Fuller M T, Caulton J H, Hutchens J A, Kaufman T C, Raff E C
J Cell Biol. 1987 Mar;104(3):385-94. doi: 10.1083/jcb.104.3.385.
A recessive male sterile mutation (B2t8) that encodes a stable variant of the testis-specific beta 2-tubulin of Drosophila causes the assembly of aberrant microtubules both in vivo and in vitro. The B2t8 mutation appears to cause defects in the formation of interprotofilament bonds. In testes from homozygous mutant males, the most commonly observed aberrant structures were sheets of protofilaments curved to form an S in cross section rather than a normal, closed microtubule. These characteristic S-shaped structures appear in the meiotic spindle, in place of axonemes in differentiating spermatids, and in cytoplasmic microtubules, including those that lie next to the nucleus during nuclear elongation. Homozygous mutant males exhibit defects in chromosome movement and cytokinesis during meiosis, flagellar elongation, and nuclear shaping, indicating that the ability to form normal closed microtubules is required for each of these events. The presence of the aberrant microtubules in three architecturally different microtubule arrays demonstrates conclusively the multifunctional nature of the beta 2-tubulin gene product. Although the mutant beta 2-tubulin subunit causes assembly of aberrant microtubules in vitro and in homozygous males, in the presence of wild-type beta 2-tubulin in heterozygous males, the variant subunit coassembles with the wild-type subunit into functional sperm.
一种隐性雄性不育突变（B2t8）编码果蝇睾丸特异性β2-微管蛋白的稳定变体，该突变在体内和体外均会导致异常微管的组装。B2t8突变似乎导致原纤维间键形成的缺陷。在纯合突变雄性果蝇的睾丸中，最常观察到的异常结构是原纤维片层，其在横切面上弯曲形成S形，而不是正常的闭合微管。这些特征性的S形结构出现在减数分裂纺锤体中、分化精子细胞的轴丝位置以及细胞质微管中，包括在核伸长过程中位于细胞核旁边的微管。纯合突变雄性果蝇在减数分裂期间的染色体移动和胞质分裂、鞭毛伸长以及细胞核塑形方面表现出缺陷，这表明这些事件中的每一个都需要形成正常闭合微管的能力。异常微管在三种结构不同的微管阵列中的存在确凿地证明了β2-微管蛋白基因产物的多功能性质。尽管突变的β2-微管蛋白亚基在体外和纯合雄性果蝇中会导致异常微管的组装，但在杂合雄性果蝇中存在野生型β2-微管蛋白的情况下，变异亚基会与野生型亚基共同组装成功能性精子。
