Loss of histone deacetylase HDAC1 induces cell death in Drosophila epithelial cells through JNK and Hippo signaling

Genome-Wide Expression Analysis of Long Noncoding RNAs and Their Target Genes in Metafemale Drosophila

Aneuploidy is usually more detrimental than altered ploidy of the entire set of chromosomes. To explore the regulatory mechanism of gene expression in aneuploidy, we analyzed the transcriptome sequencing data of metafemale Drosophila. The results showed that most genes on the X chromosome undergo dosage compensation, while the genes on the autosomal chromosomes mainly present inverse dosage effects. Furthermore, long noncoding RNAs (lncRNAs) have been identified as key regulators of gene expression, and they are more sensitive to dosage changes than mRNAs. We analyzed differentially expressed mRNAs (DEGs) and differentially expressed lncRNAs (DELs) in metafemale Drosophila and performed functional enrichment analyses of DEGs and the target genes of DELs, and we found that they are involved in several important biological processes. By constructing lncRNA-mRNA interaction networks and calculating the maximal clique centrality (MCC) value of each node in the network, we also identified two key candidate lncRNAs (CR43940 and CR42765), and two of their target genes, Sin3A and MED1, were identified as inverse dosage modulators. These results suggest that lncRNAs play an important role in the regulation of genomic imbalances. This study may deepen the understanding of the gene expression regulatory mechanisms in aneuploidy from the perspective of lncRNAs.

EGFR phosphorylates HDAC1 to regulate its expression and anti-apoptotic function

HDAC1 is the prototypical human histone deacetylase (HDAC) enzyme responsible for catalyzing the removal of acetyl group from lysine residues on many substrate proteins. By deacetylating histones and non-histone proteins, HDAC1 has a profound effect on the regulation of gene transcription and many processes related to cell growth and cell death, including cell cycle progression, DNA repair, and apoptosis. Early studies reveal that, like most eukaryotic proteins, the functions and activities of HDAC1 are regulated by post-translational modifications. For example, serine phosphorylation of HDAC1 by protein kinase CK2 promotes HDAC1 deacetylase enzymatic activity and alters its interactions with proteins in corepressor complexes. Here, we describe an alternative signaling pathway by which HDAC1 activities are regulated. Specifically, we discover that EGFR activity promotes the tyrosine phosphorylation of HDAC1, which is necessary for its protein stability. A key EGFR phosphorylation site on HDAC1, Tyr72, mediates HDAC1's anti-apoptotic function. Given that HDAC1 overexpression and EGFR activity are strongly related with tumor progression and cancer cell survival, HDAC1 tyrosine phosphorylation may present a possible target to manipulate HDAC1 protein levels in future potential cancer treatment strategies.

Reduction of Rpd3 suppresses defects in locomotive ability and neuronal morphology induced by the knockdown of Drosophila SLC25A46 via an epigenetic pathway

Mitochondrial dysfunction causes various diseases. Mutations in the SLC25A46 gene have been identified in mitochondrial diseases that are sometimes classified as Charcot-Marie-Tooth disease type 2, optic atrophy, and Leigh syndrome. A homolog of SLC25A46 was identified in Drosophila and designated as dSLC25A46 (CG5755). We previously established mitochondrial disease model targeting of dSLC25A46, which causes locomotive dysfunction and morphological defects at neuromuscular junctions, such as reduced synaptic branch lengths and decreased numbers of boutons. The diverse symptoms of mitochondrial diseases carrying mutations in SLC25A46 may be associated with the dysregulation of some epigenetic regulators. To investigate the involvement of epigenetic regulators in mitochondrial diseases, we examined candidate epigenetic regulators that interact with human SLC25A46 by searching Gene Expression Omnibus (GEO). We discovered that HDAC1 binds to several SLC25A46 genomic regions in human cultured CD4 (+) cells, and attempted to prove this in an in vivo Drosophila model. By demonstrating that Rpd3, Drosophila HDAC1, regulates the histone H4K8 acetylation state in dSLC25A46 genomic regions, we confirmed that Rpd3 is a novel epigenetic regulator modifying the phenotypes observed with the mitochondrial disease model targeting of dSLC25A46. The functional reduction of Rpd3 rescued the deficient locomotive ability and aberrant morphology of motoneurons at presynaptic terminals induced by the dSLC25A46 knockdown. The present results suggest that the inhibition of HDAC1 suppresses the pathogenic processes that lead to the degeneration of motoneurons in mitochondrial diseases.

The histone deacetylase NlHDAC1 regulates both female and male fertility in the brown planthopper, Nilaparvata lugens

Histone acetylation is a specific type of chromatin modification that serves as a key regulatory mechanism for many cellular processes in mammals. However, little is known about its biological function in invertebrates. Here, we identified 12 members of histone deacetylases (NlHDACs) in the brown planthopper (BPH), Nilaparvata lugens. RNAi-mediated silencing assay showed that NlHdac1, NlHdac3 and NlHdac4 played critical roles in female fertility via regulating ovary maturation or ovipositor development. Silencing of NlHdac1 substantially increased acetylation level of histones H3 and H4 in ovaries, indicating NlHDAC1 is the main histone deacetylase in ovaries of BPH. RNA sequencing (RNA-seq) analysis showed that knockdown of NlHdac1 impaired ovary development via multiple signalling pathways including the TOR pathway. Acoustic recording showed that males with NlHdac1 knockdown failed to make courtship songs, and thus were unacceptable to wild-type females, resulting in unfertilized eggs. Competition mating assay showed that wild-type females overwhelmingly preferred to mate with control males over NlHdac1-knockdown males. These findings improve our understanding of reproductive strategies controlled by HDACs in insects and provide a potential target for pest control.

A positive role of Sin3A in regulating Notch signaling during Drosophila wing development

Notch is a transmembrane receptor that mediates intercellular signaling through a conserved signaling cascade in all animal species. Transcriptional and posttranscriptional regulation of Notch receptor are important for maintaining Notch signaling activity. Here, we show that depletion of Drosophila Sin3A leads to loss of the adult wing margin and downregulation of Notch target gene expression in the developing wing disc. Sin3A regulates the Notch pathway downstream of Delta and upstream of Notch activation. The role of Sin3A in the Notch pathway is partly mediated by its ability to modulate Notch receptor transcription. Furthermore, the transcriptional activation of Notch receptor is autoregulated by Notch itself. We also provide evidence that Sin3A is required for Notch activation mediated Notch transcription. Together, our data demonstrate that Sin3A activates Notch signaling by promoting Notch transcription and reveal a previously unknown autoregulatory mechanism for Notch signaling activation during Drosophila wing development.

APLP2 Modulates JNK-Dependent Cell Migration in Drosophila

Amyloid precursor-like protein 2 (APLP2) belongs to the APP family and is widely expressed in human cells. Though previous studies have suggested a role of APLP2 in cancer progression, the exact role of APLP2 in cell migration remains elusive. Here in this report, we show that ectopic expression of APLP2 in Drosophila induces cell migration which is mediated by JNK signaling, as loss of JNK suppresses while gain of JNK enhances such phenotype. APLP2 is able to activate JNK signaling by phosphorylation of JNK, which triggers the expression of matrix metalloproteinase MMP1 required for basement membranes degradation to promote cell migration. The data presented here unraveled an in vivo role of APLP2 in JNK-mediated cell migration.

The histone deacetylase HDAC1 positively regulates Notch signaling during Drosophila wing development

The Notch signaling pathway is highly conserved across different animal species and plays crucial roles in development and physiology. Regulation of Notch signaling occurs at multiple levels in different tissues and cell types. Here, we show that the histone deacetylase HDAC1 acts as a positive regulator of Notch signaling during Drosophila wing development. Depletion of HDAC1 causes wing notches on the margin of adult wing. Consistently, the expression of Notch target genes is reduced in the absence of HDAC1 during wing margin formation. We further provide evidence that HDAC1 acts upstream of Notch activation. Mechanistically, we show that HDAC1 regulates Notch protein levels by promoting Notch transcription. Consistent with this, the HDAC1-associated transcriptional co-repressor Atrophin (Atro) is also required for transcriptional activation of Notch in the wing disc. In summary, our results demonstrate that HDAC1 positively regulates Notch signaling and reveal a previously unidentified function of HDAC1 in Notch signaling.