Evidence for genetic control of changes in f-actin polymerization caused by pathogenic microorganisms: in vitro assessment using gingival fibroblasts from human twins

Attachment to and migration upon a substratum, as well as other functions of connective tissue cells, are regulated mainly by cytoplasmic structural proteins, particularly filamentous actin (f-actin). Pathogenic microorganisms exert negative effects on cytoskeletal proteins. In the present study, normal gingival fibroblasts from 10 sets of human twins (6 fraternal, DZ; 4 identical, MZ) were exposed to soluble extracts from Porphyromonas gingivalis or Fusobacterium nucleatum, then f-actin was stained using FITC-labeled phalloidin. Cells were examined under fluorescence, and a computer-assisted image analyzer quantitated f-actin polymerization as fluorescence intensity on a per-cell basis. Intraclass correlation coefficients for f-actin in MZ/MZ vis-a-vis DZ/DZ paired cell cultures were determined to assess the possible heritability of responses to the microorganism preparations. F-actin labeling was significantly different between control cultures and those exposed to the extracts. Both F. nucleatum and P. gingivalis effected f-actin and fibroblast morphology. When the data were adjusted for gender and age effects, and for differences in control f-actin levels, fibroblasts from MZ twin pairs were moderately similar in both absolute and relative responses to bacterial challenges; cells from DZ twins showed little similarity when response was measured on the absolute scale, and moderate similarity using the relative scale.

Relationship between T2-weighted hyperintensities (unidentified bright objects) and lower IQs in children with neurofibromatosis-1

To address the controversy regarding the relationship between cognitive impairment (lowering of IQ) and magnetic resonance imaging (MRI) characteristics (T2-weighted hyperintensities or unidentified bright objects [UBOs]) in children with neurofibromatosis-1 (NF-1), we used a pairwise NF-1/ sibling design; we set out to predict the lowering of IQ in each child with NF-1 as a discrepancy from the IQ of an unaffected sibling (D-SIQ). Our multiple regression model included the age of the child with NF-1, familial or sporadic nature of the NF-1, number of locations in the child's brain occupied by T2-weighted hyperintensities (UBOs), and the volumetric percentage of brain tissue occupied by T2-weighted hyperintensities (UBOs). Only the number of locations occupied by UBOs accounted for IQ lowering (D-SIQ) in children with NF-1 (42% of the variance in D-SIQ). This is the first report to confirm that a continuum of lowered IQs in NF-1-affected children exists in relation to the distribution of UBOs (range 0-7), not just presence (vs. absence) of any UBOs.

Executive function in children with Tourette syndrome and/or attention deficit hyperactivity disorder

Tourette Syndrome (TS) in children is associated with various neurobehavioral disorders including attention deficit hyperactivity disorder (ADHD). Children with TS and ADHD show some difficulties with neuropsychological tasks, but we do not know if children with TS alone have neuropsychological deficits. To assess specific cognitive differences among children with TS and/or ADHD, we administered a battery of neuropsychological tests, including 10 tasks related to executive function (EF), to 10 children with TS-only, 48 with ADHD-only, and 32 with TS + ADHD. Children in all groups could not efficiently produce output on a timed continuous performance task [Test of Variables of Attention (TOVA) mean reaction time and reaction time variability]. Children with TS-only appeared to have fewer EF impairments and significantly higher perceptual organization scores than children with TS + ADHD or ADHD-only. These findings suggest that deficiencies in choice reaction time and consistency of timed responses are common to all three groups, but children with TS-only have relatively less EF impairment than children with TS + ADHD or ADHD-only.

Genetic influences in caries and periodontal diseases

Deciphering the relative roles of heredity and environmental factors ("nature vs. nurture") in the pathogenesis of dental caries and diseases of the periodontium has occupied clinical and basic researchers for decades. Success in the endeavor has come more easily in the case of caries; the complex interactions that occur between host-response mechanisms and putative microbiologic pathogens in periodontal disease have made elucidation of genetic factors in disease susceptibility more difficult. In addition, during the 30-year period between 1958 and 1987, only meager resources were targeted toward the "nature" side of the nature/nurture dipole in periodontology. In this article, we present a brief history of the development of genetic epistemology, then describe the three main research mechanisms by which questions about the hereditary component of diseases in humans can be addressed. A critical discussion of the evidence for a hereditary component in caries susceptibility is next presented, also from a historical perspective. The evolution of knowledge concerning possible genetic ("endogenous", "idiotypic") factors in the pathogenesis of inflammatory periodontal disease is initiated with an analysis of some foreign-language (primarily German) literature that is likely to be unfamiliar to the reader. We identify a turning point at about 1960, when the periodontal research community turned away from genetics in favor of microbiology research. During the past five years, investigators have re-initiated the search for the hereditary component in susceptibility to common adult periodontal disease; this small but growing body of literature is reviewed. Recent applications of in vitro methods for genetic analyses in periodontal research are presented, with an eye toward a future in which persons who are at risk--genetically predisposed--to periodontal disease may be identified and targeted for interventive strategies. Critical is the realization that genes and environment do not act independently of each other; the appearance or magnitude of heritability may differ with various environments.

Glutathione S-transferase M1 (GSTM1) deficiency and lung cancer risk

The association between glutathione S-transferase M1 (GSTM1) deficiency and lung cancer risk has been controversial in the published literature. To examine this controversy, 12 case-control studies of GSTM1 status and lung cancer risk were identified in the published English literature. These studies included a total of 1593 cases and 2135 controls. We conclude that GSTM1 deficiency is a moderate risk factor for lung cancer development with an odds ratio of 1.41 (95% confidence interval = 1.23-1.61; P < 0.0001) by using Mantel-Haenszel methods for stratified analysis. This increased risk is evident for all the major histological subtypes of lung cancer. Although the increased risk is small, GSTM1 deficiency accounts for approximately 17% of lung cancer cases because of the high prevalence of GSTM1 deficiency.

Rett syndrome studies of natural history and search for a genetic marker

The commonly held notion that Rett syndrome (RS) is a neurodegenerative disorder with normal early development was examined by an epidemiological survey and review of medical records and serial neurological and development evaluations. In some subjects, deviance from normal development was evident from the perinatal period, and gradually became more prominent with age. These findings are convincing when seen in conjunction with a reduction in velocity of brain growth, as early as 2-4 months of life, well before the recognition of gross neurological deficits. Neurodevelopmental evaluations provide no indication that there is progressive loss of adaptive behaviors, or communication skills to indicate a neurodegenerative process. Taken together with the known neuropathological and neurochemical changes in RS brain we hypothesize that RS is a neurodevelopmental disorder, which has a genetic basis, and affects subsets of neurons and their connections during a period of vigorous brain growth, when synapse formation and pruning are at a peak. Studies of mitochondrial (mt) DNA in brain to understand the genetic mechanisms underlying matrilineal inheritance in the few familial cases, and mt structural and enzyme deficiencies have been unrevealing to date.

Heart mass and blood pressure have separate genetic determinants in the New Zealand genetically hypertensive (GH) rat

OBJECTIVE

To determine associations between cardiovascular parameters and genotype in 205 F2 rats of both sexes and lineages from reciprocal crosses made between rats of the New Zealand genetically hypertensive (GH) and Brown Norway (BN) rat strains.

METHODS

Systolic tail blood pressure, mean arterial blood pressure, pulse rate, heart mass, body mass and relative heart mass were determined for each rat in the age range 17-19 weeks, and DNA polymorphisms were examined for the guanylyl cyclase A (GCA), angiotensin converting enzyme (ACE) and renin (REN) genes.

RESULTS

The phenotypic data indicated the presence of genes on the X and Y chromosomes that affected blood pressure. The GH GCA allele, in males only, and the GH ACE allele, in females only, both cosegregated with increased blood pressure. The ACE effect was confined to rats of one lineage only, namely those with GH grandfathers. A cosegregation of the GH REN allele with decreased blood pressure was also detected in females with BN grandfathers. In contrast, the GH REN allele cosegregated with a smaller heart in males only, whereas the GH ACE allele cosegregated with a larger heart both in males and in females. In males this was the consequence of a decrease in body mass with no change in absolute heart mass, whereas in females there were changes in both of these parameters.

CONCLUSIONS

The results show that cardiac hypertrophy and blood pressure have independent genetic determinants in the GH rat, and indicate the importance of sex in determining the phenotypic expression of genes underlying cardiovascular pathology.

Familial clustering of breast cancer: possible interaction between DNA repair proficiency and radiation exposure in the development of breast cancer

The capacity of peripheral blood lymphocytes to repair X-ray-induced DNA damage, manifest as chromatid damage 30-90 min after G2-phase X-irradiation, was measured among available members of a family exhibiting a cluster of breast-cancer cases occurring in one generation. The cancer patients had been exposed to repeated chest fluoroscopic examinations during early childhood and adolescence. The development of breast cancer was correlated with DNA repair proficiency and history of radiation exposure. The results of the family study provide preliminary support for the hypothesis that a deficiency in repair of X-irradiation DNA damage may be a susceptibility factor for the development of breast cancer. This hypothesis, however, requires confirmation in a larger study. Studying the combined effect of susceptibility factors and environmental exposures may enhance our knowledge of the etiology of breast cancer and provide leads for effective prevention strategies aimed at reducing exposures or altering susceptibility to unavoidable exposures.

An analysis of two discrepancy-based models and a processing-deficit approach in identifying learning disabilities

The incidence of learning disabilities (LD) in a research center sample of 107 boys and 103 girls between 6 and 12 years of age was calculated using Wechsler IQ and Woodcock-Johnson cluster scores in a regression model (REG) and a reliability model (REL). The REL method identified LD three times more often than the REG method, and all those identified by REG were also identified by REL. When stratified by IQ, REG and REL identified similar percentages in the lowest IQ group; however, REG identified at a lower rate as IQ increased. All 87 children identified with reading disabilities (both REL-RD and REG-RD) were weak to a similar extent on phonemic awareness. Comorbid elevated attention ratings were found in 62% of children with RD; 26% had elevated attention ratings but no linguistic processing deficits, and 21% had at least one linguistic processing deficit but no attentionally suspect rating.

Neurofibromatosis type 1: the cognitive phenotype

Visuospatial deficits have been reported in patients with neurofibromatosis type 1 (NF 1), although detailed observations regarding academic achievement are conflicting. Using neurocognitive testing and magnetic resonance imaging, we studied 12 families, each comprising one child with NF 1, an unaffected sibling of the same age range (6 to 16 years), and both biologic parents. The Full Scale IQ ranged from 70 to 130 among children with NF 1 and from 99 to 139 among unaffected siblings. A significant (p < 0.01) pairwise difference was found between each child with NF 1 and sibling on the Full Scale IQ and the Verbal IQ. On a single visuospatial test, Judgement of Line Orientation, children with NF 1 did significantly worse than siblings (p < 0.01). Children with NF 1 had significant learning disabilities in written language and reading (p < 0.05) and in neuromotor dysfunction (p < 0.005) compared with siblings. A significant correlation was found between the pairwise lowering of the Full Scale IQ and Judgment of Line Orientation scores in children with NF 1 and the number of locations in which, on magnetic resonance imaging, T2-weighted hyperintensities were seen (Full Scale IQ: p < 0.0003; Judgment of Line Orientation score: p < 0.02). We conclude that NF 1 is associated with a significantly lower Full Scale IQ, multifocal cognitive deficits (Verbal IQ, Judgment of Line Orientation score), reading disability, and neuromotor deficit. Pairwise cognitive differences correlated with the number of brain lesions on magnetic resonance imaging.

Racial differences in the relationship between blood pressure and risk of retinopathy among individuals with NIDDM

OBJECTIVE

To assess whether the prevalence of retinopathy differs between blacks and whites with diabetes and to examine differences between blacks and whites in the relationship between risk factors for and prevalence of retinopathy. Population data suggest diabetic retinopathy is either more prevalent or more severe in blacks than in whites.

RESEARCH DESIGN AND METHODS

We analyzed data from a screening study for retinopathy among patients with diabetes, conducted in Maryland from 1986-1990.

RESULTS

After adjusting for age, duration of diabetes, type of treatment for diabetes, and presence or absence of high blood pressure, black men with NIDDM were approximately 23% more likely to have retinopathy than other race-sex groups (not statistically significant). We also found a different relationship between systolic blood pressure and retinopathy prevalence in blacks than in whites among individuals with NIDDM. Among blacks, the risk increased as systolic blood pressure increased, even within the normal range, and reached statistical significance at > 150 mmHg. Among whites, the risk was increased only among those with high systolic blood pressure (> 140 mmHg) and did not reach statistical significance.

CONCLUSIONS

Our data are consistent with the hypothesis that differences exist between blacks and whites in risk of diabetic retinopathy, and that the effect of blood pressure on risk of retinopathy differs between blacks and whites.

Volumetric MRI changes in basal ganglia of children with Tourette's syndrome

To define the site of pathology in Tourette's syndrome (TS), we performed a volumetric MRI study of basal ganglia structures and lateral ventricles on 37 children with this disorder and 18 controls. There were no statistically significant differences in the size of the right or left caudate, putamen, globus pallidus, or ventricles in these populations. In contrast, there were significant differences for measures of symmetry in the putamen and the lenticular region. Virtually all controls (17 right- and one left-handed) had a left-sided predominance of the putamen, whereas in 13 of 37 TS subjects, a right predominance exceeded that of any control. Statistical comparisons among TS patients, with (n = 18) or without (n = 19) attention-deficit hyperactivity disorder (ADHD), and controls showed significant differences for the volume of the left globus pallidus and for lenticular asymmetry. Post hoc evaluations showed that in the TS + ADHD group, the volume of the left globus pallidus was significantly smaller than the volume of the right and that lenticular asymmetry was due to a greater right-sided predominance in the TS+ADHD group. This study lends further support to proposals that claim the basal ganglia is involved in the pathogenesis of TS and also suggests that the comorbid problem of ADHD is related to regional changes that differ from those primarily associated with tics.

SA gene and blood pressure cosegregation using Dahl salt-sensitive rats

Based on the published cDNA base sequence for the (anonymous) SA gene, a polymerase-chain-reaction (PCR) product from the SA gene was obtained from a Dahl salt-sensitive rat kidney cDNA library. Compared to the published sequence, this product had a 102 base pair insert in the 3' end of the cDNA, probably as the result of alternate mRNA splicing. A StuI restriction fragment length polymorphism detected three alleles among various rat strains using this PCR SA gene probe. Alleles at the SA locus strongly cosegregated with blood pressure (P = .0012) in a salt-fed F2 population derived from crossing Dahl S and Lewis rats. In contrast, a cosegregation analysis of blood pressure and SA alleles in salt-fed F2 rats derived from a Dahl S x Wistar-Kyoto cross gave a negative cosegregation result. It is concluded that in certain genetic backgrounds the SA gene (or a closely linked gene) can contribute a significant component of genetic hypertension.

Segregation analysis of hypospadias: a reanalysis of published pedigree data

Little is known about the cause of hypospadias, one of the most common urogenital anomalies in males. Familial clustering of hypospadias is well recognized, with heritability estimated to be about 70% under a simple multifactorial threshold model. Neither alternative genetic mechanisms nor shared environmental factors within families have been explored fully. To learn more about possible genetic mechanisms, we used 2 methods of segregation analysis to analyze a set of published family data. These analyses are based on the families of 103 probands with hypospadias, who were ascertained through surgery departments in Denmark [Sørensen, 1953]. Urogenital examinations were performed on 95% (n = 1,510) of available male relatives, and 2.2% were found to have hypospadias. Within the probands' nuclear families, 12% of nonproband sons of normal fathers were affected. Using the mixed model of inheritance, both the autosomal dominant (AD) and codominant models fit these data better than either autosomal recessive (AR) or multifactorial models. Using the regressive logistic models, both AD and AR models were equally likely, and a model of nonMendelian sibship clustering gave a better fit to these data. These inconsistent findings illustrate the difficulties commonly encountered in segregation analysis. Using 2 different statistical approaches, we found 2 different explanations, both of which differ from the autosomal recessive model originally suggested by Sørensen [1953]. Hypospadias in these families is almost certainly heterogeneous. Determining the cause of familial clustering of hypospadias will require careful delineation of persons with recognized syndromes from uncomplicated cases and detailed information on potential prenatal risk factors.

Clustering of high density lipoprotein cholesterol levels in premenopausal and postmenopausal female twins

Previous family and twin studies indicate that genetic variation makes an important contribution to individual variation in high density lipoprotein cholesterol (HDL) levels, even after adjustment for covariates (such as obesity and alcohol consumption) that also cluster in families. However, most studies assume that genetic mechanisms affecting variation in HDL level are the same in all subgroups of the population (e.g., men versus women, by age). Using data from the Kaiser-Permanente Women Twins Study, we found different patterns of clustering for monozygotic (MZ) and dizygotic (DZ) twins depending on menopausal status. Premenopausal MZ twins were more similar than postmenopausal MZ twins (r(i) = 0.79 and r(i) = 0.61, respectively, after adjustment for age, alcohol consumption, smoking status, degree of obesity, and leisure-time exercise); premenopausal and postmenopausal DZ twins were alike to the same extent (r(i) = 0.31 and r(i) = 0.32, respectively, adjusted as above). These data suggest that either postmenopausal MZ twins have a greater degree of shared environment than postmenopausal DZ twins (e.g., postmenopausal female hormone use) or that genetic mechanisms that affect individual variation in HDL level differ in pre- and postmenopausal women. Data were not available on postmenopausal female hormone use. If genetic mechanisms that influence variation in HDL levels differ between pre- and postmenopausal women, genetic epidemiologic methods that assume that genetic and environmental sources of variation are the same for all groups of individuals may lead to false conclusions.

Exclusion of linkage between familial Mediterranean fever and the human serum amyloid A (SAA) gene cluster

We studied the relationship between the autosomal recessive trait familial Mediterranean fever (FMF) and the serum amyloid A (SAA) genes by comparing alleles of a highly polymorphic dinucleotide repeat and a conventional restriction fragment length polymorphism (RFLP) in the SAA gene cluster in Israeli FMF kindreds. By haplotype analysis, our data indicate a minimum crossover frequency of 22% between the SAA gene marker and FMF. By conventional linkage analysis this eliminates a minimum of 10.4 cM including and surrounding the SAA gene cluster as the site of the FMF mutation although SAA proteins are prominent physiologic markers of the acute attacks.

Using log-linear models to test for associations among congenital malformations

Log-linear models can be used to test for pairwise associations and higher order interactions among anatomically distinct birth defects or congenital malformations. A log-linear model, including terms for every possible pairwise association among seven severe and easily detectable congenital malformations, was examined using data on 16,217 infants registered in the Metropolitan Atlanta Congenital Defects Program between 1968 and 1986. The resulting model showed clear patterns of strong association between some congenital malformations and not others, and the presence of 3-way interaction terms where the association between two malformations depended on the presence of a third. Examining a more parsimonious log-linear model showed overlapping patterns of pairwise association involving anal-rectal atresia and omphalocele, anal-rectal atresia and limb deficiency, and anal-rectal atresia and tracheaesophageal fistula. A second common pattern involved a triangular cluster with a hierarchical relationship among the three malformations (where there was a strong association between the first and second malformations and between the first and third malformations, but the association between the second and third was only seen in the absence of the first). Three such overlapping triangular clusters were identified from these data: neural tube defects, oral clefts, and omphalocele; neural tube defects, oral clefts, and limb deficiency; and limb deficiency, diaphragmatic hernia, and neural tube defects.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of family history information in case-control cancer studies

Evidence for the genetic basis of cancer has increased in recent years, and thus, assessing familial aggregation may play an important role in epidemiologic studies. To assess the degree to which family history variables are collected in cancer case-control studies, the authors conducted a literature review of studies published in six journals during 1982-1984. Only 25% of these included a family history component. The authors review some of the literature in favor of inclusion of family information and argue for its routine collection in cancer case-control studies.

Familiality of breast cancer and socioeconomic status in blacks

Familial patterns of the occurrence of breast cancer were studied in a population-based case-control series of black women from the Cancer and Steroid Hormone study. The risks of breast cancer among relatives of breast cancer cases were compared to those of controls who were matched for age and locale. Using the term "proband" to indicate either case or control status, significant predictors of risk to the relatives of probands included case/control status of the proband and the number of years of education completed by the proband. Genetic segregation analysis of the case families using external risks generated from SEER data indicated that the familial aggregation was consistent with Mendelian recessive transmission of a single major gene. The use of internally estimated risks, which are much less stable than the SEER risks, no longer permitted discrimination among the major locus models examined. To avoid possible reporting bias, we also performed segregation analysis on families of probands who had completed at least 12 years of education. The results from this analysis reflected the results from the entire data.

Differences in mitogenic responses to angiotensin II, calf serum and phorbol ester in vascular smooth muscle cells from two strains of genetically hypertensive rat

Vascular smooth muscle cells cultured from spontaneously hypertensive (SHR), New Zealand genetically hypertensive (GH) rat strains and their control strains (Wistar-Kyoto (WKY) and normal Wistar (N) rats) were compared for mitogenic responses [( 3H]-thymidine incorporation) to angiotensin II (AII), fetal calf serum (FCS), and the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA). SHR cells showed enhanced basal [3H]-thymidine incorporation and increased responses to all three factors. In contrast, basal and FCS-stimulated [3H]-thymidine incorporation was the same or less in GH than in N cells. However, DNA synthesis was greater in GH cells in response to AII, AII + TPA or FCS + TPA. These results suggest that vascular smooth muscle cells from both hypertensive rat strains display enhanced mitogenesis, but the enhancement occurs via different intracellular signalling pathways.