The mariner transposable element is capable of interplasmid transposition in the embryonic soma of the yellow fever mosquito, Aedes aegypti. To determine if this demonstrated mobility could be utilized to genetically transform the mosquito, a modified mariner element marked with a wild-type allele of the Drosophila melanogaster cinnabar gene was microinjected into embryos of a kynurenine hydroxylasedeficient, white-eyed recipient strain. Three of 69 fertile male founders resulting from the microinjected embryos produced families with colored-eyed progeny individuals, a transformation rate of 4%. The transgene-mediated complementation of eye color was observed to segregate in a Mendelian manner, although one insertion segregates with the recessive allele (female-determining) of the sex-determining locus, and a separate insertion is homozygous lethal. Molecular analysis of selected transformed families demonstrated that a single complete copy of the construct had integrated independently in each case and that it had done so in a transposase-mediated manner. The availability of a mariner transformation system greatly enhances our ability to study and manipulate this important vector species.The incidence of vector-borne diseases is on the rise. As part of a multifaceted effort to control the transmission of diseases, we are developing tools for the molecular genetic manipulation of mosquitoes (1). We intend to use the tools and techniques of modern molecular biology to generate strains of mosquitoes that are incapable of transmitting a specific pathogen. These strains will be used selectively in release programs to reduce disease transmission. One of the key requirements for this effort is a method for introducing genes into mosquitoes. Recently, the Hermes transposable element from the housefly, Musca domestica, was shown to integrate into the germ line of the yellow fever mosquito, Aedes aegypti (2). The identification of Hermes as a viable candidate for mosquito transgenesis resulted from a strategy that first evaluated the ability of the element to mobilize (excise and insert) in the embryonic soma of the mosquito (3), followed by demonstration that it would integrate into the germ line (2). By using this approach, we show that a modified mariner transposable element efficiently and stably integrates into the germ line of Ae. aegypti.Transposition assays based on the mobilization of a marked transposon from a donor to a target plasmid (4) were used to show that the mariner element, Mos1, from Drosophila mauritiana (5), was capable of mobility in embryos of Ae. aegypti. Subsequently, a genetic transformation experiment showed that Mos1 could integrate into the germ line of the mosquito. This experiment exploited the recently demonstrated ability of a wild-type copy of the Drosophila melanogaster cinnabar (cn ϩ ) gene to complement the white-eye phenotype of the kynurenine hydroxylase-white (kh w ) strain of Ae. aegypti (6-8). We report the successful generation of transgenic Ae. aegypti lines that contai...

Embryonic testis development requires the morphogenesis of cords and growth of all cell populations to allow organ formation. It is anticipated that coordination of the growth and differentiation of various cell types involves locally produced growth factors. The current study was an investigation of the hypothesis that transforming growth factor-alpha (TGF-alpha) is involved in regulating embryonic testis growth. TGF-alpha has previously been shown to function in the postnatal testis. TGF-alpha and other members of the epidermal growth factor (EGF) family act through the epidermal growth factor receptor (EGFR) to stimulate cell proliferation and tissue morphogenesis. To understand the potential actions of TGF-alpha in the embryonic testis, general cell proliferation was investigated. Characterization of cell proliferation in the rat testis throughout embryonic and postnatal development indicated that each cell type has a distinct pattern of proliferation. Germ cell growth was transiently suppressed around birth. Interstitial cell growth was high embryonically and decreased to low levels around birth. A low level of Sertoli cell proliferation was observed at the onset of testis cord formation. Sertoli cell proliferation in early embryonic development was low; the levels were high later in embryonic development and remained high until the onset of puberty. Both TGF-alpha and the EGFR were shown to be expressed in the embryonic and postnatal rat and mouse testis. Perturbation of TGF-alpha function using neutralizing antibodies to TGF-alpha on testis organ cultures dramatically inhibited the growth of both embryonic and neonatal testis. TGF-alpha antibodies had no effect on cord formation. The TGF-alpha antibody was found to be specific for TGF-alpha in Western blots when compared to EGF and heregulin. Testis growth was also inhibited by perturbation of EGFR signaling using an EGFR kinase inhibitor. Therefore, TGF-alpha appears to influence embryonic testis growth but not morphogenesis (i.e., cord formation). Treatment of embryonic testis organ cultures with exogenous TGF-alpha also perturbed development, leading to an increased proliferation of unorganized cells. Testis from EGFR and TGF-alpha knockout mice were analyzed for testis morphology. TGF-alpha knockout mice had no alterations in testis phenotype, while EGFR knockout mice had a transient decrease in the relative amount of interstitial cells before birth. Observations suggest that there may be alternate or compensatory factors that allow testis growth to occur in the apparent absence of TGF-alpha actions in the mutant mice. In summary, the results obtained suggest that TGF-alpha is an important factor in the regulation of embryonic testis growth, but other factors will also be involved in the process.

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