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Query: UNIPROT:P06889 (Mol)
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Klinefelter's syndrome (KS) is due to the presence of one or more supernumerary X chromosomes. Aneuploidy 47,XXY is the most common abnormality of sex chromosomes in humans, with an incidence of 1/500 male live births. Only one-third of subjects with KS is, however, diagnosed. The aim of this work is to present a review of current literature about neurogenetic functions in KS, referring to both clinical and therapeutics aspects. If it is well known that the majority of subjects with 47,XXY karyotype have a normal intellectual level, the identification of strengths and weaknesses of their intellectual functioning is important for the purpose of planning early psycho-educational interventions. Language difficulties are one of the more distinctive traits in cognitive functioning of people with KS. It has also been suggested that the limitations in communication markedly affect social adaptation and behavioral aspects, as well as the development of personality. Moreover, difficulties in learning language appear to be related to an altered functional lateralization; therefore, KS subjects are a suitable model for studying genetic abnormalities of lateralization. In this, perspective psychopathological risk is analyzed. Early recognition of this aspect is needed to address the educational and therapeutic perspectives for KS subjects.
Mol Hum Reprod 2010 Jun
PMID:Klinefelter's syndrome and psychoneurologic function. 2019 78

Klinefelter's syndrome (KS) is the most common chromosome aneuploidy in males, characterized by at least one supernumerary X chromosome. Although extensively studied, the pathophysiology, i.e. the link between the extra X and the phenotype, largely remains unexplained. The scope of this review is to summarize the progress made in recent years on the role of the supernumerary X chromosome with respect to its putative influence on the phenotype. In principal, the parental origin of the X chromosome, gene-dosage effects in conjunction with (possibly skewed) X chromosome inactivation, and--especially concerning spermatogenesis--meiotic failure may play pivotal roles. One of the X chromosomes is inactivated to achieve dosage-compensation in females and probably likewise in KS. Genes from the pseudoautosomal regions and an additional 15% of other genes, however, escape X inactivation and are candidates for putatively constituting the KS phenotype. Examples are the SHOX genes, identified as likely causing the tall stature regularly seen in KS. Lessons learned from comparisons with normal males and especially females as well as other sex chromosomal aneuploidies are presented. In addition, genetic topics concerning fertility and counseling are discussed.
Mol Hum Reprod 2010 Jun
PMID:Novel genetic aspects of Klinefelter's syndrome. 2022 51

Klinefelter syndrome (KS) is associated with a significant reduced life expectancy (2.1 years) including greater mortality from cardiovascular diseases. Underlying causes that may involve low levels of testosterone as well as the extra X chromosome are not fully understood. Low testosterone may have a direct affect on vascular tissue or act indirectly via metabolic effects. Testosterone levels may act genomically on cardiac function via the androgen receptor (AR) or non-genomically. Recently, it has been demonstrated that a reduced number of circulating endothelial progenitor cells (EPCs) is an independent predictor of morbidity and mortality from cardiovascular diseases. Because EPCs have never been studied in KS, we evaluated the number of circulating EPCs in 68 adult 47,XXY Klinefelter men and 46 healthy males. Patients and controls were divided into two groups, according to the absence or presence of cardiovascular risk factors (CRFs). Controls without CRFs had significantly higher levels of EPCs than controls with CRFs; on the contrary, KS patients without CRFs had EPCs levels similar to KS men with risk factors and significantly lower with respect to controls without CRFs. The number of EPCs in patients with hypogonadism was not different from that of those with normal testosterone levels. Twenty-two hypogonadal patients were re-evaluated after 6 months of androgen therapy, but we did not observe any modification in the number of EPCs. These primary hypothesis-generating data suggest that factors involved in KS, whether hypogonadism, CRFs or other genetically determined factors related to the supernumerary X chromosome might contribute to a reduction in EPCs number and that this could be considered another CRF contributing to the increased mortality of these subjects.
Mol Hum Reprod 2010 Jun
PMID:Endothelial progenitor cells as a new cardiovascular risk factor in Klinefelter's syndrome. 2022 52

Klinefelter's syndrome (KS) is the most common sex-chromosome disorder in men, affecting approximately 1:660 men, and is a rather common cause of infertility, hypogonadism and learning disability. Traditionally, men with KS have been described as tall, slim, narrow shouldered, broad hipped, with hypergonadotrophic hypogonadism and small testes. Recent studies showed an increased risk of diabetes and an unfavourable change in body composition; with accumulation of body fat and decreased muscle mass and a concomitant decrease in insulin sensitivity, muscle strength and oxygen consumption capacity. Here, we review the data on body composition, insulin resistance and metabolic syndrome in relation to testosterone in both KS patients and normal men. Treatment with testosterone in hypogonadal states (other than KS) seems to improve body composition in both clinical and experimental studies. Despite the lack of such studies in KS, we recommend testosterone treatment to KS patients with low serum testosterone or increased LH and change in body composition.
Mol Hum Reprod 2010 Jun
PMID:Klinefelter's syndrome, type 2 diabetes and the metabolic syndrome: the impact of body composition. 2023 Nov 62

In mammals, the contribution of the Y chromosome is paramount for male sexual determination; however, the presence of a single functional X chromosome is also of importance. In contrast to females where X inactivation is seen; the X chromosome of the male stays active. When, due to meiotic non-disjunction events, males are born with a supernumerary X chromosome, the resulting 47, XXY karyotype is referred to as Klinefelter's syndrome. This frequent genetic condition is most commonly associated with infertility, hypogonadism, gynecomastia and cognitive impairments. The condition has also been associated with a reduced life expectancy, insulin resistance, dyslipidemia, increased body fat mass and reduced bone mineral content. In a variety of species, male animals with karyotypes resembling Klinefelter's syndrome arise and develop a subset of features similar to those seen in humans. The availability of these animals is driving efforts to experimentally address the pathophysiology of the condition. To date, two models, 41, XXY and 41, XX(Y)* (mutated Y chromosome) male mice, have been established which resemble aspects of the pathophysiology of Klinefelter's syndrome. Experiments performed in these models confirm that the presence of a supernumerary X chromosome causes germ cell loss, cognitive deficits, Leydig cell hyperplasia, and that their Sertoli cells are capable of supporting germ cells of normal karyotype. This review summarizes the generation and characterization of the animal models for Klinefelter's syndrome and suggests experimental strategies to improve our understanding of the mechanisms underlying the pathophysiology of Klinefelter's syndrome.
Mol Hum Reprod 2010 Jun
PMID:Animal models for Klinefelter's syndrome and their relevance for the clinic. 2030 53

Klinefelter's syndrome (KS) is the most common sex chromosomal aberration among men, with estimated prevalence of about 1 in 500 newborn males. The classical phenotype of KS is widely recognized, but many affected subjects present only very mild signs. While the association between KS and infertility has been well documented, few studies have investigated sexual function in the KS patients. In the present paper we reviewed studies addressed to emotional processing and sexual function in KS. We searched the following databases Medline, Pubmed, Embase, for Klinefelter's syndrome, sexuality. We focus on the peculiar contribution of genetic and hormonal background, which characterizes sexual dysfunction in KS. Abnormal structure and function of the emotional brain circuits have been described in KS. These alterations were less pronounced when the patients underwent to testosterone replacement therapy suggesting that they were mediated by testosterone deficiency. Accordingly, clinical studies indicate that sexual dysfunctions, eventually present in KS, are not specifically associated with the syndrome but are related to the underlying hypogonadism. In conclusion, androgen deficiency more than chromosomal abnormality is the major pathogenic factor of sexual dysfunction in KS.
Mol Hum Reprod 2010 Jun
PMID:Clinical and therapeutic aspects of Klinefelter's syndrome: sexual function. 2034 47

Hypogonadism represents one of the most important causes of male osteoporosis. Testosterone regulates male bone metabolism both indirectly by aromatization to estrogens and directly through the androgen receptor (AR) on osteoblasts, promoting periosteal bone formation during puberty and reducing bone resorption during adult life. Early onset of testosterone deficiency, as observed in Klinefelter's syndrome (KS), is an important risk factor for precocious osteoporosis. Osteoporosis is present in up to 40% of subjects with KS and has usually been attributed to low testosterone levels. However, reduced bone mass might be present also in KS men with normal testosterone levels and testosterone replacement therapy does not always restore bone density in KS patients. Possible new determinants for osteoporosis in KS might be related to the AR function and insulin-like factor 3 (INSL3) levels. The CAG length and inactivation pattern of the AR in KS have been related to osteoporosis, but definitive proof is lacking. INSL3 has an anabolic role on bone metabolism by acting on osteoblasts and INSL3 levels are low in KS. Therefore, low INSL3 concentrations might represent a possible new pathogenic mechanism for reduced bone mass in KS.
Mol Hum Reprod 2010 Jun
PMID:Osteoporosis in Klinefelter's syndrome. 2034 48

G protein-coupled receptor 54 (GPR54) was first described as an orphan receptor in the rat brain one decade ago. At that time, all we knew about this receptor was that it had a high homology with other G protein-coupled receptors, like galanin receptors. Later, its endogenous ligand, kisspeptin, was identified and the kisspeptin-GPR54 system became one of the most important excitatory neuroendocrine regulators of puberty initiation. Several loss-of-function mutations in GPR54 gene were described to be associated with sporadic and familial normosmic isolated hypogonadotropic hypogonadism phenotype in humans. Consistent with this fact, knockout mice for gpr54(-/-) recapitulated the human phenotype of the lack of reproductive maturation. On the other hand, a unique activating mutation (R386P) was recently described in this receptor in a girl with central precocious puberty. This missense mutation located at carboxy-terminal tail of the GPR54 leads to prolonged activation of intracellular signaling pathways in response to kisspeptin, suggesting an uncommon model of G protein-coupled receptor activation. This chapter will describe the kisspeptin-GPR54 complex physiology and its current role in human diseases.
Prog Mol Biol Transl Sci 2009
PMID:Human diseases associated with GPR54 mutations. 2037 24

Nearly 70 years after its description, Klinefelter's syndrome (KS) remains a largely undiagnosed condition. In addition to its typical characteristics of increased follicle-stimulating hormone secretion and small and firm testes, the syndrome presents an extremely wide spectrum of phenotypes. This could be explained by the possible presence of chromosomal mosaicism, androgen receptor polymorphisms and related heterogeneous endocrine abnormalities. The varied but relatively mild physical abnormalities also explain why many patients do not receive clinical attention until adulthood, when they seek medical advice on small testes or infertility. Diagnosis is also hindered by the low awareness of the disease among health professionals. This paper aims to review the possible signs of KS at different stages of life that could help achieve an early (or at least earlier) diagnosis. It has been demonstrated that the early diagnosis of KS improves patients' quality of life and enables better medical treatment. To achieve this, it is crucial to increase both medical and general awareness of the disease, including through use of the media and patients' associations.
Mol Hum Reprod 2010 Jun
PMID:Strategies and advantages of early diagnosis in Klinefelter's syndrome. 2039 11

We reviewed cytogenetic studies performed on 4216 patients who were referred to the Cytogenetics Unit at Dicle University Hospital, Diyarbair, Southeast Turkey, between 2000 and 2009. The cases were grouped according to the reason of referral for cytogenetic analysis. The frequencies of the different types of numerical and structural abnormalities were determined, and the relative frequency of cases with abnormal karyotypes was calculated in each group. The most common reason for requesting cytogenetic testing was referral for Down syndrome and for repeated abortions. The highest frequencies of abnormal karyotypes were found among cases that were referred due to suspicion of Down syndrome (84.8%). Among the chromosomal abnormalities, sexual chromosomal abnormalities were found in 239 cases (17.6%), and Klinefelter syndrome was the most frequent sex chromosomal abnormality. Autosomal abnormalities were found in 1119 cases (82.4%), and Down syndrome was the most frequent autosomal chromosomal abnormality. In conclusion, the high rate of chromosomal abnormalities (32.2%) found in this population demonstrates the importance of cytogenetic evaluation in patients who show clinical abnormalities. This is the first report on cytogenetic testing in the southeast region of Turkey. This type of study provides a basis for determining the risks of recurrence and for deciding on clinical treatment and genetic counseling.
Genet Mol Res 2010 Jun 11
PMID:Cytogenetic analysis of 4216 patients referred for suspected chromosomal abnormalities in Southeast Turkey. 2056 54


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