Twisting the theory on the origin of human umbilical cord coiling featuring monozygotic twins.

The human umbilical cord (hUC) is the lifeline that connects the fetus to the mother. Hypercoiling of the hUC is associated with pre- and perinatal morbidity and mortality. We investigated the origin of hUC hypercoiling using state-of-the-art imaging and omics approaches. Macroscopic inspection of the hUC revealed the helices to originate from the arteries rather than other components of the hUC. Digital reconstruction of the hUC arteries showed the dynamic alignment of two layers of muscle fibers in the tunica media aligning in opposing directions. We observed that genetically identical twins can be discordant for hUC coiling, excluding genetic, many environmental, and parental origins of hUC coiling. Comparing the transcriptomic and DNA methylation profile of the hUC arteries of four twin pairs with discordant cord coiling, we detected 28 differentially expressed genes, but no differentially methylated CpGs. These genes play a role in vascular development, cell-cell interaction, and axis formation and may account for the increased number of hUC helices. When combined, our results provide a novel framework to understand the origin of hUC helices in fetal development.

Commentary: Assortative parenting and assortative cross-parenting: New views of parental preference for selected children.

The commentary delves into the implications of "assortative parenting" and "assortative cross-parenting," as introduced by N. L. Segal, and situates these concepts within the framework of current research. It addresses the joys and complexities of raising twins, highlighting how their concurrent development stages can amplify parental favoritism and heighten the challenge of addressing each twin's unique needs. This interplay provides a rich context to investigate assortative parenting practices. Additionally, this paper contemplates the broader picture of twin studies, particularly how the care of monozygotic twins (who share 100 % of their genes) and dizygotic twins (who share 50 % of their genes, on average) may reveal the intertwined nature of genetics and environment in parenting strategies. It also proposes that twins' interactions with other family members, their spouses, and peers can offer profound insights into the phenomena of phenotypic assortative affiliation, enriching our understanding of close relational bonds.

The Population-Based Hungarian Twin Registry: An Update.

Between 2006 and 2021, the Hungarian Twin Registry (HTR) operated a volunteer twin registry of all age groups (50% monozygotic [MZ], 50% dizygotic [DZ], 70% female, average age 34 ± 22 years), including 1044 twin pairs, 24 triplets and one quadruplet set. In 2021, the HTR transformed from a volunteer registry into a population-based one, and it was established in the Medical Imaging Centre of Semmelweis University in Budapest. Semmelweis University's innovation fund supported the development of information technology, a phone bank and voicemail infrastructure, administrative materials, and a new website was established where twins and their relatives (parent, foster parent or caregiver) can register. The HTR's biobank was also established: 157,751 individuals with a likely twin-sibling living in Hungary (77,042 twins, 1194 triplets, 20 quadruplets, and one quintuplet) were contacted between February and March of 2021 via sealed letters. Until November 20, 2022, 12,001 twin individuals and their parents or guardians (6724 adult twins, 3009 parents/guardians and 5277 minor twins) registered, mostly online. Based on simple self-reports, 37.6% of the registered adults were MZ twins and 56.8% were DZ; 1.12% were triplets and 4.5% were unidentified. Of the registered children, 22.3% were MZ, 72.7% were DZ, 1.93% were triplets, and 3.05% were unidentified. Of the registered twins, 59.9% were female (including both the adult and minor twins). The registration questionnaire consists of eight parts, including socio-demographic and anthropometric data, smoking habits and medical questions (diseases, operations, therapies). Hungary's twin registry has become the sole and largest population-based twin registry in Central Eastern Europe. This new resource will facilitate performing world-class modern genetic research.

Complex genotype-phenotype correlation of MYH11: new insights from monozygotic twins with highly variable expressivity and outcomes.

BACKGROUND: Thoracic aortic aneurysm/dissection (TAAD) and patent ductus arteriosus (PDA) are serious autosomal-dominant diseases affecting the cardiovascular system. They are mainly caused by variants in the MYH11 gene, which encodes the heavy chain of myosin 11. The aim of this study was to evaluate the genotype-phenotype correlation of MYH11 from a distinctive perspective based on a pair of monozygotic twins. METHODS: The detailed phenotypic characteristics of the monozygotic twins from the early fetal stage to the infancy stage were traced and compared with each other and with those of previously documented cases. Whole-exome and Sanger sequencing techniques were used to identify and validate the candidate variants, facilitating the analysis of the genotype-phenotype correlation of MYH11. RESULTS: The monozygotic twins were premature and presented with PDA, pulmonary hypoplasia, and pulmonary hypertension. The proband developed heart and brain abnormalities during the fetal stage and died at 18 days after birth, whereas his sibling was discharged after being cured and developed normally post follow-up. A novel variant c.766 A > G p. (Ile256Val) in MYH11 (NM_002474.2) was identified in the monozygotic twins and classified as a likely pathogenic variant according to the American College of Medical Genetics/Association for Molecular Pathology guidelines. Reviewing the reported cases (n = 102) showed that the penetrance of MYH11 was 82.35%, and the most common feature was TAAD (41.18%), followed by PDA (22.55%), compound TAAD and PDA (9.80%), and other vascular abnormalities (8.82%). The constituent ratios of null variants among the cases with TAAD (8.60%), PDA (43.8%), or compound TAAD and PDA (28.6%) were significantly different (P = 0.01). Further pairwise comparison of the ratios among these groups showed that there were significant differences between the TAAD and PDA groups (P = 0.006). CONCLUSION: This study expands the mutational spectrum of MYH11 and provides new insights into the genotype-phenotype correlation of MYH11 based on the monozygotic twins with variable clinical features and outcomes, indicating that cryptic modifiers and complex mechanisms beside the genetic variants may be involved in the condition.

Short report: Twins with 20p13 duplication. Case report and comprehensive literature review.

BACKGROUND: Trisomy 20p is a rare genetic condition caused by a duplication of the short arm of chromosome 20. METHODS: We employed clinical observation and molecular genetic testing (SNP microarray), to study identical twin males with an unknown dysmorphic syndrome. We conducted a literature review of trisomy 20p and collated the clinical and molecular genetic findings on 20 affected subjects reported since 2000. RESULTS: Identical twin males, whose prenatal course was complicated by a twin-to-twin transfusion, manifested profound language and neurocognitive delays as well as distinctive facial dysmorphisms when evaluated at 2 years of age. SNP microarray identified identical duplications of 20p13 with no other chromosomal aberrations. A literature survey of 20p trisomy syndrome identified 20 other examples of this condition reported since 2000, which we collated with 33 summarized by Sidwell et al. (2000). Within the combined total of 55 affected individuals, we found a distinctive clinical phenotype that provides insight on the effects of abnormal dosage of genes in 20p13. These loci include FAM110A (OMIM 611393), ANGPT4 (OMIM 603705), RSPO4 (OMIM 610573), PSMF1 (OMIM 617858), SNPH (OMIM 604942), SDCBP2 (OMIM 617358), FKBP1A (OMIM 186945), TMEM74B, C20orf202, and RAD21L1 (OMIM 619533). Gene profiling highlighted that syntaphilin (SNPH) is highly expressed in mammalian brain, where it is considered critical for mitochondrial transport in neuronal axons, and to directly influence axonal morphogenesis and function. CONCLUSION: We propose that abnormal activity of syntaphilin engendered by the trisomy is primarily responsible for the language, neurocognitive, and gross motor delays reported in individuals with 20p trisomy. Additional studies, for example, characterization of cerebral organoids generated from affected patients may help to better understand this condition, and potentially suggest rational remedies to improve the lives of affected individuals and their families.

TwinsMX: Exploring the Genetic and Environmental Influences on Health Traits in the Mexican Population.

TwinsMX registry is a national research initiative in Mexico that aims to understand the complex interplay between genetics and environment in shaping physical and mental health traits among the country's population. With a multidisciplinary approach, TwinsMX aims to advance our knowledge of the genetic and environmental mechanisms underlying ethnic variations in complex traits and diseases, including behavioral, psychometric, anthropometric, metabolic, cardiovascular and mental disorders. With information gathered from over 2800 twins, this article updates the prevalence of several complex traits; and describes the advances and novel ideas we have implemented such as magnetic resonance imaging. The future expansion of the TwinsMX registry will enhance our comprehension of the intricate interplay between genetics and environment in shaping health and disease in the Mexican population. Overall, this report describes the progress in the building of a solid database that will allow the study of complex traits in the Mexican population, valuable not only for our consortium, but also for the worldwide scientific community, by providing new insights of understudied genetically admixed populations.

Heritability of Gene Expression Measured from Peripheral Blood in Older Adults.

The contributions of genetic variation and the environment to gene expression may change across the lifespan. However, few studies have investigated the heritability of blood gene expression in older adults. The current study therefore aimed to investigate this question in a community sample of older adults. A total of 246 adults (71 MZ and 52 DZ twins, 69.91% females; mean age-75.79 ± 5.44) were studied. Peripheral blood gene expression was assessed using Illumina microarrays. A heritability analysis was performed using structural equation modelling. There were 5269 probes (19.9%) from 4603 unique genes (23.9%) (total 26,537 probes from 19,256 genes) that were significantly heritable (mean h2 = 0.40). A pathway analysis of the top 10% of significant genes showed enrichment for the immune response and ageing-associated genes. In a comparison with two other gene expression twin heritability studies using adults from across the lifespan, there were 38 out of 9479 overlapping genes that were significantly heritable. In conclusion, our study found ~24% of the available genes for analysis were heritable in older adults, with only a small number common across studies that used samples from across adulthood, indicating the importance of examining gene expression in older age groups.

Heritability of Clinically Diagnosed Obsessive-Compulsive Disorder Among Twins.

This cohort study estimates the heritability of clinically diagnosed obsessive-compulsive disorder in a sample of twins.

Tissue-specific nonheritable influences drive endometrial immune system variation.

Although human twin studies have revealed the combined contribution of heritable and environmental factors in shaping immune system variability in blood, the contribution of these factors to immune system variability in tissues remains unexplored. The human uterus undergoes constant regeneration and is exposed to distinct environmental factors. To assess uterine immune system variation, we performed a system-level analysis of endometrial and peripheral blood immune cells in monozygotic twins. Although most immune cell phenotypes in peripheral blood showed high genetic heritability, more variation was found in endometrial immune cells, indicating a stronger influence by environmental factors. Cytomegalovirus infection was identified to influence peripheral blood immune cell variability but had limited effect on endometrial immune cells. Instead, hormonal contraception shaped the local endometrial milieu and immune cell composition with minor influence on the systemic immune system. These results highlight that the magnitude of human immune system variation and factors influencing it can be tissue specific.

Exploring Hematological and Biochemical Disparities in Same-Sex and Opposite-Sex Females: A Cross-Sectional Twin Study in a Ghanaian Population.

There are sex-dependent differences in hematological and biochemical variables in adulthood attributed to the predominant effects of testosterone in males and estrogen in females. The Twin Testosterone Transfer (TTT) hypothesis proposes that opposite-sex females may develop male-typical traits due to exposure to relatively higher levels of prenatal testosterone than same-sex females. Additionally, prenatal testosterone exposure has been suggested as a correlate of current circulating testosterone levels. Consequently, opposite-sex females might exhibit male-typical patterns in their hematological and biochemical variables. Despite this hypothesis, routine laboratory investigations assign the same reference range to all females. Our cross-sectional study, conducted in Tamale from January to September 2022, included 40 twins, comprising 10 opposite-sex (OS) males (25%), 10 OS females (25%), and 20 same-sex (SS) females (50%), all aged between 18 and 27 years. Fasting venous blood samples were collected and analyzed using automated hematology and biochemistry laboratory analyzers. Results indicated that levels of hemoglobin, serum creatinine, gamma-glutamyl transferase, total protein, globulins, and total testosterone were significantly higher in OS males than OS females. Conversely, total cholesterol and low-density lipoprotein cholesterol were significantly higher in OS females than OS males. Unexpectedly, levels of low-density lipoprotein cholesterol and total testosterone were significantly higher in SS females than OS females. Contrary to expectations, opposite-sex females did not exhibit male-typical patterns in their hematological and biochemical variables. This suggests that the TTT effect may not occur or may not be strong enough to markedly affect hematological and biochemical variables in OS females.

Common genetic factors for uncontrolled eating mechanisms.

OBJECTIVE: Reward-based eating drives are putative mechanisms of uncontrolled eating implicated in obesity and disordered eating (e.g., binge eating). Uncovering the genetic and environmental contributions to reward-related eating, and their genetic correlation with BMI, could shed light on key mechanisms underlying eating and weight-related disorders. METHOD: We conducted a classical twin study to examine how much variance in uncontrolled eating phenotypes and body mass index (BMI) was explained by genetic factors, and the extent that these phenotypes shared common genetic factors. 353 monozygotic twins and 128 dizygotic twins completed the Reward-based Eating Drive 13 scale, which measures three distinct uncontrolled eating phenotypes (loss of control over eating, preoccupation with thoughts about food, and lack of satiety), and a demographic questionnaire which included height and weight for BMI calculation. We estimated additive genetic (A), common environmental (C), and unique environmental (E) factors for each phenotype, as well as their genetic correlations, with a multivariate ACE model. A common pathway model also estimated whether genetic variance in the uncontrolled eating phenotypes was better explained by a common latent uncontrolled eating factor. RESULTS: There were moderate genetic correlations between uncontrolled eating phenotypes and BMI (.26-.41). Variance from the uncontrolled eating phenotypes was also best explained by a common latent uncontrolled eating factor that was explained by additive genetic factors (52%). DISCUSSION: These results suggest that uncontrolled eating phenotypes are heritable traits that also share genetic variance with BMI. This has implications for understanding the cognitive mechanisms that underpin obesity and disordered eating. PUBLIC SIGNIFICANCE: Our study clarifies the degree to which uncontrolled eating phenotypes and BMI are influenced by shared genetics and shows that vulnerability to uncontrolled eating traits is impacted by common genetic factors.

Can flow proneness be protective against mental and cardiovascular health problems? A genetically informed prospective cohort study.

Flow is a phenomenon where one experiences optimal challenge, marked by an intense, effortless, and rewarding concentration on a task. Past research shows that flow proneness is associated with good mental and cardiovascular health. However, this research has been primarily cross-sectional, based on self-report data, and has not controlled for potential confounding effects of neuroticism. In a large, longitudinal twin sample (N = 9361), we used nationwide patient registry data to test whether flow proneness predicted registry-based diagnoses of depression, anxiety, schizophrenia, bipolar disorder, stress-related disorders, or cardiovascular diseases. We used survival analyses taking time to diagnosis into account to test if (a) there is a relationship between flow proneness and health diagnoses over time, (b) neuroticism confounds this relationship, and (c) the relationship remains present within discordant monozygotic twin pairs (N = 952), thereby controlling for genetic and shared environmental confounding. Individuals with higher flow proneness had a decreased risk of receiving diagnoses for depression (16%; CI [14%, 18%]), anxiety (16%; CI [13%, 18%]), schizophrenia (15%; CI [4%, 25%]), bipolar (12%; CI [6%, 18%]), stress-related (9%; CI [9%, 12%]), and cardiovascular disorders (4%; CI [1%, 8%]). When controlling for neuroticism, higher flow proneness still decreased the risk of depression (6%; CI [3%, 9%]) and anxiety diagnoses (5%; CI [1%, 8%]). Monozygotic twins who experienced more flow than their co-twin had a lower risk for depression (16%; CI [5%, 26%]) and anxiety (13%; CI [1%, 24%]), though only the association with depression remained significant when also controlling for neuroticism (13%; CI [1%, 24%]). Findings are in line with a causal protective role of flow experiences on depression and potentially anxiety and highlight that neuroticism and familial factors are notable confounding factors in observed associations between flow proneness and health outcomes.

[What "look-alike" individuals tell us]. / Sous le capot des sosies.

Rare unrelated individuals show striking resemblance, almost as high as monozygotic twins. Extensive genetic analysis of a set of such individuals shows that every couple shares a given allele at a large set of loci, enriched for "face genes". The similarity is limited to this set of loci, and the rest of the genome is quite diverse in these "look alike" individuals.

Peculiar CADASIL phenotype in monozygotic twins carrying a novel NOTCH3 pathogenetic variant.

BACKGROUND: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an autosomal dominantly inherited cerebral small vessel disease caused by Neurogenic locus notch homolog protein 3 (NOTCH3) gene mutations. The main clinical features include migraine with aura, recurrent ischemic strokes and dementia. Brain MRI typically shows multiple small lacunar infarcts and severe, diffuse, symmetrical white matter hyperintensities (WMHs), with characteristic involvement of the anterior temporal pole, external capsule, and superior frontal gyrus. Reports of twins with CADASIL are scarce. Herein we describe a pair of monozygotic twins with peculiar CADASIL phenotype, carrying a new NOTCH3 variant. CASE PRESENTATION: Twin A was a 45-year-old male suffering from migraine, obesity, arterial hypertension, and polycythemia (with negative genetic analysis), who complained of a transient, short-lasting (~ 5 minutes) episode of speech difficulties. Brain MRI showed diffuse, symmetrical, confluent periventricular WMHs involving frontal, parietal, and temporal lobes and external capsules, with sparing of anterior temporal poles. Genetic analysis of NOTCH3 gene demonstrated the presence of missense c.3329G>A, p.(Cys1110Tyr) variant, confirming CADASIL diagnosis. Twin B, affected by migraine and polycythemia, as well as his monozygotic twin, presented with a 2-month history of trigeminal neuralgia. Brain MRI demonstrated diffuse WMHs with a pattern of distribution like his twin. Genetic analysis revealed the same NOTCH3 pathogenic variant. CONCLUSIONS: Our monozygotic twins have a strikingly similar neuroimaging picture with sparing of anterior temporal poles. They also have a peculiar phenotype, both presenting polycythemia without genetically confirmed cause. Twin B had trigeminal neuralgia, that is unusual in CADASIL. The possible association of the peculiar findings with the newly reported NOTCH3 variant needs to be confirmed with further observations.

Twin studies as an innovative approach to address research questions in cancer care within primary care settings.

This paper proposes the utilisation of twin studies as a novel and powerful methodological approach to investigate critical research questions pertaining to cancer prevention, screening, diagnosis, treatment and survivorship within primary care contexts. The inherent genetic similarity between monozygotic (MZ) (identical) twins provides a unique opportunity to disentangle genetic and environmental influences on cancer-related outcomes. MZ twins share virtually identical genetic makeup, offering a unique opportunity to discern the relative contributions of genetic and environmental factors to cancer-related outcomes. In contrast, dizygotic (DZ) twins, also known as fraternal twins, develop from two separate eggs fertilised by two different sperm and share on average 50% of their genetic material, the same level of genetic similarity found in non-twin siblings. Comparisons between MZ and DZ twins enable researchers to disentangle hereditary factors from shared environmental influences. This methodology has the potential to advance our understanding of the multifaceted interplay between genetic predisposition, lifestyle factors and healthcare interventions in the context of cancer care. This paper outlines the rationale, design considerations and potential applications of twin studies in primary care-based cancer research.

Differential methylation patterns from clusters associated with glucose metabolism: evidence from a Shanghai twin study.

Aim: To assess the associations between genome-wide DNA methylation (DNAm) and glucose metabolism among a Chinese population, in particular the multisite correlation. Materials & methods: Epigenome-wide associations with fasting plasma glucose (FPG) and hemoglobin A1c (HbA1c) were analyzed among 100 Shanghai monozygotic (MZ) twin pairs using the Infinium HumanMethylationEPIC v2.0 BeadChip. We conducted a Pearson's correlation test, hierarchical cluster and pairwise analysis to examine the differential methylation patterns from clusters. Results: Cg01358804 (TXNIP) was identified as the most significant site associated with FPG and HbA1c. Two clusters with hypermethylated and hypomethylated patterns were observed for both FPG and HbA1c. Conclusion: Differential methylation patterns from clusters may provide new clues for epigenetic changes and biological mechanisms in glucose metabolism.

Partnership with the University of São Paulo Panel of Twins: A Four-City Tour and More / Twin Research Reviews: Twin Research on Binge Eating; Twins' Physical Outcomes Linked to Different Diets; Working Conditions and Sickness Absence in Swedish Twins; Facial Morphology Differences in Monozygotic Twins / Human Interest and Importance: Michigan Family Forced to Adopt Their Own Twins; Ethics of Hiring a Surrogate to Bear Twins; Twin Survivors of the Israel-Hamas War; Twin Pregnancy with Double Uterus; Three Twin Pairs on Same Women's Soccer Team.

This article begins with an overview of twin research in Brazil, initiated by the University of São Paulo Panel of Twins. I met with many new research collaborators and students while on a fall 2023 four-city lecture tour in that country. A meeting with a world-famous surgeon who recently separated craniopagus conjoined twin pairs is also described. This overview is followed by summaries of twin research on binge eating, twins' physical outcomes linked to different diets, working conditions and sickness absence in Swedish Twins and facial morphology differences in monozygotic twins. The final section of this article provides a sampling of human interest stories with important implications. They include a Michigan family forced to adopt their own twins, ethical issues surrounding the hiring of a surrogate to bear twins; twin survivors of the Israel-Hamas war, a twin pregnancy with a double uterus, and three twin pairs on the same women's soccer team.

A late-life neurogenetic signature of exposure to combat stress - A monozygotic discordant twin study.

Animal models suggest that experiencing high-stress levels induces changes in amygdalar circuitry and gene expression. In humans, combat exposure has been shown to alter amygdalar responsivity and connectivity, but abnormalities have been indicated to normalize at least partially upon the termination of stress exposure. In contrast, other evidence suggests that combat exposure continues to exert influence on exposed individuals well beyond deployment and homecoming, as indicated by longitudinal psychosocial evidence from veterans, and observation of greater health decline in veterans late in life. Accordingly, the experience of combat stress early in life may affect amygdalar responsivity late in life, a possibility requiring careful consideration of the confounding effects of aging, genetic factors, and symptoms of post-traumatic stress disorder. Here, we investigated amygdalar responsivity in a unique sample of 16 male monozygotic (MZ) twin pairs in their sixties, where one but not the other sibling had been exposed to combat stress in early adulthood. Forty years after combat experience, a generally blunted amygdalar response was observed in combat-exposed veterans compared to their non-exposed twin siblings. Spatial associations between these phenotypical changes and patterns of gene expression in the brain were found for genes involved in the synaptic organization and chromatin structure. Protein-protein interactions among the set of identified genes pointed to histone modification mechanisms. We conclude that exposure to combat stress early in life continues to impact brain function beyond the termination of acute stress and appears to exert prolonged effects on amygdalar function later in life via neurogenetic mechanisms.

Bilateral Peters' anomaly, aniridia and Wilms tumour (WAGR syndrome) in monozygotic twins.

AIM: This study reports the bilateral association of Peters' anomaly and congenital aniridia in monozygotic twins subsequently diagnosed with Wilms tumour (WAGR syndrome). METHODS: Two monozygotic female twins were referred at age 2 months with bilateral corneal opacity. A diagnosis of Peters' anomaly associated to aniridia was made in both eyes of both twins. Physical examination and ultrasonography were carried out at 12 months of age to explore the possibility of WAGR-related anomalies, specifically Wilms tumour. DNA were isolated and subjected to whole exome sequencing. RESULTS: Peters' anomaly associated to aniridia in both eyes as well as bilateral Wilms tumour in both children were diagnosed. Exome analyses showed a large heterozygous deletion encompassing 6 648 473 bp in chromosome 11p13, using Integrative Genomics Viewer and AnnotSV software. CONCLUSION: WAGR syndrome is a rare contiguous gene deletion syndrome with a greater risk of developing Wilms tumour associated with Peters' anomaly and congenital aniridia. However, co-occurrence of both anomalies was rarely reported in twins, and never in both eyes of monozygotic twins. Here, we report the bilateral association of Peters' anomaly and congenital aniridia in monozygotic twins with WAGR syndrome.