Neuronatin基因研究进展

Progress in The Neuronatin Gene

Neuronatin (Nnat)是最近克隆的脑特异表达的新基因 ,在大脑发育过程中被选择性地剪接 .人Nnat基因全长 3 973bp ,含有 3个外显子和 2个内含子 .NnatmRNA有α和β两种剪接形式 ,分别编码 81个和 5 4个氨基酸 ,两者具有同一相位的开放阅读框架 ,差别在于 β形式中间的外显子被剪切掉 .人Nnat是单拷贝基因 ,定位于染色体 2 0q11 2～ 12 .小鼠Nnat基因定位于 2号染色体末端 .该基因是印记基因 (imprintedgene) ,仅在父本来源的等位基因表达 ,而母本来源的等位基因则被甲基化不能表达 .该基因在胚胎期及出生后早期大量表达 ,而在成年和衰老动物大脑中表达明显降低 ,因此推测该基因与大脑的发育和分化密切相关 .成年动物中垂体前叶是NnatmRNA唯一强表达的地方 .推测其蛋白质产物具有疏水N端和亲水C端 ,是跨膜蛋白 ,其确切功能尚属未知 .

Neuronatin (Nnat) is a recently cloned brain-specific gene that is selectively expressed during brain development. Human Nnat gene spans 3 973 bases and contains three exons and two introns. Nnat mRNA has two different splice isoforms, alpha and beta, the former encoding a protein of 81 amino acids and the latter 54 amino acids. These two isoforms share the same open reading frame, but the a-form contained an additional 81 bp sequence inserted in the middle of the coding region. The human Nnat is a single copy gene located at chromosome 20q11. 2 similar to 12, while the rat gene is located on the distal region of chromosome 2, 2H1. Nnat is an imprinted gene and expressed from the paternal allele, while the maternal allele is methylated and silenced. As Nnat is highly expressed in the central nervous system from mid-gestation through early postnatal development and down-regulated in adulthood and senescence, Nnat may be involved in brain development and differentiation. The expression is also detected in the adult brain stem, suggesting roles in neuroplasticity. The deduced protein sequence contains a hydrophobic N-terminal and a hydrophilic C-terminal, and appears to code for a transmembrane protein. The biological function of Nnat remains to be elucidated.