Kusiak J W, Norton D D
Molecular Neurobiology Unit, National Institute on Aging, NIH, F.S. Key Medical Center, Baltimore, MD 21224.
Brain Res Mol Brain Res. 1993 Oct;20(1-2):64-70. doi: 10.1016/0169-328x(93)90110-b.
A splice variant of the NMDA receptor (NMDAR1) was discovered containing a deletion of 37 amino acids near the carboxyl tail and has been designated NMDAR1b. The 111 nucleotides corresponding to the deleted amino acid sequence were found in a separate exon bounded by consensus intron/exon junction sequences in rat genomic DNA. A partial restriction map of genomic DNA bounding this region placed the deleted exon approximately 600 base pairs (bp) downstream of the upstream exon. RT/PCR analysis of RNA from different brain regions showed that the deletion variant is more abundantly expressed in the brain stem and cerebellum while the full-length form is expressed more abundantly in the olfactory bulb, striatum, hippocampus, and cortex. Northern analysis of poly(A)+ RNA from different brain regions with probes specific for the deleted exon (i.e., full-length form) and for the splice junction (deletion form) indicated approximately 4.4 kb transcripts. The probe for the deleted exon hybridized to transcripts in olfactory bulb, cortex, striatum, and hippocampus while the splice junction probe hybridized most strongly to transcripts in cerebellum. The results suggest an interesting rostral to caudal shift in the expression of splice variants of the NMDAR1 which may signify important functional differences in native forms of NMDA receptors.
发现了NMDA受体（NMDAR1）的一种剪接变体，其在羧基末端附近缺失了37个氨基酸，并被命名为NMDAR1b。在大鼠基因组DNA中，与缺失氨基酸序列相对应的111个核苷酸存在于一个由共有内含子/外显子连接序列界定的单独外显子中。限定该区域的基因组DNA的部分限制性图谱显示，缺失的外显子位于上游外显子下游约600个碱基对（bp）处。对来自不同脑区的RNA进行RT/PCR分析表明，缺失变体在脑干和小脑中表达更为丰富，而全长形式在嗅球、纹状体、海马体和皮质中表达更为丰富。用针对缺失外显子（即全长形式）和剪接连接点（缺失形式）的探针，对来自不同脑区的多聚腺苷酸（poly(A)+）RNA进行Northern分析，结果显示转录本约为4.4 kb。针对缺失外显子的探针与嗅球、皮质、纹状体和海马体中的转录本杂交，而剪接连接点探针与小脑中的转录本杂交最强。这些结果表明，NMDAR1剪接变体的表达存在从吻侧到尾侧有意思的变化，这可能意味着NMDA受体天然形式存在重要的功能差异。
