Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: UNIPROT:Q00604 (X-linked)
16,883 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

X-linked adrenal hypoplasia congenita (AHC) with hypogonadotropic hypogonadism was recently shown to be caused by mutations in a gene referred to as DAX-1, which encodes a novel member of the orphan nuclear receptor family. DAX-1 is homologous to other nuclear receptors in its carboxy-terminal region, but it lacks the characteristic zinc finger DNA-binding domain. The tissue distribution of DAX-1 (adrenal cortex, gonads, hypothalamus, and pituitary) is the same as that of another orphan nuclear receptor, steroidogenic factor 1 (SF-1), that is required for development of the adrenal glands and gonads. We examined whether DAX-1 and SF-1 might interact in the regulation of SF-1-responsive target genes. Coexpression of DAX-1 and SF-1 inhibited SF-1-mediated transactivation. DAX-1 was shown to interact directly with SF-1 in in vitro protein binding studies; however, it did not interfere with SF-1 binding to DNA in gel mobility shift assays. Transactivation by GAL4-SF-1 constructs was inhibited by DAX-1, indicating that neither the SF-1 DNA-binding domain nor the SF-1 binding sites are required for inhibition by DAX-1. A series of DAX-1 deletion mutants localized the inhibitory domain to the carboxy-terminal region of the protein. Deletion of this domain also reduced basal transcriptional silencing by GAL4-DAX-1. This inhibitory domain has been deleted in all naturally occurring AHC deletion mutants described to date. In addition, two naturally occurring point mutations in DAX-1 exhibited impaired inhibition of SF-1. We conclude that DAX-1 can inhibit SF-1 transcriptional activity and suggest that the loss of this inhibitory property in DAX-1 may account in part for the phenotype of AHC.
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PMID:DAX-1 inhibits SF-1-mediated transactivation via a carboxy-terminal domain that is deleted in adrenal hypoplasia congenita. 903 75

The DAX-1 [DSS (dosage sensitive sex)-AHC critical region on the X, gene 1] gene is responsible for X-linked adrenal hypoplasia congenita (AHC). However, DAX-1 protein structure-function relationships are not well understood. Identification of missense mutations may help to reveal these relationships. We analyzed the DAX-1 gene from seven patients in six kindreds with X-linked AHC and identified one frameshift mutation, two missense mutations, and three deletion mutations. Case 1 had a 388delAG frameshift mutation, inducing a premature stop codon at position 70. Case 2 had a missense mutation, Lys382Asn, which encodes an asparagine (Asn) for lysine (Lys) at position 382. Sibling cases of 3-1 and 3-2 had a missense mutation of Trp291 Cys, which encodes a substitution of cysteine (Cys) for tryptophan (Try) at position 291. The tryptophan (Trp) at position 291 and lysine (Lys) at position 382 in human DAX-1 protein are highly conserved among other related orphan nuclear receptor superfamily members. Cases 4, 5, and 6 showed deletion mutation. In case 6, a de novo deletion mutation was revealed by both southern hybridization and polymerase chain reaction (PCR) of a GGAA tetranucleotide tandem repeat. These findings suggest that: 1) Trp at position 291 and Lys at position 382, located in the C-terminal presumptive ligand binding domain, are important to the functional role of the DAX-1 protein in adrenal embryogenesis and/or in hypothalamic-pituitary activity; and 2) molecular analysis of the DAX-1 gene may help genetic counseling, even in cases with deletion mutation, because a detection of de novo deletion may exclude another affected or carrier child.
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PMID:Three novel mutations and a de novo deletion mutation of the DAX-1 gene in patients with X-linked adrenal hypoplasia congenita. 936 May 49

The orphan nuclear receptor steroidogenic factor 1 (SF-1) is a critical developmental regulator in the urogenital ridge, because mice targeted for disruption of the SF-1 gene lack adrenal glands and gonads. SF-1 was recently shown to interact with DAX-1, another orphan receptor whose tissue distribution overlaps that of SF-1. Naturally occurring loss-of-function mutations of the DAX-1 gene cause the human disorder X-linked adrenal hypoplasia congenita (AHC), which resembles the phenotype of SF-1-deficient mice. Paradoxically, however, DAX-1 represses the transcriptional activity of SF-1, and AHC mutants of DAX-1 lose repression function. To further investigate these findings, we characterized the interaction between SF-1 and DAX-1 and found that their interaction indeed occurs through a repressive domain within the carboxy terminus of SF-1. Furthermore, we demonstrate that DAX-1 recruits the nuclear receptor corepressor N-CoR to SF-1, whereas naturally occurring AHC mutations of DAX-1 permit the SF-1-DAX-1 interaction, but markedly diminish corepressor recruitment. Finally, the interaction between DAX-1 and N-CoR shares similarities with that of the nuclear receptor RevErb and N-CoR, because the related corepressor SMRT was not efficiently recruited by DAX-1. Therefore, DAX-1 can serve as an adapter molecule that recruits nuclear receptor corepressors to DNA-bound nuclear receptors like SF-1, thereby extending the range of corepressor action.
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PMID:Nuclear receptor DAX-1 recruits nuclear receptor corepressor N-CoR to steroidogenic factor 1. 956 14

DAX1 is an unusual member of the orphan nuclear receptor family of transcription factors. Mutations in human DAX1 cause X-linked adrenal hypoplasia congenita, while abnormal duplication of the gene is responsible for male-to-female dosage-sensitive sex reversal. Based on these and other observations, DAX1 is thought to play a role in adrenal and gonadal development in mammals. As DAX1 has not previously been described in any other vertebrate, a putative avian DAX1 clone was isolated from an embryonic chicken (Gallus domesticus) urogenital ridge cDNA library. The expression profile of this cDNA was then examined during gonadogenesis. The clone included the conserved 3' ligand-binding motif identified in humans and mice but the 5' region lacked the repeat motif thought to specify a DNA-binding domain in mammals. Southern blot analysis and fluorescence in situ hybridisation mapping showed that the gene is autosomal, located on chromosome 1q. Sequence comparisons showed that the putative chicken DAX1 protein has 63 and 60% identity with the human and mouse proteins respectively over the region of the conserved ligand-binding domain. However, stronger identity (74%) exists with a putative alligator DAX1 sequence over the same region. Northern blotting detected a single 1.4 kb transcript in late embryonic chicken gonads, while RNase protection assays revealed expression in the embryonic gonads of both sexes during the period of sexual differentiation. Expression increased in both sexes during gonadogenesis, but was higher in females than in males. This is the first description of a DAX1 homologue in a non-mammalian vertebrate.
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PMID:Cloning and expression of a DAX1 homologue in the chicken embryo. 1065 94

Mutations in several genes have been shown to cause hypogonadotropic hypogonadism (HHG) in humans. This condition may result from abnormalities in hypothalamic gonadotropin-releasing hormone (GnRH) secretion, impaired pituitary gonadotropin release, or both. Here, we consider mutations in KAL in X-linked Kallmann syndrome; DAX1 in X-linked adrenal hypoplasia congenita; the related orphan nuclear receptor, steroidogenic factor-1; leptin and prohormone convertase-1, which may influence GnRH release and processing; the GnRH receptor; the pituitary transcription factors, HESX-1, LHX3 and PROP-1; and the gonadotropins, follicle stimulating hormone (FSH) and luteinizing hormone (LH). Identifying naturally occurring mutations in these genes provides important information about the role of these factors in the development and function of the hypothalamic-pituitary gonadal axis in humans. Different approaches to treatment and counseling may be needed, depending on the condition. Furthermore, the pathophysiological basis of HHG in the majority of individuals remains unclear, despite recent advances. Other candidate genes may be involved in these patients.
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PMID:Advances in the molecular genetics of hypogonadotropic hypogonadism. 1122 Jul 2

DAX-1 [dosage-sensitive sex reversal, adrenal hypoplasia congenita (AHC) critical region on the X chromosome, gene 1] is an orphan nuclear receptor that represses transcription by steroidogenic factor-1 (SF-1), a factor that regulates expression of multiple steroidogenic enzymes and other genes involved in reproduction. Mutations in the human DAX1 gene (also known as AHC) cause the X-linked syndrome AHC, a disorder that is associated with hypogonadotropic hypogonadism also. Characterization of Dax1-deficient male mice revealed primary testicular defects that included Leydig cell hyperplasia (LCH) and progressive degeneration of the germinal epithelium, leading to infertility. In this study, we investigated the effect of Dax1 disruption on the expression profile of various steroidogenic enzyme genes in Leydig cells isolated from Dax1-deficient male mice. Expression of the aromatase (Cyp19) gene, which encodes the enzyme that converts testosterone to estradiol, was increased significantly in the Leydig cells isolated from mutant mice, whereas the expression of other proteins (e.g., StAR and Cyp11a) was not altered. In in vitro transfection studies, DAX-1 repressed the SF-1-mediated transactivation of the Cyp19 promoter but did not inhibit the StAR or Cyp11a promoters. Elevated Cyp19 expression was accompanied by increased intratesticular levels of estradiol. Administration of tamoxifen, a selective estrogen-receptor modulator, restored fertility to the Dax1-deficient male mice and partially corrected LCH, suggesting that estrogen excess contributes to LCH and infertility. Based on these in vivo and in vitro analyses, aromatase seems to be a physiologic target of Dax-1 in Leydig cells, and increased Cyp19 expression may account, in part, for the infertility and LCH in Dax1-deficient mice.
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PMID:Aromatase (Cyp19) expression is up-regulated by targeted disruption of Dax1. 1142 38

DAX-1 is an orphan nuclear receptor that plays a key role in the development and function of the adrenal gland and hypothalamic-pituitary gonadal axis. Mutations in the gene encoding DAX-1 result in X-linked adrenal hypoplasia congenita (AHC). Affected boys typically present with primary adrenal failure in infancy or childhood and hypogonadotropic hypogonadism at the time of puberty. The majority of DAX1 mutations described to date are nonsense or frameshift mutations that result in premature truncation of the DAX-1 protein and loss of DAX-1 repressor function. Relatively few missense mutations in DAX1 have been reported. Here, we describe missense mutations in three additional families with X-linked AHC. When combined with previous reports, the DAX1 missense mutations appear to cluster within restricted regions of the putative ligand-binding domain of DAX-1 and affect amino acids that are evolutionarily conserved, suggesting that these regions correspond to critical functional domains. Transcription assays, using a variety of artificial and native target genes, were performed to assess the effects of these mutations on the function of DAX-1. All DAX-1 missense mutant constructs showed marked loss of repressor function, with the exception of I439S, a mutation previously shown to be associated with delayed-onset adrenal failure and incomplete hypogonadotropic hypogonadism. These data indicate that most DAX1 missense mutations associated with classic AHC exhibit marked loss of function. The locations of these mutations thereby identify important functional domains in the carboxyl-terminus of the protein.
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PMID:Missense mutations cluster within the carboxyl-terminal region of DAX-1 and impair transcriptional repression. 1144 84

Coregulators have been suggested to act as a bridging apparatus between nuclear receptors and the transcriptional machinery. The orphan receptor SF-1 plays a role in controlling the basal and cAMP-stimulated expression of the human steroidogenic acute regulatory protein gene. DAX-1 is the gene responsible for X-linked adrenal hypoplasia congenita and blocks steroid biosynthesis by impairing the expression of steroidogenic acute regulatory protein. In the present study we examined the role of coregulators in the actions of SF-1 and DAX-1 on the human steroidogenic acute regulatory protein promoter. We found that the coregulator RIP 140 interacts with SF-1 in the yeast two-hybrid system. Glutathione-S-transferase pull-down assays and coimmunoprecipitations confirmed the interaction between RIP 140 and SF-1. RIP 140 was also shown to interact with DAX-1. When an RIP 140 expression vector was introduced into Y-1 cells, basal and cAMP-stimulated human steroidogenic acute regulatory protein promoter activities decreased. The inhibitory effect of RIP 140 on human steroidogenic acute regulatory protein promoter activity was dependent upon the presence of SF-1. The cAMP response of an SF-1 response element was inhibited by both RIP 140 and DAX-1 expression vectors at low concentrations of plasmids. We conclude that RIP 140 binds to the orphan nuclear receptor SF-1 and DAX-1 and modulates their actions on the human steroidogenic acute regulatory protein promoter.
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PMID:RIP 140 modulates transcription of the steroidogenic acute regulatory protein gene through interactions with both SF-1 and DAX-1. 1145 5

DAX-1, an X-linked member of the orphan nuclear receptor superfamily of transcription factors, plays a key role in sex determination and gonadal differentiation. Dax1-deficient male mice are infertile and have small testes despite normal serum levels of T and gonadotropins. Examination of Dax1-deficient testes reveals dilated seminiferous tubules and abnormal parameters of sperm fertilizing capability consistent with a possible obstruction in the testis. To test this hypothesis, we performed a comprehensive evaluation of the male reproductive tract in Dax1-deficient mice. Light and electron microscopic examination revealed the rete testis is blocked by aberrantly located Sertoli cells, creating a tailback of necrosing sperm in the testis. Sertoli cells also obstruct the proximal and middle efferent ductules, and this is accompanied by an overgrowth of the efferent duct epithelium. Seminiferous tubules close to the rete testis contain ectopic Leydig cells, distinct from the hyperplastic Leydig cells present in the interstitial space. The peritubular tissue surrounding these tubules is frequently abnormal, containing relatively undifferentiated myoid cells and no basement membrane between the myoid cells and Sertoli cells. A third of aged (>1-yr-old) Dax1-deficient male mice develop sex cord-stromal tumors, derived from cells of the Sertoli/granulosa cell or Leydig cell lineages. Combined, these observations reveal abnormal differentiation and proliferation of Leydig cells and Sertoli cells in Dax1-deficient male mice, leading to obstruction of the rete testis and infertility.
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PMID:Blockage of the rete testis and efferent ductules by ectopic Sertoli and Leydig cells causes infertility in Dax1-deficient male mice. 1156 14

Mutations in the orphan nuclear receptor DAX-1 cause X-linked adrenal hypoplasia congenita. Affected boys usually present with primary adrenal failure in early infancy or childhood. Impaired sexual development because of hypogonadotropic hypogonadism becomes apparent at the time of puberty. We report adult-onset adrenal hypoplasia congenita in a patient who presented with hypogonadism at 28 yr of age. Although he had no clinical evidence of adrenal dysfunction, compensated primary adrenal failure was diagnosed by biochemical testing. Semen analysis showed azoospermia, and he did not achieve fertility after 8 months of treatment with gonadotropins. A novel Y380D DAX-1 missense mutation, which causes partial loss of function in transient gene expression assays, was found in this patient. This case demonstrates that partial loss-of-function mutations in DAX1 can present with hypogonadotropic hypogonadism and covert adrenal failure in adulthood. Further, an important role for DAX-1 in spermatogenesis in humans is confirmed, supporting findings in the Dax1 (Ahch) knockout mouse.
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PMID:Hypogonadotropic hypogonadism as a presenting feature of late-onset X-linked adrenal hypoplasia congenita. 1178 20


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