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M Fellous

Publications and source records attributed to M Fellous.

At least 55 records · Page 3Linked to original sources
PubMed2000

[The Human Genome Project and the genetics of infertility].

Nine years after the beginning and five years before the expected end of the Human Genome Project, we will have access in several months to 90% of the human genome sequence. This data certainly opens promising vistas to the better understanding of gametogenesis. This will allow the different types of sterility to be studied through new approaches. The aim of the current review is to describe how the Human Genome Project has proceeded in the last ten years. We also discuss to what extent the knowledge of the human genome sequence is important in understanding the genetic basis of some diseases, such as human infertility. Finally, we review the different methodologies to use this information and their limits.

Ethics↗
PubMed1999

Sex determination and the Y chromosome.

Although SRY was first identified 10 years ago, we still know remarkably little about its mode of action or downstream target genes. Recently, potential protein partners have been identified and there has been considerable activity to understand the roles of WT1, SF-1, DAX-1 and SOX9 in gonadogenesis. The emerging picture is one of complex interactions, involving both positive and negative regulatory signals that, depending on the cellular and promoter context, drive the expression of male-specific genes. Despite recent advances, however, we are still unable to explain the genetic cause of most cases of 46,XY gonadal dysgenesis or even a single case of Y-chromosome-negative 46,XX maleness.

Animals↗
PubMed1999

High-resolution human/goat comparative map of the goat polled/intersex syndrome (PIS): the human homologue is contained in a human YAC from HSA3q23.

The genetic and cytogenetic map around the chromosome 1 region shown to be linked with polledness and intersexuality (PIS) in the domestic goat (Capra hircus) was refined. For this purpose, a goat BAC library was systematically screened with primers from human coding sequences, scraped chromosome 1 DNA, bovine microsatellites from the region, and BAC ends. All the BACs (n = 30) were mapped by fluorescence in situ hybridization (FISH) on goat chromosome 1q41-q45. The genetic mapping of 30 new goat polymorphic markers, isolated from these BACs, made it possible to reduce the PIS interval to a region of less than 1 cM on goat chromosome 1q43. The PIS locus is now located between the two genes ATP1B and COP, which both map to 3q23 in humans. Genetic, cytogenetic, and comparative data suggest that the PIS region is now probably circumscribed to an approximately 1-Mb DNA segment for which construction of a BAC contig is in progress. In addition, a human YAC contig encompassing the blepharophimosis-ptosis-epicanthus-inversus region was mapped by FISH to goat chromosome 1q43. This human disease, mapped to HSA 3q23 and affecting the development and maintenance of ovarian function, could be a potential candidate for goat PIS.

Animals↗
PubMed1999

The same mutation affecting the splicing of WT1 gene is present on Frasier syndrome patients with or without Wilms' tumor.

Denys-Drash and Frasier syndromes are rare human disorders that associate nephropathy with gonadal and genital abnormalities. In DDS there is a predisposition to Wilms' tumor. Heterozygous point mutations in the Wilms' tumor, type1 gene (WT1), particularly those altering the zinc finger (ZF) encoding exons, have been reported in most DDS patients, while mutations in intron 9 of the same gene cause FS. This paper describes two cases of DDS, one FS and one patient with Wilm's tumor and intersex genitalia, in which mutations were searched by sequencing the exons 8 and 9 of WT1 gene. Patient 1 carried a missense point mutation in exon 8 (ZF2), converting a CGA-Arg codon to a TGA-stop codon. Patient 2 presented a single nucleotide deletion within exon 9 (ZF3) introducing a premature chain termination at codon 398. Patients 3 and 4 had a C-->T transition at position +4 of the second alternative splice donor site of exon 9 (this mutation was detected in peripheral blood and in tumor derived DNA of patient 3). However, patient 3 had previously developed a Wilms' tumor. This is the first case of Wilms' tumor development in a phenotypically and genetically confirmed case of FS.

Adolescent↗
PubMed1999

A high frequency of Y chromosome deletions in males with nonidiopathic infertility.

Microdeletions of the long arm of the human Y chromosome are associated with spermatogenic failure and have been used to define three regions of Yq (AZFa, AZFb, and AZFc) that are recurrently deleted in infertile males. In a blind study we screened 131 infertile males (46 idiopathic and 85 nonidiopathic) for Y chromosome microdeletions. Nineteen percent of idiopathic males, with an apparently normal 46,XY chromosome complement had microdeletions of either the AZFa, AZFb, or AZFc region. There was no strict correlation between the extent or location of the deletion and the phenotype. The AZFb deletions did not include the active RBM gene. Significantly, a high frequency of microdeletions (7%) was found in patients with known causes of infertility and a 46,XY chromosome complement. These included deletions of the AZFb and AZFc regions, with no significant difference in the location or extent of the deletion compared with the former group. It is recommended that all males with reduced or absence sperm counts seeking assisted reproductive technologies be screened for deletions of the Y chromosome.

Adult↗
PubMed1999

The human SRY protein is present in fetal and adult Sertoli cells and germ cells.

Sex determination in mammals is controlled by the Y chromosome located SRY gene. Despite recent advances towards understanding the mechanisms that regulate sex determination in mammals, the expression profile of the SRY protein in human tissues is unknown. To localize the SRY protein and determine its cellular distribution, we prepared monoclonal antibodies (mAb) against the recombinant SRY protein. One antibody, LSRY1.1, recognizes a SRY-specific epitope and was used to localize the protein in different cells and tissues. The mAb recognizes a protein of 27 kDa in total lysates of HeLa SRYB3 cells. Immunocytochemical staining showed a nuclear localization of the protein. Immunohistochemical studies performed on gonadal tissue of a fetus, a one month-old boy and an adult man, demonstrated the presence of SRY protein in the nucleus of Sertoli and germ cells. In addition two 46,XX SRY(+) males had the SRY protein in their gonadal tissues. All other samples were negative, including all female tissue studied and the testis of a 46,XX SRY(-) male. The presence of SRY protein in fetal and adult gonadal tissues including germ cells suggests that SRY may have other male-specific functions in addition to sex determinism.

Adult↗
PubMed1999

[Genetic causes of male infertility].

In this review, after a brief summary of the spermatogenesis process, we present some genetic causes of male infertility at chromosome and gene level, known at present. Even though knowledge has greatly increased, in 15% of cases, we still do not know the infertility mechanism. The genotype-phenotype relationship remain ambiguous because of the diversity of the implicated mechanisms and their interactions. Other genes remain to be identified and, in the future, one of the main difficulties will be to define exactly the relationship between environmental factors and male infertility.

Environment↗
PubMed1998

Interferon alpha inhibits a Src-mediated pathway necessary for Shigella-induced cytoskeletal rearrangements in epithelial cells.

Shigella flexneri, the causative agent of bacillary dysentery, has the ability to enter nonphagocytic cells. The interferon (IFN) family of cytokines was found to inhibit Shigella invasion of cultured epithelial cells. We show here that IFN-alpha inhibits a Src-dependent signaling cascade triggered by Shigella that leads to the reorganization of the host cell cytoskeleton. Immunofluorescence studies showed that IFN-alpha inhibits Shigella-induced actin polymerization required for bacterial entry into cells. Phosphorylation of cortactin, a Src-substrate specifically tyrosyl-phosphorylated during Shigella entry, was inhibited by IFN-alpha. Overexpression of a dominant interfering form of pp60c-src led to inhibition of Shigella-induced cytoskeletal rearrangements and decreased cortactin phosphorylation indicating a role for Src in Shigella entry. Also, Shigella uptake in cells that expressed constitutively active Src was unaffected by IFN-alpha treatment. We conclude that Src kinase activity is necessary for Shigella invasion of epithelial cells and that IFN-alpha inhibits this Src-dependent signaling pathway.

Actins↗
PubMed1998

Specific contribution of Tyk2 JH regions to the binding and the expression of the interferon alpha/beta receptor component IFNAR1.

Cytokine signaling involves the activation of the Janus kinase (JAK) family of tyrosine kinases. These enzymes are physically associated with cytokine receptor components. Here, we sought to define the molecular basis of the interaction between Tyk2 and IFNAR1, a component of the interferon alpha/beta receptor, by delimiting a minimal IFNAR1 binding region in the Tyk2 protein. Using an in vitro assay system, we narrowed down the interaction domain to a region comprising the JH7 and part of the JH6 homology boxes (amino acids 22-221). When expressed in Tyk2-negative cells, the JH7-6 region was unable to stabilize IFNAR1 protein levels, a critical function that we previously attributed to the N region (amino acids 1-591) of Tyk2. Moreover, substitution of the JH7-JH6 domain in JAK1 with that of Tyk2 did not restore IFNAR1 level nor interferon alpha signaling in Tyk2-negative cells. Thus, the major interaction surface lies within JH7-6, but additional JH regions (JH5-4-3) contribute in a specific manner to the in vivo assembly of Tyk2 and IFNAR1. Evidence is also provided of the lack of specificity of the Tyk2 kinase-like and tyrosine kinase domains in interferon alpha/beta receptor signaling.

Amino Acid Sequence↗
PubMed1998

CIITA B-cell-specific promoter suppression in MHC class II-silenced cell hybrids.

In this study, various sets of somatic cell hybrids, generated by the fusion of epithelial cell lines with B-lymphoblastoid cell lines, were analyzed for the expression of major histocompatibility complex (MHC) class II antigens. We first demonstrate, in human and mouse intraspecies hybrids, the coordinate suppression of MHC class II, Ii (invariant chain) and HLA-DM gene transcription, and the release of the silencing by the addition of interferon gamma. Using interspecies hybrids, the segregation of human chromosomes allowed us to establish that MHC class II extinction is linked to the presence in the hybrids of the chromosomes from the epithelial fusion partner. Moreover, our data provide evidence that the expression pattern of MHC class II mRNA is correlated with that of the class II transactivator (CIITA), suggesting that CIITA is the actual target of the silencing. To gain further insight into the suppression phenomenon we performed luciferase assays which show that silencing affects the activity of the B-cell-specific promoter of CIITA. These results therefore demonstrate that the MHC class II gene silencing in somatic cell hybrids is due to an active suppression of one of the promoters of the CIITA gene, mediated by the epithelial cell fusion partner.

Animals↗
PubMed1998

Failure of testicular development associated with a rearrangement of 9p24.1 proximal to the SNF2 gene.

In 46,XY individuals, testes are determined by the activity of the SRY gene (sex-determining region Y), located on the short arm of the Y chromosome. The other genetic components of the cascade that leads to testis formation are unknown and may be located on the X chromosome or on the autosomes. Evidence for the existence of several loci associated with failure of male sexual development is indicated by reports of 46,XY gonadal dysgenesis associated with structural abnormalities of the X chromosome or of autosomes (chromosomes 9, 10, 11 and 17). In this report, we describe the investigation of a child presenting with multiple congenital abnormalities, mental retardation and partial testicular failure. The patient had a homogeneous de novo 46,XY,inv dup(9)(pter-->p24.1::p21.1-->p23.3::p24.1-->qter) chromosome complement. No deletion was found by either cytogenetic or molecular analysis. The SRY gene and DSS region showed no abnormalities. Southern blotting dosage analysis with 9p probes and fluorescent in situ hybridisation data indicated that the distal breakpoint of the duplicated fragment was located at 9p24.1, proximal to the SNF2 gene. We therefore suggest that a gene involved in normal testicular development and/or maintenance is present at this position on chromosome 9.

Adolescent↗
PubMed1998

The INSL4 gene maps close to WI-5527 at 9p24.1-->p23.3 clustered with two relaxin genes and outside the critical region for the monosomy 9p syndrome.

The insulin like growth factor 4 (INSL4) gene belongs to the insulin gene superfamily and has been mapped by fluorescent in situ hybridization to 9p24. Expression of INSL4, of unknown function, has been recently detected in the perichondrium and ligaments of the human embryo. Here we have mapped INSL4 within the framework of a partial YAC contig covering the distal part of 9p to find out whether this gene lies within the critical region defined for the monosomy 9p syndrome. The gene was also located using a human-rodent radiation hybrid panel. INSL4 was found to be distal to the del(9p) critical region and excluded as a candidate for the syndrome. In addition, the positions of two relaxin genes (RLN1, RLN2) that belong to the same superfamily as INSL4 and which have also been mapped to chromosome 9, were refined. We have shown that the three genes are clustered in the same region.

Animals↗
PubMed1997

The amino-terminal region of Tyk2 sustains the level of interferon alpha receptor 1, a component of the interferon alpha/beta receptor.

Tyk2 belongs to the Janus kinase (JAK) family of receptor associated tyrosine kinases, characterized by a large N-terminal region, a kinase-like domain and a tyrosine kinase domain. It was previously shown that Tyk2 contributes to interferon-alpha (IFN-alpha) signaling not only catalytically, but also as an essential intracellular component of the receptor complex, being required for high affinity binding of IFN-alpha. For this function the tyrosine kinase domain was found to be dispensable. Here, it is shown that mutant cells lacking Tyk2 have significantly reduced IFN-alpha receptor 1 (IFNAR1) protein level, whereas the mRNA level is unaltered. Expression of the N-terminal region of Tyk2 in these cells reconstituted wild-type IFNAR1 level, but did not restore the binding activity of the receptor. Studies of mutant Tyk2 forms deleted at the N terminus indicated that the integrity of the N-terminal region is required to sustain IFNAR1. These studies also showed that the N-terminal region does not directly modulate the basal autophosphorylation activity of Tyk2, but it is required for efficient in vitro IFNAR1 phosphorylation and for rendering the enzyme activatable by IFN-alpha. Overall, these results indicate that distinct Tyk2 domains provide different functions to the receptor complex: the N-terminal region sustains IFNAR1 level, whereas the kinase-like domain provides a function toward high affinity ligand binding.

Cell Line↗
PubMed1997

Conservation of Y chromosome-specific sequences immediately 5' to the testis determining gene in primates.

Sex is determined in mammals by the SRY gene, which is located on the non-recombining region of the Y chromosome. Although the presence of mutations in SRY associated with male to female sex reversal clearly indicates that this gene is essential for testis formation, little is known concerning other genes in this process or how the expression of SRY itself is controlled. This is mainly due to the absence of an appropriate in vitro cellular model. Previous studies have indicated that SRY coding sequences are undergoing rapid evolution in mammals. In this study, we cloned and compared a Y chromosome-specific region immediately 5' to the SRY open reading frame in several primate species. The divergence of the region 5' to SRY between primates was found to be comparable with that described for autosomal sequences. An alignment of sequences within the primate lineage, together with sequences from the cow and pig, revealed the presence of several highly conserved motifs. These domains may have a function in the control of SRY expression during fetal development.

Animals↗
PubMed1997

Identification of signalling components in tyrosine kinase cascades using phosphopeptide affinity chromatography.

Various methods are now available to identify the molecular partners of the component of a signal transduction pathway. Some interactions, however, can be technically difficult to detect because they depend upon transient tyrosine phosphorylation. Here, we present a simple affinity chromatography approach based on synthetic phosphopeptides to purify potential partners of phosphotyrosine-containing proteins. With this approach, we confirm the previously characterized interaction between Grb2 and the EGF receptor, and we identify novel partners of the IGF-1 receptor and of the JAK proteins. Methenyltetrahydrofolate synthetase (MTHFS) was identified as a potential mediator of IGF-1R dependent transformation. P85alpha, the regulatory subunit of PI3 kinase, was identified as one of four proteins recruited by a phosphopeptide mimicking a motif conserved in all JAK family members.

Adaptor Proteins, Signal Transducing↗