Huntington disease (HD), an autosomal dominant neurodegenerative disorder caused by an abnormal expansion of CAG trinucleotide repeat in the Huntingtin (HTT) gene, is characterized by extensive neurodegeneration of striatum and cortex and severe diffuse atrophy at MRI.The expression of genes involved in the cholesterol biosynthetic pathway and the amount of cholesterol, lanosterol, lathosterol and 24S-hydroxycholesterol were reduced in murine models of HD. In case of HD-patients, the decrease of plasma 24OHC follows disease progression proportionally to motor and neuropsychiatric dysfunction and MRI brain atrophy, together with lanosterol and lathosterol (markers of cholesterol synthesis), and 27-hydroxycholesterol. A significant reduction of total plasma cholesterol was observed only in advanced stages.It is likely that mutant HTT decreases the maturation of SREBP and the up-regulation LXR and LXR-targeted genes (SREBP, ABCG1 and ABCG4, HMGCoA reductase, ApoE) resulting into a lower synthesis and transport of cholesterol from astrocytes to neurons via ApoE. In primary oligodendrocytes, mutant HTT inhibited the regulatory effect of PGC1α on cholesterol metabolism and on the expression of MBP.HTT seems to play a regulatory role in lipid metabolism. The impairment of the cholesterol metabolism was found to be proportional to the CAG repeat length and to the load of mutant HTT. A dysregulation on PGC1α and mitochondria dysfunction may be involved in an overall reduction of acetyl-CoA and ATP synthesis, contributing to the cerebral and whole body cholesterol impairment. This article is part of a Special Issue entitled Brain Lipids.

Nothing is known about the pathophysiology of sudden infant death syndrome (SIDS). Here we show the presence of misfolded prion protein (PrP(Sc)-like) in extracts of various sections of the brains of two SIDS victims. DNA sequence information for one of these (death at 12 days) revealed two nucleotide variants in the protein coding region of the PrP gene. This may be a key finding in the understanding of SIDS pathology, and may suggest ways for identifying risk factors for SIDS in newborn infants.

This chapter discusses the genetic contributions to the pathogenesis of Alzheimer's disease (AD). During the past 10 years, tremendous progress has been made in identifying the genetic defects responsible for FAD. Two homologous genes were identified as harboring mutations linked to the most vigorous (earliest age of onset) forms of AD. The genes are now called presenilin-1 (chromosome 14) and presenilin- 2 (chromosome 1). Mutations in presenilin-1(PS-1) account for up to 8% of all AD cases, while presenilin-2 (PS-2) mutations account for many fewer cases. The presenilin mutations are transmitted in an autosomal dominant pattern with 100% penetrance in most cases. Epidemiological data suggest an increased incidence of AD in mothers of adults with Down syndrome, suggesting an underlying genetic predisposition to AD. In a recent study, evidence for the existence of frameshift mutations in amyloid precursor protein (APP) and ubiquitin-B in the brains of Down syndrome and AD patients is reported. Frameshift mutations arise post-transcriptionally and could be an important factor in non-familial AD forms of the disease although the mechanisms whereby such acquired mutations might promote neuronal degeneration are unknown. In addition, an increasing number of genetic risk factors are being identified that predispose individuals to developing late-onset AD. One risk factor involves polymorphisms in the genes encoding apolipoprotein E.

In the first part of this article we review what has been learnt from the analysis of the sequence of HCMV. A summary of this information is presented in the form of an updated map of the viral genome. HCMV is representative of a major lineage of herpesviruses distinct from previously sequenced members of this viral family and demonstrates striking differences in genetic content and organization. The virus encodes approximately 200 genes, including nine gene families, a large number of glycoprotein genes, and homologues of the human HLA class I and G protein-coupled receptor genes. The HCMV sequence thus provides a sound basis for future molecular studies of this highly complex eukaryotic virus. The second part discusses the practical rate of DNA sequencing as deduced from this and other studies. The 229 kilobase pair DNA genome of human cytomegalovirus (HCMV) strain AD169 is the largest contiguous sequence determined to date, and as such provides a realistic benchmark for assessing the practical rate of DNA sequencing as opposed to theoretical calculations which are usually much greater. The sequence was determined manually and we assess the impact of new developments in DNA sequencing.

The amino acid sequence of drp90 (Figure la) was deduced from nucleotides 1-276 (the rightward strand as reference) on the leftward reading strand of soybeam urate oxidase cDNA (1,216 bp, [uox]). The nucleotide sequence of uox, determined on average 4.6 times, differs slightly from the published sequence (1). drp90 has motifs strongly resembling functional motifs in DNA binding proteins (2, 3, 4) (figure la & lb). For expression, uox was digested with PstI and SecI. The 286 bp fragment carrying drp90 cDNA was isolated and ligated into SmaI cut pTrc99B (5) and transformed into E. coli RB791. Analysis of expressed proteins were done as described (5) except insoluble proteins were isolated by phenol extraction and alcohol precipitation.Theprotein SDS -PAGE patterns obtained with bacteria carrying pTrc99B (controls) and drp90-pTrc99B (recombinants) show no differences in the soluble protein fractions, but the insoluble fraction of induced recombinants, but not of controls, contained two proteins 10 and 12 kDa (Figure 2i & 2ii). Peptides of this size are consistent with a recombinant fusion protein (drp90f) which opens at the 'ATG' provided by the vector cloning site and the product of a restart translation at the drp90 orf (wild type drp90). Gel retardation studies using crude protein from induced

Large-scale sequence analysis of the AD169 strain of human cytomegalovirus (HCMV) began in this laboratory in 1984 when very little was known about the sequence or location of genetic information in the viral genome. At that time sequence analysis was confined to the major immediate-early gene (Stenberg et al. 1984), a region of the Colburn strain that contained CA tracts (Jeang and Hayward 1983), the L-S junction region (Tamashiro et al. 1984), and what has been termed the transforming region (Kouzarides et al. 1983). This chapter is being written in March 1989 when the sequence is complete except for some remaining polishing of certain areas which is still going on (manuscript in preparation). As far as we know there are no major discrepancies in the data which might lead to the sequence changing although of course this cannot be ruled out. We present a preliminary analysis of the HCMV genome and limit ourselves mainly to the potential protein-coding content of over 200 reading frames.

Human cytomegalovirus (HCMV) is a herpesvirus with a genome of 230 kilobases (Kb) encoding about 200 genes. Although infection is generally innocuous, HCMV causes serious congenital and neonatal disease, and is a dangerous opportunistic pathogen in immune-deficient individuals. We have identified a family of three HCMV genes which encode polypeptides containing seven putative membrane-spanning domains, and a series of well-defined motifs characteristic of the rhodopsin-like G protein-coupled receptors (GCRs). By these criteria all three of the HCMV sequences are homologous to cellular GCRs. Members of this receptor family function in visual signal transduction, regulation of homeostasis, and development, and include known and potential oncogenes. These receptors are activated by photons or small molecules such as neurotransmitters, and glycoprotein hormones. The finding of viral-encoded GCR homologues implies a further level of complexity in the interactions between HCMV and its host, and may provide a potential pathway for virally transformed cell proliferation. Their identification could permit the development of a novel class of antiviral drugs analogous to beta-adrenergic receptor antagonists.

Human cytomegalovirus particles contain a phosphoprotein of 150,000 (pp150) apparent molecular weight in their matrix; the protein appears particularly reactive in Western blot analyses with human antisera. The gene for pp150 was mapped by screening a bacteriophage lambda gt11 cDNA expression library with monospecific rabbit antisera. Subsequent hybridization of cDNA with cosmid and plasmid clones containing the human cytomegalovirus strain AD169 genome mapped the gene to HindIII fragments J and N. The gene is transcribed into a late 6.2-kilobase RNA. The nucleotide sequence of this region was determined, and a transcription initiation site and two polyadenylation sites of an abundant transcript were located by primer extension and nuclease protection experiments. The reading frame for pp150, deduced from computer analyses, gives rise to a polypeptide of 1,048 amino acids in length; protein secondary structure analysis revealed multiple beta-pleated sheets in hydrophilic clusters, providing a possible explanation for the immunogenic properties of the polypeptide.