Spadafora Corrado
Istituto Superiore di Sanità, Viale Regina Elena 299, Rome 00161, Italy.
Hum Reprod. 2008 Apr;23(4):735-40. doi: 10.1093/humrep/dem425. Epub 2008 Feb 11.
Sperm-mediated gene transfer (SMGT) is a procedure through which new genetic traits are introduced in animals by exploiting the ability of spermatozoa to take up exogenous DNA molecules and deliver them to oocytes at fertilization. The interaction of exogenous DNA with sperm cells is a regulated process mediated by specific factors; among those, a reverse transcriptase (RT) activity plays a central role in SMGT. 'Retro-genes' are generated either through reverse transcription of exogenous RNA internalized in spermatozoa, or through sequential transcription, splicing and reverse transcription of exogenous DNA. The resulting retro-genes are delivered to oocytes and transmitted to embryos and born animals as low-copy, transcriptionally competent, extrachromosomal structures capable of determining new phenotypic traits. Retro-genes can be further transmitted through sexual reproduction from founders to their F1 progeny: new genetic and phenotypic features, unlinked to chromosomes, can thus be generated and inherited in a non-Mendelian ratio. We have called this phenomenon sperm-mediated 'reverse' gene transfer (SMRGT). Thus, a RT-mediated machinery operates in sperm cells and is responsible for the genesis and non-Mendelian propagation of new genetic information. The features of RT-generated traits elicited in SMRGT resemble those characterized in recent studies of RNA-mediated inheritance of extra-genomic information.
精子介导的基因转移（SMGT）是一种通过利用精子摄取外源DNA分子并在受精时将其传递给卵母细胞的能力，从而在动物中引入新遗传性状的方法。外源DNA与精子细胞的相互作用是一个由特定因子介导的调控过程；其中，逆转录酶（RT）活性在SMGT中起核心作用。“逆转录基因”要么通过精子内化的外源RNA的逆转录产生，要么通过外源DNA的顺序转录、剪接和逆转录产生。产生的逆转录基因被传递到卵母细胞，并作为能够决定新表型性状的低拷贝、转录活性的染色体外结构传递给胚胎和出生的动物。逆转录基因可以通过有性繁殖从创始者进一步传递给它们的F1后代：因此，可以产生与染色体无关的新的遗传和表型特征，并以非孟德尔比例遗传。我们将这种现象称为精子介导的“反向”基因转移（SMRGT）。因此，一种由RT介导的机制在精子细胞中起作用，并负责新遗传信息的产生和非孟德尔式传播。SMRGT中由RT产生的性状特征与最近关于基因组外信息的RNA介导遗传研究中所描述的特征相似。
