Biology subjects

Brito, P. H.

Publications and source records attributed to Brito, P. H..

3 recordsLinked to original sources

bioRxiv2021

Fate transitions in Drosophila neural lineages: a single cell road map to mature neurons.

Neuron specification and maturation are essential for proper central nervous system development. However, the precise mechanisms that govern neuronal maturation remain poorly understood. Here, we use single-cell RNA sequencing, combined with a conditional genetic strategy to analyse neuronal lineages and their new born neurons in the Drosophila larval brain. A focused analysis on the transcriptional alterations that occur right after neuron generation revealed that neuron maturation starts shortly after neuronal birth, with transcription, but no translation, of mature neuronal features such as neurotransmitter (NT) genes. Using NT gene Choline acetyltransferase as an example, we show that the timings of translation initiation are not solely dependent on neuron age but are rather coordinated with the animal developmental stage. This study is the first characterization of the initial phases of neuron maturation, supporting a model where neuron maturation is coordinated with the animal developmental stage through post-transcriptional regulation of terminal effector genes.

neuroscience↗

bioRxiv2020

Differential expression between African-ancestry and White patients diagnosed with Triple-Negative Breast Cancer: EGFR, Myc, Bcl2 and β-Catenin as ancestry-associated markers

PurposeTriple-negative breast cancer (TNBC) has a higher incidence, a younger age of onset, and a more aggressive behavior in African-ancestry women. Biological disparities have been suggested as an important factor influencing the ancestry-associated TNBC discrepancy. In this study, we sought to identify ancestry-associated differential gene and protein expression between African-ancestry and White TNBC patients, controlling for patients menopause status and pathological staging at diagnosis. MethodsDifferential gene expression analyses (DGEA) were performed using RNA-sequencing data from The Cancer Genome Atlas (TCGA). Gene set enrichment analysis (GSEA) and Ingenuity Pathway Analysis (IPA), with focus on network design, were performed to highlight candidate genes for further validation through immunohistochemistry of TNBC samples from patients followed in Portugal. ResultsWith 52 African-American and 90 White TNBC patients included, TCGAs data corroborate that African-American patients have a higher TNBC incidence (28.42% vs 11.89%, p<0.0001). Particularly, premenopausal and stage II disease African-American patients also have significantly lower survival probability, comparing with White patients (log-rank p=0.019 and 0.0038, respectively). DGEA results suggest that expression profile differences are more associated with TNBC staging than with patients menopause status. Hippo pathway and cellular community gene sets are downregulated, while breast cancer gene set is upregulated in African-Americans, comparing with White TNBC patients. Furthermore, MAPK pathway gene set is upregulated when controlling for stage II disease. Due to their central role in highly scored networks resulted from IPAs network design, EGFR, Myc and Bcl2 genes were selected for further validation through immunohistochemistry. We also included {beta}-Catenin in the validation study as it is consensually reported to be required in TNBC tumorigenesis. Although patients used in the DGEA and in the immunohistochemistry experiments are geographically and culturally distinct, both groups of African-ancestry patients are mostly of western-African ancestry and, interesting, differential gene and protein expression matched. ConclusionsWe found ancestry-associated gene expression patterns between African-ancestry and White TNBCs, particularly when controlling for menopause status or staging. EGFR, Myc, Bcl2 and {beta}-catenin gene and protein differential expression matching results in distinct populations suggest these markers as being important indicators of TNBCs ancestry-associated development.

cancer biology↗

bioRxiv2020

Multiple pathways to homothallism in closely related yeast lineages in the Basidiomycota

Sexual reproduction in fungi relies on proteins with well-known functions encoded by the mating-type (MAT) loci. In the Basidiomycota, MAT loci are often bipartite, with the P/R locus encoding pheromone precursors and pheromone receptors and the HD locus encoding heterodimerizing homeodomain transcription factors (Hd1/Hd2). The interplay between different alleles of these genes within a single species usually generates at least two compatible mating types. However, a minority of species are homothallic, reproducing sexually without an obligate need for a compatible partner. Here we examine the organization and function of the MAT loci of Cystofilobasidium capitatum, a species in the order Cystofilobasidiales, which is unusually rich in homothallic species. We determined MAT gene content and organization in C. capitatum and found that it resembles a mating type of the closely related heterothallic species Cystofilobasidium ferigula. To explain the homothallic sexual reproduction observed in C. capitatum we examined HD-protein interactions in the two Cystofilobasidium species and determined C. capitatum MAT gene expression both in a natural setting and upon heterologous expression in Phaffia rhodozyma, a homothallic species belonging to a clade sister to Cystofilobasidium. We conclude that the molecular basis for homothallism in C. capitatum appears to be distinct from that previously established for P. rhodozyma. Unlike the latter species, homothallism in C. capitatum may involve constitutive activation or dispensability of the pheromone receptor and the functional replacement of the usual Hd1/Hd2 heterodimer by an Hd2 homodimer. Overall, our results suggest that homothallism evolved multiple times within the Cystofilobasidiales. ImportanceSexual reproduction is important for the biology of eukaryotes because it strongly impacts the dynamics of genetic variation. In fungi, although sexual reproduction is usually associated with the fusion between cells belonging to different individuals (heterothallism), sometimes a single individual is capable of completing the sexual cycle alone (homothallism). Homothallic species are unusually common in a fungal lineage named Cystofilobasidiales. Here we studied the genetic bases of homothallism in one species in this lineage, Cystofilobasidium capitatum, and found it to be different in several aspects when compared to another homothallic species, Phaffia rhodozyma, belonging to the genus most closely related to Cystofilobasidium. Our results strongly suggest that homothallism evolved independently in Phaffia and Cystofilobasidium, lending support to the idea that transitions between heterothallism and homothallism are not as infrequent as previously thought. Our work also helps to establish the Cystofilobasidiales as a model lineage in which to study these transitions.

microbiology↗