Inheritance of finger pattern types in MZ and DZ twins

Digital patterns of a sample on twins were analyzed to estimate the resemblance between monozygotic (MZ) and dizygotic (DZ) twins and to evaluate the mode of inheritance by the use of maximum likelihood based variance decomposition analysis. MZ twin resemblance of finger pattern types appears to be more pronounced than in DZ twins, which suggests the presence of genetic factors in the forming of fingertip patterns. The most parsimonious model shows twin resemblance in count of all three basic finger patterns on 10 fingers. It has significant dominant genetic variance component across all fingers. In the general model, the dominant genetic variance component proportion is similar for all fingertips (about 60%) and the sibling environmental variance is significantly nonzero, but the proportion between additive and dominant variance components was different. Application of genetic model fitting technique of segregation analyses clearly shows mode of inheritance. A dominant genetic variance component or a specific genetic system modifies the phenotypic expression of the fingertip patterns. The present study provided evidence of strong genetic component in finger pattern types and seems more informative compared to the earlier traditional method of correlation analysis.     

Retrospective determination of chorion type in twins using a simple questionnaire.

This study investigates the validity of retrospective determination of chorion type by asking the question to the mother about the number of placentas. In the "East Flanders Prospective Twin Survey" (EFPTS), accurate information on the placentation and zygosity of the multiples was collected prospectively. The mothers of 231 monozygotic (95 dichorionic and 136 monochorionic) twins and 255 dizygotic twins were asked to fill in a simple questionnaire regarding 1). the zygosity and 2). the number of placentas of their twins. The accuracy of the response to the question on "the number of placentas" was 60% for monozygotic twins and 37% for dizygotic twins. The accuracy of the response to the question on the zygosity of the twins was 93% for monozygotic and 95% for dizygotic twins. If the questionnaire was used for the determination of chorion type, a total of 31 monozygotic twins (13%) should have been assigned as dichorionic on the fact that there were two separate placentas. Of these, 10 (32%) are monochorionic and 12 (39%) were falsely reported as having two placentas. We conclude from these findings that this simple questionnaire method is unreliable for the retrospective determination of the chorion type.     

Fingerprint recognition with identical twin fingerprints

Fingerprint recognition with identical twins is a challenging task due to the closest genetics-based relationship existing in the identical twins. Several pioneers have analyzed the similarity between twins' fingerprints. In this work we continue to investigate the topic of the similarity of identical twin fingerprints. Our study was tested based on a large identical twin fingerprint database that contains 83 twin pairs, 4 fingers per individual and six impressions per finger: 3984 (83*2*4*6) images. Compared to the previous work, our contributions are summarized as follows: (1) Two state-of-the-art fingerprint identification methods: P071 and VeriFinger 6.1 were used, rather than one fingerprint identification method in previous studies. (2) Six impressions per finger were captured, rather than just one impression, which makes the genuine distribution of matching scores more realistic. (3) A larger sample (83 pairs) was collected. (4) A novel statistical analysis, which aims at showing the probability distribution of the fingerprint types for the corresponding fingers of identical twins which have same fingerprint type, has been conducted. (5) A novel analysis, which aims at showing which finger from identical twins has higher probability of having same fingerprint type, has been conducted. Our results showed that: (a) A state-of-the-art automatic fingerprint verification system can distinguish identical twins without drastic degradation in performance. (b) The chance that the fingerprints have the same type from identical twins is 0.7440, comparing to 0.3215 from non-identical twins. (c) For the corresponding fingers of identical twins which have same fingerprint type, the probability distribution of five major fingerprint types is similar to the probability distribution for all the fingers' fingerprint type. (d) For each of four fingers of identical twins, the probability of having same fingerprint type is similar.     

Metacarpo-phalangeal and ring creases in twins

Metacarpo-phalangeal creases including the ring crease were studied on the middle finger of Japanese twins. The mean of differences and the correlation coefficient of the ring crease index as well as fine morphological features showed that the similarity between twins is greater in monozygotic twins than in dizygotic ones. The intrapair similarity in monozygotic twins is almost the same as that between right and left hands of an individual. For the diagnosis of zygosity this trait will be available.     

指纹遗传的双生子研究——Ⅱ.指纹纹型的研究

采用双生子法对26对MZ及24对DZ的指纹纹型进行研究,发现在各类指纹纹型中,斗形最多,桡箕最少。男女间纹型频率差异不大。纹型的左右手对称性为77.20％。作者提出了指纹系数的计算公式,即[(斗形纹数)+(斗形纹数+箕形纹数)]×100％。认为以此来反映10指纹型的构成和复杂程度,以及分析指纹较为合适。 纹型和三辐线在MZ与DZ对间一致率的比较,以及指纹系数、花样强度和生物学指纹价在MZ与DZ对间的相关系数的比较,发现MZ对间的一致率及相关系数明显高于DZ对间的一致率及相关系数,其遗传度为56—92％。本文发现指纹系数在MZ对间并非完全一致,即MZ对间纹型不一致,且指纹系数呈一连续常态分布。纹型的分析表明,指纹纹型以多基因遗传的可能性较大,但不能排除异质性遗传的可能。     

Genetic determination of the human EEG

Summary In this article, we have discussed recent progress in quantifying the genetically determined component of the resting EEG. This progress has been made possible in particular by the application of advanced information processing techniques such as supervised learning, and the development of a problem-oriented similarity concept. Our work aimed at modeling previous findings regarding the distinct individuality of human brain-wave patterns, the high similarity between the EEGs of monozygotic twins, and the average within-pair similarity of dizygotic twins. Thus, we had three objectives: First, we wanted to improve the quantification of EEG characteristics with respect to reproducibility and specificity by means of adaptive procedures and repeated measurements. Second, we wanted to compare the typical within-subject EEG similarity with the typical within-pair EEG similarity of monozygotic and dizygotic twins brought up together. Finally, we were interested in the degree to which environmental factors affect the characteristics of human brain-wave patterns. Our investigations were based on the empirical data derived from five different populations: (1) 81 healthy subjects, (2) 24 pairs of monozygotic twins brought up together, (3) 25 pairs of dizygotic twins brought up together, (4) 28 pairs of monozygotic twins reared apart, and (5) 21 pairs of dizygotic twins reared apart. Following our similarity conception, repeated measurements on the set of 81 individuals were used as design samples, and new registrations from the same individuals taken 14 days later were referred to as test samples in order to develop the appropriate method and to determine all required calibration parameters. This specific approach allowed us to construct EEG spectral patterns which, with a specificity and reproductibility of>90% each, largely met the requirements of genetic EEG studies. Hence, we were able systematically to investigate the within-pair EEG similarity of our twin samples. Our results provided ample evidence that the individual characteristics of the resting EEG are primarily determined by genetic factors: (1) There exists an almost perfect one-to-one mapping between each individual and his EEG; (2) monozygotic twins proved, with respect to their resting EEGs, to be only slightly less like one another (if there is any difference at all) than each person is to himself over time; (3) the average within-pair EEG similarity estimated from a sufficiently representative sample of dizygotic twins is significantly above the inter-individual EEG similarity between unrelated persons (this finding holds true for both samples of dizygotic twins brought up together and reared apart, and there is also no statistically significant difference in the resting EEG between these two samples) and, (4) the EEGs of monozygotic twins reared apart are obviously as similar to each other as are the EEGs of the same person over time, and there is no statistically significant difference in the resting EEG between the two populations of monozygotic twins brought up together and monozygotic zygotic twins reared apart.     

New chromosome 11p15 epigenotypes identified in male monozygotic twins with Beckwith-Wiedemann syndrome

Beckwith-Wiedemann syndrome (BWS) is an overgrowth syndrome demonstrating heterogeneous molecular alterations of two imprinted domains on chromosome 11p15. The most common molecular alterations include loss of methylation at the proximal imprinting center, IC2, paternal uniparental disomy (UPD) of chromosome 11p15 and hypermethylation at the distal imprinting center, IC1. An increased incidence of female monozygotic twins discordant for BWS has been reported. The molecular basis for eleven such female twin pairs has been demonstrated to be a loss of methylation at IC2, whereas only one male monozygotic twin pair has been reported with this molecular defect. We report here two new pairs of male monozygotic twins. One pair is discordant for BWS; the affected twin exhibits paternal UPD for chromosome 11p15 whereas the unaffected twin does not. The second male twin pair is concordant for BWS and both twins of the pair demonstrate hypermethylation at IC1. Thus, this report expands the known molecular etiologies for BWS twins. Interestingly, these findings demonstrate a new epigenotype-phenotype correlation in BWS twins. That is, while female monozygotic twins with BWS are likely to show loss of imprinting at IC2, male monozygotic twins with BWS reflect the molecular heterogeneity seen in BWS singletons. These data underscore the need for molecular testing in BWS twins, especially in view of the known differences among 11p15 epigenotypes with respect to tumor risk.     

The potential use of artificially produced monozygotic twins for comparative experiments

The uniformity of twins has been examined by assembling estimates of the intraclass correlation coefficient (rho(I)) available in the literature for a variety of parameters studied in cattle monozygotic twins and human dizygotic and monozygotic twins. The values of rho(I) vary considerably between parameters. In human monozygotic twins rho(I) is always larger compared to that found in dizygotic twins. There is insufficient evidence to determine whether artificial monozygotic twins are more uniform than natural monozygotic twins. A new measure of twin uniformity, given by T (3) = 1 (1-rho (I)) , is introduced. In practice 2T(3) gives the number of animals chosen at random that one member of a twin pair can replace without loss of statistical efficiency. A useful class of experimental designs for the exploitation of twin uniformity is incomplete block designs. These designs are defined by (v, k, b), where v is the number of treatments to be compared, k = 2, and b is the number of twin pairs. Each design has an associated efficiency (E). Provided rho(I)>1-E, an incomplete block design will be advantageous. In general, when only a few twin pairs are available, this relation will only hold for monozygotic and not dizygotic twins. Suitable arrangements of treatment comparisons for designs (3,2,8), (4,2,9), (5,2,10), (6,2,11) are presented.     

Validated zinc finger protein designs for all 16 GNN DNA triplet targets.

The Cys(2)-His(2)-type zinc finger DNA-binding proteins can be engineered to bind specifically to many different DNA sequences. A single zinc finger typically binds to a 3-4-base pair DNA subsite. One strategy for design is to identify highly specific fingers that recognize each of the 64 possible DNA triplets. We started with a subgroup of the 64 triplets, the GNN-binding fingers. The GNN-binding fingers have been examined in several studies, but previous studies did not produce specific fingers for all of the 16 GNN triplets. These previous studies did not provide any information on the possible positional or context effects on the performance of these fingers. To identify the most specific design and take the possible positional effects into consideration, we did a large-scale site selection experiment on our GNN designs. From this study, we identified very specific fingers for 14 of the 16 GNN triplets, demonstrating for the first time a clear positional dependence for many of the designs. Further systematic specificity study reveals that the in vivo functionality of these zinc finger proteins in a reporter assay depends on their binding affinities to their target sequences, thus giving a better understanding of how these zinc finger proteins might function inside cells.     

Evidence for higher heritability of somatotype compared to body mass index in female twins

The influence of genetics on human physique and obesity has been addressed by the literature. Evidence for heritability of anthropometric characteristics has been previously described, mainly for the body mass index (BMI). However, few studies have investigated the influence of genetics on the Heath-Carter somatotype. The aim of the present study was to assess the heritability of BMI and somatotype (endomorphy, mesomorphy, and ectomorphy) in a group of female monozygotic and dizygotic twins from childhood to early adulthood. A total of 28 females aged from 7 to 19 years old were studied. The group included 5 monozygotic and 9 dizygotic pairs of twins. The heritability was assessed by the twin method (h(2)). The anthropometric measures and somatotype were assessed using standard validated procedures. Significant differences between monozygotic and dizygotic pairs of twins were found for height, endomorphy, ectomorphy, and mesomorphy, and the heritability for these measures was high (h(2) between 0.88 and 0.97). No significant differences were found between monozygotic and dizygotic twins for weight, and the BMI and the heritability indexes were lower for these measures (respectively 0.42 and 0.52). The results of the present study have indicated that the somatotype may be more sensible to genetic influences than the BMI in females.     

Zygosity diagnosis in young twins by questionnaire for twins' mothers and twins' self-reports.

The present study deals with the determination of zygosity in twins of childhood age by simple questionnaire. The subjects were 224 twin pairs and their mothers, consisting of 159 monozygotic and 65 same-sex dizygotic pairs, identified by genetic markers including DNA samples. Mothers of twins responded to 19 questionnaire items dealing with twin similarity in 16 items about physical features and 3 items about the degree of similarity and frequency of being mistaken (confusion of identity) when twins were about 1 year of age. The twins themselves responded to three questionnaire items dealing with only confusion of identity items. The results of stepwise logistic regression analysis were as follows: the total accuracy of the mothers' questionnaire was 91.5% when using only the items dealing with confusion of identity. This accuracy was slightly lower than that obtained by twins' self-reports dealing with nearly the same question items of confusion of identity, answered by both twins separately with 93.3% accuracy. The total accuracy of mothers' questionnaire responses rose to 95.1% when we used all 19 items. In addition to "the frequency of being mistaken", two physical features, namely "shape of fingers" and "shape of eyebrow", were very informative. In conclusion, twin zygosity can be estimated by the use of the mothers' simple questionnaire with sufficient accuracy even in very young twins about 1 year of age.     

Spatial and temporal expression pattern of retinoic acid receptor genes during mouse bone development

Spatial and temporal expression pattern of retinoic acid receptor (RAR) genes was investigated in mouse finger bones during development by an in situ hybridization method with riboprobes synthesized from a human cDNA of the RAR-alpha. We found that the RAR genes are expressed intensively and specifically in calcifying fronts of the mouse finger bones, whereas the expression pattern is rather uniform in the limb buds and cartilage matrices of the embryonic fingers. Our findings are consistent with the fact that vitamin A is essential for normal mammalian bone development.     

Analysis of the Covariance Structure of Digital Ridge Counts in the Offspring of Monozygotic Twins

Improved methods for analysis of covariance structures now permit the rigorous testing of multivariate genetic hypotheses. Using J?reskog's Lisrel IV computer program we have conducted a confirmatory factor analysis of dermal ridge counts on the individual fingers of 509 offspring of 107 monozygotic twin pairs. Prior to the initiation of the model-fitting procedure, the sex-adjusted ridge counts for the offspring of male and female twins were partitioned by a multivariate nested analysis of variance yielding five 10 X 10 variance-covariance matrices containing a total of 275 distinctly observed parameters with which to estimate latent sources of genetic and environmental variation and test hypotheses about the factor structure of those latent causes. To provide an adequate explanation for the observed patterns of covariation, it was necessary to include additive genetic, random environmental, epistatic and maternal effects in the model and a structure for the additive genetic effects which included a general factor and allowed for hand asymmetry and finger symmetry. The results illustrate the value of these methods for the analysis of interrelated metric traits.     

A study of the occurrence of monochorionic and monozygotic twinning in the pig

In humans as well as in most farm animals, monozygotic twins have been described. Nevertheless, only a few reports of twinning in the pig have been published. It has been suggested that monozygotic twins are formed during the first 14 days of pregnancy. This monozygotic twin study includes the investigation of porcine monochorionic embryos from 76 sows at days 26–29 post-insemination (p.i.), as well as an examination of 10 whole litters at days 21–22 p.i. In the former group, 29% of the sows carried monochorionic embryos. Based on DNA profiling using microsatellite markers, one monozygotic twin pair was found among these embryos. In the latter group, three monozygotic twin pairs were identified. Thus, it can be concluded that although the occurrence of monozygotic twins in pigs is a sporadic event, the fusion of extra-embryonic membranes is relatively common.     

Intra-Monozygotic Twin Pair Discordance and Longitudinal Variation of Whole-Genome Scale DNA Methylation in Adults

Monozygotic twins share identical genomic DNA and are indistinguishable using conventional genetic markers. Increasing evidence indicates that monozygotic twins are epigenetically distinct, suggesting that a comparison between DNA methylation patterns might be useful to approach this forensic problem. However, the extent of epigenetic discordance between healthy adult monozygotic twins and the stability of CpG loci within the same individual over a short time span at the whole-genome scale are not well understood. Here, we used Infinium HumanMethylation450 Beadchips to compare DNA methylation profiles using blood collected from 10 pairs of monozygotic twins and 8 individuals sampled at 0, 3, 6, and 9 months. Using an effective and unbiased method for calling differentially methylated (DM) CpG sites, we showed that 0.087%–1.530% of the CpG sites exhibit differential methylation in monozygotic twin pairs. We further demonstrated that, on whole-genome level, there has been no significant epigenetic drift within the same individuals for up to 9 months, including one monozygotic twin pair. However, we did identify a subset of CpG sites that vary in DNA methylation over the 9-month period. The magnitude of the intra-pair or longitudinal methylation discordance of the CpG sites inside the CpG islands is greater than those outside the CpG islands. The CpG sites located on shores appear to be more suitable for distinguishing between MZ twins.     

Are twins and singletons comparable? A study of disease-related and lifestyle characteristics in adult women.

The classic twin study is sometimes described as "the perfect natural experiment" for the investigation of the aetiology of complex disease, but assumptions of the twin design need to be empirically tested if their results are to be considered unbiased and representative of singleton populations. In this study comparisons of disease and prevalence of lifestyle characteristics have been made between twin participants in the St Thomas' Hospital UK adult twin registry, the largest twin volunteer register in the UK for the study of diseases of ageing, and a parallel population-based study of singleton women. The only differences found were for weight, where monozygotic (MZ) twins were lighter and had a smaller variance than dizygotic (DZ) twins and singletons. For the other variables studied, volunteer twins were not found to differ from age-matched singleton women in distribution or prevalence of: bone mineral density, osteoarthritis, blood pressure, hypertensive drug use, height, history of hysterectomy and ovariectomy, menopausal status and current alcohol and overall tobacco consumption. We conclude that the results of twin studies can be generalised to singleton populations for these measures and disease outcomes.     

Zinc finger proteins as templates for metal ion exchange and ligand reactivity. Chemical and biological consequences

Zinc finger reactions with inorganic ions and coordination compounds are as diverse as the zinc fingers themselves. Use of metal ions such as Co(2+) and Cd(2+) has given structural, thermodynamic and kinetic information on zinc fingers and zinc-finger-DNA/RNA interactions. It is a general truism that alteration of the coordination sphere in the finger environment will disrupt the recognition with DNA/RNA and this has implications for mechanism of toxicity and carcinogenesis of metal ions. Structural zinc fingers are susceptible to electrophilic attack and the recognition that the coordination sphere of inorganic compounds may be modulated for control of electrophilic attack on zinc fingers raises the possibility of systematic studies of zinc fingers as drug targets using inorganic chemistry. Some inorganic compounds such as those of As(III) and Au(I) may exert their biological effects through inactivation of zinc fingers and novel approaches to specifically attack the zinc-bound ligands using Co(III)-Schiff bases and Platinum(II)-Nucleobase compounds have been proposed. The genomic importance of zinc fingers suggests that the "coordination chemistry" of zinc fingers themselves is ripe for exploration to design new targets for medicinal inorganic chemistry.     

Whole genome and exome sequencing of monozygotic twins discordant for Crohn’s disease

Background

Crohn’s disease (CD) is an inflammatory bowel disease caused by genetic and environmental factors. More than 160 susceptibility loci have been identified for IBD, yet a large part of the genetic variance remains unexplained. Recent studies have demonstrated genetic differences between monozygotic twins, who were long thought to be genetically completely identical.

Results

We aimed to test if somatic mutations play a role in CD etiology by sequencing the genomes and exomes of directly affected tissue from the bowel and blood samples of one and the blood-derived exomes of two further monozygotic discordant twin pairs. Our goal was the identification of mutations present only in the affected twins, pointing to novel candidates for CD susceptibility loci. We present a thorough genetic characterization of the sequenced individuals but detected no consistent differences within the twin pairs. An estimate of the CD susceptibility based on known CD loci however hinted at a higher mutational load in all three twin pairs compared to 1,920 healthy individuals.

Conclusion

Somatic mosaicism does not seem to play a role in the discordance of monozygotic CD twins. Our study constitutes the first to perform whole genome sequencing for CD twins and therefore provides a valuable reference dataset for future studies. We present an example framework for mosaicism detection and point to the challenges in these types of analyses.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-564) contains supplementary material, which is available to authorized users.     

Twin births to mothers who are twins: a registry based study.

OBJECTIVES: To estimate the risk of having twin infants for mothers who are twins; to investigate the genetic influence on twinning. DESIGN: Retrospective study of multiple births in two nationwide registries. SETTING: Sweden. SUBJECTS: Multiple births among 31,586 deliveries between 1973 and 1991 to women who were twins. MAIN OUTCOME MEASURES: Numbers of monozygotic and dizygotic twin births expected and estimated. RESULTS: Women who are dizygotic twins have a moderately increased risk of having twins (relative risk 1.30, 95% confidence interval 1.14 to 1.49) which seems to be completely the result of dizygotic twinning. When a mother is a monozygotic twin, her risk of having twins of the same sex is significantly increased (1.47; 1.10 to 1.97). This is the result of an excess of monozygotic twins (39 pairs estimated, 18 expected). CONCLUSIONS: Women who are twins have an increased risk of giving birth to twins. Genetic components of monozygotic and dizygotic twinning seem to be independent.