Biology subjects

MacDonald, R.

Publications and source records attributed to MacDonald, R..

4 recordsLinked to original sources

bioRxiv2026

Sexual selection does not predict long-term population trends in birds

Sexual selection is a major evolutionary force, yet its demographic consequences remain unclear. While experimental studies often report positive effects of sexual selection on traits linked to population performance, comparative studies often find null or negative associations with population persistence. One explanation for this discrepancy is that the demographic consequences of sexual selection depend on ecological context, particularly variation in mortality and fecundity. Here, we used six decades of abundance data and test whether sexual selection predicts population trends across 738 bird species from Europe and North America. We quantify sexual selection using complementary proxies capturing different components of sexual selection: mating system, sexual dichromatism, sexual size dimorphism and relative testes mass. We further assess whether the effect of sexual selection in population trends is mediated by mortality and fecundity. Across all proxies, we found no evidence that sexual selection is associated with population trends. This result is consistent across continents and robust to variation in mortality and fecundity. Our findings suggest that, despite its central role in shaping phenotypic evolution, sexual selection does not translate into consistent effects on long-term population trends at macroecological scales. More broadly, these results highlight a potential disconnect between evolutionary processes and population dynamics.

evolutionary biology↗

bioRxiv2024

Characterizing postoperative T and B cell dysfunction in cancer surgery patients, using COVID-19 as a model antigen

For most cancers, surgery is an effective intervention method for cure but, despite the benefits, many patients recur with metastatic disease. Surgery has been shown to impair immune function by causing suppression of immune cells. In this study, we used a COVID-19 immunological toolkit to answer questions regarding the effects of surgery on antigen specific CD8+ T cells and B cells by exploiting the responses to the spike protein in vaccinated cancer patients. We demonstrate that surgical stress results in a reduction in the number of CD8+ T cell that produce cytokines and B cells that secrete antibodies in response to antigen. This study will improve our understanding of surgery-induced T cell and B cell dysfunction

immunology↗

bioRxiv2019

Loss of acid sphingomyelinase ameliorates disease progression in a vertebrate model of Glucocerebrosidase deficiency

The additive effect of genetic risk variants on overall disease risk is a plausible but frequently unproven hypothesis. To test this hypothesis, we assessed the biological effect of combined glucocerebrosidase (GCase) and acid sphingomyelinase (ASM) deficiency. Variants in both glucocerebrosidase1 (GBA1) and sphingomyelinase (SMPD1) are genetic risk factors for Parkinsons disease. Unexpectedly, ASM deficiency resulted in normalized behaviour and prolonged survival in gba1-/-;smpd1-/- double-mutant zebrafish compared to gba1-/-. RNAseq-based pathway analysis confirmed a profound rescue of neuronal function and intracellular homeostasis. We identified complete reciprocal rescue of mitochondrial respiratory chain function and abolished lipid membrane oxidation in gba1-/-;smpd1-/- compared to gba1-/- or smpd1-/- as the underlying rescue mechanism. Complementing in vitro experiments demonstrated an unexpected reduction of -synuclein levels in human cell lines with combined GCase and ASM deficiency. Our study highlights the importance of functional validation for any putative interactions between genetic risk factors and their overall effect on disease-relevant mechanisms rather than readily assuming an additive effect. SummaryThe additive effect of genetic risk variants on disease risk is a popular but typically unproven hypothesis. We investigated this hypothesis mechanistically for Parkinsons disease risk factors and provide evidence of an unexpected rescue effect on neuronal function and survival.

genetics↗

bioRxiv2019

LRRK2-mediated phosphorylation of HDAC6 regulates HDAC6-cytoplasmic dynein interaction and aggresome formation.

Mutations in LRRK2 are the most common cause of dominantly inherited Parkinsons disease (PD). A proportion of LRRK2 PD exhibits Lewy pathology with accumulations of -synuclein and ubiquitin in intracellular aggregates that are indistinguishable from idiopathic PD. LRRK2 is a multi-domain protein with both GTPase and kinase activities that has been shown to affect various cellular processes including protein homeostasis, however how PD mutations in LRRK2 may lead to accumulation of ubiquitinated protein aggregates remains unclear. A main cellular pathway to remove aggregated ubiquitinated proteins is aggrephagy: the histone deacetylase HDAC6 recognizes ubiquitinated misfolded proteins and recruits them to the molecular motor cytoplasmic dynein which transports them to the perinuclear region where they are trapped in aggresomes that are subsequently removed by macroautophagy. Here we identified HDAC6 as a novel LRRK2 substrate and show that LRRK2 regulates HDAC6-dependent aggresome formation. LRRK2 directly interacted with the HDAC6 deacetylase domains via its Roc domain and phosphorylated HDAC6 on serine-22. Serine-22 phosphorylation of HDAC6 enhanced its interaction with cytoplasmic dynein and stimulated recruitment of ubiquitinated proteins to aggresomes. Knockdown or knockout of LRRK2 impaired HDAC6-mediated aggresome formation. PD mutant LRRK2 G2019S showed reduced interaction with HDAC6 and did not support aggresome formation to the same extend as wild type LRRK2. This was recapitulated in LRRK2 G2019S patient-derived iAstrocytes that showed an aggresome formation defect. In conclusion our data reveal HDAC6 as a target of LRRK2 and suggest that deregulation of HDAC6-mediated aggresome formation and aggrephagy could contribute to the pathology of PD.

neuroscience↗