Laboratory of Experimental Reproductive Endocrinology
Head of Laboratory: Professor Ilpo Huhtaniemi
AIMS
- To elucidate molecular mechanisms of endocrine regulation of male and female reproductive functions using molecular biological,
endocrinological, genetic and physiological methods - To elucidate the mechanisms of action of gonadotrophins and other hormones acting through G protein coupled receptors (GPCR) in reproductive organs
- To address the influence of the above hormonal functions on obesity, ageing, hormone-dependent cancer and environmental effects on reproduction
PREVIOUS AND CURRENT RESEARCH
The main emphasis of our research has been in elucidation of the role of the two gonadotrophic hormones, luteinising hormone (LH) and follicle-stimulating hormone (FSH) in the regulation of human reproductive function. In addition, the role of these hormonal function in endocrine cancer, ageing and intetaractions with environmental effects (e.g. endocrine disrupting chemicals) has been addressed. We have studied mutations and polymorphisms in the genes of gonadotrophins and gonadotrophin receptors, and developed genetically modified mice to address further details and mechanisms of the phenotypic effects of such mutations.
In addition to female reproduction, we have had sustained interest in developmental aspects of reproductive functions and in endocrine aspects of male reproductive health (andrology).
Besides standard molecular and cell biological techniques we produce genetically modified (transgenic and knockout) mice, do hormone measurements, and study gene function and hormonal signaling in cell culture experiments.
Some of our recent key findings include:
- Discovery of a common genetic variant of human LH (Pettersson et al: J Clin Endocrinol Metab 1992; 74: 164)
- Discovery of the first inactivating mutation in the human FSH receptor gene (Aittomäki et al: Cell 1995; 82:959)
- Production of a transgenic mouse developing multiple types of tumours in gonads and adrenal gland (Kananen et al: Mol Endocrinol 1995; 9: 616)
- Production of the LH receptor knockout mouse (Zhang et al. Mol Endocrinol 2001: 18: 182)
- Production of a choriongonadotrophin overexpressing transgenic mouse, producing multiple endocrine tumours in gonads, pituitary, adrenal and mammary gland (Rulli et al. Endocrinology 2002: 143: 4085)
The head of the laboratory is also the Director of an Academy of Finland Centre of Excellence “Research Programme on Male Reproductive Health” at Department of Physiology, University of Turku, Finland (http://research.utu.fi/mrh/index.htm), and there is close scientific collaboration between the London and Turku laboratories.
FUTURE RESEARCH PLANS
Genetic basis of LH dependent obesity and adrenal tumorigenesis in mice
Certain strains of mice develop adrenal hyperplasia and tumours after gonadectomy. The phenotype is associated with ectopic LH receptor expression in the adrenal gland. Being clearly strain specific it must have a genetic basis. The purpose of this project is to identify, by using mouse genetics approaches, the quantitative trait loci (QTLs) and finally the discrete gene(s) that are responsible for the induction of adrenocortical LH receptor expression, adrenal hyperfunction and tumorigenesis. More generally, the findings are expected to elucidate the regulation of expression of the LH receptor, a key player in the maintenance of normal development and functions of the ovary and testis.
Mouse models for activating gonadotrophin receptor mutations
Both activating and inactivating mutations have been detected in human gonadotrophin receptor genes. Knockout mice have provided good phenocopies of the inactivating human mutations and numerous important details of the inactivation mechanisms have been elucidated by the mouse models. The mechanisms of activating human mutations are less clearly understood. There is no female phenotype with activating LHR mutations, and no clear-cut activating mutations have been found in FSHR. To predict the phenotypes of such mutations in humans, our aim is to produce, using knock-in techniques, mouse models for activating LHR and FSHR mutations.
Dissecting the different signaling systems of gonadotrophin action
Besides the classical cAMP mediated signaling, it has became apparent that gonadotrophin actions are also mediated through alternative signaling cascades, such as phospholipase C/protein kinase C and MAP kinase. The physiological function of the alternative signaling systems is not known, although it is suggested that the steroidogenic and grow-stimulating effects of LH and FSH might use different second messengers. To explore the roles of the different seconds messenger systems, we are constructing tethered fusion proteins of gonadotrophin receptors and specific G proteins, transfecting them into cells in vitro and making transgenic animal models. In this way we expect that we can dissect out specific functional effects of the different signaling cascades activated by gonadotrophin stimulation of target tissues.
In vitro bioassay of androgens in human peripheral serum and biological samples
In the clinical diagnostics of androgen excess in women (polycystic ovary syndrome, hirsutism), usually measurements of serum testosterone levels are used, but these levels have often poor correlation with the clinical picture. Likewise, the ageing-related decrease of immunoassayable testosterone in men has poor correlation with apparent symptoms of hypogonadism. Hence, levels of immunoreactivity of selected androgens may not completely reflect the total androgenic activity present in a biological sample. We have therefore developed an in vitro bioassay of serum total androgenic activity, using a recombinant cell line expressing human androgen receptor (AR) and AR dependent reporter gene. The assay measures total androgenic bioactivity in biological samples, and it can also be modified for assessment of antiandrogenic activity. The assay is suitable for clinical diagnostics and for research tool to assess androgen bioactivity in peripheral serum, other biological samples and to monitor androgenic and antiandrogenic activity of environmental samples and potential endocrine disruptors.
Biology of novel membrane receptors for progesterone
The membrane receptor for progesterone was recently cloned and surprisingly, it turned out to have a 7-transmembrane GPCR structure. In fact, there are 3 subtypes of this receptor, a,b and g, each with distinct tissue specificity of expression. We are studying the functions of these new receptors by exploring their expression in different tissues of the human and rodent reproductive tract, elucidating their signal transduction mechanisms and attempting to produce knockout mouse models for the receptors.
Role or epididymis in the regulation of sperm maturation
The epididymis plays an important role in the maturation of sperms and their acquisition of fertilising capacity. This organ is therefore a promising target for novel strategies of male contraception. The purpose of this project is to identify novel epididymis-specific genes and study their role in the process of sperm maturation, using genetically modified mice as experimental models.
In vitro and in vivo screening of endocrine disrupting chemicals
We are participating in several EU consortia working on biology and screening of endocrcine disrupting chemicals. These include:
- Multiorganic risk assessment of endocrine disrupters (EuRiskED)
- Development of a novel approach in hazard and risk assessment of reproductive toxicity by a combination and application of in vitro, tissue and sensor technologies (ReProTect)
- Puberty onset – influence of nutritional, environmental and endogenous regulators (PIONEER)
SELECTED PUBLICATIONS
1. Aittomäki K., Dieguez Lucena J.L., Pakarinen P., Sistonen P., Tapanainen J., Gromoll J., Kaskikari R., Sankila E.-M., Lehväslaiho H., Reyes Engel A., Nieschlag E., Huhtaniemi I. and de la Chapelle A. (1995) Mutation in the follicle-stimulating hormone receptor gene causes hereditary hypergonadotropic ovarian failure. Cell 82, 959-968.
2. Tapanainen J.S., Aittomäki K., Jiang M., Vaskivuo T. and Huhtaniemi I.T. (1997) Men homozygous for an inactivating mutation of the follicle-stimulating hormone (FSH) receptor gene present variable suppression of spermatogenesis and fertility. Nature Genet 15, 205-206.
3. Manna P.R., Tena-Sempere M. and Huhtaniemi I.T. (1999) Molecular mechanisms of thyroid hormone-stimulated steroidogenesis in mouse Leydig tumor cells; Involvement of the steroidogenic acute regulatory (StAR) protein. J Biol Chem 274, 5909-5918.
4. Jiang M., Pakarinen P., Zhang F.-P., El-Hefnawy T., Koskimies P., Pettersson K. and Huhtaniemi I. (1999) A common polymorphic allele of the human luteinizing hormone beta-subunit gene: additional mutations and differential function of the promoter sequence. Hum Mol Genet 8, 2037-2046.
5. Kero J., Poutanen M., Zhang F.-P., Rahman N., McNicol A.-M., Nilson J., Keri R. and Huhtaniemi I. (2000) Elevated luteinizing hormone (LH) in transgenic mice induces functional LH receptor expression and steroidogenesis in adrenal cortex. J Clin Invest 105, 633-641.
6. Themmen A.P.N. and Huhtaniemi I.T. (2000) Mutations of gonadotropins and gonadotropin receptors: Elucidating the physiology and pathophysiology of pituitary-gonadal function. Endocr Rev 21, 551-583.
7. Zhang F.-P., Poutanen M., Wilbertz J. and Huhtaniemi I. (2001) Normal prenatal but arrested postnatal sexual development of luteinizing hormone receptor knockout mice. Mol Endocrinol 18, 182-193.
8. Manna P.R., Joshi L., Reinhold V.N., Aubert M.L., Suganuma N., Pettersson K. and Huhtaniemi I. (2002) Synthesis, purification, and structural and functional characterization of recombinant form of a common genetic variant of human luteinizing hormone. Hum Mol Genet 11, 301-315.
9. Zhang F.-P., Pakarainen T., Poutanen M., Toppari J. and Huhtaniemi I. (2003) The low gonadotropin-independent constitutive production of testicular testosterone is sufficient to maintain spermatogenesis. Proc Natl Acad Sci USA 100, 13692-13697.
10. Rahman N. A., Kiiveri S., Rivero-Müller A., Levallet J., Vierre S., Kero J., Wilson D.B., Heikinheimo M.T. and Huhtaniemi I.T. (2004) Adrenocortical tumorigenesis in transgenic mice expressing the inhibin a-subunit promoter/SV40 virus T-antigen transgene: Relationship between ectopic expression. Mol Endocrinol 18, 2553-2569.
RESEARCH OPPORTUNITIES
From time to time, there are opportunities for new postdoctoral researchers or PhD students to work on any of the above projects.
