米兰达果蝇（Drosophila miranda）不断进化的性染色体上的淀粉酶基因簇。
The Amylase gene cluster on the evolving sex chromosomes of Drosophila miranda.
作者信息
Steinemann S, Steinemann M
机构信息
Institut für Genetik, Heinrich Heine Universität Düsseldorf, Universitätsstrasse 1, D-40225, Düsseldorf, Germany.
出版信息
Genetics. 1999 Jan;151(1):151-61. doi: 10.1093/genetics/151.1.151.
On the basis of chromosomal homology, the Amylase gene cluster in Drosophila miranda must be located on the secondary sex chromosome pair, neo-X (X2) and neo-Y, but is autosomally inherited in all other Drosophila species. Genetic evidence indicates no active amylase on the neo-Y chromosome and the X2-chromosomal locus already shows dosage compensation. Several lines of evidence strongly suggest that the Amy gene cluster has been lost already from the evolving neo-Y chromosome. This finding shows that a relatively new neo-Y chromosome can start to lose genes and hence gradually lose homology with the neo-X. The X2-chromosomal Amy1 is intact and Amy2 contains a complete coding sequence, but has a deletion in the 3'-flanking region. Amy3 is structurally eroded and hampered by missing regulatory motifs. Functional analysis of the X2-chromosomal Amy1 and Amy2 regions from D. miranda in transgenic D. melanogaster flies reveals ectopic AMY1 expression. AMY1 shows the same electrophoretic mobility as the single amylase band in D. miranda, while ectopic AMY2 expression is characterized by a different mobility. Therefore, only the Amy1 gene of the resident Amy cluster remains functional and hence Amy1 is the dosage compensated gene.
基于染色体同源性，拟果蝇（Drosophila miranda）中的淀粉酶基因簇必定位于第二对性染色体，即新X染色体（X2）和新Y染色体上，但在所有其他果蝇物种中它是常染色体遗传的。遗传证据表明新Y染色体上没有活性淀粉酶，并且X2染色体位点已经表现出剂量补偿。多条证据强烈表明，Amy基因簇已经从不断进化的新Y染色体上丢失。这一发现表明，一条相对较新的新Y染色体可能开始丢失基因，从而逐渐与新X染色体失去同源性。X2染色体上的Amy1是完整的，Amy2包含一个完整的编码序列，但在3'侧翼区域有一个缺失。Amy3在结构上受到侵蚀，并且因缺少调控基序而受到阻碍。对转基因黑腹果蝇（D. melanogaster）中拟果蝇X2染色体上的Amy1和Amy2区域进行功能分析，发现有异位AMY1表达。AMY1与拟果蝇中的单一淀粉酶条带具有相同的电泳迁移率，而异位AMY2表达的特征是具有不同的迁移率。因此，常驻Amy基因簇中只有Amy1基因仍具功能，所以Amy1是剂量补偿基因。
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