人类性别决定和性别分化研究进展

SRY基因在人类性别分化中起着关键作用,目前研究认为SRY仅是涉及性别决定过程的基因之一,其他基因和SRY相关基因SOX9,抗副中肾激素基因AMH,编码缁类因子的基因SF1,X－连锁的DAX基因,wilm‘s肿瘤抑制基因WT1等基因都参与了人类性腺分化和发育,本文拟就人类性别决定基因的研究进展及其与人类性别分化的关系作一综述。     

SRY基因及其性别决定

对近十年来关于脊椎动物尤其是哺乳动物的SRY基因及其性别决定机制的研究进展作了简要的综述。扼要阐述了哺乳动物的SRY基因的结构、转录、表达及其在性别决定中的作用模式及相关的基因家族。     

寻找人类性别决定基因的历程

动物和人类性别决定机制的探讨是生命科学中一个重要研究领域,性决定和性分化过程决定着雌性和雄性两种性别的存在。性别决定是在受精的瞬间就确定了的,是性分化的遗传基础;而性分化则是一个由早期胚胎至性成熟分化发育的复杂调控过程。该项研究不仅有益于对人类性别相关疾病的诊断治疗,而且对于动物性别的人为控制和个体性别鉴定,以及对于从低等脊椎动物到人类性别决定机制进化的探讨都具有重大价值。１　人类中存在性别决定基因对于哺乳动物的早期研究结果已使人们认识到精子有两种类型：“Ｘ精子”和“Ｙ精子”,受精时哪种类型的精…     

SOX9基因与性别决定的关系

1 .性别决定简介[1～ 5 ]哺乳动物包括人类的性别决定问题一直是科学史上的一个难解之谜。科学家们经过异常艰苦的研究才逐步揭开性别决定的神秘面纱。位于男性Ｙ染色体上的ＳＲＹ(ｓｅｘｄｅ ｔｅｒｍｉｎｇｒｅｇｉｏｎｏｆＹｃｈｒｏｍｏｓｏｍｅ)基因是当前被确定的睾丸决定因子 (ＴＤＦ)的主要侯选基因 ,它是哺乳动物中睾丸发育的主要诱导者。ＳＲＹ基因编码的蛋白质含有与ＤＮＡ结合的模体 ,称为ＨＭＧ盒 (与高速泳动类蛋白质相关的一种模体 )。ＨＭＧ盒存在于很多转录因子中。ＳＲＹ蛋白的ＨＭＧ盒与特定的ＤＮＡ序列结合 ,表明它在…     

植物的性、性染色体及性别决定

高等植物的性别表型具多态性,这与植物性别决定的遗传基础有关,高等植的性别与性别决定基因,性染色体及常染色体有关,其性别决定系统有性别决定基因决定性别、性染色体决定性别及X染色体与常染色体间的基因平衡决定性别等多种方式。     

鱼类性别与性别鉴定

性别分化和性别决定相互联系又有所区别,具双向潜力的未分化性腺经过程序性发生的一系列事件,发育成精巢或卵巢,并出现第二性征的过程称为性别分化,而性别决定则是确定性分化方向的方式。       

家蚕性别及其决定基因的研究进展

家蚕作为模式生物和鳞翅目昆虫的典型代表,性别决定的分子机制是近年来的研究热点,其分子机制的阐明将为家蚕的雄蚕饲养和害虫的生物防治打下基础.主要对国内外家蚕性别决定、性染色体、家蚕性别决定基因的研究进展进行了综述,并对家蚕性别调控研究中存在的问题进行了分析和展望.     

性别决定与性染色体

较系统地介绍生物性别决定的遗传类型及其理论基础,阐明性染色体上基因的遗传特点和引起性别分化的途径;论述性别决定与性染色体的关系。     

哺乳动物性别决定及其机制的研究

哺乳动物的性别决定与性别分化是在以SRY基因为主,SOX基因、DAX-1等众多基因的参与下实现的。哺乳动物性别决定的研究涉及到三个方面的内容:性别决定机制、性别决定进化和物种间性别决定差异。性别决定的进化和物种间性别决定的差异对性别决定机制的研究提供了重要的线索。     

Human sex ratios and sex distribution in sibships of size 2

We previously analyzed data from the U.S. National Health Interview Survey (NHIS, 1998 to 2002) on families with two biological children (10 years of age and younger) and found that the distribution of families with two boys, two girls, and one boy + one girl did not statistically conform to a binomial distribution regardless of the boy/girl sex ratio used. Using the best estimate of the sex ratio from the data, we found that there were significantly more families with opposite-sex siblings than families with same-sex siblings. No biological mechanism could explain these results at the time. In the present study we conducted an analysis of the first two children in sibships of size 3 from the same data source and found that there are significantly more same-sex sibships than unlike-sex sibships. Combining the two sets of data for the first two children produced observed numbers in close agreement with the expected numbers. A hypothesis of parental choice (family planning) appears to be strongly supported as an explanation for the discrepancies in the two sets of data individually. For example, parents who have a boy and a girl (either order) as their first two children are more likely to stop having children ("stopping rule") than are parents whose first two children are of the same sex.     

Effects of temperature on the deformity and sex differentiation of tilapia, Oreochromis mossambicus

The effects of temperature on the deformity and sex differentiation of tilapia, Oreochromis mossambicus, were investigated. Zero- (the hatching day), 5-, and 10-day-old tilapia were respectively divided into 4 groups that were reared at 20, 24, 28, and 32 degrees C for 5 days. Percentages of deformity were significantly increased when tilapia were kept in the elevated temperatures (28 and 32 degrees C) before 5 days old during this experiment, whereas the lower temperature (20 degrees C) had no effect on the development of morphology. On the other hand, exposure to the lower temperature before 10 days old induced a high proportion of females whereas a high proportion of males was induced by the elevated temperature after 10 days old during this experiment. These results indicate that morphological development is influenced by temperature, particularly by the elevated temperature during a restricted developmental period. Both lower and elevated temperatures induce the gonadal feminization and masculinization, respectively, during its restricted developmental period. J. Exp. Zool. 286:534-537, 2000.     

Human male meiotic sex chromosome inactivation

In mammalian male gametogenesis the sex chromosomes are distinctive in both gene activity and epigenetic strategy. At first meiotic prophase the heteromorphic X and Y chromosomes are placed in a separate chromatin domain called the XY body. In this process, X,Y chromatin becomes highly phosphorylated at S139 of H2AX leading to the repression of gonosomal genes, a process known as meiotic sex chromosome inactivation (MSCI), which has been studied best in mice. Post-meiotically this repression is largely maintained. Disturbance of MSCI in mice leads to harmful X,Y gene expression, eventuating in spermatocyte death and sperm heterogeneity. Sperm heterogeneity is a characteristic of the human male. For this reason we were interested in the efficiency of MSCI in human primary spermatocytes. We investigated MSCI in pachytene spermatocytes of seven probands: four infertile men and three fertile controls, using direct and indirect in situ methods. A considerable degree of variation in the degree of MSCI was detected, both between and within probands. Moreover, in post-meiotic stages this variation was observed as well, indicating survival of spermatocytes with incompletely inactivated sex chromosomes. Furthermore, we investigated the presence of H3K9me3 posttranslational modifications on the X and Y chromatin. Contrary to constitutive centromeric heterochromatin, this heterochromatin marker did not specifically accumulate on the XY body, with the exception of the heterochromatic part of the Y chromosome. This may reflect the lower degree of MSCI in man compared to mouse. These results point at relaxation of MSCI, which can be explained by genetic changes in sex chromosome composition during evolution and candidates as a mechanism behind human sperm heterogeneity.     

Human sex ratio and sex-related selection at birth

Sex ratio in 11,500 infants died at different perinatal periods (antenatal, intranatal and postnatal) is studied. Sex ratio in these periods is: 107 male : 100 female; 136 male : 100 female; 168 male : 100 female respectively; differences at each period are statistically significant (alpha less than 0.001). A change in differential sex-linked mortality is observed at perinatal period. High mortality in males, which is characteristic of human postnatal ontogenesis, manifests distinctly from the moment of passing on to extrauterine life.     

Human behaviour: sex ratio and the city

The ratio of males to females in a population is known to influence the behaviour, life histories and demography of animals. A recent experimental study finds that sex ratio also affects human economic behaviour, and in a manner consistent with evolutionary theory.     

Human IgG Fc-glycosylation profiling reveals associations with age, sex, female sex hormones and thyroid cancer

IgG functions rely on interactions of the Fc region with other proteins, which are optimized by tailoring of a conserved N-linked glycosylation at Asn-297. We conducted a study involving 735 control individuals and 138 thyroid cancer patients. Here we demonstrated that previously described age-related change in Fc-glycosylation was further characterized by definite sex specificity. In females, the incidences of most of glycosylated forms began to pose characteristic changes at ages of puberty or menopause. In addition, glycan-glycan relationships existed extensively within Fc glycosylation, which were characterized to be altered upon different states of subjects, such as age, sex and thyroid cancer. In thyroid cancer patients, detailed comparison of glycosylation incidences with control individuals yielded insight into aberrant change in IgG(1) Fc-glycosylation. This aberrant pattern was also featured by remarkable specificities of both age and sex. The receiver operating characteristic curve analysis was used to determine diagnostic values of Fc glycosylation. Finally, clinical measurement of two major female sex hormones estradiol and progesterone was conducted to determine potential associations of hormones with IgG Fc glycosylation. This study provided an important view to the associations of IgG Fc N-linked glycosylation with age, sex, female sex hormones and thyroid cancer. This article is part of a Special Issue entitled: Proteomics: The clinical link.     

Human and mouse amelogenin gene loci are on the sex chromosomes

Enamel is the outermost covering of teeth and is the hardest tissue in the vertebrate body. The enamel matrix is composed of enamelin and amelogenin classes of protein. We have determined the chromosomal locations for the human and mouse amelogenin (AMEL) loci using Southern blot analyses of DNA from human, mouse, or somatic cell hybrids by hybridization to a characterized mouse amelogenin cDNA. We have determined that human AMEL sequences are located on the distal short arm of the X chromosome in the p22.1----p22.3 region and near the centromere on the Y chromosome, possibly at the proximal long arm (Yq11) region. These chromosomal assignments are consistent with the hypothesis that perturbation of the amelogenin gene is involved in X-linked types of amelogenesis imperfecta, as well as with the Y-chromosomal locations for genes that participate in regulating tooth size and shape. Unlike the locus in humans, the mouse AMEL locus appears to be assigned solely to the X chromosome. Finally, together with the data on other X and Y chromosome sequences, these data for AMEL mapping support the notion of a pericentric inversion occurring in the human Y chromosome during primate evolution.