Tibetan PHD2, an allele with loss-of-function properties

Area of Science:

• Human adaptation to extreme environments
• Molecular genetics and physiology
• High-altitude biology

Background:

• Tibetans exhibit unique physiological adaptations to high-altitude chronic hypoxia.
• Genetic studies pinpoint natural selection in Hypoxia Inducible Factor (HIF) pathway genes, specifically PHD2 and HIF2A.
• The functional impact of Tibetan PHD2 variants on high-altitude adaptation remains unclear.

Purpose of the Study:

• To determine if Tibetan PHD2 is a gain-of-function or loss-of-function allele.
• To investigate the role of Tibetan PHD2 in high-altitude physiological adaptations.
• To elucidate the interaction between PHD2, p23, and the HIF pathway in adaptation.

Main Methods:

• In vitro analysis of Tibetan PHD2 interaction with p23 cochaperone.
• Generation and physiological assessment of mice with the Tibetan Phd2 allele.
• Phenotypic comparison of mice with Tibetan Phd2 allele, p23 mutation, and Hif2a haploinsufficiency.

Main Results:

• Tibetan PHD2 variants, including D4E and C127S, impair interaction with p23 in vitro.
• Mice with the Tibetan Phd2 allele show an augmented hypoxic ventilatory response, supporting loss-of-function.
• Tibetan Phd2 allele does not affect hypoxia-induced pulmonary hypertension or hemoglobin levels in mice.

Conclusions:

• Tibetan PHD2 functions as a loss-of-function allele, contributing to enhanced hypoxic ventilatory response.
• The Tibetan Phd2 allele's effect on pulmonary hypertension differs from Hif2a haploinsufficiency.
• Tibetans may utilize coordinated genetic modifications in the HIF pathway for successful high-altitude adaptation.