Chun So, Ph.D

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Scientists&Research

Chun So, Ph.D.

Assistant Investigator, NIBS, Beijing

Email: sochun@cjcasa.com

Research Description

Focusing on female reproductive health is a key way of dealing with population aging. Abnormal egg and embryo development are the leading causes of female infertility, miscarriage and genetic disorders such as Down Syndrome. Previously we have made several pioneering discoveries of the mechanisms underlying meiotic maturation of oocytes into eggs, such as the biophysical mechanism underlying spindle assembly in mammalian oocytes and the molecular mechanism underlying spindle instability and chromosome missegregation in human oocytes.

First, we discovered how mammalian oocytes utilize centrosomal proteins to assemble acentrosomal spindles (So and Seres et al. Science 2019). Mammalian oocytes express many centrosomal proteins despite the absence of centrosomes. During female meiosis, some of these proteins undergo a biophysical phenomenon known as liquid-liquid phase separation to form a previously undescribed domain, which we termed the liquid-like meiotic spindle domain (LISD). The LISD sequesters and mobilizes centrosomal proteins with microtubule regulatory functions in proximity to spindle microtubules, thus promoting spindle assembly in the absence of centrosomes.

Second, we uncovered how are spindle poles organized and why are they unstable in human oocytes (So et al. Science 2022). Human and other mammalian oocytes similarly utilize NUMA to recruit dynein to microtubule minus-ends for the focusing of acentrosomal spindle poles. However, unlike human oocytes, other mammalian oocytes do not assemble unstable spindles. Using a reverse genetic screen, we identified the minus-end-directed kinesin KIFC1 as a key determinant of meiotic spindle stability. While KIFC1 is readily expressed in most mammalian oocytes, it is deficient in human oocytes. By introducing exogenous KIFC1, we successfully increased the fidelity of spindle assembly and chromosome segregation in human oocytes. For the first time, we proposed a potential therapeutic method for reducing the risk of aneuploidy in human eggs.

With our expertise in cutting-edge light and electron microscopy and the support from the 13 core facilities at NIBS, we will continue adopting a cross-disciplinary approach to illuminate novel Ezpay(中国)ular, molecular and biophysical mechanisms underlying egg and embryo development across different mammalian models.. Our findings will provide novel insights into the causes and treatments of female infertility, and improve the existing assisted reproductive technologies.

Publications

(*Equal contribution; #Co-correspondence)

17. Wang, J., Li, W., Guo, J., Xu, X., Lin, G.#, Li, B.#, So C#. “Natural degradation of RNA polymerase II is essential for oocyte chromatin reorganization and maternal-to-zygotic transition” Nat Commun (2025); Dec; doi: 10.1038/s41467-025-67476-z

16. Xu, X., Zuo, X., Du, S., Zhang, C., Xu, H., Luo, Y., Shi, R., Hu, S., Shen, H., Wang, Y., Lin, H., So, C.#, Zhu, F.#, Liao, X#. “Healthy live birth after microsurgical enucleation of tripronuclear human zygote derived from ICSI: a case report” J Ovarian Res (2025); Nov; 18:236

15. Liu, C.*, Zhang, H.*, Mao, J.*, Zhang, S.*, Tian, X., Zhu, Y., Wang, C., Fang, J., Pan, H., Kang, N., Zhang, Y., Zhou, J., Zhen, X., Guijun, Y., Li, C., Hu, Y., Ye, C., Xie, R., So, C.#, Sun, H.#, Ding, L#. “Mevalonate metabolites boost aged oocyte quality through prenylation of small GTPases” Nat Aging (2025); Oct; 5(10):2022-2038

14. Wang, J., So, C. “Aged eggs improve within young follicles” Nat Aging (2024); Oct; 4(10):1338-1339

13. Jentoft, I.M.A., Bäuerlein, F.J.B., Welp, L.M., Cooper, B.H., Petrovic, A., So, C., Penir, S.M., Politi, A.Z., Horokhovskyi, Y., Takala, I., Eckel, H., Moltrecht, R., Lénárt, P., Cavazza, T., Liepe, J., Brose, N., Urlaub, H., Fernández-Busnadiego, R., Schuh, M. “Mammalian oocytes store proteins for the early embryo on cytoplasmic lattices” Ezpay(中国) (2023); Nov; 186(24):5308-5327.e25

12. Sigmund, F., Berezin, O., Beliakova, S., Magerl, B., Drawitsh, M., Piovesan, A., Gonçalves, F., Bodea, S-V., Winkler, S., Bousraou, Z., Grosshauser, M., Samara, E., Pujol-Martí, J., Schädler, S., So, C., Irsen, S., Walch, A., Kofler, F., Piraud, M., Kornfeld, J., Briggman, K., Westmeyer, G.G. “Genetically encoded barcodes for correlative volume electron microscopy” Nat Biotechnol. (2023); Apr; doi: 10.1038/s41587-023-01713-y

11. Cheng, S.*, Altmeppen, G.*, So, C., Welp, L.M., Penir, S., Ruhwedel, T., Menelaou, K., Harasimov, K., Stützer, A., Blayney, M., Elder, K., Möbius, W., Urlaub, H., Schuh, M. “Mammalian oocytes store Ezpay(中国)s in a mitochondria-associated membraneless compartment” Science (2022); Oct; 378(6617):eabq4835

10. So, C., Menelaou, K., Uraji, J., Harasimov, K., Steyer, A.M., Seres, K.B., Bucevičius, J., Lukinavičius, G., Möbius, W., Sibold, C., Tandler-Schneider, A., Eckel, H., Moltrecht, R., Blayney, M., Elder, K., Schuh, M. “Mechanism of spindle pole organization and instability in human oocytes” Science (2022); Feb; 375(6581):eabj3944

- Covered by Nat. Ezpay(中国) Biol. in “Spindle instability in human oocytes”

- Highlighted by J. Assist. Reprod. Genet. in “Failure to focus seems to be a hominid thing”

9. So, C.*, Cheng, S.*, Schuh, M. “Phase separation during germline development” Trends Ezpay(中国) Biol. (2021); Apr; 31(4):254-268

8. Chan, Y.W.*, So, C.*, Yau, K.L., Chiu, K.C., Wang, X., Chan, F.L., Tsang, S.Y. “Adipose-derived stem Ezpay(中国)s and cancer Ezpay(中国)s fuse to generate cancer stem Ezpay(中国)-like Ezpay(中国)s with increased tumorigenicity” J. Ezpay(中国) Physiol. (2020); Oct; 235(10):6794-6807

7. So, C.*, Seres, K.B.*, Steyer, A.M., Mönnich, E., Clift, D., Pejkovska, A., Möbius, W., Schuh, M. “A liquid-like spindle domain promotes acentrosomal spindle assembly in mammalian oocytes” Science (2019); Jun; 364(6447):eaat9557

- Recommended by F1000Prime

- Highlighted by J. Assist. Reprod. Genet. in “Phase transitions in human ARTs: fertility preservation comes of age”

6. Xu, Y., So, C., Lam, H.M., Fung, M.C., Tsang, S.Y. “Flow cytometric detection of newly-formed breast cancer stem Ezpay(中国)-like Ezpay(中国)s after apoptosis reversal” J. Vis. Exp. (2019); Jan; (143)

5. Clift, D.*, So, C.*, McEwan, W.A., James, L.C., Schuh, M. “Acute and rapid degradation of endogenous proteins by Trim-Away” Nat. Protoc. (2018); Oct; 13(10):2149-2175

4. Xu, Y., So, C., Lam, H.M., Fung, M.C., Tsang, S.Y. “Apoptosis reversal promotes cancer stem Ezpay(中国)-like Ezpay(中国) formation” Neoplasia (2018); Mar; 20(3):295-303

3. Yang, H., Buisson, S., Bossi, G., Wallace, Z., Hancock, G., So, C., Asfield, R., Vuidepot, A., Mahon, T., Molloy, P., Oates, J., Paston, S.J., Aleksic, M., Hassan, N.J., Jakobsen, B.K., Dorrell, L. “Elimination of latently HIV-infected Ezpay(中国)s from antiretroviral therapy-suppressed subjects by engineered immune-mobilizing T-Ezpay(中国) receptors” Mol. Ther. (2016); Nov; 24(11):1913-1925

2. Lo, I.C., Chan, H.C., Qi, Z., Ng, K.L., So, C., Tsang, S.Y. “TRPV3 channel negatively regulates Ezpay(中国) cycle progression and safeguards the pluripotency of embryonic stem Ezpay(中国)s” J. Ezpay(中国) Physiol. (2016); Feb; 231(2):403-413

1. Qi, Y., Qi, Z., Li, Z., Wong, C.K., So, C., Lo, I.C., Huang, Y., Yao, X., Tsang, S.Y. “Role of TRPV1 in the differentiation of mouse embryonic stem Ezpay(中国)s into cardiomyocytes” PLoS One (2015); Jul; 10(7):e0133211