M. Ram Sairam

Bio: M. Ram Sairam is an academic researcher from Université de Montréal. The author has contributed to research in topics: Follicle-stimulating hormone receptor & Follicle-stimulating hormone. The author has an hindex of 25, co-authored 45 publications receiving 2517 citations. Previous affiliations of M. Ram Sairam include McGill University.

Impairing follicle-stimulating hormone (FSH) signaling in vivo: Targeted disruption of the FSH receptor leads to aberrant gametogenesis and hormonal imbalance

Abstract: Pituitary gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone stimulate the gonads by regulating germ cell proliferation and differentiation. FSH receptors (FSH-Rs) are localized to testicular Sertoli cells and ovarian granulosa cells and are coupled to activation of the adenylyl cyclase and other signaling pathways. Activation of FSH-Rs is considered essential for folliculogenesis in the female and spermatogenesis in the male. We have generated mice lacking FSH-R by homologous recombination. FSH-R-deficient males are fertile but display small testes and partial spermatogenic failure. Thus, although FSH signaling is not essential for initiating spermatogenesis, it appears to be required for adequate viability and motility of the sperms. FSH-R-deficient females display thin uteri and small ovaries and are sterile because of a block in folliculogenesis before antral follicle formation. Although the expression of marker genes is only moderately altered in FSH-R −/− mice, drastic sex-specific changes are observed in the levels of various hormones. The anterior lobe of the pituitary gland in females is enlarged and reveals a larger number of FSH- and thyroid-stimulating hormone (TSH)-positive cells. The phenotype of FSH-R −/− mice is reminiscent of human hypergonadotropic ovarian dysgenesis and infertility.

Estrogen deficiency, obesity, and skeletal abnormalities in follicle-stimulating hormone receptor knockout (FORKO) female mice.

Abstract: Targeted disruption of the receptor for glycoprotein hormone, FSH (FSH-R) causes a gene dose-related endocrine and gametogenic abnormality in female mice. The resulting FSH-R knockout (FORKO) mutants have disordered estrous cycles, ovulatory defects, and atrophic uterus. The heterozygous animals that initially show reduced fertility undergo early reproductive senescence and stop breeding altogether. Lack of FSH-R signaling in females causes severe ovarian underdevelopment producing chronic estrogen deficiency. This was accompanied by increases in serum testosterone levels. Ovarian aromatase gene transcription and translation are unaltered in the mutants. Early loss of estrogen in the null mutants leads to obesity and skeletal abnormalities that intensify with age producing (kyphosis), a hunchback appearance. Both these changes also become apparent in older heterozygous mice coincident with early reproductive senescence. The expression of nuclear estrogen receptor(s) a and b genes and the corresponding proteins in the ovary and uterus of FORKO mice appear to be intact. The loss of ovarian estrogen creates an imbalance in A and B forms of the progesterone receptor in the uterus of both heterozygotes and null mutants. Some of the changes we have documented here in FORKO mice are reminiscent of the ovarian dysfunction and other major symptoms that are usually associated with estrogen deficiency. In null mutants, estradiol-17b administration promptly induced uterine growth and reversed the accumulation of adipose tissue indicating that estrogen receptors are functional. Thus, the phenotypes evident in these genetically altered FSH-R mutants may provide an experimental system to explore the effects of estrogenic compounds on different targets including the ovary in a nonsurgical setting. (Endocrinology 141: 4295‐ 4308, 2000)

Qualitative and Quantitative Decline in Spermatogenesis of the Follicle-Stimulating Hormone Receptor Knockout (FORKO) Mouse

Abstract: Sertoli cells express functional receptors for FSH, one of the two pituitary hormones that regulate spermatogenesis in mammals. We recently produced genetic mutant (FORKO) mice that lack FSH receptor, in order to examine the effects on testicular function and fertility. Mutant males exhibited weight loss of testis, epididymis, and seminal vesicle as well as low levels of testosterone. Except for reduced seminiferous tubular diameter, no gross changes were apparent upon histological examination. Analysis of testicular germ cells by flow cytometry revealed a significant increase in the percentage of 2C cells (spermatogonia and non-germ cells) and a significant decrease in the percentage of HC cells (elongated spermatids) of FORKO males. The absolute number of homogenization-resistant elongated spermatids was also significantly reduced in the mutant males. A 2-fold increase in c-kit-positive 2C cells was recorded in the mutant males. Elongated spermatids of FORKO males showed a dramatic increase in propidium iodide binding suggesting reduced nuclear compaction. The increase in size of the sperm head in mutants, as well as susceptibility to dithiothreitol-induced decondensation, suggests the inadequate condensation of sperm chromatin. Sperm chromatin structure assay, a technique that reflects DNA stability, revealed that sperm from FORKO males are susceptible to acid denaturation, indicating the poor quality of sperm. These data allow us to conclude that genetic disruption of FSH receptor signaling in the rodent induces major changes that might contribute to reduced fertility.

Ovarian pathology and high incidence of sex cord tumors in follitropin receptor knockout (FORKO) mice.

Abstract: In this investigation we describe our observations of the status of the aging ovary in mice with disruption of the receptor for FSH. Knockout mice at 3–5 months of age are acyclic and sterile, with very small, underdeveloped ovaries. Thus, they exhibit hypergonadotropic-hypogonadism with high levels of circulating FSH similar to the postmenopausal state in women. By 12 months more than 92% of these animals developed various kinds of ovarian pathology, including neoplasms of sex cord-stromal type as well as cysts. Interestingly, the majority of tumors were located in the right ovary, with the contralateral ovary remaining unaffected but atrophic. The ovary from heterozygotes also showed pathology after 15 months. None of the age-matched wild-type mice that remained fertile developed any sign of ovarian tumors. Circulating LH and FSH levels were increased in follitropin receptor knockout mice and remained severalfold higher in tumor-bearing animals. The histological appearances of ovarian tumors were simila...

Estrogen receptor null mice: what have we learned and where will they lead us?

Abstract: All scientific investigations begin with distinct objectives: first is the hypothesis upon which studies are undertaken to disprove, and second is the overall aim of obtaining further information, from which future and more precise hypotheses may be drawn Studies focusing on the generation and use of gene-targeted animal models also apply these goals and may be loosely categorized into sequential phases that become apparent as the use of the model progresses Initial studies of knockout models often focus on the plausibility of the model based on prior knowledge and whether the generation of an animal lacking the particular gene will prove lethal or not Upon the successful generation of a knockout, confirmatory studies are undertaken to corroborate previously established hypotheses of the function of the disrupted gene product As these studies continue, observations of unpredicted phenotypes or, more likely, the lack of a phenotype that was expected based on models put forth from past investigations are noted Often the surprising phenotype is due to the loss of a gene product that is downstream from the functions of the disrupted gene, whereas the lack of an expected phenotype may be due to compensatory roles filled by alternate mechanisms As the descriptive studies of the knockout continue, use of the model is often shifted to the role as a unique research reagent, to be used in studies that 1) were not previously possible in a wild-type model; 2) aimed at finding related proteins or pathways whose existence or functions were previously masked; or 3) the subsequent effects of the gene disruption on related physiological and biochemical systems The alpha ERKO mice continue to satisfy the confirmatory role of a knockout quite well As summarized in Table 4, the phenotypes observed in the alpha ERKO due to estrogen insensitivity have definitively illustrated several roles that were previously believed to be dependent on functional ER alpha, including 1) the proliferative and differentiative actions critical to the function of the adult female reproductive tract and mammary gland; 2) as an obligatory component in growth factor signaling in the uterus and mammary gland; 3) as the principal steroid involved in negative regulation of gonadotropin gene transcription and LH levels in the hypothalamic-pituitary axis; 4) as a positive regulator of PR expression in several tissues; 5) in the positive regulation of PRL synthesis and secretion from the pituitary; 6) as a promotional factor in oncogene-induced mammary neoplasia; and 7) as a crucial component in the differentiation and activation of several behaviors in both the female and male The list of unpredictable phenotypes in the alpha ERKO must begin with the observation that generation of an animal lacking a functional ER alpha gene was successful and produced animals of both sexes that exhibit a life span comparable to wild-type The successful generation of beta ERKO mice suggests that this receptor is also not essential to survival and was most likely not a compensatory factor in the survival of the alpha ERKO In support of this is our recent successful generation of double knockout, or alpha beta ERKO mice of both sexes The precise defects in certain components of male reproduction, including the production of abnormal sperm and the loss of intromission and ejaculatory responses that were observed in the alpha ERKO, were quite surprising In turn, certain estrogen pathways in the alpha ERKO female appear intact or unaffected, such as the ability of the uterus to successfully exhibit a progesterone-induced decidualization response, and the possible maintenance of an LH surge system in the hypothalamus [ABSTRACT TRUNCATED]

Initial and cyclic recruitment of ovarian follicles.

Abstract: Mammalian ovaries consist of follicles as basic functional units. The total number of ovarian follicles is determined early in life, and the depletion of this pool leads to reproductive senescence. Each follicle develops to either ovulate or, more likely, to undergo degeneration. The dynamics of ovarian follicle development have interested endocrinologists and developmental biologists for many years. With the advent of assisted reproductive techniques in humans, the possibility of regulating follicle development in vivo and in vitro has gained clinical relevance. In this review, we focus upon key branching points during the development of ovarian follicles as well as factors involved in determining the eventual destiny of individual follicles. We discuss inconsistencies in the literature regarding the definitions of follicle recruitment and selection and propose to name the two major steps of follicle development as initial and cyclic recruitment, respectively. Because some of these disparities have arisen due to differences in the animal systems studied, we also compare the development of the ovarian follicles of both humans and rats. We also review the status of knowledge of several puzzling clinical issues that may provide important clues toward unlocking the mechanisms of follicle development.

The human obesity gene map: the 2005 update.

Abstract: This paper presents the 12th update of the human obesity gene map, which incorporates published results up to the end of October 2005. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTL) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2005, 176 human obesity cases due to single-gene mutations in 11 different genes have been reported, 50 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 244 genes that, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 408. The number of human obesity QTLs derived from genome scans continues to grow, and we now have 253 QTLs for obesity-related phenotypes from 61 genome-wide scans. A total of 52 genomic regions harbor QTLs supported by two or more studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably, with 426 findings of positive associations with 127 candidate genes. A promising observation is that 22 genes are each supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. The electronic version of the map with links to useful publications and relevant sites can be found at http://obesitygene.pbrc.edu.

Effect of single and compound knockouts of estrogen receptors alpha (ERalpha) and beta (ERbeta) on mouse reproductive phenotypes.

Abstract: The functions of estrogen receptors (ERs) in mouse ovary and genital tracts were investigated by generating null mutants for ERalpha (ERalphaKO), ERbeta (ERbetaKO) and both ERs (ERalphabetaKO). All ERalphaKO females are sterile, whereas ERbetaKO females are either infertile or exhibit variable degrees of subfertility. Mast cells present in adult ERalphaKO and ERalphabetaKO ovaries could participate in the generation of hemorrhagic cysts. Folliculogenesis proceeds normally up to the large antral stage in both ERalphaKO and ERbetaKO adults, whereas large antral follicles of ERalpha+/-ERbetaKO and ERalphabetaKO adults are markedly deficient in granulosa cells. Similarly, prematurely developed follicles found in prepubertal ERalphaKO ovaries appear normal, but their ERalphabetaKO counterparts display only few granulosa cell layers. Upon superovulation treatment, all prepubertal ERalphaKO females form numerous preovulatory follicles of which the vast majority do not ovulate. The same treatment fails to elicit the formation of preovulatory follicles in half of the ERbetaKO mice and in all ERalpha+/-/ERbetaKO mice. These and other results reveal a functional redundancy between ERalpha and ERbeta for ovarian folliculogenesis, and strongly suggest that (1) ERbeta plays an important role in mediating the stimulatory effects of estrogens on granulosa cell proliferation, (2) ERalpha is not required for follicle growth under wild type conditions, while it is indispensable for ovulation, and (3) ERalpha is also necessary for interstitial glandular cell development. Our data also indicate that ERbeta exerts some function in ERalphaKO uterus and vagina. ERalphabetaKO granulosa cells localized within degenerating follicles transform into cells displaying junctions that are unique to testicular Sertoli cells. From the distribution pattern of anti-Mullerian hormone (AMH) in ERalphabetaKO ovaries, it is unlikely that an elevated AMH level is the cause of Sertoli cell differentiation. Our results also show that cell proliferation in the prostate and urinary bladder of old ERbetaKO and ERalphabetaKO males is apparently normal.

The human obesity gene map: the 2004 update.

Abstract: This paper presents the eleventh update of the human obesity gene map, which incorporates published results up to the end of October 2004. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTLs) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2004, 173 human obesity cases due to single-gene mutations in 10 different genes have been reported, and 49 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 166 genes which, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 221. The number of human obesity QTLs derived from genome scans continues to grow, and we have now 204 QTLs for obesity-related phenotypes from 50 genome-wide scans. A total of 38 genomic regions harbor QTLs replicated among two to four studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably with 358 findings of positive associations with 113 candidate genes. Among them, 18 genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, >600 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful publications and genomic and other relevant sites can be found at http://obesitygene.pbrc.edu.