Biology subjects

Hatkevich, T.

Publications and source records attributed to Hatkevich, T..

3 recordsLinked to original sources

bioRxiv2026

In mice, a population of male germ cells show characteristics of non-apoptotic cell death during G0 arrest

In mammals, a small population of spermatogonial stem cells (SSCs) is established shortly after birth. These cells self-renew and produce sperm for the entirety of a males reproductive lifespan, passing the genome on to the next generation. Thus, establishment of a population of SSCs with high genomic integrity is essential. SSCs are derived from a much larger precursor population of male germ cells (MGCs) that differentiate during fetal life. During the last third of gestation, MGCs undergo a prolonged period of G0 cell cycle arrest during which they sustain high levels of transcription and acquire epigenetic programming for SSC fate. Although these differentiation steps can cause cellular and genomic damage, it has been unclear whether selection for germ cell quality occurs during G0 arrest since no classic markers of cell death have been detected. In this study, we utilize a mouse model to characterize a population of MGCs that begin to accumulate markers if cell death, such as AnnexinV (AnV) and propidium iodide (PI), at E16.5. The AnV- and PI-positive MGC population is characterized by low expression of the RNA-binding protein, Dead End 1 (DND1), and exhibit dsDNA breaks and mitochondrial dysfunction. Interestingly, we do not see evidence of an active cell death cascade until the time of birth, where we see phosphorylation of MLKL, a hallmark of a necroptotic cell death mechanism. Based on these findings, we propose that variable cellular health is an important basis for selection of the SSC precursors. Significance StatementSpermatogonial stem cells (SSCs) are essential for reproductive fitness, yet how their precursors are selected during development is not known. Utilizing a mouse model, this study describes high levels of cellular damage within a subset of male germ cells (MGCs) during G0 arrest. The damaged MGC population was marked by low expression of the RNA-binding protein, DND1, and was strongly associated with mitochondrial dysfunction and dsDNA breaks. We observed signs of non-apoptotic cell death by embryonic day (E)16.5 and the appearance of necroptotic markers in MGCs at the time of birth. This study uncovers previously unknown heterogeneity in the MGC pool and points to MGC health as an important source of selection during G0 arrest.

developmental biology↗

bioRxiv2020

Collaboration between homologous recombination and non-homologous end joining in repair of meiotic double-strand breaks in Drosophila

Programmed DNA double-strand breaks (DSBs) made during meiosis are repaired by recombination with the homologous chromosome to generate, at selected sites, reciprocal crossovers that are critical for the proper separation of homologs in the first meiotic divisions. Backup repair processes can compensate when the normal meiotic recombination processes are non-functional. We describe a novel backup repair mechanism that occurs when the homologous chromosome is not available in Drosophila melanogaster meiosis. In the presence of a previously described mutation (Mcm5A7) that disrupts chromosome pairing, DSB repair is initiated by homologous recombination but is completed by non-homologous end joining (NHEJ). Remarkably, this process yields precise repair products. Our results provide support for a recombination intermediate recently discovered in mouse meiosis, in which an oligonucleotide bound to the Spo11 protein that catalyzes DSB formation remains bound after resection. We propose that this oligonucleotide functions as a primer for fill-in synthesis to allow scarless repair by NHEJ.

genetics↗

bioRxiv2018

Genetic analysis reveals novel roles for mei-MCMs during meiotic recombination in Drosophila

Crossover formation as a result of meiotic recombination is vital for proper segregation of homologous chromosomes at the end of meiosis I. In many organisms, crossovers are generated through two crossover pathways: Class I and Class II. To ensure accurate crossover formation, meiosis-specific protein complexes regulate the degree in which each pathway is used. One such complex is the mei-MCM complex, which contains MCM (mini-chromosome maintenance) and MCM-like proteins REC (ortholog of Mcm8), MEI-217, and MEI-218, collectively called the mei-MCM complex. The mei-MCM complex genetically promotes Class I crossovers and inhibits Class II crossovers in Drosophila, but it is unclear how individual mei-MCM proteins contribute to crossover regulation. In this study, we perform genetic analyses to understand how specific regions and motifs of mei-MCM proteins contribute to Class I and II crossover formation and distribution. Our analyses show that the long, disordered N-terminus of MEI-218 is dispensable for crossover formation, and that mutations that disrupt RECs Walker A and B motifs differentially affect Class I and Class II crossover formation. In Rec Walker A mutants, Class I crossovers exhibit no change, but Class II crossovers are increased. However, in rec Walker B mutants, Class I crossovers are severely impaired, and Class II crossovers are increased. These results suggest that REC may form multiple complexes that exhibit differential REC-dependent ATP binding and hydrolyzing requirements. These results provide genetic insight into the mechanisms through which mei-MCM proteins promote Class I crossovers and inhibit Class II crossovers.

genetics↗