Diet effects on mouse meiotic recombination: a warning for recombination studies

Meiotic recombination is a critical process for sexually reproducing organisms. This exchange of genetic information between homologous chromosomes during meiosis is important not only because it generates genetic diversity, but also because it is often required for proper chromosome segregation. Consequently, the frequency and distribution of crossovers are tightly controlled to ensure fertility and offspring viability. However, in many systems it has been shown that environmental factors can alter the frequency of crossover events. Two studies in flies and yeast point to nutritional status affecting the frequency of crossing over. However, this question remains unexplored in mammals. Here we test how crossover frequency varies in response to diet in Mus musculus males. We use immunohistochemistry to estimate crossover frequency in multiple genotypes under two diet treatments. Our results indicate that while crossover frequency was unaffected by diet in some strains, other strains were sensitive even to small composition changes between two common laboratory chows. Therefore, recombination is both resistant and sensitive to certain dietary changes in a strain-dependent manner and, hence, this response is genetically determined. Our study is the first to report a nutrition effect on genome-wide levels of recombination. Moreover, our work highlights the importance of controlling diet in recombination studies and may point to diet as a potential source of variability among studies, which is relevant for reproducibility.

Diet effects on mouse sperm: a warning for recombination studies

Meiotic recombination is a critical process for sexually reproducing organisms. This exchange of genetic information between homologous chromosomes during meiosis is important not only because it generates genetic diversity, but also because it is often required for proper chromosome segregation. Consequently, the frequency and distribution of crossovers are tightly controlled to ensure fertility and offspring viability. However, in many systems it has been shown that environmental factors can alter the frequency of crossover events. Two studies in flies and yeast point to nutritional status affecting the frequency of crossing over. However, this question remains unexplored in mammals. Here we test how crossover frequency varies in response to diet in Mus musculus males. We use immunohistochemistry to estimate crossover frequency in multiple genotypes under two diet treatments. Our results indicate that while crossover frequency was unaffected by diet in some strains, other strains were sensitive even to small composition changes between two common laboratory chows. Therefore, recombination is both resistant and sensitive to certain dietary changes in a strain-dependent manner and, hence, this response is genetically determined. Our study is the first to report a nutrition effect on genome-wide levels of recombination. Moreover, our work highlights the importance of controlling diet in recombination studies and may point to diet as a potential source of variability among studies, which is relevant for reproducibility.

Analytical Expressions for Voltage Controller Coefficients to Attain Desired Values of Total Harmonic Distortion and DC Link Voltage Undershoot in Power Factor Correction Rectifiers

The paper reveals analytical expressions linking the coefficients of PI controller, typically employed as voltage loop compensator of power factor correction rectifiers (PFCR), with two major performance merits (namely, total harmonic distortion (THD) of grid-side current and DC-link voltage deviation upon sudden load increase) and DC link capacitance to rated power ratio. The proposed methodology allows to concretize the commonly used "8–10Hz crossover frequency, 45 degree–70 degree phase margin" rule-of-thumb, typically utilized in application notes of commercial PFC controllers. Relations between voltage loop gain crossover frequency and phase margin as well as settling time of DC-link voltage response to a step load increase to the above mentioned performance merits are also derived in the paper. Provided design guidelines allow to precisely achieve desired values of the two mentioned performance merits and indicate the feasible range of possible DC link capacitance values. Proposed quantitative design guidelines are well-supported by experiments.

Analytical Expressions for Voltage Controller Coefficients to Attain Desired Values of Total Harmonic Distortion and DC Link Voltage Undershoot in Power Factor Correction Rectifiers

The paper reveals analytical expressions linking the coefficients of PI controller, typically employed as voltage loop compensator of power factor correction rectifiers (PFCR), with two major performance merits (namely, total harmonic distortion (THD) of grid-side current and DC-link voltage deviation upon sudden load increase) and DC link capacitance to rated power ratio. The proposed methodology allows to concretize the commonly used "8–10Hz crossover frequency, 45 degree–70 degree phase margin" rule-of-thumb, typically utilized in application notes of commercial PFC controllers. Relations between voltage loop gain crossover frequency and phase margin as well as settling time of DC-link voltage response to a step load increase to the above mentioned performance merits are also derived in the paper. Provided design guidelines allow to precisely achieve desired values of the two mentioned performance merits and indicate the feasible range of possible DC link capacitance values. Proposed quantitative design guidelines are well-supported by experiments.

Interplay between Pds5 and Rec8 in regulating chromosome axis length and crossover frequency

Meiotic chromosomes have a loop/axis architecture, with axis length determining crossover frequency. Meiosis-specific Pds5 depletion mutants have shorter chromosome axes and lower homologous chromosome pairing and recombination frequency. However, it is poorly understood how Pds5 coordinately regulates these processes. In this study, we show that only ~20% of wild-type level of Pds5 is required for homolog pairing and that higher levels of Pds5 dosage-dependently regulate axis length and crossover frequency. Moderate changes in Pds5 protein levels do not explicitly impair the basic recombination process. Further investigations show that Pds5 does not regulate chromosome axes by altering Rec8 abundance. Conversely, Rec8 regulates chromosome axis length by modulating Pds5. These findings highlight the important role of Pds5 in regulating meiosis and its relationship with Rec8 to regulate chromosome axis length and crossover frequency with implications for evolutionary adaptation.

CRISPR targeting of MEIOTIC-TOPOISOMERASE VIB-dCas9 to a recombination hotspot is insufficient to increase crossover frequency in Arabidopsis

During meiosis, homologous chromosomes pair and recombine, which can result in reciprocal crossovers that increase genetic diversity. Crossovers are unevenly distributed along eukaryote chromosomes and show repression in heterochromatin and the centromeres. Within the chromosome arms crossovers are often concentrated in hotspots, which are typically in the kilobase range. The uneven distribution of crossovers along chromosomes, together with their low number per meiosis, creates a limitation during crop breeding, where recombination can be beneficial. Therefore, targeting crossovers to specific genome locations has the potential to accelerate crop improvement. In plants, meiotic crossovers are initiated by DNA double strand breaks (DSBs) that are catalysed by SPO11 complexes, which consist of two catalytic (SPO11-1 and SPO11-2) and two non-catalytic subunits (MTOPVIB). We used the model plant Arabidopsis thaliana to target a dCas9-MTOPVIB fusion protein to the 3a crossover hotspot via CRISPR. We observed that this was insufficient to significantly change meiotic crossover frequency or pattern within 3a. We discuss the implications of our findings for targeting meiotic recombination within plant genomes.

Rapid ESKAPE Pathogens Detection Method using Tapered Dielectrophoresis Electrodes via Crossover Frequency Analysis

This paper introduces the versatile of an electrokinetic technique by using the non-uniform electric field for dielectrophoresis (DEP) application. This technique is defined as electromicrofluidics. The potential application for portable and real time detection method of Enterococcus faecium (EF), Staphylococcus aureus (SA), Klebsiella pneumoniae (KP), Acinetobacter baumannii (AB), Pseudomonas aeruginosa (PA) and Enterobacter aerogenes (EA), which are the (ESKAPE) bacteria. The MATLAB analytical modelling was used in simulating the polarisation factor and velocities of bacteria based on Clausius-Mossotti factor (CMF). The validation of CMF simulation through the DEP experimental can be quantified based on the response of alternating current (AC) voltage applied using 6 voltage peak to peak (Vp-p) to their input frequencies from 100 to 15000 kHz. The droplet method was deployed to place properly 0.2 μL of sample onto DEP microelectrode. The velocities and crossover frequency (fxo) ranges of bacteria were determined through bacteria trajectory in specific time interval monitored by microscope attached with eyepiece camera. The applied range of input frequencies from 100 to 15000 kHz at 6 Vp-p for each bacteria were successfully identified the unique ranges of frequencies response for detection application. The advantages of this works are selective with rapid capability for multidrug resistant (MDR) bacteria detection application.

The effect of the buffer zone on the maize pollen flow in mixed crops

Field experiments were carried out to study the effect of the buffer zone length and wind direction on the crossover frequency between the donor and recipient of maize pollen.