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Journal of Obstetrics and Gynaecology :... Jul 2011
Topics: Chimerism; Female; Humans; Infant, Newborn; Infant, Premature; Male; Pregnancy; Sex Characteristics; Twins, Dizygotic
PubMed: 21627435
DOI: 10.3109/01443615.2011.570813 -
American Journal of Medical Genetics.... Jul 2013Chimerism occurs when an organism contains cells derived from more than one distinct zygote. We focus on monochorionic dizygotic twin blood chimerism, and particularly... (Review)
Review
Chimerism occurs when an organism contains cells derived from more than one distinct zygote. We focus on monochorionic dizygotic twin blood chimerism, and particularly twin-twin transfusion syndrome in such pregnancies. For years, researchers have understood chimerism to be a common phenomenon in cattle. Although, this review will not delve deeply into animal chimerism, an understanding of chimerism in the animal world can provide clues regarding health implications for human chimeras. This report serves two purposes: an update and assessment of the twins we reported previously in 2010 [Assaf et al., 2010] and a review on dizygotic monochorionic chimeric twins. First, our updated assessment of the twins shows no identifiable regression of Müllerian sex derivatives in the female, and normal neurodevelopment was documented in both. Our research has suggested several key points; one that blood chimerism persists from fetal life to at least age two years. Second, chimerism in humans is not as rare as previously thought, although it has been studied only recently. Third, assisted reproductive technologies appear to increase the risk of monochorionic dizygotic twin pregnancies.
Topics: Animals; Autoimmune Diseases; Chimerism; Chorion; Diseases in Twins; Female; Fetofetal Transfusion; Follow-Up Studies; Humans; Male; Mouth Mucosa; Neoplasms; Pregnancy; Pregnancy, Twin; Stem Cells; Twins, Dizygotic
PubMed: 23703979
DOI: 10.1002/ajmg.a.35957 -
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 -
Schizophrenia Bulletin 1992Geneticists and twin researchers have long debated the relative merits of two alternative measures of twin concordance: the pairwise and probandwise concordance rates.... (Review)
Review
Geneticists and twin researchers have long debated the relative merits of two alternative measures of twin concordance: the pairwise and probandwise concordance rates. The results of this debate are now quite clear, for almost every application the probandwise rate is preferred over the pairwise rate. In a recent review of schizophrenia twin studies, however, Torrey (1992) chose to analyze pairwise rather than probandwise rates. Torrey's use of pairwise rates led him to conclude that the monozygotic twin concordance for schizophrenia is weaker than what is widely accepted, and that, by implication, the magnitude of the genetic contribution to schizophrenia has been overestimated. In this brief commentary, we review the relative strengths and weaknesses of the pairwise and probandwise rates and show that Torrey's conclusion is based upon his incorrect use of pairwise rates. Twin studies of schizophrenia continue to support the existence of a strong genetic influence on the development of schizophrenia.
Topics: Female; Humans; Male; Neurologic Examination; Parents; Probability; Schizophrenia; Schizophrenic Psychology; Twins, Dizygotic; Twins, Monozygotic
PubMed: 1621065
DOI: 10.1093/schbul/18.2.171 -
Scientific Reports Oct 2023Considerable evidence supports the role of present-moment attention, a central feature of mindfulness, in subjective wellbeing maintenance and enhancement. Yet it is not...
Considerable evidence supports the role of present-moment attention, a central feature of mindfulness, in subjective wellbeing maintenance and enhancement. Yet it is not clear why such a relation exists. This study examined the genetic and environmental contributions of present-moment attention to subjective wellbeing. Consistent with the "generalist genes hypothesis" and prior evidence, we hypothesized that presence and subjective wellbeing would show a substantial genetic correlation and smaller environmental correlation. Using a large epidemiological sample of healthy 16-year-old twins in the United Kingdom (N = 1136 monozygotic (MZ) and dizygotic (DZ) twin pairs), genetic overlap was found between presence and the cognitive component of subjective wellbeing (life satisfaction), and to a lesser extent, the affective component of subjective wellbeing (operationalized as happiness). The non-shared environmental overlap between these constructs was substantial. This study provides the first evidence known to us showing that present-centered attention, a primary component of mindfulness, has both genetic and environmental overlap with subjective wellbeing. The findings have implications for understanding mechanisms by which presence is associated with positive emotions and life satisfaction, and suggest, pending additional research, that mindfulness-based interventions to enhance wellbeing may be best suited to those with a genetic propensity toward mindful presence.
Topics: Humans; Adolescent; Twins, Dizygotic; Happiness; Mindfulness; United Kingdom; Twins, Monozygotic
PubMed: 37838734
DOI: 10.1038/s41598-023-42810-x -
American Journal of Medical Genetics.... May 2009Monozygotic twins (MZ) are rarely absolutely "identical." This review discusses the types of genetic/epigenetic and prenatal environmental post-zygotic mechanisms that... (Review)
Review
Monozygotic twins (MZ) are rarely absolutely "identical." This review discusses the types of genetic/epigenetic and prenatal environmental post-zygotic mechanisms that cause discordance within such twin pairs. Some of these mechanisms--ranging from heterokaryotypia to skewed X-chromosome inactivation--may cause extreme discordance, but these extremes are merely the more emphatic examples of discordance that, to some degree, underlies the majority of MZ twin pairs. Because of the entrenched misconception that MZ twins are necessarily identical, many MZ twin pairs are mistakenly designated as dizygotic (DZ). Clinical benefits to accurate zygosity determination include correct solid organ transplantation matching, if one twin requires donation for a non-genetically mediated disease; the opportunity of preventive management for disorders that do not manifest synchronously; and better counseling to parents regarding their individually unique, and often psychologically puzzling, twin offspring. In twin pairs with complex and confusing biological origins, more detailed zygosity testing may be required. For example, intermediate trigametic and tetragametic chimeric dizygotic twins are reviewed, some of whom are, nevertheless, monochorionic (MC). Because of inter-fetal vascular anastomoses in MC twins, genetic results from blood samples may not accurately reflect discordance in solid organs. Previously, it was thought that MZ twinning was some sort of embryological fluke. However, familial monozygotic twinning is more common than suggested by the literature. Seven new families are presented in an accompanying paper. Despite the difficulties and dangers of twin pregnancy (especially so for MC twins), human twinning persists, and continues to both challenge and fascinate parents, clinicians and geneticists.
Topics: Chimera; Humans; Teratogens; Twins, Dizygotic; Twins, Monozygotic
PubMed: 19363805
DOI: 10.1002/ajmg.c.30212 -
Prenatal Diagnosis May 2018To evaluate the incidence and characteristics of unusual twinning by using single nucleotide polymorphism (SNP) array to identify twin zygosity.
OBJECTIVE
To evaluate the incidence and characteristics of unusual twinning by using single nucleotide polymorphism (SNP) array to identify twin zygosity.
METHODS
This study reviewed 386 twin pairs who were seen for prenatal or postnatal diagnosis and underwent SNP array to detect zygosity.
RESULTS
The incidence of monozygotic (MZ) twins was 11.36% (25/220) in the assisted reproductive technology (ART)-conceived group. Monochorionic dizygotic twins represented 3 of 24 monochorionic ART-conceived twin pairs (3/24, 12.50%) but none in the spontaneous twin pairs. Among 4 single-embryo transfer twin pairs, 3 represented unusual twinning, including 2 MZ twin pairs with discordant karyotypes and 1 dizygotic twin pair of the same gender. Of the pregnancies with 2 or more embryos transferred, 7.77% (15/193) were MZ. Additionally, there was a dichorionic monozygotic twin pair with placental vascular anastomoses from a day-5 blastocyst transfer.
CONCLUSION
Single nucleotide polymorphism array can provide zygosity diagnosis in addition to chromosomal copy number variation and uniparental disomy detection. ART twin pregnancies have a risk of unusual twinning, such as monochorionic dizygotic, single-embryo transfer twin pairs with discordant karyotypes or dizygotic, and dichorionic monozygotic with vascular anastomoses from day-5 transfer.
Topics: Female; Humans; Oligonucleotide Array Sequence Analysis; Polymorphism, Single Nucleotide; Pregnancy; Pregnancy, Twin; Prenatal Diagnosis; Reproductive Techniques, Assisted; Retrospective Studies; Twins, Dizygotic; Twins, Monozygotic
PubMed: 29569732
DOI: 10.1002/pd.5255 -
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 -
Fetal and Pediatric Pathology Oct 2019Dizygotic twin pregnancies with discordant manifestation of abnormalities with unclear etiology are of interest because they arise in the same environment. We present...
Dizygotic twin pregnancies with discordant manifestation of abnormalities with unclear etiology are of interest because they arise in the same environment. We present a dizygotic third trimester twin placenta with discordant villous maturation, one placenta lacking developed syncytiocapillary membranes. The twins were eutrophic with no perinatal or postnatal complications. Discordant manifestation of villous maturation in dizygotic twin placentas could be a hint for a genetic rather than an environmental etiology. Villous maturation defect may be underrecognized and has been associated with perinatal morbidity and stillbirth in the late third trimester. Proper recognition is important because of the increased recurrence risk of villous dysmaturity.
Topics: Adult; Female; Humans; Infant, Newborn; Placenta; Placentation; Pregnancy; Pregnancy, Twin; Twins, Dizygotic
PubMed: 31025579
DOI: 10.1080/15513815.2019.1604924 -
Twin Research and Human Genetics : the... Feb 2020Dichorionic diamniotic (DCDA) twin pregnancies after single blastocyst embryo transfer have been reported recently, although a blastocyst ovum is generally believed to...
Dichorionic diamniotic (DCDA) twin pregnancies after single blastocyst embryo transfer have been reported recently, although a blastocyst ovum is generally believed to divide into monochorionic twin pregnancy. We investigated the incidence of DCDA twin pregnancy after single blastocyst embryo transfer and their zygosity. This prospective cohort study included 655 consecutive twin pregnancies that were managed from 2006 to 2014 at our institution. Chorionicity and amnionicity were determined using first-trimester ultrasonography and/or placental pathology. Zygosity was analyzed if the cases were DCDA twins after single blastocyst embryo transfer. Among 655 twin pregnancies, there were 348 DCDA cases, 295 monochorionic diamniotic (MCDA) cases and 12 monochorionic monoamniotic cases. Single blastocyst embryo transfer was performed in 43 cases. Six out of the 43 (14%) cases involved DCDA twin pregnancies and the other 37 cases involved MCDA twin pregnancies. Three DCDA twins born after single blastocyst embryo transfer, wherein frozen embryo transfer (FET) was performed in the natural cycle, were dizygotic, and the other three cases, wherein FET with hormone replacement therapy was performed, were monozygotic. DCDA twin pregnancy occurred in 14% (7% for monozygotic and 7% for dizygotic) of twin pregnancies after single blastocyst embryo transfer cases.
Topics: Adult; Amnion; Blastocyst; Chorion; Cohort Studies; Embryo Transfer; Female; Humans; Pregnancy; Pregnancy Trimester, First; Prospective Studies; Twins, Dizygotic; Twins, Monozygotic; Ultrasonography, Prenatal
PubMed: 32209150
DOI: 10.1017/thg.2020.5