Department of Biology, University of Maryland, College Park, MD, USA.
Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD, USA.
Nat Commun. 2020 Jun 2;11(1):2772. doi: 10.1038/s41467-020-16497-x.
Vestigial structures are key indicators of evolutionary descent, but the mechanisms underlying their development are poorly understood. This study examines vestigial eye formation in the teleost Astyanax mexicanus, which consists of a sighted surface-dwelling morph and multiple populations of blind cave morphs. Cavefish embryos initially develop eyes, but they subsequently degenerate and become vestigial structures embedded in the head. The mutated genes involved in cavefish vestigial eye formation have not been characterized. Here we identify cystathionine ß-synthase a (cbsa), which encodes the key enzyme of the transsulfuration pathway, as one of the mutated genes responsible for eye degeneration in multiple cavefish populations. The inactivation of cbsa affects eye development by increasing the transsulfuration intermediate homocysteine and inducing defects in optic vasculature, which result in aneurysms and eye hemorrhages. Our findings suggest that localized modifications in the circulatory system may have contributed to the evolution of vestigial eyes in cavefish.
退化结构是进化血统的关键指标，但它们的发育机制仍不清楚。本研究检查了硬骨鱼墨西哥脂鲤的退化眼形成，它由有视力的地表栖生物种和多个盲洞栖生物种组成。洞鱼胚胎最初发育出眼睛，但随后退化并成为嵌入头部的退化结构。参与洞鱼退化眼形成的突变基因尚未被描述。在这里，我们鉴定出半胱氨酸 β-合成酶 a (cbsa)，它编码转硫途径的关键酶，是导致多个洞鱼种群眼睛退化的突变基因之一。cbsa 的失活通过增加转硫中间产物同型半胱氨酸并诱导视神经管缺陷，导致动脉瘤和眼睛出血，从而影响眼睛发育。我们的发现表明，循环系统的局部修饰可能有助于洞鱼退化眼睛的进化。
