Radice G P, Malacinski G M
Department of Biology, Indiana University, Bloomington 47405.
Dev Biol. 1989 Jun;133(2):562-8. doi: 10.1016/0012-1606(89)90058-4.
In amphibians, the composition and pattern of expression of the myosin heavy chain (myHC) gene family are mostly unknown. To understand better the regulation of this complex family, we screened cDNA libraries from swimming tadpole and adult leg muscle RNA and have isolated and partially sequenced clones for several myHCs. Two of these, E3 and E19, first appear in mesoderm at late gastrula stage and are coexpressed with muscle actin. They increase in abundance in trunk and tail myotome until metamorphosis, when they begin to decline. E3 and E19 are also both expressed in hind leg muscle at the beginning of metamorphosis, but decline to low levels in adult leg muscle. A new transcript, A7, first appears during early metamorphosis in both the tail and hind leg skeletal muscle. A7 transcripts then decline in degenerating tail but persist in hind leg through metamorphosis and in adults. Two other embryonic myHCs, E14 and E15, code for isoforms closely related to E19 and may be alleles or duplications. Although sequence comparisons with myHCs from other vertebrates could not correlate the transcripts with specific protein isoforms, from the pattern of expression E3 and E19 apparently code for embryonic fast skeletal myHC isoforms, whereas A7 codes for an adult skeletal isoform.
在两栖动物中，肌球蛋白重链（myHC）基因家族的组成和表达模式大多未知。为了更好地理解这个复杂家族的调控机制，我们从蝌蚪游泳肌和成年腿部肌肉RNA中筛选了cDNA文库，并分离出了几个myHC的克隆并进行了部分测序。其中两个，E3和E19，最早出现在原肠胚晚期的中胚层，并与肌肉肌动蛋白共同表达。它们在躯干和尾部肌节中的丰度增加，直至变态期开始下降。E3和E19在变态期开始时也在腿部肌肉中表达，但在成年腿部肌肉中降至低水平。一个新的转录本A7，最早出现在变态初期的尾部和后腿骨骼肌中。然后，A7转录本在退化的尾部中下降，但在变态期及成年期的后腿中持续存在。另外两个胚胎期的myHC，E14和E15，编码的异构体与E19密切相关，可能是等位基因或重复基因。尽管与其他脊椎动物的myHC进行序列比较无法将这些转录本与特定的蛋白质异构体相关联，但从表达模式来看，E3和E19显然编码胚胎期快速骨骼肌myHC异构体，而A7编码成年骨骼肌异构体。
