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Abstract:
The epigenetic mechanism of genomic imprinting has been suggested to play an important role for the development of behavioral traits and speciation processes. One of the factors immensely influencing the speciation process is mate choice, as thereby certain alleles in a population are actively selected over others. Two paternally imprinted loci have been identified as candidate genes potentially influencing mate choice in allopatric mouse populations; one of them is the paternally expressed gene 13 (Peg13).
A previous study has shown that reproductive success was affected in Peg13 knockout (KO)
mutant mice, as they showed a shift in mate choice, very low breeding success and an
increased secondary loss of litters. In addition, many behavioral traits like anxiety, activity and curiosity were affected. Based on its expression throughout embryogenesis and
transregulatory effect on a large number of brain genes, Peg13 was proposed to play a role during development of several fundamental behaviors. Therefore, this thesis was designed to investigate the effects of Peg13 on prenatal and postnatal gene expression of a set of imprinted genes, sperm phenotype, as well as cognition by using Peg13 KO mutants of C57BL/6 mice.
Here, an in-depth gene expression analysis during embryogenesis from day 13 to 19 showed significant variation of Peg13 and all four genes in the imprinted cluster, especially during late neurogenesis. Postnatally, adolescent males showed highly elevated gene expression of the complete genetic cluster around Peg13 compared to females and earlier or later development, thereby pointing to a sex-specific role of these genes during sexual maturation. In a social preference test, initial preference of interaction partners was shifted in male KO
mutants to same-sex partners, while KO femalesshowed an even stronger preference towards males compared to wildtype (WT) females. This result was unexpected given the previous findings, however, time was found to be a key variable during behavioral, and especially mate choice experiments, as it severely affects the observed results. Mutant adult male mice experienced deficits in velocity and direction of sperm. While cognitive ability of female mutant mice in this study was not influenced, it remains to be studied whether male cognition is altered by Peg13.
