Screening for mutations in the open reading frame and promoter of the beta-amyloid precursor protein gene in familial Alzheimer's disease: identification of a further family with APP717 Val-->Ile.

Following the identification of mutations in the beta-amyloid precursor protein (APP) gene in familial, early onset Alzheimer's disease (AD), we have developed a screening protocol using single strand conformation analysis (SSCA) to screen exon 17 for the known mutations within APP. In addition, we used this protocol to screen the other seventeen exons of APP and a three hundred and thirty base pair regulatory region of the promoter for new mutations in 9 families with early onset AD. Exons 16 and 17, which encode the deposited beta-amyloid peptide, were screened in a further 10 families. Our screening procedure identifies all the reported mutations within APP. While we have identified a further family with APP717 Val-->Ile, we did not find any previously undescribed mutations. Screening of other exons of APP in 2 families in which we have previously reported mutations at APP717, failed to reveal other sequence abnormalities supporting the hypothesis that the mutations at APP717 cause the disease in these families. These data suggest that mutations in APP are a rare cause of familial early onset AD (3/21 families tested) and that within APP most, possibly all, mutations which cause AD are in exon 17.     

Anger and psychobiological changes during smoking abstinence and in response to acute stress: prediction of smoking relapse.

Nicotine may be used to manage negative emotions, and recent research suggests that smokers with high levels of hostility may use cigarettes to cope with anger provoking situations. This study evaluated the extent to which a high level of trait anger is associated with risk for relapse among smokers interested in cessation. Chronic smokers with different levels of trait anger provided reports of withdrawal symptoms, craving, and state anger, and collected saliva samples for cortisol during 24-hour ad libitum smoking and the first 24-hour abstinence period of a quit attempt. They also attended a laboratory session conducted after the 24-hour abstinence during which they performed brief mental and social stress challenges and provided blood samples for adrenocorticotropin (ACTH) and cortisol assays. High trait anger was associated with greater increases in state anger, withdrawal symptoms, and craving during the first 24 h of abstinence. It was also associated with greater ACTH concentrations during the laboratory session. High trait anger was also associated with increased risk for early relapse. The findings support the hypothesis that smokers high in anger trait may have greater mood difficulties during abstinence and may be more vulnerable to early relapse than smokers with low anger trait.     

Discrete pulses of molting hormone, 20-hydroxyecdysone, during late larval development of Drosophila melanogaster: correlations with changes in gene activity.

Periodic pulses of the insect steroid molting hormone 20-hydroxyecdysone (20E), acting via its nuclear receptor complex (EcR/USP), control gene expression at many stages throughout Drosophila development. However, during the last larval instar of some lepidopteran insects, subtle changes in titers of ecdysteroids have been documented, including the so-called "commitment peak." This small elevation of 20E reprograms the larva for metamorphosis to the pupa. Similar periods of ecdysteroid immunoreactivity have been observed during the last larval instar of Drosophila. However, due to low amplitude and short duration, along with small body size and staging difficulties, their timing and ecdysteroid composition have remained uncertain. Employing a rigorous regimen of Drosophila culture and a salivary gland reporter gene, Sgs3-GFP, we used RP-HPLC and differential ecdysteroid RIA analysis to determine whole body titers of 20E during the last larval instar. Three small peaks of 20E were observed at 8, 20, and 28 hr following ecdysis, prior to the well-characterized large peak around the time of pupariation. The possible regulation of 20E levels by biosynthetic P450 enzymes and the roles of these early peaks in coordinating gene expression and late larval development are discussed.     

Congenital insensitivity to pain with anhidrosis (CIPA) in Israeli-Bedouins: genetic heterogeneity, novel mutations in the TRKA/NGF receptor gene, clinical findings, and results of nerve conduction studies

Congenital insensitivity to pain with anhidrosis (CIPA), a rare and severe disorder, comprises absence of sensation to noxious stimuli, inability to sweat, and recurrent episodes of hyperthermia. It has a relatively high prevalence in the consanguineous Israeli-Bedouins. Clinical studies of 28 patients are reported here. Using the linkage analysis approach, we linked the disease in 9 of 10 unrelated Israeli-Bedouin families with CIPA to the TrkA gene, which encodes the receptor for nerve growth factor. In one family, linkage was excluded, implying that another gene, yet unidentified, is involved. Two new mutations in the tyrosine kinase domain of the TrkA gene were identified in our CIPA patients: a 1926-ins-T in most of the southern Israeli-Negev CIPA patients, and a Pro- 689-Leu mutation in a different isolate of Bedouins in northern Israel. Eight prenatal diagnoses were made in the southern Israeli-Negev Bedouins, two by linkage analysis and six by checking directly for the 1926-ins-T mutation. Three polymorphisms in the TrkA protein kinase encoding domain were also observed.     

A population study of mutations and LOH at breast cancer gene loci in tumours from sister pairs: two recurrent mutations seem to account for all BRCA1/BRCA2 linked breast cancer in Iceland.

The majority of breast cancer in high risk families is believed to result from a mutation in either of two genes named BRCA1 and BRCA2. A germline defect in either gene is usually followed by chromosomal deletion of the normal allele in the tumour. In Iceland two recurrent mutations have been identified, 999del5 BRCA2 and G5193A BRCA1. In this study, randomly selected pairs of sisters diagnosed with breast cancer at the age of 60 years or younger were analysed to evaluate the proportion of breast cancer resulting from BRCA1 and BRCA2. Genotypes and allele loss in tumour tissue from 42 sister pairs were compared using markers within and around the BRCA1 and BRCA2 genes. Eleven sister pairs were highly suggestive of BRCA2 linkage, and no obvious BRCA1 linkage was seen. Screening for the G5193A BRCA1 and 999del5 BRCA2 mutations showed the 999del5 mutation in the 11 BRCA2 suggestive pairs plus three pairs less indicative of linkage, and the G5193A BRCA1 mutation in one pair. When known mutation carriers are removed from the group, no indication of further linkage to BRCA1 or BRCA2 is seen. The results of our studies suggest that a large proportion of familial breast cancer in Iceland is the result of the 999del5 BRCA2 mutation, and it is unlikely that BRCA1 and BRCA2 germline mutations other than 999del5 and G5193A play a significant role in hereditary breast cancer in Iceland. Furthermore it can be concluded that most families with BRCA1 or BRCA2 linkage are easily identified by studying LOH around the defective gene in as few as two affected relatives.     

Mutational pattern of the nurse shark antigen receptor gene (NAR) is similar to that of mammalian Ig genes and to spontaneous mutations in evolution: the translesion synthesis model of somatic hypermutation.

The pattern of somatic mutations of shark and frog Ig is distinct from somatic hypermutation of Ig in mammals in that there is a bias to mutate GC base pairs and a low frequency of mutations. Previous analysis of the new antigen receptor gene in nurse sharks (NAR), however, revealed no bias to mutate GC base pairs and the frequency of mutation was comparable to that of mammalian IgG. Here, we analyzed 1023 mutations in NAR and found no targeting of the mechanism to any particular nucleotide but did obtain strong evidence for a transition bias and for strand polarity. As seen for all species studied to date, the serine codon AGC/T in NAR was a mutational hotspot. The NAR mutational pattern is most similar to that of mammalian IgG and furthermore both are strikingly akin to mutations acquired during the neutral evolution of nuclear pseudogenes, suggesting that a similar mechanism is at work for both processes. In yeast, most spontaneous mutations are introduced by the translesion synthesis DNA polymerase zeta (REV3) and in various DNA repair-deficient backgrounds transitions were more often REV3-dependent than were transversions. Therefore, we propose a model of somatic hypermutation where DNA polymerase zeta is recruited to the Ig locus. An excess of DNA glycosylases in germinal center reactions may further enhance the mutation frequency by a REV3-dependent mutagenic process known as imbalanced base excision repair.     

Relationship of MAO-A promoter (u-VNTR) and COMT (V158M) gene polymorphisms to CSF monoamine metabolites levels in a psychiatric sample of caucasians: A preliminary report.

Monoamine oxidase A gene promoter (MAOA-uVNTR) and catechol-O-methyltransferase V158M (COMT-V158M) gene functional polymorphisms are reported to be associated with impulsive-aggression, but a biological intermediate effect remains to be determined. This study assessed the association of these polymorphisms with cerebrospinal fluid (CSF) monoamine metabolites as endophenotypes. Ninety-eight Caucasian psychiatric subjects were assessed for Axis I and II diagnosis. Subjects were genotyped for the functional polymorphisms, MAOA-uVNTR and COMT-V158M. CSF was obtained by lumbar puncture. Relationships of the two polymorphism to monoamine metabolites: HVA, 5-HIAA, and MHPG were examined. The higher-expressing MAOA-uVNTR genotype was associated with higher CSF-HVA levels in males only (n = 46) (195.80 pmol/ml, SD = 61.64 vs. 161.13, SD = 50.23, respectively; P = 0.042). No association was found with diagnosis. COMT-V158M had no association with CSF monoamine metabolites. The association of MAOA-uVNTR with dopaminergic activity in males is a preliminary finding that needs to be replicated in a larger sample of Caucasian males and relationships sought with clinical phenotypes. This article contains supplementary material, which may be viewed at the American Journal of Medical Genetics website at http://www.interscience.wiley.com/jpages/0148-7299:1/suppmat/index.html.