Arno G. Motulsky

Werner's syndrome a review of its symptomatology, natural history, pathologic features, genetics and relationship to the natural aging process.

Werner’s syndrome was first described in 1904 by Otto Werner in his doctoral thesis, “Uber Katarakt in Verbindung mit Sklerodermie” (“Cataract in combination with scleroderma”) (137). He reported four sibs with similar clinical findings: shortness of stature; senile appearance; graying of the hair beginning at about age 20; cataracts appearing during the third decade; skin changes (tautness, atrophy, hyperkeratoses and ulceration) designated as scleroderma and primarily involving the feet and, to a lesser degree, the hands; joint deformities associated with the skin abnormalities; atrophy of the muscles and connective tissues of the extremities; and early cessation of menstruation. Werner was impressed principally by the cataracts, skin changes, senile appearance, and graying of the hair and attributed the condition to a “failure” of the cells derived from the ectoderma. Although he knew that the features displayed by the affected members of the family represented a new and distinct entity, he related this condition to one described by Rothmund (106) in which juvenile cataracts were found together with skin changes. The implied association of these two syndromes and the identification of the skin alterations in Werner’s cases as scleroderma were sources of confusion for many years, and it was not until the appearance of the paper by Oppenheimer and Kugel in 1934 (94) and of the comprehensive study by Thannhauser in 1945 (131) that the two syndromes were clearly delineated and the character of the skin changes defined.

Spectrophotometric assays for the enzymatic hydrolysis of the active metabolites of chlorpyrifos and parathion by plasma paraoxonase/arylesterase.

Human serum plasma paraoxonase/arylesterase exhibits a genetic polymorphism for the hydrolysis of paraoxon. One allelic form of the enzyme hydrolyzes paraoxon slowly with a low turnover number and the other(s) hydrolyzes paraoxon rapidly with a high turnover number. Chlorpyrifos-oxon, the active metabolite of the insecticide chlorpyrifos (Dursban), is also hydrolyzed by plasma arylesterase/paraoxonase. A specific assay for measuring hydrolysis of this compound is described. This assay is not subject to interference by the esterase activity of serum albumin. The Km for chlorpyrifos-oxon hydrolysis was 75 microM. Hydrolysis was inhibited by phenyl acetate, EDTA, and organic solvents. Enzyme activity required calcium ions and was stimulated by sodium chloride. Hydrolysis was optimized by using methanol instead of acetone to dissolve substrate. Unlike the multimodal distribution of paraoxonase, the distribution of chlorpyrifos-oxonase activity failed to show clear multimodality. An improvement in the assay for hydrolysis of paraoxon by plasma arylesterase/paraoxonase was achieved by elimination of organic solvents. Plotting chlorpyrifos-oxonase activity vs paraoxonase activity for a human population using the new assay conditions provided an excellent resolution of low activity homozygotes from heterozygotes for this allele. A greater than 40-fold difference in rates of chlorpyrifosoxon hydrolysis observed between rat (low activity) and rabbit sera (high activity) correlated well with the reported large differences in LD50 values for chlorpyrifos in these two animals, consistent with an important role of serum paraoxonase in detoxification of organophosphorus pesticides in vivo.

Reporting Genetic Results in Research Studies: Summary and Recommendations of an NHLBI Working Group

Prospective epidemiologic studies aid in identifying genetic variants associated with diseases, health risks, and physiologic traits. These genetic variants may eventually be measured clinically for purposes of diagnosis, prognosis, and treatment. As evidence of the potential clinical value of such information accrues, research studies face growing pressure to report these results to study participants or their physicians, even before sufficient evidence is available to support widespread screening of asymptomatic persons. There is thus a need to begin to develop consensus on whether and when genetic findings should be reported to participants in research studies. The National Heart, Lung, and Blood Institute (NHLBI) convened a Working Group on Reporting Genetic Results in Research Studies to discuss if, when, and how genetic information should be reported to study participants. The Working Group concluded that genetic test results should be reported to study participants when the associated risk for the disease is significant; the disease has important health implications such as premature death or substantial morbidity or has significant reproductive implications; and proven therapeutic or preventive interventions are available. Finally, the Working Group recommended procedures for reporting genetic research results and encouraged increased efforts to create uniform guidelines for this activity. Published 2006 Wiley‐Liss, Inc.

Serum paraoxonase and its influence on paraoxon and chlorpyrifos-oxon toxicity in rats

Paraoxon and chlorpyrifos-oxon, the active metabolites of the organophosphorus insecticides parathion and chlorpyrifos, respectively, are hydrolyzed by an A-esterase, paraoxonase, which is present in the sera of several mammalian species. In this study, we investigated whether levels of serum paraoxonase activity in laboratory animals can influence the in vivo toxicity of paraoxon and chlorpyrifos-oxon. Paraoxonase was found to be 7-fold higher in rabbit serum than in rat serum. The dose of paraoxon required to produce similar signs of toxicity and similar degrees of cholinesterase inhibition in rats and rabbits (0.5 and 2.0 mg/kg, respectively) differed by 4-fold. Paraoxonase was then purified from rabbit serum and 8.35 units was injected in the tail veins of rats, increasing the peak hydrolytic activity of rat serum by 9-fold toward paraoxon and by 50-fold toward chlorpyrifos-oxon. The increase in serum paraoxonase/chlorpyrifos-oxonase activity was long-lasting, with a 2- and 10-fold increase, respectively, still present after 24 hr. Thirty minutes following enzyme injection, rats were challenged with an acute dose of paraoxon or chlorpyrifos-oxon given by the intravenous, intraperitoneal, dermal, or oral route. Cholinesterase activities were measured in plasma, red blood cells, brain, and diaphragm after 4 hr. Rats pretreated with paraoxonase exhibited less inhibition of cholinesterase than vehicle-treated controls following identical doses of paraoxon, particularly when the organophosphate was given iv or dermally. A very high degree of protection, particularly toward brain and diaphragm cholinesterase, was provided by paraoxonase pretreatment in animals challenged with chlorpyrifos-oxon by all routes. These results indicate that levels of serum paraoxonase activity can affect the toxicity of paraoxon and chlorpyrifos-oxon.

Genetic counseling and screening of consanguineous couples and their offspring: Recommendations of the national society of genetic counselors

The objective of this document is to provide recommendations for genetic counseling and screening for consanguineous couples (related as second cousins or closer) and their offspring with the goals of1. providing preconception reproductive options2. improving pregnancy outcome and identifying reproductive choices3. reducing morbidity and mortality in the 1st years of life, and4. respecting psychosocial and multicultural issues.The recommendations are the opinions of a multicenter working group (the Consanguinity Working Group (CWG)) with expertise in genetic counseling, medical genetics, biochemical genetics, genetic epidemiology, pediatrics, perinatology, and public health genetics, which was convened by the National Society of Genetic Counselors (NSGC). The consensus of the CWG and NSGC reviewers is that beyond a thorough medical family history with follow-up of significant findings, no additional preconception screening is recommended for consanguineous couples. Consanguineous couples should be offered similar genetic screening as suggested for any couple of their ethnic group. During pregnancy, consanguineous couples should be offered maternal–fetal serum marker screening and high-resolution fetal ultrasonography. Newborns should be screened for impaired hearing and detection of treatable inborn errors of metabolism. These recommendations should not be construed as dictating an exclusive course of management, nor does use of such recommendations guarantee a particular outcome. The professional judgment of a health care provider, familiar with the facts and circumstances of a specific case, will always supersede these recommendations.

Position of a 'green-red' hybrid gene in the visual pigment array determines colour-vision phenotype

The X-linked red- and green-pigment genes are arranged in a head-to-tail tandem array. The colour-vision defect of deuteranomaly (in 5% of males of European descent) is associated with a 5´-green-red-3´ visual-pigment hybrid gene, which may also exist in males with normal colour vision. To explain why males with a normal red, a normal green and a green-red hybrid gene may have either normal or deutan colour vision, we hypothesized that only the first two genes are expressed and deuteranomaly results only if the green-red hybrid gene occupies the second position and is expressed preferentially over normal green-pigment genes occupying more distal positions. We used long-range PCR amplification and studied 10 deutan males (8 deuteranomalous and 2 deuteranopic) with 3 visual pigment genes (red, green and green-red hybrid) to investigate whether position of the hybrid gene in the array determined gene expression. The green-red hybrid gene was always at the second position (and the first position was always occupied by the red gene). Conversely, in two men with red, green and green-red hybrid genes and normal colour vision, the hybrid gene occupied the third position. When pigment gene mRNA expression was assessed in post-mortem retinae of three men with the red, green and green-red genotype, the green-red hybrid gene was expressed only when located in the second position. We conclude that the green-red hybrid gene will only cause deutan defects when it occupies the second position of the pigment gene array.

Equal proportion of adult male and female homozygous for the 677C T mutation in the methylenetetrahydrofolate reductase polymorphism

Evidence suggests that a polymorphism of the autosomal gene encoding for 5,10 methylenetetrahydrofolate reductase (MTHFR) [Frosst et al., 1995] gives rise to a thermolabile form [Kang et al., 1988] of the enzyme that in the homozygous state is associated with increased levels of homocysteine under conditions of less than optimal folate nutrition [Jacques et al., 1996]. This polymorphism is due to a C!T substitution at nucleotide 677 which converts an alanine to valine in a conserved portion of themolecule [Frosst et al., 1995] and appears to be a risk factor for increased plasma levels of homocysteine and vascular diseases [Boushey et al., 1995; Jacques et al., 1996; Kluijtmans et al., 1997]. In a 1999 letter to the Editor of the American Journal of Medical Genetics, RimaRozen et al. presented data examining the frequencies of the three methylenetetrahydrofolate reductase (MTHFR) genotypes in newborn healthy infants ascertained by the California Birth Defects Monitoring Program [Rozen and Shaw, 1999]. It was suggested that homozygosity for the common 677 C!Tmutation inMTHFR genewasmore frequent among newbornmales than among newborn females. The apparent gender difference was observed among 915 newborn infants used as control populations in studies of an association between the MTHFR polymorphism and neural tubedefects.RozenandShaw [1999] stratified this groupof 915 newborn control healthy infants by MTHFR genotypes and found that among 150 infants who had the TT variant for MTHFR only 50 (33%) were female. This was significantly less (P< 0.01) than the expected 50% of female infants. Weexamined the frequencies of the threeMTHFRgenotypes in 559 healthy, Caucasian, male and female adult volunteers from Seattle, WA for a controlled intervention study of homocysteine response to folic acid supplementation with variable dosage. As shown in Table I, and similar to the findings of Rozen and Shaw [1999], we detected a significantly lower proportion of females than males to be homozygous for the 677C!Tmutation inMTHFR. Among the 173 males and 386 females analyzed, we found 13.9% of male volunteers were TT homozygotes in comparison to 7.8% of female volunteers (Chi square: P< 0.05). We also found that the T allele relative frequency is significantly different betweenmales and females (P1⁄4 0.02). These results suggest some variation in our data in the MTHFR genotypes due to gender. We hypothesized that theremay be two possible reasons for the observed reduction in frequency ofMTHFR TT homozygotes in females. The first is a possible prenatal selection against TT female homozygotes, and the second is a possible higher T allele frequency in males than females. To explore the observed reduction in frequency of MTHFR TT homozygotes in females, we conducted a literature search for studies specifying MTHFR genotypes and gender for healthy adult individuals, typically from population and case-control studies.Weassumed that a sex difference observed at birth would survive into adulthood since we know of no postnatal condition associated with the MTHFR polymorphism that would eliminate such differences during childhood. The keywords used to produce a primary list in the PubMed literature search were MTHFR, gender, and sex. Two articles were carefully reviewed for related articles [Slattery et al., 1999;Ulrich et al., 2000]. Fromthis search, the list of articles in Table II was generated and was considered representative of the literature on the subject [Adams et al., 1996; Brugada and Marian, 1997; Christensen et al., 1997; Galinsky et al., 1997; Heijmans et al., 1999; Slattery et al., 1999; Stegmann et al., 1999; Chango et al., 2000; Delvin et al., 2000; D’Angelo et al., 2000; Ho, 2000; Hustad et al., 2000; Ulrich et al., 2000; Dekou et al., 2001; Dierkes et al., 2001; Guillen et al., 2001; Kimura et al., 2001; Saw et al., 2001; Wu et al., 2001; Beresford, 2004 unpublished data]. Each article was examined for information onMTHFR genotypes and gender. Table II shows the numbers and percentages of males and females with TT homozygosity for the MTHFR 677 C!T polymorphism, the total number of males and females, age group, and geographic and ethnic origin for each study. We show race/ethnicity data because the incidence of this genetic polymorphism varies among populations.Weshowgeographic originbecause theallele frequencies of theMTHFR 677C!Tpolymorphism also vary significantly between populations from different geographic areas. For example, the T allele frequency varies from 22 to 45% between populations from northern and southern European countries, respectively [Andreassi et al., 2003]. Based on data from these studies, we show no consistent gender difference in homozygosity for the common 677 C!T mutation in MTHFR gene. If the studies are combined, as indicated at the bottom of Table II, the TT genotype frequency is almost the same in males and females (11.6 and 11.5%, respectively). Assessing only studies with a total of over 100 males and 100 females from Table II, similar results were obtained (data not shown). We also calculated the predicted distributions of the genotypes for each gender using the relative frequencies of the C and T allele and the Hardy– Weinberg equation. We found that the predicted distributions are in complete accord with the observed distributions shown in Table I. The principles of the Hardy–Weinberg equation apply in these data suggesting there is no prenatal selection Cheryl A.M. Anderson and Arne Lund Jorgensen completed the work while at the University of Washington, School of Public Health and Community Medicine (CA) and Division of Medical Genetics (ALJ).

Theophylline metabolism: Variation and genetics

Variation of theophylline metabolism in 54 healthy, nonmedicated adults (13 monozygotic [MZ] twin pairs, 11 dizygotic [DZ] twin pairs, and 6 single individuals) was assessed by kinetic study. Elimination rate constant, clearance (CI), t½, and apparent volume of distribution, as well as urine excretion of unchanged theophylline and of the three major metabolites (1‐methyluric acid, 3‐methyl‐xanthine, and 1,3‐dimethyluric acid) were studied. Smokers and men had increased theophylline elimination rates compared to nonsmokers and women. Identical (MZ) twins resembled each other more closely than nonidentical (DZ) twins in the various kinetic parameters, but mean intrapair differences between MZ and DZ twins for all but one of the serum and urinary parameters examined (including t½) were not statistically significant. Correspondingly, estimates of heritability and of intrapair correlation coefficients showed a smaller contribution of genetic factors to variation in theophylline metabolism than had been reported for other drugs investigated by twin studies. Nevertheless, in the family of the individual with the longest theophylline t½, the operation of a rare major gene retarding theophylline metabolism could not be excluded. A father and two out of four children had very slow Cls. This finding would be consistent with, but does not prove, monogenic inheritance.

Low-Density Lipoprotein Particle Size Loci in Familial Combined Hyperlipidemia Evidence for Multiple Loci From a Genome Scan

Objective—Low-density lipoprotein (LDL) size is associated with vascular disease and with familial combined hyperlipidemia (FCHL). Methods and Results—We used logarithm of odds (lod) score and Bayesian Markov chain Monte Carlo (MCMC) linkage analysis methods to perform a 10-cM genome scan of LDL size, measured as peak particle diameter (PPD) and adjusted for age, sex, body mass index, and triglycerides in 4 large families with FCHL (n=185). We identified significant evidence of linkage to a chromosome 9p locus (multipoint lodmax=3.70; MCMC intensity ratio [IR]=21) in a single family, and across all 4 families to chromosomes 16q23 (lodmax=3.00; IR=43) near cholesteryl ester transfer protein (CETP) and to 11q22 (lodmax=3.71; IR=120). Chromosome 14q24-31, a region with previous suggestive LDL PPD linkage evidence, yielded an IR of 71 but an lodmax=1.79 in the combined families. Conclusions—These results of significant evidence of linkage to 3 regions (9p, 16q, and 11q) and confirmatory support of previous reported linkage to 14q in large FCHL pedigrees demonstrate that LDL size is a trait influenced by multiple loci and illustrate the complementary use of lod score and MCMC methods in analysis of a complex trait.

Molecular genetics of human color vision

The significant advances in our understanding of color vision has been due to the convergence of information from behavioral and molecular genetic analyses. The molecular biology of the visual pigments; molecular genetic basis of variation in normal and abnormal color vision, and regulation of the genes at the LWS-MWS pigment gene locus are discussed.