Biology subjects

Langston, R.

Publications and source records attributed to Langston, R..

6 recordsLinked to original sources

bioRxiv2025

Single cell RNA sequencing reveals limited effects of Lrrk2 genotype in a mouse model of acute CNS inflammation

BACKGROUNDPrevious data implicates neuroinflammation in the pathogenesis of Parkinsons disease (PD). Of the genes associated with PD, Leucine rich repeat kinase 2 (LRRK2) has previously been proposed to play a role in neuroinflammation. However, the extent to which LRRK2 is involved in endogenous inflammatory signaling is unclear. OBJECTIVETo examine whether endogenous mutations in LRRK2 affect responses to neuroinflammation in vivo. METHODSWe injected cohorts of mice with knock-in mutations in Lrrk2, homologous to those causing human PD, with a single intrastriatal injection of lipopolysaccharide (LPS) or control. We used single cell RNA-Sequencing to examine cell type specific responses to treatment and genotype and validated key results with orthogonal approaches. RESULTSWe found that our chosen paradigm of acute LPS exposure evokes robust transcriptional changes consistent with a multicellular neuroinflammatory response. We also found evidence of peripheral immune cell recruitment into the brain and interaction with brain-resident microglia. However, the transcriptional effects of Lrrk2 mutations were limited to small numbers of genes, including down regulation of gene ontogeny terms related to lysosomes, in microglia. CONCLUSIONSOur data clearly demonstrate that many cells in the brain respond to a single inflammatory insult with strong transcriptional responses and that, even in a model focused on CNS injection, there is interaction between peripheral and central immune cells. In contrast, the quantitative effects of Lrrk2 mutations are modest at the transcriptional level, demonstrating that additional studies are needed to clarify whether Lrrk2 mutations affect neuroinflammation in an endogenous context.

neuroscience↗

bioRxiv2025

The shortest telomere in telomerase-negative cells triggers replicative senescence at a critical threshold length and also fuels genomic instability

In the absence of telomerase, telomere shortening triggers replicative senescence, a tumor suppressor mechanism that is also associated with oncogenic genomic instability. Yet, the precise mechanism that connects these seemingly opposing forces remains poorly understood. To directly study the complex interplay between senescence, telomere dynamics, and genomic instability, we developed a system in Saccharomyces cerevisiae to generate and track telomeres of precise length in the absence of telomerase. Using single-telomere and single-cell analyses combined with mathematical modeling, we identify a threshold length at which telomeres switch into dysfunction. A single shortest telomere below the threshold length is necessary and sufficient to trigger the onset of replicative senescence in a majority of cells. At population level, fluctuation assays establish that rare genomic instability arises predominantly in cis to the shortest telomere as Pol32-dependent non-reciprocal translocations that result in re-elongation of the shortest telomere and likely transient escape from senescence. The switch of the shortest telomere into dysfunction and subsequent processing in telomerase-negative cells thus serves as the mechanistic link between replicative senescence onset, genomic instability and the initiation of post-senescence survival.

molecular biology↗

bioRxiv2022

Comparison of Two Budding Yeast Disome Model Systems: Similarities, Difference, and Conflict

Here we define chromosome instability as the propensity of error-prone DNA repair and maintenance to generate chromosomal alterations known as gross chromosomal rearrangements (GCR), which can be found in a variety of forms in a variety of diseased cells. Insights and study of GCRs and chromosome instability can be gained through experimentation using a disome system (a haploid strain with an extra copy of one chromosome). Chromosome instability has previously been investigated and identified in a budding yeast ChrVII disome model. Here we extend and compare the study of chromosome instability using a similar ChrV disome system. As with the ChrVII disome system, cells containing unstable chromosomes form a distinctive "sectored" colony phenotype and through the use of genetic markers, we also find evidence of allelic recombination and chromosome loss. We also found the same DNA integrity pathways suppress chromosome instability and that unstable chromosomes are not generated through homologous recombination (HR) or non-homologous end-joining (NHEJ), similar to the ChrVII system. But in contrast and more interestingly, we did not detect any altered ChrV sizes, which conflicts with a previous ChrVII disome study where it was thought that unstable chromosomes often resulted in altered sizes. We also discovered a distinct increase in frequency of instability in the ChrV system compared to the ChrVII system.

molecular biology↗

bioRxiv2021

Association of a common genetic variant with Parkinson's disease is propagated through microglia

Studies of the genetic basis of Parkinsons disease (PD) have identified many disease-associated genetic variants, but the mechanisms linking variants to pathogenicity are largely unknown. PD risk is attributed to both coding mutations in the Leucine-rich repeat kinase 2 (LRRK2) gene and to common non-coding variation upstream of the LRRK2 locus. Here we show that the influence of genotype at non-coding variant rs76904798 on LRRK2 expression is propagated specifically through microglia, in contrast to evaluations based on general rather than genotype-dependent expression. We find evidence of microglia-specific regulatory regions that may modulate LRRK2 expression using single nuclei sequencing analyses of human frontal cortex and confirm these results in a human induced pluripotent stem cell-derived microglia model. Our study demonstrates that cell type is an important consideration in interrogation of the role of non-coding variation in disease pathogenesis.

neuroscience↗

bioRxiv2019

Loss of Cdc13 causes genome instability by deficiency in replication-dependent telomere capping

In budding yeast, Cdc13, Stn1, and Ten1 form a telomere binding heterotrimer dubbed CST. Here we investigate the role of Cdc13/CST in maintaining genome stability, using a Chr VII disome system that can generate recombinants, loss, and enigmatic unstable chromosomes. In cells expressing a temperature sensitive CDC13 allele, cdc13F684S, unstable chromosomes frequently arise due to problems in or near a telomere. Hence, when Cdc13 is defective, passage through S phase causes Exo1-dependent ssDNA and unstable chromosomes, which then are the source for whole chromosome instability events (e.g. recombinants, chromosome truncations, dicentrics, and/or loss). Specifically, genome instability arises from a defect in Cdc13s replication-dependent telomere capping function, not Cdc13s putative post-replication telomere capping function. Furthermore, the unstable chromosomes form without involvement of homologous recombination nor non-homologous end joining. Our data suggest that a Cdc13/CST defect in semi-conservative replication near the telomere leads to ssDNA and unstable chromosomes, which then are lost or subject to complex rearrangements. This system defines a links between replication-dependent chromosome capping and genome stability in the form of unstable chromosomes.

genetics↗

bioRxiv2019

Genetic modifiers of risk and age at onset in GBA associated Parkinson disease and Lewy body dementia

Parkinsons disease (PD) is a genetically complex disorder. Multiple genes have been shown to contribute to the risk of PD, and currently 90 independent risk variants have been identified by genome-wide association studies. Thus far, a number of genes (including SNCA, LRRK2, and GBA) have been shown to contain variability across a spectrum of frequency and effect, from rare, highly penetrant variants to common risk alleles with small effect sizes. Variants in GBA, encoding the enzyme glucocerebrosidase, are associated with Lewy body diseases such as PD and Lewy body dementia (LBD). These variants, which reduce or abolish enzymatic activity, confer a spectrum of disease risk, from 1.4- to >10-fold. An outstanding question in the field is what other genetic factors that influence GBA-associated risk for disease, and whether these overlap with known PD risk variants.\n\nUsing multiple, large case-control datasets, totalling 217,165 individuals (22,757 PD cases, 13,431 PD proxy cases, 622 LBD cases and 180,355 controls), we identified 1,772 PD cases, 711 proxy cases and 7,624 controls with a GBA variant (p.E326K, p.T369M or p.N370S). We performed a genome-wide association study and analysed the most recent PD-associated genetic risk score to detect genetic influences on GBA risk and age at onset. We attempted to replicate our findings in two independent datasets, including the personal genetics company 23andMe, Inc. and whole-genome sequencing data. Our analysis showed that the overall PD genetic risk score modifies risk for disease and decreases age at onset in carriers of GBA variants. Notably, this effect was consistent across all tested GBA risk variants. Dissecting this signal demonstrated that variants in close proximity to SNCA and CTSB (encoding cathepsin B) are the most significant contributors. Risk variants in the CTSB locus were identified to decrease mRNA expression of CTSB. Additional analyses suggest a possible genetic interaction between GBA and CTSB and GBA p.N370S neurons were shown to have decreased Cathepsin B expression compared to controls. These data provide a genetic basis for modification of GBA-associated PD risk and age at onset and demonstrate that variability at genes implicated in lysosomal function exerts the largest effect on GBA associated risk for disease. Further, these results have important implications for selection of GBA carriers for therapeutic interventions.

genetics↗