Rennan G. Moreira

Origin and dynamics of admixture in Brazilians and its effect on the pattern of deleterious mutations

Significance The EPIGEN Brazil Project is the largest Latin-American initiative to study the genomic diversity of admixed populations and its effect on phenotypes. We studied 6,487 Brazilians from three population-based cohorts with different geographic and demographic backgrounds. We identified ancestry components of these populations at a previously unmatched geographic resolution. We broadened our understanding of the African diaspora, the principal destination of which was Brazil, by revealing an African ancestry component that likely derives from the slave trade from Bantu/eastern African populations. In the context of the current debate about how the pattern of deleterious mutations varies between Africans and Europeans, we use whole-genome data to show that continental admixture is the main and complex determinant of the amount of deleterious genotypes in admixed individuals. While South Americans are underrepresented in human genomic diversity studies, Brazil has been a classical model for population genetics studies on admixture. We present the results of the EPIGEN Brazil Initiative, the most comprehensive up-to-date genomic analysis of any Latin-American population. A population-based genome-wide analysis of 6,487 individuals was performed in the context of worldwide genomic diversity to elucidate how ancestry, kinship, and inbreeding interact in three populations with different histories from the Northeast (African ancestry: 50%), Southeast, and South (both with European ancestry >70%) of Brazil. We showed that ancestry-positive assortative mating permeated Brazilian history. We traced European ancestry in the Southeast/South to a wider European/Middle Eastern region with respect to the Northeast, where ancestry seems restricted to Iberia. By developing an approximate Bayesian computation framework, we infer more recent European immigration to the Southeast/South than to the Northeast. Also, the observed low Native-American ancestry (6–8%) was mostly introduced in different regions of Brazil soon after the European Conquest. We broadened our understanding of the African diaspora, the major destination of which was Brazil, by revealing that Brazilians display two within-Africa ancestry components: one associated with non-Bantu/western Africans (more evident in the Northeast and African Americans) and one associated with Bantu/eastern Africans (more present in the Southeast/South). Furthermore, the whole-genome analysis of 30 individuals (42-fold deep coverage) shows that continental admixture rather than local post-Columbian history is the main and complex determinant of the individual amount of deleterious genotypes.

Spatial genetic structure of Coccoloba cereifera (Polygonaceae), a critically endangered microendemic species of Brazilian rupestrian fields

Coccoloba cereifera (Polygonaceae) is an extremely rare endemic shrub found exclusively in the rupestrian fields of Serra do Cipó, southeastern, Brazil. We assessed the genetic diversity and structure across the single occurrence area of C. cereifera. The genetic variation at 13 microsatellite loci was estimated from 139 individuals sampled in nine patches. The number of alleles per locus varied from two to ten; the expected and observed heterozygosity ranged from 0.324 to 0.566 and 0.337 to 0.529, respectively. Microsatellites detected low but statistically significant levels of differentiation among patches (FSTxa0=xa00.123, RSTxa0=xa00.105), whereas Mantel test results showed a weak but significant pattern of isolation by distance (r2xa0=xa00.31, Pxa0<xa00.002). Bayesian clustering indicated two subdivisions connected via admixture. Habitat heterogeneity across the drainage basin of the Rio Indequicé is likely limiting gene flow within patches of the geographically restricted population. While there is currently no evidence for a direct genetic risk to species survival, the apparent natural segregation occurring within the species could be exacerbated by future land use changes and the influx of alien species which could lead to demographic reductions in population size leading to a reduction in genetic diversity and an increase in population subdivision. We suggest that maintaining the integrity of the habitat within the small range of the species and continued monitoring of the effects of alien species would be the wisest use of management resources.

Isolation and characterization of microsatellite loci in Coccoloba cereifera (Polygonaceae), an endangered species endemic to the Serra do Cipó, Brazil.

Microsatellite primers were isolated from the microendemic and threatened species Coccoloba cereifera, a shrub known only from a small region in the Serra do Cipó, Brazil. Thirteen primer pairs amplifying perfect and imperfect microsatellite regions were tested in 40 individuals from the one known occurrence of the species. Number of alleles ranged from two to six and levels of observed heterozygosities ranged from 0.21 to 0.95. These markers will be useful for the analysis of questions concerning population genetic structure and will assist in providing information for future conservation management programmes.

Spathaspora boniae sp. nov., a D-xylose-fermenting species in the Candida albicans/Lodderomyces clade

Two yeast isolates producing asci-containing elongate ascospores with curved ends typical of the genus Spathaspora were isolated from rotting wood samples collected in an Atlantic rainforest ecosystem in Brazil. Phylogenetic analysis of the LSU rRNA gene D1/D2 domain sequences demonstrated that the strains represent a new species and placed it next to Candida blackwellae, in a clade that also contains Candida albicans and Candida dubliniensis. Other sequences of the ribosomal gene cluster supported same placementin the same clade, and a phylogenomic analysis placed this new species in an early emerging position relative to the larger C. albicans/Lodderomyces clade. One interpretation is that the genus Spathaspora is, in fact, paraphyletic. In conformity with this view, we propose the novel species Spathaspora boniae sp. nov. to accommodate the isolates. The type strain of Spathaspora boniae sp. nov. is UFMG-CM-Y306T (=CBS 13262T). The MycoBank number is MB 821297. A detailed analysis of xylose metabolism was conducted for the new species.

Targeted next-generation sequencing of glandular odontogenic cyst: a preliminary study

OBJECTIVEnGlandular odontogenic cyst (GOC) is an uncommon developmental cyst. Its molecular pathogenesis is unclear, and deep sequencing may help identify causative low-frequency variants in tumors. We investigated in GOC mutations in 50 genes commonly altered in human cancers.nnnSTUDY DESIGNnTargeted next-generation sequencing was used to interrogate a panel of approximately 2800 mutations in GOC.nnnRESULTSnSix missense single nucleotide variations (SNVs) were reported. Three SNVs (TP53 rs1042522, KDR rs1870377, and KIT rs3822214) are listed as common single-nucleotide polymorphisms at the UCSC Genome Browser. The other SNVs (PIK3CA p.Glu689Lys, PIK3CA p.Ala708Thr, and TP53 p.Leu289Phe) are predicted to have deleterious or damaging effects on proteins, but they showed very low frequency in our samples and could not be further validated by orthogonal methods.nnnCONCLUSIONSnNo pathogenic SNV was detected in this cohort of GOCs. Further studies with larger gene panels or whole exome sequencing are needed to find the genetic basis of GOC.

Next generation sequencing of oncogenes and tumor suppressor genes in odontogenic myxomas

BACKGROUNDnMutations previously considered drivers of malignant neoplasms also occur in benign tumors. From the biological perspective, the study of malignant and benign neoplasms is equally relevant. The study of rare tumors contributes to the understanding of the more common ones, as both could share the same hallmark genetic drivers. The identification of driver mutations in benign tumors is facilitated by the fact that they harbor quiet genomes. Pathogenic mutations have being described in benign epithelial odontogenic tumors, such as ameloblastomas and adenomatoid odontogenic tumors. However, the molecular pathogenesis of odontogenic myxoma (OM), a benign aggressive ectomesenchymal tumor, is still poorly characterized, precluding the development of personalized therapy. Aiming to find druggable genetic mutations, we investigated in OM mutations in 50 genes commonly mutated in cancer.nnnMETHODSnWe used targeted next-generation sequencing to interrogate over 2,800 COSMIC mutations in OM.nnnRESULTSnMissense single nucleotide variants were detected in KDR, TP53, PIK3CA, KIT, JAK3; however, these did not include pathogenic mutations.nnnCONCLUSIONnThese aggressive tumors do not harbor pathogenic mutations in genes commonly mutated in human cancers or if they do, these mutations probably occur in a low proportion of cases.

Sporadic granular cell tumours lack recurrent mutations in PTPN11, PTEN and other cancer-related genes

Granular cell tumour (GCT) is a benign nerve sheath neoplasm of unknown molecular pathogenesis. Although a skeletal muscle cell origin was initially proposed for GCT, its neural origin, derived from Schwann cells, is supported by S-100 immunopositivity.1 There are few molecular studies on oral GCT.2 GCTs have been previously described in patients with LEOPARD and Noonan syndromexa0with PTPN11 gene mutations,3–6 as well as in a patient with PTEN hamartoma tumour syndromexa0with PTEN mutation.7 Therefore, we hypothesised that mutations in these genes could be drivers of sporadic GCT pathogenesis.nnA convenience sample of six formalin-fixed, paraffin-embedded (FFPE) sporadic oral GCT was selected from the archives of the author’s institution. All samples were located at the tongue and occurred in female subjects ranging from 18 to 42 years old (median age 34 years old). The H&Exa0stained slides were analysed by two pathologists (CCG and RSG) to confirm the diagnosis (figure 1A). Tumour-enriched areas were ensured by microdissection and DNA was isolated using QIAamp DNA FFPE Tissue Kit (Qiagen, USA) and quantified by Qubit 3.0 Fluorometer (Life Technologies, USA) before next-generation sequencing (NGS) library preparation. …

EPIGEN-Brazil Initiative resources: a Latin American imputation panel and the Scientific Workflow

EPIGEN-Brazil is one of the largest Latin American initiatives at the interface of human genomics, public health, and computational biology. Here, we present two resources to address two challenges to the global dissemination of precision medicine and the development of the bioinformatics know-how to support it. To address the underrepresentation of non-European individuals in human genome diversity studies, we present the EPIGEN-5M+1KGP imputation panel-the fusion of the public 1000 Genomes Project (1KGP) Phase 3 imputation panel with haplotypes derived from the EPIGEN-5M data set (a product of the genotyping of 4.3 million SNPs in 265 admixed individuals from the EPIGEN-Brazil Initiative). When we imputed a target SNPs data set (6487 admixed individuals genotyped for 2.2 million SNPs from the EPIGEN-Brazil project) with the EPIGEN-5M+1KGP panel, we gained 140,452 more SNPs in total than when using the 1KGP Phase 3 panel alone and 788,873 additional high confidence SNPs (info score ≥ 0.8). Thus, the major effect of the inclusion of the EPIGEN-5M data set in this new imputation panel is not only to gain more SNPs but also to improve the quality of imputation. To address the lack of transparency and reproducibility of bioinformatics protocols, we present a conceptual Scientific Workflow in the form of a website that models the scientific process (by including publications, flowcharts, masterscripts, documents, and bioinformatics protocols), making it accessible and interactive. Its applicability is shown in the context of the development of our EPIGEN-5M+1KGP imputation panel. The Scientific Workflow also serves as a repository of bioinformatics resources.

The Wnt/β-catenin pathway is deregulated in cemento-ossifying fibromas

OBJECTIVEnThe molecular pathogenesis of cemento ossifying fibroma (COF) is unclear. The purpose of this study was to investigate mutations in 50 oncogenes and tumor suppressor genes, including APC and CTNNB1, in which mutations in COF have been previously reported. In addition, we assessed the transcriptional levels of the Wnt/β-catenin pathway genes in COF.nnnSTUDY DESIGNnWe used a quantitative polymerase chain reaction array to evaluate the transcriptional levels of 44 Wnt/β-catenin pathway genes in 6 COF samples, in comparison with 6 samples of healthy jaws. By using next-generation sequencing (NGS) in 7 COF samples, we investigated approximately 2800 mutations in 50 genes.nnnRESULTSnThe expression assay revealed 12 differentially expressed Wnt/β-catenin pathway genes in COF, including the upregulation of CTNNB1, TCF7, NKD1, and WNT5 A, and downregulation of CTNNBIP1, FRZB, FZD6, RHOU, SFRP4, WNT10 A, WNT3 A, and WNT4, suggesting activation of the Wnt/β-catenin signaling pathway. NGS revealed 5 single nucleotide variants: TP53 (rs1042522), PIK3 CA (rs2230461), MET (rs33917957), KIT (rs3822214), and APC (rs33974176), but none of them was pathogenic.nnnCONCLUSIONSnAlthough NGS detected no oncogenic mutation, deregulation of key Wnt/β-catenin signaling pathway genes appears to be relevant to the molecular pathogenesis of COF.

Scheffersomyces stambukii f.a., sp. nov., a d-xylose-fermenting species isolated from rotting wood

Two isolates representing a new species of Scheffersomyces were isolated from rotting wood samples collected in an Amazonian forest ecosystem in Brazil. Analysis of the sequences of the D1/D2 domains showed that this new species is phylogenetically related to Scheffersomyces NYMU 15730, a species without a formal description, and the two are in an early emerging position with respect to the xylose-fermenting subclade containing Scheffersomyces titanus and Scheffersomyces stipitis. Phylogenomic analyses using 474 orthologous genes placed the new species in an intermediary position between Scheffersomyces species and the larger genus Spathaspora and the Candida albicans/Lodderomyces clade. The novel species, Scheffersomyces stambukii f.a., sp. nov., is proposed to accommodate these isolates. The type strain of Scheffersomyces stambukii sp. nov. is UFMG-CM-Y427T (=CBS 14217T). The MycoBank number is MB 824093. In addition, we studied the xylose metabolism of this new species.