Kojima T, Ishimaru S, Higashijima S, Takayama E, Akimaru H, Sone M, Emori Y, Saigo K
Department of Biophysics and Biochemistry, Faculty of Science, University of Tokyo, Japan.
Proc Natl Acad Sci U S A. 1991 May 15;88(10):4343-7. doi: 10.1073/pnas.88.10.4343.
The Bar mutation B of Drosophila melanogaster and optic morphology mutation Om(1D) of Drosophila ananassae result in suppression of ommatidium differentiation at the anterior portion of the eye. Examinations was made to determine the genes responsible for these mutations. Both loci were found to share in common a different type of homeobox gene, which we call "BarH1." Polyptides encoded by D. melanogaster and D. ananassae BarH1 genes consist of 543 and 604 amino acids, respectively, with homeodomains identical in sequence except for one amino acid substitution. A unique feature of these homeodomains is that the phenylalanine residue in helix 3, conserved in all metazoan homeodomains so far examined, is replaced by a tyrosine residue. By Northern blotting, considerably more BarH1 RNA was detected in the Bar mutant than in wild type. P element-mediated transformation showed Bar-like eye malformation to be induced by transient overexpression of the BarH1 gene in the late third-instar larvae. Somatic recombination analysis indicated normal gene functions of the Bar region, including the BarH1 gene, to be required for normal eye morphogenesis.
黑腹果蝇的Bar突变B和拟果蝇的视形态突变Om(1D)会导致眼睛前部小眼分化受到抑制。为了确定导致这些突变的基因，我们进行了相关检测。结果发现这两个位点都共享一种不同类型的同源异型框基因，我们将其称为“BarH1”。黑腹果蝇和拟果蝇的BarH1基因编码的多肽分别由543和604个氨基酸组成，其同源结构域的序列除了一个氨基酸替换外完全相同。这些同源结构域的一个独特特征是，在迄今为止所研究的所有后生动物同源结构域中都保守的螺旋3中的苯丙氨酸残基被酪氨酸残基所取代。通过Northern印迹法检测发现，Bar突变体中检测到的BarH1 RNA比野生型中的要多得多。P因子介导的转化实验表明，在三龄幼虫后期短暂过表达BarH1基因会诱导出类似Bar的眼睛畸形。体细胞重组分析表明，包括BarH1基因在内的Bar区域的正常基因功能是正常眼睛形态发生所必需的。
