Biology subjects

Belalcazar, H. M.

Publications and source records attributed to Belalcazar, H. M..

5 recordsLinked to original sources

bioRxiv2020

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

Mutations in the genes encoding the 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 for neuroanatomical development and synaptic function. The JmjC-domain encoded histone demethylase activity of KDM5, which is expected to be diminished by many ID-associated alleles and required for appropriate synaptic morphology and neurotransmission. The C5HC2 zinc finger of KDM5 is also involved, as an ID-associated mutation in this motif reduces NMJ bouton number but increases bouton size. 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.

neuroscience↗

bioRxiv2020

The Drosophila histone demethylase KDM5 is required during early neurodevelopment for proper mushroom body formation and cognitive function

Mutations in the lysine demethylase 5 (KDM5) family of transcriptional regulators are associated with intellectual disability, yet little is known regarding the spatiotemporal requirements or neurodevelopmental contributions of KDM5 proteins. Utilizing the mushroom body (MB), a major learning and memory center within the Drosophila brain, we demonstrate that KDM5 is specifically required within ganglion mother cells and immature neurons for proper neurodevelopment and cognitive function. Within this cellular subpopulation, we identify a core network of KDM5-regulated genes that are critical modulators of neurodevelopment. Significantly, we find that a majority of these genes are direct targets of Prospero (Pros), a transcription factor with well-established roles in neurodevelopment in other neuronal contexts. We demonstrate that Pros is essential for MB development and functions downstream of KDM5 to regulate MB morphology. We therefore provide evidence for a KDM5-Pros axis that orchestrates a transcriptional program critical for proper axonal development and cognitive function.

neuroscience↗

bioRxiv2019

Age-dependent neuroprotective effect of an SK3. channel agonist on excitotoxityto dopaminergic neurons in organotypic culture

We evaluated the age-dependency of the neuroprotective effect of an small-conductance calcium activated potassium channel 3 (SK3) agonist, 1-EBIO, on AMPA excitoxicity to dopaminergic neurons (DN) in organotypic cultures. Most TH+ neurons were also SK3+. SK3+/TH-cells (DN+) were common at each developmental stage but more prominently at day in vitro (DIV) 8. Young DN+ neurons were small bipolar and fusiform, whereas mature ones were large and multipolar. Exposure of organotypic cultures to AMPA (100 m, 16 h) had no effect on the survival of DN+ at DIV 8, but caused significant toxicity at DIV 15 (n=15, p=0.005) and DIV 22 (n=15, p<<0.001). These results indicate that susceptibility of DN to AMPA excitotoxicity is developmental stage-dependent in embryonic VM organotypic cultures. Immature DN+ (small, bipolar) were increased after AMPA (100 m, 16 h) at DIV 8, at the expense of the number of differentiated (large, multipolar) DN+ (p=0.039). This effect was larger at DIV 15 (p<<<0.0001) and at DIV 22 (p<<<0.0001). At DIV 8, 30 M 1-EBIO resulted in a large increase in DN+. At DIV 15, AMPA toxicity was prevented by exposure to 30 M, but not 100 M 1-EBIO. At DIV 22, excitotoxicity was unaffected by 30 M 1-EBIO, and partially reduced by 100 M 1-EBIO. The effects of the SK3. channel agonist 1-EBIO on the survival of SK3.-expressing dopaminergic neurons were concentrationdependent and influenced by neuronal developmental stage.

neuroscience↗

bioRxiv2019

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

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 largely unknown. 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 mutant animal is sufficient to rescue both the larval developmental delay and the pupal lethality caused by loss of KDM5. Molecularly, 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. This occurs through KDM5-mediated regulation of the receptor tyrosine kinase torso, which in in turn 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 the molecular mechanisms that govern the transcriptional regulation of animal development.

developmental biology↗

bioRxiv2018

The histone demethylase KDM5 is essential for larval growth in Drosophila

Regulated gene expression is necessary for developmental and homeostatic processes. The KDM5 family of proteins are histone H3 lysine 4 demethylases that can regulate transcription through both demethylase-dependent and independent mechanisms. While loss and overexpression of KDM5 proteins are linked to intellectual disability and cancer, respectively, their normal developmental functions remain less characterized. Drosophila melanogaster provides an ideal system to investigate KDM5 function, as it encodes a single ortholog in contrast to the four paralogs found in mammalian cells. To examine the consequences of complete loss of KDM5, we generated a null allele of Drosophila kdm5, also known as little imaginal discs (lid), and show that it is essential for development. Animals lacking KDM5 die during late pupal development but show a dramatically delayed larval development that coincides with decreased proliferation and increased cell death in imaginal discs. Interestingly, this developmental delay is independent of the well-characterized Jumonji C (JmjC) domain-encoded histone demethylase activity and plant homedomain (PHD) motif-mediated chromatin binding activities of KDM5, suggesting key functions for less characterized domains. Consistent with the phenotypes observed, transcriptome analyses of kdm5 null mutant wing imaginal discs revealed the dysregulation of genes involved in several cellular processes, including cell cycle progression and DNA repair. Together, our data provide the first description of complete loss of KDM5 function in a metazoan and offer an invaluable tool for defining the biological activities of KDM5 family proteins.

genetics↗