F-actin coordinates spindle morphology and function in Drosophila meiosis

Stage-specific transcriptomic analysis reveals insights into the development, reproduction and biological function of allergens in the European house dust mite Dermatophagoides pteronyssinus

BACKGROUND

House dust mites (HDMs) such as Dermatophagoides pteronyssinus are major allergy elicitors worldwide, yet their gene expression across developmental stages remains underexplored. Herein, we report a comprehensive RNAseq analysis of larvae, nymphs, and adult males and females, mapped to a recently published high-quality genome with extended functional annotations.

RESULTS

Analysis of differentially expressed genes (DEG) revealed that female-biased expression was the most prevalent profile (16% of genes), while males exhibited the highest fold-change differences. DEG data, combined with network clustering and functional enrichment analysis, highlighted distinct genes and biological processes for each stage and sex: females showed upregulation of genes related to cell division and oogenesis, with vitellogenins among the most abundant transcripts; males exhibited increased expression of genes encoding putative seminal fluid proteins (e.g. endopeptidases, serpins, antimicrobial peptides), and those involved in reproductive regulation (e.g. testis-specific serine kinases); while juveniles displayed enhanced expression of genes related to energy metabolism and growth. Further analysis of endocrine pathways revealed non-canonic mechanisms compared to insect models, particularly in ecdysteroid and sesquiterpenoid biosynthesis and regulation. Expression patterns in genes involved in cuticle formation were also identified, reflecting their role in developmental transitions and sexual differentiation. Allergen and allergen-related gene expression showed an overall increase in feeding juveniles, as well as sex-biased expression, with Der p 27 upregulated in females. These findings provide insight into the physiological roles of allergens in digestion, immunity, and muscle formation, among other functions. Additionally, seven new horizontally transferred genes, including a DNA-repair photolyase linked to females, and novel multigene families (e.g. 119 male-specific beta-propeller proteins, 70 hypothetical cuticular proteins, 23 tetraspanin-like proteins, 5 female-associated putative odorant-binding proteins) were identified.

CONCLUSIONS

This study provides the first genome-wide transcriptomic analysis of a HDM across life stages and sexes, expanding our understanding of the molecular mechanisms underlying mite development, sexual reproduction, and allergen expression. The generated data, fully available via supplementary spreadsheet and the ORCAE online platform, provide a valuable foundation for future allergy research and the development of new mite control strategies.

RNA-binding protein Miso/CG44249 is crucial for minor splicing during oogenesis in Drosophila

Pre-mRNA introns are removed by two distinct spliceosomes: the major (U2-type) spliceosome, which splices over 99.5% of introns, and the minor (U12-type) spliceosome, responsible for a rare class of introns known as minor introns. While the major spliceosome contains U1, U2, U4, U5, and U6 small nuclear RNAs (snRNAs) along with numerous associated proteins, the minor spliceosome comprises U11, U12, U4atac, U5, and U6atac snRNAs and includes specialized proteins. The function and regulation of the minor spliceosome are critical. Mutations in its specific component, RNA-binding protein RNPC3/65K, are linked to human diseases such as primary ovarian insufficiency. In this study, we identify RNA-binding protein Miso (CG44249), which shares 31% and 27% amino acid sequence identity with human RNPC3 and RBM41, respectively, as a key factor in minor splicing and oogenesis in Drosophila Miso associates with U11 and U12 snRNAs in ovaries. miso mutant females exhibit smaller ovaries, reduced germline stem cell numbers, disrupted oogenesis, reduced fecundity, and lower fertility. In miso mutant ovaries, significant minor intron retention is observed, accompanied by a reduction in spliced RNAs and protein products. Our findings establish Miso as a critical factor for minor intron splicing and underscore its essential role in Drosophila oogenesis.

No transcription, no problem: Protein phosphorylation changes and the transition from oocyte to embryo

Although mature oocytes are arrested in a differentiated state, they are provisioned with maternally-derived macromolecules that will start embryogenesis. The transition to embryogenesis, called 'egg activation', occurs without new transcription, even though it includes major cell changes like completing stalled meiosis, translating stored mRNAs, cytoskeletal remodeling, and changes to nuclear architecture. In most animals, egg activation is triggered by a rise in free calcium in the egg's cytoplasm, but we are only now beginning to understand how this induces the egg to transition to totipotency and proliferation. Here, we discuss the model that calcium-dependent protein kinases and phosphatases modify the phosphorylation landscape of the maternal proteome to activate the egg. We review recent phosphoproteomic mass spectrometry analyses that revealed broad phospho-regulation during egg activation, both in number of phospho-events and classes of regulated proteins. Our interspecies comparisons of these proteins pinpoints orthologs and protein families that are phospho-regulated in activating eggs, many of which function in hallmark events of egg activation, and others whose regulation and activity warrant further study. Finally, we discuss key phospho-regulating enzymes that may act apically or as intermediates in the phosphorylation cascades during egg activation. Knowing the regulators, targets, and effects of phospho-regulation that cause an egg to initiate embryogenesis is crucial at both fundamental and applied levels for understanding female fertility, embryo development, and cell-state transitions.