POU domain motif3 (Pdm3) induces wingless (wg) transcription and is essential for development of larval neuromuscular junctions in Drosophila

A brief review of current treatment options for osteoarthritis including disease-modifying osteoarthritis drugs (DMOADs) and novel therapeutics

Osteoarthritis (OA) is a chronic disorder caused by degenerative changes in articular cartilage, which are mainly manifests as degeneration of cartilage, subchondral bone remodeling, as well as synovial inflammation. Over the next few decades, OA and its burden will continue to increase worldwide, posing a major public health challenge for the foreseeable future. Treatment for OA includes non-pharmacological, pharmacological, and surgical treatments. Existing conservative treatments and joint surgery can only alleviate the symptoms and cannot be cured, so new therapies for OA are urgently needed. Since advances in the understanding of OA pathophysiology, researchers have identified some potential therapeutic targets against degeneration of cartilage, subchondral bone remodeling and synovial inflammation, enabling development of the disease-modifying OA drugs (DMOADs). Additionally, a number of new technologies are also being investigated for treating OA, such as RNA interference (RNAi), CRISPR/Cas9 and PROTAC. The goal of this review is to describe the current development status of DMOADs and to discuss the potential of emerging therapeutic approaches for treating OA, thus providing a reference for OA treatments.

Dynein Heavy Chain 64C Differentially Regulates Cell Survival and Proliferation of Wingless-Producing Cells in Drosophila melanogaster

Dynein is a multi-subunit motor protein that moves toward the minus-end of microtubules, and plays important roles in fly development. We identified Dhc64C^m115, a new mutant allele of the fly Dynein heavy chain 64C (Dhc64C) gene whose heterozygotes survive against lethality induced by overexpression of Sol narae (Sona). Sona is a secreted metalloprotease that positively regulates Wingless (Wg) signaling, and promotes cell survival and proliferation. Knockdown of Dhc64C in fly wings induced extensive cell death accompanied by widespread and disorganized expression of Wg. The disrupted pattern of the Wg protein was due to cell death of the Wg-producing cells at the DV midline and overproliferation of the Wg-producing cells at the hinge in disorganized ways. Coexpression of Dhc64C RNAi and p35 resulted in no cell death and normal pattern of Wg, demonstrating that cell death is responsible for all phenotypes induced by Dhc64C RNAi expression. The effect of Dhc64C on Wg-producing cells was unique among components of Dynein and other microtubule motors. We propose that Dhc64C differentially regulates survival of Wg-producing cells, which is essential for maintaining normal expression pattern of Wg for wing development.

The histone demethylase KDM5 is required for synaptic structure and function at the Drosophila neuromuscular junction

Mutations in the genes encoding the lysine demethylase 5 (KDM5) family of histone demethylases are observed in individuals with intellectual disability (ID). Despite clear evidence linking KDM5 function to neurodevelopmental pathways, how this family of proteins impacts transcriptional programs to mediate synaptic structure and activity remains unclear. Using the Drosophila larval neuromuscular junction (NMJ), we show that KDM5 is required presynaptically for neuroanatomical development and synaptic function. The Jumonji C (JmjC) domain-encoded histone demethylase activity of KDM5, which is expected to be diminished by many ID-associated alleles, is required for appropriate synaptic morphology and neurotransmission. The activity of the C5HC2 zinc finger is also required, as an ID-associated mutation in this motif reduces NMJ bouton number, increases bouton size, and alters microtubule dynamics. KDM5 therefore uses demethylase-dependent and independent mechanisms to regulate NMJ structure and activity, highlighting the complex nature by which this chromatin modifier carries out its neuronal gene-regulatory programs.

Anastral Spindle 3/Rotatin Stabilizes Sol narae and Promotes Cell Survival in Drosophila melanogaster

Apoptosis and compensatory proliferation, two intertwined cellular processes essential for both development and adult homeostasis, are often initiated by the mis-regulation of centrosomal proteins, damaged DNA, and defects in mitosis. Fly Anastral spindle 3 (Ana3) is a member of the pericentriolar matrix proteins and known as a key component of centriolar cohesion and basal body formation. We report here that ana3m19 is a suppressor of lethality induced by the overexpression of Sol narae (Sona), a metalloprotease in a disintegrin and metalloprotease with thrombospondin motif (ADAMTS) family. ana3m19 has a nonsense mutation that truncates the highly conserved carboxyl terminal region containing multiple Armadillo repeats. Lethality induced by Sona overexpression was completely rescued by knockdown of Ana3, and the small and malformed wing and hinge phenotype induced by the knockdown of Ana3 was also normalized by Sona overexpression, establishing a mutually positive genetic interaction between ana3 and sona. p35 inhibited apoptosis and rescued the small wing and hinge phenotype induced by knockdown of ana3. Furthermore, overexpression of Ana3 increased the survival rate of irradiated flies and reduced the number of dying cells, demonstrating that Ana3 actively promotes cell survival. Knockdown of Ana3 decreased the levels of both intra- and extracellular Sona in wing discs, while overexpression of Ana3 in S2 cells dramatically increased the levels of both cytoplasmic and exosomal Sona due to the stabilization of Sona in the lysosomal degradation pathway. We propose that one of the main functions of Ana3 is to stabilize Sona for cell survival and proliferation.

Exosomal arrow (Arr)/lipoprotein receptor protein 6 (LRP6) in Drosophila melanogaster increases the extracellular level of Sol narae (Sona) in a Wnt-independent manner

Wg/Wnt as a signaling protein binds to Frizzled (Fz) and Arrow (Arr), two Wg co-receptors essential for Wg signaling for cell proliferation, differentiation, and cell survival. Arr has a long extracellular region, a single transmembrane domain and an intracellular region. Here, we report that a new arr^m7 mutant is identified in a genetic screen as a suppressor of lethality induced by overexpression of Sol narae (Sona), a secreted metalloprotease in ADAMTS family involved in Wg signaling. arr^m7 allele has a premature stop codon, which encodes Arr^m7 protein missing the intracellular region. arr^m7 clones show cell death phenotype and overexpression of Arr^m7 protein also induces cell death. Levels of extracellular Sona were decreased in both arr^m7 and arr² null clones, demonstrating that Arr increases the level of extracellular Sona. Indeed, Arr but not Arr^m7, increased levels of Sona in cytoplasm and exosome fraction by inhibiting the lysosomal degradation pathway. Interestingly, Arr itself was identified in the exosome fraction, demonstrating that Arr is secreted to extracellular space. When Sona-expressing S2 cells were treated with exosomal Arr, the extracellular level of active Sona was increased. These results show that exosomal Arr dictates Sona-expressing cells to increase the level of extracellular Sona. This new function of Arr occurred in the absence of Wg because S2 cells do not express Wg. We propose that Arr plays two distinct roles, one as an exosomal protein to increase the level of extracellular Sona in a Wnt-independent manner and the other as a Wg co-receptor in a Wnt-dependent manner.