Former UCSD prof who resigned amid investigation into China ties retracts paper for ‘inadvertently misidentified’ images

Kang Zhang

Kang Zhang, a formerly high-profile geneticist at the University of California, San Diego, who resigned his post last July amidst an investigation into undisclosed ties to China, has retracted a paper because some of its images were taken from other researchers’ work.

The paper, “Impaired lipid metabolism by age-dependent DNA methylation alterations accelerates aging,” was submitted to the Proceedings of the National Academy of Sciences (PNAS) last fall, months after Zhang’s resignation. One of Zhang’s fellow corresponding authors, Jian-Kang Zhu, used the journal’s “Contributed Submissions” process, in which “An NAS member may contribute up to two of her or his own manuscripts for publication in PNAS each year.”

PNAS published the paper on February 6 of this year. But on February 18, authors of a different paper, in Aging Cell, sent the editors of PNAS a letter, writing:

Key data in this paper were taken without attribution from our earlier paper in Aging Cell and mislabeled with respect to the animals involved. Our Aging Cell paper, “The lipid elongation enzyme ELOVL2 is a molecular regulator of aging in the retina,” was available as a preprint on bioRxiv on October 8, 2019. The paper was submitted on October 23, 2019, accepted for publication on December 11, and published online on January 13, 2020. We attach the bioRxiv version, which remains publicly available Kang Zhang is a co-author on both papers and the only shared author between them. He agreed to the original bioRxiv manuscript and to its publication. Dr. Zhang was aware of the content and of the key dates mentioned above.

The paper was retracted just over a month later. The notice reads:

The authors wish to note the following: “It came to our attention after publication that the fundus images in Fig. 3E and SI Appendix, Fig. S4C of our PNAS article were a duplication of the photos in a recent Aging Cell article (1). These photographs were generated by Dr. Daniel Chen and Dr. Dorota Skowronska-Krawczyk in the course of conducting research exploring the effects of Elovl2 deficiency in the mouse eye at Dr. Kang Zhang’s laboratory at University of California San Diego. In the same time period, the authors of the PNAS paper were working at the same laboratory exploring the effects of the Elovl2 loss in the entire mouse body. While the two groups of researchers were working concurrently at Dr. Zhang’s University of California San Diego laboratory, the fundus photographs were inadvertently misidentified and mixed in with materials developed for the Elovl2 mouse strain in the PNAS paper, during the process of data organization and presentation. The similarities in genetic properties between the Elovl2 mouse strains contributed to the confusion and subsequent mix-up.

“We apologize to the scientific community for this inadvertent error. Despite the fact that this is an honest mistake and the inclusion of the erroneously misidentified photos did not affect the conclusions of the PNAS article nor the validity of the remaining data and findings in the paper, including all of the data generated from the laboratories of Drs. Qi Zhou, Wei Li, and Jian-Kang Zhu, who are unaccountable for this inadvertent error, we believe that a retraction is appropriate to prevent confusion among the scientific community. The affiliation of Dr. Xin Li needs to be corrected as University of California, San Diego, rather than Whitehead Institute for Biomedical Research.”

Zhang, who had a lab named after him at UCSD, has not responded to a request for comment from Retraction Watch. Last April, inewsource, which reported Zhang’s resignation in July, reported that

several of Zhang’s studies were riddled with violations of basic human research standards. A U.S. Food and Drug Administration warning in 2017 and a UCSD audit that followed reveal a pattern that put patients in harm’s way for years.

Dorota Skowronska-Krawczyk, the last author of the Aging Cell paper, who was one of the researchers who generated the mixed-up images, told Retraction Watch:

We were deeply disappointed by the turn of events but we are satisfied with the PNAS actions. We hope this example will encourage other researchers to react in similar situations.

Like Retraction Watch? You can make a tax-deductible contribution to support our work, follow us on Twitter, like us on Facebook, add us to your RSS reader, or subscribe to our daily digest. If you find a retraction that’s not in our database, you can let us know here. For comments or feedback, email us at

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.