Charcot-Marie-Tooth phenotype produced by a duplicated PMP22 gene as part of a 17P trisomy-translocation to the X chromosome

The Charcot-Mane-Tooth disease type 1A (CMTlA) phenotype is most often associated with a 1.5 megabase (mb), tandem duplication of chromosome 17 band p12 (17˜12). The prevailing hypothesis is that the demyelinating neuropathy results from a dosage effect of the peripheral myelin protein gene PMP22 which is included within this duplication. We present a patient with clinical and electrophysiological features ofCMTlA in whom an extra PMP22 gene resulted from a rare unbalanced translocation of 17p to the X chromosome. This finding further supports the hypothesis of gene dosage as the basis for CMTlA. More-over, this case highlights the importance of fluorescence in siiu hybridization (FISH) as an alternative molecular technique in the diagnosis of CMTlA.     

Inhibition of the Mixed Lymphocyte Culture Response by Antibody Following Successful Human Renal Transplantation

Immunoglobulin G, appearing after several months in the serum of a recipient of a successful kidney transplant from a closely matched sibling donor, was demonstrated to progressively inhibit unidirectional mixed lymphocyte cultures when donor lymphocytes were used either in responding or stimulating cell populations. The active recipient IgG had no effect in cultures in which donor cells were not used, nor did IgG obtained from other individuals show nonspecific inhibitory effects on cultures containing donor cells. It is suggested that the MLC inhibitory immunoglobulin may serve an immunoregulatory function after renal transplantation.     

Aspergillus fumigatus empyema, arthritis, and calcaneal osteomyelitis in a lung transplant patient successfully treated with posaconazole

A 64-year-old male with Aspergillus fumigatus infection that had disseminated from the lung to the ankle and adjacent bone was treated successfully with posaconazole after therapy with itraconazole and amphotericin B lipid complex failed. Marked clinical improvement occurred within 6 weeks of initiation of posaconazole therapy; after 6 months, infection had resolved at all sites. The patient has had no recurrence of infection.     

Separation of chromosomes of Cryptococcus neoformans by pulsed field gel electrophoresis.

Chromosomes from Cryptococcus neoformans, an encapsulated yeast pathogen, were separated by contour-clamped homogeneous field gel electrophoresis. Seven strains representing all four serotypes were studied. It was found that each strain had a unique, reproducible pattern of chromosome bands which could potentially be used for strain polymorphism studies. There were between 10 and 12 chromosomes in the strains studied, with an approximate genomic size of 15,000 to 17,000 kilobases. Chromosome separation also could be used to assign locations for cloned genes, and the ribosomal DNA genes were found on one of the larger C. neoformans chromosomes. The technique of electrophoretic karyotyping should be helpful for genetic and molecular investigations into the biology of C. neoformans.     

Cryptococcus neoformans differential gene expression detected in vitro and in vivo with green fluorescent protein

Synthetic green fluorescent protein (GFP) was used as a reporter to detect differential gene expression in the pathogenic fungus Cryptococcus neoformans. Promoters from the C. neoformans actin, GAL7, or mating-type alpha pheromone (MFalpha1) genes were fused to GFP, and the resulting reporter genes were used to assess gene expression in serotype A C. neoformans. Yeast cells containing an integrated pACT::GFP construct demonstrated that the actin promoter was expressed during vegetative growth on yeast extract-peptone-dextrose medium. In contrast, yeast cells containing the inducible GAL7::GFP or MFalpha1::GFP reporter genes expressed significant GFP activity only during growth on galactose medium or V-8 agar, respectively. These findings demonstrated that the GAL7 and MFalpha1 promoters from a serotype D C. neoformans strain function when introduced into a serotype A strain. Because the MFalpha1 promoter is induced by nutrient deprivation and the MATalpha locus containing the MFalpha1 gene has been linked with virulence, yeast cells containing the pMFalpha1::GFP reporter gene were analyzed for GFP expression in the central nervous system (CNS) of immunosuppressed rabbits. In fact, significant GFP expression from the MFalpha1::GFP reporter gene was detected after the first week of a CNS infection. These findings suggest that there are temporal, host-specific cues that regulate gene expression during infection and that the MFalpha1 gene is induced during the proliferative stage of a CNS infection. In conclusion, GFP can be used as an effective and sensitive reporter to monitor specific C. neoformans gene expression in vitro, and GFP reporter constructs can be used as an approach to identify a novel gene(s) or to characterize known genes whose expression is regulated during infection.     

Life expectancy in British Marfan syndrome populations

A total of 206 patients with Marfan syndrome were ascertained throughout genetic clinics in Wales and Scotland during the period 1970–1990. There were 45 deaths representing 22% of the cohort. Mean age at death was 45.3 ± 16.5 years. 50% median cumulative survival in the total cohort (n = 206) was 53 years for males and 72 years for females. Multivariate analysis confirmed severity as the best independent indicator of survival. These findings and survival curves will assist in the counselling of British families and individuals with Marfan syndrome.     

The GAP-related domain of tuberin, the product of the TSC2 gene, is a target for missense mutations in tuberous sclerosis

Tuberous sclerosis is an autosomal dominant trait in which the dysregulation of cellular proliferation and differentiation results in the development of hamartomatous growths in many organs. The TSC2 gene is one of two genes determining tuberous sclerosis. Inactivating germline mutations of TSC2 in patients with tuberous sclerosis and somatic loss of heterozygosity at the TSC2 locus in the associated hamartomas indicate that TSC2 functions as a tumour suppressor gene and that loss of function is critical to expression of the tuberous sclerosis phenotype. The TSC2 product, tuberin, has a region of homology with the GTPase activating protein rap1GAP and stimulates the GTPase activity of rap1a and rab5a in vitro. Here we show that the region of homology between tuberin and human rap1GAP and the murine GAP mSpa1 is more extensive than previously reported and spans approximately 160 amino acid residues encoded within exons 34-38 of the TSC2 gene. Single strand conformation polymorphism analysis of these exons in 173 unrelated patients with tuberous sclerosis and direct sequencing of variant conformers together with study of additional family members enabled characterisation of disease associated mutations in 14 cases. Missense mutations, which occurred in exons 36, 37 and 38 were identified in eight cases, four of whom shared the same recurrent change P1675L. Each of the five different missense mutations identified was shown to occur de novo in at least one sporadic case of tuberous sclerosis. The high proportion of missense mutations detected in the region of the TSC2 gene encoding the GAP-related domain supports its key role in the regulation of cellular growth.