Biology subjects

Isaacson, J.

Publications and source records attributed to Isaacson, J..

4 recordsLinked to original sources

bioRxiv2026

Sleep dynamics and epileptogenesis following Kainic acid in epilepsy-susceptible (DBA/2J) and epilepsy-resistant (C57BL/6) mice

Susceptibility to epileptogenesis varies in humans and outbred mouse strains. We hypothesized that baseline sleep abnormalities increase susceptibility to epileptogenesis following Kainic acid (KA) and abnormal circadian rhythm or sleep homeostasis (SH) contribute to worse seizures in epilepsy-susceptible DBAs. Following EEG electrode implantation, C57 and DBA mice underwent repeated low-dose KA or saline treatment. Seizures, interictal spikes and sleep were examined over 8-weeks with continuous electroencephalography (EEG). Seizures were manually scored, and interictal spikes and sleep were analyzed using machine learning algorithms. Slow wave activity (SWA) was derived from non-rapid eye movement (NREM) sleep following Fourier transform, and SH was measured by the decay of SWA during sleep and its rise with preceding wakefulness. The impact of post-KA seizures on circadian rhythm was determined using Cosinor analysis. Seizures were longer and more frequent in KA-treated DBAs than C57s. Interictal spike were much greater in saline-treated DBAs than C57s. SWA across the 24-hours was lower in DBAs at baseline. KA treatment decreased REM and increased SWA activity in DBAs but not in C57s. Cosinor analysis revealed circadian rhythm abnormalities in DBAs but not in C57s. Seizures impaired SH in DBAs, with no increase in SWA with preceding wakefulness and a progressive loss of SWA decay during lights-on over the 8-week recording. These findings suggest that baseline sleep abnormalities, poorly adaptable circadian rhythms and impaired SH are associated with increased vulnerability to epileptogenesis. Therapies enhancing circadian rhythm and SH after an insult may be avenues to mitigate epileptogenesis in vulnerable populations. Significance StatementSusceptibility to spontaneous seizures after a central nervous system insult varies in humans as well as mouse models. The reasons behind the differential susceptibility are not entirely known. Here we show in a Kainic acid model, epilepsy susceptible DBA/2J mice have baseline sleep abnormalities and following Kainic acid treatment, these mice develop more frequent and longer seizures than the epilepsy-resistant C57BL/6 mice. We also show that the epilepsy-susceptible DBAs have abnormalities in circadian rhythm as well as sleep homeostasis measures compared to epilepsy-resistant C57s, which may be contributing to progression of epileptogenesis and worse seizures. Therapies targeted at enhancing sleep, circadian rhythms or sleep homeostasis may be avenues to mitigate development of spontaneous seizures after a central nervous system insult.

neuroscience↗

bioRxiv2021

The amino acid substitution affects cellular response to mistranslation

Mistranslation, the mis-incorporation of an amino acid not specified by the "standard" genetic code, occurs in all organisms. tRNA variants that increase mistranslation arise spontaneously and engineered tRNAs can achieve mistranslation frequencies approaching 10% in yeast and bacteria. Interestingly, human genomes contain tRNA variants with the potential to mistranslate. Cells cope with increased mistranslation through multiple mechanisms, though high levels cause proteotoxic stress. The goal of this study was to compare the genetic interactions and the impact on transcriptome and cellular growth of two tRNA variants that mistranslate at a similar frequency but create different amino acid substitutions in Saccharomyces cerevisiae. One tRNA variant inserts alanine at proline codons whereas the other inserts serine for arginine. Both tRNAs decreased growth rate, with the effect being greater for arginine to serine than for proline to alanine. The tRNA that substituted serine for arginine resulted in a heat shock response. In contrast, heat shock response was minimal for proline to alanine substitution. Further demonstrating the significance of the amino acid substitution, transcriptome analysis identified unique up- and downregulated genes in response to each mistranslating tRNA. Number and extent of negative synthetic genetic interactions also differed depending upon type of mistranslation. Based on the unique responses observed for these mistranslating tRNAs, we predict that the potential of mistranslation to exacerbate diseases caused by proteotoxic stress depends on the tRNA variant. Furthermore, based on their unique transcriptomes and genetic interactions, different naturally occurring mistranslating tRNAs have the potential to negatively influence specific diseases.

molecular biology↗

bioRxiv2020

Chemical-genetic interactions with the proline analog L-azetidine-2-carboxylic acid in Saccharomyces cerevisiae

Non-proteinogenic amino acids, such as the proline analog L-azetidine-2-carboxylic acid (AZC), are detrimental to cells because they are mis-incorporated into proteins and lead to proteotoxic stress. Our goal was to identify genes that show chemical-genetic interactions with AZC in Saccharomyces cerevisiae and thus also potentially define the pathways cells use to cope with amino acid mis-incorporation. Screening the yeast deletion and temperature sensitive collections, we found 72 alleles with negative synthetic interactions with AZC treatment and 12 alleles that suppress AZC toxicity. Many of the genes with negative synthetic interactions are involved in protein quality control pathways through the proteasome. Genes involved in actin cytoskeleton organization and endocytosis also had negative synthetic interactions with AZC. Related to this, the number of actin patches per cell increases upon AZC treatment. Many of the same cellular processes were identified to have interactions with proteotoxic stress caused by two other amino acid analogs, canavanine and thialysine, or a mistranslating tRNA variant that mis-incorporates serine at proline codons. Alleles that suppressed AZC-induced toxicity functioned through the amino acid sensing TOR pathway or controlled amino acid permeases required for AZC uptake.

genetics↗

bioRxiv2017

The Plateau Method for Forensic DNA SNP Mixture Deconvolution

Identification of individuals in complex DNA mixtures remains a challenge for forensic analysts. Recent advances in high throughput sequencing (HTS) are enabling analysis of DNA mixtures with expanded panels of Short Tandem Repeats (STRs) and/or Single Nucleotide Polymorphisms (SNPs). We present the plateau method for direct SNP DNA mixture deconvolution into sub-profiles based on differences in contributors DNA concentrations in the mixtures in the absence of matching reference profiles. The Plateau method can detect profiles of individuals whose contribution is as low as 1/200 in a DNA mixture (patent pending)1.

bioinformatics↗