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S Lumbroso

Publications and source records attributed to S Lumbroso.

At least 55 records · Page 3Linked to original sources
PubMed1994

Molecular prenatal diagnosis of partial androgen insensitivity syndrome based on the Hind III polymorphism of the androgen receptor gene.

OBJECTIVE: Partial androgen insensitivity syndromes are the cause of genital ambiguity that is at times quite severe; there is, therefore, a high demand for prenatal diagnosis in families already afflicted with this syndrome. When the mutation has not been identified, the diagnosis can be made by the study of the polymorphisms of the androgen receptor gene. To perform molecular prenatal diagnosis in a family with partial androgen insensitivity syndrome, we studied the Hind III polymorphism of the androgen receptor gene on the trophoblastic DNA. The use of this restriction fragment length polymorphism tracked maternal X chromosome segregation and established prenatal diagnosis although the mutation had not yet been identified in this family. FAMILY: The mother had been previously described as heterozygous for the Hind III polymorphism and chromosomal segregation analysis showed that the affected allele was associated with the 6.7-kb Hind III fragment. MEASUREMENTS: Hind III RFLP with an androgen receptor gene cDNA probe was realized on the trophoblastic DNA, along with measurement of androgen binding activity on the trophoblastic cells. RESULTS: We detected the presence of the 6.7-kb fragment in the DNA of the trophoblastic cells suggesting the fetus was affected. Partial androgen insensitivity syndrome was confirmed by a considerable decrease in androgen binding activity on the trophoblastic cells and by sonography of the fetus. After a therapeutic abortion requested by the parents, the diagnosis was confirmed by clinical examination of the fetus, biochemical analyses of the fetal androgen receptor, and molecular studies of the fetal DNA. CONCLUSIONS: When the mutation of the androgen receptor gene has not been identified, Hind III polymorphism of the trophoblastic DNA is useful in the prenatal diagnosis of androgen insensitivity syndrome in high-risk families.

Androgens↗
PubMed1994

Molecular prenatal exclusion of familial partial androgen insensitivity (Reifenstein syndrome)

In a large family with Reifenstein syndrome, we previously performed molecular analysis of the androgen receptor gene. Direct sequencing showed a G-A point mutation at position 2818 of exon 7, which was responsible for an arginine-histidine substitution at position 840 of the androgen receptor. In this family, the proband's mother became pregnant and wished to know whether she was carrying an unaffected fetus. Polymerase chain reactions of the sex-determining region of the Y chromosome (the SRY gene) on trophoblastic DNA at week 14 revealed a 46,XY genotype. Sequencing analysis showed the canonical sequence (CGT, encoding an Arg residue), suggesting that the fetus was not affected. The expectation of normal male sexual development was confirmed by detection of normal male external genitalia through ultrasonography at week 24. These data confirm that sequence analysis of the androgen receptor gene on trophoblastic DNA is the most reliable method for prenatally diagnosing or excluding androgen insensitivity syndrome in high-risk families.

Base Sequence↗
PubMed1994

Molecular genetics of androgen insensitivity syndromes.

The androgen receptor belongs to the family of nuclear receptors and contains three functional domains: a carboxy-terminal hormone binding region, a central cystein rich DNA binding region and an amino-terminal region involved in the expression of androgen regulated genes. Cloning of the complementary DNA encoding the androgen receptor enabled the characterization of the molecular defects associated with androgen insensitivity syndromes, X-linked disorders resulting from androgen action defects in target cells. Moreover, androgen receptor gene alterations have been recently described in two unrelated diseases: male breast cancer and spinal and bulbar muscular atrophy. Our group have identified 16 androgen receptor gene alterations in patients with androgen insensitivity syndrome, an amino acid substitution in a patient with a partial androgen insensitivity syndrome and a breast cancer. In 2 families, the molecular diagnosis of spinal and bulbar muscular atrophy has been performed.

Base Sequence↗
PubMed1994

[Genes of the Y chromosome and Turner syndrome].

Turner syndrome is a complex human phenotype most commonly seen in association with a 45,X karyotype and it has been proposed that the phenotype is the result of monosomy for genes common to the X and Y chromosomes. Detection of unrecognized Y derived material is now possible by PCR of the SRY gene. Its presence is correlated with the presence of testicular tissue, known to increase the risk of developing gonadal neoplasia. Study of Y chromosome allowed the localisation of a candidate gene for the development of gonadoblastoma, GBY. Moreover, some groups described genes on the Y chromosome whose defects seem to be involved in the development of Turner stigmata: ZFY and RPS4Y. In conclusion; molecular genetics of the Y chromosome develops new pathophysiological and fundamental perspectives of the molecular genetics of the Turner syndrome.

Chromosome Mapping↗
PubMed1993

Complete androgen insensitivity syndrome associated with a de novo mutation of the androgen receptor gene detected by single strand conformation polymorphism.

In a French child with complete androgen insensitivity syndrome and negative receptor-binding, no gross deletion has been found. Using single-strand conformation polymorphism assay, a useful screening method for rapid detection of DNA sequence alterations, and direct DNA sequencing, a G-T nucleotide substitution in exon 5 of the androgen receptor gene at nucleotide 2590 was found. This changed codon 743, glycine to valine, in the hormone-binding domain and created a new recognition sequence for the restriction endonuclease Asp HI. Amplification of exon 5 by polymerase chain reaction followed by digestion with Asp HI enabled easy recognition of the described mutation. Since the mother's exon 5 was undigested, we suspected the de novo nature of this nucleotide substitution. This was confirmed by direct sequencing of the mother's DNA which only showed the canonical sequence. To our knowledge, there has been no previous report of a de novo mutation described within the androgen receptor gene in patients with androgen insensitivity syndrome.

Amino Acid Sequence↗
PubMed1993

Mutations of androgen receptor gene in androgen insensitivity syndromes.

The androgen receptor belongs to the family of steroid-thyroid hormone-retinoid nuclear receptors. It contains 3 major domains: a hormone-binding region, a DNA-binding region and an amino-terminal region. Cloning of the cDNA encoding the androgen receptor and elucidation of the androgen receptor gene structure enabled the characterization of the molecular defects associated with androgen insensitivity. Mutations of the androgen receptor in 46,XY individuals cause a spectrum of androgen insensitivity syndromes, ranging from female phenotype (testicular feminization) to minor degrees of undervirilization or infertility. Reports on androgen receptor gene structure in patients with complete or partial forms of androgen insensitivity demonstrate that gene deletions are very rare. Several categories of mutations have been reported and are reviewed in this paper. Nucleotide substitutions in the androgen-binding domain or the N-terminal region that cause insertion of premature termination codons result in failure to form a functional protein. Missense mutations within the androgen-binding domain are responsible for a decrease or absence of receptor-binding activity. Mutations within the DNA-binding domain are associated with a positive receptor-binding form of androgen insensitivity. Analysis of described mutations indicates that they are spread throughout the gene, either associated with partial or complete androgen insensitivity. Furthermore, the same point mutation was reported to be associated with variable phenotypic expression of androgen insensitivity syndrome. It is thus difficult to define a genotype/phenotype relationship. However, mutations causing androgen insensitivity will certainly yield important new insights into the molecular basis of androgen action.

Androgen-Insensitivity Syndrome↗
PubMed1993

A new mutation within the deoxyribonucleic acid-binding domain of the androgen receptor gene in a family with complete androgen insensitivity syndrome.

OBJECTIVE: To study the androgen receptor gene in a large kindred with complete androgen insensitivity syndrome and positive receptor-binding activity. DESIGN: Enzymatic amplification coupled with single strand conformation polymorphism and DNA sequencing were used. RESULTS: In all the affected members, single strand conformation polymorphism showed a mobility shift in exon 2, suggesting a sequence alteration. Sequencing identified a valine into phenylalanine substitution at position 581 in the first zinc finger of the DNA-binding domain. CONCLUSIONS: This valine 581 is conserved in all nuclear receptors and has an important role for the recognition of the androgen response elements by the activated androgen receptor. This amino acid substitution has not been previously described in the androgen receptor in patients with androgen insensitivity syndrome. Moreover, single strand conformation polymorphism allowed determination of the generation in which the mutation appeared and performance of carrier diagnosis in this family.

Amino Acid Sequence↗
PubMed1993

Androgen receptor gene mutation in male breast cancer.

We screened thirteen male breast cancers for the presence of germline mutations in exons 2 and 3 encoding the DNA-binding domain of the androgen receptor. These two exons were amplified from genomic DNA extracted from patients' white blood cells. In one of these thirteen patients, single strand conformation polymorphism and direct sequencing detected a guanine-adenine point mutation at nucleotide 2185 that changes Arg608 into Lys in a highly conserved region of the second zinc finger of the androgen receptor. This mutation occurred in a 38 year old man with partial androgen insensitivity syndrome and normal androgen-binding capacity in cultured genital skin fibroblasts. To our knowledge, only one germline Arg to Gln androgen receptor gene mutation has been previously reported at position 607 in male breast cancer. This androgen receptor mutation along with the Arg608 into Lys mutation we describe, suggests that this genetic abnormality is not fortuitous: a decrease in androgen action within the breast cells could account for the development of male breast cancer by the loss of a protective effect of androgens on these cells. Activation of estrogen regulated genes by the change of DNA-binding characteristics of the mutant androgen receptor cannot, however, be ruled out.

Adult↗
PubMed1993

Increased oestradiol level in seminal plasma in infertile men.

Seminal hormonal patterns in fertile and infertile men were investigated. Follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin, testosterone and oestradiol were assessed by radioimmunoassay, and dehydroepiandrosterone sulphate (DHAS) by bioluminescence assay, on blood and seminal plasma of 23 fertile men and 83 infertile men. For fertile men, mean FSH, LH, testosterone and DHAS concentrations were lower and mean oestradiol was higher in seminal than in blood plasma; prolactin did not differ. For infertile men, mean seminal FSH and LH showed a moderate but significant increase compared with fertile men; testosterone, DHAS and prolactin did not differ but mean seminal oestradiol was significantly increased. Of the infertile men, 53% had seminal oestradiol concentration above the 90th percentile value for fertile men. The meaning of this seminal oestradiol increase is unclear since it is not known whether it is the cause or the consequence of the alteration of spermatogenesis in infertile men. Further studies are required to explore the possible therapeutic implications.

Dehydroepiandrosterone↗
PubMed1993

[Familial form of partial androgen insensitivity (Reifenstein syndrome): arginine-histidine mutation in position 840 in the androgen receptor].

In a large kindred with Reifenstein syndrome, we performed the molecular analysis of the androgen receptor gene. Since the biochemical characteristics of the androgen receptor, determined on the cultured genital skin fibroblasts, showed a drastic decrease of the androgen binding capacity, we assumed that a point mutation was located in exons 4-8 encoding the carboxy-terminal domain of the receptor. Enzymatic amplifications of these exons did not point out any deletions. Direct sequencing showed a G-A point mutation at position 2818 of exon 7 responsible for an arginine-histidine substitution at position 840 of the androgen receptor. The presence of the same mutation has been reported by other groups in four unrelated patients. Its association with different phenotypes of androgen insensitivity and different biochemical characteristics of the androgen receptor pointed out the complexity of the genotype-phenotype relationship in androgen insensitivity. Moreover the identification of the point mutation gave us the opportunity to perform a prenatal exclusion diagnosis of Reifenstein syndrome in this high-risk family.

Arginine↗
PubMed1992

Prenatal prediction of androgen insensitivity syndrome using exon 1 polymorphism of the androgen receptor gene.

Exon 1 polymorphism of the androgen receptor (AR) gene is characterized by a (CAG)n(CAA) repeat at position 172 following the translation start codon. The aim of this study was to determine whether AR gene exon 1 polymorphism could be used to perform prenatal diagnosis in high risk families with complete or partial androgen insensitivity syndrome. After enzymatic amplification of a 1 kilobase exon 1 fragment, each DNA was simultaneously digested by MspI and PstI restriction enzymes. After electrophoresis on a 15% electrophoresis on a 15% acrylamide gel or a 6% Nusieve gel, we measured the size of the obtained fragments and determined the number of CAG repeats since a 282 basepair fragment corresponds to 21 CAG. We previously showed that the number of CAG repeats within the AR gene exon 1 in 23 families with complete or partial androgen insensitivity syndrome was 19 +/- 4. By this method, we detected heterozygosity in 50% of the mothers. We present here 2 exclusion prenatal diagnoses using exon 1 polymorphism of the AR gene. Family A presented a boy with a severe form of partial androgen insensitivity syndrome. The mother had 2 uncles with ambiguous genitalia. In family B, the affected child had a complete androgen insensitivity syndrome. In both families, analysis of the AR gene exon 1 polymorphism of the trophoblastic DNA showed the presence of the normal maternal X chromosome. The parents decided to carry on the gestation. In family A, the newborn had normal male external genitalia. In family B, sonography confirmed the presence of normal male external genitalia. These data suggest that exon 1 polymorphism of the AR gene could be prenatally used to predict androgen insensitivity syndrome.

Androgens↗
PubMed1992

Molecular biology of disorders of sex differentiation.

Sexual ambiguity can be a difficult and sometimes confusing diagnostic problem in children. Recent developments in molecular biology have provided the opportunity to analyze the gene responsible for testicular determination, SRY, the androgen receptor gene and the gene encoding the cP450 enzyme specific for 21-hydroxylation, CYP21B, whose defects are responsible for congenital adrenal hyperplasia. Southern-blotting studies and PCR analyses of SRY, androgen receptor and CYP21B genes can be routinely used for the direct diagnosis of gonadal dysgenesis, androgen insensitivity syndromes and congenital adrenal hyperplasia, respectively. In sex-reversed XY females, several de novo mutations or deletions in the SRY gene have been reported. Defects in the human androgen receptor cause a spectrum of defects in male phenotypic sexual development associated with abnormalities in the receptor protein. Analyses of the androgen receptor gene structure have identified the causative mutation in some families: mutations that result in large-scale alterations of the structure of the androgen receptor, mRNA or gene mutations that alter the primary structure of the androgen receptor protein and mutations that alter the level of mRNA. The diversity of clinical phenotypes, apparent in 21-hydroxylase deficiency, is paralleled by a considerable degree of mutational heterogeneity in the CYP21 gene locus. Various changes causing severe 21-hydroxylase deficiency have been reported: point mutations, gene conversions and gene deletions. In conclusion, substantial progress has been made elucidating genetic defects causing sex reversal in XY females, the androgen insensitivity syndrome and congenital adrenal hyperplasia. Molecular genetics can also be applied for carrier identification and prenatal diagnosis.

Disorders of Sex Development↗
PubMed1991

[Androgen receptor gene polymorphism analysis: application to screening of heterozygote and to prenatal diagnosis of androgen insensitivity syndrome].

Androgen insensitivity syndromes are X-linked disorders. Restriction fragment length polymorphism analysis of the androgen receptor gene showed that deletions were infrequent. Some mutations have been described. In these conditions, in high-risk family, carrier diagnosis is impossible unless identification of mutations is made. It is thus necessary to detect androgen receptor gene polymorphism in order to differentiate the two maternal X chromosomes. Two androgen receptor gene polymorphisms have been reported (Hind III and exon 1). In this study we analyzed these two gene polymorphisms to detect carriers in at-risk families. The combined results of the two analyses allowed us to detect carriers in 45% of the studied families. In two families the prenatal diagnosis of androgen insensitivity syndrome was performed.

Deoxyribonuclease HindIII↗
PubMedDate not supplied

Disorders linked to insufficient androgen action in male children.

Virilization of the external genitalia in the male fetus requires testosterone and dihydrotestosterone (DHT), which is formed from testosterone by the action of the enzyme, 5alpha-reductase type 2 (5alphaR-2). Mediation of the effects of both testosterone and DHT requires a functional androgen receptor (AR) located in the cytoplasmic compartment of target cells. DHT (or testosterone) binding induces a conformational change which facilitates AR nuclear transport, phosphorylation and dimerization, ultimately regulating of the rate of transcription of androgen-dependent genes. Any event which impairs DHT formation (mutation within the 5alphaR-2 gene or 5alphaR-2 inhibitors) or normal function of the AR (mutation in the AR gene, antiandrogens) may result in insufficient androgen action in the male fetus and in subsequent undervirilization in the newborn. Hypospadias may be due to a defect in androgen action due to mutation of the 5alphaR-2 or of the AR gene. Mutation of unidentified genes is likely to underlie this displacement of the urethral meatus from the tip to the ventral side of the phallus. An aetiological role for environmental chemical products has been postulated, since ethnic as well as geographical differences in the incidence of hypospadias have been noted. Increasing evidence has been gathered indicating that widely used industrial and agricultural chemicals have deleterious effects on normal male sexual differentiation. Cryptorchidism and micropenis may represent an intersex phenotype, even if they are isolated. Aetiological factors include 5alphaR-2 gene mutation, AR gene mutation or environmental hormonal disruptors. In conclusion, several phenotypes have been attributed to insufficient androgen action during fetal life. Whereas mutations in the 5alphaR-2 gene and AR gene are natural, attention should be focused on environmental endocrine disruptors that are able to mimic steroid 5alpha-reductase deficiency or partial androgen insensitivity syndrome.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗