Biology subjects

Nguyen, A. L.

Publications and source records attributed to Nguyen, A. L..

6 recordsLinked to original sources

bioRxiv2024

Structural constraints and drivers of molecular evolution in a macromolecular complex; the kinetochore

Evolutionary theory suggests that critical cellular structures should be subject to strong purifying selection as protein changes would result in inviability. However, how this evolutionary principle relates to multi-subunit complexes remains incompletely explored. For example, the macromolecular kinetochore complex, which mediates the faithful segregation of DNA during cell division, violates the expectation of purifying selection as subsets of kinetochore proteins exhibit rapid evolution despite its critical role. Here, we developed a multi-level approach to investigate the evolutionary dynamics of the kinetochore as a model for understanding how an essential multi-protein structure can experience high rates of diversifying selection while maintaining function. Our comprehensive approach analyzed 57 kinetochore genes for signatures of purifying and diversifying selection across 70 mammalian species. Intraspecies comparisons of kinetochore gene evolution showed that members of the order Afrotheria experience higher rates of diversifying selection than other mammalian orders. Among individual loci, genes that serve regulatory functions, such as the mitotic checkpoint genes, are conserved under strong purifying selection. In contrast, the proteins that serve as the structural base of the kinetochore, including the inner and outer kinetochore, evolve rapidly across species. We also demonstrated that diversifying selection is targeted to protein regions that lack clear structural predictions. Finally, we identified sites that exhibit corresponding trends in evolution across different genes, potentially providing evidence of compensatory evolution in this complex. Together, our study of the kinetochore reveals a potential avenue by which selection can alter the genes that comprise an essential cellular complex without compromising its function.

evolutionary biology↗

bioRxiv2024

Co-Essentiality Analysis Identifies PRR12 as a Regulator of Cohesin and Genome Integrity

The cohesin complex is critical for genome regulation, relying on specialized co-factors to mediate its diverse functional activities. Here, by analyzing patterns of similar gene requirements across cell lines, we identify PRR12 as a regulator of cohesin and genome integrity. We show that PRR12 interacts with cohesin and PRR12 loss results in a reduction of nuclear-localized cohesin and an accumulation of DNA lesions. We find that different cell lines across human and mouse exhibit significant variation in their sensitivity to PRR12 loss. Unlike the modest phenotypes observed in human cell lines, PRR12 depletion in mouse cells results in substantial genome instability. Despite a modest requirement in human cell lines, mutations in PRR12 lead to severe developmental defects in human patients, suggesting context-specific roles in cohesin regulation. By harnessing comparative studies across species and cell lines, our work reveals critical insights into how cohesin is regulated across diverse cellular contexts.

cell biology↗

bioRxiv2024

Adeno-Associated Viral Tools to Trace Neural Development and Connectivity Across Amphibians

The development, evolution, and function of the vertebrate central nervous system (CNS) can be best studied using diverse model organisms. Amphibians, with their unique phylogenetic position at the transition between aquatic and terrestrial lifestyles, are valuable for understanding the origin and evolution of the tetrapod brain and spinal cord. Their metamorphic developmental transitions and unique regenerative abilities also facilitate the discovery of mechanisms for neural circuit remodeling and replacement. The genetic toolkit for amphibians, however, remains limited, with only a few species having sequenced genomes and a small number of transgenic lines available. In mammals, recombinant adeno-associated viral vectors (AAVs) have become a powerful alternative to genome modification for visualizing and perturbing the nervous system. AAVs are DNA viruses that enable neuronal transduction in both developing and adult animals with low toxicity and spatial, temporal, and cell-type specificity. However, AAVs have never been shown to transduce amphibian cells efficiently. To bridge this gap, we established a simple, scalable, and robust strategy to screen AAV serotypes in three distantly-related amphibian species: the frogs Xenopus laevis and Pelophylax bedriagae, and the salamander Pleurodeles waltl, in both developing larval tadpoles and post-metamorphic animals. For each species, we successfully identified at least two AAV serotypes capable of infecting the CNS; however, no pan-amphibian serotype was identified, indicating rapid evolution of AAV tropism. In addition, we developed an AAV-based strategy that targets isochronic cohorts of developing neurons - a critical tool for parsing neural circuit assembly. Finally, to enable visualization and manipulation of neural circuits, we identified AAV variants for retrograde tracing of neuronal projections in adult animals. Our findings expand the toolkit for amphibians to include AAVs, establish a generalizable workflow for AAV screening in non-canonical research organisms, generate testable hypotheses for the evolution of AAV tropism, and lay the foundation for modern cross-species comparisons of vertebrate CNS development, function, and evolution.

neuroscience↗

bioRxiv2023

Multimodal profiling of peripheral blood identifies proliferating circulating effector CD4+ T cells as predictors for response to integrin α4β7-blocking therapy in patients with inflammatory bowel disease

Despite the success of biological therapies in inflammatory bowel disease (IBD), patient management remains challenging due to a lack of therapy response predictors. Here we prospectively sampled two cohorts of IBD patient cohorts receiving the anti-integrin 4{beta}7 antibody vedolizumab. Samples were subjected to mass cytometry, single-cell RNA sequencing, single-cell V(D)J sequencing, serum proteomics, and multidimensional flow cytometry to comprehensively assess vedolizumab-induced immunological changes in the peripheral blood and their potential associations with treatment response. Vedolizumab induced changes in the abundance of both circulating innate and adaptive immune cell compartments and modified the T cell receptor diversity of circulating gut-homing CD4+ memory T cells. Through integration of multimodal parameters and machine learning, we identify that pretreatment activated proliferating CD4+ memory T cell abundance is associated with treatment failure, independent of clinical variables, thereby providing a reliable predictive classifier with significant implications for the personalized management of IBD patients.

immunology↗

bioRxiv2021

TRIM28-dependent SUMOylation protects the adult ovary from the male pathway

Gonadal sexual fate in mammals is determined during embryonic development and must be actively maintained in adulthood. In the mouse ovary, oestrogen receptors and FOXL2 protect ovarian granulosa cells from transdifferentiation into Sertoli cells, their testicular counterpart. However, the mechanism underlying their protective effect is unknown. Here, we show that TRIM28 is required to prevent female-to-male sex reversal of the mouse ovary after birth. We found that upon loss of Trim28, ovarian granulosa cells transdifferentiate to Sertoli cells through an intermediate cell type, different from gonadal embryonic progenitors. TRIM28 is recruited on chromatin in the proximity of FOXL2 to maintain the ovarian pathway and to repress testicular-specific genes. The role of TRIM28 in ovarian maintenance depends on its E3-SUMO ligase activity that regulates the sex-specific SUMOylation profile of ovarian-specific genes. Our study identifies TRIM28 as a key factor in protecting the adult ovary from the testicular pathway.

developmental biology↗

bioRxiv2020

Differential Requirements for the CENP-O Complex Reveal Parallel PLK1 Kinetochore Recruitment Pathways

Similar to other core biological processes, the vast majority of cell division components are essential for viability across human cell lines. However, genome-wide screens have identified a number of proteins that exhibit cell line-specific essentiality. Defining the behaviors of these proteins is critical to our understanding of complex biological processes. Here, we harness differential essentiality to reveal the contributions of the 4-subunit centromere-localized CENP-O complex, whose precise function has been difficult to define. Our results support a model in which the CENP-O complex and BUB1 act in parallel pathways to recruit a threshold level of PLK1 to mitotic kinetochores, ensuring accurate chromosome segregation. We demonstrate that targeted changes to either pathway sensitizes cells to the loss of the other component, resulting in cell-state dependent requirements. This approach also highlights the advantage of comparing phenotypes across diverse cell lines to define critical functional contributions and behaviors that could be exploited for the targeted treatment of disease.

cell biology↗