The mammalian lamina-associated polypeptide 2 (LAP2) gene encodes six isoforms (LAP2alpha, beta, delta, epsilon, gamma, zeta) that are synthesised from alternatively spliced mRNAs. The mammalian LAP2alpha is one of the predominant isoforms and localised in the nucleoplasm whereas LAP2beta, delta, epsilon, and gamma are integral membrane proteins of the inner nuclear membrane. We have analysed the LAP2 gene structure of the zebrafish Danio rerio as an attractive lower vertebrate model organism. The zebrafish LAP2 (ZLAP2) gene without regulatory sequences spans approximately 19 kb of genomic DNA. It contains 15 exons that encode the isoforms ZLAP2beta, gamma, and omega which are localised in the inner nuclear membrane. By radiation hybrid mapping, we have located the gene onto linkage group 4 between EST markers fc01g04 (213.97cR) and fb49f01 (215.69cR). The identification of a chicken genomic clone comprising the complete coding region of the avian LAP2 gene enabled us to compare the LAP2 gene structure amongst vertebrates. In contrast to the mammalian LAP2 gene, the zebrafish and the chicken sequences do not encode for an alpha-isoform. In parallel we searched for an alpha-isoform in birds using polyclonal and monoclonal LAP2 antibodies specific for the common evolutionary conserved aminoterminal domain present in all isoforms. We detected LAP2beta as the predominant isoform but no LAP2alpha in tissues of 10-day-old chicken embryos and cultured chicken fibroblasts thus confirming the genomic analysis. The comparison of each zebrafish and chicken LAP2 exon with the corresponding exons of the human LAP2 gene demonstrates that the degree of identity at the amino acid level is much higher between the human and chicken than between the human and zebrafish sequences. By Blast search with the nucleotide and amino acid sequences of the human LAP2alpha, we did not find any significant homologies in databases of the zebrafish and chicken sequences. Our data suggest that LAP2alpha is a novelty of mammals.

中文翻译：

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斑马鱼和鸡的椎板相关多肽2（LAP2）基因：非哺乳动物脊椎动物不合成LAP2alpha同工型。

哺乳动物的椎板相关多肽2（LAP2）基因编码从异构剪接的mRNA合成的六个同工型（LAP2alpha，beta，delta，ε，γ，zeta）。哺乳动物的LAP2alpha是主要的亚型之一，位于核质中，而LAP2beta，δ，ε和γ是内核膜的完整膜蛋白。我们已经分析了斑马鱼斑马鱼作为有吸引力的低等脊椎动物模型生物的LAP2基因结构。没有调控序列的斑马鱼LAP2（ZLAP2）基因跨越大约19 kb的基因组DNA。它包含15个外显子，它们编码位于核内膜中的同工型ZLAP2beta，γ和ω。通过辐射杂交作图，我们将该基因定位到EST标记fc01g04（213.97cR）和fb49f01（215。69cR）。包含禽类LAP2基因完整编码区的鸡基因组克隆的鉴定使我们能够在脊椎动物之间比较LAP2基因的结构。与哺乳动物的LAP2基因相反，斑马鱼和鸡的序列不编码α-亚型。平行地，我们使用对所有同种型中存在的共同进化保守的氨基末端结构域具有特异性的多克隆和单克隆LAP2抗体，在鸟类中搜索α-同种型。我们在10天大的鸡胚胎和培养的鸡成纤维细胞的组织中检测到LAP2beta是主要的同工型，但没有LAP2alpha，从而证实了基因组分析。每种斑马鱼和鸡的LAP2外显子与人类LAP2基因的相应外显子的比较表明，人与鸡之间氨基酸水平的同一性程度远高于人与斑马鱼序列之间。通过Blast搜索人LAP2alpha的核苷酸和氨基酸序列，我们在斑马鱼和鸡序列的数据库中未发现任何重要的同源性。我们的数据表明，LAP2alpha是哺乳动物的一种新奇事物。