-
Twin Research : the Official Journal of... Aug 2002It has been suggested that dizygotic twin pairs share two HLA haplotypes more often than ordinary siblings and thus might be genetically more alike. We tested this...
It has been suggested that dizygotic twin pairs share two HLA haplotypes more often than ordinary siblings and thus might be genetically more alike. We tested this hypothesis in dizygotic twin pairs from the Danish Twin Registry. A total of 114 (60 female and 54 male) same-sexed healthy twin pairs aged 18-45 years participated. Dizygosity was established by means of DNA sequencing of nine polymorphic markers. HLA-A, B and Cw specificities were typed with serology, and if data were inconclusive, with DNA typing. If twin partners had the same HLA-types, they were assumed to share two haplotypes. If they had 1 HLA A, B and C antigen group in common they were assumed to share one haplotype and if they had no HLA types in common they were assumed to share zero haplotypes. Since HLA-types from parents were unavailable we could not test for identity-by-descent and thus had a risk of overestimating the number of twins sharing two haplotypes. A Chi-square test was used to compare observed numbers in each haplotype sharing group with the expected numbers. Twenty-nine (expected 28.5) twin pairs had two HLA-types in common, 52 (expected 57) had one HLA-type in common and 33 (expected 28.5) had zero HLA-types in common, p = 0.56. Our data show that DZ twins are not more similar than sibs from different pregnancies in general.
Topics: Adolescent; Adult; Female; HLA Antigens; HLA-A Antigens; HLA-B Antigens; HLA-C Antigens; Haplotypes; Humans; Male; Middle Aged; Twins, Dizygotic
PubMed: 12217235
DOI: 10.1375/13690520260186470 -
BMJ Case Reports Dec 2015Presence or eruption of teeth immediately at or after birth is a rarely reported phenomenon. This condition is referred to as natal teeth, neonatal teeth, congenital...
Presence or eruption of teeth immediately at or after birth is a rarely reported phenomenon. This condition is referred to as natal teeth, neonatal teeth, congenital teeth, fetal teeth, predeciduous teeth and dentitia praecox. The most affected teeth are lower primary central incisors with the incidence of 1:2000 for natal and 1:3500 for neonatal teeth. The aetiology of this anomaly is still not clear, however, attributes have been reported in relation to congenital teeth, multiple factors and some syndromes. The management of such cases depends on clinical characteristics of natal or neonatal teeth, as well as complications that they might cause. The aim of this paper is to discuss a rare case of occurrence of two natal teeth in both premature dizygotic twin female babies with specific emphasis on the literature review related to concerns regarding prevalence, aetiology, clinical characteristics, differential diagnosis, complications and management.
Topics: Female; Humans; Infant, Newborn; Infant, Premature; Natal Teeth; Twins, Dizygotic
PubMed: 26682836
DOI: 10.1136/bcr-2015-211930 -
Investigative Ophthalmology & Visual... Aug 2017To determine the genetic contribution to the pattern of retinal vascular branching expressed by its fractal dimension.
PURPOSE
To determine the genetic contribution to the pattern of retinal vascular branching expressed by its fractal dimension.
METHODS
This was a cross-sectional study of 50 monozygotic and 49 dizygotic, same-sex twin pairs aged 20 to 46 years. In 50°, disc-centered fundus photographs, the retinal vascular fractal dimension was measured using the box-counting method and compared within monozygotic and dizygotic twin pairs using Pearson correlation coefficients. Falconer's formula and quantitative genetic models were used to determine the genetic component of variation.
RESULTS
The mean fractal dimension did not differ statistically significantly between monozygotic and dizygotic twin pairs (1.505 vs. 1.495, P = 0.06), supporting that the study population was suitable for quantitative analysis of heritability. The intrapair correlation was markedly higher (0.505, P = 0.0002) in monozygotic twins than in dizygotic twins (0.108, P = 0.46), corresponding to a heritability h2 for the fractal dimension of 0.79. In quantitative genetic models, dominant genetic effects explained 54% of the variation and 46% was individually environmentally determined.
CONCLUSIONS
In young adult twins, the branching pattern of the retinal vessels demonstrated a higher structural similarity in monozygotic than in dizygotic twin pairs. The retinal vascular fractal dimension was mainly determined by genetic factors, which accounted for 54% of the variation. The genetically predetermination of the retinal vasculature may affect the retinal response to potential vascular disease in later life.
Topics: Adult; Cross-Sectional Studies; Female; Fractals; Humans; Male; Middle Aged; Quantitative Trait, Heritable; Retinal Vessels; Surveys and Questionnaires; Twins, Dizygotic; Twins, Monozygotic; Young Adult
PubMed: 28800646
DOI: 10.1167/iovs.17-22072 -
Clinical Chemistry Feb 2013The current methods for distinguishing the zygosities of twins include ultrasound scanning, which is nondefinitive, and amniocentesis, which is invasive. We explored the...
BACKGROUND
The current methods for distinguishing the zygosities of twins include ultrasound scanning, which is nondefinitive, and amniocentesis, which is invasive. We explored the use of massively parallel sequencing of maternal plasma DNA for the noninvasive prenatal assessment of the zygosities of twin pregnancies.
METHODS
Plasma DNA was extracted from blood collected from 8 women pregnant with twins. Target enrichment and massively parallel sequencing were performed for each plasma DNA library. Apparent fractional fetal DNA concentrations were calculated for multiple genomic regions by determining the ratio of minor to major alleles among single-nucleotide polymorphism sites. Variations in the apparent fractional fetal DNA concentrations between genomic regions were used to infer whether individual fetuses in a twin pair were genotypically different and hence dizygotic.
RESULTS
The extent of the variation in the apparent fractional fetal DNA concentration across chromosomes was 0.82-1.35 SDs for monozygotic twin pregnancies and 2.42-4.80 SDs for dizygotic twin pregnancies. The proportions of apparent fractional fetal DNA concentration values that deviated beyond the range expected for stochastic variation were 0.00%-1.93% for monozygotic twin pregnancies and 36.2%-78.1% for dizygotic twin pregnancies. After identifying a pair of twins as likely dizygotic, the method also allowed determination of the fractional fetal DNA concentrations contributed by the individual fetuses of a dizygotic twin pair.
CONCLUSIONS
Noninvasive prenatal determination of twin zygosity by maternal plasma DNA sequencing is feasible. It is also possible to determine the relative fractional fetal DNA concentrations for each fetus for dizygotic twin pregnancies.
Topics: DNA; Female; Gene Library; Humans; Maternal Serum Screening Tests; Polymorphism, Single Nucleotide; Pregnancy; Prenatal Diagnosis; Sequence Analysis, DNA; Twins, Dizygotic; Twins, Monozygotic
PubMed: 23115054
DOI: 10.1373/clinchem.2012.194068 -
Wiener Klinische Wochenschrift 2007Convergent evidence from a multitude of research designs (adoption, family, genomescan, geographical, immigrant, molecular genetic, surname, and twin studies of suicide)... (Meta-Analysis)
Meta-Analysis Review
OBJECTIVES
Convergent evidence from a multitude of research designs (adoption, family, genomescan, geographical, immigrant, molecular genetic, surname, and twin studies of suicide) suggests genetic contributions to suicide risk. The present account provides a comprehensive and up-to-date review of the twin studies on this topic.
METHODS
A total of 32 studies (19 case reports, 5 twin register-based studies, 4 population-based epidemiological studies, 4 studies of surviving co-twins) located through extensive literature search strategies are summarized and discussed here. This literature corpus was published between 1812 and 2006 in six languages and reports data from 13 countries.
RESULTS
A meta-analysis of all register-based studies and all case reports aggregated shows that concordance for completed suicide is significantly more frequent among monozygotic than dizygotic twin pairs. The results of co-twin studies rule out exclusively psychosocially based explanations of this pattern. Population-based epidemiological studies demonstrate a significant contribution of additive genetic factors (heritability estimates: 30-55%) to the broader phenotype of suicidal behavior (suicide thoughts, plans and attempts) that largely overlaps for different types of suicidal behavior and is largely independent of the inheritance of psychiatric disorders. Nonshared environmental effects (i.e. personal experiences) also contribute substantially to the risk of suicidal behavior, whereas effects of shared (family) environment do not.
CONCLUSIONS
The totality of evidence from twin studies of suicide strongly suggests genetic contributions to liability for suicidal behavior. To further research progress in this area, an extensive discussion of design limitations, shortcomings of the literature and further points is provided, including sources of bias, gaps in the literature, errors in previous reviews, age and sex effects and twin-singleton differences in suicide risk, and notes from a history-of-science view.
Topics: Cause of Death; Diseases in Twins; Female; Genetic Predisposition to Disease; Humans; Male; Mental Disorders; Phenotype; Population Surveillance; Risk Factors; Social Environment; Suicide; Suicide, Attempted; Twin Studies as Topic; Twins, Dizygotic; Twins, Monozygotic
PubMed: 17721766
DOI: 10.1007/s00508-007-0823-2 -
Urology Jun 2001Our objective was to determine whether there is a greater concordance of interstitial cystitis (IC) among monozygotic than dizygotic twins. Members of the Interstitial...
Our objective was to determine whether there is a greater concordance of interstitial cystitis (IC) among monozygotic than dizygotic twins. Members of the Interstitial Cystitis Association (ICA) who responded to a survey about first-degree family members with IC symptoms or confirmed IC were requested to identify themselves if they were 1 of a twin pair. Each twin respondent and co-twin were then evaluated via a questionnaire and acquisition of hydrodistention reports as to their meeting modified National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) criteria for IC. Of the co-twins of 8 monozygotic twin respondents, 2 had probable and 3 had confirmed IC compared with none of the co-twins of the 26 dizygotic twin respondents (including 15 female co-twins). There is a greater concordance of IC among monozygotic than dizygotic twin pairs suggesting a genetic susceptibility to IC.
Topics: Cystitis, Interstitial; Diseases in Twins; Female; Humans; Male; Middle Aged; Twins, Dizygotic; Twins, Monozygotic
PubMed: 11378045
DOI: 10.1016/s0090-4295(01)01120-7 -
Twin Research and Human Genetics : the... Dec 2017Twin research has offered evidence that monozygotic (MZ) twins are more socially close than dizygotic (DZ) twins, but has not paid much attention to the way twins...
Twin research has offered evidence that monozygotic (MZ) twins are more socially close than dizygotic (DZ) twins, but has not paid much attention to the way twins compare themselves with their co-twin. The few studies in this area suggest that 'horizontal comparisons' (social comparison motivated by solidarity or communion with others) matter more for MZ twins than for DZ twins, at least when the co-twin is the social comparison standard. Consistent with this view, we predicted higher interest in MZ twins relative to DZ twins to select their co-twin rather than other people in general as the social comparison standard. The Social Comparison Orientation (SCO) scale, which measures the inclination to compare with others in a horizontal rather than vertical mode (comparing either upward or downward), was administered in 90 MZ pairs and 57 same-sex DZ pairs (63% female; average age 18.06 years) from the Netherlands Twin Register. MZ twin pairs showed significantly higher SCO scores than DZ twin pairs (with a large effect size) on the co-twin SCO, whereas the two groups did not differ from each other on the general SCO excluding the co-twin as social comparison standard. In MZ twin pairs, anxiety was associated with social comparison with others in general, not with their co-twin. For both scales, twin resemblance was explained by additive genetic variance. The present findings provide direct evidence that horizontal comparisons with the co-twin are of particular importance for MZ twins.
Topics: Adolescent; Adult; Female; Humans; Male; Netherlands; Social Skills; Twins, Dizygotic; Twins, Monozygotic; Young Adult
PubMed: 29125095
DOI: 10.1017/thg.2017.61 -
Journal of Developmental Origins of... Feb 2021Major obstetrics and gynecology societies offer inconsistent recommendation regarding optimal delivery timing in uncomplicated dizygotic twins. We sought to investigate...
Major obstetrics and gynecology societies offer inconsistent recommendation regarding optimal delivery timing in uncomplicated dizygotic twins. We sought to investigate the impact of delivery timing within term gestation, in dizygotic twins, on the short- and long-term offspring morbidity. A prospectively analyzed cohort of dizygotic twin deliveries was conducted. All women delivered at a regional tertiary medical center, at term (≥37 0/7), between the years 1991 and 2014, were included. The primary exposure was delivery at 37 0/7-37 + 6/7 weeks, while delivery at ≥38 0/7 weeks' gestation was considered the reference. Neonatal short- and long-term outcomes according to hospitalizations of offspring up to 18 years of age due to cardiac, respiratory, hematological, neurological, and infectious morbidity were compared. Kaplan-Meier survival curves were used to compare cumulative incidences per each major-system hospitalization. Cox regression models were used to estimate the adjusted hazard ratios, while adjusting for variables with clinical importance. During the study period, 612 dizygotic twin deliveries met the inclusion criteria. Of them, 200 (31.3%) occurred at 37-37 6/7 weeks, and 412 (68.7%) occurred at ≥38 0/7 weeks' gestation. In the long-term analysis, rates of hospitalizations involving several major morbidity categories exhibited comparable rates in both groups. The Cox regression models did not demonstrate an independent association between gestational age within term and later major pediatric morbidity in offspring (total long-term morbidity: adjusted hazard ratio 1.33, 95% confidence interval 0.77-2.29). Dizygotic twin deliveries occurring at different gestational ages within term do not appear to significantly impact on major short- and long-term outcomes.
Topics: Adolescent; Adult; Child; Child, Preschool; Delivery, Obstetric; Female; Gestational Age; Hospitalization; Humans; Infant; Infant, Newborn; Male; Morbidity; Pregnancy; Pregnancy, Twin; Prospective Studies; Retrospective Studies; Time Factors; Twins, Dizygotic; Young Adult
PubMed: 32127072
DOI: 10.1017/S2040174420000100 -
Annals of Human Genetics Jun 1955
Topics: Humans; Twins; Twins, Dizygotic
PubMed: 14388534
DOI: 10.1111/j.1469-1809.1955.tb01354.x -
Twin Research and Human Genetics : the... Jun 2021We report a very rare case of monochorionic dizygotic twins conceived spontaneously. The fetuses were sex-discordant in ultrasonography despite being monochorionic...
We report a very rare case of monochorionic dizygotic twins conceived spontaneously. The fetuses were sex-discordant in ultrasonography despite being monochorionic twins. After birth, the girl and boy showed normal phenotypes but they showed blood chimerism in karyotype and blood group type.
Topics: Blood Group Antigens; Chimerism; Female; Humans; Karyotype; Karyotyping; Male; Twins, Dizygotic; Twins, Monozygotic
PubMed: 34127172
DOI: 10.1017/thg.2021.20