Genetic analysis of bilateral dermatoglyphic asymmetry in twins and their parents

The data for this study were collected on 64 twin pairs (30 MZ and 34 DZ) and their 128 parents. Two following hypotheses were evaluated: 1. Bilateral asymmetry is significantly genetically controlled; 2. The twinning phenomenon would affect the magnitude of bilateral asymmetry. The results revealed no statistically significant differences between mean values of MZ and DZ twins and their parents for the majority of the traits. Significant differences were recorded for only 6 of 96 comparisons (6%). Analysis of variance revealed separated sources of MZ, DZ and singleton variance. F-ratios, contrasting variances between different groups were significant for 26 of 96 comparisons (27%) showing heterogeneity of variance between zygosities and between twins and their parents. In addition, environmental covariance appeared to be larger for MZ than DZ with respect to directional asymmetry (DA) for all 16 traits and fluctuating asymmetry (FA) for 14 traits. These observations showed complex environmental determinism for bilateral asymmetry for the majority of dermatoglyphic traits. Significant genetic variance ratios (GVRs) were observed for four variables (25%) with respect to DA and three variables (18.75%) with respect to FA. All these significant GVRs were rendered insignificant because of evidence of greater environmental covariance for MZ twins, except possibly for DA for URC4.     

Abuse of elderly people by their carers.

OBJECTIVE--To assess the prevalence of abuse of elderly people by their carers and the characteristics of abusers and the abused. DESIGN--Information on abuse and risk factors was collected over six months from carers and patients. Risk factors were identified in the abused group and compared with those in a non-abused control group. SETTING--Carers were interviewed at home; patients were examined in the wards of Putney and Barnes geriatric hospitals, London. SUBJECTS--All patients referred from any source for respite care to the geriatric services over a six month period and their carers. MAIN OUTCOME MEASURES--Amount of physical and verbal abuse or neglect. Quantification of risk factors and correlation with the presence or absence of abuse. RESULTS--45% Of carers openly admitted to some form of abuse. Few patients admitted abuse. The most significant risk factor for physical abuse was alcohol consumption by the carer (p less than 0.001). Other significant risk factors were a poor pre-morbid relationship and previous abuse over many years. Abuse was often reciprocated and was associated with social dysfunction in many patients. Service delivery, respite care, and level of mental and physical disability were not significantly associated with abuse. CONCLUSION--The high level of abuse found in elderly patients in respite care was particularly associated with alcohol abuse and long term relationships of poor quality, which are difficult to change. Even with increased provision of services, care in the community may not be the best solution for these people.     

Genetic analysis of indicators of cholesterol synthesis and absorption: lathosterol and phytosterols in Dutch twins and their parents.

Significant familial aggregation was observed for plasma levels of lathosterol (an indicator of whole-body cholesterol synthesis) and plant sterols campesterol and beta-sitosterol (indicators of cholesterol absorption) in 160 Dutch families consisting of adolescent mono- and dizygotic twin pairs and their parents. For lathosterol a moderate genetic heritability in parents and offspring (29%) was found. In addition, shared environment also contributed significantly (37%) to variation in plasma lathosterol concentrations in twin siblings. However, a model with different genetic heritabilities in the two generations (10% in parents and 68% in offspring) fitted the data almost as well. For plasma plant sterol concentrations high heritabilities were found. For campesterol heritability was 80% and for beta-sitosterol it was 73%, without evidence for differences in heritability between sexes or generations. No influence of common environmental influences shared by family members was seen for either campesterol or beta-sitosterol. Taken together, these results confirm and expand the hypothesis that individual differences in plasma levels of noncholesterol sterols are moderately (lathosterol) to highly (plant sterols) heritable.     

Alternative splicing and gene co-expression network-based analysis of dizygotic twins with autism-spectrum disorder and their parents

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with high heritability, however, understanding the complexity of the underlying genetic basis has proven to be a challenging task. We hypothesized that dissecting the aberrations in alternative splicing (AS) and their effects on expression networks might provide insight. Therefore, we performed AS and co-expression analyses of total RNA isolated from Peripheral Blood Mononuclear Cells (PBMCs) of two pairs of dizygotic (DZ) twins with non-syndromic autism and their parents. We identified 183 differential AS events in 146 genes, seven of them being Simons Foundation Autism Research Initiative (SFARI) Category 1–3 genes, three of which had previously been reported to be alternatively spliced in ASD post-mortem brains. Gene co-expression analysis identified 7 modules with 513 genes, 5 of which were SFARI Category 1 or Category 2 genes. Among differentially AS genes within the modules, ZNF322 and NR4A1 could be potentially interesting targets for further investigations.     

Protein crystals and their evil twins.

Different types of crystal twinning are reviewed with an emphasis on how to detect the phenomenon from protein diffraction data. The recent literature and a database survey both serve as reminders to perform routine checks whenever twinning is a possibility.     

Self-reported reading problems in parents of twins with reading difficulties.

Parents of 323 twin pairs with reading disability (RD) reported significantly more problems learning to read (16% of mothers and 33% of fathers) than parents of 309 twin pairs without reading difficulties (6% of mothers and 9% of fathers). These rates of self-reported reading problems in parents of twins are highly similar to those previously obtained in parents of non-twin children with RD and controls, suggesting that the etiology of reading deficits in twin and non-twin children may also be highly similar. Moreover, within both the RD and control samples, twins whose parents self-reported a positive history of reading problems had lower reading performance test scores, on average, than those whose parents reported no reading problems. Therefore, results of the present twin study support those of previous studies with non-twin children in which parental self-reports have been found to provide a valid index of family history status for reading difficulties.     

Peers, teachers and parents as assessors of the behavioural and emotional problems of twins and their adjustment: the Multidimensional Peer Nomination Inventory.

A multidimensional peer nomination inventory (MPNI; 30 items) and parallel versions--MPNI-Teacher and MPNI-Parental Rating Forms (37 items each)--were developed during a major new Finnish study of families with twins. The twins (477 girls and 467 boys) were 12 years old, representing subsets of three nationwide Finnish twin cohorts (b. 1983-1985). They were enrolled in 503 school classes, and the total number of children participating in peer nominations was 12,937. Three main factors were extracted from peer nominations and teacher and parental assessments. Intercorrelating sub-components were found, especially in parental assessments. Scales were formed, accordingly, for Behavioral Problems (including Hyperactivity-Impulsivity, Aggression, and Inattention), Emotional Problems (including Depression and Social Anxiety), and Adjustment (including Constructiveness, Compliance, and Social Activity). A framework for the development of the multidimensional inventory was a model of emotional and behavioural regulation. Peer nominations were most reliable, while parental assessments, although mostly satisfactory, were least reliable. Results provided evidence of concurrent validity of peer-referenced assessment, using teacher assessments as criteria; correlations between assessments of peers and parents were lower. The inventory has discriminative validity. Intra-pair correlations of monozygotic co-twins were higher than correlations of same-sex (SS) and opposite-sex (OS) dizygotic (DZ) co-twins for all scales across all three assessors, and peer nominations of both SS and OSDZ co-twins yielded correlations significantly greater than zero for all scales. All scales, except Depression and Social Anxiety, differentiated boys from girls.     

Feelings and the need for information and counselling of expectant parents of twins.

In this study, expectant parents of twins were questioned about their feelings and need for information and counselling on the parenting of twins. Data were obtained from self-rating questionnaires and an interview with the expectant mother. From the results it is argued that expectant parents of twins need specific information and counselling about the medical, emotional and parenting issues of having twins. Guidelines for organising this counselling are proposed.     

Special twin environments, genetic influences and their effects on the handedness of twins and their siblings.

It has been suggested that twinning may influence handedness through the effects of birth order, intra-uterine crowding and mirror imaging. The influence of these effects on handedness (for writing and throwing) was examined in 3657 Monozygotic (MZ) and 3762 Dizygotic (DZ) twin pairs (born 1893-1992). Maximum likelihood analyses revealed no effects of birth order on the incidence of left-handedness. Twins were no more likely to be left-handed than their singleton siblings (n = 1757), and there were no differences between the DZ co-twin and sibling-twin covariances, suggesting that neither intra-uterine crowding nor the experience of being a twin affects handedness. There was no evidence of mirror imaging; the co-twin correlations of monochorionic and dichorionic MZ twins did not differ. Univariate genetic analyses revealed common environmental factors to be the most parsimonious explanation of familial aggregation for the writing-hand measure, while additive genetic influences provided a better interpretation of the throwing hand data.     

Why zygosity of multiple births is not always obvious: an examination of zygosity testing requests from twins or their parents.

This paper examines why parents of twins or adult twins themselves request zygosity testing. Of 405 multiples including 8 sets of triplets, the majority (93%) were monozygotic. Age of testing ranged from 0 days to 73 years. About 50% of requests came from parents or twins who were curious about, or expressed a need to be certain of, their zygosity. Other reasons included health concerns (current or future), other twins in the family, and misinformation about zygosity, frequently because of the erroneous assumption that all dichorionic twins are dizygotic. Parents of monozygotic twins may expect their twins to be 'identical' and believe their twins to be dizygotic because of minor phenotypic differences between them. Dizygotic twins like other siblings may share a phenotypic resemblance. Health professionals should be aware that zygosity of multiples may not always be obvious to parents and that accurate knowledge of zygosity may be justified.     

Assortative mating for anthropometric traits in parents of Punjabi twins

The marital correlations between 97 pairs of parents of Punjabi twins reveal positive phenotypic assortative mating for body traits while almost random mating with respect to cranio-facial traits. There is no evidence of any significant negative assortative mating for any of the 50 traits. The results have been compared with those from other world populations. The data contradict the earlier reported hypothesis that assortative mating is associated with lowered fertility.     

Reliability and stability of mothers' reports about their pregnancies with twins.

The objective of this study was to determine if mothers' retrospective reports about events in their pregnancies with twins are reliable and stable. Six hundred and twenty-four mothers completed psychiatric interviews about their twins. These interviews also contained questions about the mothers' pregnancies, the perinatal period, and the child's early development. The mothers reported first on one twin and then on the other with interviews spaced from 3 days to 2 weeks apart. Thus mothers reported on the same pregnancy twice. Of these mothers, 47 were re-interviewed 6 to 18 months later by raters blind to the results of the initial interview. The twin design allowed us to compare the short-term reliability of the 624 mothers' reports of the same pregnancy. The re-interview of the 47 mothers enabled us to compare the stability of reports over a longer time period. Agreement between the reports was measured with the kappa statistic. Kappas were good to excellent for the short-term reports of pregnancy for each twin for the 624 mothers. Kappas were equally high for the 47 mothers that were re-interviewed 6 to 18 months later. Mothers show good reliability and stability of reporting about events during pregnancy.