EAGER: Testing the Roles of Zygotic Selection and Sperm Competition in Transmission Bias in Astyanax

人们普遍认为，精子的特性是由产生精子的男性的二倍体基因决定的。然而，最近意想不到的发现表明，精子细胞的表型也可能受到其自身基因的影响。这一创新项目考察了精子细胞的单倍体基因类型对其个体特征的影响程度，以及受精后精子竞争和选择在导致等位基因从一代传递到下一代的偏见方面的相对重要性。它将提供基本信息，以阐明进化中自然选择的一条以前不曾被怀疑但可能很重要的途径。预期的结果有可能开辟精子生物学研究的一条重要的新路线。它们有望在发育生物学、进化生物学以及改进人类和家畜的报告技术方面具有广泛的意义。本研究调查了在两个早期淡水鱼物种(Astianax spp.)杂交中观察到的基因之间的上位性相互作用。之前的研究表明，来自杂交雄性的精子传递来自非连锁基因的有偏见的等位基因子集和等位基因组合。这一观察表明，假设单个精子的表型(在这种情况下，受精效率)由他们各自的基因决定，即包裹被送到的概率取决于它包含的东西。与这一假设一致的是，初步研究表明，精子亚群--由游泳能力的差异或对化学挑战的反应--在等位基因含量上存在显著差异。这项研究测试了观察到的传播偏差是否确实是由精子竞争引起的，或者是否有受精后合子选择的贡献。单个精子将通过胞浆内单精子注射形成的胚胎进行基因分型。这将允许对不同的精子亚群(例如，游泳速度慢的人和快的人)的等位基因含量进行比较。此外，杂交X非杂交个体的后代将进行基因分型，以便检测传播偏见。该假说预测，偏见将仅限于来自杂交男性的家庭，而不是来自杂交女性的家庭。

It has been accepted that the characteristics of sperm are determined by the diploid genotype of the male producing them. However, recent and unexpected findings indicate that the phenotype of a sperm cell may also be influenced by its own genotype. This innovative project examines the degree to which the haploid genotypes of sperm cells affect their individual characteristics and the relative importance of sperm competition versus selection post-fertilization in causing biases in transmission of alleles from one generation to the next. It will provide basic information to illuminate a previously unsuspected but potentially important avenue for natural selection in evolution. The expected results have the potential to open up an important new line of research in sperm biology. They are expected to have broad implications in developmental biology, evolutionary biology, and for improvements in reporductive technologies in humans and domestic animals.This research investigates the epistatic interactions among genes observable in hybrids between two incipient species of freshwater fish (Astyanax spp.). Previous work has shown that sperm from hybrid males pass along biased subsets of alleles and allelic combinations derived from unlinked genes. This observation suggested the hypothesis that the phenotypes of individual sperm (in this case fertilization efficiency) are determined by their individual genotypes, i.e., the probability that a package gets delivered depends upon what it contains. Consistent with this hypothesis are preliminary studies that show that sperm subpopulations - defined by differences in swimming ability or by their response to a chemical challenge - differ significantly in allelic content. This research tests whether the observed transmission biases are indeed caused by sperm competition or whether there is a contribution from zygotic selection, post fertilization. Single sperm will be genotyped from embryos formed using intracytoplasmic sperm injection. This will allow different sub-populations of sperm (e.g. slow versus fast swimmers) to be compared for allelic content. Additionally, the offspring of hybrid X non-hybrid individuals will be genotyped, allowing for the detection of transmission biases. The hypothesis predicts that biases will be restricted to families derived from hybrid males but not from hybrid females.