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.

Background: Bolivian Andean Aymara highlanders, living at 4,000 m for 14,000 years, have evolved genetic adaptations to hypoxia. These include EGLN1 encoding prolyl hydroxylase 2 (PHD2), a regulator of transferrin transcription. Transferrin level increases in hypoxia and iron deficiency. Contrasting reports indicate that elevated transferrin is associated with experimentally induced thrombosis in mice undergoing short-stay at high altitude, but with decreased thrombosis in a congenital disorder of hypoxia-sensing. Methods: A retrospective study was conducted in people living at high altitude (3,650 - 4,150 m). We analyzed serum transferrin concentration and thrombosis history in Aymara patients with high-altitude erythrocytosis (n = 149, median age 55 years, female gender 30%, iron deficiency 23%) or high-altitude anemia (n = 137, median age 43 years, female gender 86%, iron deficiency 57%). Results: The median transferrin concentration was 339 mg/dL in erythrocytosis patients versus 310 mg/dL in anemia patients (P = 0.037); it was 367 mg/dL in iron deficient versus 312 mg/dL in iron replete patients (P < 0.001). Thrombosis history was present in 13% of erythrocytosis and 8% of anemia patients (P = 0.25) and was present in 16% of iron deficient and 7% of iron replete patients (P = 0.017). After adjustment for erythrocytosis and iron deficiency in multivariate regression analysis, the mean (95% confidence interval) transferrin concentration was 277 (237 - 316) mg/dL in 30 patients with thrombosis history versus 324 (306 - 341) mg/dL in 256 patients without thrombosis history (P = 0.018). Similar trends occurred for the subgroups of arterial thrombosis history (P = 0.044) and venous thrombosis history (P = 0.22). Conclusions: In individuals with extreme environmental hypoxia, we found no evidence that increased transferrin is associated with increased thrombosis history. Rather, we observed a trend to decreased thrombosis history with increased transferrin levels.

Introducción: La leucemia eritroide aguda (LEA) es un subtipo raro y agresivo de leucemia mieloide aguda, asociada a mutaciones bialélicas del gen TP53. La edad media de diagnóstico es 67 años conllevando una proporción hombre:mujer de 2,4:1. La hipoxia y los factores inducibles por hipoxia (HIF) parecen desempeñar un rol en el desarrollo de LEA mediante mecanismos que involucran la diferenciación eritroide, producción de hemoglobina, regulación de eritropoyesis y modificación del microambiente de la médula ósea. Por lo que, para discernir sobre la influencia de la hipoxia en este subtipo de leucemia, es de interés analizar su prevalencia y características en poblaciones residentes a gran altitud. Material y Métodos. Estudio retrospectivo que consideró casos de LMA (n=211) diagnosticados en Bolivia durante el periodo de mayo de 2019 a octubre de 2024, se identificó casos del subtipo LEA (n=15) y se recopiló datos demográficos, hematológicos, morfológicos e inmunofenotípicos. El análisis estadístico contempló categorizar los casos de LMA y subsecuentemente de LEA según la altitud de presentación: 4000m, 2000m y 400m. Resultados. Los casos de LEA en Bolivia correspondieron al 7,5 % entre todos los casos de LMA, la edad media de presentación fue 53 años con predominio en varones (1,5:1). Distribuidos por altitudes, los casos de LEA a 4000 m (n=10) representaron el 14,1 %, significativamente mayor (p=0,01) comparado con el 4,5 % observado en los casos a 2000 m (n=3) y 2,7 % en los casos a 400 m (n=2). Los índices hematológicos de LEA reflejaron hemoglobina media de 7,3 g/dl, leucocitos 10266/ul y plaquetas 82267/ul, sin diferencias epresentativas entre las diferentes altitudes. Los rasgos de médula ósea reflejaron >80% de precursores eritroides prominentes con núcleos grandes e irregulares, cromatina dispersa, 1 a 3 nucléolos alargados, citoplasma profundamente basófilo e intensa actividad mitótica. Las características inmunofenotípicas mostraron clonalidad eritroide 90 % (CD34, CD71, CD105, CD36, CD235) y clonalidad mieloide 1,4 % (CD117, CD34). Conclusiones. El porcentaje de LEA (14,1 %), respecto del total de casos de LMA, está aumentada en la altitud (4000 m). Tal aumento podría deberse al incremento de HIF y Eritropoyetina en ambientes de hipoxia hipobárica.