[Atypical manifestations in familial type 1 Waardenburg syndrome]

BACKGROUND

Waardenburg syndrome is an uncommon genetic disorder. Four clinical types are recognized. Three responsible genes have been identified (PAX 3: for type I syndrome, MITF and EDN3 for types II and IV respectively).

CASE REPORT

We report the case of a patient with Waardenburg type I morphotype who had atypical neurological manifestations. Decisive elements for diagnosis were the presence of Waardenburg syndrome in the family and, in affected kin, a mutation causing a shift in PAX 3 gene reading.

DISCUSSION

This case confirms the variability of Waardenburg signs within one family. The association of unusual neurological manifestations in the proband suggested that Vogt Koyanagi Harada disease may have been associated and may show some relationship with familial Waardenburg syndrome.

New mutations in the X-linked form of Charcot-Marie-Tooth disease

Mutations in the gene for connexin 32 are associated with a chromosome X-linked form of Charcot-Marie-Tooth disease. The prevalence of this form is probably underestimated. We screened 12 candidate families and found 7 missense mutations of which 4 are new. These mutations are located in intra- and extramembraneous parts of the protein. Some mutations are probably present with a higher frequency. This study further confirms variation of connexin 32 mutations with scarcity in the second transmembrane domain and, so far, absence in the fourth transmembrane domain and in the carboxy-terminal region.

Retinal-specific guanylate cyclase gene mutations in Leber's congenital amaurosis

Leber's congenital amaurosis (LCA, MIM 204,000), the earliest and most severe form of inherited retinopathy, accounts for at least 5% of all inherited retinal dystrophies. This autosomal recessive condition is usually recognized at birth or during the first months of life in an infant with total blindness or greatly impaired vision, normal fundus and extinguished electroretinogram (ERG). Nystagmus (pendular type) and characteristic eye poking are frequently observed in the first months of life (digito-ocular sign of Franceschetti). Hypermetropia and keratoconus frequently develop in the course of the disease. The observation by Waardenburg of normal children born to affected parents supports the genetic heterogeneity of LCA. Until now, however, little was known about the pathophysiology of the disease, but LCA is usually regarded as the consequence of either impaired development of photoreceptors or extremely early degeneration of cells that have developed normally. We have recently mapped a gene for LCA to chromosome 17p13.1 (LCA1) by homozygosity mapping in consanguineous families of North African origin and provided evidence of genetic heterogeneity in our sample, as LCA1 accounted for 8/15 LCA families in our series. Here, we report two missense mutations (F589S) and two frameshift mutations (nt 460 del C, nt 693 del C) of the retinal guanylate cyclase (RETGC, GDB symbol GUC2D) gene in four unrelated LCA1 probands of North African ancestry and ascribe LCA1 to an impaired production of cGMP in the retina, with permanent closure of cGMP-gated cation channels.

Prenatal diagnosis in congenital erythropoietic porphyria by metabolic measurement and DNA mutation analysis

Identification of uroporphyrinogen III synthase (UROIIIS) gene mutations in patients with congenital erythropoietic porphyria (CEP) allows fast and reliable carrier detection and prenatal diagnosis. We describe here the first case of prenatal diagnosis by concomitant measurement of uroporphyrin I in amniotic fluid and direct detection of the gene mutation. A French couple, whose first child was diagnosed with CEP, requested prenatal diagnosis at 16 weeks of gestation. Uroporphyrin I was dramatically increased in amniotic fluid and the fetus was homozygous for the C73R mutation, the most common mutation in this disease. The pregnancy was then terminated.

Structural analysis of the RH-like blood group gene products in nonhuman primates

Rh-related transcripts present in bone marrow samples from several species of nonhuman primates (chimpanzee, gorilla, gibbon, crab-eating macaque) have been amplified by RT-polymerase chain reaction using primers deduced from the sequence of human RH genes. Nucleotide sequence analysis of the nonhuman transcripts revealed a high degree of similarity to human blood group Rh sequences, suggesting a great conservation of the RH genes throughout evolution. Full-length transcripts, potentially encoding 417 amino acid long proteins homologous to Rh polypeptides, were characterized, as well as mRNA isoforms which harbored nucleotide deletions or insertions and potentially encode truncated proteins. Proteins of 30-40,000 M(r), immunologically related to human Rh proteins, were detected by western blot analysis with antipeptide antibodies, indicating that Rh-like transcripts are translated into membrane proteins. Comparison of human and nonhuman protein sequences was pivotal in clarifying the molecular basis of the blood group C/c polymorphism, showing that only the Pro103Ser substitution was correlated with C/c polymorphism. In addition, it was shown that a proline residue at position 102 was critical in the expression of C and c epitopes, most likely by providing an appropriate conformation of Rh polypeptides. From these data a phylogenetic reconstruction of the RH locus evolution has been calculated from which an unrooted phylogenetic tree could be proposed, indicating that African ape Rh-like genes would be closer to the human RhD gene than to the human RhCE gene.

Length polymorphism of a microsatellite in human and non human primates

Microsatellites are tandem repeats of short sequences elements (most often CA repeats) interspersed in many genomes and which frequently show multiallele polymorphism. They have proved invaluable for genomic mapping in man and other species and may be used for evolutionary studies provided that the available primers can be used in different species. The dystrophin gene, which shows high sequence conservation between man, rodents and chicken contains such polymorphic CA repeats. Using the oligonucleotides primers developed for testing the polymorphic CA repeat of the 3'untranslated region of the dystrophin gene in man, we achieved the amplification by polymerase chain reaction (PCR) of the analogous region in five non human primates species (Pan troglodytes, Gorilla gorilla, Macaca tonkeana, Macaca fascicularis, Lemur fulvus). All were proved to possess the CA repeat while intraspecies variations of the microsatellite length was observed in chimpanzees, gorillas and tonkean macaques. As it was demonstrated by sequencing, these length variations depend on the number of CA repeats in the microsatellite.

Molecular genetics of chimpanzee Rh-related genes: their relationship with the R-C-E-F blood group system, the chimpanzee counterpart of the human rhesus system

As the chimpanzee R-C-E-F blood group system appears to be the chimpanzee counterpart of the human Rhesus (RH) system, we have tried to determine whether chimpanzee Rh-like genes encode R-C-E-F-related proteins. Chimpanzee genomic DNA, digested by any of eight endonucleases and hybridized with three Rh exon-specific probes, exhibits a high degree of polymorphism. Analysis of DNA from unrelated individuals of different R-C-E-F types revealed that the presence of some restriction fragments is correlated with particular R-C-E-F types. The cosegregation of these fragments with R-C-E-F haplotypes was confirmed by family studies. Oligonucleotides complementary to regions flanking human exons were used as PCR primers on chimpanzee DNA; the resulting amplified fragments were identical in size to their human counterparts. Moreover, the nucleotide sequences of the fragments present a high degree of similarity to the corresponding human regions.

Chimpanzee Rh-like blood group genes map to chromosome region 1p36.1-->p34.2 by in situ hybridization

A human Rh cDNA probe was used to map the Rh-like genes in the chimpanzee. The data gathered made it possible to uniquely localize these genes to chimpanzee chromosome region 1p36.1-->p34.2. This chromosomal localization is homologous to the location of the Rh genes in the human genome.

Relationship between chimpanzee Rh-like genes and the R-C-E-F blood group system

The antigenic closeness between the chimpanzee alloantigen Rc of the R-C-E-F system, and the human alloantigen Rho(D) suggests a phyloge-connection between their genes. To confirm at the molecular level the common origin of these genes, genomic DNA from 16 unrelated chimpanzees of various R-C-E-F phenotypes were digested by three restriction enzymes and analyzed by Southern blot using a human Rh cDNA probe and three exon-specific probes. Restrictions profiles displayed reach polymorphism. Correlations between some bands and certain R-C-E-F phenotypes demonstrate that the human Rh cDNA probe defines in chimpanzee genomic DNA some genes of the R-C-E-F system.

Fabry's disease: heterozygous form of different expression in two monozygous twin sisters

A 26-year-old woman presented widespread angiokeratomas predominantly in a swimsuit distribution pattern associated with acroparesthesia in all four limbs. The tentative diagnosis of Fabry's disease (FD) was confirmed by optical and electron-microscopic findings and by appropriate biochemical testing. The work-up showed ocular and renal manifestations of the disease. The monozygous twin sister of the patient was asymptomatic although she was shown to be heterozygous for the enzymatic defect. These 2 cases illustrate the concept of extreme lyonization which can explain observed phenotypic differences in heterozygous females with X-linked hereditary diseases. The father and mother of the patient were shown to be noncarriers of the trait, suggesting de novo mutation in the twin pregnancy. However, biochemical testing for the detection of FD heterozygous females cannot rule out the possibility of the mother being heterozygous with normal enzyme activity.

t(9;11)(p22;q23) translocation in blastic phase of chronic myeloid leukemia

A patient with chronic myeloid leukemia showed clonal karyotypic evolution, with the appearance of an i(17q) and t(9;11)(p22;q23). This case sheds light upon leukemogenic events related to t(9;11)(p22;q23). The presence of t(9;22) and t(9;11) in the same clone showed that t(9;11) may affect a pluripotent stem cell, thus accounting for t(9;11) in both lymphoid and monocytic leukemias. In this patient, t(9;11) could not be related to a prior cytotoxic exposure and was instead the result of natural evolution of chronic myeloid leukemia. Furthermore, this led us to assume that the phenotype of blast cells may be determined by a chromosome abnormality. A phenotypic conversion from myeloblastic to undifferentiated morphologic aspect was observed when t(9;11) was detected, suggesting that t(9;11) may have induced a loss in differentiation of blast cells affected by this change. This assumption is in agreement with the putative presence of genes activated in pluripotent progenitors by 11q23 rearrangements.

[Role and contribution of karyotyping in male infertility]

In the context of the aetiological investigation of male infertility, the authors stress the place and the contribution of blood karyotype testing in the light of their personal experience based on 1,612 subjects. This examination has an important place, as about 15% of azoospermic subjects and 6 to 7% of subjects with oligospermia less than 10 million spermatozoa per ml, either alone or in combination with other abnormalities of the semen examination, present a congenital chromosomal abnormality. A remarkable constancy of the results was observed according to identical recruitment criteria. The contribution of this examination is also important: the medical and psychological value of detecting the cause of azoospermia, genetic counselling and antenatal chromosomal diagnosis for non-azoospermic subjects with an equilibrated structural abnormality, in whom treatment allows a chance of procreation, genetic counselling for the family of these subjects in order to prevent the appearance of a chromosomally abnormal infant. In conclusion, the authors argue in favour of the routine use of this test in all infertile subjects with at least isolated oligospermia less than 10 million spermatozoa per ml.

Human monoclonal autoantibodies produced by hybridomas derived from lymphocytes of multiple sclerosis patients

The aim of this study was to characterize autoantibodies produced in vitro by peripheral blood lymphocytes (PBL) of patients affected with multiple sclerosis (MS). We studied supernatants from man-mouse hybridomas established by fusion of PBL from 6 MS patients (group I) and from 13 individuals free of any neurological pathology (group II) with the mouse myeloma cell line P3X63 Ag8-653. They were screened for human IgG or IgM production by ELISA. Autoantibody activity against lymphocytes was studied by cell-binding ELISA. Anti-tissue reactivity was assessed by indirect immunofluorescence assay (IFA) on human cerebellum and peripheral nerve as well as on a panel of 8 non-nervous tissues. Additional ELISA tests were performed on 4 purified cellular antigens. Among 522 supernatants in group I, 13.7% contained Ig, mainly IgM, as compared to 25% among 1212 supernatants in group II; 8.3% in group I and 6.7% in group II contained anti-tissue autoantibodies. Antibodies against purified cellular antigens were found in 6% of the supernatants in group II versus 7% in group II. One human monoclonal anti-astrocyte antibody from group I was further studied. This IgM lambda (SAN-7) was particularly polyreactive and recognized glial fibrillar acid protein and other intermediate filaments, as well as tubulin and myosin. Moreover, cross-reactivity was observed with a hapten (TNP-BSA).

Natural autoantibodies in nude and normal outbred (Swiss) and inbred (BALB/c) mice

Spleen cells from adult unprimed outbred (Swiss) and inbred (BALB/c) mice, either normal (no) or athymic-nude (nu) as well as spleen cells from Swiss nude mice bearing two different human tumors (BUR and PINQ), were fused with the mouse non-secreting myeloma cell line P3X63 Ag8-653. The supernatants of immunoglobulin secreting hybrids, all containing IgM, were screened for antibody activity against macromolecular antigens (autologous: actin, tubulin, myosin, dsDNA) and haptens (TNP, NP, NIP and NBrP). Furthermore, their idiotypic determinants were analyzed using a rabbit anti-idiotype which recognizes a major cross-reactive idiotype (IdD23) of BALB/c natural polyreactive autoantibodies. In all the mice studied, we identified: (1) hybrids reacting strongly with one or more haptens (10.7 to 37.8%) and (2) hybrids secreting natural monoclonal autoantibodies (NMoAb) with broad reactivities (polyreactive and/or oligoreactive) against autoantigens and/or haptens (11.4 to 26.8%). The results indicate that: (1) cells secreting natural autoantibodies with broad reactivities exist in both normal and nude mice, independently of the genetic background (inbred/outbred) of the mouse. However, in nude mice, the natural autoantibodies exhibit a more restricted pattern of reactivity (oligoreactive) compared to those of normal mice, and do not express the common idiotype IdD23 of natural polyreactive autoantibodies. (2) Tumors grafted into nude mice seem to induce the expression of polyreactive autoantibodies bearing the IdD23.

Interferons and multiple sclerosis

Interferons (IFNs) are a family of proteins with antiviral, antitumoral and immunomodulating properties. Multiple Sclerosis (MS) is a CNS disease in which the immune reaction (IR) is the cause of the inflammatory demyelinating lesions. IFNs have been demonstrated in active lesions. The location of IFN gamma on astrocytes suggests an enhancing activity on IR by inducing Ia antigen expression on these cells. In contrast, IFN alpha/beta located on microglial cells and astrocytes might limit the growing lesion. MS patients frequently present a defective response of NK cell activity and an abnormally low production of IFNs reflecting immune dysregulation. The therapeutic trials available to date are discussed: IFN gamma possesses a severe deleterious effect but IFN alpha/beta are still under consideration due to a possible beneficial activity.