Mutations in a novel, cryptic exon of the luteinizing hormone/chorionic gonadotropin receptor gene cause male pseudohermaphroditism.
Mutations in a novel, cryptic exon of the luteinizing hormone/chorionic gonadotropin receptor gene cause male pseudohermaphroditism.
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DOI：
10.1371/journal.pmed.0050088
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发表时间：
2008-04-22
期刊：
影响因子：
15.8
通讯作者：
Gromoll J
中科院分区：
文献类型：
--
作者：
Kossack N;Simoni M;Richter-Unruh A;Themmen AP;Gromoll J
男性假雌雄同体，或称间质细胞发育不全（LCH），是一种常染色体隐性遗传病，常见于46，XY核型的个体，其特征是显性女性表型，阴道失明，乳房发育缺失，原发性闭经和睾丸结构的存在。它是由黄体生成素/绒毛膜促性腺激素受体基因（LHCGR）突变引起的，这种突变损害了LH/CG结合或信号转导。然而，分子分析显示，LHCGR在约50%的LCH全临床表型患者中明显正常。因此，我们在LHCGR中寻找导致LCH的新基因组元件。在目前的研究中，我们在LHCGR基因中发现了一个新的、灵长类动物特异性的外显子（外显子6A）。它具有内/末端外显子的复合特征，并具有在LHCGR中触发无义介导的mRNA衰变（NMD）的终止密码子。包括外显子6A在内的转录本在人类睾丸和颗粒细胞中生理上高度表达，并导致细胞内截断209个氨基酸的LHCGR蛋白。我们对16例不明原因LCH患者的外显子6A进行测序，并在3例患者中检测到突变。功能研究显示，突变的内部外显子6A转录本的表达显著增加，表明NMD异常。这些LHCGR转录本比例的改变导致主要无功能的LHCGR亚型的产生，从而阻碍了正常的表达和功能。这一新的外显子的鉴定和表征不仅在LHCGR的基因组组织中发现了一个新的调控元件，而且还指出了一个复杂的受体调控网络，包括转录水平的事件。这些发现增加了LCH的分子诊断工具，并扩展了我们对性别分化的内分泌调节的理解。Joerg Gromoll和他的同事描述了一个新的外显子的鉴定和特征，该外显子似乎是三个间质细胞发育不全个体的黄体生成素/绒毛膜促性腺激素受体基因中的一个新的调控元件。一个人的性别是由他们的X和Y（性）染色体的补体决定的。有两条X染色体的人在基因上是女性，通常有卵巢和女性外部性器官。拥有X和Y染色体的人在基因上是男性，并且有睾丸和男性外部性器官。然而，有时生殖器官的发育不正常，导致染色体、性腺（卵巢或睾丸）和外部性器官不一致的“双性人”。间质细胞发育不全（LCH，亦称男性假两性畸形或性发育障碍）是一种XY型女性间性疾病。患有这种遗传病的人有睾丸，但也有阴道（与子宫没有连接），他们没有乳房或月经。这种性特征的混合是由于睾丸的间质细胞发育不全。间质细胞通常分泌睾丸激素，这种激素促进男性性特征的发展和维持。出生前，绒毛膜促性腺激素（CG，一种由胎盘产生的激素）刺激间质细胞的发育和睾酮的产生；出生后，由脑垂体分泌的黄体生成素（LH）刺激睾酮的产生。这两种激素都与间质细胞表面的一种蛋白质LH/CG受体结合。在LCH中，这种受体要么不能结合CG和LH，要么不能告诉间质细胞制造睾酮。编码LH/CG受体的基因被称为LHCGR。在LCH患者中已经发现了几种使LC/CG受体失活的突变（遗传变化）。然而，LHCGR基因在50%的双性人身上显然是正常的。在这项研究中，研究人员详细检查了LHCGR基因，试图在这些个体中找到潜在的遗传缺陷。研究人员使用了几种分子生物学技术来鉴定人类LHCGR基因中的一个新的外显子-外显子6a。外显子是包含制造蛋白质信息的DNA序列；内含子是中断基因编码序列的DNA序列。内含子和外显子都被转录成信使RNA (mRNA)，然后外显子被“剪接”在一起，形成成熟的mRNA，后者被翻译成蛋白质。研究人员鉴定了几种不同剪接的LHCGR mRNA转录本，这些转录本包含外显子6A - a端外显子6A mRNA，其中包含外显子1-6和外显子6A，以及两个内部外显子6A mRNA，也包含外显子7-11。研究人员报告说，人类睾丸表达高水平的末端外显子6A转录本，它被翻译成LHCGR蛋白的短版本，留在细胞内（全长LHCGR移动到细胞表面）。相比之下，睾丸含有低水平的内部外显子6A mrna。这是因为外显子6A包含两个过早终止密码子（标记蛋白质末端的DNA序列），它们触发“无义介导的衰变”（NMD），这是一种细胞监视机制，通过降解含有内部终止密码子的mrna来调节蛋白质合成。当研究人员筛选16名患有LCH但没有已知LHCGR基因突变的人时，有3人外显子6A发生突变。实验室实验表明，这些突变大大增加了细胞中存在的内部外显子6A转录本的数量，并干扰了细胞对绒毛膜促性腺激素的正常反应。这些发现在LHCGR基因中发现了一个新的功能性外显子，并表明该外显子的突变导致了一些LCH病例。这是人类疾病首次与作为NMD靶点的外显子突变相关联。此外，这些发现为LHCGR是如何被调控提供了重要的见解。研究人员推测，在转录水平上，一个包含含有转录本的外显子6a和NMD的复杂网络通常会严格调节功能性LHCGR的产生。他们认为，当外显子6A出现突变时，NMD是所有含外显子6A转录本的主要途径，从而大大减少了功能性LHCGR的数量。请通过本摘要的在线版本http://dx.doi.org/10.1371/journal.pmed.0050088访问这些网站。MedlinePlus百科全书有一个关于双性人状况的页面（英语和西班牙语）维基百科有关于双性人和LH/CG受体的页面(注意维基百科是一个免费的在线百科全书，任何人都可以编辑；北美双性人协会为双性人儿童的父母提供信息和支持。雄激素不敏感综合征支持小组也提供一些关于双性人疾病的一般信息，包括LCH和其他XY女性疾病的信息（几种语言）。序列-结构-功能分析（SSFA），由德国的一组研究人员(莱布尼茨研究所<e:2>分子药理学；Humboldt-Universitätzu Berlin)，是一个处理糖蛋白激素受体的序列、结构和功能的数据库，糖蛋白激素受体信息系统（GRIS）是一个提供LHCGR结构信息的数据库，该数据库来自布鲁塞尔自由大学和跨学科人类生物学和molcculaire研究所
Male pseudohermaphroditism, or Leydig cell hypoplasia (LCH), is an autosomal recessive disorder in individuals with a 46,XY karyotype, characterized by a predominantly female phenotype, a blind-ending vagina, absence of breast development, primary amenorrhea, and the presence of testicular structures. It is caused by mutations in the luteinizing hormone/chorionic gonadotropin receptor gene (LHCGR), which impair either LH/CG binding or signal transduction. However, molecular analysis has revealed that the LHCGR is apparently normal in about 50% of patients with the full clinical phenotype of LCH. We therefore searched the LHCGR for novel genomic elements causative for LCH. In the present study we have identified a novel, primate-specific bona fide exon (exon 6A) within the LHCGR gene. It displays composite characteristics of an internal/terminal exon and possesses stop codons triggering nonsense-mediated mRNA decay (NMD) in LHCGR. Transcripts including exon 6A are physiologically highly expressed in human testes and granulosa cells, and result in an intracellular, truncated LHCGR protein of 209 amino acids. We sequenced exon 6A in 16 patients with unexplained LCH and detected mutations in three patients. Functional studies revealed a dramatic increase in the expression of the mutated internal exon 6A transcripts, indicating aberrant NMD. These altered ratios of LHCGR transcripts result in the generation of predominantly nonfunctional LHCGR isoforms, thereby preventing proper expression and functioning. The identification and characterization of this novel exon not only identifies a new regulatory element within the genomic organization of LHCGR, but also points toward a complex network of receptor regulation, including events at the transcriptional level. These findings add to the molecular diagnostic tools for LCH and extend our understanding of the endocrine regulation of sexual differentiation. Joerg Gromoll and colleagues describe the identification and characterization of a novel exon that appears to be a new regulatory element within the luteinizing hormone/chorionic gonadotropin receptor gene of three individuals with Leydig cell hypoplasia. A person's sex is determined by their complement of X and Y (sex) chromosomes. Someone who has two X chromosomes is genetically female and usually has ovaries and female external sex organs. Someone who has an X and a Y chromosome is genetically male and has testes and male external sex organs. Sometimes, though, the development of the reproductive organs proceeds abnormally, resulting in a person with an “intersex” condition whose chromosomes, gonads (ovaries or testes), and external sex organs do not correspond. Leydig cell hypoplasia (LCH; also called male pseudohermaphroditism or a disorder of sex development) is an XY female intersex condition. People with this inherited condition develop testes but also have a vagina (which is not connected to a womb), and they do not develop breasts or have periods. This mixture of sexual characteristics arises because the Leydig cells in the testes are underdeveloped. Leydig cells normally secrete testosterone, the hormone that promotes the development and maintenance of male sex characteristics. Before birth, chorionic gonadotropin (CG; a hormone made by the placenta) stimulates Leydig cell development and testosterone production; after birth, luteinizing hormone (LH), which is made by the pituitary gland, stimulates testosterone production. Both hormones bind to the LH/CG receptor, a protein on the surface of Leydig cells. In LCH, this receptor either does not bind CG and LH or fails to tell the Leydig cells to make testosterone. The gene that encodes the LH/CG receptor is called LHCGR. Several mutations (genetic changes) that inactivate the LC/CG receptor have been identified in people with LCH. However, the LHCGR gene is apparently normal in 50% of people with this intersex condition. In this study, the researchers examine the LHCGR gene in detail to try to find the underlying genetic defect in these individuals. The researchers used several molecular biology techniques to identify a new exon—exon 6A—within the human LHCGR gene. (Exons are DNA sequences that contain the information for making proteins; introns are DNA sequences that interrupt the coding sequence of a gene. Both introns and exons are transcribed into messenger RNA [mRNA] and the exons are then “spliced” together to make the mature mRNA, which is translated into protein.) The researchers identify several differently spliced LHCGR mRNA transcripts that contain exon 6A—a terminal exon 6A mRNA that contains exons 1–6 and exon 6A, and two internal exon 6A mRNAs that also contain exons 7–11. The researchers report that human testes express high levels of the terminal exon 6A transcript, which is translated into a short version of LHCGR protein that remains within the cell (full-length LHCGR moves to the cell surface). By contrast, testes contain low levels of the internal exon 6A mRNAs. This is because exon 6A contains two premature stop codons (DNA sequences that mark the end of a protein), which trigger “nonsense-mediated decay” (NMD), a cellular surveillance mechanism that regulates protein synthesis by degrading mRNAs that contain internal stop codons. When the researchers screened 16 people with LCH but without known mutations in the LHCGR gene, three had mutations in exon 6A. Laboratory experiments show that these mutations greatly increased the amounts of the internal exon 6A transcripts present in cells and interfered with the cells' normal response to chorionic gonadotropin. These findings identify a new, functional exon in the LHCGR gene and show that mutations in this exon cause some cases of LCH. This is the first time that a human disease has been associated with mutations in an exon that is a target for NMD. In addition, these findings provide important insights into how the LHCGR is regulated. The researchers speculate that a complex network that involves the exon 6A-containing transcripts and NMD normally tightly regulates the production of functional LHCGR already at the transcriptional level. When mutations are present in exon 6A, they suggest, NMD is the predominant pathway for all the exon 6A-containing transcripts, thereby drastically decreasing the amount of functional LHCGR. Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050088. The MedlinePlus Encyclopedia has a page on intersex conditions (in English and Spanish) Wikipedia has pages on intersexuality and on the LH/CG receptor (note that Wikipedia is a free online encyclopedia that anyone can edit; available in several languages) The Intersex Society of North America provides information and support for the parents of children with intersex conditions The Androgen Insensitivity Syndrome Support Group also provides some general information about intersex conditions, including information about LCH and other XY female conditions (in several languages) Sequence-Structure-Function-Analysis (SSFA), run by a group of researchers in Germany (Leibniz-Institut für Molekulare Pharmakologie; Humboldt-Universitätzu Berlin), is a database dealing the sequence, structure, and function of glycoprotein hormone receptors Glycoprotein-hormone Receptors Information System (GRIS), from Université Libre de Bruxelles and Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire, is a database giving structural information on the LHCGR
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影响因子：
3.6
作者：
Gromoll, J;Wistuba, J;Simoni, M
通讯作者：
Simoni, M
影响因子：
5.8
作者：
Misrahi, M;Meduri, G;Bougneres, P
通讯作者：
Bougneres, P
影响因子：
14.9
作者：
SHEETS, MD;OGG, SC;WICKENS, MP
通讯作者：
WICKENS, MP
影响因子：
30.8
作者：
Modrek, B;Lee, CJ
通讯作者：
Lee, CJ
影响因子：
5.8
作者：
Gromoll, J;Schulz, A;Seif, FJ
通讯作者：
Seif, FJ