A gain-of-function mutation in the cardiac pacemaker HCN4 channel increasing cAMP sensitivity is associated with familial Inappropriate Sinus Tachycardia

Aims Inappropriate Sinus Tachycardia (IST), a syndrome characterized by abnormally fast sinus rates and multisystem symptoms, is still poorly understood. Because of the relevance of HCN4 channels to pacemaker activity, we used a candidate-gene approach and screened IST patients for the presence of disease-causing HCN4 mutations. Methods and results Forty-eight IST patients, four of whom of known familial history, were enrolled in the study. We initially identified in one of the patients with familial history the R524Q mutation in HCN4. Investigation extended to the family members showed that the mutation co-segregated with IST-related symptoms. The R524Q mutation is located in the C-linker, a region known to couple cAMP binding to channel activation. The functional relevance of the mutation was investigated in heterologous expression systems by patch-clamp experiments. We found that mutant HCN4 channels were more sensitive to cAMP than wild-type channels, in agreement with increased sensitivity to basal and stimulated adrenergic input and with a faster than normal pacemaker rate. The properties of variant channels indicate therefore that R524Q is a gain-of-function mutation. Increased channel contribution to activity was confirmed by evidence that when spontaneously beating rat newborn myocytes were transfected with R524Q mutant HCN4 channels, they exhibited a faster rate than when transfected with wild-type HCN4 channels. Conclusion This is the first report of a gain-of-function HCN4 mutation associated with IST through increased sensitivity to cAMP-dependent activation

Evidence of Polygenic Adaptation to High Altitude from Tibetan and Sherpa Genomes

Although Tibetans and Sherpa present several physiological adjustments evolved to cope with selective pressures imposed by the high-altitude environment, especially hypobaric hypoxia, few selective sweeps at a limited number of hypoxia related genes were confirmed by multiple genomic studies. Nevertheless, variants at these loci were found to be associated only with downregulation of the erythropoietic cascade, which represents an indirect aspect of the considered adaptive phenotype. Accordingly, the genetic basis of Tibetan/Sherpa adaptive traits remains to be fully elucidated, in part due to limitations of selection scans implemented so far and mostly relying on the hard sweep model.In order to overcome this issue, we used whole-genome sequence data and several selection statistics as input for gene network analyses aimed at testing for the occurrence of polygenic adaptation in these high-altitude Himalayan populations. Being able to detect also subtle genomic signatures ascribable to weak positive selection at multiple genes of the same functional subnetwork, this approach allowed us to infer adaptive evolution at loci individually showing small effect sizes, but belonging to highly interconnected biological pathways overall involved in angiogenetic processes.Therefore, these findings pinpointed a series of selective events neglected so far, which likely contributed to the augmented tissue blood perfusion observed in Tibetans and Sherpa, thus uncovering the genetic determinants of a key biological mechanism that underlies their adaptation to high altitude

A Loss-of-Function HCN4 Mutation Associated With Familial Benign Myoclonic Epilepsy in Infancy Causes Increased Neuronal Excitability

HCN channels are highly expressed and functionally relevant in neurons and increasing evidence demonstrates their involvement in the etiology of human epilepsies. Among HCN isoforms, HCN4 is important in cardiac tissue, where it underlies pacemaker activity. Despite being expressed also in deep structures of the brain, mutations of this channel functionally shown to be associated with epilepsy have not been reported yet. Using Next Generation Sequencing for the screening of patients with idiopathic epilepsy, we identified the p.Arg550Cys (c.1648C>T) heterozygous mutation on HCN4 in two brothers affected by benign myoclonic epilepsy of infancy. Functional characterization in heterologous expression system and in neurons showed that the mutation determines a loss of function of HCN4 contribution to activity and an increase of neuronal discharge, potentially predisposing to epilepsy. Expressed in cardiomyocytes, mutant channels activate at slightly more negative voltages than wild-type (WT), in accordance with borderline bradycardia. While HCN4 variants have been frequently associated with cardiac arrhythmias, these data represent the first experimental evidence that functional alteration of HCN4 can also be involved in human epilepsy through a loss-of-function effect and associated increased neuronal excitability. Since HCN4 appears to be highly expressed in deep brain structures only early during development, our data provide a potential explanation for a link between dysfunctional HCN4 and infantile epilepsy. These findings suggest that it may be useful to include HCN4 screening to extend the knowledge of the genetic causes of infantile epilepsies, potentially paving the way for the identification of innovative therapeutic strategies

Ancient genomes reveal origin and rapid trans-Eurasian migration of 7^th century Avar elites

The Avars settled the Carpathian Basin in 567/68 CE, establishing an empire lasting over 200 years. Who they were and where they came from is highly debated. Contemporaries have disagreed about whether they were, as they claimed, the direct successors of the Mongolian Steppe Rouran empire that was destroyed by the Turks in ∼550 CE. Here, we analyze new genome-wide data from 66 pre-Avar and Avar-period Carpathian Basin individuals, including the 8 richest Avar-period burials and further elite sites from Avar’s empire core region. Our results provide support for a rapid long-distance trans-Eurasian migration of Avar-period elites. These individuals carried Northeast Asian ancestry matching the profile of preceding Mongolian Steppe populations, particularly a genome available from the Rouran period. Some of the later elite individuals carried an additional non-local ancestry component broadly matching the steppe, which could point to a later migration or reflect greater genetic diversity within the initial migrant population.- Introduction - Results -- Ancient DNA dataset and quality control -- The genomic structure of the pre-Avar-period population -- The genomic structure of the Avar-period population -- Modeling the eastern steppe ancestry of the elites in the core of the Avar empire -- The heterogeneous ancestry in the regions surrounding the Avar empire’s core - Discussion -- Limitations of the study - Star Method

Ten millennia of hepatitis B virus evolution

Hepatitis B virus (HBV) has been infecting humans for millennia and remains a global health problem, but its past diversity and dispersal routes are largely unknown. We generated HBV genomic data from 137 Eurasians and Native Americans dated between ~10,500 and ~400 years ago. We date the most recent common ancestor of all HBV lineages to between ~20,000 and 12,000 years ago, with the virus present in European and South American hunter-gatherers during the early Holocene. After the European Neolithic transition, Mesolithic HBV strains were replaced by a lineage likely disseminated by early farmers that prevailed throughout western Eurasia for ~4000 years, declining around the end of the 2nd millennium BCE. The only remnant of this prehistoric HBV diversity is the rare genotype G, which appears to have reemerged during the HIV pandemic

Ancient DNA reveals admixture history and endogamy in the prehistoric Aegean (advance online)

The Neolithic and Bronze Ages were highly transformative periods forthe genetic history of Europe but for the Aegean—a region fundamentalto Europe’s prehistory—the biological dimensions of cultural transitionshave been elucidated only to a limited extent so far. We have analysed newlygenerated genome-wide data from 102 ancient individuals from Crete, theGreek mainland and the Aegean Islands, spanning from the Neolithic tothe Iron Age. We found that the early farmers from Crete shared the sameancestry as other contemporaneous Neolithic Aegeans. In contrast, the endof the Neolithic period and the following Early Bronze Age were marked by‘eastern’ gene flow, which was predominantly of Anatolian origin in Crete.Confirming previous findings for additional Central/Eastern Europeanancestry in the Greek mainland by the Middle Bronze Age, we additionallyshow that such genetic signatures appeared in Crete gradually from theseventeenth to twelfth centuries bc, a period when the influence of themainland over the island intensified. Biological and cultural connectednesswithin the Aegean is also supported by the finding of consanguineousendogamy practiced at high frequencies, unprecedented in the globalancient DNA record. Our results highlight the potential of archaeogenomicapproaches in the Aegean for unravelling the interplay of genetic admixture,marital and other cultural practice

Ten millennia of hepatitis B virus evolution

Hepatitis B virus (HBV) has been infecting humans for millennia and remains a global health problem, but its past diversity and dispersal routes are largely unknown. We generated HBV genomic data from 137 Eurasians and Native Americans dated between similar to 10,500 and similar to 400 years ago. We date the most recent common ancestor of all HBV lineages to between similar to 20,000 and 12,000 years ago, with the virus present in European and South American hunter-gatherers during the early Holocene. After the European Neolithic transition, Mesolithic HBV strains were replaced by a lineage likely disseminated by early farmers that prevailed throughout western Eurasia for similar to 4000 years, declining around the end of the 2nd millennium BCE. The only remnant of this prehistoric HBV diversity is the rare genotype G, which appears to have reemerged during the HIV pandemic.Molecular Technology and Informatics for Personalised Medicine and Healt