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Biomedical subjects

G de Saint Basile

Publications and source records attributed to G de Saint Basile.

At least 19 recordsLinked to original sources
PubMed2001

Spectrum of perforin gene mutations in familial hemophagocytic lymphohistiocytosis.

Familial hemophagocytic lymphohistiocytosis (FHL) is an autosomal recessive disease of early childhood characterized by nonmalignant accumulation and multivisceral infiltration of activated T lymphocytes and histiocytes (macrophages). Cytotoxic T and natural killer (NK) cell activity is markedly reduced or absent in these patients, and mutations in a lytic granule constituent, perforin, were recently identified in a number of FHL individuals. Here, we report a comprehensive survey of 34 additional patients with FHL for mutations in the coding region of the perforin gene and the relative frequency of perforin mutations in FHL. Perforin mutations were identified in 7 of the 34 families investigated. Six children were homozygous for the mutations, and one patient was a compound heterozygote. Four novel mutations were detected: one nonsense, two missense, and one deletion of one amino acid. In four families, a previously reported mutation at codon 374, causing a premature stop codon, was identified, and, therefore, this is the most common perforin mutation identified so far in FHL patients. We found perforin mutations in 20% of all FHL patients investigated (7/34), with a somewhat higher prevalence, approximately 30% (6/20), in children whose parents originated from Turkey. No other correlation between the type of mutation and the phenotype of the patients was evident from the present study. Our combined results from mutational analysis of 34 families and linkage analysis of a subset of consanguineous families indicate that perforin mutations account for 20%-40% of the FHL cases and the FHL 1 locus on chromosome 9 for approximately 10%, whereas the major part of the FHL cases are caused by mutations in not-yet-identified genes.

Amino Acid Substitution↗
PubMed2001

Mutations in severe combined immune deficiency (SCID) due to JAK3 deficiency.

During the last 10 years, an increasing number of genes have been identified whose abnormalities account for primary immunodeficiencies, with defects in development and/or function of the immune system. Among them is the JAK3-gene, encoding for a tyrosine kinase that is functionally coupled to cytokine receptors which share the common gamma chain. Defects of this gene cause an autosomal recessive form of severe combined immunodeficiency with almost absent T-cells and functionally defective B-cells (T(-)B(+) SCID). Herewith, we present molecular information on the first 27 unique mutations identified in the JAK3 gene, including clinical data on all of the 23 affected patients reported so far. A variety of mutations scattered throughout all seven functional domains of the protein, and with different functional effects, have been identified. Availability of a molecular screening test, based on amplification of genomic DNA, facilitates the diagnostic approach, and has permitted recognition that JAK3 deficiency may also be associated with atypical clinical and immunological features. Development of a structural model of the JAK3 kinase domain has allowed characterization of the functional effects of the various mutations. Most importantly, molecular analysis at the JAK3 locus results in improved genetic counseling, allows early prenatal diagnosis, and prompts appropriate treatment (currently based on hematopoietic stem cell transplantation) in affected families.

Genetic Counseling↗
PubMed2001

Eleven novel JAK3 mutations in patients with severe combined immunodeficiency-including the first patients with mutations in the kinase domain.

Defects of the JAK3-gene are known to cause an autosomal recessive form of severe combined immunodeficiency with almost absent T-cells and functionally defective B-cells (T-B+SCID). The JAK3 protein, an intracellular tyrosine kinase, is crucial for signal-transmission from the common gamma chain to the Signal Transducers and Activators of Transcription (STATs) that drive gene expression in the nucleus. We present nine novel patients with eleven distinct mutations (g.96A>G, g.268G>C, IVS12-1G>A, g.2046C>T, g.2160C>T, g.2175G>A, g.2187G>T, g.2391C>T, g.2406C>T, IVS18+3G>C) among them a mutation in the kinase domain (JH1: g.3167del). The clinical phenotype of the patients shows an unusually broad spectrum ranging from classical SCID to almost normal. In order to understand the complex genotype-phenotype correlation we studied expression and function (by IL-2 induced phosphorylation) of the newly identified and two other alleles with JH1 mutations we recently reported. We found the first mutation in the JH1-domain of JAK3, that precludes kinase activity (L910S). The two other JH1 mutations both caused a premature stop. One of them (C1024fsX1037) also abolished any phosphorylation of JAK3 and expression of the protein. The other mutation (Y1023X), affecting the last JH1 tyrosine, may allow for residual protein expression and phosphorylation. This may indicate that the part of the kinase region downstream Y1023, is not essential for the function of JAK3.

Alleles↗
PubMed2001

The role of cytotoxicity in lymphocyte homeostasis.

Several human inherited immune disorders lead to the same fatal lymphoproliferative syndrome, called the hemophagocytic syndrome. Through defective perforin expression or transport, these disorders highlight the determinant role of the secretory cytotoxic pathway in the regulation of the immune response and in lymphocyte homeostasis. In addition, new effectors of this secretory pathway have been identified.

Animals↗
PubMed2000

Gene therapy of human severe combined immunodeficiency (SCID)-X1 disease.

Severe combined immunodeficiency-X1 (SCID-X1) is an X-linked inherited disorder characterized by an early block in T and natural killer (NK) lymphocyte differentiation. This block is caused by mutations of the gene encoding the gammac cytokine receptor subunit of interleukin-2, -4, -7, -9, and -15 receptors, which participates in the delivery of growth, survival, and differentiation signals to early lymphoid progenitors. After preclinical studies, a gene therapy trial for SCID-X1 was initiated, based on the use of complementary DNA containing a defective gammac Moloney retrovirus-derived vector and ex vivo infection of CD34+ cells. After a 10-month follow-up period, gammac transgene-expressing T and NK cells were detected in two patients. T, B, and NK cell counts and function, including antigen-specific responses, were comparable to those of age-matched controls. Thus, gene therapy was able to provide full correction of disease phenotype and, hence, clinical benefit.

Antigens, CD34↗
PubMed2000

Two genes are responsible for Griscelli syndrome at the same 15q21 locus.

Griscelli syndrome is a rare autosomal recessive disease characterized by pigment dilution, variable cellular immunodeficiency, and an acute phase of uncontrolled T lymphocyte and macrophage activation. We previously mapped the disease locus to 15q21 and showed that a MyoVa gene (HGMW-approved symbol MYO5A) defect leads to Griscelli syndrome. We report a second MyoVa mutation in a new patient, confirming this first finding. However, in four other Griscelli syndrome patients analyzed, the MYOVA protein is expressed, and no mutation can be detected in the MyoVa gene coding sequence, even in the alternatively spliced region for which exon-intron boundaries were characterized. Linkage analysis performed in 15 Griscelli families thus far studied confirms the first localization. However, fine haplotype analysis in three families strongly suggests the existence of a second gene at the same locus for Griscelli syndrome less than 7.3 cM distant from the MyoVa gene.

Alternative Splicing↗
PubMed2000

Protein truncation test of LYST reveals heterogenous mutations in patients with Chediak-Higashi syndrome.

Chediak-Higashi syndrome (CHS) is a rare autosomal recessive disorder in which an immune deficiency occurs in association with pigmentation abnormalities. Most patients who do not undergo bone marrow transplantation die of a lymphoproliferative syndrome, though some patients with CHS have a relatively milder clinical course of the disease. The large size of the LYST gene, defective in CHS, has made it difficult to screen for mutations in a large number of patients. Only 8 mutations have been identified so far, and all lead to a truncated LYST protein. We conducted protein truncation tests on this gene in 8 patients with CHS. Different LYST mutations were identified in all subjects through this approach, strengthening the observation of a high frequency of truncated LYST proteins as the genetic cause of CHS.

Adolescent↗
PubMed2000

Diversity, functionality, and stability of the T cell repertoire derived in vivo from a single human T cell precursor.

In this report, we have analyzed the human T cell repertoire derived in vivo from a single T cell precursor. A unique case of X-linked severe combined immunodeficiency in which a reverse mutation occurred in an early T cell precursor was analyzed to this end. It was determined that at least 1,000 T cell clones with unique T cell receptor-beta sequences were generated from this precursor. This diversity seems to be stable over time and provides protection from infections in vivo. A similar estimation was obtained in an in vitro murine model of T cell generation from a single cell precursor. Overall, our results document the large diversity potential of T cell precursors and provide a rationale for gene therapy of the block of T cell development.

Child, Preschool↗
PubMed2000

Founder effect for a 26-bp deletion in the RFXANK gene in North African major histocompatibility complex class II-deficient patients belonging to complementation group B.

Expression of major histocompatibility complex (MHC) class II genes is controlled at the transcriptional level by at least four trans-acting genes, CIITA, RFXANK, RFX5, and RFXAP. Defects in these regulatory genes result in the absence of MHC class II molecule expression and, thereby, cause a combined immunodeficiency. MHC class II deficiency is inherited as an autosomal recessive trait. Since the first description of the disease, about 70 patients from 50 families have been reported. Forty-three of these families have been classified into four complementation groups: A, B, C, and D. In the largest group, B, the majority of patients are of North African origin. In two of these patients, the same mutation in the RFXANK gene (752delG-25) was identified. We performed a mutation analysis in 20 additional patients belonging to complementation group B and detected the 752delG-25 mutation in 17. All of these patients are of North African origin. A founder effect for this mutation was documented, since all tested patients, except one, display a common haplotype spanning the RFXANK locus.

Africa, Northern↗
PubMed2000

Gene therapy of severe combined immunodeficiencies.

Primary immunodeficiency diseases (PID) are attractive candi dates for a gene therapy approach because many of these disorders convey a poor prognosis while a number of the genes mutated in these conditions have been identified. Gene transfer into hematopoietic stem cells (HSC) should, in theory, lead to a cure of the disease. There are, however, a number of limitations mostly related to the failure of clinically available vectors to enable transgene integration into HSC. Nevertheless PID due to a gene defect leading to failure of cell development could be amenable to gene therapy given the selective advantage conferred to transgene expression in progenitor cells. Terminally differentiated cells are, however, long lived, as is the case for T lymphocytes. This concept led to the first gene therapy trials for adenosine deaminase (ADA) deficiency several years ago. Results were in part disappointing mostly because of the concomitant substitutive treatment by polyethylene glycol-ADA. However, recent application to X-linked severe combined immunodeficiency (gamma(c) deficiency) turned out to be efficient at least on a relatively short term basis (i.e. one year so far). These results demonstrate that this concept is valid and can be the basis for the treatment of other forms of severe T-cell immunodeficiencies. Obviously, development of vectors (lentiviruses) able to efficiently target HSC could in the future considerably enlarge the field of PID treatable by gene transfer.

Animals↗
PubMed2000

Mutations in RAB27A cause Griscelli syndrome associated with haemophagocytic syndrome.

Griscelli syndrome (GS, MIM 214450), a rare, autosomal recessive disorder, results in pigmentary dilution of the skin and the hair, the presence of large clumps of pigment in hair shafts and an accumulation of melanosomes in melanocytes. Most patients also develop an uncontrolled T-lymphocyte and macrophage activation syndrome (known as haemophagocytic syndrome, HS), leading to death in the absence of bone-marrow transplantation. In contrast, early in life some GS patients show a severe neurological impairment without apparent immune abnormalities. We previously mapped the GS locus to chromosome 15q21 and found a mutation in a gene (MYO5A) encoding a molecular motor in two patients. Further linkage analysis suggested a second gene associated with GS was in the same chromosomal region. Homozygosity mapping in additional families narrowed the candidate region to a 3.1-cM interval between D15S1003 and D15S962. We detected mutations in RAB27A, which lies within this interval, in 16 patients with GS. Unlike MYO5A, the GTP-binding protein RAB27A appears to be involved in the control of the immune system, as all patients with RAB27A mutations, but none with the MYO5A mutation, developed HS. In addition, RAB27A-deficient T cells exhibited reduced cytotoxicity and cytolytic granule exocytosis, whereas MYO5A-defective T cells did not. RAB27A appears to be a key effector of cytotoxic granule exocytosis, a pathway essential for immune homeostasis.

B-Lymphocytes↗
PubMed2000

Gastric adenocarcinoma in a patient with X-linked agammaglobulinaemia.

Patients with primary immunodeficiencies are at high risk for developing haematological malignancies and, to a lesser degree, carcinoma. We report a patient with ascertained X-linked agammaglobulinaemia who developed a gastric carcinoma involving the distal part of the stomach associated with chronic atrophic gastritis and intestinal metaplasia. These latter conditions are considered to be precursor conditions and the role of chronic infections is likely. Patients with X-linked agammaglobulinaemia, as with other primary immunodeficiencies, could benefit from regular gastrointestinal evaluation, leading to early diagnosis and treatment of carcinoma.

Adenocarcinoma↗
PubMed2000

[Gene therapy for immune deficiencies].

Gene therapy offers an attractive option to the most severe forms of primary immunodeficiency diseases. Identification of disease associated genes as well as advances in the technology of gene transfer into hematopoietic progenitor cells have set the basis for the first clinical trials. Settings characterized by the potential for a selective advantage provided to transduced cells are the first diseases to target. The recent example of successful treatment of Severe Combined Immunodeficiency-X1 (gamma c deficiency) illustrates this potential.

Genetic Therapy↗
PubMed1999

Perforin gene defects in familial hemophagocytic lymphohistiocytosis.

Familial hemophagocytic lymphohistiocytosis (FHL) is a rare, rapidly fatal, autosomal recessive immune disorder characterized by uncontrolled activation of T cells and macrophages and overproduction of inflammatory cytokines. Linkage analyses indicate that FHL is genetically heterogeneous and linked to 9q21.3-22, 10q21-22, or another as yet undefined locus. Sequencing of the coding regions of the perforin gene of eight unrelated 10q21-22-linked FHL patients revealed homozygous nonsense mutations in four patients and missense mutations in the other four patients. Cultured lymphocytes from patients had defective cytotoxic activity, and immunostaining revealed little or no perforin in the granules. Thus, defects in perforin are responsible for 10q21-22-linked FHL. Perforin-based effector systems are, therefore, involved not only in the lysis of abnormal cells but also in the down-regulation of cellular immune activation.

Antigen-Presenting Cells↗
PubMed1999

Defective CTLA-4 cycling pathway in Chediak-Higashi syndrome: a possible mechanism for deregulation of T lymphocyte activation.

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4, also known as CD152) has been shown to play a major role in the regulation of T cell activation. Its membrane expression is highly regulated by endocytosis and trafficking through the secretory lysosome pathway. Chediak-Higashi syndrome (CHS) is an inherited disorder caused by mutations in the lysosomal trafficking regulator gene, LYST. It results in defective membrane targeting of the proteins present in secretory lysosomes, and it is associated with a variety of features, including a lymphoproliferative syndrome with hemophagocytosis. The murine equivalent of CHS, beige mice, present similar characteristics but do not develop the lymphoproliferative syndrome. We show herein that CTLA-4 is present in enlarged, abnormal vesicles in CHS T cells and is not properly expressed at the cell surface after T cell activation, whereas its surface expression is not impaired. It is therefore proposed that the defective surface expression of CTLA-4 by CHS T cells is involved in the generation of lymphoproliferative disease. This observation may provide insight into the role of CTLA-4 in humans.

Abatacept↗