Table 1.

The phase (reading frame) and length of the coding exons of the fast/developmental MYH genes

Exon length
Coding exonPhaseEmbryonicIIAIIXIIBPerinatalMYH13
3(0,0)204183204204210204
4(0,0)144144144144144144
5(0,1)157157157157157157
6(1,2)282828282828
7(2,0)109115115115109112
8(0,0)939393939393
9(0,1)646464646464
10(1,1)999999999999
11(1,0)104104104104104104
12(0,1)139139139139139139
13(1,0)119119119119119119
14(0,0)150150150150150150
15(0,0)171171171171171171
16(0,1)307310310310310310
17(1,0)716871716874
18(0,1)888888888888
19(1,2)118118118118118118
20(2,0)124124124124124124
21(0,2)137137137137137137
22(2,0)256256256256256256
23(0,0)243243243243243243
24(0,0)177177177177177177
25(0,2)146146146146146146
26(2,0)919191919191
27(0,0)390390390390390390
28(0,1)127127127127127127
29(1,0)119119119119119119
30(0,2)197197197197197197
31(2,0)184184184184184184
32(0,1)166166166166166166
33(1,0)125125125125125125
34(0,0)309309309309309309
35(0,0)204204204204204204
36(0,0)126126126126126126
37(0,0)171171171171171171
38(0,0)105105105105105105
39(0,0)969696969696
40(0,0)138150150150147135
41(0,0)2412
  • The exon structure of these genes is highly conserved. The pattern of split codons is identical among all the genes. Exon lengths are also identical, with four exceptions. The exons encoding the N and C termini reflect known differences in amino acid sequence; and the C termini of MYH13 and the embryonic MYH are encoded by two exons, whereas the homologous sequences of the other MYHs are encoded by a single exon.

    Additional length variations occur in the exons that encode the variable-length loop 1 and loop 2. The variation in loop 1 appears to be due to exon slippage at the 3′ boundary of exon 7, as does the variation in loop 2, which occurs at the boundary of exons 16 and 17.