非洲爪蟾：生物学模式动物中的王子Xenopus laevis: the prince of model organisms

作者：毛炳宇（中国科学院昆明动物研究所）Author: Mao Bingyu (Kunming Institute of Zoology, CAS)

①帅气的非洲爪蟾① An impressive animal

非洲爪蟾（Xenopus laevis，African clawed frog）是一种原产于非洲撒哈拉以南地区的水栖型蛙类。成体体长 8–12 cm，体形扁平，腹部银白，背部橄榄绿至棕褐色；前肢纤细无蹼，后肢粗壮，内侧三趾具黑色角质爪。无外耳，皮肤光滑，侧线系统发达。它终生栖居水中，几乎不主动上岸，依靠强健的后肢与流线型躯体在水中高速穿行。Xenopus laevis is a permanently aquatic, sub-Saharan African frog, 8–12 cm in length. It has a flattened body, silver-white ventrum, and olive-brown dorsum. Its slender, unwebbed forelimbs contrast with muscular hindlimbs bearing three black clawed toes. Earless, smooth-skinned, and equipped with a functional lateral-line system, it spends its entire life in water, relying on powerful hindlimbs for rapid locomotion.

②从蛙到王子的蜕变——历史沿革② Rise to prominence — a brief history

1930 年代，妊娠试验：南非开普敦大学 Lancelot Hogben 发现，向非洲爪蟾注射孕妇尿液可在 8–12 小时内诱发排卵，即"霍格本（Hogben）试验"。这是世界上第一个成功的生物妊娠诊断方法，使爪蟾迅速被全球引种用于妇产科临床。1930s – Pregnancy test: Lancelot Hogben (Cape Town) discovered that injecting pregnant women's urine into X. laevis induced ovulation within 8–12 hours — the "Hogben test", the world's first successful biological pregnancy test, driving worldwide captive importation.

1962 年，核移植实验：英国剑桥大学 John Gurdon 将爪蟾肠上皮细胞的细胞核移植到去核的爪蟾卵母细胞中，获得了正常发育的蝌蚪。这一里程碑实验证明了分化细胞核的全能性，奠定了克隆技术与诱导多能干细胞（iPSC）的理论基础，Gurdon 为此获得 2012 年诺贝尔生理学或医学奖。1962 – Nuclear transplantation: John Gurdon (Cambridge) transplanted intestinal epithelial nuclei into enucleated Xenopus oocytes, producing normal tadpoles. This milestone demonstrated somatic cell nuclear totipotency, underpinning cloning technology and iPSC reprogramming. Gurdon received the 2012 Nobel Prize in Physiology or Medicine.

1971 年，成熟促进因子（MPF）：Masui Y 与 Markert CL 在爪蟾卵中发现了 MPF（maturation-promoting factor），后被证明是 Cdc2/Cyclin B 复合物，是细胞周期调控研究的奠基性发现。1971 – MPF discovery: Masui Y and Markert CL identified MPF (maturation-promoting factor) in Xenopus oocytes. MPF was subsequently shown to be the Cdc2/Cyclin B complex, a foundational discovery in cell-cycle regulation.

1980 年代，体外转录与卵母细胞表达系统：利用爪蟾卵母细胞巨大的体积（直径 1–1.3 mm）、强大的翻译机器与天然的质膜环境，科学家将外源 mRNA 或 DNA 注射入卵母细胞，实现外源离子通道、受体与酶的高效功能表达。这一系统至今仍是离子通道功能研究和药物筛选的黄金标准。1980s – Oocyte expression system: The giant oocyte (1–1.3 mm diameter), with its powerful translational machinery and native plasma membrane, became the gold-standard system for expressing exogenous ion channels, receptors and enzymes via mRNA or DNA microinjection — a platform still widely used today.

③王子的丰功伟绩——主要科学贡献③ Scientific contributions

• 发现 Spemann–Mangold 组织者信号分子（Chordin、Noggin、Follistatin）的分子身份；Identification of Spemann–Mangold organizer signaling molecules (Chordin, Noggin, Follistatin);
• 建立 Wnt/β-Catenin、TGF-β/Nodal、FGF 等脊椎动物胚胎发育核心信号通路；Establishment of core vertebrate embryonic signaling pathways: Wnt/β-catenin, TGF-β/Nodal, FGF;
• 利用卵提取物体外重构 DNA 复制、核膜组装与有丝分裂纺锤体；In-vitro reconstitution of DNA replication, nuclear envelope assembly and mitotic spindle using egg extracts;
• 率先利用吗啉环寡聚核苷酸（Morpholino）进行基因敲降；Pioneer use of Morpholino antisense oligonucleotides for gene knockdown;
• 为离子通道、G蛋白偶联受体和转运蛋白提供标准化的电生理功能表达平台（TEVC）。Standardized TEVC electrophysiology platform for ion channels, GPCRs and transporters.

④王子的近亲——X. tropicalis④ A close relative — X. tropicalis

X. tropicalis（西部爪蟾）是唯一二倍体爪蟾种，基因组约 1.5 Gb，2010 年完成测序。相比 X. laevis 的四倍体基因组，X. tropicalis 更便于遗传操作（ENU 突变体文库、CRISPR/Cas9）。两种爪蟾互补使用，构成爪蟾模式动物生态系的核心。X. tropicalis (Western clawed frog) is the only diploid Xenopus species. Its ~1.5-Gb genome was sequenced in 2010, making it easier for genetics (ENU mutagenesis, CRISPR). The two species are complementary and together form the core of the Xenopus model-organism ecosystem.

参考文献References

1. Gurdon JB. (2012) The egg and the nucleus: a battle for supremacy. Nobel Lecture. Angew Chem Int Ed 52(12):3177–3180.
2. Harland R & Grainger R. (2011) Xenopus research: metamorphosed by genetics and genomics. Trends Genet 27(12):507–515.
3. Masui Y & Markert CL. (1971) Cytoplasmic control of nuclear behavior during meiotic maturation of frog oocytes. J Exp Zool 177(2):129–145.
4. Gurdon JB & Hopwood N. (2000) The introduction of Xenopus laevis into developmental biology. Int J Dev Biol 44(1):43–50.