Mary Lynn Duckworth

Large fragment of the probasin promoter targets high levels of transgene expression to the prostate of transgenic mice

Androgen regulation and prostatic‐specific expression of targeted genes in transgenic mice can be controlled by a small DNA fragment of the probasin (PB) promoter (−426 +28 base pairs, bp). Although the small PB fragment was sufficient to direct prostate‐specific expression, the low levels of transgene expression suggested that important upstream regulatory sequences were missing.

Cellular localization of rat placental lactogen II and rat prolactin-like proteins A and B by in situ hybridization

In situ hybridizations using 35S-labelled antisense and sense RNA probes of rPLII, rPLP-A and rPLP-B were carried out on developing rat placenta to determine which cell types synthesized each specific mRNA. Cellular localization of the sites of synthesis of these placental RNAs would help to decide whether these proteins were functioning in the mother of the fetus. The cells of the basal zone are known to have access only to the maternal blood supply, while the labyrinth region is supplied by both maternal and fetal blood vessels. The data in this paper show that at day 12 of pregnancy the rPLII mRNA is synthesized in the primary and secondary giant cells. At later days, hybridization is seen in both the giant cells of the basal zone, and cells in the labyrinth, suggesting that rPLII has a function not only in the mother, but also in the fetus. The rPLP-A mRNA is synthesized in both the giant cells and the cytotrophoblasts of the basal zone. No hybridization is seen to any cells in the labyrinth, even at the later days when it appears that all cytotrophoblasts synthesize rPLP-A mRNA. The rPLP-B mRNA is synthesized exclusively by the cytophoblasts of the fetal placenta. Like rPLP-A, all these cells synthesize this mRNA in the late term placenta. The synthesis of the rPLP-A and rPLP-B mRNAs in cells which have access only to the maternal circulation suggest that they have a role in the mother.

FGF-16 is required for embryonic heart development.

Fibroblast growth factor 16 (FGF-16) expression has previously been detected in mouse heart at mid-gestation in the endocardium and epicardium, suggesting a role in embryonic heart development. More specifically, exogenously applied FGF-16 has been shown to stimulate growth of embryonic myocardial cells in tissue explants. We have generated mice lacking FGF-16 by targeting the Fgf16 locus on the X chromosome. Elimination of Fgf16 expression resulted in embryonic death as early as day 11.5 (E11.5). External abnormalities, including hemorrhage in the heart and ventral body region as well as facial defects, began to appear in null embryos from E11.5. Morphological analysis of FGF-16 null hearts revealed cardiac defects including chamber dilation, thinning of the atrial and ventricular walls, and poor trabeculation, which were visible at E10.5 and more pronounced at E11.5. These findings indicate FGF-16 is required for embryonic heart development in mid-gestation through its positive effect on myocardial growth.

Transgenic expression of human equilibrative nucleoside transporter 1 in mouse neurons

Transgenic mice that express human equilibrative nucleoside transporter subtype 1 (hENT1) under the control of a neuron‐specific enolase promoter have been generated. Southern blot and PCR revealed the presence of the transgene in five founder mice. Mice from each founder line were examined by reverse transcriptase (RT)‐PCR and found to express hENT1 in RNA isolated from whole brain, cerebral cortex, striatum, hippocampus, and cerebellum but not liver, kidney, heart, lung or skeletal muscle. Cortical synaptosomes prepared from transgenic mice had significantly increased [3H]adenosine uptake and [3H]nitrobenzylthioinosine binding, relative to samples from wild‐type mice. In behavioral tests, transgenic mice had altered responses to caffeine and ethanol, two drugs that inhibit and enhance, respectively, adenosine receptor activity. Caffeine‐induced locomotor stimulation was attenuated whereas the hypnotic effect of ethanol was enhanced in transgenic mice. Caffeine was more potent in inhibiting ethanol‐induced motor incoordination in wild‐type than in transgenic mice. No differences in expression of mouse genes for adenosine receptors, nucleoside transporters, or purine metabolizing enzymes were detected by RT‐PCR analyses. These data indicate that expression of hENT1 in neurons does not trigger adaptive changes in expression of adenosine‐related genes. Instead, hENT1 expression affects dynamic changes in endogenous adenosine levels, as revealed by altered behavioral responses to drugs that affect adenosine receptor signalling.

Differential Placental Hormone Gene Expression during Pregnancy in a Transgenic Mouse Containing the Human Growth Hormone/Chorionic Somatomammotropin Locus

The human (h) growth hormone/chorionic somatomammotropin (GH/CS) gene locus presents a unique model to gain insight into the molecular mechanisms that have allowed a closely related family of genes to be expressed in two distinct cell lineages/tissues: pituitary somatotrophs and placental syncytiotrophoblasts. However, studies of external factors that regulate gene expression have been somewhat limited by (i) a lack of human cell lines expressing endogenous GH or CS appropriately; and (ii) the fact that the GH/CS locus is unique to primates and thus does not exist in rodents. In the current study, a transgenic (171 h GH/CS-TG) mouse was generated containing the intact hGH/CS gene cluster and hGH locus control region (LCR) in a 171-kilobase DNA fragment. Pituitary and placental-specific expression of hGH/CS RNA was detected at embryonic day (E) 18.5. Immunostaining of hGH was seen in somatotrophs of the anterior pituitary beginning in late gestation. The presence of hCS protein was detected in the placental labyrinth in trophoblasts functionally analogous to the syncytiotrophoblast of the chorionic villi. This pattern of gene expression is consistent with the presence of essential components of the hGH/CS LCR. Transcript levels for hCS-A, hCS-B and placental hGH-variant increased in 171 hGH/CS-TG placenta during gestation (E11.5-E18.5), as previously observed in human placental development. Throughout gestation, hCS-A RNA levels were proportionately higher, accounting for 91% of total CS RNA by E18.5, comparable to term human placenta. Finally, the previous correlation between the transcription factor AP-2alpha and hCS RNA expression observed in developing primary human cytotrophoblast cultures, was extended to pregnancy in the 171 hGH/CS-TG mouse. The 171 hGH/CS-TG mouse thus provides a model to investigate hGH/CS gene expression, including in pregnancy.

Embryonic Survival and Severity of Cardiac and Craniofacial Defects Are Affected by Genetic Background in Fibroblast Growth Factor-16 Null Mice

Disruption of the X-chromosome fibroblast growth factor 16 (Fgf-16) gene, a member of the FGF-9 subfamily with FGF-20, was linked with an effect on cardiac development in two independent studies. However, poor trabeculation with lethality by embryonic day (E) 11.5 was associated with only one, involving maintenance in Black Swiss (Bsw) versus C57BL/6 mice. The aim of this study was to examine the potential influence of genetic background through breeding the null mutation onto an alternate (C57BL/6) background. After three generations, 25% of Fgf-16(-/Y) mice survived to adulthood, which could be reversed by reducing the contribution of the C57BL/6 genetic background by back crossing to another strain. There was no significant difference between FGF-9 and FGF-20 RNA levels in Fgf-16 null versus wild-type mice regardless of strain. However, FGF-8 RNA levels were reduced significantly in Bsw but not C57BL/6 mice. FGF-8 is linked to anterior heart development and like the FGF-9 subfamily is reportedly expressed at E10.5. Like FGF-16, neuregulin as well as signaling via ErbB2 and ErbB4 receptors have been linked to trabeculae formation and cardiac development around E10.5. Basal neuregulin, ErbB2, and ErbB4 as well as FGF-8, FGF-9, and FGF-16 RNA levels varied in Bsw versus C57BL/6 mice. These data are consistent with the ability of genetic background to modify the phenotype and affect embryonic survival in Fgf-16 null mice.

Molecular Genetics and Biology of the Rat Placental Prolactin Family

The prolactin (PRL) family of hormones plays a key role in the establishment and maintenance of pregnancy in the rat. Astwood and Greep (1) demonstrated that the hypophysectomy of a pregnant rat before day 12 of gestation resulted in abortion. After midterm the outcome of pregnancy was unaffected, suggesting that pituitary hormones were essential in the earlier stages, but that placental proteins were able to take over their roles after that time. Early in pregnancy, PRL is the hormone that is responsible for transforming the corpus luteum of the cycle to the corpus luteum of pregnancy (2, 3). Beginning by day 2 after mating, PRL is secreted as diurnal and nocturnal surges (4, 5). These surges decline at midpregnancy: first the diurnal surge at day 8, then the nocturnal surge by day 10. It has been speculated that not only might placental proteins replace the functions of PRL in the pregnant rat, but that they also could have a role in regulating the decline in these surges (7–9). This switch, from the mother to the developing fetuses, in the synthesis of proteins important to the successful outcome of pregnancy means that their times and locations of synthesis, as well as their quantities, are directly related to the presence of the fetuses. This may allow more precise control of the expression of these proteins during the specific times in pregnancy when they are needed.

A standardized nomenclature for the mouse and rat prolactin superfamilies

Institute of Maternal-Fetal Biology, University of Kansas Medical Center, Kansas City, Kansas, 66160, USA Department of Physiology, University of Manitoba, R3E 3J7, Winnipeg, Manitoba, Canada Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio, 45267, USA Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois, 60208, USA Mouse Genome Informatics Resource and Mouse Genomic Nomenclature Committee, The Jackson Laboratory, Bar Harbor, Maine, 04609, USA Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa, 50011, USA Department of Cellular Biochemistry, Veterinary Medical Sciences/Animal Resource Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku Tokyo, Japan Rat Genome Database, Medical College of Wisconsin, Milwaukee, Wisconsin, 53226, USA Biochemistry Department, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, UK

The Placental Lactogen Gene Family: Structure and Regulation

The placenta has been recognized as a major endocrine gland for well over half a century. Its repertoire of secretory products includes both steroids, proteins, and peptides, several of which are secreted in large amounts. Another notable feature of placental endocrinology is the great species variation of specific hormones and pattern of hormones secreted. This feature makes studies of placental endocrinology more fascinating as well as more complex and challenging. Excellent reviews on placental endocrinology should be consulted for a more detailed account of the subject (Forsyth, 1974; Blank et al., 1977; Talamantes et al., 1980).

Placental Lactogen/Growth Hormone Gene Family

Before focusing on selective aspects of current research on placental lactogens (PLs), it is useful to look at advances in this area from a historical perspective. Several landmark studies can be recognized that were instrumental in providing new directions to the field (Table 11.1). Four major periods, each ushered in by the applications of new technologies or methods, can readily be identified, underscoring the importance of technology to scientific advance.