Linkage analysis in adenomatous polyposis coli families in the United Kingdom, and a search for highly polymorphic markers

Familial adenomatous polyposis (FAP), also known as adenomatous polyposis coli (APC), is a relatively common autosomal dominant disorder characterized by the development of hundreds to thousands of pre-malignant adenomatous polyps in the colon and rectum by the third decade of life in most affected individuals. Colonic polyposis with the addition of extracolonic lesions was formerly considered to constitute a distinct syndrome first described by Gardner. The gene for APC has been mapped to chromosome 5, region q21-22, by linkage to the DNA marker, C11p11 (D5S71). Linkage to the more informative markers, n227 (D5S37), ECB27 (D5S98) and YN5.48 (D5S81) was subsequently reported. The evidence now available suggests that Gardner's syndrome maps to the same region of chromosome 5 as APC and the prevailing opinion is that the two cannot be clinically distinguished. This study comprised 26 families, 206 individuals, segregating for FAP. The DNA markers used for the linkage analysis were C11p11, n227, ECB27 and YN5.48. The purpose was to estimate the genetic distance between these markers and the disease locus in order to be able to assess the reliability of these markers for prenatal and presymtomatic diagnosis of FAP. Not a single gene order could be established from our data, although either of the orders 227-Cllpll-ECB27-APC-YN5.48 or 227-C11p11-ECB27-YN5.48-APC were possible. The genetic distances were estimated as 17 cM between n227 and AFC, 4 cM between n227 and ECB27. YN5.48 was found to be extremely close to AFC, with the highest lod score obtained at a recombination fraction of nought. Although the DNA markers were quite informative, there were instances where none or only one was informative in a given family. The recent discovery of frequent length variation in dinucleotide (C-A) repeats which are uniformly spaced throughout the genome, provides the basis for the isolation of potentially informative markers. The construction of a cosmid library was undertaken and it was subsequently screened with all the DNA probes. Two different clones were isolated using ECB27, both of which contain the same (C-A) repeat. One of them was sequenced and found to be repeated nine times. When tested for its polymorphic value it gave two alleles, one corresponding to (C-A)9 the other to (C-A) 10. This polymorphic marker showed complete linkage disequilibrium with ECB27

Genetics and therapies for GM2 gangliosidosis

Tay-Sachs disease, caused by impaired β-N-acetylhexosaminidase activity, was the first GM2 gangliosidosis to be studied and one of the most severe and earliest lysosomal diseases to be described. The condition, associated with the pathological build-up of GM2 ganglioside, has acquired almost iconic status and serves as a paradigm in the study of lysosomal storage diseases. Inherited as a classical autosomal recessive disorder, this global disease of the nervous system induces developmental arrest with regression of attained milestones; neurodegeneration progresses rapidly to cause premature death in young children. There is no effective treatment beyond palliative care, and while the genetic basis of GM2 gangliosidosis is well established, the molecular and cellular events, from diseasecausing mutations and glycosphingolipid storage to disease manifestations, remain to be fully delineated. Several therapeutic approaches have been attempted in patients, including enzymatic augmentation, bone marrow transplantation, enzyme enhancement, and substrate reduction therapy. Hitherto, none of these stratagems has materially altered the course of the disease. Authentic animal models of GM2 gangliodidosis have facilitated in-depth evaluation of innovative applications such as gene transfer, which in contrast to other interventions, shows great promise. This review outlines current knowledge pertaining the pathobiology as well as potential innovative treatments for the GM2 gangliosidoses.MRC programme award The National Institute of Health Research University of Cambridge Biomedical Research Centr

Decrease in Myelin-Associated Lipids Precedes Neuronal Loss and Glial Activation in the CNS of the Sandhoff Mouse as Determined by Metabolomics

Sandhoff disease (SD) is a lysosomal disease caused by mutations in the gene coding for the β subunit of β-hexosaminidase, leading to deficiency in the enzymes β-hexosaminidase (HEX) A and B. SD is characterised by an accumulation of gangliosides and related glycolipids, mainly in the central nervous system, and progressive neurodegeneration. The underlying cellular mecha-nisms leading to neurodegeneration and the contribution of inflammation in SD remain unde-fined. The aim of the present study was to measure global changes in metabolism over time that might reveal novel molecular pathways of disease. We used liquid chromatography-mass spec-trometry and 1H Nuclear Magnetic Resonance spectroscopy to profile intact lipids and aqueous metabolites, respectively. We examined spinal cord and cerebrum from healthy and Hexb -/- mice, a mouse model of SD, at ages one, two, three and four months. We report decreased concentrations in lipids typical of the myelin sheath, galactosylceramides and plasmalogen-phosphatidylethanolamines, suggesting that reduced synthesis of myelin lipids is an early event in the development of disease pathology. Reduction in neuronal density is pro-gressive, as demonstrated by decreased concentrations of N-acetylaspartate and amino acid neurotransmitters. Finally, microglial activation, indicated by increased amounts of myo-inositol correlates closely with the late symptomatic phases of the disease

Identification of unique reciprocal and non reciprocal cross packaging relationships between HIV-1, HIV-2 and SIV reveals an efficient SIV/HIV-2 lentiviral vector system with highly favourable features for in vivo testing and clinical usage.

BACKGROUND: Lentiviral vectors have shown immense promise as vehicles for gene delivery to non-dividing cells particularly to cells of the central nervous system (CNS). Improvements in the biosafety of viral vectors are paramount as lentiviral vectors move into human clinical trials. This study investigates the packaging relationship between gene transfer (vector) and Gag-Pol expression constructs of HIV-1, HIV-2 and SIV. Cross-packaged vectors expressing GFP were assessed for RNA packaging, viral vector titre and their ability to transduce rat primary glial cell cultures and human neural stem cells. RESULTS: HIV-1 Gag-Pol demonstrated the ability to cross package both HIV-2 and SIV gene transfer vectors. However both HIV-2 and SIV Gag-Pol showed a reduced ability to package HIV-1 vector RNA with no significant gene transfer to target cells. An unexpected packaging relationship was found to exist between HIV-2 and SIV with SIV Gag-Pol able to package HIV-2 vector RNA and transduce dividing SV2T cells and CNS cell cultures with an efficiency equivalent to the homologous HIV-1 vector however HIV-2 was unable to deliver SIV based vectors. CONCLUSION: This new non-reciprocal cross packaging relationship between SIV and HIV-2 provides a novel way of significantly increasing bio-safety with a reduced sequence homology between the HIV-2 gene transfer vector and the SIV Gag-Pol construct thus ensuring that vector RNA packaging is unidirectional.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are