepristone acts in females to counteract these effects of male SP.