References

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Trophic Factors for Gonadotropes and Thyrotropes

Although not a transgenic model, the hpg mouse is particularly relevant to this topic. These mice harbor a spontaneous deletion of at least 33.5 kb (96) from chromosome 14 (97) removing the distal portion of the gene encoding a biosynthetic precursor of both gonadotropin-releasing hormone (GnRH) and GnRH-associated peptide (GAP) (96). Although the mice are capable of expressing mRNA from the truncated gene, no synthesis of GnRH or GAP occurs. Following the loss of this hypothalamic trophic...

Igf2 And Igf2 Receptor

Igf2 was the first member of the insulin Igf family to be knocked out, now almost a decade ago (31). This experiment revealed that murine Igf2 expression is subject to genomic imprinting, and that gene is expressed from the paternal allele. As a result, deletion of the paternal allele results in dwarfism, while deletion of the maternal allele has no apparent effect (31,32). Igf2 p- + and - - are indistinguishable, and dwarfism is apparent shortly after placentation (31,32). These mice are...

Antral Follicle Development Sensitivity To Extra Ovarian And Intra Ovarian Regulation

During follicular development in mice, follicular antrum formation represents a transition from primarily intrafollicular regulation to a combination of intraovarian and extraovarian regulation. Follicles enter a rapid period of growth, and synthesize peptide and steroid hormones that impact on the reproductive axis. Multiple positive and negative feedback loops between the hypothalamus, pituitary, and ovaries coordinate follicle maturation with sexual behavior and physiological preparation for...

Role Of Kit Ligand In Female Gametogenesis

In female embryos, once PGCs have entered the fetal ovary, they complete mitotic divisions and enter meiosis. They eventually arrest meiosis at Prophase I, and each germ cell will become invested by a layer of flattened somatic cells that are the precursors of the follicle or granulosa cells. Therefore, in the ovary, just as in the testis, germ-cell survival, growth, and differentiation is controlled by the complex interaction between the germ cells and the surrounding somatic cells (62,63)...

StAr Knockout Mice

As shown in Fig. 1, one essential step in steroidogenesis is the translocation of cholesterol from the cytoplasm to the inner mitochondrial membrane, where the cholesterol side-chain cleavage enzyme (P450scc) catalyzes the first committed reactions in steroidogenesis. The steroidogenic acute regulatory protein (StAR), a 30-kDa mitochondrial phosphoprotein, was initially isolated because its expression within steroidogenic cells was rapidly induced by trophic hormones (3). These findings...

Inhibin Activin And Follistatin Deficiency Or Overexpression

While GnRH pulsatility provides one mechanism for differential FSH and LH regulation, other factors are clearly involved. A myriad of in vivo and in vitro studies clearly indicate a role for activins, inhibins, and follistatins in the selective regulation of FSH (3). As their names suggest, activins stimulate, while inhibins attenuate FSH synthesis and secretion. Both activins and inhibins are members of the transforming growth factor-p (TGFP) protein family. Activins are comprised of two...

Toxigenic Ablation Of Melanotrophs And Corticotrophs

Ablation of selected cell populations in transgenic mice using a targeted toxigenic protein has been useful in cell-lineage studies and physiological studies of tissue function within a complex biological environment 58-61 . The two most commonly used toxins have been diptheria toxin A chain DTA and herpes simplex virus type 1 thymidine kinase HSV1-TK , although both have limitations. HSV-TK has the advantage of temporal control, because its toxicity in most mammalian cells is dependent on...