-
Twin Research and Human Genetics : the... Feb 2022Heritability of age at menarche (AAM) in African populations remains largely unknown. A question on AAM was given to 1803 [454 monozygotic (MZ), 823 same-sex dizygotic...
Heritability of age at menarche (AAM) in African populations remains largely unknown. A question on AAM was given to 1803 [454 monozygotic (MZ), 823 same-sex dizygotic (DZ), and 526 female members of opposite sex] adolescent twins attending public schools in Lagos State, Nigeria. The age range of the sample was 12-18 years, with a mean (SD) of 14.57 (±1.70) years. The data included 905 missing cases consisting of those who had not experienced menarche and did not recall AAM. Missing values were imputed using the Expectation-Maximization algorithm. Kaplan-Meier analysis based on the imputed data yielded 13.23 years [95% CI [13.18, 13.28] for the mean and 13.00 years [95% CI [12.96, 13.04] for the median of AAM. Twin correlation and model-fitting analyses were performed on the basis of those who reported AAM (MZ = 82 complete pairs and 38 cotwin missing cases; DZ = 157 complete pairs and 99 cotwin missing cases). Maximum likelihood MZ and DZ twin correlations for AAM were .63 (95% CI [.48, .74]) and .33 (95% CI [.19, .45]) respectively. Model-fitting analyses indicated that 58% (95% CI [46, 67]) of the variance of AAM was associated with additive genetic influences with the remaining variance, 42% (33-54) being due to nonshared environmental influences including measurement error. The heritability estimate found in this study was within the range of those found in Asian and Western twin samples.
Topics: Adolescent; Asian People; Child; Female; Humans; Menarche; Nigeria; Twins, Dizygotic; Twins, Monozygotic
PubMed: 35535435
DOI: 10.1017/thg.2022.9 -
Twin Research and Human Genetics : the... Dec 2021Although twins often participate in medical research, few clinical trials are conducted entirely in twin populations. The purpose of this review is to demonstrate the... (Review)
Review
Although twins often participate in medical research, few clinical trials are conducted entirely in twin populations. The purpose of this review is to demonstrate the substantial benefits and address the key challenges of conducting clinical trials in twin populations, or 'twin-only trials'. We consider the unique design, analysis, recruitment and ethical issues that arise in such trials. In particular, we describe the different approaches available for randomizing twin pairs, highlight the similarity or correlation that exists between outcomes of twins, and discuss the impact of this correlation on sample size calculations and statistical analysis methods for estimating treatment effects. We also consider the role of both monozygotic and dizygotic twins for studying variation in outcomes, the factors that may affect recruitment of twins, and the ethics of conducting trials entirely in twin populations. The advantages and disadvantages of conducting twin-only trials are also discussed. Finally, we recommend that twin-only trials should be considered more often.
Topics: Diseases in Twins; Humans; Twins, Dizygotic; Twins, Monozygotic
PubMed: 35074024
DOI: 10.1017/thg.2021.52 -
Twin Research and Human Genetics : the... Aug 2021Every reared-apart monozygotic (MZ) twin pair offers a fresh perspective on human developmental questions. This is true regardless of whether the co-twins were raised in... (Review)
Review
Twins Separated at Birth: Across a Country and Around the World/Twin Research: Memorial Tribute to Isaac Blickstein, MD; Infanticide and Sacrifice of Archaic-Aged Twins and Triplets; Prehistoric Twin Burials; Highlights from a Conference on /Media Reports: An Atypical Twin Father; An Actor's Twin...
Every reared-apart monozygotic (MZ) twin pair offers a fresh perspective on human developmental questions. This is true regardless of whether the co-twins were raised in the same country or across the globe. The members of two pairs of separated MZ female twins have recently come to attention. In one case the twins were raised by different families in Argentina; in the other case the twins were raised by different families in Sweden and Vietnam. The perceptions and perspectives of these twins are insightful. The twin research section that follows begins with a tribute to our late esteemed colleague, Dr Isaac Blickstein (1953-2020). Research concerning the infanticide and sacrifice of Archaic-aged twins and triplets and prehistoric twin burials is reviewed next. Highlights from a conference focused on the 2018 film Three Identical Strangers are also included in this portion. The final section of this article includes media reports of an atypical twin father, an actor's twin brother, a twin link to the 1921 Tulsa, Oklahoma massacre, the birth of superfetated twins, twin comedians and script writers and Indian twins' tragic loss to COVID-19.
Topics: Aged; Burial; COVID-19; Fathers; Female; Humans; Infant, Newborn; Infanticide; Male; Oklahoma; SARS-CoV-2; Siblings; Twins, Dizygotic; Twins, Monozygotic
PubMed: 34429182
DOI: 10.1017/thg.2021.30 -
Twin Research and Human Genetics : the... Aug 2020The aim of the study was to examine the Family and School Psychosocial Environment (FSPE) questionnaire in relation to a possible genotype-environment correlation and...
The aim of the study was to examine the Family and School Psychosocial Environment (FSPE) questionnaire in relation to a possible genotype-environment correlation and genetic mediation between the FSPE variables and personality variables, assessed by the Junior Eysenck Personality Questionnaire. A sample of 506 Swedish children aged 10-20 years from 253 families were recruited via the Swedish state population and address register and SchoolList.Eu. The children were divided into 253 pairs: 46 monozygotic twin pairs, 42 dizygotic twin pairs, 140 pairs of full siblings and 25 pairs of half-siblings. The behavioral genetic analysis showed that both FSPE factors, Warmth and Conflicts, may be partly influenced by genetic factors (suggesting genotype-environment correlation) and that nonadditive genetic factors may mediate the relationship between FSPE factors and psychoticism/antisocial personality (P). An indication of a special shared monozygotic twin environment was found for P and Lie/social desirability, but based on prior research findings this factor may have a minor influence on P and L. P and L were negatively correlated, and the relationship seems to be partly mediated by nonadditive genetic factors. Nonshared environment and measurement errors seem to be the most influential mediating factors, but none of the cross-twin cross-dimension correlations suggest a common shared environmental mediating factor.
Topics: Adolescent; Child; Gene-Environment Interaction; Genotype; Humans; Personality; Sweden; Twins, Dizygotic; Twins, Monozygotic; Young Adult
PubMed: 32772950
DOI: 10.1017/thg.2020.63 -
Journal of Affective Disorders Jun 2022Educational achievement is an independent predictor of many life outcomes and so it is important to understand its causes and correlates. Internalising symptoms,...
BACKGROUND
Educational achievement is an independent predictor of many life outcomes and so it is important to understand its causes and correlates. Internalising symptoms, encompassing anxiety and depression symptoms, are one candidate influence.
METHODS
Using a prospective and genetically-informative design, the present study investigated the associations between internalising symptoms and educational achievement, controlling for IQ at age 7 years and socioeconomic status, among participants of the Twin and Early Development Study (up to N = 10,791). Internalising symptoms were measured by the parent-rated Anxiety Related Behaviours Questionnaire (ages 7, 9, 16 years), and educational attainment were indexed by UK-wide standardized examination results at ages 16 and 18 years, and self-reported transition to university education.
RESULTS
Negative affect was the only internalising symptom subtype that was uniquely associated with academic underachievement at all timepoints, from mid-adolescence to early adulthood. The association between negative affect and achievement became non-significant when using MZ twin difference scores, suggesting that the majority of the relationship is accounted for by genetic and shared environmental effects.
LIMITATIONS
Limitations include the reliance on parent-reported internalising symptoms.
CONCLUSIONS
Negative affect in youth may be an important marker of later academic underachievement. Findings suggest that academic underachievement is not simply a consequence of the disruption caused by negative affect symptoms and therefore educational interventions may be required to optimise outcomes.
Topics: Academic Success; Achievement; Adolescent; Adult; Anxiety Disorders; Child; Educational Status; Humans; Twins, Monozygotic
PubMed: 35390354
DOI: 10.1016/j.jad.2022.03.073 -
Twin Research and Human Genetics : the... Apr 2022It is widely recognized that dizygotic twinning (DZT) runs in families, but estimates of heritability from twin and family data are remarkably scarce and vary...
It is widely recognized that dizygotic twinning (DZT) runs in families, but estimates of heritability from twin and family data are remarkably scarce and vary considerably. Here, we traced seven large, sometimes historical, multigeneration pedigrees from West Africans, fin de siècle French Jews, Canadians (two pedigrees), and the French royal family, in which twin births were recorded. We estimated heritability of twinning (of all types) as zygosity information was not available, diluting the true DZT heritability by a third or so. The estimates in the range 8-20% are remarkably consistent across time (8-19 generations) and ethnicities and also consistent with twin and family estimates.
Topics: Canada; Humans; Pedigree; Twins, Dizygotic; Twins, Monozygotic
PubMed: 35593089
DOI: 10.1017/thg.2022.14 -
Reproductive Sciences (Thousand Oaks,... May 2021In vitro fertilization (IVF) is associated with a higher incidence of monozygotic twin pregnancies, which are known to be burdened by a higher risk of main obstetric...
In vitro fertilization (IVF) is associated with a higher incidence of monozygotic twin pregnancies, which are known to be burdened by a higher risk of main obstetric complications. The reasons behind this association are still unclear. In the present study, we therefore investigate the risk factors for monozygotic twinning in pregnancies achieved by IVF. We conducted a multicenter retrospective case-control study. All IVF cycles performed between 2014 and 2019 at the infertility units of two Italian academic institutes were retrospectively reviewed. Only pregnancies obtained with single embryo transfer were eligible. A total of 50 monozygotic twin pregnancies (cases) were identified and matched in a 1:5 ratio to 250 singleton pregnancies (controls) by study center and study period. Monozygotic twin pregnancies were diagnosed by ultrasound. Women experiencing miscarriage could be included provided that the pregnancy loss occurred after a definitive diagnosis of monozygotic twin pregnancy. Demographic, clinical, and embryological characteristics were retrieved from patients' charts. Overall, the incidence of monozygotic twin pregnancies was 1.2% (50 out of 4016 single embryo transfers). At univariate analyses, statistically significant differences emerged for BMI, peripheral levels of estradiol and progesterone at the time of hCG administration, total number of retrieved suitable oocytes, freezing-thawing cycles, and assisted hatching. After performing a multivariate logistic analysis, only assisted hatching remained significantly associated with monozygotic twinning (adjusted odds ratio 2.32, 95%CI 1.03-5.25). Blastomere separation during the passage through this artificial hole or interference with the signaling pathway within the embryo could be the mechanisms involved.
Topics: Adult; Case-Control Studies; Estrogens; Female; Fertilization in Vitro; Humans; Oocytes; Progesterone; Retrospective Studies; Risk Factors; Twinning, Monozygotic; Twins, Monozygotic
PubMed: 33258063
DOI: 10.1007/s43032-020-00406-0 -
Nutrients Sep 2022The present study aimed to investigate the coincidence of obesity and nutritional intake in monozygotic twins compared to dizygotic twins. The data from the Korean...
The present study aimed to investigate the coincidence of obesity and nutritional intake in monozygotic twins compared to dizygotic twins. The data from the Korean Genome and Epidemiology Study (KoGES) from 2005 through 2014 were analyzed. Participants ≥ 20 years old were enrolled. The 1006 monozygotic twins and 238 dizygotic twins were analyzed for differences in self-reported nutritional intake, total body fat, and body mass index (BMI) using a linear regression model. The estimated values (EV) with 95% confidence intervals (95% CI) of the difference in dietary intake, total body fat, and BMI score were calculated. The monozygotic twin group and the dizygotic twin group showed similar differences in nutritional intake, DEXA fat, and BMI (all p > 0.05). The differences in nutritional intake of total calories and carbohydrates were lower in the monozygotic twin group than in the dizygotic twin group (all p < 0.05). The differences in total body fat were lower in monozygotic twins than in dizygotic twins (adjusted EV = 2427.86 g, 95% CI = 1777.19−3078.53 and adjusted EV = 1.90%, 95% CI = 1.33−2.46). Monozygotic twins had more similar dietary habits for total calories and carbohydrate intake. Other nutritional factors did not show differential similarity between monozygotic and dizygotic twins. Total body fat was more concordant in monozygotic twins.
Topics: Adipose Tissue; Adult; Body Mass Index; Eating; Humans; Twins, Dizygotic; Twins, Monozygotic; Young Adult
PubMed: 36079910
DOI: 10.3390/nu14173655 -
Journal of Autoimmunity Sep 2017Monozygotic twins share an identical DNA sequence but are not truly "identical". In fact, when it comes to health and disease, they may often display some level of... (Review)
Review
Monozygotic twins share an identical DNA sequence but are not truly "identical". In fact, when it comes to health and disease, they may often display some level of phenotypic discordance. The cause of this discordance is often unknown. Epigenetic modifications such as DNA methylation, histone modification, and microRNAs-mediated regulation regulate gene expression and are sensitive to external stimuli. These modifications may be seen to bridge the gap between genetics and the environment. Over the years, the importance of epigenetics as a primary mechanism for the role that the environment plays in defining phenotype has been increasingly appreciated. Mechanisms of epigenetics include DNA methylation, histone modifications and microRNAs. Discordance rates in monozygotic twins vary depending on the specific condition, from 11% in SLE to 64% in psoriasis and 77% in PBC. Other autoimmune diseases in which discordance is found among monozygotic twins has also been studied include type 1 diabetes, multiple sclerosis, rheumatoid arthritis, dermatomyositis and systemic sclerosis. In some cases, the differences in various epigenetic modifications is slight, even though the concordance rate is low, suggesting that epigenetics is not the only factor that needs to be considered. Nonetheless, the study of phenotypic discordance in monozygotic twins may shed light on the pathogenesis of autoimmune diseases and contribute to the development of new methodologies for the diagnosis and treatment of these diseases.
Topics: Autoimmune Diseases; Autoimmunity; DNA Methylation; Epigenesis, Genetic; Gene-Environment Interaction; Genotype; Histones; Humans; MicroRNAs; Phenotype; Twins, Monozygotic
PubMed: 28412046
DOI: 10.1016/j.jaut.2017.04.003 -
Twin Research and Human Genetics : the... Apr 2021Research into the origins of twinning has focused mostly on contributions from the female side of the family. A review of current findings suggests that possible male... (Review)
Review
Do Males Affect Twinning Events? A Review of Current Findings/Twin Research Reviews: Monozygotic Twins Discordant for Parkinson's Disease; Fetal Loss in Twin Pregnancies Following Prenatal Diagnosis; Uterine Rupture and Repair in an Early Twin Pregnancy; Twin Study of Affectionate...
Research into the origins of twinning has focused mostly on contributions from the female side of the family. A review of current findings suggests that possible male contributions to twinning events have been overlooked. This section is followed by brief reviews of twin research concerning monozygotic twins discordant for Parkinson's disease, fetal loss in twin pregnancies following prenatal diagnosis, uterine rupture and repair in an early twin pregnancy and a twin study of affectionate communication. The concluding portion of this article presents human interest stories involving twins that are both informative and poignant, namely conjoined twins in a triplet set, identical twin nurses who delivered identical twins, identical twins discordant for COVID-19 recovery course, identical twins who passed away from COVID-19 and archeological finds of the oldest identical twins.
Topics: COVID-19; Communication; Female; Fetal Death; Humans; Male; Nurses; Parkinson Disease; Pregnancy; Pregnancy, Twin; Prenatal Diagnosis; Twin Studies as Topic; Twins, Conjoined; Twins, Monozygotic; Uterine Rupture
PubMed: 33736741
DOI: 10.1017/thg.2021.8