Geneviève Jean

Molecular characterization of CTNS deletions in nephropathic cystinosis: development of a PCR-based detection assay.

Nephropathic cystinosis is an autosomal recessive disorder that is characterized by accumulation of intralysosomal cystine and is caused by a defect in the transport of cystine across the lysosomal membrane. Using a positional cloning strategy, we recently cloned the causative gene, CTNS, and identified pathogenic mutations, including deletions, that span the cystinosis locus. Two types of deletions were detected-one of 9.5-16 kb, which was seen in a single family, and one of approximately 65 kb, which is the most frequent mutation found in the homozygous state in nearly one-third of cystinotic individuals. We present here characterization of the deletion breakpoints and demonstrate that, although both deletions occur in regions of repetitive sequences, they are the result of nonhomologous recombination. This type of mechanism suggests that the approximately 65-kb deletion is not a recurrent mutation, and our results confirm that it is identical in all patients. Haplotype analysis shows that this large deletion is due to a founder effect that occurred in a white individual and that probably arose in the middle of the first millenium. We also describe a rapid PCR-based assay that will accurately detect both homozygous and heterozygous deletions, and we use it to show that the approximately 65-kb deletion is present in either the homozygous or the heterozygous state in 76% of cystinotic patients of European origin.

Congenital nephrotic syndrome of the Finnish type: linkage to the locus in a non-Finnish population.

Congenital nephrotic syndrome of the Finnish type (CNF) is inherited as an autosomal recessive trait. The biochemical basis of the disease is unknown, although a lesion in the glomerular basement membrane is strongly suggested. Recently, the CNF locus was assigned to chromosome 19q12–q13.1 on the basis of linkage analysis in Finnish families. The high incidence of the disease in Finland, as well as the demonstration of linkage disequilibrium in the Finnish study, strongly suggests a founder effect based on a common ancient mutation in this population. We confirm linkage of the CNF locus to the same chromosomal region in seven non-Finnish CNF families without evidence of linkage disequilibrium. Our results show that the same gene seems to be affected in both Finnish and non-Finnish CNF populations. However, in the latter the mutation-carrying chromosomes descend from different ancestors without evidence of a founder effect.

Altered Oxidative Metabolism, Motility, and Adherence in Phagocytic Cells from Cystinotic Children

ABSTRACT: The present study investigates whether the metabolic abnormalities in cystinotic cells could affect nonspecific immune responses. Lymphocytes showed normal antibody-dependent cellular cytotoxicity and natural killer activity. However, cystinotic polymorphonuclear and mononuclear phagocytes exhibited altered oxidative responses as monitored by a luminol dependent chemiluminescence (CL) assay. Both isolated polymorphonuclear and mononuclear phagocytes in the absence of stimuli showed significantly increased CL production which was not found when cells were tested directly within whole blood. CL responses to a panel of stimuli differed markedly according to the type of cells and agents tested. Indeed, isolated polymorphonuclear demonstrated increased CL responses to soluble but not particulate agents, whereas isolated mononuclear phagocytes and overall cell CL responses in whole blood were found to be within the normal range regardless of the type of stimulus used. We also studied some membrane related properties of phagocytic cells. Fc and C3b receptors were normally expressed as tested by erythrocyte-antibody and erythrocyte-antibody-complement rosette-forming cells. Nevertheless, cystinotic polymorphonuclear and mononuclear phagocytes presented decreased random and directed migrations in an under-agarose chemotaxis assay. Finally, cystinotic granulocytes showed an impaired adhesiveness in a nylon fiber assay.

Anti-OKT3 response following prophylactic treatment in paediatric kidney transplant recipients

The anti-OKT3 response was studied in 40 paediatric kidney transplant recipients receiving OTK3 as a prophylactic treatment in association with azathioprine and prednisone. Only 1 patient experienced a reversible acute rejection episode while receiving OKT3. OKT3 induced a rapid disappearance of CD3+ cells, but significant proportions of CD3+ cells reappeared before the end of the treatment in 14 patients. Wide variations in circulating OKT3 levels were observed and in only 50% of patients could stable circulating OKT3 levels be detected until discontinuation of treatment. Anti-OKT3 antibodies detected by the enzyme-linked immunosorbent assay (ELISA) (anti-idiotypic and anti-isotypic antibodies) developed in 91% of patients. Anti-idiotypic antibodies detected by the immunofluorescence inhibition test were found in the sera of 71% of patients, always when high titres of anti-OKT3 antibodies were detected by ELISA. As it has recently been shown that anti-idiotypic antibodies are associated with failure of subsequent OKT3 treatment, we conclude that OKT3 should be restricted to steroid-resistant rejection crises in paediatric patients.

Increased monocyte-dependent suppression of polyclonal activation of B lymphocytes from cystinotic children

In infantile cystinosis the amino acid cystine preferentially accumulates in phagocytic cells, polymorphonuclear leucocytes (PMN) and monocytes, rather than in lymphocytes. We previously described functional abnormalities in the oxidative metabolism and locomotion of cystinotic PMN and monocytes. The present study shows an abnormal lymphocyte polyclonal activation as evidenced by a decreased immunoglobulin (Ig) production and generation of Ig-containing cells (ICC) in cultures of peripheral blood mononuclear cells (PBMC) from cystinotic children upon stimultion with pokeweed mitogen andStaphylococcus aureus Cowan I. However, monocyte depletion from cystinotic PBMC fully reconstituted Ig production and ICC generation, indicating: (1) the presence of an increased monocyte-dependent suppression on lymphocyte polyclonal activation, and (2) that the intrinsic ability of cystinotic lymphocytes to respond to polyclonal stimulation was preserved. The increased cystinotic monocytedependent suppressive effect was not mediated by prostaglandin E2 (PGE2) since its production by cystinotic PBMC upon polyclonal activation was not different from that of controls. In addition, the sensitivity of cystinotic lymphocytes to the immunosuppressive effect of varying concentrations of exogenous PGE2 was similar to that of controls. Finally, indomethacin and 2-mercaptoethanol, two agents able to scavenge hydroxyl (OH) radicals, restored Ig production by cystinotic PBMC, suggesting a role for reactive oxygen species in the increased cystinotic monocyte-dependent suppression.

Altered Leukotriene Generation in Leukocytes from Cystinotic Children

ABSTRACT: Upon in vitro stimulation with 10 μM ionophore A 23187 for 5 min at 37°C, the generation of leukotriene (LT) C4 in polymorphonuclear leukocytes (PMNL) from nine untreated cystinotic children was significantly increased compared with that in eight control children (p < 0.01) and 25 normal adults (p < 0.001) (417.4 ± 70.0 versus 177.0 ± 30.9 and 164.9 ± 19.5 pmol/1 × 107 cells, respectively). Concomitantly with the increased generation of LTC4, LTB4 production in PMNL from untreated cystinotic children was decreased compared with controls, whereas the total amount of LTA4 derivatives was similar in the three groups. The increase in LTC4 production was not related to the number of eosinophils present in the PMNL preparations from cystinotic children, which was similar to that of control subjects. PMNL from cystinotic children treated with cysteamine, an aminothiol compound that decreases the intracellular cystine content, generated smaller amounts of LTC4 upon ionophore A 23187 stimulation than PMNL from untreated cystinotic children. In addition, abrogation of the cysteamine treatment for 3 or 4 d led to an increase in LTC4 production. These findings suggest that the metabolic abnormalities taking place in infantile cystinosis may favor the biosynthesis of LTC4 from PMNL.

Growth, free plasma and muscle amino-acids in uraemic rats fed various low-protein diets

The nutritional effects of low-protein diets are difficult to assess in humans. Normal and uraemic growing rats were therefore fed: a moderately low-protein (12%) reference diet (diet R), two 5% casein diets, one supplemented with essential amino acids (AA) (diet A) and the other with their keto acids (diet K), and a 7% casein diet isonitrogenous with diet K (diet L). Appetite and growth of both uraemic and control rats were identical on diets R and A and were reduced on diets K and L. Stunting was prominent in rats fed diet L and more severe than in those on diet K. Diet K induced marked anorexia in controls. This effect was smaller in uraemic rats, which were all anorectic, regardless of the diet. Plasma essential AA were similar in rats on diets R and A but low in control rats fed diets L and K. In particular, diet K did not improve the branchedchain AA levels although it produced better growth than diet L. Plasma and muscle threonine were surprisingly elevated in rats on the semi-synthetic diets A and K, despite identical or lower consumptions. Regardless of the diet, uraemia resulted in unchanged or increased plasma essential AA, despite reduced appetite and stunting. Uraemia caused a marked rise in some non-essential AA. Muscle essential AA, except for threonine, were essentially unaltered and did not correlate with growth or uraemia.

Highlights Plasma and Muscle Free Amino Acid Alteration in Uremic Children

Simultaneous assessment of plasma and muscle free amino acids (AA) has been performed in children in order to obtain more information about metabolic disturbances presumably related to growth retardation. Plasma and muscle were sampled after an overnight fast and amino acids were measured by ion exchange chromatography with five step lithium buffers.