PRODUCTION OF ANDROGENETIC ZEBRAFISH (DANIO-RERIO)

To help investigate the evolutionary origin of the imprinting (parent- of-origin mono-allelic expression) of paternal genes observed in mamma ls, we constructed haploid and diploid androgenetic zebrafish (Danio r erio). Haploid androgenotes were produced by fertilizing eggs that had been X-ray irradiated to eliminate the maternal genome. Subsequent in hibition of the first mitotic division of haploid androgenotes by heat shock produced diploid androgenotes. The lack of inheritance of mater nal-specific DNA markers (RAPD and SSR) by putative diploid and haploi d androgenotes confirmed the androgenetic origin of their genomes. Mar ker analysis was performed on 18 putative androgenotes (five diploids and 13 haploids) from six families. None of 157 maternal-specific RAPD markers analyzed, some of which were apparently homozygous, were pass ed on to any of these putative androgenotes. A mean of 7.7 maternal-sp ecific markers were assessed per family. The survival of androgenetic zebrafish suggests that if paternal imprinting occurs in zebrafish, it does not result in essential genes being inactivated when their expre ssion is required for development. Production of haploid androgenotes can be used to determine the meiotic recombination rate in male zebraf ish. Androgenesis may also provide useful information about the mechan ism of sex determination in zebrafish.