Genetics and Medicine: an evolving relationship.

The rapid expansion of knowledge in human and medical genetics has revealed at least 6 percent average heterozygosity per structural gene locus, in excess of 2300 Mendelian (single gene) variants and several hundred chromosomal variants in man. This means that with the exception of monozygous twins, no two individuals are alike in their phenotype. Therefore, each person has a relative state of health, and genetic factors contribute significantly to disease. The ubiquity of genetic diversity requires the development of services for genetic screening, diagnosis, and counseling to prevent and treat a major portion of disease in modern society. Specific programs in Quebec and Canada illustrate how individuals and populations can be served by such services. Better education of citizens and health professionals in human genetics is essential for the further improvement of genetics services in society.

A new probe for the diagnosis of myotonic muscular dystrophy.

Myotonic muscular dystrophy (DM) is the most common muscular dystrophy, affecting adults as well as children. It is inherited as an autosomal dominant trait and is characterized by variable expressivity and late age-of-onset. Linkage studies have established the locus on chromosome 19. In order to identify tightly linked probes for diagnosis as well as to define in detail the DM gene region, chromosome 19 libraries were constructed and screened for restriction fragment length polymorphisms tightly linked to DM. A genomic clone, LDR152 (D19S19), was isolated that is tightly linked to DM; recombination fraction = 0.0 (95% confidence limits 0.0-0.03); lod score, 15.4.

Contribution of hierarchical clustering techniques to the modeling of the geographic distribution of genetic polymorphisms associated with chronic inflammatory diseases in the Québec population.

OBJECTIVES: The purpose of this project was to evaluate the potential of the downward hierarchical clustering analysis (DHCA) for studying genetic heterogeneity, i.e. differences in allele frequency in subpopulations, such as the 15 public health regions of the province of Québec (Canada). METHODS: The study relied on an anonymized sample of 1,680 individuals who had participated in the Québec Heart Health Survey in 1990-1991. The genotyping of 11 variants in 8 candidate genes known to be involved in chronic inflammatory diseases, namely asthma and cardiovascular diseases, was performed using the amplification refractory mutation system and restriction fragment length polymorphism techniques. Only variants showing an allelic frequency >2% in the Québec Heart Health Survey (n = 8) were selected. DHCA techniques were then applied to model the geographical distribution of these 8 genetic variants in 15 Québec public health regions and to study genetic heterogeneity. RESULTS: The DHCA allowed to group public health regions and gene variants on the basis of genetic variability. For both asthma and cardiovascular diseases, 3 significant clusters of public health regions and 1 cluster of gene variants were identified. DISCUSSION: This study suggests that DHCA might be useful in studying genetic heterogeneity at the population level and for public health activities.

Tight linkage of creatine kinase (CKMM) to myotonic dystrophy on chromosome 19.

The myotonic dystrophy (DM) gene is localized to the proximal long arm of chromosome 19. There have been reports of tight linkage to a number of chromosome 19 markers, including APOC2 and creatine kinase muscle type (CKMM), but they did not establish orientation of the 2 markers to DM. We screened several large multi-generational DM families for linkage to a series of chromosome 19 markers including CKMM. CKMM is tightly linked to DM in these data with z(theta) = 28.41; theta = 0.01. Analysis of cross-over data indicates CKMM is on the same side and closer to DM than APOC2. Thus, CKMM is a useful probe for carrier detection studies in presymptomatic individuals as well as for prenatal diagnosis.

Genome-wide search for linkage of bipolar affective disorders in a very large pedigree derived from a homogeneous population in quebec points to a locus of major effect on chromosome 12q23-q24.

We completed a genome-wide scan for susceptibility loci for bipolar affective disorders in families derived from a rather homogeneous population in the Province of Québec. The genetic homogeneity of this population stems from the migration of founding families into this relatively isolated area of Québec in the 1830s. A possible founder effect, combined with a prevalence of very large families, makes this population ideal for linkage studies. Genealogies for probands can be readily constructed from a population database of acts of baptism and marriage from the early 1830s up to the present time (the BALSAC register). We chose probands with a DSM III diagnosis of bipolar affective disorder and who may be grouped within large families having genealogical origins with the founding population of the Saguenay-Lac-St-Jean area. Living members (n approximately 120) of a very large pedigree were interviewed using the Structured Clinical Interview for DSM III (SCID I), SCID II, and with a family history questionnaire. A diagnostic panel evaluated multisource information (interview, medical records, family history) and pronounced best-estimate consensus diagnoses on all family members. Linkage, SimAPM, SimIBD, and sib-pair analyses have been performed with 332 microsatellite probes covering the entire genome at an average spacing of 11 cM. GENEHUNTER and haplotype analyses were performed on regions of interest. Analysis of a second large pedigree in the same regions of interest permitted confirmation of presumed linkages found in the region of chromosome 12q23-q24.

Socioeconomic geographical links to human immunodeficiency virus seroprevalence among childbearing women in Montreal, 1989-1993.

BACKGROUND: To describe the socioeconomic profiles of geographical areas on Montreal Island in which human immunodeficiency virus (HIV) seropositive women delivering live births between 1989 and 1993 reside. METHODS: Leftover dried blood spot filter paper specimens collected from newborns were irretrievably unlinked from identifying information prior to testing. Seroprevalence estimates were calculated based on Western blot confirmed positive samples. Using data from the Canadian census, Revenue Canada, and provincial birth records, the socioeconomic characteristics of postal zones in which seropositive mothers reside were described. RESULTS: Montreal Island had an overall 5-year HIV seroprevalence rate estimate of 16.6 (95% CI: 14.1-19.3) per 10000 childbearing women. Areas in which at least one seropositive woman gave birth had lower mean infant birthweights and higher percentages of single mothers and single-parent families. The HIV-positive neonatal blood specimens were more likely to originate from areas where a higher proportion of residents reported less education, greater unemployment, and lower income. CONCLUSIONS: Higher HIV infection rates were found among childbearing women from lower socioeconomic areas of Montreal. Increased understanding of the relationship between socioeconomic status and HIV acquisition and transmission is required to inform the development of targeted HIV prevention programmes.

Detection of succinylacetone and the use of its measurement in mass screening for hereditary tyrosinemia.

A technique designed to measure quantitatively succinylacetone (4,6-dioxoheptanoic acid) is presented. It essentially involves the inhibition of delta-aminolevulinate dehydratase (EC 4.2.1.24) by succinylacetone. Prior to their use in the assay, the samples are heated at 100 degrees C for 30 min in order to transform all succinylacetoacetate (3,5-dioxooctanedioic acid) to succinylacetone. By this transformation of the first abnormal metabolite specific to hereditary tyrosinemia to the second and last one, which is a powerful inhibitor of delta-aminolevulinate dehydratase, we determine in one sensitive assay the total amount of both. Succinylacetone was measured in sera and urines from 19 patients with hereditary tyrosinemia. All sera and urines contained succinylacetone at concentrations ranging, respectively, from 2 to 100 mumol/l and from 190 to 6000 mumol/g creatinine. The technique was also adapted to dried blood spots on paper and was used as a test complementary to blood tyrosine determination in mass screening for hereditary tyrosinemia. A total of 2412 samples having concentrations of 60 mg/l or more of tyrosine were assayed, and ten showed the presence of succinylacetone. These were all from newborns with hereditary tyrosinemia. The test has proven to virtually eliminate false positives, and, thereby, much clerical work and parental anxiety.

Myotonic dystrophy in Quebec: geographical distribution and concept of genetic homogeneity.

The geographical distribution relative to place of residence of patients with myotonic dystrophy (MD) and admitted to a Quebec hospital during a five year period (1980-1984) is presented and discussed. The sample consists of 72 males and 68 females of varying ages over 10 years. Analysis of the data shows a North Shore distribution of patients in a cline from Saguenay-Lac-St-Jean, through Québec City and to Montréal. However, a low prevalence is apparent on the South Shore, east of Québec City, for which an historical and genealogical explanation are discussed. This geographic distribution favours the hypothesis of genetic homogeneity for the MD gene in the Québec population. A stronger second argument comes from genealogical studies of 10 families sampled from the Chicoutimi Muscular Dystrophy Clinic. Genealogical paths traced to ancestors who founded Charlevoix for these 10 families go back to a cluster of 25 founders, one of whom must have been the carrier of the MD gene. The probative third argument for genetic homogeneity comes from the allelic distribution of the apolipoprotein E (ApoE) gene in the Québec City, Saguenay and in families with MD. The ApoE locus is on chromosome 19 and closely linked to MD. In MD-affected individuals there is a linkage disequilibrium for the epsilon 4 allele while non-MD members of these families show allelic frequencies not differing significantly from the control population.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypertriglyceridemia and lower LDL cholesterol concentration in relation to apolipoprotein E phenotypes in myotonic dystrophy.

Plasma lipid, lipoprotein levels and apolipoprotein apo E phenotypes were determined in 70 patients with myotonic dystrophy (MyD) and 81 controls. Marked differences were noticed in the apo E phenotype frequencies between the two groups. Plasma triglycerides and VLDL cholesterol were higher in MyD than controls, but only the latter was related to differences in the apo E phenotypes between two groups. Accordingly, the ratio of VLDL cholesterol/plasma triglycerides was increased significantly in MyD, suggesting accumulation of intermediary density particles due to lower affinity of E2 containing lipoproteins for lipoprotein cell receptors. The LDL cholesterol concentration was lower in MyD than controls and was related to differences in the apo E phenotype frequencies between the two groups. These results indicate increased removal of LDL particles in the apo E2 phenotypes, perhaps due to upregulation of LDL (B, E) receptor activity. Plasma cholesterol and HDL cholesterol concentrations were similar in both groups. Another feature of the study was lower levels of plasma cholesterol, triglycerides, VLDL and LDL cholesterol in the homozygous E4:E4 phenotype. These results suggest increased clearance rate of both VLDL and LDL particles and support the concept that apo E4-containing lipoproteins have higher in vivo affinity for ape E and/or B, E receptors.

Myotonic dystrophy: linkage with apolipoprotein E and estimation of the gene carrier status with genetic markers.

The genes for myotonic dystrophy (MD) and for apolipoprotein E (ApoE) belong to a chromosome 19 synthenic group of markers. A familial linkage analysis between MD and ApoE was performed using the J Ott LIPED program (IBM PC/XT, April 1984) to estimate the genetic distance between these 2 genes. Of a total of 136 individuals in 11 MD families, 81 were confirmed to be affected by the disease and 41 were asymptomatic. ApoE phenotypes were determined in 115 of these 122 individuals. No recombinant was observed out of 74 meioses which were informatives for both MD and the ApoE isoproteins. A global maximal lod score Z of 19.00 was obtained at the recombination fraction theta = 0. The upper theta value at the confidence interval corresponding to the peak lod score (Z max) - 1 was 0.03. This suggests that the loci for MD and ApoE are at a distance of 0 to 0.03 Morgan. Since ApoE and apolipoprotein C2 (ApoC2) have been shown by others to be about 40 kb apart, our data are therefore consistent with the distance estimate of 0.02 Morgan reported between MD and ApoC2. The D19S19 (LDR152) polymorphic DNA sequence is also tightly linked to MD on chromosome 19. The segregation of ApoE isoproteins and of ApoC2 and D19S19 DNA polymorphism was utilized for evaluating the probability for individuals at risk of inheriting the disease gene in MD families. Data are presented on 3 families to emphasize the usefulness of genetic markers to estimate the MD gene carrier status of asymptomatic individuals and also for those presenting a partial syndrome. The limitations of such approach are also discussed.

Hereditary tyrosinemias (type I): a new vista on tyrosine toxicity and cancer.

Review of the literature of the past 40 years on tyrosine and its toxicity shows that no direct link between this aromatic amino acid and carcinogenesis has been well established. Ten years ago, studies of tyrosine toxicity in mice suggested the formation of an epoxide adduction product presumably derived from tyrosine by way of the liver microsomal detoxification system. Another study showed an increased frequency of hepatomas following long-term treatment with para-hydroxyphenyllactic acid, a tyrosine derivative occurring in the absence of p-hydroxyphenylpyruvate oxydase activity. Recently, studies on hereditary tyrosinemias (Type I) have indicated that the primary enzyme defect in these diseases is a deficiency of liver and renal fumarylacetoacetase. This results in an accumulation of natural alkylating derivatives of homogentisic acid such as maleyl- and fumarylacetoacetate in liver. Adduction of these compounds by glutathione is demonstrated by the presence of the mercapturic acid S-2-fumaryl-acetone-N-acetylcysteine in urine of patients. This adduct is also present in the urine of a number of heterozygote carriers after oral loads consisting of small quantities of homogentisic acid. In this report, we present the results of preliminary animal studies on the biochemical nature of the toxic effects of these tyrosine derivatives in these diseases along with preliminary data on the influence of fumarylacetone on protein synthesis in cultured eucaryotic cells. Fumarylacetone reacts as a natural alkylating agent and may, along with maleylacetoacetate, be responsible for the high incidence of late-onset hepatoma in the clinical chronic forms of hereditary tyrosinemias.

"Chilled" pork--Part II. Consumer perception of sensory quality.

The objective of this study was to compare consumer perception of the sensory quality of grilled Canadian pork destined for Japanese and domestic markets, with particular reference to export selection criteria imposed by Japanese importers and transportation conditions. Consumers from Quebec, Canada tasted local and export quality pork subjected to "chilled" (aged 43 days at -1.7 °C) or conventional ageing (5 days at 3.1 °C). Consumers' scores (out of 10) were higher (P<0.05) in the "chilled" than conventionally aged pork for tenderness (6.8 vs 5.7), juiciness (6.6 vs 6.0), taste liking (6.4 vs 5.9) and overall acceptability (6.7 vs 6.1). When informed that the conventionally aged, domestic quality pork was destined for the domestic market, consumer scores increased significantly (P<0.05). No effect of information was observed on the perception of the 'chilled' export quality meat, perhaps a consequence of the high sensory quality observed prior to labelling.

"Chilled" pork--Part I: Sensory and physico-chemical quality.

Chilled meat exportation comprises chilling within 48 h post-mortem to temperatures <0 °C without freezing and holding under these conditions for several weeks. The effects of this ageing on sensory quality of pork are unknown and hence the objective of this study was to compare the sensory quality of Canadian pork as found in an export (Japan) market and locally. Regardless that the Japanese market's quality criteria were met, pork sorted on-line differed (P<0.05) from that for the domestic market only for lightness, exudate and cooking loss; no differences in intramuscular fat content were observed. Overall, a trained panel scored weaker pork and meat flavours and odours in the export than the domestic pork as a result of either the quality by selection if roasted or the ageing (-1.7 °C, 43 days exported chilled or 3.1 °C, 5 days domestic) if grilled or shabu shabu. Grilled pork was also more tender, sweeter and had stronger caramel flavour with the chilled ageing.

Framing genomics, public health research and policy: points to consider.

Genetic information can be used to target interventions that improve health and prevent disease. Indeed, the results of population genomics research could be useful for public health and national pandemic plans. Yet, firm scientific evidence originating from such research and the indicators of the role of health determinants, gene-gene and gene-environment interaction remain to be assessed and validated before being integrated into pandemic plans or public health programmes. It is not clear what is the role of the State in research on the elucidation of the determinants of gene-gene and gene-environment interactions and how, when, and if such data can be accessed and used for such planning. Over a period of 3 years, we sought to address these questions by gathering data and literature relevant to research in public health genomics, preparing issues papers and, finally, consulting with stakeholders on a provisional 'points to consider' document at various times. Examining in turn the issues of privacy, State powers, stakeholder perceptions, and public participation, we propose in this article, for each of these themes, a series of recommendations aiming to provide guidance on the role of the State in the use of genomic information for public health research, prevention and planning.

Clinical characteristics of myotonic dystrophy type 1 patients with small CTG expansions.

The authors report a genotype-phenotype correlation study in 102 patients with myotonic dystrophy type 1 carrying small CTG repeat expansions. Most patients carrying 50 to 99 CTG repeats were asymptomatic, except for cataracts. Myotonia, weakness, excessive daytime sleepiness, and myotonic discharges at EMG were significantly more present in the patients with 100 to 200 CTG repeats. These findings highlight different outcomes related to the expansion size, even among small CTG expansions.

A statistical approach to field measurements of the chemical evolution of cold (<0°C) snow cover.

Two statistical methods for the analysis of data on the evolution of the chemical composition of cold snow (<0°C) in the field (Lac Laflamme, Quebec) were compared. The methods used on the data were regression analysis (One sample per sampling date over a long cold period) and ANOVA (replicate samples on a restricted number of sampling dates over shorter periods). The relative power of the tests to determine the detectable amplitude of chemical changes was derived from the theoretical power of the tests under comparable conditions of sampling (number of observations) and from the estimated error variances of the measured data.The results of the study on the evolution of sulfates (SO4) concentrations in discretely identified snow strate clearly showed that for six of the eight strata, significant losses of SO4 occurred in snow during cold periods. The relative amplitude of the significant losses varied between 1% per day and 4% per day depending on the initial concentrations in the snow and the prevailing meteorological conditions.The analysis of the data also demonstrated that for the same number of samples, the regression analysis is more efficient in detecting the chemical changes in snow than the alternative ANOVA method. The use of this information to plan sampling programs of cold snow under both field and laboratory conditions is discussed.

Ethical guideposts for allelic variation databases.

Basically, a mutation database (MDB) is a repository where allelic variations are described and assigned within a specific gene locus. The purposes of an MDB may vary greatly and have different content and structure. The curator of an electronic and computer-based MDB will provide expert feedback (clinical and research). This requires ethical guideposts. Going to direct on-line public access for the content of an MDB or to interactive communication also raises other considerations. Currently, HUGO's MDI (Mutation Database Initiative) is the only integrated effort supporting and guiding the coordinated deployment of MDBs devoted to genetic diversity. Thus, HUGO's ethical "Statements" are applicable. Among the ethical principles, the obligation of preserving the confidentiality of information transferred by a collaborator to the curator is particularly important. Thus, anonymization of such data prior to transmission is essential. The 1997 Universal Declaration on the Human Genome and Human Rights of UNESCO addresses the participation of vulnerable persons. Researchers in charge of MDBs should ensure that information received on the testing of children or incompetent adults is subject to ethical review and approval in the country of origin. Caution should be taken against the involuntary consequences of public disclosure of results without complete explanation. Clear and enforceable regulations must be developed to protect the public against misuse of genetic databanks. Interaction with a databank could be seen as creating a "virtual" physician-patient relationship. However, interactive public MDBs should not give medical advice. We have identified new social ethical principles to govern different levels of complexity of genetic information. They are: reciprocity, mutuality, solidarity, and universality. Finally, precaution and prudence at this early stage of the MDI may not only avoid ethically inextricable conundrums but also provide for the respect for the rights and interests of all those involved.