Two new proteins preferentially associated with membrane immunoglobulin D.

The IgM and IgD classes of antigen receptor can perform different functions on B cells. However, so far no class-specific components communicating with the cytoplasm have been found in the two antigen receptors. We have employed a new biotinylation protocol to search for intracellular membrane Ig-associated proteins. Here we describe two proteins of 29 and 31 kDa that are associated with membrane IgD and to some extent with membrane IgM. The membrane IgM molecule is associated specifically with three proteins of 32, 37 and 41 kDa. The purification and sequencing of the two mIgD-associated proteins revealed that they are novel proteins which are related to each other. These proteins may be the missing link between the antigen receptor and the cytoskeleton and may contribute to functional differences between membrane IgM and membrane IgD.     

FMR1 gene deletion/reversion: a pitfall of fragile X carrier testing

The Fragile X syndrome is, in the majority of cases, caused by CGG trinucleotide amplification within the FMR1 gene. The syndrome is rarely caused by point mutations or deletions. Here we describe a family with 2 sons and 1 daughter affected by Fragile X syndrome and 2 unaffected daughters whose carrier status was unknown prior to this study. Analysis of DNA from each of the 2 daughters revealed two alleles in the normal size range. However, 1 daughter carried one allele of 10 CGG repeats that was not present in either the mother or the father. No evidence for mosaicism could be detected. Haplotype analysis of flanking polymorphic markers revealed that the 10 CGG allele was derived from the mutated allele inherited from the mother. Thus, this case most likely represents an additional case of a reverse mutation from a premutation allele in a female to a normal-sized allele in the offspring. It remains unclear how frequently such reversion events occur. The observation has important consequences for genetic testing, because many laboratories prescreen for the Fragile X syndrome by determining the length of the CGG repeat using PCR. If this shows alleles in the normal size range, a diagnosis of Fragile X syndrome is considered to be excluded. Because the routine PCR and/or Southern blot analyses alone may yield false-negative results in cases of a regression of the number of CGG repeats, we strongly recommend the inclusion of fragment length or haplotype analysis when determining the carrier status within Fragile X syndrome families.     

FMR1 in global populations.

Fragile X syndrome, a frequent form of inherited mental retardation, results from the unstable expansion of a cryptic CGG repeat within the 5' UTR region of the FMR1 gene. The CGG repeat is normally polymorphic in length, and the content is frequently interrupted by AGG triplets. These interruptions are believed to stabilize the repeat, and their absence, leading to long tracts of perfect CGG repeats, may give rise to predisposed alleles. In order to examine the stability of normal FMR1 alleles, the repeat length of 345 chromosomes from nine global populations was examined with the content also determined from 114 chromosomes as assessed by automated DNA sequencing. The FMR1 alleles, defined by the CGG repeat, as well as by the haplotypes of nearby polymorphic loci, were very heterogeneous, although the level of variation correlated with the age and/or genetic history of a particular population. Native American alleles, interrupted by three AGG repeats, exhibited marked stability over 7,000 years. However, in older African populations, parsimony analysis predicts the occasional loss of an AGG, leading to more perfect CGG repeats. These data therefore support the suggestion that AGG interruptions enhance the stability of the FMR1 repeat and indicate that the rare loss of these interruptions leads to alleles with longer perfect CGG-repeat tracts.     

Allelic polymorphism of FMR1 gene CGG-repeat region in patients with impairment of natural and stimulated ovulation

The frequency of heterozygote carriers of (risk zone, alleles of FMR1 gene (40-47 CGG-repeats) was significantly higher in group of patients with ovarian dysfunction than in control group I. The tendency for higher frequency of those alleles was observed in patients with "poor response" to superovulation induction in IVF cycles. The average number of oocytes and follicles, which was obtained after stimulation of superovulation, was significantly decreased in FMR1 gene "risk zone" alleles carriers compared to patients with normal alleles of FMR1 gene. The average general dosage of exogenous gonadotrophin, necessary for superovulation induction was significantly higher in heterozygote carriers of FMR1 gene "risk zone" alleles than in patients with normal genotype. Thereby, the FMR1 gene "risk zone" alleles can be one of the hereditary susceptibility factors of impairment nature and stimulated ovulation.     

Two cases of anorexia nervosa associated with Graves' disease

In this report on two cases of anorexia nervosa associated with Graves' disease, metabolism and the relationship between the two illness are considered. Case 1 was a 25-year-old female. Anorexia was associated with a stressful life situation following marriage. One year after the onset of anorexia, her condition was diagnosed as Graves' disease. In spite of high levels of serum thyroid hormone, she did not show the clinical signs and symptoms of hyperthyroidism. The hypermetabolic state of Graves' disease seems to be suppressed by the hypometabolism of anorexia. Case 2 was a 17-year-old female whose body weight, due to anorexia, at one time had decreased from 55 kg to 35.2 kg. A rebound from anorexia to bulimia increased her body weight to 80 kg in spite of an association with the hypermetabolic state of Graves' disease. In light of the abovementioned cases, it seems that the clinical picture of Graves' disease is usually hidden by the clinical symptoms of anorexia nervosa.     

Prenatal diagnosis of X-linked choroideremia with mental retardation,associated with a cytologically detectable X-chromosome deletion

Summary We describe a family in which an X-chromosome deletion is segregating with choroideremia, an X-linked recessive condition. The DNA sequences DXYS1 and DXS3, defined by the probes pDP34 and 19.2 respectively, are absent in the affected male (who is also mentally retarded), and hemizygous in his mother and in his carrier sister, who presented early in pregnancy. Analysis of chorionic villus DNA formed the basis of prenatal exclusion of choroideremia in her male fetus. In three female relatives, studied with late-labelling techniques, the deleted X was preferentially inactivated in 86–100% of cells studied. This family confirms the localisation of the choroideremia locus to within Xq1321, and places the loci for anhidrotic ectodermal dysplasia and the X-linked immunodeficiencies outside this region.     

Short arm deletion of chromosome 12: report of two new cases.

Two boys (W.M. and C.P.) are described, in each of whom a short-arm deleted C chromosome was apparently present. The clinical findings on W.M. are stenosis of the sagittal sutura associated with atrophy of the nervus opticus and mental retardation, and on C.P. osteogenesis imperfecta. An analysis of the G- and Q-banding patterns revealed in each patient a 12p-- chromosome. The deletion involved most of band p12 as shown by length measurements on G-banded chromosomes. Both cases were compared to proven and presumed cases of 12p-- from literature, but no common clinical phenotype could be demonstrated.     

Two new cases of the Christchurch (Ch1) chromosome 21: evidence for clinical consequences of de novo deletion 21P-

We performed an investigation of two unrelated cases with extremal variants of chromosome 21 without visible materials of the short arms (Christchurch or Ch1 chromosome). In the first case chromosome 21p- was initially detected during routine cytogenetic amniocentesis. Chromosomal variant was inherited from phenotypically normal father to phenotypically normal fetus (phenotypically normal boy after the birth). The second case of chromosome 21p- was detected in 7 years old boy, referred to cytogenetic analysis due to mental retardation and mild congenital malformation, including prenatal hypoplasia, microcephaly, low-set dysplastic ears, short nose, micrognatia, short neck. Molecular characterization of 21p-variant chromosomes was performed by the use of FISH with DNA probes specific to the short arm and centromeric region of chromosome 21 (telomeric, beta-satellite, ribosomal, classical satellite and alphoid DNA probes). Chromosomes 21p-hybridized positively only with telomeric DNA at both chromosomal ends and alphoid DNA probes at centromeric region of the first patient. In second case (de novo deletion of 21p), the Ch1 was associated with clinical phenotype and loss of telomeric and subtelomeric DNA in the p-arm of chromosome 21. Therefore, the complete absent of the short arm of chromosome 21 may be considered as abnormal. We propose that de novo deletion 21p- could have negative consequences due to absence of large portion of chromosomal DNA from the p-arm (telomeric, satellite or ribosomal DNAs) and following imbalance in organization and functioning of genome.     

Identification of an FMR cell surface antigen associated with murine leukemia virus-infected cells.

FMR antigens are found on the surface of cells infected with Friend, Moloney, and Rauscher murine leukemia viruses (MuLV). These antigens are serologically distinct from the G cell surface antigens that are found on cells infected with endogenous MuLV (AKR and Gross virus). Cell surface antigens of both virus groups are immunogenic in mice, and immunization with appropriate virus-infected cells leads to the production of cytotoxic antisera. The cytotoxic activity of FMR antisera can be absorbed by disrupted preparations of Rauscher MuLV, but not by AKR MuLV. FMR antisera precipitate the viral envelope proteins gp70, pl5(E), and p12(E) from detergent-disrupted preparations of [3H]leucine-labeled MuLV. The reaction of these antisera with p15(E) and p12(E) proteins is directed against group-specific antigens and can be absorbed with AKR MuLV; in contrast, the reaction of these antisera with gp70 is directed against type-specific antigens and is absorbed only by viruses of the FMR group. In immune precipitation assays with detergent-disrupted 125I surface-labeled cells, FMR antisera react only with type-specific antigens of the viral envelpe protein. On the basis of these findings we conclude that the FMR cell surface antigen is a determinant on the MuLV env gene product.     

Mental status of females with an FMR1 gene full mutation.

The cloning of the FMR1 gene enables molecular diagnosis in patients and in carriers (male and female) of this X-linked mental retardation disorder. Unlike most X-linked disorders, a considerable proportion of the female carriers of a full mutation of the FMR1 gene is affected. In this study, the intelligence quotients (IQs) were ascertained by the Wechsler Adult Intelligence Scale in 33 adult females with a full mutation, with 28 first-degree adult female relatives (mainly sisters) without a full mutation as controls. Seventy-one percent of the females with a full mutation had IQ scores below 85. In paired analysis, no significant correlation could be detected between the IQs of the females with a full mutation and those of their first-degree female relatives, reflecting a dominant effect of the FMR1 gene full mutation in the mental development of females. Considering females with a full mutation only, we observed a significant relation between the proportion of normal FMR1 alleles on the active X chromosome and IQ. We present a model to explain this relationship.     

Distal deletion of the long arm of chromosome number 1 (q43-->qter) associated with severe mental retardation and a nonspecific dysmorphic syndrome.

A 6 8/12-year-old girl with severe mental retardation, multiple congenital malformations and a de novo distal deletion of the long arm of chromosome 1 [del 1 (q43-->qter)] is here described. A review of the reported patients does not allow to distinguish different phenotypes related to distal deletion 1q42 and/or 1q43.     

Screening for FMR1 and FMR2 mutations in 222 individuals from Spanish special schools: identification of a case of FRAXE-associated mental retardation

Fragile X syndrome is the most common inherited form of familial mental retardation. It results from a (CGG) _n trinucleotide expansion in the FMR1 gene leading to the typical Martin-Bell phenotype. Clinical features vary depending on age and sex. Expansion of a (CCG) _n repeat in the FMR2 gene corresponds to the FRAXE fragile site which lies distal to FRAXA and is also associated with mental retardation, but it is less frequent and lacks a consistent phenotype. Analysis of repeat expansions in these two genes allows the molecular diagnosis of these different entities. We report here the screening of the FRAXA and FRAXE mutations in 222 unrelated mentally retarded individuals attending Spanish special schools. PCR and/or Southern blotting methods were used. We detected full mutations in the FMR1 gene in 11 boys (4.9%) and 1 boy (0.5%) with a CCG repeat expansion in the FMR2 gene. The latter shows mild mental retardation with psychotic behaviour and no remarkable physical traits. Molecular studies revealed a mosaicism for methylation in the FMR2 gene. This case supports the observation that expansions greater than 100 repeats can be partially methylated and cause the phenotype. Received: 11 February 1997 / Accepted: 9 June 1997     

Familial transmission of the FMR1 CGG repeat.

To better define the nature of FMR1 CGG-repeat expansions, changes in allele sizes for 191 families with fragile X and for 33 families with gray-zone repeats (40-60) were analyzed. Expansion of the fragile X chromosome to the full mutation was seen in 13.4% of offspring from premutation mothers with 56-59 repeats, 20.6% of those with 60-69 repeats, 57.8% of those with 70-79 repeats, 72.9% of those with 80-89 repeats, and 97.3% of those with 90-199 repeats. For premutation fathers, the majority (62%) of their daughters had a larger repeat number, while a few had either a smaller (22%) or the same (16%) repeat number, compared with their fathers' sizes. However, daughters with a smaller repeat number were observed only if their fathers had > or = 80 repeats. Fifteen (39.5%) of 38 such daughters carried a smaller repeat than did their fathers. We observed that a similar repeat number was inherited more often than expected by chance, among the members of a sibship segregating fragile X. This familial clustering, observed in the offspring of both males and females with a premutation, implies there may be an additional factor, independent of parental repeat size, that influences CGG-repeat instability. Instability in gray-zone allele transmissions was observed in 25% of alleles with 50-60 CGGs but in <8% of those with 40-49 CGGs. Examination of gray-zone allele organization revealed that long tracts of pure CGGs (>34) are not always unstably transmitted. These results raise new questions regarding the familial factors that may determine transmission expansions.     

Maternal duplication associated with gene deletion in sporadic hemophilia.

Sporadic occurrences of X-linked disorders can give insights into mutagenesis in man. In a case of sporadic hemophilia, associated with a partial deletion of the factor VIII gene, an unexpected inheritance pattern of gene rearrangements was observed. The factor VIII gene was found to be partially duplicated in the hemophiliac's mother. A pedigree analysis indicates that the mother has contributed both aberrant genes as well as the normal gene to her offspring. One simple model for the evolution of the deletion in this family is that the duplication is the precursor to the deletion.