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ACKNOWLEDGMENTS
We thank the Amish community and the Amish Research Clinic
staff. WGS for the TOPMed program was supported by the NHLB).
WGS for“NHLBI TOPMed: Genetics of Cardiometabolic Health
in the Amish”(phs000956) was performed at the Broad Institute
of MIT and Harvard. Core support including centralized genomic
read mapping and genotype calling, along with variant quality
metrics and filtering were provided by the TOPMed Informatics
Research Center (3R01HL-117626-02S1; contract no.
HHSN268201800002I). Core support including phenotype
harmonization, data management, sample-identity QC, and
general program coordination were provided by the TOPMed
Data Coordinating Center (R01HL-120393; U01HL-120393;
contract HHSN268201800001I). MMAP ( 52 ) was used for
single-variant genetic analyses.Funding:This work was
supported in part by NIH grants U01HL137181, U01HL072515,
R01AG18728, R01HL121007, HHSN268201500014C, 3R01HL-117626-
02S1, 3R01HL-120393-02S1, and P30DK072488 and by American
Heart Association grant 17GRNT33661168 and Regeneron
Pharmaceuticals, Inc.Author contributions:Conceived,
designed and supervised the work: A.R.S., A.N.E., M.E.M. Data
collection: A.D.H., A.R., A.R.S., B.S., C.H., Ch.H., D.W., E.P.,
G.D.G., G.T., J.R.O., L.A.L., L.L., L.M., M.E.M., N.L., Q.F., S.A.H.,
W.L., Y.M., Y.T. Data analysis: A.E.L., B.S., B.Y., C.H., C.V.H., D.W.,
G.D.G., G.G., G.T., J.A.P., J.R.O., K.A.R., L.A.L., L.L., L.M., M.E.M.,
M.F., M.H., N.L., N.V., S.A.H., T.D., Y.T. Results interpretation:
A.B., A.D.H., A.N.E., A.R.S., B.D.M., B.S., C.S., C.V.H., E.S., G.D.G.,
J.R.O., M.E.M., M.H., N.L., S.I.T., T.J.D. Manuscript preparation:
A.R.S., G.D.G., M.E.M..Competing interests:A.E., A.R., A.R.S.,
B.S., B.Y., C.H., C.V.H., D.W., E.P., G.D.G., G.G., G.T., L.A.L., L.L.,
L.M., M.C., M.H., N.L., Q.F., S.A.H., T.J.D., W.L., Y.M., and Y.T.
are current or former employees of Regeneron Pharmaceuticals,
Inc. A.R.S., C.V.H., G.D.G., M.E.M., and M.H. are inventors on
US Patent Number 10,738,284“B4GALT1 Variants And Uses Thereof”
and international patent applications filed in Europe, Canada,
New Zealand, Singapore, Israel, India, and Japan. A.R.S. and
G.D.G. are inventors on a separate patent application related to
this work filed by Regeneron Pharmaceuticals, Inc., US
Application No. 17/190,650, on 3 March 2021, which is pending.
M.E.M. and B.D.M. receive sponsored research support from
RegeneronPharmaceuticals,Inc.A.R.S.isapart-timefaculty
member at the University of Maryland School of Medicine,
in addition to his employment at Regeneron.Data availability:
Amish WGS, phenotypes, and covariates are available through
dbGaP (phs000956). WES, chip genotypes, imputed data, and
glycoprotein data are available to academic investigators through
a data use agreement with UMB. DiscovEHR data are available
through a data transfer agreement with Regeneron. Regeneron
materials (mice and data) described in this manuscript may
be available to qualified, academic, noncommercial researchers
upon request through the Regeneron portal (https://regeneron.
envisionpharma.com/vt_regeneron/). Please send any questions
about materials sharing to preclinical.collaborations@regeneron.
com. UKBB data are available by application to UK Biobank as
described at https://www.ukbiobank.ac.uk/enable-your-research/
apply-for-access.SUPPLEMENTARY MATERIALS
science.org/doi/10.1126/science.abe0348
Materials and Methods
Figs. S1 to S16
Tables S1 to S11
References ( 53 – 75 )
MDAR Reproducibility ChecklistRegeneron Genetics Center Collaborators
Goncalo Abecasis, Aris Baras, Michael Cantor, Giovanni Coppola,
Andrew Deubler, Aris Economides, Katia Karalis, Luca A. Lotta,
John D. Overton, Jeffrey G. Reid, Alan R. Shuldiner, Nilanjana
Banerjee, Dadong Li, Deepika Sharma, Xiaodong Bai, Suganthi
Balasubramanian, Andrew Blumenfeld, Gisu Eom, Lukas Habegger,
Alicia Hawes, Shareef Khalid, Evan K. Maxwell, William Salerno,
Jeffrey C. Staples, Josh Backman, Mathew Barber, Christian Benner,
Shan Chen, Amy Damask, Lee Dobbyn, Manuel A. R. Ferreira,
Arkopravo Ghosh, Lauren Gurski, Eric Jorgenson, Bindu Kalesan,
Jack A. Kosmicki, Hyun Min Kang, Alexander Li, Nan Lin, Daren Liu,
Adam E. Locke, Jonathan Marchini, Anthony Marcketta, Joelle Mbatchou,
Arden Moscati, Colm O’Dushlaine, Charles Paulding, Jonathan Ross,
Eli Stahl, Dylan Sun, Cristopher Van Hout, Kyoko Watanabe,
Bin Ye, Andrey Ziyatdinov, Marcus B. Jones, Michelle G. LeBlanc,
Jason A. Mighty, Lyndon J. Mitnaul, Ariane Ayer, Kavita Praveen,
Regeneron Genetics Center, LLC, Tarrytown, NY 10591, USA.27 July 2020; resubmitted 25 February 2021
Accepted 19 October 2021
10.1126/science.abe0348METABOLISMFumarate is a terminal electron acceptor in the
mammalian electron transport chain
Jessica B. Spinelli1,2*, Paul C. Rosen1,2,3, Hans-Georg Sprenger1,2, Anna M. Puszynska1,2,
Jessica L. Mann1,2,3, Julian M. Roessler1,2,3, Andrew L. Cangelosi1,2,3, Antonia Henne^1 ,
Kendall J. Condon1,2,3, Tong Zhang1,2,3, Tenzin Kunchok^1 , Caroline A. Lewis^1 ,
Navdeep S. Chandel^4 , David M. Sabatini^3For electrons to continuously enter and flow through the mitochondrial electron transport chain
(ETC), they must ultimately land on a terminal electron acceptor (TEA), which is known to be
oxygen in mammals. Paradoxically, we find that complex I and dihydroorotate dehydrogenase
(DHODH) can still deposit electrons into the ETC when oxygen reduction is impeded. Cells lacking
oxygen reduction accumulate ubiquinol, driving the succinate dehydrogenase (SDH) complex in
reverse to enable electron deposition onto fumarate. Upon inhibition of oxygen reduction,
fumarate reduction sustains DHODH and complex I activities. Mouse tissues display varying
capacities to use fumarate as a TEA, most of which net reverse the SDH complex under hypoxia.
Thus, we delineate a circuit of electron flow in the mammalian ETC that maintains mitochondrial
functions under oxygen limitation.T
he flow of electrons through the mito-
chondrial electron transport chain (ETC)
supports a diverse set of cellular pro-
cesses, such as the synthesis of central
metabolites and the regulation of sig-
naling and cell death pathways ( 1 – 7 ). Electrons
enter the ETC through the activities of en-
zymes such as dihydroorotate dehydrogenase
(DHODH) and complex I, move between com-
plexes via the electron carrier ubiquinol (UQH 2 ),
and exit by reducing a terminal electron ac-ceptor (TEA). The canonical view is that in
mammalian cells, oxygen (O 2 ) serves as the
sole TEA and its reduction is necessary for the
reoxidation of UQH 2 into ubiquinone (UQ)
and thus the continuous input of electrons
into the ETC. However, under a variety of
physiological states, mammalian cells can
exist in hypoxic niches ( 8 – 16 ) while maintain-
ing functions that require the flow of electrons
into the ETC, including de novo pyrimidine
biosynthesis and oxidation of reduced nicotin-
amide adenine dinucleotide (NADH) ( 17 – 22 ).
Thus, we sought to clarify the extent to which
mitochondrial functions that necessitate elec-
tron input into the ETC also require the use of
O 2 as a TEA.Results
In mammalian cells, the flow of electrons into
the ETC does not require O 2 reduction
To ask how limitations in O 2 reduction affect
mitochondrial functions that depend on theSCIENCEscience.org 3 DECEMBER 2021•VOL 374 ISSUE 6572 1227
(^1) Whitehead Institute for Biomedical Research, Cambridge,
MA 02142, USA.^2 Howard Hughes Medical Institute,
Department of Biology, Massachusetts Institute of
Technology, Cambridge, MA 02139, USA.^3 Department of
Biology, Massachusetts Institute of Technology, Cambridge,
MA 02139, USA.^4 Feinberg School of Medicine, Northwestern
University, Chicago, IL 60611, USA.
*Corresponding author. Email: [email protected]
†David M. Sabatini is no longer affiliated with the Whitehead
Institute or the Howard Hughes Medical Institute. To ensure
execution of the duties of corresponding author, Jessica B. Spinelli
has taken on this role.
RESEARCH | RESEARCH ARTICLES