Chromosome Mapping of H1 and H4 Histones in Parodontidae (Actinopterygii: Characiformes): Dispersed and/or Co-Opted Transposable Elements?

The karyotypes of the family Parodontidae consist of 2n = 54 chromosomes. The main chromosomal evolutionary changes of its species are attributed to chromosome rearrangements in repetitive DNA regions in their genomes. Physical mapping of the H1 and H4 histones was performed in 7 Parodontidae species to analyze the chromosome rearrangements involved in karyotype diversification in the group. In parallel, the observation of a partial sequence of an endogenous retrovirus (ERV) retrotransposon in the H1 histone sequence was evaluated to verify molecular co-option of the transposable elements (TEs) and to assess paralogous sequence dispersion in the karyotypes. Six of the studied species had an interstitial histone gene cluster in the short arm of the autosomal pair 13. Besides this interstitial cluster, in Apareiodon davisi, a probable further site was detected in the terminal region of the long arm in the same chromosome pair. The H1/H4 clusters in Parodon cf. pongoensis were located in the smallest chromosomes (pair 20). In addition, scattered H1 signals were observed on the chromosomes in all species. The H1 sequence showed an ERV in the open reading frame (ORF), and the scattered H1 signals on the chromosomes were attributed to the ERV's location. The H4 sequence had no similarity to the TEs and displayed no dispersed signals. Furthermore, the degeneration of the inner ERV in the H1 sequence (which overlapped a stretch of the H1 ORF) was discussed regarding the likelihood of molecular co-option of this retroelement in histone gene function in Parodontidae.

Genetic characterization of 32 X-InDels in a population sample from São Paulo State (Brazil).

X-chromosomal markers can be useful in some forensic cases, where the analysis of the autosomal markers is not conclusive. In this study, a population sample of 500 unrelated individuals born in São Paulo State was characterized for 32 X-InDel markers. No deviations from the Hardy-Weinberg equilibrium were detected, except for MID1361. The 32 X-InDels showed an accumulated power of discrimination of 0.9999999999993 in females and 0.99999993 in males and an exclusion chance of 0.999996 in trios and 0.99995 in duos. São Paulo showed lower genetic distances to the Colombian admixed and European populations than to Native American, Asian, or African populations. Ancestry analysis revealed 41.8% European, 31.6% African, and 26.6% Native American contributions. Segregation analysis was performed in 101 trios, and the mutation rate was estimated to be low.

Antidiabetic Disruptors of the Glucokinase-Glucokinase Regulatory Protein Complex Reorganize a Coulombic Interface.

The glucokinase regulatory protein (GKRP) plays an essential role in glucose homeostasis by acting as a competitive inhibitor of glucokinase (GCK) and triggering its localization to the hepatocyte nucleus upon glucose deprivation. Metabolites such as fructose 6-phosphate and sorbitol 6-phosphate promote assembly of the GCK-GKRP complex, whereas fructose 1-phosphate and functionalized piperazines with potent in vivo antidiabetic activity disrupt the complex. Here, we establish the molecular basis by which these natural and synthetic ligands modulate the GCK-GKRP interaction. We demonstrate that a small-molecule disruptor of the protein-protein interaction utilizes a two-step conformational selection mechanism to associate with a rare GKRP conformation constituting 3% of the total population. Conformational heterogeneity of GKRP is localized to the N-terminus and deleting this region eliminates the ability of sorbitol 6-phosphate to promote the GCK-GKRP interaction. Stabilizing ligands favor an extended N-terminus, which sterically positions two arginine residues for optimal Coulombic interaction with a pair of carboxylate side chains from GCK. Conversely, disruptors promote a more compact N-terminus in which an interfacial arginine residue is stabilized in an unproductive orientation through a cation-π interaction with tyrosine 75. Eliminating the ability to sample this binding impaired conformation enhances the intrinsic inhibitory activity of GKRP. Elucidating the molecular basis of ligand-mediated control over the GCK-GKRP interaction is expected to impact the development and future refinement of therapeutic agents for diabetes and cardiovascular disease, which result from improper GKRP regulation of GCK.

Genetic characterization of an X-STR decaplex system in the State of Mato Grosso, Brazil: distribution, forensic efficiency and population structure.

Studies with X-STR loci show population genetic substructure, which makes necessary the characterization of such markers in the different geographical and/or ethnic populations. Therefore, this study assessed the distribution and forensic efficiency of an X-STR decaplex system in the population of the State of Mato Grosso, as well as analysed the population structure of this State based on the aforementioned system. All X-STR markers were in Hardy-Weinberg equilibrium and linkage equilibrium, and the DXS6809 was the most informative marker. The power of discrimination value in females and males was 0.99999999995 and 0.9999994, respectively. Analysis of molecular variance indicated 1.10% (p < 0.00001) of heterogeneity among Europeans, Africans, Brazilians and other Latin Americans, and in relation to such groups, the population of the State of Mato Grosso showed lower genetic variation when compared with the Brazilian group (-0.10%, p = 0.67327). The genetic distance analysis showed lower values of F ST (0.0004 ≤ F ST ≤ 0.00331), with non-significant p value (p > 0.00024), between the populations of Mato Grosso and Mato Grosso do Sul, Paraná and the Southeast region of Brazil (except for one sample of Rio de Janeiro). F ST values with significant p values (p ≤ 0.00024) were obtained between the population of Mato Grosso and Iberian, African and some Latin American populations. The X-STR decaplex system proved to be extremely useful in the population of the State of Mato Grosso, and the data obtained does not show the need for a specific forensic database for this State in relation to the Brazilian populations compared in this study, except for population of Rio de Janeiro.

Mutation rates for 20 STR loci in a population from São Paulo state, Southeast, Brazil.

Short tandem repeats (STRs) are genetic markers largely employed in forensic analysis and paternity investigation cases. When an inconsistency between the parent and child is considered as a possible mutation, the mutation rate should be incorporated into paternity index calculations to give a robust result and to reduce the chance of misinterpretation. The aim of this study was to estimate the mutation rates of 20 autosomal STRs loci used for paternity tests. In these loci we analysed 29,831 parent-child allelic transfers from 929 duo or trio paternity tests carried out during 2012?2016 from São Paulo State, Brazil. We identified 35 mutations in 16 loci, and they were more frequent in the paternal germline compared to the maternal germline. The loci with the highest rate were vWA and FGA and the ones with the lowest rate were PENTA E, PENTA D, D21S11, D7S820 and D6S1043. We did not identified any mutation in D2S1338, TH01, TPOX and D16S539 loci. All mutations consisted of losses or gains of one repeat unit. Mutation rates found in the São Paulo population have peculiarities, which justifies the use of regional databases in laboratories.

Comparative Cytogenetics of Hoplerythrinus unitaeniatus (Agassiz, 1829) (Characiformes, Erythrinidae) Species Complex from Different Brazilian Hydrographic Basins.

Chromosomal characteristics of Hoplerythrinus unitaeniatus populations from 5 Brazilian river basins, namely Arinos (Amazonas basin), Araguaia, Paraguai, Alto Paraná, and São Francisco were analyzed by conventional Giemsa staining, C-banding, silver nitrate impregnation, and fluorescence in situ hybridization (FISH) with 18S and 5S rDNA and telomeric sequence (TTAGGG)n probes. The diploid chromosome number was 2n = 48 in representatives of the populations from Paraguai and Alto Paraná River basins and 2n = 52 for those from the Arinos and Araguaia River basins. The São Francisco population had individuals with 2n = 50 and 52 occurring in sympatry. C-banding showed heterochromatic blocks mainly located at interstitial and pericentromeric positions in most of the chromosomes. Silver nitrate impregnation demonstrated simple NORs for representatives from Arinos and Araguaia River populations and multiple NORs for specimens from Paraguai, Alto Paraná, and São Francisco River populations. FISH with 18S and 5S rDNA probes revealed many chromosomes carrying these cistrons, with up to 21 chromosomes bearing 18S rDNA sites (Alto Rio Paraná basin) and up to 12 chromosomes with 5S rDNA sites (Paraguai basin), besides the occurrence of colocalization in all populations. FISH with telomeric sequence (TTAGGG)n detected sites in the terminal portion of the chromosomes in all populations. These data reinforce the idea that H. unitaeniatus is a species complex. Evolutionary and biogeographical aspects of the group in the Neotropical region are discussed.

Analysis of SOD1 and C9orf72 mutations in patients with amyotrophic lateral sclerosis in Antioquia, Colombia / Análisis de mutaciones en los genes SOD1 y C9orf72 en pacientes con esclerosis lateral amiotrófica, Antioquia, Colombia

INTRODUCTION: Amyotrophic lateral sclerosis is a neurodegenerative disease with a possible multifactorial origin characterized by the progressive degeneration of motor neurons. There is a relatively high prevalence of this disease in Antioquia; however, there is no published genetic study to date in Colombia. Despite its unknown etiopathogenesis, more genetic risk factors possibly involved in the development of this disease are constantly found. OBJETIVES: To evaluate G93A and D90A mutations in SOD1 gene and a short tandem repeat in C9orf72 within a cohort of amyotrophic lateral sclerosis patients from Antioquia, Colombia. Materials y methods: Thirty-four patients previously diagnosed with amyotrophic lateral sclerosis were included in the study. Peripheral blood samples were used for DNA extraction and genotyping. RESULTS: No mutations were found in SOD1 (G93A and D90A) in any of the patients, while C9orf72 exhibited an allele with a statistically significant high prevalence in the study sample (8 hexanucleotide repeats of CAGCAG). CONCLUSIONS: These results suggest an association between this short tandem repeat (STR) in C9orf72 and the presence of amyotrophic lateral sclerosis in the studied population. However, this association should be established in a larger sample size and with controls from the same population. In addition, there also seems to be a genetic anticipation effect for the disease regarding this locus, since patients with this genotype present an earlier onset.

Introducción. La esclerosis lateral amiotrófica es una enfermedad neurodegenerativa con un posible origen multifactorial, caracterizado por una degeneración progresiva de las neuronas motoras. Hay una gran prevalencia relativa de esta enfermedad en Antioquia; sin embargo, no hay publicaciones de estudios genéticos en Colombia. A pesar de su etiopatogénesis desconocida, hay varios factores de riesgo genético que se encuentran constantemente en el desarrollo de esta enfermedad. Objetivo. Evaluar las mutaciones G93A y D90A del gen SOD1 y una repetición corta en tándem (Short Tandem Repeat, STR) en el locus C9orf72, en una cohorte de pacientes con esclerosis lateral amiotrófica en Antioquia, Colombia. Materiales y métodos. Se incluyeron 34 pacientes previamente diagnosticados en el estudio. Una muestra de sangre periférica se usó para extraer el ADN y, posteriormente, genotipificarlo. Resultados. No se encontraron mutaciones en el gen SOD1 (G93A y D90A), mientras que el C9orf72 exhibe un alelo con una significativa prevalencia en los pacientes del estudio (8 repeticiones del hexanucleótido G4C2). Conclusiones. Se sugiere una asociación entre la repetición en tándem en C9orf72 y la presencia de la esclerosis lateral amiotrófica en la población estudiada. Sin embargo, se sugiere hacer estudios adicionales e incluir un grupo control de la misma población. Además, se detecta un fenómeno de anticipación genética de la enfermedad, dado que los pacientes con el alelo de 8 repeticiones en C9orf72 presentan una edad temprana de aparición de los síntomas.

LGBT Studies Without LGBT Studies: Mapping Alternative Pathways in Perú and Colombia.

Our article tackles gender and sexual diversity scholarship in Colombia and Perú, two countries without institutionalized LGBT studies programs. By analyzing the impact of literary works in Perú and an annual conference in Colombia's capital, we show how LGBT-related scholarship (and activism) has been advanced in these Andean countries with tactful maneuvering, as they offset contemporary violence-and a strong religious influence. Our comparison allows us to showcase two of the most common ways through which these countries have engaged in LGBT research and activism. This region-centered, dual-country approach underscores the broader need of researching and documenting these efforts.

Chromosomal Diversification in Two Species of Pimelodus (Siluriformes: Pimelodidae): Comparative Cytogenetic Mapping of Multigene Families.

Pimelodidae has a high number of species, but cytogenetic studies are generally restricted to classical chromosomal characterization and in situ localization of ribosomal DNA (rDNA) genes. This study was developed to compare Pimelodus microstoma and Pimelodus pohli focusing on chromosomal diversification provided by the transposition of DNA sequences containing multigene families. Both species share 56 chromosomes, with centromeric and terminal heterochromatic blocks. The silver nucleolus organizer regions (Ag-NORs)/45S rDNA was located in the chromosome pair 24 for both species. The 5S rDNA sites were evidenced in the pair 8 of P. microstoma, and in the pairs 1, 17, and 18 in P. pohli. The U1 small nuclear RNA (snRNA) was located at terminal site in the first subtelocentric pair in both species. The U2 snRNA site was syntenic to 5S rDNA in non-homeologue chromosomes between analyzed species. The histones H3 and H4 were clustered in chromosome pairs 19 and 23 in P. microstoma, and 21 and 22 in P. pohli. Our study proposes that the movement of DNA sequences carrying multigene families has been driven on the chromosomal diversification of Pimelodidae. These multigene location in the genomes can explain most of the visualized chromosomal rearrangements in Pimelodidae and it is useful to understand the chromosomal changes and their distinctive karyotype formulae.

The first homozygous family for prothrombin G20210A polymorphism reported in Latin America.

The 20210A allele of the prothrombin gene is associated with increased risk of venous thromboembolism. In this study, we described manifestations of thrombosis in four generations of a Colombian family, with four 20210A homozygous carriers and six 20210G/A heterozygous carriers for polymorphism as well as unrelated participants from the same population. The levels of prothrombin in the 20210A homozygote patients were higher than in the normal 20210G homozygotes (133 + 11% and 92.3 + 12.4%, respectively, P < .01) and the 20210G/A heterozygotes (133 + 11% vs. 114.8 + 24%, P < .05). About 2 out of 4 20210A homozygotes and 5 out of 6 20210G/A heterozygous members of this family did not have venous thromboembolism or any other thrombotic manifestation even though one of them had been exposed to thrombotic risk factors. Thus, we posit the effect of 20210A on the thrombotic phenotype in this family seems to be weak.

[Cardiovascular disease risk factors in people working at a Colombian health institution]. / Factores de Riesgo para Enfermedad Cardiovascular en Trabajadores de una Institución Prestadora de Servicios de Salud, Colombia.

OBJECTIVE: Establishing the prevalence of recognised biological and behavioural cardiovascular disease (CVD) risk factors in a population of workers at a health institution in Popayán, Colombia. METHODS: An observational descriptive study was conducted, 96 employees being interviewed to obtain information regarding their socio-demographic characteristics, tobacco and alcohol consumption, physical activity, eating habits and personal and family history of CVD. Each worker's standardised glycaemia, serum lipids, arterial blood pressure and body mass index were measured. RESULTS: There was 12,5% behavioural risk factor prevalence for smoking, 58,3 % for alcohol consumption, 56,3 % physical inactivity during free time and 82,3 % atherogenic diet; biological risk factor prevalence was 11,5 % hypertension, 45,8 % being overweight, 1 % diabetes, 61,5 % dyslipidaemia and 58,3 % family history of CVD. It was also found that the risk of hypertension was significantly higher in males, in individuals >40 years, in people having >25 BMI and in smokers. Regarding dyslipidaemia, the risk was higher in males and in >40 year old individuals. The risk of being overweight and obese was significantly associated with smoking and alcohol consumption. CONCLUSION: Although this is an institution having an asymptomatic and relatively young population (25-55 years), action should be taken towards modifying lifestyles to reduce CVD risk in the affected population due to the high prevalence of biological and behavioural risk factors.

Effects of Continuous and Accumulated Exercise on Endothelial Function in Rat Aorta.

BACKGROUND:: The practice of exercise in short bouts repeated throughout the day may be an alternative strategy to lift people out of physical inactivity. OBJECTIVE:: to evaluate if accumulated exercise, as occurs in continuous exercise training, improve endothelial function in rat aorta. METHODS:: Wistar male rats were divided into three groups: continuous exercise (CEx, 1 hour on the treadmill) or accumulated exercise (AEx, 4 bouts of 15 minutes / day) for 5 days/week for 8 weeks, or sedentary (SED). During the training period, body weight gain and increase in exercise performance were recorded. On sacrifice day, aorta was dissected into rings (3-5 mm) and mounted on the organ bath. RESULTS:: Fitness was significantly greater in CEx and AEx rats as compared with SED animals. In addition, compared with the SED group, CEx animals had a lower body mass gain, and the aorta obtained from these animals had reduced contractile response to norepinephrine and greater acetylcholine-induced relaxation. These results were not observed in ACEx animals. CONCLUSIONS:: Both CEx and AEx improved fitness, but only CEx led to reduced body weight gain and improved endothelial function. FUNDAMENTO:: A prática de exercícios em sessões curtas que se repetem ao longo do dia pode ser uma alternativa para tirar as pessoas da inatividade física. OBJETIVO:: Verificar se o exercício acumulado, tal como ocorre com o treinamento com exercício contínuo, melhora a função endotelial na aorta de ratos. MÉTODOS:: Ratos Wistar machos foram divididos em 3 grupos: treinamento com exercício contínuo (ExC; 1 hora em esteira) ou com exercício acumulado (ExA; 4 sessões de 15 minutos ao longo do dia) por 5 dias/semana, durante 8 semanas, ou grupo sedentário (SED). Durante o treinamento, foram registrados o ganho de peso corporal e desempenho na esteira. No dia do sacrifício, anéis (3-5 mm) da aorta foram obtidos e montados em banho de órgãos. RESULTADOS:: Animais ExC e ExA mostraram aptidão física significativamente maior em comparação com os SED. Paralelamente, em comparação com SED, animais ExC tiveram menor ganho de massa corporal, e aortas retiradas desses animais mostraram respostas contrácteis à noradrenalina reduzidas e maior relaxamento induzido pela acetilcolina. Esses resultados não foram observados no grupo ExA. CONCLUSÕES:: Tanto o ExC quanto o ExA melhoraram a aptidão física, mas somente o ExC foi capaz de reduzir o ganho de peso corporal dos animais e melhorar a função endotelial.

Karyotype Diversity and Evolutionary Trends in Armored Catfish Species of the Genus Harttia (Siluriformes: Loricariidae).

Most species of the genus Harttia inhabits the headwaters of small tributaries, but some species are restricted to the main channel of some rivers. This feature, combined with limited dispersal ability, leads to the formation of small isolated populations with reduced gene flow. Currently, there are 23 taxonomically defined and recognized species, and 17 of these are found in Brazil, distributed in several hydrographic basins. Despite this diversity, few chromosomal data for the species belonging to this genus are found in the literature. Thus, this study analyzed, by classical and molecular cytogenetics methodologies, the chromosomal diversity of this genus, to discuss the processes that are involved in the evolution and karyotype differentiation of the species of the group. Seven species of Harttia were analyzed: H. kronei, H. longipinna, H. gracilis, H. punctata, H. loricariformis, H. torrenticola, and H. carvalhoi. The chromosomal diversity found in these species includes different diploid and fundamental numbers, distinct distribution of several repetitive sequences, the presence of supernumerary chromosomes in H. longipinna and multiple sex chromosome systems of the type XX/XY1Y2 in H. carvalhoi and X1X1X2X2/X1X2Y in H. punctata. Lastly, our data highlight the genus Harttia as an excellent model for evolutionary studies.

Expression of HLA-E molecules in the placental tissue of women infected with HIV-1 and uninfected women.

INTRODUCTION: Expression of HLA-E molecule in the placental extravillous trophoblast is associated with immune system cell inhibition, resulting in immune tolerance to fetus during pregnancy. HIV-1 can infect trophoblast cells and modify the expression of HLA-E, which may inhibit the cytotoxic activity of the immune system. AIM: The aim of this study was to evaluate HLA-E expression in third trimester placental tissue of women infected with HIV-1 and uninfected women. METHODS: We performed an immunohistochemistry assay to evaluate HLA-E staining in the placental tissue of 99 HIV-1 infected and 85 uninfected women. A pathologist analyzed and classified the HLA-E expression in the placental cells. RESULTS: Irrespective of the HIV status, HLA-E staining was observed in the extravillous trophoblast cells, endothelial cells and Hofbauer cells, but not in the syncytiotrophoblast. HLA-E staining showed no significant difference between the placental tissue of women infected with HIV-1 and uninfected women (P = 0.76). Considering HIV-1 infected women, HLA-E staining was not influenced by HIV-1 viral load (P = 0.48), CD4+ T-cell count (P = 0.10) and antiretroviral therapy used during pregnancy (P = 0.54). DISCUSSION: Despite the presence of HIV-1 infection, the expression of HLA-E molecules in the placental tissue was not modified when the infection was under antiretroviral therapy control.

Chromosome Analyses of Apareiodon argenteus and Apareiodon davisi (Characiformes, Parodontidae): An Extensive Chromosomal Polymorphism of 45S and 5S Ribosomal DNAs.

This study analyzed two Apareiodon species without available chromosome data: Apareiodon argenteus and Apareiodon davisi. Both species have 54 metacentric/submetacentric chromosomes, with centromeric blocks of heterochromatin. Nucleolus organizer regions were active in chromosome pair 2 in A. argenteus and pairs 4 and 9 in A. davisi. In A. argenteus, 45S and 5S ribosomal genes were located in chromosome pairs 2 and 18, respectively. Polymorphisms were observed in these ribosomal sequences in A. davisi, with variations in the number/position of sites, and colocalization of these genes in some chromosome pairs. The WAp repetitive fraction was dispersed along the chromosomes of the two species. The satellite DNA pPh2004 was identified in chromosome pairs 7, 8, 10, 11, and 18 in A. argenteus and in pair 24 in A. davisi. The present study describes the first case of chromosomal polymorphisms involving two ribosomal sequences in Parodontidae and discusses the role of repetitive DNAs in the genome and karyotype diversity of this family.

Occurrence of Natural Hybrids Among Sympatric Karyomorphs in Hoplerythrinus unitaeniatus (Characiformes, Erythrinidae).

In this study, 43 specimens of Hoplerythrinus unitaeniatus from the São Francisco River basin were chromosomally analyzed by conventional Giemsa staining, C-banding, silver nitrate impregnation, and fluorescence in situ hybridization (FISH) with probes of 5S and 18S rDNA. The diploid numbers found were 50 and 52 chromosomes, showing the existence of two well-defined biological entities in sympatry. Specimens with 51 chromosomes, which showed three distinct karyotypic forms, were also found and are characterized as natural hybrids due to the correspondence with the chromosomes of the specimens with 50 and 52 chromosomes. By FISH using 5S and 18S rDNA probes, it was possible to detect specific chromosomal markers for the specimens with 50 and 52 chromosomes, as well as the occurrence of common sites in both. The specimens with 51 chromosomes showed intermediate patterns for these markers, reinforcing the hypothesis that these are actual natural hybrids. A review and new classification for the karyomorphs of H. unitaeniatus have also been proposed.

Expanding the mutation spectrum in 182 Spanish probands with craniosynostosis: identification and characterization of novel TCF12 variants.

Craniosynostosis, caused by the premature fusion of one or more of the cranial sutures, can be classified into non-syndromic or syndromic and by which sutures are affected. Clinical assignment is a difficult challenge due to the high phenotypic variability observed between syndromes. During routine diagnostics, we screened 182 Spanish craniosynostosis probands, implementing a four-tiered cascade screening of FGFR2, FGFR3, FGFR1, TWIST1 and EFNB1. A total of 43 variants, eight novel, were identified in 113 (62%) patients: 104 (92%) detected in level 1; eight (7%) in level 2 and one (1%) in level 3. We subsequently screened additional genes in the probands with no detected mutation: one duplication of the IHH regulatory region was identified in a patient with craniosynostosis Philadelphia type and five variants, four novel, were identified in the recently described TCF12, in probands with coronal or multisuture affectation. In the 19 Saethre-Chotzen syndrome (SCS) individuals in whom a variant was detected, 15 (79%) carried a TWIST1 variant, whereas four (21%) had a TCF12 variant. Thus, we propose that TCF12 screening should be included for TWIST1 negative SCS patients and in patients where the coronal suture is affected. In summary, a molecular diagnosis was obtained in a total of 119/182 patients (65%), allowing the correct craniosynostosis syndrome classification, aiding genetic counselling and in some cases provided a better planning on how and when surgical intervention should take place and, subsequently the appropriate clinical follow up.

Role of connecting loop I in catalysis and allosteric regulation of human glucokinase.

Glucokinase (GCK, hexokinase IV) is a monomeric enzyme with a single glucose binding site that displays steady-state kinetic cooperativity, a functional characteristic that affords allosteric regulation of GCK activity. Structural evidence suggests that connecting loop I, comprised of residues 47-71, facilitates cooperativity by dictating the rate and scope of motions between the large and small domains of GCK. Here we investigate the impact of varying the length and amino acid sequence of connecting loop I upon GCK cooperativity. We find that sequential, single amino acid deletions from the C-terminus of connecting loop I cause systematic decreases in cooperativity. Deleting up to two loop residues leaves the kcat value unchanged; however, removing three or more residues reduces kcat by 1000-fold. In contrast, the glucose K0.5 and KD values are unaffected by shortening the connecting loop by up to six residues. Substituting alanine or glycine for proline-66, which adopts a cis conformation in some GCK crystal structures, does not alter cooperativity, indicating that cis/trans isomerization of this loop residue does not govern slow conformational reorganizations linked to hysteresis. Replacing connecting loop I with the corresponding loop sequence from the catalytic domain of the noncooperative isozyme human hexokinase I (HK-I) eliminates cooperativity without impacting the kcat and glucose K0.5 values. Our results indicate that catalytic turnover requires a minimal length of connecting loop I, whereas the loop has little impact upon the binding affinity of GCK for glucose. We propose a model in which the primary structure of connecting loop I affects cooperativity by influencing conformational dynamics, without altering the equilibrium distribution of GCK conformations.

Chromosomal distribution of the retroelements Rex 1, Rex 3 and Rex 6 in species of the genus Harttia and Hypostomus (Siluriformes: Loricariidae)

The transposable elements (TE) have been widely applied as physical chromosome markers. However, in Loricariidae there are few physical mapping analyses of these elements. Considering the importance of transposable elements for chromosomal evolution and genome organization, this study conducted the physical chromosome mapping of retroelements (RTEs) Rex1, Rex3 and Rex6 in seven species of the genus Harttia and four species of the genus Hypostomus, aiming to better understand the organization and dynamics of genomes of Loricariidae species. The results showed an intense accumulation of RTEs Rex1, Rex3 and Rex6 and dispersed distribution in heterochromatic and euchromatic regions in the genomes of the species studied here. The presence of retroelements in some chromosomal regions suggests their participation in various chromosomal rearrangements. In addition, the intense accumulation of three retroelements in all species of Harttia and Hypostomus, especially in euchromatic regions, can indicate the participation of these elements in the diversification and evolution of these species through the molecular domestication by genomes of hosts, with these sequences being a co-option for new functions.(AU)

Os elementos transponíveis (TE) têm sido amplamente aplicados como marcadores cromossômicos. Contudo, em Loricariidae, há poucas análises de mapeamento físico destes elementos. Considerando a importância de elementos transponíveis para a evolução cromossômica e organização genômica, este trabalho realizou o mapeamento físico cromossômico dos retroelementos (RTEs) Rex1, Rex3 e Rex6 em sete espécies do gênero Harttia e em quatro espécies do gênero Hypostomus, com o intuito de melhor compreender a organização e dinâmica dos genomas das espécies de Loricariidae. Os resultados evidenciaram um intenso acúmulo dos RTEs Rex1, Rex3 e Rex6 e distribuição dispersa em regiões heterocromáticas e eucromáticas no genoma das espécies estudadas. A presença de retroelementos em algumas regiões cromossômicas sugere sua participação em vários rearranjos cromossômicos. Além disso, o intenso acúmulo dos três retroelementos em todas as espécies de Harttia e Hypostomus, especialmente em regiões eucromáticas, pode indicar a participação destes elementos na diversificação e evolução destas espécies através da domesticação molecular pelo genoma dos hospedeiros, com estas sequências sendo co-optadas paras novas funções.(AU)