Sergio Russo Matioli

A key factor contributing to the success of Darwin and Wallace’s theory of biological evolution by natural selection was its population-level perspective. This conceptual framework was not immediately adopted, largely due to the enduring intuitive appeal of Lamarckian ideas. The development of genetics during the twentieth century provided compelling evidence that effectively excluded Lamarckian mechanisms from the mainstream understanding of evolutionary processes. Some naturalists, however, proposed mechanisms by which environmental factors could influence genotypes in shaping phenotypes, later attributed to chemical modifications of DNA or chromosomal proteins, among others. The field of population epigenetics emerged with the aim of extending the well-established discipline of population genetics by incorporating such phenomena. This review seeks to provide a historical background on this subject and to examine how advances in both contemporary epigenetics and population epigenetics have been achieved, as well as their implications for the study of human diseases, particularly regarding their contribution to the phenomenon of missing heritability. Because there are major taxonomic differences in the transgenerational inheritance of epigenetic modifications, the potential effects of epigenetic architecture on phenotypes of interest also differ, as in the case of mammals and, in particular, humans.

O termo “epistasia” refere-se à interação entre genótipos de genes (lócus) diferentes (interação interlócus), em que a expressão de um lócus depende do genótipo de outro lócus de forma não independente. Esse conceito pode ser aplicado a dois domínios: um de natureza fisiológica/bioquímica, voltado para a maneira como os produtos gênicos interagem em processos biológicos. O segundo é de caráter quantitativo e mais matemático, referindo-se aos efeitos do fenômeno sobre um fenótipo quantitativo. Ambas as definições são valiosas e válidas em seus respectivos domínios, oferecendo perspectivas diferentes sobre o conceito de epistasia. Neste artigo abordaremos as diferentes definições de epistasia e sua importância, incluindo exemplos. O objetivo do artigo é oferecer subsídios para a discussão do fenômeno no ensino superior.

Background: Sphingomyelinase D is the main toxin present in the venom ofLoxoscelesspiders. Several isoforms present in these venoms can be structurally classified in two groups. Class I Sphingomyelinase D contains a single disulphide bridge and variable loop. Class II Sphingomyelinase D presents an additional intrachain disulphide bridge that links a flexible loop with a catalytic loop. These classes exhibit differences in their toxic potential. In this paper we address the distribution of the structural classes of SMase D within and among species of spiders and also their evolutionary origin by means of phylogenetic analyses. We also conducted tests to assess the action of natural selection in their evolution combined to structural modelling of the affected sites.Results: The majority of the Class I enzymes belong to the same clade, which indicates a recent evolution from a single common ancestor. Positively selected sites are located on the catalytic interface, which contributes to a distinct surface charge distribution between the classes. Sites that may prevent the formation of an additional bridge were found in Class I enzymes.Conclusions: The evolution of Sphingomyelinase D has been driven by natural selection toward an increase in noxiousness, and this might help explain the toxic variation between classes.

Interleukin (IL)-21 and protein tyrosine phosphatase non-receptor 22 (PTPN22) regulate lymphocyte function and have been implicated in the pathogenesis of autoimmune diabetes. We sequenced the proximal promoter of the IL-21 gene for the first time and analysed the PTPN22 1858T polymorphism in type 1A diabetes (T1AD) patients and healthy controls (HC). We correlated the frequencies of islet and extra-pancreatic autoantibodies with genotypes from both loci. The case series comprised 612 T1AD patients and 792 HC. Genotyping of PTPN22 C1858T was performed on 434 T1AD patients and 689 HC. The −448 to +83 base pairs (bp) region of the IL-21 gene was sequenced in 309 Brazilian T1AD and 189 HC subjects. We also evaluated human leucocyte antigen (HLA) DR3/DR4 alleles. The frequencies of glutamic acid decarboxylase (GAD65), tyrosine phosphatase-like protein (IA)-2, anti-nuclear antibody (ANA), thyroid peroxidase (TPO), thyroglobulin (TG), thyrotrophin receptor autoantibody (TRAb), anti-smooth muscle (ASM) and 21-hydroxylase (21-OH) autoantibodies were higher in T1AD patients than in HC. The PTPN22 1858T allele was associated with an increased risk for developing T1AD [odds ratio (OR) = 1·94; P < 0·001], particularly in patients of European ancestry, and with a higher frequency of GAD65 and TG autoantibodies. HLA-DR3/DR4 alleles predominated in T1AD patients. A heterozygous allelic IL-21 gene variant (g.-241 T > A) was found in only one patient. In conclusion, only PTPN22 C1858T polymorphism and HLA-DR3 and/or DR4 alleles, but not allelic variants in the 5′-proximal region of the IL-21 gene were associated with T1AD risk. Patients with T1AD had increased frequencies of anti-islet-cell, anti-thyroid, anti-nuclear, anti-smooth muscle and anti-21-OH autoantibodies. The C1858T PTPN22 polymorphism was also associated with a higher frequency of GAD65 and TG autoantibodies.

Hepatitis C virus (HCV) infection frequently persists despite substantial virus-specific immune responses and the combination of pegylated interferon (INF)-α and ribavirin therapy. Major histocompatibility complex class I restricted CD8(+) T cells are responsible for the control of viraemia in HCV infection, and several studies suggest protection against viral infection associated with specific HLAs. The reason for low rates of sustained viral response (SVR) in HCV patients remains unknown. Escape mutations in response to cytotoxic T lymphocyte are widely described; however, its influence in the treatment outcome is ill understood. Here, we investigate the differences in CD8 epitopes frequencies from the Los Alamos database between groups of patients that showed distinct response to pegylated α-INF with ribavirin therapy and test evidence of natural selection on the virus in those who failed treatment, using five maximum likelihood evolutionary models from PAML package. The group of sustained virological responders showed three epitopes with frequencies higher than Non-responders group, all had statistical support, and we observed evidence of selection pressure in the last group. No escape mutation was observed. Interestingly, the epitope VLSDFKTWL was 100% conserved in SVR group. These results suggest that the response to treatment can be explained by the increase in immune pressure, induced by interferon therapy, and the presence of those epitopes may represent an important factor in determining the outcome of therapy.

Summary: Objective  Adiponectin is an important mediator of insulin sensitivity, encoded by the ADIPOQ gene. Here we describe two Japanese–Brazilian families with hypoadiponectinaemia due to a novel mutation in ADIPOQ.Design and patients  In this study, we examined the entire translated regions of adiponectin in Japanese–Brazilians, a population with one of the highest prevalence rates of diabetes worldwide. We screened 200 patients with type 2 diabetes (DM) and 240 age‐matched subjects with normal glucose tolerance.Results  A novel heterozygous T deletion at position 186 in exon 2 of ADIPOQ, causing a frameshift at codon 62 and leading to a premature termination at codon 168 (p.Gly63ValfsX106), was found in two individuals with diabetes. This mutation was not found in 240 nondiabetic control subjects. In addition, we screened the mutation in an expanded set of 100 nondiabetic subjects from the general Brazilian population, but we found no mutations. In addition, six family members of the probands were identified as mutation‐carriers. Individuals who were mutation‐carriers had markedly low plasma adiponectin concentrations compared with those without the mutation [DM: 0·65 (0·59–1·34) µg/ml vs. 5·30 (3·10–8·55) µg/ml, P < 0·0001; normal glucose tolerance: 0·95 (0·76–1·48) µg/ml vs. 8·50 (5·52–14·55) µg/ml, P = 0·003]. All individuals carrying the p.Gly63ValfsX106 mutation and older than 30 years were found to be diabetic.Conclusions  We describe for the first time a frameshift mutation in exon 2 of the ADIPOQ gene, which modulates adiponectin levels and may contribute to the genetic risk of late‐onset diabetes in Japanese–Brazilians.

The ADH (alcohol dehydrogenase) system is one of the earliest known models of molecular evolution, and is still the most studied in Drosophila. Herein, we studied this model in the genus Anastrepha (Diptera, Tephritidae). Due to the remarkable advantages it presents, it is possible to cross species with different Adh genotypes and with different phenotype traits related to ethanol tolerance. The two species studied here each have a different number of Adh gene copies, whereby crosses generate polymorphisms in gene number and in composition of the genetic background. We measured certain traits related to ethanol metabolism and tolerance. ADH specific enzyme activity presented gene by environment interactions, and the larval protein content showed an additive pattern of inheritance, whilst ADH enzyme activity per larva presented a complex behavior that may be explained by epistatic effects. Regression models suggest that there are heritable factors acting on ethanol tolerance, which may be related to enzymatic activity of the ADHs and to larval mass, although a pronounced environmental effect on ethanol tolerance was also observed. By using these data, we speculated on the mechanisms of ethanol tolerance and its inheritance as well as of associated traits.