The histone demethylase KDM5 controls developmental timing in Drosophila by promoting prothoracic gland endocycles

Abstract

In Drosophila, the larval prothoracic gland integrates nutritional status with developmental signals to regulate growth and maturation through the secretion of the steroid hormone ecdysone. While the nutritional signals and cellular pathways that regulate prothoracic gland function are relatively well studied, the transcriptional regulators that orchestrate the activity of this tissue remain less characterized. Here, we show that lysine demethylase 5 (KDM5) is essential for prothoracic gland function. Indeed, restoring kdm5 expression only in the prothoracic gland in an otherwise kdm5 null mutant animal is sufficient to rescue both the larval developmental delay and the pupal lethality caused by loss of KDM5. Our studies show that KDM5 functions by promoting the endoreplication of prothoracic gland cells, a process that increases ploidy and is rate limiting for the expression of ecdysone biosynthetic genes. Molecularly, we show that KDM5 activates the expression of the receptor tyrosine kinase torso, which then promotes polyploidization and growth through activation of the MAPK signaling pathway. Taken together, our studies provide key insights into the biological processes regulated by KDM5 and expand our understanding of the transcriptional regulators that coordinate animal development.

Regulation of Body Size and Growth Control

“…Since endoreduplication is an irreversible process that increases the ploidy of the PG cells, this mechanism translates nutritional cues into increased transcription that commits the PG to producing ecdysone at the CW transition. The importance of endoreduplication within the cells of the PG to the regulation of ecdysone is further supported by the finding that lysine demethylase 5 (Kdm5) is specifically required for endoreduplication in the PG through its transcriptional upregulation of torso (Drelon et al 2019). TOR also regulates autophagy-mediated cholesterol trafficking that affects CW Texada et al 2019b).…”

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

“…We then quantified the number and size of type Ib synaptic boutons, which are predominantly responsible for muscle contraction ( Newman et al, 2017 ), at muscle 4 of the third abdominal segment. Because kdm5 140 mutants show a slow-growth phenotype that results in larvae taking longer to develop to the same size as wild-type (WT) animals, we matched animals developmentally rather than chronologically, as we have done previously ( Drelon et al, 2018 , 2019 ). In addition, we normalized the number of boutons to muscle size to account for any slight differences in larval size.…”

“…To determine where KDM5 function is required to mediate its effects on NMJ morphology, we restored kdm5 expression in specific cell types within kdm5 140 protein-null animals. To do this, we used a UAS-kdm5 transgene that drives low levels of expression (~2-fold increase over endogenous levels) ( Drelon et al, 2019 ; Li et al, 2010 ; Secombe et al, 2007 ) and a range of well-characterized Gal4 drivers. Re-expression of kdm5 ubiquitously ( Act5C-Gal4 and da-Gal4 ), pan-neuronally ( elav-Gal4 ), or in motor neurons ( OK6-Gal4 ) significantly rescued the bouton number deficit of kdm5 140 larvae ( Figures 1D and 1G ).…”

“…The number of male and female larvae were equal across the genotypes examined. For studies comparing wild-type and kdm5 mutant larvae, animals were matched for developmental stage based on the morphology of larval mouth hooks, not chronological age, similar to our previously reported analyses ( Drelon et al, 2018 , 2019 ). Control wandering third instar larvae were therefore ~120 hours after egg laying (AEL) while kdm5 140 larvae were 8-10 days old.…”

“…The kdm5 140 null and kdm5 JmjC* alleles have been previously described ( Drelon et al, 2018 ; Navarro-Costa et al, 2016 ; Zamurrad et al, 2018 ). UASp-kdm5 transgene was validated in numerous rescue experiments ( Drelon et al, 2019 ; Li et al, 2010 ; Secombe et al, 2007 ). The UAS-shRNA transgene to knockdown kdm5 was generated as part of the TRiP project and has been well-validated by us and others (BL #35706) ( Liu et al, 2014 ; Navarro-Costa et al, 2016 ).…”