-
Pediatric Research Sep 2021Several factors contribute to neurodevelopmental outcomes in preterm infants. The aim of this study was to examine the genetic and environmental influences on long-term...
BACKGROUND
Several factors contribute to neurodevelopmental outcomes in preterm infants. The aim of this study was to examine the genetic and environmental influences on long-term outcomes in preterm twins.
METHODS
From a prospective cohort of 225 preterm neonates studied with MRI, 24 monozygotic and 52 dizygotic twins were included. Neurodevelopmental outcomes at 1.5 and 3 years were assessed with the Bayley-III and at 4.5 years with The Movement Assessment Battery for Children and The Wechsler Preschool and Primary Scale of Intelligence-III.
RESULTS
Preterm monozygotic and dizygotic twin pairs (N = 76 neonates) had similar neurodevelopmental outcomes at all time points. Monozygotic twins (N = 24) did not show greater agreement for outcomes relative to dizygotic twins (N = 52). Twin pairs who were discordant in development (N = 12) were born at a lower gestational age and had a higher incidence of bronchopulmonary dysplasia and retinopathy of prematurity. Discordant twins become more similar in cognitive and language outcomes over time.
CONCLUSIONS
Neurodevelopmental outcomes in preterm twins may relate more strongly to environmental factors than genetics. Discordant twins were born earlier and had more perinatal morbidities. Despite the initial discordance, these twin pairs become similar in outcomes over time, which may reflect the positive impact of home environment or early intervention programs.
IMPACT
Neurodevelopmental outcomes in preterm twins relate more strongly to environmental factors than genetics. Monozygotic twins did not show greater agreement in outcomes relative to dizygotic twins suggesting a stronger environmental, rather than genetic, influence on development. Twin pairs who were discordant in development were born at a lower gestational age and had a higher incidence of perinatal morbidities. Despite the initial discordance, these twin pairs become more similar in cognitive and language outcomes over time, which may reflect the positive impact of early intervention programs or home environment. Neurodevelopmental outcomes in preterm twins are influenced by exposure to early-life insults or environmental stressors. The initial variability in outcomes among preterm infants is not fixed, and efforts made post-discharge from the neonatal intensive care unit can have a substantial impact on long-term outcomes.
Topics: Central Nervous System; Child, Preschool; Female; Humans; Infant, Newborn; Infant, Premature; Longitudinal Studies; Magnetic Resonance Imaging; Male; Neurodevelopmental Disorders; Prospective Studies; Twins; Twins, Dizygotic; Twins, Monozygotic
PubMed: 32172281
DOI: 10.1038/s41390-020-0840-7 -
Human Reproduction (Oxford, England) Jan 2024Spontaneous dizygotic (DZ) twins, i.e. twins conceived without the use of ARTs, run in families and their prevalence varies widely around the globe. In contrast,... (Meta-Analysis)
Meta-Analysis
Spontaneous dizygotic (DZ) twins, i.e. twins conceived without the use of ARTs, run in families and their prevalence varies widely around the globe. In contrast, monozygotic (MZ) twins occur at a constant rate across time and geographical regions and, with some rare exceptions, do not cluster in families. The leading hypothesis for MZ twins, which arise when a zygote splits during preimplantation stages of development, is random occurrence. We have found the first series of genes underlying the liability of being the mother of DZ twins and have shown that being an MZ twin is strongly associated with a stable DNA methylation signature in child and adult somatic tissues. Because identical twins keep this molecular signature across the lifespan, this discovery opens up completely new possibilities for the retrospective diagnosis of whether a person is an MZ twin whose co-twin may have vanished in the early stages of pregnancy. Here, we summarize the gene finding results for mothers of DZ twins based on genetic association studies followed by meta-analysis, and further present the striking epigenetic results for MZ twins.
Topics: Female; Humans; Pregnancy; Fertilization; Genetic Association Studies; Retrospective Studies; Twins, Dizygotic; Twins, Monozygotic; Infant, Newborn
PubMed: 38052159
DOI: 10.1093/humrep/dead131 -
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 -
Journal of Psychiatric Research Feb 2022Gilles de la Tourette Syndrome (GTS) is a multifactorial neurodevelopmental disorder characterized by tics and multiple comorbidities. The pathophysiology is not yet...
Gilles de la Tourette Syndrome (GTS) is a multifactorial neurodevelopmental disorder characterized by tics and multiple comorbidities. The pathophysiology is not yet fully understood, but both environmental and genetic risk factors seem to be involved. Twin studies provide important knowledge on genetic factors. We assessed the concordance of GTS and chronic tic disorders (CTD) in monozygotic (MZ) twins, and examined tic severity, symptoms of obsessive-compulsive disorder (OCD), attention deficit/hyperactivity disorder and autism spectrum disorder. Twin pairs, where at least one twin was diagnosed with any tic disorder, were identified through Danish Twin Registry, Psychiatric Central Registry, Danish National Patient Registry and National Tourette Clinic, Copenhagen University Hospital, Herlev. Zygosity was tested with single-nucleotide polymorphism (SNP) genotyping and clinical assessment was done with validated tools. 14 MZ twin pairs were included: five were discordant. Seven twin pairs were concordant for GTS, and for two pairs one twin had GTS and the other CTD. Among the twins with CTD or GTS, 50% had at least one comorbidity, which is higher than in background populations. The GTS + OCD-phenotype was significantly more frequent among GTS-concordant than among discordant twins. No statistically significant differences were found between the GTS-concordant and discordant twin pairs regarding tic severity or comorbidities. Thorough clinical assessment and SNP-based genotyping are important when conducting clinical twin studies. We found high concordance of GTS and CTD, which supports the notion that both disorders have common genetic risk factors. Further studies with larger cohorts including dizygotic twins are warranted for more conclusive results.
Topics: Autism Spectrum Disorder; Comorbidity; Humans; Tic Disorders; Tourette Syndrome; Twins, Dizygotic; Twins, Monozygotic
PubMed: 34794811
DOI: 10.1016/j.jpsychires.2021.11.019 -
JAMA Health Forum Jul 2021Wealthy adults tend to live longer than those with less wealth. However, a challenge in this area of research has been the reduction of potential confounding by factors...
IMPORTANCE
Wealthy adults tend to live longer than those with less wealth. However, a challenge in this area of research has been the reduction of potential confounding by factors associated with the early environment and heritable traits, which could simultaneously affect socioeconomic circumstances in adulthood and health across the life course.
OBJECTIVE
To identify the association between net worth at midlife and subsequent all-cause mortality in individuals as well as within siblings and twin pairs.
DESIGN SETTING AND PARTICIPANTS
This cohort study conducted a series of analyses using data from the Midlife in the United States (MIDUS) study, an ongoing national study of health and aging. The sample included adults (unrelated individuals, full siblings, and dizygotic and monozygotic twins) aged 20 to 75 years, who participated in wave 1 of the MIDUS study, which occurred from 1994 to 1996. The analyses were conducted between November 16, 2019, and May 18, 2021.
EXPOSURES
Self-reported net worth (total financial assets minus liabilities) at midlife (the middle years of life).
MAIN OUTCOMES AND MEASURES
All-cause mortality was tracked over nearly 24 years of follow-up, with a censor date of October 31, 2018. Survival models tested the association between net worth and all-cause mortality. Discordant sibling and twin analyses compared longevity within siblings and twin pairs who, given their shared early experiences and genetic backgrounds, were matched on these factors.
RESULTS
The full sample comprised 5414 participants, who had a mean (SD) age of 46.7 (12.7) years and included 2766 women (51.1%). Higher net worth was associated with lower mortality risk (hazard ratio [HR], 0.95; 95% CI, 0.94-0.97; < .001). Among siblings and twin pairs specifically (n = 2490), a similar within-family association was observed between higher net worth and lower mortality (HR, 0.94; 95% CI, 0.91-0.97; = .001), suggesting that the sibling or twin with more wealth tended to live longer than their co-sibling or co-twin with less wealth. When separate estimates were performed for the subsamples of siblings (HR, 0.94; 95% CI, 0.90-0.97; = .002), dizygotic twins (HR, 0.94; 95% CI, 0.86-1.02; = .19), and monozygotic twins (HR, 0.95; 95% CI, 0.87-1.04; = .34), the within-family estimates of the net worth-mortality association were similar, although the precision of estimates was reduced among twins.
CONCLUSIONS AND RELEVANCE
This cohort study found that wealth accumulation at midlife was associated with longevity in US adults. Discordant sibling analyses suggested that this association is unlikely to be simply an artifact of early experiences or heritable characteristics shared by families.
Topics: Adult; Aged; Cohort Studies; Female; Humans; Longevity; Longitudinal Studies; Male; Middle Aged; Social Class; Twins, Dizygotic; Twins, Monozygotic; United States; Young Adult
PubMed: 35977209
DOI: 10.1001/jamahealthforum.2021.1652 -
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 -
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