Reyes A A, Small S J, Akeson R
Division of Basic Research, Children's Hospital Research Foundation, Cincinnati, Ohio 45229-2899.
Mol Cell Biol. 1991 Mar;11(3):1654-61. doi: 10.1128/mcb.11.3.1654-1661.1991.
The major membrane-associated or transmembrane isoforms of the neural cell adhesion molecule (NCAM) are generated by alternative splicing at the 3' end of the mRNA. Further diversity in NCAM structure is observed in the extracellular region of the polypeptide, where the insertion of additional amino acid residues can result from alternative splicing events occurring at the exon 7-exon 8 and exon 12-exon 13 junctions. Here we report the characterization of tissue-specific patterns of alternative splicing at the exon 12-exon 13 junction by using the polymerase chain reaction. Nine alternatively spliced sequences in rat heart between exon 12 and exon 13 were identified. Each sequence consisted of different combinations of the three small exons (15, 48, and 42 bp in length) and the AAG triplet that make up MSD1, the 108-bp muscle-specific sequence found in human skeletal muscle NCAM (G. Dickson, H.J. Gower, C. H. Barton, H. M. Prentice, V. L. Elsom, S. E. Moore, R. D. Cox, C. Quinn, W. Putt, and F. S. Walsh, Cell 50:1119-1130, 1987). Although the rat equivalent of MSD1 (designated 15+ 48+ 42+ 3+) was detected in all ages of heart examined, it was only one of four or five major splice combinations at any given age. The only alternatively spliced sequence found in the exon 7-exon 8 junction of heart NCAM mRNA was the 30-bp variable alternatively spliced exon previously identified in rat brain. Twenty-seven NCAM forms with distinct sequences were found by analysis of individual NCAM transcripts from postnatal day 1 heart tissue for alternative splicing at the exon 7-exon 8 junction, the exon 12-exon 13 junction and the 3' end. Several combinations of splicing patterns in these three different regions of the gene appeared to be preferentially expressed. The observation that the expression of alternatively spliced forms of NCAM is developmentally regulated suggests a role for NCAM diversity in cardiac development.
神经细胞黏附分子（NCAM）的主要膜相关或跨膜异构体是由mRNA 3'端的可变剪接产生的。在多肽的细胞外区域观察到NCAM结构的进一步多样性，其中额外氨基酸残基的插入可能源于外显子7-外显子8和外显子12-外显子13连接处发生的可变剪接事件。在此，我们报告了通过聚合酶链反应对组织特异性可变剪接模式在外显子12-外显子13连接处的特征分析。在大鼠心脏中外显子12和外显子13之间鉴定出9种可变剪接序列。每个序列由三个小外显子（长度分别为15、48和42 bp）和构成MSD1的AAG三联体的不同组合组成，MSD1是在人骨骼肌NCAM中发现的108 bp肌肉特异性序列（G. Dickson、H.J. Gower、C.H. Barton、H.M. Prentice、V.L. Elsom、S.E. Moore、R.D. Cox、C. Quinn、W. Putt和F.S. Walsh，《细胞》50:1119 - 1130，1987）。尽管在所检查的所有年龄段的心脏中都检测到了大鼠等同的MSD1（命名为15 + 48 + 42 + 3 +），但在任何给定年龄它只是四到五种主要剪接组合之一。在心脏NCAM mRNA的外显子7-外显子8连接处发现的唯一可变剪接序列是先前在大鼠脑中鉴定出的30 bp可变外显子。通过分析出生后第1天心脏组织中单个NCAM转录本在外显子7-外显子8连接处、外显子12-外显子13连接处和3'端的可变剪接，发现了27种具有不同序列的NCAM形式。在基因的这三个不同区域中，几种剪接模式的组合似乎优先表达。NCAM可变剪接形式的表达受发育调控这一观察结果表明NCAM多样性在心脏发育中起作用。
