Browsing by Autor "Jihyun Song"

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Andean Aymara Enriched Genetic Variants Are Beneficial to High Altitude Adaptation of Andean Quechuas Living at 5000 m
(Elsevier BV, 2022) Ricardo Amaru; Emerson Cayo; Julieta Luna; Teddy Quispe; Josef T. Prchal; Jihyun Song
Populations living at high altitude developed distinct evolutionary genetic adaptations allowing them to exist in extreme hypobaric hypoxia condition. Tibetans and Andean highlanders (Aymaras and Quechuas) have inhabited regions over ~4000 m for 44,000 and 14,000 years, respectively (PMID: 28448578, 25342802). Unlike other high-altitude populations, such as Tibetans, Andeans' Aymaras and Quechuas have higher hemoglobin levels. Tibetan genomic analyses revealed evolutionary selected genetic signatures EPAS1, EGLN1 and PKLR genes (PMID:25129147; Song, ASH 2018). However non-DenisovanEPAS1 variants (rs13005507 and rs142764723) are present in Aymaras and Quechuas, and ~56% of Aymaras have Tibetan PKLR variants (Song, ASH 2018). Our whole genome study found that most Aymara evolutionary-enriched genes (BRNIP3, NOS2, SH2B1, and TBX5) are associated with cardiopulmonary development but not with hemoglobin levels (PMID: 29100088); different genomic selection was reported in Andean Quechuas (PMID:23954164). We then found previously unreported Aymara enriched NFKB1 single nucleotide polymorphisms (SNP) by integrative analysis of the Aymaras' genome and transcriptome, this SNP is also enriched in Quechuas but to the lesser degree. Decreased NFKB1 results in increased NF-kB levels leading to NF-kB driven increased inflammation as well as increased HIFs activity (PMID: 26513405) and is associated with high hemoglobin and inflammatory protein and transcript levels in Aymaras (Song, ASH 2018). We studied the presence of Aymara enriched SNPs in Quechua, one of Andean population living in Chorolque (5000 m) and their association with phenotypes at high altitude. We genotyped 5 Aymara enriched SNPs and PKLR (Table) in Quechuas (45 men, 14 women) living in Chorolque (5000 m) mining district, Potosi-Bolivia. All men were smokers while none of women were smokers. We also measured laboratory phenotypes leukocytes, platelets, lymphocytes, monocytes, neutrophils, as well as hemoglobin dissociation p50, SpO2, lactose, hemoglobin and hematocrit to study if genetic variants play a role in changes in these phenotypes. All Aymara enriched allele frequencies in Quechuas were lower than in Aymaras (Table). The allele frequencies of BRINP3, SH2B1, TBX5 in Quechuas were significantly different from those in Aymara, suggesting that Quechuas share some but not all genetic background with Aymaras. Since all men were smokers, we tested smoking effect on these phenotypes. Except hemoglobin and hematocrit levels, other phenotypes were comparable to women without smoking history. BRINP3 SNP positively correlated with SpO2 levels (r=0.2252, p=0.0893), suggesting that this SNP may have a role in delivery oxygen to tissue. PKLR SNP is associated with decreased levels of pyruvate kinase transcript levels, leading to increase 2,3 DPG and shifting hemoglobin dissociation curve to the right (increase of p50) (Song, ASH 2018). However, in these subjects, we did not find association in p50 but positive correlation with SpO2 (r=0.3423, p=0.0082). It suggests that presence of BRINP3 and PKLR SNPs is beneficial to live at low oxygen tension by delivering more oxygen to tissues. Total leukocytes, lymphocytes, and neutrophils were negatively correlated with NFKB1 SNP (r=-0.2349, r=-0.281, and r=-0.1725, respectively) which differed from our previous study of Aymaras at La Paz, suggesting that Quechuas may have different mechanisms in responding to inflammation from Aymaras. None of SNPs were associated with hematocrit and hemoglobin levels in men; however, we could not exclude effect of smoking. In females, NOS2 SNP were positively correlated with both hemoglobin and hematocrit (r=0.5513, p=0.0246). NO (nitric oxide) synthesized by NOS2 inhibits erythropoiesis (PMID: 18282521), suggesting that NOS2 SNP may decrease NO production resulting in inducing erythropoiesis in Quechuas. We conclude that while Quechuas and Aymaras share some genetic variants, but they differ in degree of selection for these SNPs. BRINP3 and PKLR SNPs are helpful to transfer more oxygen to tissues at high altitude. NFKB1 SNPs` inverse correlation with immune cells may provide protective functions in response to increased inflammation at high altitude (PMID: 26855492). Decreased NO production by NOS2 SNP may augment erythropoiesis in Quechuas, resulting in their higher hemoglobin and hematocrit at high altitude compared to Europeans. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal
Andean high-altitude dwellers with the NFKB1 haplotype (rs230511) are protected from acute mountain sickness
(Elsevier BV, 2025) Ricardo Amaru; Javier Valencia; Edgar Teddy Quispe Soto; Emerson Cayo; Julieta Luna; Daniela Patón; Victor R. Gordeuk; Josef T. Prchal; Jihyun Song
Abstract Acute Mountain Sickness (AMS) occurs with rapid ascent to high altitudes (&gt;2,500m), where air and oxygen pressures are lower than at sea level. AMS symptoms are headache, loss of appetite, nausea, dizziness, insomnia, fatigue and chest tightness, but severe AMS can progress to cerebral edema or pulmonary edema (PMID:26294748). Hypoxia at high altitude activates inflammatory pathways in which NF-κB signaling plays a central role. Severe hypoxia (1–3% O2) induces NF-κB-driven production of inflammatory mediators, connecting hypoxia-induced stress mediated by hypoxia-inducible factors (HIFs) with NF-κB. HIFs are also involved in responses that increase pulmonary vascular permeability, pulmonary hypertension, and edema (PMIDs:11441701;3410239;18641050). HIFs increase blood-brain barrier permeability, a central feature of high-altitude cerebral edema (PMID:33856254). NFKB1 is part of NF-κB complex and modulates NF-κB activity. NFKB1 also augments activity of HIFs. In our study of evolutionary adaptation to extreme high altitude of Andean native Aymara who have higher hemoglobin than Europeans living at the same high-altitude (PMIDs: 24039843; 29100088), we reported that the evolutionary selected T allele of NFKB1 rs230511 haplotype is linked to previously unreported alternate splicing of NFKB1, including skipping exon 4, exon 5, or both exons 4 and 5. It is present in ~90% of Aymara, but it also exists at lower frequency in Europeans, Asians and Hispanics (~30%). These alternatively spliced NFKB1 transcripts result in partial or complete loss of NFKB1 protein expression. This Aymara NFKB1haplotype is associated with increased baseline expression of inflammatory and HIF-regulated genes and correlates with those Aymara having high hemoglobin. However, under inflammatory stress, it has the opposite effect: nuclear translocation of NF-kB protein is attenuated, resulting in reduced expression of inflammatory, HIF-regulated, and prothrombotic genes (PMID:39971917). Since the incidence of AMS in the Aymara population is 0.6 % (Viruez, Horiz Med [Lima] 2020; 20(3): e943), which is markedly lower than the 1.7 % observed in non-Aymara at the same altitude (Castellanos, Correo Científico Médico 2022; 26), we hypothesized that rs230511-T is also associated with a protective role for AMS in Aymara. We studied 35 Bolivian Aymara in LaPaz (altitude of 4000 meters) who relocated to lower altitudes (&lt;400 m) for 1 month to 5 years and then returned to 4000 m and developed AMS. Among 35 subjects, 10 participants- 5 women (age 29±14 years) and 5 men (age 39±8 years)- without a history of medical comorbidities (except for one having history of gout) developed AMS. The 25 subjects who did not develop AMS served as controls (7 women, age 40±14 years and 18 men, age 38±11 years). All participants were genotyped for the NFKB1(rs230511) and NOS2 (rs34913965) variants; NOS2 was included due to a potential relationship with AMS (PMID:29100088). Among the subjects who developed AMS, the allele frequencies for the Aymara-enrichedNFKB1 variant were C:0.75 and T:0.25, compared to C:0.0 and T:1.0 in the control group (p&lt;0.0001). The genotype frequencies were CC:50%, CT:50% and TT:0% in the AMS group and CC:0%, CT:0% and TT:100% in the control group (p&lt;0.0001). For the NOS2 C/T haplotype variant, analysis of 7 AMS patients revealed that allele frequencies (T-Aymara enriched allele PMID:29100088) were C:0.14 and T:0.86, compared to C:0.1 and T:0.9 in the control group (p=0.5146). The genotype frequencies were CC:0%, CT:29%, and TT:71% in the AMS group, but CC:4%, CT:12%, and TT:84% in the control group (p=0.011). We classified AMS severity as severe (4 patients admitted to the intensive care unit), moderate (2 patients hospitalized), and mild (4 patients managed at home). Two patients with severe AMS who developed both pulmonary and cerebral edema had an Aymara NFKB1 allele frequency of C: 1.0 and T: 0.0, a 100% CC genotype. Our findings suggest that the presence of the Aymara evolutionary selected NFKB1 haplotype protects from developing AMS, whereas its absence (CC genotype) increases the likelihood of development of severe AMS. The CT genotype of NOS2 variant may also provide some protective effect. Larger cohorts and functional assays are needed to validate these associations and to further explore the molecular mechanisms by which the NFKB1 and NOS2 variants contribute to protection against AMS.
Do Andean Aymara High‐Altitude–Enriched Genetic Variants Protect Europeans Against Acute Mountain Sickness?
(Wiley, 2026) Josef T. Prchal; M. Burtscher; Soo Jin Kim; Maria Wille; Ricardo Amaru; Jihyun Song
The authors declare no conflicts of interest. Data sharing not applicable to this article as no datasets were generated or analyzed during the current study.
Do Andean Aymaras' Evolutionary Selected Genes to High Altitude Hypoxia Also Influence Hemoglobin Concentration of Europeans and Their Acute Hypoxia Responses?
(Elsevier BV, 2022) Divya Sundar; Grace Min; Martin Burtscher; Ricardo Amaru; Maria Wille; Soo Jin Kim; Josef T. Prchal; Jihyun Song
The major regulation of hemoglobin levels (Hb) is hypoxia regulated by hypoxia inducible factors (HIFs). Some mutations of hypoxia sensing pathway increase HIFs and cause erythrocytosis (PMID: 23733342). Some high-altitude dwellers developed beneficial genomic evolution, facilitating their existence in high altitude hypoxia. Tibetans have been exposed to longer evolutionary selection than Andeans for approximately 44,000 and 14,000 years, respectively (PMID: 28448578, 25342802). This evolutionary pressure accounted for unique Tibetan haplotypes; it decreased HIFs activity and lowered Hb (PMID: 25129147). In contrast, Andean natives, Quechuas and Aymaras underwent different evolutionary adaptations to environmental hypoxia developinghigh Hb. We previously studied Aymaras at high-altitude and identified their evolutionary selected genes. The 5 most selected genes - BRINP3, NOS2, TBX5,SH2B1, and PYGM have some roles in cardiopulmonary development, but their functional consequences are unknown. None of these 5 highly selected Aymara genes are correlated with their Hb levels (PMID: 29100088). The single nucleotide polymorphisms (SNPs) of these genes also exist in Europeans, although in much lower frequency (Table). In contrast, NFKB1 rs230511 (allele frequency: 88% of Aymaras) underwent lower selection, but was still significant and correlated with the elevated hemoglobin in Aymaras (Song, ASH2018). It is also present in Europeans but at lower gene frequency (38%). NFKB1 is an inhibitor of NF-kB. Our previous analysis of differential exon usage of Aymara transcriptome found two previously unreported alternative splice transcripts of NFKB1 with exons 4 or 5 skipped transcripts. These transcripts correlated with Aymara enriched NFKB1 rs230511 and resulted in non-functional truncated-NFKB1 protein. Decreased NFKB1 results in increased NF-kB levels leading to NF-kB driven increased inflammation as well as increased HIFs activity (PMID: 26513405). Here, we interrogated associations among 6 Aymara hypoxia selected SNPs with physiological changes akinwith being rapidly exposed to hypobaric hypoxia (equivalent to 4500m) (Table). We isolated DNA from plasma 79 young and fit Austrian volunteers before and after exposure to hypoxia. Mean age was 26 ± 5.4 years (female = 34, male = 40 ). Their physiological responses to acute hypoxia were monitored at specific time intervals (0hr, 3hr, 6hr). These intervals included heart rate, systolic and diastolic blood pressures, oxygen saturation SpO2 and SaO2, PaCO2, blood pH, lactate and parameters of acute mountain sickness by Lake Louis score(PMID: 29583031). Their baseline Hb levels were also measured. These parameters were correlated with their 6 Aymara-enriched SNP. The Hb was only significantly higher in females with Aymara selected NFKB1 rs230511 by T test (p= 0.0163) and by Bartlett's test at p=0.017. Other SNPs have reached statistical significance in correlation with physiological parameters corresponding to acute hypoxic exposure. NOS2 rs34913975 correlated negatively with SpO2 (p= 0.0451), systolic blood pressure (p=0.0307) and diastolic blood pressure (p=0.0388), while SH2B1 rs 12448902 negatively correlated with SpO2 in heterozygotes (p=0.0068, ). The PYGM rs487105 correlated with systolic blood pressure (p=0.0095), and heart rate p=0.0442. However, some of these associations revealed trends for correlation.Since several Aymara-enriched SNPs had low allele frequency in Europeans, some correlations may not have reached enough statistical significance. A larger cohort may be needed for evaluation. In contrast, NFKB1 rs230511 correlated in females with higher Hb, but also with several other physiological responses to acute hypoxia in this cohort. It correlated positively with SpO2, systolic blood pressure (p=0.0041) and diastolic blood pressure (p=0.0114) while negatively with PaCO2 (p=0.0487) and Lake Louis score(p=0.0184). We conclude that the evolutionary-selected genes to chronic environmental hypoxia in Aymaras appear to also have function in Europeans. NFKB1 rs230511 has a significant association with higher Hb in the European females and is beneficial in some physiological responses to acute hypoxia. DS and GM contributed equally in this abstract. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal
Erythroid and Cardiovascular High Altitude-Selected Haplotypes in Andean Aymaras and Tibetans
(Elsevier BV, 2017) Ricardo Amaru; Jihyun Song; N. Scott Reading; Victor R. Gordeuk; Teddy Quispe; Lorna G. Moore; Rasmus Nielsen; Josef T. Prchal
Abstract Humans migrating out of Africa encountered new conditions, including living at high altitude. Tibetans and Andean Aymaras have inhabited regions of 4,000 meters or more for ~44,000 and 14,000 years respectively (Hu et al, PLoS Genet 2017, Rademaker et al, Science 2014). There is a distinct difference in erythroid phenotypes: Aymaras are polycythemic at high altitude, while most Tibetans are not. Mutations providing an advantage in highlanders will improve fitness under hypoxic conditions,including modulation of erythropoiesis through the hypoxia-inducible factor (HIF) pathway. There are few shared, naturally-selected gene regions in Aymaras and Tibetans and these have different phenotypic associations (Bigham et al, Am J Hum Biol 2013). Aymara high-altitude selected haplotypes have not been published. Tibetan EPAS 1 (encoding HIF2a protein) haplotypes in part originated from ancient Denisovans and entered the Tibetan genome through introgression (Huerta-Sanchez et al, Nature 2014). Tibetan variant prolyl hydroxylase 2 (PHD2), a negative regulator of HIFs encoded by EGLN1 gene, encodes in cis both PHD2D4E and PHD2C127S which together have increased activity in hypoxia (Lorenzo et al, Nature Genetics 2014) and, together with a Tibetan EPAS 1 haplotype, protects from high altitude polycythemia (Tashi et al, JMM 2017). We and others previously identified other Tibetans haplotypes that are not unique but are enriched in Tibetans, including a “Tibetan” haplotype of PKLR encoding liver- and red cell-specific pyruvate kinase (PK) (Simonson et al, Science 2010, and Yi et al, Science 2010). We studied Tibetan-enriched haplotypes of EGLN1, EPAS1 and PKLR in 72 Bolivian Andean Aymaras, all residing at 4,000 m, and compared them with 347 Tibetans living at altitudes of 200 m and 4,300 m (Table). We genotyped PHD2D4E and PHD2C127S variants of EGLN1 and 10 Tibetan specific single nucleotide polymorphisms (SNPs) of EPAS1, 5 Denisovan and 5 non-Denisovan, each under different linkage disequilibrium (Hu et all, PLoS Genet 2017), 7 Tibetan enriched PKLR SNPs, and searched for Aymara selected variants by whole genome sequencing. The prevalence of the Tibetan-selected EGLN1 and EPAS1 haplotypes increased with increasing altitude of residence in Tibetans, suggesting a continuous evolutionary advantage (Tashi et al, JMM 2017). Aymaras did not have the PHD2D4E haplotype, and PHD2C127S was found at lower prevalence in heterozygote form. Aymaras shared two of five non-Denisovan EPAS1 SNPs selected in Tibetans; one, rs130005507 G allele, had a similar prevalence to Tibetans, but another, rs142764723 C allele, had a lower prevalence. We report that >90% of Tibetans and ~50% of Aymaras, but only ~10% of Europeans, have the “Tibetan ” PKLR haplotype. Aymara females with homozygous PKLR haplotypes have lower hemoglobins than heterozygotes (p=0.022). Further, the PKLR transcript in reticulocytes decreases with increasing altitude and this progressive decrease is even more pronounced in the “Tibetan” haplotype. We found Aymaras' selected haplotypes encoding BRINP3, NOS2, TBX5 ; these genes are associated with cardiovascular development and function but not hypoxia sensing. They are not enriched in Tibetans. We conclude that Aymara highlanders do not have the Tibetan PHD2D4E mutation or Denisovan-like EPAS1 variants. Furthermore, they share only two of five Tibetan non- Denisovan EPAS1 variants. The absence of these variants in Aymaras supports that Tibetan and Aymara high altitude inhabitants do not have the same ancestry, that they developed different evolutionary adaptations (Bigham et al, Am J Hum Biol 2013), and that Tibetans' EGLN1 and EPAS1 mutations are unique to that part of the world. We hypothesize that decreased PK enzyme activity would be expected to increase 2,3-diphosphoglycerate (2,3-DPG) (as is shown in people with PK enzyme deficiency) and thus be beneficial to high altitude adaptation by progressively augmenting tissue oxygen delivery with increasing altitude. Based on its association with lower hemoglobin in Aymara females, the selected “Tibetan” PKLR haplotype, present in about half of Aymaras, may contribute to their hypoxic adaptation. Additional evaluation of evolutionary selected genes including PKLR, BRINP3, NOS 2, and TBX5 and their functional consequences are in progress with Aymaras living at El Alto (4,150 m), Cochabamba (2,500 m) and Santa Cruz, (416m), Bolivia. Download : Download high-res image (320KB) Download : Download full-size image Disclosures No relevant conflicts of interest to declare.
High altitude: A forgotten cause of pulmonary oedema
(Medknow, 2025) Jihyun Song; Ricardo Amaru; Josef T. Prchal
Natural Selection on Genes Related to Cardiovascular Health in High-Altitude Adapted Andeans
(Elsevier BV, 2017) Jacob E. Crawford; Ricardo Amaru; Jihyun Song; Colleen G. Julian; Fernando Racimo; Jade Yu Cheng; Xiuqing Guo; Jie Yao; Bharath Ambale‐Venkatesh; João A.C. Lima
Novel Form of Alternative Splicing of NFKB1. Its Role in Polycythemia and Adaptation to High Altitude in Andean Aymara
(Elsevier BV, 2018) Jihyun Song; Seonggyun Han; Ricardo Amaru; Teddy Quispe; Dongwook Kim; Jacob E. Crawford; Josef Stehlik; Rasmus Nielsen; Younghee Lee; Josef T. Prchal
Abstract Evolutionary adaptations to high altitude in Tibetans, Ethiopians, and Andean populations of South America have shown that Tibetans and Ethiopians have normal hemoglobin %, while most of Aymara and Quechua of the Andean highlands are polycythemic. Whole genome sequencing (WGS) in Quechua identified enriched SENP1 and ANP32D genes correlating with polycythemia (Zhou et al, Am J Hum Genet. 2013 Sep 5; 93(3): 452-462) but these genes were neither enriched nor segregated with polycythemia in Aymara. Instead, we identified that genes enriched in Aymara are related to regulation of cardiovascular development in high-altitude adapted Andeans, BRINP3, NOS2, and TBX5 (Crawford et al, Am J Hum Genet. 2017 Nov 2;101(5):752-767). To further search for Aymara propensity to polycythemia, we analyzed transcriptomes from Aymara and Europeans living in La Paz, Bolivia (3,639-4,150m) from limited amount of peripheral blood reticulocytes, platelets and granulocytes, but only granulocyte RNA was adequate for unbiased whole transcriptome analyses. In Aymaras, 2,585 genes were upregulated and 365 genes were downregulated (Adjp<0.05, fold difference <-2.0, and >2.0). Many of these modulated genes are involved in inflammatory pathways including B-cell activation (FDR=0.005) and NF-κB signaling pathway (FDR=0.011). We then analyzed differential exon usage in the transcriptome and identified 2,475 genes with alternative splicing events, comprising 1,568 exon skipping, 485 intron retention, 175 alternative 3' splice sites, 144 alternative 5' splice sites, and 902 mutually exclusive exons. These alternative spliced genes were also overrepresented in inflammatory pathways (TNF receptor, IL-1 and IL-23 mediated signaling, and NF-κB signaling). Notably we detected the previously unreported NFKB1 alternate transcripts skipping exon 4 or 5, which lead to the out-of-framed NFKB1 mRNA, generating the truncated nonfunctional NF-κB protein (Figure). Inflammation is a potent suppressor of erythropoiesis and the NF-κB is transcriptional regulator of plethora of inflammatory genes. Further, NF-κB also interacts with erythropoiesis-regulators, hypoxia-inducible factors (HIFs). By the integrative analysis of the Aymara transcriptome and WGS, we identified 46 NFKB1 splicing quantitative trait loci (sQTLs). Among these 46 sQTLs, five single nucleotide polymorphisms (SNP) were in high linkage disequilibrium, and two (rs230511 and rs230504) were more enriched in Aymara (allele frequency: 0.878) (Figure) and within a genomic region where Andeans are genetically differentiated from lowland Native Americans (peak FST = 0.37, peak PBSn1 = 0.31). These sQTLs rs230511 and rs230504 were corelated with two functionally important exon skipping (exon 4 and 5) in NFKB1 as described above. Furthermore, these two SNPs were correlated with higher hemoglobin levels and lower leukocytes; the wild-type NFKB1 transcript inversely correlated with hemoglobin%. We report Aymara have differentially expressed and alternatively spliced transcripts of genes modulating inflammation, particularly NFKB1. This Aymara enriched NFKB1 haplotype variant stands out as a major cause of Aymara adaptation to high altitude, as this truncated nonfunctional NF-κB variant peptide correlates with higher hemoglobin, lower leukocytes and suppresses inflammation. These data indicate that NFKB1 SNPs enriched in Aymara are associated with alternative spliced NFKB1 transcripts which contribute to polycythemia in Aymara. Further evaluation of NF-κB and HIFs' transcriptional activity and their correlation with inflammatory makers, hepcidin and erythroferrone in Aymara and Europeans living at the same high altitude is under way. JS and SH contributed equally to this work. YL and JTP act as equivalent co-senior authors. Figure. Figure. Disclosures No relevant conflicts of interest to declare.
Tibetan Enriched PKLR Variant Is Beneficial to High Altitude Adaption By Improving Oxygen Delivery
(Elsevier BV, 2018) Jihyun Song; Virginia Abello; Ricardo Amaru; Adelina Sergueeva; Jainagul Isakova; Penelope A. Kosinski; Brigitte A. van Oirschot; Victor R. Gordeuk; Charles Kung; Richard van Wijk
Abstract Tibetans have been living at altitudes over 3500 m for ~20,000 years and have developed unique beneficial evolutionary genetic adaptions (PMID:28448578). Our previous study identified selected genetic haplotypes in two genes, EPAS1 (encoding hypoxia-inducible factor 2-alpha [HIF2-a], a transcription factor that mediates the hypoxic response), and EGLN1 (encoding prolyl hydroxylase 2 [PHD2], a principal negative regulator of HIF stability (PMID:25129147). The presence of these two haplotypes correlates with lower hemoglobin levels in Tibetans compared to other highlanders. However, the entire diverse complex of molecular mechanisms of high altitude adaptation is still largely unknown and our study showed that neither EPAS1 nor EGLN1 variants fully explain the mechanism of protection from polycythemia in Tibetans in high altitude (PMID:28233034). We found an enriched haplotype in the PKLR gene (encoding pyruvate kinase [PK] expressed only in liver and red blood cells). The PK enzyme is in the terminal portion of the glycolytic pathway, and its decreased activity leads to accumulation of proximal glycolytic intermediates, including 2,3-diphosphoglycerate (DPG) which shifts the hemoglobin dissociation curve to right (high p50) and increases oxygen release to tissues from a unit of hemoglobin. We hypothesized that Tibetan enriched PKLR variants might improve oxygen delivery to tissues and help explain the protection from polycythemia at high altitude. Genomic analyses revealed that this PKLR haplotype is enriched in Tibetans but is not unique to Tibetans. It has the highest frequency in Tibetans (89%), with a lower prevalence in Chinese and Mongolians (~77%), Kyrgyz (~60 %), Aymara (~44 %), and Colombians (~30 %) and a much lower frequency in Caucasians (11%), perhaps explaining the heterogeneity of responses to hypoxia within and among these populations. Our study of reticulocyte RNA showed that transcript levels of PKLR progressively decrease with increasing altitude in controls and even more in Tibetans with the Tibetan evolutionary selected PKLR haplotype. Tibetans with the PKLR haplotype (heterozygotes and homozygotes) have lower PKLR transcript levels than wild type Tibetans. Because of the paucity of wildtype PKLR haplotype in Tibetans and the challenges of acquiring Tibetan samples in high altitude in China, we collected samples from 125 m (Cheboksary, Chuvashia); 800 m (Bishkek, Kyrgyzstan) and 2640 m (Bogota, Colombia). PK activity, PKLR transcript levels, and ATP decreased at 2640 m compared to 800 m, while p50 increased at 2640 m. PKLR transcript levels correlated with PK activity and ATP and inversely correlated with p50. PK activities also correlated with PKLR transcript levels and ATP and inversely correlated with p50. At 2640 m, PK activity was lower and p50 levels were higher in those with the enriched PKLR haplotype. These results demonstrate that increasing altitude decreases PK activity, resulting in increasing p50 providing a molecular basis for the previously reported improvement of oxygen delivery at high altitude (PMID:17394415). To study the roles of HIFs in the regulation of PKLR gene expression, we also collected samples from Chuvash polycythemia (CP) homozygotes and Chuvash controls. CP homozygotes have a mutation in the VHL gene, a negative regulator of HIFs, that results in augmented HIF levels. CP homozygotes had lower PKLR mRNA in reticulocytes, PK activity, and PKR protein levels in red blood cells compared to controls, while their 2,3 DPG levels were higher. These data confirm that PKLR expression levels are negatively regulated by HIFs. Our findings demonstrate that individuals in high altitudes have lower PKLR transcript levels and PK activity, resulting in high 2,3DPG and p50 which shifts the hemoglobin dissociation curve to right. This decreases affinity of hemoglobin for oxygen, which improves tissue oxygen delivery and as such is another mechanism in Tibetans that protects from high altitude polycythemia. We also demonstrate that HIFs negatively regulate PKLR expression, leading to better oxygen release from hemoglobin at high altitude. Disclosures Kosinski: Agios: Employment, Equity Ownership. Kung:Agios: Employment, Equity Ownership. van Wijk:RR Mechatronics: Research Funding; Agios Pharmaceuticals: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.
“What We Know and What We Do Not Know about Evolutionary Genetic Adaptation to High Altitude Hypoxia in Andean Aymaras”
(Multidisciplinary Digital Publishing Institute, 2023) Ricardo Amaru; Jihyun Song; N. Scott Reading; Victor R. Gordeuk; Josef T. Prchal
Three well-studied populations living at high altitudes are Tibetans, Andeans (Aymaras and Quechuas), and Ethiopians. Unlike Tibetans and Ethiopians who have similar hemoglobin (Hb) levels as individuals living at sea level, Aymara Hb levels increase when living at higher altitudes. Our previous whole genome study of Aymara people revealed several selected genes that are involved in cardiovascular functions, but their relationship with Hb levels was not elucidated. Here, we studied the frequencies of known evolutionary-selected variants in Tibetan and Aymara populations and their correlation with high Hb levels in Aymara. We genotyped 177 Aymaras at three different altitudes: 400 m (Santa Cruz), 4000 m (La Paz), and 5000 m (Chorolque), and correlated the results with the elevation of residence. Some of the Tibetan-selected variants also exist in Aymaras, but at a lower prevalence. Two of 10 Tibetan selected variants of EPAS1 were found (rs13005507 and rs142764723) and these variants did not correlate with Hb levels. Allele frequencies of 5 Aymara selected SNPs (heterozygous and homozygous) at 4000 m (rs11578671_BRINP3, rs34913965_NOS2, rs12448902_SH2B1, rs10744822_TBX5, and rs487105_PYGM) were higher compared to Europeans. The allelic frequencies of rs11578671_BRINP3, rs34913965_NOS2, and rs10744822_SH2B1 were significantly higher for Aymaras living at 5000 m than those at 400 m elevation. Variant rs11578671, close to the BRINP3 coding region, correlated with Hb levels in females. Variant rs34913965 (NOS2) correlated with leukocyte counts. Variants rs12448902 (SH2B1) and rs34913965 (NOS2) associated with higher platelet levels. The correlation of these SNPs with blood cell counts demonstrates that the selected genetic variants in Aymara influence hematopoiesis and cardiovascular effects.