Project description:Gametic selection during fertilization or the effects of specific genotypes on the viability of embryos may cause a skewed transmission of chromosomes to surviving offspring. A recent analysis of transmission distortion in humans reported significant excess sharing among full siblings. Dizygotic (DZ) twin pairs are a special case of the simultaneous survival of two genotypes, and there have been reports of DZ pairs with excess allele sharing around the HLA locus, a candidate locus for embryo survival. We performed an allele-sharing study of 1,592 DZ twin pairs from two independent Australian cohorts, of which 1,561 pairs were informative for linkage on chromosome 6. We also analyzed allele sharing in 336 DZ twin pairs from The Netherlands. We found no evidence of excess allele sharing, either at the HLA locus or in the rest of the genome. In contrast, we found evidence of a small but significant (P=.003 for the Australian sample) genomewide deficit in the proportion of two alleles shared identical by descent among DZ twin pairs. We reconciled conflicting evidence in the literature for excess genomewide allele sharing by performing a simulation study that shows how undetected genotyping errors can lead to an apparent deficit or excess of allele sharing among sibling pairs, dependent on whether parental genotypes are known. Our results imply that gene-mapping studies based on affected sibling pairs that include DZ pairs will not suffer from false-positive results due to loci involved in embryo survival.
Project description:Monochorionic twins are usually monozygotic and thus usually have the same sex. A case of monochorionic diamniotic twins following IVF/ICSI and laser treatment of the zona pellucida ("assisted hatching") is presented in which partial embryo amalgamation appears to have occurred. Discordant sex between the twins was suspected on detailed antenatal ultrasound at 13 + 3 weeks gestation and was confirmed on subsequent examinations. The sexual phenotype at birth was female for one twin and male for the other. Placental histology confirmed the monochorionic, diamniotic situation. Cytogenetic analysis of both twins was carried out postpartum on various tissues. On karyotyping of blood lymphocytes the male and female twins each had one mosaic of male and female cells. Oral mucosal cells showed normal male and female karyotypes respectively. Analysis of urothelium showed a normal result for the male infant, and a weak gonosomal mosaic with an XX and XY constellation for the female infant. At least for blood lymphocytes, a diagnosis of chimerism was proven.
Project description:BackgroundThe tendency to conceive dizygotic (DZ) twins is a complex trait influenced by genetic and environmental factors. To search for new candidate loci for twinning, we conducted a genome-wide linkage scan in 525 families using microsatellite and single nucleotide polymorphism marker panels.Methods and resultsNon-parametric linkage analyses, including 523 families containing a total of 1115 mothers of DZ twins (MODZT) from Australia and New Zealand (ANZ) and The Netherlands (NL), produced four linkage peaks above the threshold for suggestive linkage, including a highly suggestive peak at the extreme telomeric end of chromosome 6 with an exponential logarithm of odds [(exp)LOD] score of 2.813 (P = 0.0002). Since the DZ twinning rate increases steeply with maternal age independent of genetic effects, we also investigated linkage including only families where at least one MODZT gave birth to her first set of twins before the age of 30. These analyses produced a maximum expLOD score of 2.718 (P = 0.0002), largely due to linkage signal from the ANZ cohort, however, ordered subset analyses indicated this result is most likely a chance finding in the combined dataset. Linkage analyses were also performed for two large DZ twinning families from the USA, one of which produced a peak on chromosome 2 in the region of two potential candidate genes. Sequencing of FSHR and FIGLA, along with INHBB in MODZTs from two large NL families with family specific linkage peaks directly over this gene, revealed a potentially functional variant in the 5' untranslated region of FSHR that segregated with the DZ twinning phenotype in the Utah family.ConclusionOur data provide further evidence for complex inheritance of familial DZ twinning.
Project description:Monochorionic twins are generally considered to be monozygotic, as monochorionic dizygotic (MCDZ) twins are extremely rare in natural pregnancies. Several studies have reported this rare occurrence, and most of these pregnancies have been conceived by assisted reproductive technology (ART). These reports mostly focused on MCDZ twin pregnancies and the childhood development of the twins; a follow-up into adulthood and the effect on their reproduction has not been reported. In this case study, we report a case of chimerism in opposite-sex MCDZ twins who were naturally conceived and have reached reproductive maturity. We collected oral mucosal, endometrial, and germ cells from the twins and evaluated their chimerism using single-nucleotide polymorphism (SNP) array and droplet digital PCR (ddPCR). The SNP array showed that they had 4,049 non-allele shared loci, and they inherited nearly 50% informative SNP loci from each parent, confirming that they are dizygotic twins. We found that the female twin had a 46, XX (2)/46, XY (78) karyotype in her peripheral blood. The SNP array confirmed that the female twin and male twin had the same blood haplotype. The ddPCR result showed 92.84 (± 1.80%) chimerism in her blood. In case of chimerism in her germline, the female twin chose preimplantation genetic testing for aneuploidy for her blastocysts. Fortunately, the patient only had blood chimerism. A healthy boy was born at 39 weeks of gestation.
Project description:BackgroundCardiac rhabdomyoma (RHM) is considered one of the most frequent benign heart tumors in children. However, encounters with cardiac RHM in clinical practice remain rare. Clinical information is primarily available in the form of single case reports or smaller studies with a shortage of large-scale reviews encompassing a substantial number of cases.ResultsIn order to congregate existing and future information on cardiac RHM we established a web-based cardiac RHM online registry using an online survey tool. In addition we integrated previously published data from individual case reports and case series. The evaluation of this paper is intended to provide a brief overview of the cohort that we have been able to include so far. Our findings mainly confirm the previous knowledge on cardiac RHM. At the same time, our cohort shows a clear heterogeneity in the treatment methods with regard to rhabdomyomas requiring therapy and revealed a bias between literature data and our registry data with regard to symptoms and need for therapy.ConclusionIn the view of the heterogeneity of treatment methods, a systematic overview of cardiac RHM is all the more important, especially as specific drug treatment options now exist. The registry should not just provide a comprehensive and informative overview of causes, time course, symptoms and therapeutic options of cardiac RHM but also facilitate information sharing among clinicians and researchers and serve as a basis for future clinical and pharmacological studies.
Project description:BackgroundMonochorionic dizygotic twins are a rare condition, mostly related to assisted reproductive technology. This type of twinning is burdened by the same risk of pregnancy complications found in monochorionic monozygotic pregnancies.Case presentationWe report a case of spontaneous monochorionic dizygotic twins sharing situs inversus abdominalis and isolated levocardia, with only one twin affected by biliary atresia with splenic malformation syndrome. We also conducted a literature review of the 14 available documented monochorionic dizygotic twin gestations spontaneously conceived.ConclusionsIt is still unclear how this unusual type of twinning can occur in spontaneous conception. The evidence so far suggest the importance to timely diagnose the chorionicity, in order to adequately manage the typical complications associated with monochorionicity.
Project description:Nuclear receptor subfamily 5, group A, member 1 (NR5A1) is a nuclear receptor involved in gonadal and adrenal development. We identified a novel C-terminally truncating NR5A1 mutation, p.Leu423Trpfs*7, in dizygotic twins with 46,XY disorders of sex development. Our results highlight the functional importance of C-terminal region of NR5A1 and indicate that NR5A1 mutations can be associated with intrafamilial phenotypic variations, progressive testicular dysfunction, hypogonadotropic hypogonadism, and borderline adrenal dysfunction.
Project description:ImportanceLow birth weight is associated with an increased likelihood of neurodivergence and neurodevelopmental conditions (NDCs) such as autism, attention-deficit/hyperactivity disorder (ADHD), and intellectual disability. However, it is unclear whether birth weight contributes independently to NDCs or whether the association is predominantly driven by genetic predisposition.ObjectiveTo estimate the associations between birth weight and dimensional (trait) and categorical (diagnoses) NDC outcomes, while adjusting for genetic risks.Design, setting, and participantsA co-twin design was applied to this case-control study conducted in Sweden. Diagnostic assessments were conducted between August 2011 and March 2022, within the Roots of Autism and ADHD Twin Study in Sweden (RATSS) during a 2.5-day participant visit to the clinic. The RATSS sample comprised phenotyped monozygotic and dizygotic twins enriched for NDCs. Data analysis was conducted in November 2022.ExposureBirth weight.Main outcomes and measuresCategorical and dimensional operationalizations of autism, ADHD, and intellectual disability were assessed. Generalized estimating equation models were fitted across and within twin pairs.ResultsThe study sample included 393 twins: 230 were monozygotic and 159 were dizygotic (zygosity was unknown for 4). Their median age was 15 (range, 8-37) years. There were 185 female participants (47.1%) and 208 male participants (52.9%). Across twin pairs, higher birth weight was associated with fewer autistic traits (unstandardized β [B], -5.51 [95% CI, -10.09 to -0.94]) and lower odds of autism diagnosis (OR, 0.63 [95% CI, 0.45 to 0.88]) and intellectual disability (OR, 0.42 [95% CI, 0.19 to 0.92]). Within pairs, the association between birth weight and dimensional autism (B, -17.35 [95% CI, -28.66 to -6.04]) and categorical autism (OR, 0.02 [95% CI, 0.001 to 0.42]) remained among monozygotic pairs but not dizygotic pairs. In addition, higher birth weight was associated with lower odds of ADHD diagnosis (OR, 0.003 [95% CI, 0 to 0.70]), fewer ADHD traits (B, -0.25 [95% CI, -0.39 to -0.11]), and higher IQ ratings (B, 7.43 [95% CI, 1.05 to 13.82]) among monozygotic twins.Conclusions and relevanceThe findings of this co-twin study suggest an association between low birth weight and NDCs, but they also acknowledge the importance of genetics because the associations observed were only statically significant among monozygotic twins. It is of pivotal importance to facilitate early identification of factors contributing to fetal growth restriction to minimize detrimental outcomes.
Project description:Using the Infinium HM450 platform, we have performed a longitudinal study of DNA methylation at birth and age 18 months in DNA from buccal swabs from 10 monozygotic (MZ) and 5 dizygotic (DZ) twin pairs from the Peri/postnatal Epigenetic Twins Study (PETS) cohort.