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Scandinavian Journal of Medicine &... Sep 2022Genetic and early environmental differences including early health habits associate with future health. To provide insight on the causal nature of these associations,... (Review)
Review
Genetic and early environmental differences including early health habits associate with future health. To provide insight on the causal nature of these associations, monozygotic (MZ) twin pairs discordant for health habits provide an interesting natural experiment. Twin pairs discordant for leisure-time physical activity (LTPA) in early adult life is thus a powerful study design to investigate the associations between long-term LTPA and indicators of health and wellbeing. We have identified 17 LTPA discordant twin pairs from two Finnish twin cohorts and summarize key findings of these studies in this paper. The carefully characterized rare long-term LTPA discordant MZ twin pairs have participated in multi-dimensional clinical examinations. Key findings highlight that compared with less active twins in such MZ twin pairs, the twins with higher long-term LTPA have higher physical fitness, reduced body fat, reduced visceral fat, reduced liver fat, increased lumen diameters of conduit arteries to the lower limbs, increased bone mineral density in loaded bone areas, and an increased number of large high-density lipoprotein particles. The findings increase our understanding on the possible site-specific and system-level effects of long-term LTPA.
Topics: Adult; Exercise; Finland; Humans; Motor Activity; Physical Fitness; Twins, Monozygotic
PubMed: 35770444
DOI: 10.1111/sms.14205 -
Genome Biology Dec 2023Recent state-of-the-art sequencing technologies enable the investigation of challenging regions in the human genome and expand the scope of variant benchmarking...
BACKGROUND
Recent state-of-the-art sequencing technologies enable the investigation of challenging regions in the human genome and expand the scope of variant benchmarking datasets. Herein, we sequence a Chinese Quartet, comprising two monozygotic twin daughters and their biological parents, using four short and long sequencing platforms (Illumina, BGI, PacBio, and Oxford Nanopore Technology).
RESULTS
The long reads from the monozygotic twin daughters are phased into paternal and maternal haplotypes using the parent-child genetic map and for each haplotype. We also use long reads to generate haplotype-resolved whole-genome assemblies with completeness and continuity exceeding that of GRCh38. Using this Quartet, we comprehensively catalogue the human variant landscape, generating a dataset of 3,962,453 SNVs, 886,648 indels (< 50 bp), 9726 large deletions (≥ 50 bp), 15,600 large insertions (≥ 50 bp), 40 inversions, 31 complex structural variants, and 68 de novo mutations which are shared between the monozygotic twin daughters. Variants underrepresented in previous benchmarks owing to their complexity-including those located at long repeat regions, complex structural variants, and de novo mutations-are systematically examined in this study.
CONCLUSIONS
In summary, this study provides high-quality haplotype-resolved assemblies and a comprehensive set of benchmarking resources for two Chinese monozygotic twin samples which, relative to existing benchmarks, offers expanded genomic coverage and insight into complex variant categories.
Topics: Humans; Benchmarking; East Asian People; Genomics; Haplotypes; High-Throughput Nucleotide Sequencing; Sequence Analysis, DNA; Twins, Monozygotic; Twin Studies as Topic
PubMed: 38049885
DOI: 10.1186/s13059-023-03116-3 -
Journal of Attention Disorders Nov 2023We examined the characteristics and heritability of Autism Spectrum Disorder (ASD) and ADHD through a twin study.
OBJECTIVE
We examined the characteristics and heritability of Autism Spectrum Disorder (ASD) and ADHD through a twin study.
METHOD
Our sample included 44 twins, with at least one twin diagnosed with ASD. Among the participants, 30 had ASD, and 18 of them also had coexisting ADHD.
RESULTS
We observed higher concordance rates for ASD in monozygotic twins compared to dizygotic twins (67% vs. 25%), indicating a genetic influence on ASD. Inattentive symptoms of ADHD were more prevalent in monozygotic twins. The ASD + ADHD group exhibited significantly higher Social Responsiveness Scale scores, indicating greater social difficulties compared to the ASD and typical development groups. Twin analyses revealed that shared genetic factors accounted for 72.25% of the variance in both ASD and ADHD symptoms.
CONCLUSIONS
Our findings suggest that the comorbidity of ASD and ADHD may indicate increased severity and can be explained by shared genetic factors underlying both conditions.
Topics: Humans; Child; Autism Spectrum Disorder; Attention Deficit Disorder with Hyperactivity; Twins, Monozygotic; Twins, Dizygotic; Comorbidity
PubMed: 37480257
DOI: 10.1177/10870547231187166 -
Fertility and Sterility Oct 2015To estimate the relative contribution of genetic influences and prevalence on endometriosis.
OBJECTIVE
To estimate the relative contribution of genetic influences and prevalence on endometriosis.
DESIGN
Analysis of self-reported data from a nationwide population-based twin registry.
SETTING
Not applicable.
PATIENT(S)
A total of 28,370 women, female monozygotic (MZ) or dizygotic (DZ) twins, who participated in either of two surveys (1998-2002 or 2005-2006).
INTERVENTION(S)
None.
MAIN OUTCOME MEASURE(S)
Self-reported endometriosis, validated by medical records.
RESULT(S)
A history of endometriosis was reported by 1,228 female twins. The probandwise concordance was 0.21 for MZ and 0.10 for DZ twins. Higher within-pair (tetrachoric) correlation was observed among MZ (0.47) compared with DZ (0.20) twins. The best-fitting model revealed a contribution of 47% by additive genetic factors and the remaining 53% attributed to unique environmental effects.
CONCLUSION(S)
Our findings suggest both genetic and unique (nonshared) environmental influences on the complex etiology of endometriosis and support the hypothesis that genes have a strong influence on phenotypic manifestations of endometriosis.
Topics: Adult; Aged; Cross-Sectional Studies; Diseases in Twins; Endometriosis; Female; Genetic Predisposition to Disease; Humans; Middle Aged; Models, Genetic; Quantitative Trait, Heritable; Twins, Dizygotic; Twins, Monozygotic; Young Adult
PubMed: 26209831
DOI: 10.1016/j.fertnstert.2015.06.035 -
Genes Feb 2019Studies with twins provide fundamental insights to lifespans of humans. We aim to clarify if monozygotic and dizygotic twin individuals differ in lifespan, that is, if...
Studies with twins provide fundamental insights to lifespans of humans. We aim to clarify if monozygotic and dizygotic twin individuals differ in lifespan, that is, if zygosity matters. We investigate whether a possible difference in mortality after infancy between zygosities is stable in different age cohorts, and whether the difference remains when twins with unknown zygosity are taken into account. Further, we compare the distribution of long-livers, that is, the upper-tail of the lifespan distribution, between monozygotic and same-sex dizygotic twin individuals. The Danish Twin Registry provides a nationwide cohort of 109,303 twins born during 1870 to 1990 with valid vital status. Standard survival analysis is used to compare mortality in monozygotic and dizygotic twin individuals and twin individuals with unknown zygosity. The mortality of monozygotic and dizygotic twin individuals differs slightly after taking into consideration effects of birth- and age-cohorts, gender differences, and that twins are paired. However, no substantial nor systematic differences remain when taking twins with unknown zygosity into account. Further, the distribution of long-livers is very similar by zygosity, suggesting the same mortality process. The population-based and oldest twin cohort ever studied suggests that monozygotic and dizygotic twins have similar lifespans.
Topics: Adult; Aged; Denmark; Female; Humans; Longevity; Male; Middle Aged; Mortality; Registries; Twins, Dizygotic; Twins, Monozygotic
PubMed: 30791679
DOI: 10.3390/genes10020166 -
Monographs in Oral Science 2021The study of twins is a powerful tool to infer the presence and amount of contribution of genetic variation to a particular trait or disease. The ability to compare... (Review)
Review
The study of twins is a powerful tool to infer the presence and amount of contribution of genetic variation to a particular trait or disease. The ability to compare identical or monozygotic twins with dizygotic twins permits the direct comparison of pairs of individuals that share 100% of their genomic DNA with pairs that share only 50%, with the assumption that these pairs are under the same environment. In the case of dental caries, the environment is same parents, under the same roof, with the same diet, oral hygiene habits, culture, and lifestyle. These data have consistently suggested that a relevant proportion of the variation of dental caries in populations is due to genetics.
Topics: Dental Caries; Diseases in Twins; Humans; Oral Hygiene; Twin Studies as Topic; Twins, Dizygotic; Twins, Monozygotic
PubMed: 35078175
DOI: 10.1159/000520768 -
Journal of Assisted Reproduction and... Apr 2023To determine the recurrence risk and risk factors for monozygotic splitting after elective single-embryo transfers (eSET).
PURPOSE
To determine the recurrence risk and risk factors for monozygotic splitting after elective single-embryo transfers (eSET).
METHODS
A retrospective cohort study was performed investigating 65,664 eSET cycles that resulted in a clinical pregnancy as reported in the Society for Assisted Reproductive Technology (SART) Clinical Outcomes Reporting System (CORS) between 2004 and 2017. Monozygosity was defined as more than one fetal heart tone by the first-trimester ultrasound and concordant sex at live birth. The primary outcome was recurrence risk, with recurrence defined as one patient having two or more cycles of eSET resulting in monozygotic multiples. The secondary objective was to identify factors associated with smonozygotic splitting, using a multivariable logistic regression model and a stepwise purposeful model selection.
RESULTS
There were 1355 (2.05%) pregnancies that resulted in two or more fetal heart tones after SET, including 840 monozygotic twins and triplets at birth. Recurrence occurred in two cases-0.0001% of patients with multiple eSET cycles. One case resulted from embryos created from a single cohort with intracytoplasmic sperm injection (ICSI), assisted hatching (AH), and blastocyst transfers. The second case resulted from donor egg embryos with ICSI and blastocyst transfers. Risk factors associated with monozygotic live birth were blastocyst transfer (OR 1.23, 95% CI 1.04-1.47, P = 0.0176) and AH (OR 1.23, 95% CI 1.05-1.44, P = 0.0081).
CONCLUSION
Recurrence of monozygotic live births in eSET was very rare. Blastocyst transfer and AH were confirmed to be risk factors for monozygotic live births, while ICSI, PGT, and FET do not appear to be associated.
Topics: Infant, Newborn; Female; Pregnancy; Humans; Male; Twins, Monozygotic; Retrospective Studies; Fertilization in Vitro; Semen; Embryo Transfer; Risk Factors
PubMed: 36746891
DOI: 10.1007/s10815-023-02737-8 -
Methods (San Diego, Calif.) Jun 2016As a final function of various epigenetic mechanisms, chromatin regulation is a transcription control process that especially demonstrates active interaction with... (Review)
Review
As a final function of various epigenetic mechanisms, chromatin regulation is a transcription control process that especially demonstrates active interaction with genetic elements. Thus, chromatin structure has become a principal focus in recent genomics researches that strive to characterize regulatory functions of DNA variants related to diseases or other traits. Although researchers have been focusing on DNA methylation when studying monozygotic (MZ) twins, a great model in epigenetics research, interactions between genetics and epigenetics in chromatin level are expected to be an imperative research trend in the future. In this review, we discuss how the genome, epigenome, and transcriptome of MZ twins can be studied in an integrative manner from this perspective.
Topics: Epigenesis, Genetic; Epigenomics; Genome, Human; Humans; Phenotype; Transcriptome; Twins, Monozygotic
PubMed: 26548893
DOI: 10.1016/j.ymeth.2015.10.020 -
The Journal of Clinical Pediatric... Mar 2022The aim of this study is to investigate the relative contributions of genetic and environmental factors to variations in dental dimensions in a sample of Turkish twins,...
BACKGROUND
The aim of this study is to investigate the relative contributions of genetic and environmental factors to variations in dental dimensions in a sample of Turkish twins, and to estimate heritability using dental casts.
STUDY DESIGN
The study samples were selected from the twin children between 3-15 years old who referred for their first dental examination. Fifty nine monozygotic and one hundred and forty three dizygotic twin pairs were examined in the study. The alginate impression material used to create the plaster model of maxilla and mandible. Anterior arch width, posterior arch width, arch length and arch circumference were measured on models prepared from measurements taken for both maxilla and mandible with digital caliper. The similarities and differences of the measurements were compared between pairs of twins and zygocytes. Morever, the effects of bad oral habits, bruxism, a result of psychosocial factors on measurements were examined. Statistical analysis was performed using Paired T Test, Wilcoxon Test and Mann Whitney U test.
RESULTS
A total of 404 dental models of 118 (29.2%) monozygotic and 286 (70.8%) dizygotic twins were evaluated. There was no statistical difference between sibling pairs in both monozygotic and dizygotic twins. The measurement similarity between twin siblings differed according to zygosity in all measurements (p<0.05). It has been observed that the finger sucking and mouth breathing affect the dental arch measurements (p<0.05).
CONCLUSION
These results indicate that the differences in dental arch dimensions between monozygotic twin pairs are less than the difference between dizygotic twin pairs.
Topics: Adolescent; Child; Child, Preschool; Dental Arch; Humans; Mandible; Maxilla; Twins, Dizygotic; Twins, Monozygotic
PubMed: 35533222
DOI: 10.17796/1053-4625-46.2.12 -
Sleep Health Oct 2021The causal nature of the sleep-obesity association is unclear. To control for potential confounding by genes and shared environment, we studied monozygotic twin pairs...
OBJECTIVES
The causal nature of the sleep-obesity association is unclear. To control for potential confounding by genes and shared environment, we studied monozygotic twin pairs discordant for body mass index (BMI). First, we investigated sleep in relation to BMI. Second, we examined associations of objective and subjective sleep duration and sleep debt (objective or subjective sleep duration minus subjective sleep need) with eating behaviors and physical activity (PA).
DESIGN
Cross-sectional study.
SETTING
Finnish twins in everyday life circumstances.
PARTICIPANTS
Seventy-four healthy young adult monozygotic twin pairs, of whom 36 were BMI-discordant (∆BMI ≥ 3 kg/m).
MEASUREMENTS
Clinical measurements estimated BMI and body composition. Sleep, eating, and PA behaviors were measured by self-report and actigraphy.
RESULTS
Compared to co-twins with lower BMI, co-twins with higher BMI reported shorter sleep (P = .043), more snoring (P = .0093), and greater tiredness (P = .0013) and trended toward eveningness (P = .036). Actigraphy-measured sleep duration correlated highly within BMI-discordant twin pairs (r = 0.63, P = .004). Subjective sleep debt was consistently positively associated with disinhibited eating and binge eating, but not with BMI. Subjective and objective sleep debt had negative correlations with moderate-to-vigorous PA.
CONCLUSIONS
Twins with higher BMI showed less favorable sleep characteristics than their co-twins with lower BMI. Subjective sleep debt is a potential target for intervention to reduce eating and PA behaviors that promote weight gain. Experimental studies could elucidate mechanisms underlying tiredness in individuals with higher BMI and investigate causal relationships between sleep debt, BMI, and lifestyle.
Topics: Body Mass Index; Cross-Sectional Studies; Humans; Life Style; Sleep; Twins, Monozygotic; Young Adult
PubMed: 34193396
DOI: 10.1016/j.sleh.2021.04.002