Amemiya C T, Litman G W
Laboratory of Molecular Genetics, Tampa Bay Research Institute, Saint Petersburg, FL 33716.
Proc Natl Acad Sci U S A. 1990 Jan;87(2):811-5. doi: 10.1073/pnas.87.2.811.
The immunoglobulin heavy-chain variable region (VH) locus in a phylogenetically primitive teleost (Elops saurus) has been characterized by a strategy that relied initially on cross-hybridization between genomic VH segments and a murine VH probe. Using a homologous (Elops) VH probe and DNA sequencing, this gene family has been shown to be complex and to contain overt pseudogenes. A homologous probe also has been used to isolate a full copy length cDNA containing constant (CH) as well as joining (JH) and VH regions. Genomic analyses using CH-, JH-, and VH-specific probes have demonstrated the presence of only a single hybridizing CH and several JH elements. JH-CH linkage is less than or equal to 3.6 kilobases (kb) and VH-CH linkage is less than or equal to 100 kb, as estimated by field-inversion gel electrophoresis. An additional VH family sharing less than 50% nucleotide identity with the prototype Elops VH sequence is described. Taken together, these results suggest that the immunoglobulin VH locus in a comparatively primitive teleost resembles the VH locus in mammals, but not that found in the more phylogenetically distant elasmobranchs. The evolutionary radiations of cartilaginous and bony fishes are associated with a dramatic change in the organization and, presumably, regulation of immunoglobulin genes. The origins of the modern VH gene locus can be traced to the primitive teleost fishes.
在一种系统发育上原始的硬骨鱼（蜥海鲢）中，免疫球蛋白重链可变区（VH）基因座的特征是采用了一种策略，该策略最初依赖于基因组VH片段与鼠VH探针之间的交叉杂交。使用同源（海鲢）VH探针和DNA测序，已证明该基因家族很复杂且包含明显的假基因。同源探针也已用于分离一个包含恒定区（CH）以及连接区（JH）和VH区的全长cDNA。使用CH、JH和VH特异性探针进行的基因组分析表明，仅存在一个杂交的CH和几个JH元件。通过场反转凝胶电泳估计，JH-CH连接小于或等于3.6千碱基（kb），VH-CH连接小于或等于100 kb。描述了另一个与原型海鲢VH序列核苷酸同一性小于50%的VH家族。综上所述，这些结果表明，相对原始的硬骨鱼中的免疫球蛋白VH基因座类似于哺乳动物中的VH基因座，但与系统发育上更远的板鳃亚纲动物中的VH基因座不同。软骨鱼和硬骨鱼的进化辐射与免疫球蛋白基因的组织以及推测的调控方面的巨大变化有关。现代VH基因座的起源可以追溯到原始的硬骨鱼。
