Genetic Isolation Research Articles

Current status of the Peromyscus mexicanus complex in Oaxaca, México

The physiographic, climatic, and ecological characteristics of the mountainous regions of Oaxaca are unique and host geographically isolated populations of Peromyscus mexicanus. Populations of P. mexicanus from the Sierra Madre del Sur in the Gulf side (SMG) and Pacific side (SMP), Oaxaca, were compared at the craniodental and molecular genetic levels (cytochrome b sequences). The geographic isolation of both sides of the Sierra Madre del Sur are expected to have led to genetic isolation between populations of P. mexicanus in each area and from populations of eastern México. Our results show that the Oaxacan SMG and SMP populations are genetically different, as are populations of eastern México. Populations in the Oaxaca SMG-SMP are more genetically similar to P. gymnotis than to P. mexicanus from eastern México. We recommend that the Oaxacan SMG population be classified as P. totontepecus and the SMP population as P. angelensis, with the Putla population, which is morphologically and morphometrically different, as the subspecies, P. a. putlaensis.

Clinical pharmacology of the SingleTablet Regimen (STR) Bictegravir/Emtricitabine/Tenofovir Alafenamide (BIC/FTC/TAF).

In Italy a proportion of HIV patients exceeding 50% are diagnosed at advanced stages of disease. A sizeable proportion of patients under chronic HIV treatment has a story of poor adherence with archived resistance associated mutations, a condition implying some risks in case of treatment with dual regimens. Conventional three-drug regimens will remain necessary in the short-mid term, in order to avoid treatment failure and selection of drug resistance. Efficacy, tolerability, safety, genetic barrier, forgiveness and a good compatibility with concurrent medications are all features that describe the overall quality of BIC/FTC/TAF, a combination whose robustness will remain a point of reference for the next years.

Mangrove propagules are limited in their capacity to disperse across long distances

Abstract Mangroves are subject to rapid and large-scale habitat changes, which threaten their unique genetic diversity and provision of critically important ecosystem services. Habitat fragmentation reduces connectivity, which can impair dispersal and lead to genetic isolation. However, it is unclear whether fragmentation could impact mangrove genetic isolation, as mangrove propagules appear to be able to disperse long distances. Here, we conducted a meta-analysis of studies testing for a correlation between geographic distance and genetic distance in mangrove plants. From the 22 studies that met the inclusion criteria, we found a significant isolation-by-distance effect; geographic distance was significantly associated with Nei’s genetic distance and FST. Our results show that mangrove propagules may be limited in their capacity to disperse across long distances, which highlights the importance of maintaining close proximity between habitat patches and reducing habitat fragmentation.

Probiotics in atopic dermatitis: Where do we stand?

Introduction: Atopic dermatitis (AD) is a chronic, inflammatory skin disorder that significantly impairs life quality and mostly affects children. Although classical approaches of treatment have been effective in mitigating the symptoms of AD, novel remedial measures based on a better understanding of immunopathogenesis are needed to target the underlying etiology. Aims and Objectives: Probiotics improve the intestinal micro environment and restore the balance of immune responses, thereby, emerging as a novel therapeutic option in the management of AD. Taking into account the updated information available, this review aims to discuss the beneficial effects of probiotics on gut microbiota, their role in strengthening the epidermal barrier and immunological responses, and hence their clinical usage in AD. Results: Classically, AD has been understood as a complex interplay between genetic susceptibility, barrier dysfunction, immune dysregulation, and exogenous factors. Current research has demonstrated that AD is associated with changes in both skin and gut microflora. The "gut-skin" axis hypothesis and the interaction between them have been demonstrated in research. Patients with AD have demonstrated gut dysbiosis, which leads to immune dysregulation and can serve as a potential trigger for AD. Probiotics, by their ability to put right gut dysbiosis, have demonstrated modest efficacy in reducing disease activity in clinical studies. Conclusion: Although multiple randomized controlled trials and meta-analyses have demonstrated the utility of probiotics as adjuvant therapy in the management of AD, the need of the hour is to develop precise guidelines pertaining to their usage in AD.

Genetic characterization and virus isolation of porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome virus (PRRSV) is an acute, febrile, highly contagious infectious disease characterized by reproductive dysfunction and respiratory failure. Its high morbidity and mortality have caused significant economic losses to the swine industry. With the continuous development of PRRSV, its genetic variation is also increasing, which causes great difficulties for the clinical prevention and control of infections casued by the virus. Monitoring the genetic variation of the virus and vaccine immunity at any time is the current research focus. In this study, patients suspected of having PRRSV were sampled, and the virus was successfully isolated. The genomic variation characteristics of the new isolate of HLJ03 were determined, especially the molecular characteristics of GP5 and NSP2, and the main focus was placed on the analysis of genetic variation. The results provide important information for further investigation of the molecular prevalence of porcine PRRSV and create a basis for the prevention and control of porcine PRRSV infections.

Therapy initiation and rapid start with Bictegravir/Emtricitabine/Tenofovir Alafenamide in PLWH.

Advanced HIV naive represents an unfavorable prognostic condition due to a persistent high risk of death, increased probability of virological failure, immunologic impairment, clinical progression, and immune reconstitution inflammatory syndrome (IRIS), cumulative adverse drug events, drug-drug interactions and increased healthcare costs. Currently, all international guidelines recommend the rapid initiation of ART, especially in late-stage naive patients. Bictegravir/emtricitabine/tenofovir alafenamide (B/F/TAF), due to its efficacy high genetic barrier, good safety profile, and low DDI potential, is one of the regimens recommended for overall rapid initiation by international guidelines. B/F/TAF has been tested in observational or uncontrolled pilot studies (OPERA, RAINBOW), while a large randomized controlled trial is currently ongoing (LAPTOP). In conclusion, B/F/TAF is an ideal combination for the initiation of antiretroviral therapy, particularly in the HIV late presenter or advanced HIV disease patient, even in the context of rapid start or same-day treatment regimens, where the initiation of treatment usually occurs in the absence of information on viral load, CD4 count, biochemical profile and HIV transmitted resistance.

Conservation strategies for endemic Dendrocalamus manipureanus: A study on genetic diversity and population structure based on molecular and phytochemical markers

Genetic diversity and population structure studies were conducted for the first time on endemic Dendrocalamus manipureanus of Manipur, northeast India, using molecular and phytochemical markers. 15 inter simple sequence repeats (ISSR) and 11 start codon targeted (SCoT) primers produced 136 and 91 polymorphic bands, respectively, generating high polymorphism. 10 primers of inter primer binding site (iPBS) markers gave 94 polymorphic bands producing 100% polymorphism. The Mantel test showed no significant correlation between markers indicating the necessity of employing a combination of multiple markers in diversity assessment. Combined marker analysis showed high genetic differentiation among populations (Gst = 0.684) due to low gene flow (Nm = 0.230). Analysis of molecular variance (AMOVA) also disclosed high genetic variation (67%) among the population and low diversity (33%) within the populations. BARRIER analysis identified 9 putative genetic barriers separating D. manipureanus populations, affirming the possible hindrance to gene flow. Neighbor-joining dendrogram and principal coordinate analysis (PCoA) revealed the absence of mixed clustering patterns. Bayesian model STRUCTURE analysis grouped D. manipureanus populations into 7 genetic clusters (K = 7) with less admixture. GENELAND further assigned the bamboo genotypes into 9 different genetic pools, confirming a high level of genetic isolation among the populations. The phytochemical examination further validated the molecular diversity studies with a similar bamboo diversity profile generation. The positive correlation between the genetic and phytochemical distance (r = 0.62, P = 0.01) confirmed that the phytochemical investigation could substantiate molecular diversity studies. The measures recommended from the crucial genetic findings might be utilized for genetic improvement and management of the endemic bamboo in the region.

Unstable environment of coastal lagoons drives genetic variation in the amphipod Quadrivisio lutzi.

The freshwater/brackish amphipod Quadrivisio lutzi inhabits coastal lagoons, highly unstable environments subject to sudden inflow of marine water. Our aim was to evaluate how the genetic composition varies in these populations. Brazilian populations were compared by 16S rRNA and COI gene sequences. The genetic structure of four Rio de Janeiro amphipod populations was evaluated during the period of 2011-2019 by COI. Rio de Janeiro population was compared with Alagoas and São Paulo populations, which was genetically distinct, at species level (16S, d > 7%; COI, d >14%). The genetic structure in Rio de Janeiro showed the Imboassica subpopulation as the most divergent (Imboassica & Carapebus, F ST = 0.238), followed by Lagamar population (Lagamar & Carapebus, F ST = 0.049). The geographic distance and urbanization around these lagoons explain the degree of genetic isolation of these amphipod subpopulations. Paulista and Carapebus populations were not structured. Temporal variation in haplotype number and frequency were evident in both populations that were evaluated (Carapebus and Imboassica). Changes in salinity and water volume variation at these lagoons may be responsible for the observed changes in genetic composition, which may be the results of genetic drift effects over temporally fluctuating size subpopulations, without loss of genetic diversity.

Популяционно-генетическая структура степного орла: есть ли надежда на сохранение вида?

For centuries, Steppe Eagle (Aquila nipalensis) had been the most numerous Palearctic Aquila species, but nowadays it has been decreasing in numbers progressively, so in 2015 the IUCN changed the species status to “endangered”. The decrease is evidently related to Steppe Eagles’ electrocution at nesting areas and during migration, poisoning by veterinarian drugs when feeding on agricultural animal carcasses at wintering grounds, steppe fires and total habitat loss combined with loss of prey like susliks. To the contrary, the sister Aquila species, the Imperial Eagle (Aquila heliaca), which exhibits similar biological traits and lives simpatrically to the Steppe Eagle at some parts of areas, shows local increase in numbers and even substitutes the decreasing Steppe Eagle in steppe biomes. In the 1960s, many Palearctic birds of prey came through population decline due to so-called “DDT crisis” – massive pesticide poisoning. To restore the species numbers, specific conservation actions were initiated in Europe to support population numbers and genetic diversity of raptors. Regarding the Steppe Eagle with its nesting area located mostly at Kazakhstan, Russian, Mongolian and Chinese territories, the implications of DDT and electrocution impacts on the population numbers stayed poorly investigated. Meanwhile, loss of genetic stability can be a reason for lasting population decline. Genetic threats like population fragmentation, genetic erosion, and inbreeding depression are believed more prolonged in comparison to anthropogenic impacts and more rarely come under increasing scrutiny of conservation practitioners. However, if exist, they can lead to species extinction regardless of removal of all other threats. The Steppe Eagle population structure stays poorly investigated. In 2018, during the 1st Steppe Eagle conservation international workshop, this problem was highlighted with recommendations for filling this gap. Our presented study was conducted following this recommendation and focused on genetic structure, fragmentation, and effective number comparison of the Steppe Eagle population at the individual samples) and sympatric populations of the Imperial Eagle (over 100 samples). For conservation criteria estimation, we used widespread genetic markers like nuclear microsatellites (9 loci) and mitochondrial control region (D-loop). Also we performed molecular individual tagging and parentage analysis to study the population structure using samples from the numerous Western Kazakhstan population. We also used GIS methods to study geographic fragmentation of populations. The genetic analysis showed that the Steppe Eagle population structure is highly similar to that of the Imperial Eagle but with less genetic diversity and has traces of repeated survival of “population bottlenecks” with huge decline in the number and genetic diversity. Fragmentation analysis showed no genetic isolation of geographically fragmented nesting groups despite the presumed natal phylopatry in accordance with our Steppe Eagle parentage data. Preliminary estimation of the Steppe Eagle population effective numbers by linkage disequilibrium method showed rather high values inspite of the lasting population decline. The molecular coancestry estimation showed more serious decline during the latest bottleneck which was also far below the ancestral Imperial Eagle population at the studied areas. The inbreeding rate for the Steppe Eagle population at the most part of the species areas turned out to outnumber one for the local population of the Imperial Eagle. Our data showed no immediate genetic threats for the Steppe Eagle population restoration and also demonstrated traces of multiple bottlenecks in the species evolution. Still the genetic structure of the species population keeps some traits of modern decline and should be monitored permanently according to the species numbers. Unique population structure patterns of the Steppe Eagle between other Aquilinae species and their conservation aspects are directions for future Aquila nipalensis genetic research.

Tandem duplications, eupolyploidy and secondary diploidization – genetic mechanisms of plant speciation and progressive evolution

The article considers the genetic mechanisms of plant speciation. The importance of interspecific hybridization and polyploidy (whole genome duplication, WGD) as the main mechanisms of plant speciation is shown. There are three main ways of transformations of the hybrid genome associated with speciation. In the first way, the ploidy of the offspring does not change in comparison with the parents’ ploidy; the genomes of hybrid lines are stabilized through backcrosses and introgression without polyploidization. In the second way, the interspecial hybridization followed by whole genome duplication. Then, the initially unstable neopolyploid genome gradually passes into a stable eupolyploid state with the preservation of the polyploid number of chromosomes but with the diploid type of chromosome conjugation in meiosis. This is a widespread and rapid mechanism of plant speciation and genus formation in higher plants, which ensured the morphological and genetic isolation and adaptability of at least 15 % of modern species of higher plants. However, this is a path that usually does not lead to aromorphoses, this is speciation at an already achieved level of complexity. The third way of speciation is realized through dysploidy and secondary diploidization of the genome. In this case, the neopolyploid undergoes significant genomic rearrangements and loses most of the duplicated gene copies, its number of chromosomes is radically reduced. In different individuals of a species that has embarked on the path of stochastic genome fractionation and dysploidy, the initial genetic redundancy of various genome components multiplied after WGD is transformed in an unpredictably unique way, which leads to a radical increase in intraspecific genomic and epigenetic polymorphism and provides rich material for natural selection. It was also shown that in eupolyploids and paleopolyploids, a significant role in heritable adaptations to environmental conditions and in anatomical and morphological innovations is played by segment and tandem duplications not associated with WGD. Some of the paleopolyploids, which turned out to be evolutionarily progressive morphotypes, possessing aromorphoses with diploidized genomes, give rise to new phylogenetic branches, new suprageneric taxa. The article proposes to assign both genera carrying a unique two-chromosomal genome Zingeria and Colpodium (x = 2; 2n = 4, 8, 12) into subtribe Zingeriinae Rodionov, subtrib. nov. – Type: Zingeria P. A. Smirn. In addition, the accomodation of the genera Helictochloa and Molineriella into one subtribe Helictochloinae Röser et Tkach seems to us unreasonable from a genomic point of view, since the fundamental difference between representatives of these two genera is that Molineriella species carry an unusual 4-chromosomal genome, while speciation in genus Helictochloa(2n = 14 – 154) goes through the combinations of different 7-chromosome subgenomes, denoted by the letters E, L, B, C, M, V, G, U. Therefore, we consider it necessary to assign Molineriella into a monogenic subtribe MolineriellinaeRodionov, subtrib. nov. – Type: Molineriella Rouy.

Rear‐edge daylily populations show legacies of habitat fragmentation due to the Holocene climate warming

AbstractAimsQuaternary climate changes dramatically affected species' distributions and thus impacted genetic diversity patterns, particularly for rear‐edge populations. Empirical studies have shown the southernmost (rear‐edge), fragmented populations of Japanese woody plants can harbour high genetic diversity owing to their origin in southern glacial refugia. The effect of Holocene climate warming on rear‐edge populations has, however, rarely been demonstrated. We assessed whether the genetic structure of populations of temperate plants in Japan can be interpreted to show legacies of both icy (Last Glacial Maximum, LGM) and warm (Holocene) climates.LocationJapanese Archipelago.TaxonHemerocallis middendorffii (Asphodelaceae).MethodsPopulation genetic profiles of 737 individuals from 41 populations were analysed to examine population structure and past population demography, using 12 EST‐SSR markers. Present and past suitable habitat areas during the LGM and the Holocene climatic optimum were estimated by ecological niche modelling (ENM). Reconstructed palaeodistribution was combined with population genetics to statistically predict population demographics in relation to past climate changes.ResultsGenetic analysis of the 41 populations revealed 6 regional population groups. Four groups widely dominating the northern–central ranges harboured high genetic diversity, whereas genetic divergence within the groups was low. In contrast, the two groups at the southwestern edge were geographically and genetically isolated, and they showed the lowest genetic diversity. The estimated palaeodistributions showed a decrease in the suitable range during the Holocene in comparison with that at the LGM, and only habitat suitability in the Holocene was able to predict the genetic diversity across the range.Main conclusionsPopulations at the centre of the current distribution harbour high genetic diversity because they remained stable during both cold and warm periods. However, habitat fragmentation and population decline in relation to climate warming during the Holocene resulted in genetic isolation and impoverishment of the rear‐edge populations.

Analysis of genetic diversity of valuable walnut species collected at N.V. Tsitsin Main Botanical Garden of the Russian Academy of Sciences Using SSR markers

Walnut is one of the most economically significant nut crops. Evaluation of the genetic structure of the domestic walnut gene plasma using modern molecular genetic approaches is a relevant research task. The walnut samples collected by Tsitsin Main Moscow Botanical Garden of Academy of Sciences (MBG RAS) are of particular importance for breeding practice aimed at increasing winter freezing tolerance of plants. The seed material for this collection was introduced from different regions of the former Soviet Union, including Tajikistan, Kyrgyzstan, Ukraine, Belarus, as well as regions of Russia. The MBG RAS collection presents interest as a breeding material for mobilizing the genetic resources and replenishing the gene pool of the South of Russia with new, economically valuable walnut varieties. This work aims to analyze the genetic diversity of a J. regia genotype sample, which includes the most valuable forms from the MBG RAS collection, in order to establish their genetic relationships with samples representing the walnut gene pool of the South of Russia. The genetic analysis of the studied walnut species and varieties was carried out using eight SSR markers: WGA001, WGA376, WGA069, WGA276, WGA009, WGA202, WGA089, and WGA054. The polymorphism of microsatellite DNA markers established during genotyping indicated a high heterogeneity between the MBG RAS walnut sample and genetic resources in other regions. An analysis of genetic relationships using UPGMA and PCoA clustering methods revealed the genetic isolation of most samples in the MBG RAS collection from walnut varieties in the South of Russia. The most genetically distant samples in the MBG RAS collection were found to be 199, 196, 236, 256, 106, and 134. Therefore, these samples should be introduced in the gene pool of North-Caucasus Federal Scientific Center of Horticulture, Viticulture, and Wine-making and Nikitsky Botanical Garden with the purpose of increasing the heterogeneity of their gene pools.

Dolutegravir-Based Regimen Ensures High Virological Success despite Prior Exposure to Efavirenz-Based First-LINE ART in Cameroon: An Evidence of a Successful Transition Model.

To ensure optimal prescribing practices in the dolutegravir-era in Cameroon, we compared first-line virological response (VR) under tenofovir + lamivudine + dolutegravir (TLD) according to prior exposure to tenofovir + lamivudine + efavirenz (TLE). A facility-based survey was conducted among patients initiating antiretroviral therapy (ART) with TLD (I-TLD) versus those transitioning from TLE to TLD (T-TLD). HIV viral load was performed and unsuppressed participants (VL > 1000 copies/mL) had genotyping performed by Sanger sequencing. Of the 12,093 patients followed, 310 (mean-age: 41 ± 11 years; 52.26% female) complied with study criteria (171 I-TLD vs. 139 T-TLD). The median ART-duration was 14 (12−17) months among I-TLDs versus 28 (24.5−31) months among T-TLDs (15 (11−19) on TLE and 14 (9−15) on TLD), and 83.15% (148/178) were at WHO clinical stages I/II. The viral suppression rate (<1000 copies/mL) was 96.45%, with 97.08% among I-TLDs versus 95.68% among T-TLDs (p = 0.55). VR was similar in I-TLD versus T-TLD at <400 copies/mL (94.15% versus 94.42%) and age, gender, residence, ART-duration, and WHO stages were not associated with VR (p > 0.05). Genotyping was successful for 72.7% (8/11), with no major mutations to integrase inhibitors found. VR is optimal under first-line TLD after 14 months, even among TLE-exposed, thus confirming the effectiveness of transitioning from TLE to TLD in similar settings, supported by strong pharmacological potency and genetic barrier of dolutegravir.

Effects of fruit dimorphism on genetic structure and gene flow in the coastal shrub Scaevola taccada.

Plant propagules often possess specialized morphologies that facilitate dispersal across specific landscapes. In the fruit dimorphism of a coastal shrub, Scaevola taccada, individual plants produce either cork-morph or pulp-morph fruits. The former is buoyant and common on sandy beaches, whereas the latter does not float, is bird-dispersed, and is common on elevated sites such as slopes on sea cliffs and behind rocky shores. We hypothesized that beach populations bridge the heterogeneous landscapes by serving as a source of both fruit types, while dispersal is biased for the pulp morph on elevated sites within the islands and for the cork morph between beaches of different islands. Based on this hypothesis, we predicted that populations in elevated sites would diverge genetically over time due to isolation by distance, whereas beach populations would maintain high genetic similarity via current gene flow. The genetic structure and gene flow in S. taccada were evaluated by investigating genome-wide single nucleotide polymorphisms in plants from 17 sampling sites on six islands (belonging to the Ryukyu, Daito and Ogasawara Islands) in Japan. Geographical isolation was detected among the three distant island groups. Analyses within the Ryukyu Islands suggested that sandy beach populations were characterized by genetic admixture, whereas populations in elevated sites were relatively isolated between the islands. Pairwise FST values between islands were lowest between sandy beaches, intermediate between sandy beaches and elevated sites, and highest between elevated sites. Dispersal across the ocean by cork morphs is sufficiently frequent to prevent genetic divergence between beaches of different islands. Stronger genetic isolation of elevated sites between islands suggests that bird dispersal by pulp morphs is restricted mainly within islands. These contrasting patterns of gene flow realized by fruit dimorphism provide evidence that fruit characteristics can strongly mediate genetic structure.

1160. Treatment-Emergent Viral Variants in the Phase 3 TACKLE Trial Investigating Efficacy and Safety of AZD7442 (Tixagevimab/Cilgavimab) for the Treatment of Mild to Moderate COVID-19 in Adults

Abstract Background AZD7442 (tixagevimab/cilgavimab) is a combination of neutralizing monoclonal antibodies (mAbs) that bind to distinct epitopes on the SARS-CoV-2 spike protein, with neutralization activity against variants including Omicron. In the Phase 3 TACKLE study, AZD7442 significantly reduced severe disease progression or death and was well-tolerated through Day 29. Viral evolution during treatment has the potential for resistance selection, such as variants exhibiting reduced mAb binding. We report genotypic analysis and phenotypic characterization of variants identified over 15 days after AZD7442 treatment in TACKLE. Methods In TACKLE (NCT04723394), non-hospitalized adults with mild to moderate COVID19 were randomized and dosed ≤7 days from symptom onset with a single 600-mg AZD7442 dose (2 consecutive intramuscular injections, 300 mg of each antibody; n=452) or placebo (n=451). Next-generation sequencing of the spike gene was performed on SARS-CoV-2 reverse-transcription polymerase chain reaction–positive nasal swabs (at baseline and Days 3, 6, and 15). SARS-CoV-2 lineages were assigned using spike nucleotide sequences. Amino acid substitutions, insertions, and deletions were analyzed at allele fractions (AF, % of sequence reads represented by mutation) ≥25% and 3–25%. Results Baseline spike sequences were available from 744 participants (82.4%) (AZD7442, n=380; placebo, n=364); 87% of sequences corresponded to variants of concern/interest; these were balanced between AZD7442 and placebo groups (Table 1). Treatment-emergent (post-dosing) viral variants were rare, with 11 (4.5%) AZD7442 and 3 (1.3%) placebo participants showing the emergence of ≥1 mutation at tixagevimab/cilgavimab binding sites, with an AF ≥25% (Table 2). At AF 3–25%, treatment-emergent viral variants in the AZD7442 binding site were observed in 16 (6.6%) AZD7442 and 15 (6.5%) placebo participants. Conclusion Following AZD7442 treatment, low levels of SARS-CoV-2 variants bearing mutations at tixagevimab/cilgavimab binding sites were identified. These data indicate that combination of two antibodies creates a high genetic barrier for resistance, supporting the use of mAb combinations that bind to distinct epitopes for the treatment of COVID-19. Disclosures Gustavo H. Kijak, PharmD PhD, AstraZeneca: Employee|AstraZeneca: Stocks/Bonds Bahar Ahani, BSC, AstraZeneca: Employee|AstraZeneca: Stocks/Bonds Douglas Arbetter, MPH, AstraZeneca: Employee|AstraZeneca: Stocks/Bonds Tyler Brady, MS, AstraZeneca: Employee|AstraZeneca: Stocks/Bonds Fernando Chuecos, BS, AstraZeneca: Employee|AstraZeneca: Stocks/Bonds Vancheswaran Gopalakrishnan, PhD, AstraZeneca: Employee|AstraZeneca: Stocks/Bonds Tiffany L. Roe, B.S., AstraZeneca: Employee|AstraZeneca: Stocks/Bonds Nicolette Schuko, MS, AstraZeneca: Employee|AstraZeneca: Stocks/Bonds F.D. Richard Hobbs, FMedSci, AstraZeneca: Grant/Research Support|AstraZeneca: Principal investigator|NIHR Applied Research Collaboration, Oxford Thames Valley: Director|Oxford BRC and NIHR MedTech: Investigator|UKRI and NIHR: Grant/Research Support Francisco Padilla, MD, Amgen: Grant/Research Support|Amgen: Personal fees|AstraZeneca: Grant/Research Support|AstraZeneca: Personal fees|Boehringer Ingelheim: Grant/Research Support|Boehringer Ingelheim: Personal fees|Ferrer: Grant/Research Support|Ferrer: Personal fees|Kowa: Grant/Research Support|Kowa: Personal fees|Medix: Grant/Research Support|Medix: Personal fees|Merck Sharp and Dohme: Grant/Research Support|Merck Sharp and Dohme: Personal fees|Novartis: Grant/Research Support|Novartis: Personal fees|Pfizer: Grant/Research Support|Pfizer: Personal fees|Sanofi: Grant/Research Support|Sanofi: Personal fees|Servier: Grant/Research Support|Servier: Personal fees|Silanes: Grant/Research Support|Silanes: Personal fees Elizabeth J. Kelly, PhD, AstraZeneca: Employee|AstraZeneca: Stocks/Bonds Hugh Montgomery, MD, AstraZeneca: Advisor/Consultant|Millfield Medical Ltd: Advisor/Consultant|UK National Institute for Health Research's Comprehensive Biomedical Research Centre at University College London Hospitals: Grant/Research Support Katie Streicher, PhD, AstraZeneca: Employee|AstraZeneca: Stocks/Bonds.

820 VARIABLE EXPRESSIVITY OF SCN5A MUTATION IN A FAMILY WITH CARDIAC DYSFUNCTION AND SUSPECTED BRUGADA SYNDROME

Abstract Background Inherited arrhythmogenic diseases (IADs) represent a group of life-threatening genetic cardiomyopathies that predispose young individuals to sudden cardiac death (SCD), often in the absence of structural cardiac alterations. Some IADs share mutations in genes encoding for surface membrane ion channels, and the gene for the alpha subunit of the voltage-dependent channel Nav1.5 (SCN5A) is among the ones mostly involved. Brugada syndrome represents one of the possible spectrum deriving from SCN5A gene mutations, and it is characterized by “loss-of-function” genetic alterations. Interestingly, both loss-of and gain-of-function mutations have been associated with familial dilated cardiomyopathy (DCM). Materials and Methods In the context of an Italian Ministry of Health-funded research project devoted to identify genetic isolates of IADs in the Calabria region, we found a family affected by different cardiovascular manifestations including cardiac dysfunction, ventricular tachyarrhythmias, atrioventricular block and suspected Brugada syndrome pattern in first-degree relatives in association with a newly identified SCN5A mutation. Results The proband came to our attention with a diagnosis of DCM, echocardiographic assessment of reduced left ventricular ejection fraction (EF) to 38%, high occurrence of premature ventricular complexes (PVCs) and first-degree atrioventricular block (PR = 240ms) at electrocardiogram. In spite of negative electrophysiologic study, he underwent implantable cardioverter defibrillator implantation (ICD), hypothesizing lamin A/C mutation; genetic analysis turned out negative for lamin A/C and CACNA1C, while a SCN5A gene mutation (c.4554 G&amp;lt;T p.Gln1518His) was detected. Proband's sons and his brother underwent clinical evaluations as well as genetic testing: the second son's ECG showed first-degree AV block (PR = 220ms), QTc interval 426ms, and coved type ST-segment elevation of 1.5mm, in the context of normal cardiac function; the remaining male (see Figure 1) was asymptomatic, while the daughter had a hypokinetic non-dilated cardiomyopathy. The proband's brother had first-degree AV block and very frequent monomorphic ventricular couplets. Conclusions These phenotypic differences in first degree-relatives, can be explained by the concept of variable expressivity of genes, according to which individuals carrying the same mutation can have different clinical features. Therefore, the search for genetic mutations assumes a preponderant role for stratifying the risk of SCN5A-related diseases and to adopt appropriate diagnostic and therapeutic strategies.

Adipocyte differentiation of 3T3-L1 cells under tenofovir alafenamide, tenofovir disoproxil fumarate, and integrase strand transfer inhibitors selective challenge: an in-vitro model.

Integrase strand transfer inhibitors (INSTIs) are a class of antiretroviral therapy (ART) medications with a good tolerability profile and a high genetic barrier to HIV drug resistance. However, several studies report significant weight gain among persons receiving INSTI-based ART regimens compared with other regimens. In-vitro model of adipogenesis. We used 3T3-L1 cells to investigate the effects of the nucleoside reverse transcriptase inhibitors (NRTIs) tenofovir disoproxil fumarate (TDF) and tenofovir alafenamide (TAF), alone or in combination with INSTIs: raltegravir (RAL), elvitegravir (ELV), dolutegravir (DTG), and bictegravir (BIC) on adipose differentiation. To monitor adipocyte differentiation, expression levels of PPARɣ and C/EBPα and the intracellular lipid accumulation by Red Oil staining were used. Furthermore, we evaluated the immunohistochemical expression of ER-TR7, a fibroblastic marker, after INSTIs treatment. Compared with control, INSTIs were able to increase adipogenesis, especially RAL and ELV. TAF and TDF inhibited adipogenesis alone and in combination with INSTIs. This ability was more evident when TAF was used in combination with DTG and BIC. Finally, INSTIs increased the expression of ER-TR7 compared with control and cells treated with TAF or TDF. Our data support the evidence that in-vitro challenge of 3T3-L1 cells with INSTIs is able to increase adipocytic differentiation and to drive a number of these cells toward the expression of fibroblastic features, with a different degree according to the various drugs used whereas TAF and TDF have an antagonistic role on this phenomenon.

Plasma pTau181 is associated with impaired cognition in the Old Order Amish and adds additional information beyond the known genetic risk factors for AD

AbstractBackgroundAs plasma biomarker assays have become more widely available, they are increasingly being used to characterize AD and related dementias. The Old Order Amish are a cultural and genetic isolate in the US that have participated in genetic studies for decades. This study investigated plasma phosphorylated tau at threonine‐181 (pTau181) in an Old Order Amish cohort to determine if the association with cognitive status is reproducible in this population.MethodOld Order Amish individuals over age 65 (n=467, mean age = 81.3, 60.6% female) in Indiana and Ohio were examined using a modified Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) battery. Each individual was assigned Impaired (n=155, mean age = 82.5, 56.8% female) or Unimpaired (n=312, mean age = 80.8, 62.5% female) cognitive status via consensus review of these examination results. The level of plasma pTau181 was measured using the pTau181 Advantage V2 assay from Quanterix. Genetic Risk Scores (GRS) were calculated using genome‐wide significant variants from Kunkle et al. (2019), weighted by log odds ratio estimates. A t‐test was used to compare plasma pTau181 levels between the Impaired and Unimpaired groups. Logistic regression was then used to model the contribution of age, sex, GRS, and plasma pTau181 on cognitive status.ResultWe found that the average level of plasma pTau181 was significantly higher in the Impaired group (2.46 pg/mL) compared to the Unimpaired group (2.01 pg/mL) at p&lt;0.0001. A multivariable model found increasing age (OR=1.10, p=0.0002), male sex (OR=1.60, p=0.04), increasing GRS (OR=1.97, p&lt;0.0001), and increasing plasma pTau181 (OR=1.46, p=0.001) associated with impaired cognitive status. The effect of GRS is mostly attributable to APOE.ConclusionThe result of these analyses indicates that pTau181 is associated with impaired cognitive status in the Old Order Amish, adding additional information beyond the known genetic risk factors for AD.

Genetic landscape of ALS in Malta based on a quinquennial analysis

Genetic risk for amyotrophic lateral sclerosis (ALS) is highly elevated in genetic isolates, like the island population of Malta in the south of Europe, providing a unique opportunity to investigate the genetics of this disease. Here we characterize the clinical phenotype and genetic profile of the largest series of Maltese ALS patients to date identified throughout a 5-year window. Cases and controls underwent neuromuscular assessment and analysis of rare variants in ALS causative or risk genes following whole-genome sequencing. Potentially damaging variants or repeat expansions were identified in more than 45% of all patients. The most commonly affected genes were ALS2, DAO, SETX and SPG11, an infrequent cause of ALS in Europeans. We also confirmed a significant association between ATXN1 intermediate repeats and increased disease risk. Damaging variants in major ALS genes C9orf72, SOD1, TARDBP and FUS were however either absent or rare in Maltese ALS patients. Overall, our study underscores a population that is an outlier within Europe and one that represents a high percentage of genetically explained cases.

An isolated population reveals greater genetic structuring of the Australian dingo

The Australian dingo is a recent anthropogenic addition to the Australian fauna, which spread rapidly across the continent and has since widely interbred with modern dogs. Genetic studies of dingoes have given rise to speculation about their entry to the continent and subsequent biogeographic effects, but few studies of their contemporary population structure have been conducted. Here we investigated the dingo ancestry and population structure of free-living dogs in western Victoria and contrasted it with a wider southern Australian sample. We wished to determine whether their geographic isolation was mirrored in genetic isolation. To address this question, we analysed 34 microsatellite markers using Bayesian clustering and discriminant analysis of principal components, and summarised genetic diversity at the population and individual level. The broader southern Australia sample (n = 1138) comprised mostly hybrid animals, with 30% considered pure dingoes. All western Victorian individuals (n = 59) appeared to be hybrids with high dingo ancestry. The population showed no evidence of admixture with other populations and low genetic diversity on all measures tested. Based upon our characterisation of this unusual mainland population, we advise against assuming homogeneity of dingoes across the continent.