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C Derom

Publications and source records attributed to C Derom.

At least 37 records · Page 2Linked to original sources
PubMed2001

The influence of zygosity and chorion type on fat distribution in young adult twins consequences for twin studies.

An adverse intra-uterine environment has been associated with abdominal fat distribution in singletons. Twins often have a low birth weight and a short gestation. Therefore, they may have an increased risk to develop abdominal obesity. Furthermore, monozygotic monochorionic twins (MZ MC) have a larger intra-pair birth weight difference compared to monozygotic dichorionic twins (MZ DC). If adult anthropometry is programmed in utero, this may affect the intra-pair correlations in adulthood and, consequently, also the results from the classic twin method to estimate genetic and environmental influences. In the present study, we compared the absolute values, the intra-pair differences, and the intra-pair correlations of body mass, height, BMI, and abdominal fat distribution of 424 MZ MC, MZ DC and dizygotic (DZ) twin pairs (aged 18-34 yrs). DZ, MZ DC and MZ MC twins did not differ for most anthropometric characteristics. Only MZ women tended (p = 0.03) to accumulate more abdominal fat compared to DZ twins. Overall, the contribution of zygosity and chorion type to adult anthropometry was rather low (< or = 1.7%). Although the intra-pair birth weight difference of MZ MC pairs (10.5% in men, 12.3% in women) was significantly larger compared to that of MZ DC pairs (6.9% and 9.2% resp.), the intra-pair differences in adult anthropometry were similar for both MZ twin types. Also the intra-pair correlations of MZ MC and MZ DC pairs were strikingly alike, suggesting no significant influence of the prenatal environment on adult concordance. In conclusion, the substantial difference in the prenatal environment of MZ MC and MZ DC twins did not result in a difference in intra-pair concordance of adult anthropometry and fat distribution. Therefore, we suggest that the chorion type of MZ twins does not bias the twin design and the estimation of the genetic contribution to adult anthropometry.

Adipose Tissue↗
PubMed2001

Hypodontia and tooth formation in groups of children with cleft, siblings without cleft, and nonrelated controls.

OBJECTIVE: To compare the occurrence of hypodontia, dental age, and asymmetric dental development in children with cleft with their siblings and a nonsibling control group. SUBJECTS: The sample consisted of 54 children with cleft (aged 4.2 to 13.1 years), who had at least one sibling available for an orthopantomogram, 63 siblings without cleft (aged 4 to 14.9 years) and 250 controls without cleft (aged between 4 and 14.9 years). METHOD: Hypodontia, dental age, and asymmetric dental development were assessed on panoramic radiographs of the children with cleft, the siblings without cleft, and the control children without cleft. RESULTS: Both the cleft (p <.001) and the sibling group (p <.05) showed a significantly higher frequency of hypodontia and a significantly higher occurrence (cleft p <.01 and sibling group p <.001) of asymmetric dental development, compared with the control group. Only a small, but insignificant, delay in dental development could be found in the cleft and the sibling group. CONCLUSIONS; The cleft subjects with siblings showed a significantly higher occurrence of hypodontia and asymmetric dental development than the noncleft control group. This may suggest a genetic component for the occurrence of hypodontia and asymmetric dental development.

Adolescent↗
PubMed1998

Validation of a telephone zygosity questionnaire in twins of known zygosity.

The aim of this study was to validate a zygosity questionnaire that can be administered over the telephone. Mothers of same-sexed twins of known zygosity and chronicity between 2 and 31 years of age were interviewed on a nine-item questionnaire. From the answers one unweighted and four weighted indices were computed. As single questions, the mother's opinion and the "two peas in a pod" question differentiated best between monozygotic and dizygotic twins. One independent well-trained observer assessed the zygosity based on the questionnaire and made the correct diagnosis in 96% of the cases. A weighted index of eight similarity questions yielded an accuracy of 98%. This study shows that the zygosity of same-sexed twins more than 2 years old and without gross physical malformation can reliably be determined by a telephone questionnaire with a high accuracy.

Adolescent↗
PubMed1998

Univariate and multivariate genetic analysis of subcutaneous fatness and fat distribution in early adolescence.

Univariate and multivariate analyses of the genetic and environmental contributions to variance in adipose tissue and adipose tissue distribution were carried out in early adolescents. Stature, weight, body mass index (BMI), and five subcutaneous skinfolds were measured at half-yearly intervals in 105 MZ and DZ twin pairs from 10 to 14 years. The most parsimonious model, which provided an adequate explanation for variation in the BMI, five skinfolds, and the T/E ratio, included additive genetic and specific environmental factors. Multivariate analyses of the genetic architecture of subcutaneous fat indicated a general skinfold genetic factor, an extremity skinfold genetic factor, and skinfold specific genetic factors. This implies that all skinfolds are under control of the same set of genes, that a different set of genes partly controls extremity skinfolds, and that other genes have a small skinfold specific impact. Environmental contributions included a general skinfold environmental factor and skinfold specific environmental factors. BMI is under control of the same set of genes as skinfolds and shows high genetic correlations with trunk skinfolds, which implies that nearly the same genes may influence trunk skinfolds and the BMI. All models were fairly consistent across the age range.

Adipose Tissue↗
PubMed1998

A genetic study of anteroposterior and vertical facial proportions using model-fitting.

Genetic model-fitting was used to determine the heritability of anteroposterior and vertical facial proportions in twins. Lateral headplates of 33 monozygotic and 46 dizygotic twins, none of whom had undergone orthodontic treatment, were used. Five proportions, based on four vertical and five horizontal measurements, were assessed: lower facial height, anterior- to posterior-facial height, total facial height to face depth, sella-A-point to sella-B-point, and sella-upper incisal edge to sella-lower incisal edge. Reproducibility was high for all variables. Model-fitting indicated that all the facial proportions were controlled by additive genes and the specific environment. The genetic component was 71% for upper-to lower-facial height, 66% for anterior- to posterior-facial height, 62% for total facial height, and 66% for sella-A-point to sella-B-point and sella-upper incisal edge to sella-lower incisal edge.

Adolescent↗
PubMed1998

Commitment to X inactivation precedes the twinning event in monochorionic MZ twins.

To gain insight into the timing of twinning, we have examined a closely related event, X-chromosome inactivation, in female MZ twin pairs. X-inactivation patterns in peripheral blood and buccal mucosa were compared between monochorionic MZ (MC-MZ) and dichorionic MZ (DC-MZ) twins. Overall, the MC-MZ twins displayed highly similar X-inactivation patterns, whereas DC-MZ twins frequently differed in their X-inactivation patterns, when both tissues were tested. Previous experimental data suggest that commitment to X inactivation occurs when there are 10-20 cells in the embryo. Simulation of embryo splitting after commitment to X inactivation suggests that MC-MZ twinning occurs three or four rounds of replication after X inactivation, whereas a DC-MZ twinning event occurs earlier, before or around the time of X inactivation. Finally, the overall degree of skewing in the MZ twins was not significantly different from that observed in singletons. This indicates that X inactivation does not play a direct role in the twinning process, and it further suggests that extreme unequal splitting is not a common mechanism of twin formation.

Adolescent↗
PubMed1998

The East Flanders Prospective Twin Survey (Belgium): a population-based register.

The East Flanders Prospective Twin Survey (EFPTS), started in 1964, is unique among the 17 major European twin registers because it is population based, the twins (and higher order births) are ascertained at birth, basic perinatal data are collected, chorion type is established and, when appropriate, genetic markers including DNA fingerprints, are determined. The total number of sets is 5089 twin, 158 triplet and 14 of higher order. Zygosity has been diagnosed on the basis of sex, placental structure and genetic markers in more than 95% of pairs. The EFPTS is the only large register that includes placental data and allows differentiation of three subtypes of monozygotic twins based on the time of the initial zygotic division: the dichorionic-diamnionic pairs (early), the monochorionic-diamnionic pairs (intermediate), and the monochorionic-monoamnionic pairs (late). Methodology and basic results in twins are considered in this article; detailed studies will be reported later. The sex proportion in dizygotic (DZ) twins is the same as in singletons, whereas monozygotic (MZ) twins number more girls than boys. The difference in perinatal mortality between DZ and MZ twins is limited to the monochorionic MZ subgroup. Birth weight is highest in DZ twins and diminishes stepwise in MZ dichorionic and MZ monochorionic twins. Duration of pregnancy follows the same trend but is limited to a few days. Iatrogenic pregnancies are increasing to the point of representing almost 50% of the twin births in 1997.

Amnion↗
PubMed1997

Gender-specific regional changes in genetic structure of muscularity in early adolescence.

Genetic and environmental influences on muscle circumference measurements of the extremities were estimated in 105 pairs of twins between 10 and 14 yr of age. Four circumferences, extended upper arm (EAC), forearm (FC), thigh (TC), and calf (CC), were measured. Univariate model fitting revealed that the largest part (87-95%) of the variance for all circumferences at most ages was explained by additive genetic factors. Sex differences were observed for some age categories. Multivariate analyses showed a different pattern evolving according to age and gender. In boys from 10 to 12 yr of age, one general genetic factor influenced all four circumferences. With increasing age, an arm-leg model emerged, one genetic factor influencing the arm and another genetic factor the leg circumferences. In young girls one genetic factor loaded on the proximal (EAC, TC) and another on the distal (FC, CC) circumferences. With subjects at age 14 yr, an arm-leg model was observed. High genetic correlations indicated that genetic factors related to EAC, FC, TC, and CC did not act independently. The age-and gender-specific changes in the genetic structure suggest pubertal influences. This study shows that muscle circumferences are highly heritable characteristics and are therefore a promising starting point at which to locate their genes. Gene mapping could validate the gender-specific change of the genetic structure with age and region.

Adolescent↗
PubMed1997

The genetic contribution to dental maturation.

It has been established in the literature that there is a major genetic impact on tooth size (Potter et al., 1976; Corruccini and Sharma, 1985; Sharma et al., 1985), tooth morphology (Kraus and Furr, 1952; Biggerstaff, 1970), and root formation (Garn et al., 1960; Green and Aszkler, 1970). None of the studies concerning root formation, however, used the more advanced method of path analysis and model fitting to estimate genetic influence. The aim of the present study was to determine the genetic and environmental influence on dental maturation. Dental age scores were determined on panoramic radiographs of 58 pairs of twins--26 monozygotic (MZ) and 32 dizygotic (DZ)--with the method of Demirjian et al. (1973). No mirror-image effect was found between the sides of the same individual or between twin members, so dental maturation seems to be symmetrical for both left and right sides of the mandible. Correlation coefficients were significantly higher in MZ than in DZ twins, which suggests a genetic influence. Model fitting showed that the variation in dental age was best explained by additive genetic influences (A-component) (43%) and by environmental factors common to both twins (C-component) (50%). The specific environment (E-component) added only 8% to the model. The importance of the common environmental factor can be explained by the fact that twins, being raised together, share the same prenatal, natal, and immediate post-natal conditions that are of importance for the formation of the teeth.

Adolescent↗
PubMed1996

Handedness in twins according to zygosity and chorion type: a preliminary report.

In the course of the East Flanders Prospective Twin Survey (EFPTS), handedness was assessed as part of a genealogical study (Meulemans et al., 1995) in 1616 twins (808 twin pairs) aged 6 to 28. Our findings are that, in this large population-based study with known placentation and zygosity, the often observed higher frequency of left-handedness in twins is confirmed, that it appears to be independent of zygosity and chorion type, and that the belief that discordant handedness in monozygotic twins represents mirror-imaging is mythical.

Adolescent↗
PubMed1996

Inheritance of physical fitness in 10-yr-old twins and their parents.

This study focuses on the quantification of genetic and environmental sources of variation in physical fitness components in 105 10-yr-old twin pairs and their parents. Nine motor tests and six skinfold measures were administered. Motor tests can be divided into those that are performance-related: static strength, explosive strength, running speed, speed of limb movement, and balance; and those that are health-related: trunk strength, functional strength, maximum oxygen uptake, and flexibility. The significance and contribution of genetic and environmental factors to variation in physical fitness were tested with model fitting. Performance-related fitness characteristics were moderately to highly heritable. The heritability estimates were slightly higher for health-related fitness characteristics. For most variables a simple model including genetic and specific environmental factors fitted the observed phenotypic variance well. Common environmental factors explained a significant part of the variation in speed components and flexibility. Assortative mating was significant and positive for speed components, balance, trunk strength, and cardiorespiratory fitness, but negative for adiposity. Static strength, explosive strength, functional strength, and cardiorespiratory fitness showed evidence for reduced genetic transmission or dominance. The hypothesis that performance-related fitness characteristics are more determined by genetic factors than health-related fitness was not supported. At this prepubertal age, genetic factors have the predominant effect on fitness.

Adult↗
PubMed1995

Heritability of conventional and ambulatory blood pressures. A study in twins.

Conventional and 24-hour ambulatory blood pressures were measured in 26 pairs of monozygotic twins and 27 pairs of dizygotic twins, all male, ages 18 to 38 years, to determine the heritability of blood pressure measured under various conditions. Conventional pressure was the average of three well-standardized measurements in the supine position, and ambulatory pressure was recorded during the subjects' normal activities by use of the SpaceLabs 90202 device. Heritability was assessed by classic methods and by model fitting and path analysis. In the latter approach, the percent genetic variance was 70% for mean 24-hour systolic pressure and 73% for diastolic pressure, which was similar to the results for the conventional pressures (64% and 73%, respectively). During the night, these estimates were 72% and 51% for systolic and diastolic pressures, respectively, and also the average pressures of the total awake daytime period were under partial genetic control (63% and 55%, respectively). The remaining variances could be attributed primarily to unique environmental influences. However, shared and nonshared environmental factors were predominant for the pressures during a fixed 6-hour afternoon period. We conclude that the heritability of blood pressure is relatively high in young adult healthy men, for standardized conventional pressure and the average 24-hour pressure. Genetic variance is somewhat higher for the asleep pressure than for the awake systolic pressure.

Adolescent↗
PubMed1994

X chromosome inactivation patterns correlate with fetal-placental anatomy in monozygotic twin pairs: implications for immune relatedness and concordance for autoimmunity.

BACKGROUND: Monozygotic (MZ) twinning is a poorly understood phenomenon that may result in subtle biologic differences between twins, despite their identical inheritance. These differences may in part account for discordant expression of disease in MZ twin pairs. Due to their stochastic nature, differences in X chromosome inactivation patterns are one source of such variation in female MZ twins. MATERIALS AND METHODS: We investigated X chromosome inactivation patterns in the blood of 41 MZ twin pairs based on methylation of the androgen receptor gene using a Hpa II-PCR assay. Twenty-six female MZ twin pairs with autoimmune disease (rheumatoid arthritis or multiple sclerosis) were studied. In addition, we studied 15 newborn female MZ twin pairs who were characterized at birth with respect to the anatomy of chorionic membranes (dichorionic versus monochorionic). RESULTS: We found a strong correlation between dichorionic fetal anatomy and differences in X chromosome inactivation patterns between members of an MZ twin pair. In contrast, all monochorionic twin pairs had closely correlated patterns of X chromosome inactivation. X chromosome inactivation patterns did not distinguish between MZ twin pairs who were concordant or discordant for autoimmune disease. CONCLUSIONS: The highly similar patterns of X chromosome inactivation among monochorionic twin pairs may result from their shared placental blood supply during intrauterine life. Alternatively, these patterns may indicate that X chromosome inactivation occurs before the twinning event in this anatomic subgroup of MZ twins. The data further suggest that these factors do not make a major contribution to the high discordance rates for autoimmune disease in MZ twin pairs.

Autoimmune Diseases↗
PubMed1993

Iatrogenic multiple pregnancies in East Flanders, Belgium.

OBJECTIVE: To evaluate the specific contribution of artificial induction of ovulation to the increasing number of multiple gestations in East Flanders and the effects of this treatment on the frequencies of monozygotic and dizygotic twinning. DESIGN: Since 1976 the East Flanders Prospective Twin Study has collected data on artificial induction of ovulation for all the multiple births listed in its registry. SETTING: East Flanders Prospective Twin Survey. PATIENTS: Between 1976 and 1992, 458 twin and 78 triplet pregnancies resulting from artificial induction of ovulation were analyzed. MAIN OUTCOME MEASURES: Zygosity and frequency of iatrogenic multiple births. RESULTS: Since 1985 there is an explosive increase in twin and triplet births in East Flanders. This increase has been caused mainly by the sole use of fertility-enhancing drugs and in the last few years by resorting to other technologies of assisted reproduction, such as IVF-ET, GIFT, or zygote intrafallopian transfer. CONCLUSION: In view of the elevated risk inherent to multiple pregnancies in terms of perinatal mortality and morbidity, the over enthusiastic or improper use of fertility drugs should be curtailed.

Belgium↗
PubMed1991

Genotyping of macerated stillborn fetuses.

It is generally impossible to collect blood or to culture tissue from a macerated stillborn fetus. Accurate genotyping of such a fetus may, however, be critical for the diagnosis of genetic diseases and appropriate genetic counseling. In the East Flanders Prospective Twin Study, placental tissue of twin and triplet sets, in some of which one or both members were stillborn and macerated, has been stored at -20 degrees C. Of all these fetuses, sex and zygosity could be determined accurately on the placental deoxyribonucleic acid. We tested the possibility of nongenetic changes in deoxyribonucleic acid that result from maceration or tissue degradation over time in storage on placental samples from monochorionic twins in which only one member was stillborn and macerated. The deoxyribonucleic acid variants in these monozygotic twins were identical whether or not either cotwin was macerated. Thus deoxyribonucleic acid variants can be determined accurately on the placental tissue of macerated fetuses, even after prolonged freezing.

DNA↗