complexes. It will now be essential to elucidate
the downstream mechanism or mechanisms
that block the emergence of secondary pollen
tubes at the septum. Further components of
this polytubey block may include nitric oxide
( 11 ); secretion of cell wall components; and
ROS that mediate FER-controlled pollen tube
rupture ( 21 ), pollen hydration ( 31 ), and self-
incompatibility ( 32 ).
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ACKNOWLEDGMENTS
We thank D. Ye for providingfer-4andmyb97 myb101 myb120mutant
seeds; L. Smith for sharinganj,herk1,anj herk1, andfer anj herk1
mutant seeds; J. F. Harper for providingaca9mutant seeds; and C. Li
and Q. Duan for sharingfer+/−mutant seeds.Funding:L.-J.Q. was
funded by the National Natural Science Foundation of China (grant
nos. 31991202, 31830004, 31620103903, and 31621001), S.Z. was
supported by the Young Elite Scientists Sponsorship Program by the
China Association of Science and Technology (2019QNRC001), Z.G. was
supported by a NSFC Young Scientists Fund (31900161), A.Y.C. was
funded by the US Natural Science Foundation (IOS-1645854, MCB-
1715764, and MCB-0955910), J.D. was funded by the National Institute of
Health (R01GM109080), and T.D. was supported by the German
Research Foundation DFG (SFB924).Author contributions:S.Z. and
L.-J.Q. conceived the project, and L.-J.Q. and H.G. supervised the project.
S.Z., Li.Li, Z.W., Z.G., and T.L. performed molecular cloning and CRISPR-
Cas9–mediated mutant generation. S.Z., Li.Li, and Z.W. performed
phenotype observation and statistical analysis. Li.Li and Z.W. analyzed
the GUS activity with the help of Z.S., Lu.Li, and L.Z. S.Z., Z.G., and Y.S.
performed RNA-seq analysis. Z.G., Q.L., and J.W. performed protein
expression, protein purification, and all the protein-protein interaction
assays with the help of H.Z., Y.W., and Lu.La. A.B. and T.D. conducted
receptor reporter localization assays. S.Z., J.D., H.-M.W., A.Y.C., T.D., and
L.-J.Q. drafted the manuscript. All authors contributed to data analysis
and manuscript preparation.Competing interests:The authors declare
no competing interests.Data and materials availability:All data are
available in the main text or the supplementary materials.
SUPPLEMENTARY MATERIALS
science.org/doi/10.1126/science.abl4683
Materials and Methods
Figs. S1 to S12Tables S1 to S3
References ( 33 – 47 )
MDAR Reproducibility Checklist15 July 2021; accepted 30 November 2021
10.1126/science.abl4683REPORTS
◥MULTIPLE SCLEROSISLongitudinal analysis reveals high prevalence of
Epstein-Barr virus associated with multiple sclerosis
Kjetil Bjornevik^1 †, Marianna Cortese^1 †, Brian C. Healy2,3,4, Jens Kuhle^5 , Michael J. Mina6,7,8,
Yumei Leng^6 , Stephen J. Elledge^6 , David W. Niebuhr^9 , Ann I. Scher^9 ,
Kassandra L. Munger^1 ‡, Alberto Ascherio1,10,11*‡Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous
system of unknown etiology. We tested the hypothesis that MS is caused by Epstein-Barr
virus (EBV) in a cohort comprising more than 10 million young adults on active duty in the
US military, 955 of whom were diagnosed with MS during their period of service. Risk of
MS increased 32-fold after infection with EBV but was not increased after infection with other
viruses, including the similarly transmitted cytomegalovirus. Serum levels of neurofilament
light chain, a biomarker of neuroaxonal degeneration, increased only after EBV seroconversion.
These findings cannot be explained by any known risk factor for MS and suggest EBV as the
leading cause of MS.M
ultiple sclerosis (MS) is a chronic in-
flammatory demyelinating disease of
the central nervous system of unknown
etiology. The demyelination in the
brain and spinal cord is an immune-
mediated process ( 1 ) possibly triggered by a
viral infection ( 2 ). Among the putative causal
agents, the top candidate is Epstein-Barr virus
(EBV) ( 3 ). EBV is a human herpesvirus that
after infection persists in latent form in B lym-
phocytes throughout the life of the host ( 3 ).
A causal role of EBV is supported by the in-
creased MS risk after infectious mononucleo-
sis ( 4 ), elevated serum antibody titers against
EBV nuclear antigens (EBNAs) ( 5 ), and by the
presence of EBV in MS demyelinated lesions
reported in some ( 6 – 8 ), but not all ( 9 ), path-
ological studies. Evidence of causality, how-
ever, remains inconclusive.Causality implies that some individuals who
developed MS after EBV infection would not
have developed MS if they had not been in-
fected with EBV.Ruling out a randomized
trial, the gold standard to study this coun-
terfactual occurrence is an“experiment of
nature,”a longitudinal investigation of MS
incidence in a cohort of EBV-negative indi-
viduals, some of whom will be infected with
EBV during the follow-up and some who will
not. The ubiquitous nature of EBV, which in-
fects ~95% of adults, and the fact that MS is a
relatively rare disease, has until now impeded
such an investigation. Over the course of a
20-year collaboration with the US military,
we have identified cases of MS in a cohort
composed of active-duty US military per-
sonnel between 1993 and 2013, a racially
diverse population of >10 million individuals.296 21 JANUARY 2022•VOL 375 ISSUE 6578 science.orgSCIENCE
(^1) Department of Nutrition, Harvard T. H. Chan School of Public Health, Boston, MA, USA. (^2) Partners Multiple Sclerosis Center,
Brigham and Women’s Hospital, Boston, MA, USA.^3 Department of Neurology, Harvard Medical School, Boston, MA, USA.
(^4) Biostatistics Center, Massachusetts General Hospital, Boston, MA, USA. (^5) Neurologic Clinic and Policlinic, MS Center and
Research Center for Clinical Neuroimmunology and Neuroscience Basel (RC2NB), University Hospital Basel, University of Basel,
Basel, Switzerland.^6 Division of Genetics, Brigham and Women’s Hospital, Howard Hughes Medical Institute, Department of
Genetics, and Program in Virology, Harvard Medical School, Boston, MA, USA.^7 Center for Communicable Disease Dynamics,
Department of Epidemiology, and Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public
Health, Boston, MA, USA.^8 Department of Pathology, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA,
USA.^9 Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, Bethesda,
MD, USA.^10 Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA, USA.^11 Channing Laboratory,
Department of Medicine, Brigham and Women’s Hospital, and Harvard Medical School, Boston, MA, USA.
*Corresponding author. Email: [email protected]
†These authors contributed equally to this work.
‡These authors contributed equally to this work.
RESEARCH