[Management in an adolescent with Turner syndrome].
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Adolescent↗
Biomedical subjects
M A Mancini
Publications and source records attributed to M A Mancini.
Mitosis-specific phosphorylation of histone H3 initiates primarily within pericentromeric heterochromatin during G2 and spreads in an ordered fashion coincident with mitotic chromosome condensation.
We have generated and characterized a novel site-specific antibody highly specific for the phosphorylated form of the amino-terminus of histone H3 (Ser10). In this study, we used this antibody to examine in detail the relationship between H3 phosphorylation and mitotic chromosome condensation in mammalian cells. Our results extend previous biochemical studies by demonstrating that mitotic phosphorylation of H3 initiates nonrandomly in pericentromeric heterochromatin in late G2 interphase cells. Following initiation, H3 phosphorylation appears to spread throughout the condensing chromatin and is complete in most cell lines just prior to the formation of prophase chromosomes, in which a phosphorylated, but nonmitotic, chromosomal organization is observed. In general, there is a precise spatial and temporal correlation between H3 phosphorylation and initial stages of chromatin condensation. Dephosphorylation of H3 begins in anaphase and is complete immediately prior to detectable chromosome decondensation in telophase cells. We propose that the singular phosphorylation of the amino-terminus of histone H3 may be involved in facilitating two key functions during mitosis: (1) regulate protein-protein interactions to promote binding of trans-acting factors that "drive" chromatin condensation as cells enter M-phase and (2) coordinate chromatin decondensation associated with M-phase.
Amino Acid Sequence↗
Targeted overexpression of androgen receptor with a liver-specific promoter in transgenic mice.
The rodent liver displays marked age- and sex-dependent changes in androgen sensitivity due to the sexually dimorphic and temporally programmed expression of the androgen receptor (AR) gene. We have altered this normal phenotype by constitutive overexpression of the rat AR transgene in the mouse liver by targeting it via the human phenylalanine hydroxylase (hPAH) gene promoter. These transgenic animals in their heterozygous state produce an approximately 30-fold higher level of the AR in the liver as compared with the nontransgenic control. Androgen inactivation via sulfonation of the hormone by dehydroepiandrosterone sulfotransferase (DST), an androgen-repressible enzyme, also contributes to the age- and sex-dependent regulation of hepatic androgen sensitivity. DST has a broad range of substrate specificity and is responsible for the age- and sex-specific activation of certain polycyclic aromatic hepatocarcinogens as well, by converting them to electrophilic sulfonated derivatives. In the transgenic female, the hepatic expression of DST was approximately 4-fold lower than in normal females, a level comparable to that in normal males. The hPAH-AR mice will serve as a valuable model for studying the sex- and age-invariant expression of liver-specific genes, particularly those involved in the activation of environmental hepatocarcinogens such as the aromatic hydrocarbons.
Animals↗
Dynamic continuity of nuclear and mitotic matrix proteins in the cell cycle.
The eukaryotic cell nucleus is a membrane-enclosed compartment containing the genome and associated molecules supported by a highly insoluble filamentous network known as the nucleoskeleton or nuclear matrix. The nuclear matrix is believed to play roles in maintaining nuclear architecture and organizing nuclear metabolism. Recently, advances in microscopic techniques and the availability of new molecular probes have made it possible to localize functional domains within the nuclear matrix and demonstrate dynamic interactions between both soluble and insoluble components involved in the control of multiple nuclear transactions. Like the cytoplasm and its skeleton, the nucleoplasm is highly structured and very crowded with an equally complex skeletal framework. In fact, there is growing evidence that the two skeletal systems are functionally contiguous, providing a dynamic cellular matrix connecting the cell surface with the genome. If we impose cell cycle dynamics upon this skeletal organization, it is obvious that the genome and associated nuclear matrix must undergo a major structural transition during mitosis, being disassembled and/or reorganized in late G2 and reassembled again in daughter nuclei. However, recent evidence from our laboratory and elsewhere suggests that much of the nuclear matrix is used to form the mitotic apparatus (MA). Indeed, both facultative and constitutive matrix-associated proteins such as NuMA, CENP-B, CENP-F, and the retinoblastoma protein (Rb) associate within and around the MA. During mitosis, the nuclear matrix proteins may either become inert "passengers" or assume critical functions in partitioning the genome into newly formed G1 nuclei. Therefore, we support the view that the nuclear matrix exists as a dynamic architectural continuum, embracing the genome and maintaining cellular regulation throughout the cell cycle.
Animals↗
Combined treatment with gonadotropin-releasing hormone analog and growth hormone in central precocious puberty.
GnRH analogs (GnRHa) arrest pubertal development and slow growth velocity (GV) and bone maturation, thus improving adult height in central precocious puberty (CPP). In some patients, however, GV decreases to such an extent that it compromises the improvement in predicted adult height (PAH). Fourteen children (10 girls and 4 boys) with idiopathic CPP whose GV during GnRHa treatment decreased below the 25th percentile for chronological age with no improvement in PAH received GH at a dose of 0.3 mg/kg week, sc, 6 days/week for 2-3 yr. Fourteen children (10 girls and 4 boys) with idiopathic CPP, matched for bone age (BA), chronological age, and duration of GnRHa treatment, who showed the same growth deceleration but refused GH treatment, served as the control group. In girls, GV as so score for BA improved from -3.4 +/- 0.5 to -2.5 +/- 0.5 after 3 yr of combined treatment; PAH significantly improved from 152.7 +/- 1.7 cm (before GnRHa) and 153.5 +/- 1.7 cm (before GnRHa and GH) to 167.1 +/- 3.0 cm after 3 yr of combined treatment (P < 0.01 vs. pretreatment with GnRHa plus GH). In boys, GV as SD score for BA remained unchanged from -2.0 +/- 1.0 to -2.2 +/- 1.2 after 2 yr of combined treatment; PAH increased from 166.6 +/- 4.8 cm (before GnRHa) and 166.2 +/- 4.9 (before GnRHa plus GH) to 171.1 +/- 6.1 cm after 2 yr (P = NS). In the control group, in girls after 6 yr of GnRHa treatment, height in SD score for BA improved from -1.0 +/- 0.3 to -0.1 +/- 0.4 (P = NS), and PAH significantly improved from 155.5 +/- 2.0 to 161.5 +/- 2.1 cm (P < 0.05); in boys after 4 yr of GnRHa treatment, height in SD score for BA improved from -1.1 +/- 0.3 to -0.3 +/- 0.4 (P = NS), and PAH changed from 172.6 +/- 3.6 to 170.3 +/- 3.6 cm (P = NS). Eight of 10 girls receiving GH plus GnRHa treatment had an actual height higher than PAH and their target height. The results of our long term study indicate that in children with CPP who show a marked decrease in GV during GnRHa treatment, GH administration remarkably improves growth velocity and predicted adult height, especially in girls.
Body Height↗
The C terminus of mitosin is essential for its nuclear localization, centromere/kinetochore targeting, and dimerization.
Mitosin is a novel 350-kDa nuclear phosphoprotein that dramatically relocates from the evenly nuclear distribution in S phase to the centromere/kinetochore and mitotic apparatus in M phase. The dynamic relocalization of mitosin is accompanied by the phosphorylation of itself, suggesting that mitosin plays a role in mitotic progression. The molecular basis of nuclear localization and targeting of mitosin to the centromere/kinetochore were characterized using a set of epitope-tagged deletion mutants. The data indicate that the extreme C terminus (amino acids 2,487-3,113) of mitosin has both an independent centromere/kinetochore targeting domain and an unusually spaced bipartite nuclear localization signal. Moreover, the same centromere/kinetochore targeting domain was shown to be essential for the ability of mitosin to bind to itself or other putative mitosin-associated proteins through use of the yeast two-hybrid system. These results suggest that the C terminus of the mitosin is essential for its role in influencing cell cycle progression.
Amino Acid Sequence↗
Progression of premature thelarche to central precocious puberty.
To evaluate whether girls with premature thelarche progress to central precocious puberty (CPP) and to analyze their clinical and hormonal characteristics, we retrospectively examined 100 girls with premature thelarche who were followed for several years. Fourteen of the patients with characteristics diagnostic of premature thelarche (isolated breast development before age 8 years, bone age advancement within 2 SD of normal, normal growth velocity, follicle-stimulating hormone-predominant response to luteinizing hormone-releasing hormone) progressed during follow-up to precocious or early central puberty (progressive breast size increase, bone age acceleration, and significant decrease in predicted adult height). The chronologic age of this group of 14 girls was 5.1 +/- 2.0 years at the onset of premature thelarche and 7.8 +/- 0.6 years (mean +/- SD) after progression to central early or precocious puberty. Pelvic ultrasonography showed significant differences in measurements between the time of diagnosis of premature thelarche and progression to CPP. Nine of these patients required treatment, three with cyproterone acetate and six with luteinizing hormone-releasing hormone analogs, and all responded as expected for classic CPP. At baseline evaluation, no clinical or hormonal characteristics could be established that separated the 14 children who progressed to precocious or early puberty from the 86 girls who did not. We conclude that premature thelarche is not always a self-limited condition and may sometimes accelerate the timing of puberty.
Age Determination by Skeleton↗
Characterization of a novel 350-kilodalton nuclear phosphoprotein that is specifically involved in mitotic-phase progression.
A gene assigned to human chromosome 1q32-41 encodes a novel protein of 3,113 amino acids containing an internal tandem repeat of 177 amino acids. The protein, which we have named "mitosin," was identified by direct binding to purified retinoblastoma protein in vitro with a region distantly related to the retinoblastoma protein-binding site of E2F-1. Mitosin is expressed throughout S, G2, and M phases of the cell cycle but is absent in G1. Its localization is dramatically reorganized from a rather homogeneous nuclear distribution in S phase to paired dots at the kinetochore/centromere region, to the spindle apparatus, and then to the midbody during M-phase progression. This spatial reorganization coincides closely with the temporal phosphorylation patterns of mitosin. Overexpression of N-terminally truncated mutants blocks cell cycle progression mainly at G2/M. These results suggest that mitosin may play an important role in mitotic-phase progression.
Amino Acid Sequence↗
The retinoblastoma gene product is a cell cycle-dependent, nuclear matrix-associated protein.
The retinoblastoma gene product (Rb) has been established as a tumor suppressor and cell cycle regulator, although its mechanism of action remains obscure. The observations that several Rb-binding viral oncoproteins all associate with the nuclear matrix suggest that these interactions may occur on this structure. To determine whether Rb itself is a component of the matrix, we extracted synchronized cultured cells to isolate matrix proteins while preserving nuclear architecture. Immunoblot and immunolabeling data show that a significant portion of hypophosphorylated Rb associates with the matrix only during early G1. Mutant Rb in tumor cells did not associate with the matrix, whereas Rb-reconstituted cells contained abundant matrix-bound Rb. Rb is distributed widely throughout the matrix, particularly concentrated at the nuclear periphery and in nucleolar remnants. Core filaments of the matrix contained no detectable Rb. Our screening of expression libraries for potential Rb-associated proteins has identified several that are part of the matrix. Specifically, the peripheral matrix proteins lamin A and C bound Rb in vitro. We therefore suggest that Rb interactions with the nuclear matrix may be important for its ability to regulate cell cycle progression.
Cell Cycle↗
The amino-terminal region of the retinoblastoma gene product binds a novel nuclear matrix protein that co-localizes to centers for RNA processing.
The tumor suppressing capacity of the retinoblastoma protein (p110RB) is dependent on interactions made with cellular proteins through its carboxy-terminal domains. How the p110RB amino-terminal region contributes to this activity is unclear, though evidence now indicates it is important for both growth suppression and regulation of the full-length protein. We have used the yeast two-hybrid system to screen for cellular proteins which bind to the first 300 amino acids of p110RB. The only gene isolated from this screen encodes a novel 84-kD nuclear matrix protein that localizes to subnuclear regions associated with RNA processing. This protein, p84, requires a structurally defined domain in the amino terminus of p110RB for binding. Furthermore, both in vivo and in vitro experiments demonstrate that p84 binds preferentially to the functionally active, hypophosphorylated form of p110RB. Thus, the amino terminus of p110RB may function in part to facilitate the binding of growth promoting factors at subnuclear regions actively involved in RNA metabolism.
Amino Acid Sequence↗
The corral hypothesis: a novel regulatory mode for retinoblastoma protein function.
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Animals↗
Spatio-temporal expression of estrogen sulfotransferase within the hepatic lobule of male rats: implication of in situ estrogen inactivation in androgen action.
Estrogen sulfotransferase (EST) catalyzes transfer of the sulfate group from phosphoadenosine phosphosulfate to estrogenic steroids. Since estrogen sulfates do not bind to the estrogen receptor with high affinity, EST can control the intracellular level of the receptor-active estrogens. Androgen action in the rat liver, as indicated by the androgenic induction of alpha 2u-globulin, is inhibited by low levels of estrogens. Thus, in situ estrogen inactivation by EST is expected to increase hepatic androgen sensitivity. During the lifespan of the animal, rat liver undergoes three distinct phases of androgen sensitivity, i.e. prepubertal androgen insensitivity, androgen sensitivity after approximately 40 days of age, and androgen insensitivity during senescence (greater than 750 days). EST in the liver is expressed only after puberty, when the liver becomes androgen sensitive. Furthermore, localization of EST and its corresponding mRNA within the lobular unit of the liver demonstrates that only androgen-responsive hepatocytes located around the central vein contain immunoreactive EST and its corresponding mRNA. These temporal and spatial correlations of EST expression and hepatic androgen sensitivity support the concept that steroid-inactivating enzymes play important roles in sex hormone action.
Aging↗
The alternative splicing of fibronectin pre-mRNA is altered during aging and in response to growth factors.
The reverse transcription-polymerase chain reaction was used to examine alternative splicing at each of the three fibronectin exons known to undergo alternative splicing, i.e. extra domain A (ED-A), extra domain B (ED-B), and type III connecting sequence (IIICS). Ratios of fibronectin mRNAs with or without a given exon were determined in several rat tissues and human cell lines during aging in vivo and cellular senescence in vitro. We demonstrate that statistically significant shifts in the alternative splicing of fibronectin occur during aging in vivo and in vitro. Since all three alternatively spliced exons are spliced out at a higher frequency in aging tissues and cells, the fibronectin protein produced by old cells should be slightly smaller than that obtained from young cells. The reverse transcription-polymerase chain reaction demonstrates tissue-specific patterns of alternative splicing in several tissues. Whereas fibronectin mRNAs from adult rat tissues were found to range from 0 to 25% ED-A+ and from 0 to 10% ED-B+, fibronectin mRNAs from cultured cell lines were found to be approximately 50-60% ED-A+ and 15-25% ED-B+. We observed similarity in splicing of fibronectin RNA by the different cultured cell lines obtained from many tissues and attribute this observation to the effect of growth factors. We demonstrate that serum deprivation; placement of cells into primary culture; and growth factors such as transforming growth factor beta 1, retinoic acid, and 1,25-dihydroxyvitamin D3 can all change the alternative splicing of fibronectin pre-mRNA in the ED-A, ED-B, and type III connecting sequence exons. Possible mechanisms for the regulation of the alternative splicing of fibronectin RNA by growth factors are discussed.
Aging↗
Age-dependent reversal of the lobular distribution of androgen-inducible alpha 2u globulin and androgen-repressible SMP-2 in rat liver.
Hepatocytes situated at pericentral and periportal zones of the liver lobule show differences in the expression of several liver-specific genes, such as androgen-inducible alpha 2u globulin and androgen-repressible senescence marker protein-2 (SMP-2). A marked temporal difference in the expression of these two androgen-regulated genes has also been observed. The liver of the pre-pubertal male rat is insensitive to androgen, and during this period hepatocytes synthesize only SMP-2. During young adult life (greater than 40 days), the liver becomes androgen sensitive and concomitant synthesis of alpha 2u globulin and repression of SMP-2 occur. In the senescent male rat (greater than 750 days), the liver again becomes androgen insensitive when the decline in alpha 2u globulin is accompanied by an increase in SMP-2 synthesis. In this article we present results to show a correlation between the temporal and spatial (intralobular) changes in the expression of the androgen-inducible alpha 2u globulin and the androgen-repressible SMP-2 in rat hepatocytes. Results indicate that the temporal changes in hepatic androgen sensitivity are dictated by the intralobular location of the hepatocytes. Hepatocytes located around the central vein (pericentral/perivenous) may benefit from a paracrine advantage for the expression of a subset of genes, including the gene for the androgen receptor.
Aging↗
Androgen receptor messenger ribonucleic acid (mRNA) in the rat liver: changes in mRNA levels during maturation, aging, and calorie restriction.
By means of RNAase protection assay with an antisense cRNA probe, we have shown that the liver of the young adult male rat contains androgen receptor (AR) mRNA to a level of 4% compared to the prostate. Steady state levels of AR mRNA in the liver show both sex and age specificity. Compared to that of the male, the female liver contains a markedly reduced amount of AR mRNA. AR mRNA is almost undetectable in livers of prepubertal male (less than 35 days old) and senescent male (greater than 750 days old) rats. Both prepubertal and senescent animals are relatively insensitive to the androgenic induction of alpha 2u-globulin, a hepatic secretory protein. The age-dependent decline in hepatic androgen sensitivity and AR mRNA level can be delayed considerably by a 40% reduction in the dietary calorie intake. Analysis of poly(A)-containing RNA from two liver cell populations, hepatocytes and nonhepatocytes, revealed that only the hepatocytes that express alpha 2u-globulin gene contain AR mRNA. From these results and our earlier observation of in vitro induction of alpha 2u-globulin in isolated rat liver, we conclude 1) that androgen can act directly on hepatocytes to promote alpha 2u-globulin synthesis; 2) that changes in the hepatic androgen sensitivity during maturation and aging are reflections of the age-dependent expression of the receptor gene; and 3) that retardation of the age-dependent loss of androgen sensitivity by calorie restriction is due to a concomitant delay in the decline of the hepatic AR mRNA level.
Aging↗
The senescence marker protein (SMP-2) of the rat liver: purification, immunochemical characterization and age-dependent regulation.
In vitro translation of total rat hepatic mRNAs has identified a 31 kilodalton senescence marker protein (SMP-2) which is present in higher amounts in prepubertal and senescent males than in the post-pubertal adult male (more than 10-fold). SMP-2 is an androgen-repressible protein. The negative regulation of the SMP-2 gene activity by androgen accounts for its increased expression during the androgen insensitive states of the prepubertal and senescent livers, and its constitutive expression in the female liver. A combination of separation procedures including salt fractionation, chromatofocusing, ion-exchange chromatography and preparative gel electrophoresis have led to the purification of SMP-2 to apparent homogeneity. The purified protein showed the same electrophoretic mobility as the sex- and age-specific in vitro translation product of hepatic mRNAs. The polyclonal antibody to SMP-2 was produced in the rabbit. The antibody selectively reacted with the 31 kDa sex- and age-specific translation product of hepatic mRNAs. Western blot analysis of the liver cytosol confirms monospecificity of the antiserum, as well as age- and sex-dependent changes in the tissue level of SMP-2. Histochemical staining of liver sections with the antiserum reveals a preferential periportal localization of SMP-2 in the hepatocytes. This finding is in marked contrast to the androgen-inducible alpha 2u globulin which is preferentially synthesized and localized in the pericentral hepatocytes. Thus, the zonal distribution of SMP-2 correlates with polarized androgen sensitivity of the hepatocytes within the liver lobule.
Aging↗
Histochemical localization of catalase in cultured lens epithelial cells.
The diaminobenzidine (DAB) technique was used to investigate the localization of the peroxidatic activity of catalase in cultured lens epithelial cells at the ultrastructural level. Cultured rabbit, bovine and mouse lens epithelial cells incubated in an alkaline DAB reaction mixture contained catalase-positive microperoxisomes which were randomly distributed throughout the cytoplasm. The reaction product of catalase was abolished when cells were treated with 3-amino-1-H-1,2,4-triazole, a specific inhibitor of catalase, and was not detected when DAB or H2O2 was omitted from the incubation medium, or when the pH of the reaction mixture was lowered to 7.0. The fine structure of lens epithelial cells that were constantly exposed to 0.025 or 0.05 mM hydrogen peroxide was also determined. Lens epithelial cells that were constantly exposed to 0.05 mM H2O2 for 1-3 h exhibited damaged mitochondria, a phenomenon that did not occur when the cells were exposed to 0.025 mM peroxide.
Animals↗
Alpha 2u-globulin in modified sebaceous glands with pheromonal functions: localization of the protein and its mRNA in preputial, meibomian, and perianal glands.
alpha 2u-Globulin, the principal urinary protein of the male rat, has extensive sequence homology with many lipid binding proteins. The highest concentration of alpha 2u-globulin is found in the preputial gland, a holocrine secretory organ with pheromonal function. Meibomian and perianal glands are two other modified sebaceous glands with holocrine secretory cycles and pleiomorphic peroxisomes capable of synthesizing pheromonal lipids. Immunocytochemical examination shows the presence of alpha 2u-globulin in the acinar cells of all three of these modified sebaceous glands. Whereas in the preputial gland all of the acinar cells exhibit immunoreactivity, in the meibomian and perianal glands only selective cells contain alpha 2u-globulin. In the case of the preputial gland, in addition to the acinar cells some stratified epithelial cells also were immunoreactive. In the perianal and meibomian glands, keratinocytes lining nearby hair shafts and select cells of accessory oil glands stained for alpha 2u-globulin. In situ hybridization with a cloned cRNA probe confirmed the immunocytochemical data. Presence of the alpha 2u-globulin mRNA in these glands was also established by Northern blot analysis. Immunoelectron microscopic examination of preputial alpha 2u-globulin showed the presence of this protein in secretory granules of various maturational stages. Immunolabeled alpha 2u was also found in attached vesicles containing protein and lipid inclusions. The lytic cells were not only loaded with alpha 2u-globulin but also contained sharp-edged, irregularly shaped electron-dense granules which stained heavily for this protein. Specific localization of alpha 2u-globulin and its mRNA in three pheromone-producing sebaceous glands and its structural homology with known lipid binding proteins indicate a pheromone carrier role of alpha 2u-globulin.
Alpha-Globulins↗