Scielo RSS <![CDATA[Genetics and Molecular Biology]]> http://www.scielo.br/rss.php?pid=1415-475720210003&lang=en vol. 44 num. 2 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.br/img/en/fbpelogp.gif http://www.scielo.br <![CDATA[Alpha thalassemia and alpha-MRE haplotypes in Uruguayan patients with microcytosis and hypochromia without anemia]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300101&lng=en&nrm=iso&tlng=en Abstract Alpha thalassemia is the most common genetic disorder across the world, being the α-3.7 deletion the most frequent mutation. In order to analyze the spectrum and origin of alpha thalassemia mutations in Uruguay, we obtained a sample of 168 unrelated outpatients with normal hemoglobin levels with microcytosis and hypochromia from two cities: Montevideo and Salto. The presence of α-thalassemia mutations was investigated by gap-PCR, restriction endonucleases analysis and HBA2 and HBA1 genes sequencing, whereas the alpha-MRE haplotypes were investigated by sequencing. We found 55 individuals (32.7%) with α-thalassemia mutations, 51(30.4%) carrying the -α3.7 deletion, one with the -α4.2 deletion and three having the rare punctual mutation HBA2:c.-59C&gt;T. Regarding alpha-MRE analysis, we observed a significant higher frequency of haplotype D, characteristic of African populations, in the sample with the -α3.7 deletion. These results show that α-thalassemia mutations are an important determinant of microcytosis and hypochromia in Uruguayan patients with microcytosis and hypochromia without anemia, mainly due to the -α3.7 deletion. The alpha-MRE haplotypes and the α-thalassemia mutations spectrum suggest a predominant, but not exclusive, African origin of these mutations in Uruguay. <![CDATA[Gene expression evaluation of antioxidant enzymes in patients with hepatocellular carcinoma: RT-qPCR and bioinformatic analyses]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300102&lng=en&nrm=iso&tlng=en Abstract Any condition leading to chronic liver disease is a potential oncogenic agent for hepatocellular carcinoma (HCC). Alterations in the expression of antioxidant enzymes could alter the redox balance. Our aim was to evaluate the expression of the genes GPX1, GPX4, SEP15, SELENOP, SOD1, SOD2, GSR, CAT, and NFE2L2 in patients with HCC. Differential gene expression analysis was performed using RNA-Seq data from the TCGA and GTEx databases, and RT-qPCR data from HCC patient samples. Bioinformatic analysis revealed significant differential expression in most genes. GPX4 expression was significantly increased (p=0.02), while SOD2 expression was significantly decreased (p=0.04) in experimental data. In TCGA samples, alpha-fetoprotein levels (mg/dL) were negatively correlated with the expression of SEP15 (p&lt;0.001), SELENOP (p&lt;0.001), SOD1 (p&lt;0.001), SOD2 (p&lt;0.001), CAT (p&lt;0.001), and NFE2L2 (p=0.004). Alpha-fetoprotein levels were positively correlated with the expression of GPX4 (p=0.02) and SELENOP (p=0.01) in the experimental data. Low expression of GPX1 (p=0.006), GPX4 (p=0.01), SELENOP (p=0.006), SOD1 (p=0.007), CAT (p&lt;0.001), and NFE2L2 (p&lt;0.001), and higher levels of GSR, were associated with low overall survival at 12 months. These results suggest a significant role for these antioxidant enzymes in HCC pathogenesis and severity. <![CDATA[The paradox of autophagy in Tuberous Sclerosis Complex]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300103&lng=en&nrm=iso&tlng=en Abstract Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disorder caused by germline mutations in TSC1 or TSC2 genes, which leads to the hyperactivation of the mTORC1 pathway, an important negative regulator of autophagy. This leads to the development of hamartomas in multiple organs. The variability in symptoms presents a challenge for the development of completely effective treatments for TSC. One option is the treatment with mTORC1 inhibitors, which are targeted to block cell growth and restore autophagy. However, the therapeutic effect of rapamycin seems to be more efficient in the early stages of hamartoma development, an effect that seems to be associated with the paradoxical role of autophagy in tumor establishment. Under normal conditions, autophagy is directly inhibited by mTORC1. In situations of bioenergetics stress, mTORC1 releases the Ulk1 complex and initiates the autophagy process. In this way, autophagy promotes the survival of established tumors by supplying metabolic precursors during nutrient deprivation; paradoxically, excessive autophagy has been associated with cell death in some situations. In spite of its paradoxical role, autophagy is an alternative therapeutic strategy that could be explored in TSC. This review compiles the findings related to autophagy and the new therapeutic strategies targeting this pathway in TSC. <![CDATA[Blood groups in Native Americans: a look beyond ABO and Rh]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300104&lng=en&nrm=iso&tlng=en Abstract The study presents comparisons between blood group frequencies beyond ABO and Rh blood systems in Native American populations and previously published data from Brazilian blood donors. The frequencies of Diego (c.2561C&gt;T, rs2285644), Kell (c.578C&gt;T, rs8176058), Duffy (c.125A&gt;G, rs12075, c.1−67T&gt;C, rs2814778) and Kidd (c.838A&gt;G, rs1058396) variants in Kaingang (n=72) and Guarani (n=234) populations from Brazil (1990-2000) were obtained and compared with data from these populations sampled during the 1960s and with individuals of different Brazilian regions. Data showed high frequencies of DI*01 and FY*01 alleles: 11.8% and 57.6% in Kaingang and 6.8% and 75.7% in Guarani groups, respectively. The main results indicated: (1) reduction in genetic distance over time of Kaingang and Guarani in relation to other Brazilian populations is suggestive of ongoing admixture; (2) significant differences in some frequencies of blood group markers (especially Diego, Kidd and Duffy) in relation to Native Americans and individuals from different geographical regions of Brazil. Our study shows that the frequency of red blood cell polymorphisms in two Native American groups is very different from that of blood donors, when we evaluated blood groups different from ABO and Rh systems, suggesting that a better ethnic characterization of blood unit receptors is necessary. <![CDATA[Structural analysis of new compound heterozygous variants in <em>PEPD</em> gene identified in a patient with Prolidase Deficiency diagnosed by exome sequencing]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300105&lng=en&nrm=iso&tlng=en Abstract Prolidase Deficiency (PD) is an autosomal recessive rare disorder caused by loss or reduction of prolidase enzymatic activity due to variants in the PEPD gene. PD clinical features vary among affected individuals: skin ulcerations, recurrent infections, and developmental delay are common. In this study, we describe a 16-year-old boy with a mild PD phenotype comprising chronic eczema, recurrent infections and elevated IgE. Whole exome sequencing analysis revealed three PEPD variants: c.575T&gt;C p.(Leu192Pro) inherited from the mother, and c.692_694del p.(Tyr231del) and c.1409G&gt;A p.(Arg470His), both inherited from the father. The variant p.(Tyr231del) has been previously characterized by high-resolution X-ray structure analysis as altering protein dynamics/flexibility. In order to study the effects of the other two prolidase variants, we performed site directed mutagenesis purification and crystallization studies. A high-resolution X-ray structure could only be obtained for the p.(Arg470His) variant, which showed no significant structural differences in comparison to WT prolidase. On the other hand, the p.(Leu192Pro) variant led to significant protein destabilization. Hence, we conclude that the maternal p.(Leu192Pro) variant was likely causally associated with the proband´s disease, together with the known pathogenic paternal variant p.(Tyr231del). Our results demonstrated the utility of exome sequencing to perform diagnosis in PD cases with mild phenotype. <![CDATA[miR-34a regulates phenotypic modulation of vascular smooth muscle cells in intracranial aneurysm by targeting CXCR3 and MMP-2]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300106&lng=en&nrm=iso&tlng=en Abstract MicroRNAs (miRNAs) dysregulation is tightly related to diseases including tumor, neuro disease and cardiovascular disease. In this study, we investigated the potential biological effects of miR-34a and its target CXCR3 in phenotypic modulation of vascular smooth muscle cells (VSMCs) of intracranial aneurysms (IAs). MiR-34a was found to be down-regulated in IAs patients tested by Real-time PCR and decreased in GEO data. Meanwhile, our study also showed miR-34a inhibited matrix metalloproteinases (MMPs) and migration of VSMCs. Besides, CXCR3 is a direct target of miR-34a identified via luciferase assay. CXCR3 showed inhibitory effect on SM-MHC, SM22 while promoted MMPs expression, cell proliferation and migration in VSMCs. MiR-34a reversed the effect of CXCR3 in VSMCs. In addition, MMP-2 is a competitive endogenous RNA (ceRNA) of CXCR3 sharing common miR-34a target. CXCR3 increased MMP-2 level through competitive endogenous RNA regulation by sponging endogenous miR-34a. In conclusion, miR-34a is down-regulated in IAs while CXCR3 is the direct target of miR-34a that regulates phenotypic modulation of VSMCs. CXCR3 increased MMP-2 level through competitive endogenous RNA regulation by sharing common miR-34a targets. <![CDATA[Increased prevalence of the CVD-associated <em>ANRIL</em> allele in the Roma/Gypsy population in comparison with the majority Czech population]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300107&lng=en&nrm=iso&tlng=en Abstract Cardiovascular disease (CVD) is a major cause of death around the world, with highest prevalence reported in minority Roma/Gypsy populations living in developed countries. Whether these differences are caused by unhealthy lifestyles or genetic factors remain unknown. The aim of our study was to examine the genotype frequencies of the rs10757274 polymorphism in the 9p.21 locus within ANRIL (antisense non-coding RNA in the INK4 locus), a long non-coding RNA located in the vicinity of the CDKN2A/2B inhibitors loci. ANRIL is understood to be the strongest genetic determinant of CVD in Caucasians. Using PCR-RFLP, we analysed the ANRIL rs10757274 polymorphism in 298 non-Roma (50% male) and 302 Roma/Gypsy (50% male) adult (39.5 ± 15.1 years and 39.2 ± 12.8 years, respectively) subjects. We found that frequencies of the ANRIL GG, GA and AA genotypes were 20.1%, 52.4% and 27.5% in the majority population and 32.9%, 47.9% and 19.2% in Roma/Gypsy subjects, respectively. The distribution of genotypes was deemed significantly different at P &lt; 0.001. Within the Roma/Gypsy population, we detected increased prevalence of the CVD-associated GG genotype. Increased prevalence of CVD among Roma/Gypsies subjects may be significantly linked to genetic background. <![CDATA[Association of <em>TYK2</em> polymorphisms with autoimmune diseases: A comprehensive and updated systematic review with meta-analysis]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300108&lng=en&nrm=iso&tlng=en Abstract Autoimmune diseases are characterized by the loss of self-tolerance, leading to immune-mediated tissue destruction and chronic inflammation. Tyrosine kinase 2 (TYK2) protein plays a key role in immunity and apoptosis pathways. Studies have reported associations between single nucleotide polymorphisms (SNPs) in the TYK2 gene and autoimmune diseases; however, results are still inconclusive. Thus, we conducted a systematic review followed by meta-analysis. A literature search was performed to find studies that investigated associations between TYK2 SNPs and autoimmune diseases (multiple sclerosis, systemic lupus erythematosus, Crohn’s disease, ulcerative colitis, psoriasis, rheumatoid arthritis, type 1 diabetes, and inflammatory bowel disease). Pooled odds ratios (OR) with 95 % CI were calculated using random (REM) or fixed (FEM) effects models in the Stata 11.0 Software. Thirty-four articles were eligible for inclusion in the meta-analyses, comprising 9 different SNPs: rs280496, rs280500, rs280523, rs280519, rs2304256, rs12720270, rs12720356, rs34536443, and rs35018800. Meta-analysis results showed the minor alleles of rs2304256, rs12720270, rs12720356, rs34536443, and rs35018800 SNPs were associated with protection against autoimmune diseases. Moreover, the A allele of the rs280519 SNP was associated with risk for systemic lupus erythematosus. Our meta-analyses demonstrated that the rs2304256, rs12720270, rs12720356, rs34536443, rs35018800, and rs280519 SNPs in the TYK2 gene are associated with different autoimmune diseases. <![CDATA[Cytogenetic and genetic data support <em>Crossodactylus aeneus</em> Müller, 1924 as a new junior synonym of <em>C. gaudichaudii</em> Duméril and Bibron, 1841 (Amphibia, Anura)]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300201&lng=en&nrm=iso&tlng=en Abstract The nominal anuran species Crossodactylus gaudichaudii Duméril and Bibron, 1841 and Crossodactylus aeneus Müller, 1924 are indistinguishable based on adult and larval morphology, being subject of taxonomic doubts. Here, we describe the karyotypes of C. gaudichaudii and C. aeneus, using classical and molecular cytogenetic markers. In addition, we used sequences of the H1 mitochondrial DNA to infer their phylogenetic relationships by Maximum Likelihood (ML) and Maximum Parsimony (MP) approaches and species delimitation test (by bPTP approach). The karyotypic data do not differentiate C. gaudichaudii and C. aeneus in any of the chromosome markers assessed. In both phylogenetic analyses, C. gaudichaudii and C. aeneus were recovered into a strongly supported clade. The species delimitation analysis recovered the specimens assigned to C. gaudichaudii and C. aeneus as a single taxonomic unit. Taken the cytogenetic and genetic results together with previous studies of internal and external morphology of tadpoles and biacoustic pattern, C. gaudichaudii and C. aeneus could not be differentiated, which supports the hypothesis that they correspond to the same taxonomic unit, with C. aeneus being a junior synonym of C. gaudichaudii. <![CDATA[Establishment of rapid and non-invasive protocols to identify B-carrying individuals of <em>Psalidodon paranae</em>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300202&lng=en&nrm=iso&tlng=en Abstract Supernumerary, or B, chromosomes are present in several eukaryotes, including characid fish of the genus Psalidodon. Notably, Psalidodon paranae carries the most studied B chromosome variant, a macro-B chromosome. The origin of this element was determined to be an isochromosome; however, data regarding its inheritance remain unavailable due to methodological barriers such as the lack of an efficient, non-invasive, and rapid protocol for identifying B-carrying individuals that would enable the design of efficient crossing experiments. Thus, in this study, we primarily aimed was to develop two non-invasive and fast (approximately 2 h) methods to identify the presence of B chromosomes in live specimens of P. paranae based on satellite DNA (satDNA) sequences known to be present in this element. The methods include fluorescence in situ hybridization in interphase nuclei and relative gene quantification of satDNAs using quantitative polymerase chain reaction. Our results reveal the efficiency of quick-fluorescence in situ hybridization and quantitative polymerase chain reaction for identifying B-carrying individuals using the proposed satDNA sequences and open up new possibilities to study B chromosomes. <![CDATA[Genetic structure of the endangered Irrawaddy dolphin (<em>Orcaella brevirostris</em>) in the Gulf of Thailand]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300203&lng=en&nrm=iso&tlng=en Abstract The Irrawaddy dolphin (Orcaella brevirostris) is an endangered, small cetacean species which is widely distributed in rivers, estuaries, and coastal waters throughout the tropical and subtropical Indo-Pacific. Despite the extensive distribution of this species, little is known of individual movements or genetic exchange among regions in Thailand. Here, we evaluate the genetic diversity and genetic structure of O. brevirostris in the eastern, northern and western Gulf of Thailand, and Andaman Sea. Although phylogenetic relationships and network analysis based on 15 haplotypes obtained from 32 individuals reveal no obvious divergence, significant genetic differentiation in mitochondrial DNA (overall FST = 0.226, P &lt; 0.001; ΦST = 0.252, P &lt; 0.001) is apparent among regions. Of 18 tested microsatellite loci, 10 are polymorphic and successfully characterized in 28 individuals, revealing significant genetic differentiation (overall FST = 0.077, P &lt; 0.05) among the four sampling sites. Structure analysis reveals two inferred genetic clusters. Additionally, Mantel analysis demonstrates individual-by-individual genetic distances and geographic distances follow an isolation-by-distance model. We speculate that the significant genetic structure of O. brevirostris in Thailand is associated with a combination of geographical distribution patterns, environmental and anthropogenic factors, and local adaptations. <![CDATA[Cytotaxonomy of <em>Gallinula melanops</em> (Gruiformes, Rallidae): Karyotype evolution and phylogenetic inference]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300204&lng=en&nrm=iso&tlng=en Abstract Although Rallidae is the most diverse family within Gruiformes, there is little information concerning the karyotype of the species in this group. In fact, Gallinula melanops, a species of Rallidae found in Brazil, is among the few species studied cytogenetically, but only with conventional staining and repetitive DNA mapping, showing 2n=80. Thus, in order to understand the karyotypic evolution and phylogeny of this group, the present study aimed to analyze the karyotype of G. melanops by classical and molecular cytogenetics, comparing the results with other species of Gruiformes. The results show that G. melanops has the same chromosome rearrangements as described in Gallinula chloropus (Clade Fulica), including fission of ancestral chromosomes 4 and 5 of Gallus gallus (GGA), beyond the fusion between two of segments resultants of the GGA4/GGA5, also fusions between the chromosomes GGA6/GGA7. Thus, despite the fact that some authors have suggested the inclusion of G. melanops in genus Porphyriops, our molecular cytogenetic results confirm its place in the Gallinula genus. <![CDATA[Cytogenetic and molecular characteristics of <em>Potamotrygon motoro</em> and <em>Potamotrygon</em> sp. (Chondrichthyes, Myliobatiformes, Potamotrygonidae) from the Amazon basin: Implications for the taxonomy of the genus]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300205&lng=en&nrm=iso&tlng=en Abstract The chromosomes of two freshwater stingrays, Potamotrygon motoro and Potamotrygon sp., from the Amazon River basin in Brazil were investigated using integrated molecular (cytochrome c oxidase subunit 1) and cytogenetic analyses. Potamotrygon motoro presented intraspecific variation in the diploid number, with 2n=66 in the females and 2n=65 in the males, while Potamotrygon sp. had a karyotype with 66 chromosomes, in both sexes. The C-banding revealed the presence of heterochromatic blocks accumulated in the centromeric region of all the chromosomes in both species. The FISH assays with 18S DNA probes highlighted the terminal region of three or four chromosome pairs in P. motoro and seven chromosomes in Potamotrygon sp. The rDNA 5S sequences were found in only one chromosomal pair in both species. The interspecific genetic distance based on the COI sequences, between P. motoro and Potamotrygon sp. from Amazon River was 10.8%, while that between the Amazonian P. motoro and Potamotrygon amandae from the Paraná River was 2.2%, and the genetic distance between Potamotrygon sp. and P. amandae was 11.8%. In addition to the new insights on the cytogenetics of the study species, the results of the present study confirmed the existence of heteromorphic sex-linked chromosomes in P. motoro. <![CDATA[TLR4 and TLR8 variability in Amazonian and West Indian manatee species from Brazil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300206&lng=en&nrm=iso&tlng=en Abstract Amazonian (Trichechus inunguis) and West Indian (Trichechus manatus) manatees are aquatic mammals vulnerable to extinction found in the Amazon basin and the coastal western Atlantic. Toll-like receptors (TLR) play a key role in recognizing pathogen-associated molecular patterns using leucine-rich repeats (LRRs). We described the diversity of TLR4 and TLR8 genes in these two species of manatee. Amazonian manatee showed seven SNPs in TLR4 and the eight in TLR8, while West Indian manatee shared four and six of those SNPs, respectively. In our analysis, TLR4 showed one non-conservative amino acid replacement substitution in LRR7 and LRR8, on the other hand, TLR8 was less variable and showed only conserved amino acid substitutions. Selection analysis showed that only one TLR4 site was subjected to positive selection and none in TLR8. TLR4 in manatees did not show any evidence of convergent evolution compared to species of the cetacean lineage. Differences in TLR4 and TLR8 polymorphism may be related to distinct selection by pathogens, population reduction of West Indian manatees, or an expected consequence of population expansion in Amazonian manatees. Future studies combining pathogen association and TLR polymorphism may clarify possible roles of these genes and be used for conservation purposes of manatee species. <![CDATA[Molecular cytogenetic analysis and the establishment of a cell culture in the fish species <em>Hollandichthys multifasciatus</em> (Eigenmann & Norris, 1900) (Characiformes, Characidae)]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300207&lng=en&nrm=iso&tlng=en Abstract Hollandichthys is a fish genus of the family Characidae that was until recently considered to be monotypic, with cytogenetic, morphological, and molecular data being restricted to a few local populations. In the present study, the karyotype of a population of Hollandichthys multifasciatus was analyzed using classical and molecular cytogenetic approaches for the investigation of potential markers that could provide new perspectives on the cytotaxonomy. H. multifasciatus presented a diploid number of 2n=50 chromosomes and a karyotype formula of 8m+10sm+32st. A single pair of chromosomes presented Ag-NORs signals, which coincided with the 18S rDNA sites visualized by FISH, whilst the 5S rDNA sequences were mapped in two chromosome pairs. The distribution of the U snRNA genes was mapped on the Hollandichthys chromosomes for the first time, with the probes revealing the presence of the U1 snDNA on the chromosomes of pair 20, U2 on pairs 6 and 19, U4 on pair 16, and U6 on the chromosomes of pair 11. The results of the present study indicated karyotypic differences in comparison with the other populations of H. multifasciatus studied previously, reinforcing the need for further research to identify isolated populations or the potential existence of cryptic Hollandichthys species. <![CDATA[Molecular tools confirm natural <em>Leishmania</em> (<em>Viannia</em>) <em>guyanensis/L.</em> (<em>V.</em>) <em>shawi</em> hybrids causing cutaneous leishmaniasis in the Amazon region of Brazil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300208&lng=en&nrm=iso&tlng=en Abstract Seven isolates from patients with American cutaneous leishmaniasis in the Amazon region of Brazil were phenotypically suggestive of Leishmania (Viannia) guyanensis/L. (V.) shawi hybrids. In this work, two molecular targets were employed to check the hybrid identity of the putative hybrids. Heat shock protein 70 (hsp70) gene sequences were analyzed by three different polymerase chain reaction (PCR) approaches, and two different patterns of inherited hsp70 alleles were found. Three isolates presented heterozygous L. (V.) guyanensis/L. (V.) shawi patterns, and four presented homozygous hsp70 patterns involving only L. (V.) shawi alleles. The amplicon sequences confirmed the RFLP patterns. The high-resolution melting method detected variant heterozygous and homozygous profiles. Single-nucleotide polymorphism genotyping/cleaved amplified polymorphic site analysis suggested a higher contribution from L. (V.) guyanensis in hsp70 heterozygous hybrids. Additionally, PCR-RFLP analysis targeting the enzyme mannose phosphate isomerase (mpi) gene indicated heterozygous and homozygous cleavage patterns for L. (V.) shawi and L. (V.) guyanensis, corroborating the hsp70 findings. In this communication, we present molecular findings based on partial informative regions of the coding sequences of hsp70 and mpi as markers confirming that some of the parasite strains from the Brazilian Amazon region are indeed hybrids between L. (V.) guyanensis and L. (V.) shawi. <![CDATA[Identification and characterization of repetitive DNA in the genus <em>Didelphis</em> Linnaeus, 1758 (Didelphimorphia, Didelphidae) and the use of satellite DNAs as phylogenetic markers]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300501&lng=en&nrm=iso&tlng=en Abstract Didelphis species have been shown to exhibit very conservative karyotypes, which mainly differ in their constitutive heterochromatin, known to be mostly composed by repetitive DNAs. In this study, we used genome skimming data combined with computational pipelines to identify the most abundant repetitive DNA families of Lutreolina crassicaudata and all six Didelphis species. We found that transposable elements (TEs), particularly LINE-1, endogenous retroviruses, and SINEs, are the most abundant mobile elements in the studied species. Despite overall similar TE proportions, we report that species of the D. albiventris group consistently present a less diverse TE composition and smaller proportions of LINEs and LTRs in their genomes than other studied species. We also identified four new putative satDNAs (sat206, sat907, sat1430 and sat2324) in the genomes of Didelphis species, which show differences in abundance and nucleotide composition. Phylogenies based on satDNA sequences showed well supported relationships at the species (sat1430) and groups of species (sat206) level, recovering topologies congruent with previous studies. Our study is one of the first attempts to present a characterization of the most abundant families of repetitive DNAs of Lutreolina and Didelphis species providing insights into the repetitive DNA composition in the genome landscape of American marsupials. <![CDATA[Fantastic databases and where to find them: Web applications for researchers in a rush]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300801&lng=en&nrm=iso&tlng=en Abstract Public databases are essential to the development of multi-omics resources. The amount of data created by biological technologies needs a systematic and organized form of storage, that can quickly be accessed, and managed. This is the objective of a biological database. Here, we present an overview of human databases with web applications. The databases and tools allow the search of biological sequences, genes and genomes, gene expression patterns, epigenetic variation, protein-protein interactions, variant frequency, regulatory elements, and comparative analysis between human and model organisms. Our goal is to provide an opportunity for exploring large datasets and analyzing the data for users with little or no programming skills. Public user-friendly web-based databases facilitate data mining and the search for information applicable to healthcare professionals. Besides, biological databases are essential to improve biomedical search sensitivity and efficiency and merge multiple datasets needed to share data and build global initiatives for the diagnosis, prognosis, and discovery of new treatments for genetic diseases. To show the databases at work, we present a a case study using ACE2 as example of a gene to be investigated. The analysis and the complete list of databases is available in the following website &lt;https://kur1sutaru.github.io/fantastic_databases_and_where_to_find_them/&gt;. <![CDATA[Erratum]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572021000300901&lng=en&nrm=iso&tlng=en Abstract Public databases are essential to the development of multi-omics resources. The amount of data created by biological technologies needs a systematic and organized form of storage, that can quickly be accessed, and managed. This is the objective of a biological database. Here, we present an overview of human databases with web applications. The databases and tools allow the search of biological sequences, genes and genomes, gene expression patterns, epigenetic variation, protein-protein interactions, variant frequency, regulatory elements, and comparative analysis between human and model organisms. Our goal is to provide an opportunity for exploring large datasets and analyzing the data for users with little or no programming skills. Public user-friendly web-based databases facilitate data mining and the search for information applicable to healthcare professionals. Besides, biological databases are essential to improve biomedical search sensitivity and efficiency and merge multiple datasets needed to share data and build global initiatives for the diagnosis, prognosis, and discovery of new treatments for genetic diseases. To show the databases at work, we present a a case study using ACE2 as example of a gene to be investigated. The analysis and the complete list of databases is available in the following website &lt;https://kur1sutaru.github.io/fantastic_databases_and_where_to_find_them/&gt;.