Biology subjects

Warsinger-Pepe, N.

Publications and source records attributed to Warsinger-Pepe, N..

4 recordsLinked to original sources

bioRxiv2026

Influence of the male germline on B chromosome transmission in D. melanogaster

Selfish genetic elements that bias their inheritance to the detriment to their host are in an evolutionary arms race with host-derived suppressors that neutralize the spread of these elements. The supernumerary B chromosomes recently found in a mutant Drosophila melanogaster laboratory stock are subject to drive (>50% transmission) when passed through the female germline, but through the male germline they experience the opposite of drive, a phenomenon referred to as drag (<50% transmission). Here we show that males from this mutant stock do not have fertility defects, excluding the possibility that sperm carrying more B chromosomes are inviable. Though we revealed irregularities in the germline stem cell (GSC) niche, we show that other aspects of GSCs activity is normal: there is no delay in their mitoses and the B chromosomes appear to be symmetrically segregated during the GSC divisions, suggesting that the asymmetry of these divisions is not likely the source of B chromosome drag. Together, this work lays the foundation for future studies into the mechanism of paternal B chromosome drag in D. melanogaster, which is poised to significantly advance on our understanding of how various genetic and developmental contexts promote disparate chromosome behavior.

genetics↗

bioRxiv2022

Polycomb response elements reduce leaky expression of Cas9 under temperature-inducible Hsp70Bb promoter in Drosophila melanogaster

Heat shock inducible expression of genes through the use of heat inducible promoters is commonly used in research despite leaky expression of downstream genes of interest without targeted induction (i.e. heat shock). The development of non-leaky inducible expression systems are of broad interest for both basic and applied studies, to precisely control gene expression. Here we characterize the use of Polycomb response elements and the inducible Heat shock protein 70Bb promoter, previously described as a non-leaky inducible system, to regulate Cas9 endonuclease levels and function in Drosophila melanogaster after varying both heat shock durations and rearing temperatures. We show that Polycomb response elements can significantly reduce expression of Cas9 under Heat shock protein 70Bb promoter control using a range of conditions, corroborating previously published results. We further demonstrate that this low transcript level of heat-induced Cas9 is sufficient to induce mutant mosaic phenotypes. Incomplete suppression of an inducible Cas9 system by Polycomb response elements with no heat shock suggests that further regulatory elements are required to precisely control Cas9 expression and abundance.

synthetic biology↗

bioRxiv2019

Regulation of nucleolar dominance in Drosophila melanogaster

In eukaryotic genomes, ribosomal RNA (rRNA) genes exist as tandemly repeated clusters, forming ribosomal DNA (rDNA) loci. Each rDNA locus typically contains hundreds of rRNA genes to meet the high demand of ribosome biogenesis. Nucleolar dominance is a phenomenon, whereby individual rDNA loci are entirely silenced or transcribed, and is believed to be a mechanism to control rRNA dosage. Nucleolar dominance was originally noted to occur in interspecies hybrids, and has been shown to occur within a species (i.e. non-hybrid contexts). However, studying nucleolar dominance within a species has been challenging due to the highly homogenous sequence across rDNA loci. By utilizing single nucleotide polymorphisms (SNPs) between X rDNA vs. Y rDNA loci in males, as well as sequence variations between two X rDNA loci in females, we conducted a thorough characterization of nucleolar dominance throughout development of D. melanogaster. We demonstrate that nucleolar dominance is a developmentally-regulated program, where Y rDNA dominance is established during male embryogenesis, whereas females normally do not exhibit dominance between two X rDNA loci. By utilizing various chromosomal complements (e.g. X/Y, X/X, X/X/Y) and a chromosome rearrangement, we show that Y chromosome rDNA likely contains cis elements that dictate its dominance over the X chromosome rDNA. Our study begins to reveal the mechanisms underlying the selection of rDNA loci for activation/silencing in nucleolar dominance.

developmental biology↗

bioRxiv2017

Transgenerational dynamics of rDNA copy number in Drosophila male germline stem cells

rDNA loci, composed of hundreds of tandemly duplicated arrays of rRNA genes, are known to be among the most unstable genetic elements due to their repetitive nature. rDNA instability underlies aging (replicative senescence) in yeast cells, however, its contribution to the aging of multicellular organisms is poorly understood. In this study, we investigate the dynamics of rDNA loci during aging in the Drosophila male germline stem cell (GSC) lineage, and show that rDNA copy number decreases during aging. Our study further reveals that this age-dependent decrease in rDNA copy number is heritable from generation to generation, yet GSCs in animals that inherit reduced rDNA copy number are capable of recovering normal rDNA copy number. Based on these findings, we propose that rDNA loci are dynamic genetic elements, where rDNA copy number changes dynamically yet is maintained through a recovery mechanism in the germline.

developmental biology↗