Kyriakou Eleni, Zouros Eleftherios, Rodakis George C
Department of Biochemistry and Molecular Biology, National and Kapodistrian University of Athens, Panepistimioupolis, 15701 Athens, Greece.
BMC Res Notes. 2010 Aug 6;3:222. doi: 10.1186/1756-0500-3-222.
In animals mtDNA inheritance is maternal except in certain molluscan bivalve species which have a paternally inherited mitochondrial genome (genome M) along with the standard maternal one (genome F). Normally, the paternal genome occurs in the male gonad, but it can be often found, as a minority, in somatic tissues of males and females. This may happen in two ways. One is through "sperm mtDNA leakage" into somatic tissues, a deviation from the normal situation in which the sperm mtDNA vanishes in females or ends up exclusively in the germ line of males. The other is through "egg heteroplasmy", when the egg contains, in small quantities, the paternal genome in addition to maternal genome.
To test the two hypotheses, we compared the sequences of one of the most variable domains of the M molecule in a somatic tissue (foot) and in the sperm of ten male and in the foot of ten female individuals of M. galloprovincialis. Presence of the M genome was rarer in the foot of females than males. The M genome in the sperm and in the foot of males was identical.
Given that the surveyed region differs from individual to individual, the identity of the M genome in the foot and the sperm of males supports strongly the hypothesis that, at least for the tissue examined, the presence of the M genome is due to sperm mtDNA leakage.
在动物中，线粒体DNA（mtDNA）的遗传是母系遗传，除了某些双壳贝类软体动物，它们除了有标准的母系线粒体基因组（F基因组）外，还有父系遗传的线粒体基因组（M基因组）。通常，父系基因组存在于雄性性腺中，但在雄性和雌性的体细胞组织中也经常能少量发现。这可能通过两种方式发生。一种是通过“精子mtDNA泄漏”进入体细胞组织，这是一种偏离正常情况的现象，正常情况下精子mtDNA在雌性体内消失或仅存在于雄性生殖系中。另一种是通过“卵子异质性”，即卵子除了含有母系基因组外，还少量含有父系基因组。
为了验证这两种假设，我们比较了地中海贻贝10只雄性个体的体细胞组织（足部）和精子以及10只雌性个体的足部中M分子最可变区域之一的序列。雌性足部中M基因组的存在比雄性中更罕见。精子和雄性足部中的M基因组是相同的。
鉴于所调查的区域因个体而异，雄性足部和精子中M基因组的一致性有力地支持了这样一种假设，即至少在所检查的组织中，M基因组的存在是由于精子mtDNA泄漏。
