Are thyrogastric autoantibodies associated with an increased susceptibility to developing type 1 (insulin-dependent) diabetes? A study in identical twins

To examine whether the presence of thyrogastric autoantibodies is associated with an increased susceptibility towards developing type 1 diabetes we have tested for thyroid (microsomal and thyroglobulin) and gastric-parietal cell antibodies in 86 pairs of identical twins, 47 discordant and 39 concordant for type 1 diabetes. Autoantibodies were detected in both twins of a pair in 35 and in neither twin in 45 pairs. In only 6 pairs (3 discordant) was there a discrepancy in the antibody results between co-twins. The frequency of antibodies was similar in twin pairs discordant, (21/44, 48%), and concordant, (14/36, 39%), for diabetes. Thyrogastric antibodies were not more frequent in pairs that were female, diagnosed above the age of 20, or had HLA DR3 as opposed to DR4. We conclude that thyrogastric autoantibodies are common in both type 1 diabetic patients and their non-diabetic identical twins. Their presence appears to be genetically determined but does not increase the susceptibility of developing diabetes. The presence of autoantibodies does not appear to indicate a separate aetiological type of diabetes.     

Environmental Factors in Obsessive-Compulsive Behavior: Evidence from Discordant and Concordant Monozygotic Twins

To investigate environmental factors that protect against or exacerbate obsessive-compulsive (OC) symptoms, we selected 25 monozygotic (MZ) twin pairs discordant, 17 MZ twin pairs concordant high and 34 MZ pairs concordant low on OC symptoms from a large longitudinal Dutch sample of adult twin pairs and their family members, applying stringent criteria for OC symptomatology. Data were collected on psychopathology, family structure, health, lifestyle, birth complications and life events. Unique environmental factors were studied using within-discordant MZ pair comparisons, whereas between-concordant MZ pair comparisons were used to study environmental factors that are shared by the twins of an MZ pair. The high-scoring MZ twins of the discordant group reported more life events (especially sexual abuse) than their low-scoring twin-siblings. The between-pair comparisons showed lower birth weight in the discordant MZ pairs than in the concordant MZ pairs. Further, the concordant high MZ pairs as well as their spouses had a lower educational level than the two other groups. On scale scores of anxious-depression, neuroticism, and somatic complaints, concordant high MZ pairs showed highest scores, and the discordant MZ pairs scored intermediate, except for neuroticism, on which the high-scoring twins of discordant MZ pairs were equal to the concordant high pairs. Discordance on psychological scale scores between the concordant MZ pairs was evident from 1991 onward, and within the discordant MZ pairs from 1997 onward, confirming previous reports of an association of early-onset OC symptoms with higher genetic load. Parent scores of OC symptoms and anxious-depression suggested intermediate genetic load in the discordant MZ group. In conclusion, this study reports on both unique and shared environmental factors associated with OC symptomatology. Whether these factors operate in addition to or in interaction with genetic disposition is to be elucidated in future studies. Edited by Tatiana Foroud.     

EEG differences in monozygotic twins discordant and concordant for schizophrenia

In an electroencephalographic (EEG) study of 27 pairs of monozygotic (MZ) twins discordant for schizophrenia, 13 pairs of MZ twins concordant for schizophrenia, 40 pairs of healthy MZ twins, and 91 healthy, unrelated subjects with repeated assessments, we investigated (a) the trait quality of brainwave patterns with respect to interindividual differences, intraindividual stability over time, and within-pair MZ concordance; (b) the EEG characteristics that enable discrimination between affected and unaffected individuals; and (c) the EEG characteristics that reflect the severity of illness. In comparison with healthy control subjects, the MZ twins who were discordant and concordant for schizophrenia exhibited a much lower within-pair EEG concordance, so that EEG abnormalities associated with schizophrenia and manifested differently in the co-twins concordant for schizophrenia seemed to reflect nongenetic, pathological developments of genetically identical brains.     

Evaluation of three commercial kits for the estimation of total glycolysed hemoglobin: Hb Al (author's transl)

It has been demonstrated by numerous workers that variations in levels of glycolysed hemoglobins Hb Al (Alb, Alb, Alc) are an excellent means of control of the quality of diabetes control. The estimation of the main glycolysed hemoglobin (Hb Alc) is very difficult, and various chromatographic methods have been developed to permit rapid estimation of all these glycolysed hemoglobins. Our work consisted of testing the three microcolumn kits on the french market: Isolab, Helena and Biorad. The great thermo-dependency of the first two kits did not permit us to obtain results in correlation with those of our reference technic derived from Trivelli's method. On the other hand, the levels of Hb Al obtained with the Biorad kit were perfectly correlated with the levels of Hb Alc. The average normal of Hb Al was 6,45 +/- 0,66 p. cent, CV 10,2 p. cent; the average value of Hblc was 5,4 +/- 0,4 p. cent. CV 7,4 p. cent. The average levels of Hb A obtained in diabetic subjects was 12 p. cent, the levels of Hblc being 10 p. cent. Certain restrictions in the use of these microcolumns were demonstrated: presence of Hb F or abnormal Hb, hyperlipemia and presence of chylomicrons.     

Handedness concordance and intelligence discrepancies in identical twins

The purpose of this study was to determine if the discrepancy in measured intelligence between identical twins concordant for handedness differed measureably from the discrepancy between identical twins discordant for handedness. If handed concordant and discordant twins did differ in terms of the between twin discrepancy in measured intelligence, then one could infer that congenital factors had caused dissociation of handedness and measured intelligence within a twin set. This finding would support Nagylaki and Levy's contention that the found discordance rates for handedness in identical twins is a function of "pathogenic" congenital factors disrupting the genetically determined handedness pattern. More generally, this finding would also support Satz's model with respect to pathological shifts in handedness due to brain insult either in utero or perinatally. However, in the current study, eight sets of identical twins were examined and no evidence was found to support these hypotheses. Instead, in one set where there was a marked discrepancy in measured intelligence, handedness could not be determined precisely for the twin with the lower intelligence quotient.     

Studies of kidney and muscle biopsy specimens from identical twins discordant for type I diabetes mellitus

To distinguish metabolic from genetic factors in the development of microangiopathy in diabetes, we evaluated biopsy specimens of kidney and quadriceps muscle from seven pairs of identical twins who were discordant for Type I (insulin-dependent) diabetes mellitus. Two of the diabetic patients had clinical diabetic nephropathy, including hypertension, marked albuminuria, and a substantially reduced creatinine clearance; the other five had normal renal function and only minor clinical indications of complications. All the twins of the diabetic patients had normal glomerular basement membrane widths and normal fractional volumes of the glomerular mesangium. Values for glomerular basement membrane width, tubular basement membrane width, and mesangial volume in each diabetic twin exceeded the values in the respective sibling (P less than or equal to 0.0035), even if the value in the diabetic twin lay within established normal ranges. Values for muscle capillary basement membrane width in the diabetic twins did not differ from those in their siblings (P = 0.5). Our observations suggest that the metabolic abnormalities of diabetes are necessary, if not sufficient, for the development of glomerular abnormalities. We also conclude that in diabetic patients, alterations in muscle capillary basement membrane width do not necessarily accompany pathologic lesions in the kidney.     

Apolipoprotein E type ε4 allele, heritability and age at onset in twins with Alzheimer disease and vascular dementia

The apolipoprotein E (APOE) ε4 allele is a risk factor in Alzheimer disease (AD), but not in vascular dementia (VaD). We have investigated whether the ε4 allele is more common in twin pairs concordant for AD, compared with those discordant for AD, and whether the ε4 allele is more common in AD twins than in VaD twins. In addition, we have investigated the relationship of the ε4 allele and the age at onset in AD and VaD. APOE genotype was analysed in 29 senile demented twin pairs. The ε4 allele was associated with AD and not with VaD. However, there was no difference in the frequency of the APOE ε4 allele in concordant (33.3%) and discordant (31.3%) AD dizygotic twin pairs. Age at onset in AD was significantly lower in ε4 homozygotes than in individuals with one or no copies of ε4 (62.4 vs. 73.5, p < 0.01). In concordant AD twin pairs, the ε4 allele frequency was somewhat higher in the twins with earlier onset (41.7% vs. 25%), but the difference was not statistically significant. In the VaD group the age at onset was not significantly different between individuals with or without ε4 in their genotypes.     

T-cell receptor repertoire analysis in monozygotic twins concordant and discordant for type 1 diabetes

Several data suggest that stochastic rearrangements of the TCR could play a pathogenic role in both disease predisposition and protection in type 1 diabetes (T1D). As twin sets offer an enormous potential in evaluating the role of genetic and environmental factors in susceptibility to disease, the main goal of this study was to assess whether the degree of sharing of the expressed TCR repertoire of twin pairs discordant for T1D differs from that of disease concordant pairs. We performed our analysis in 5 pairs of monozygotic twins, 3 of which were concordant and 2 discordant for T1D, by combining flow cytometry and CDR3 spectratyping on both CD4+ and CD8+ T-cells. Our data show that TCR repertoires show increased level of concordance within each twin pair, especially in CD8+ cells, in terms of mean BV expression levels on flow cytometry as well as of CDR3 patterns and frequencies of skewed or oligoclonal BV subfamilies on spectratyping. It is worth noting that the degree of similarity among twins seems to be independent of concordance or discordance for T1D. Our findings seem to suggest that in monozygotic twins with T1D the TCR repertoire is influenced by genetic factors more than by the presence of the autoimmune disorder itself.     

Acquired defect in interleukin-2 production in patients with type I diabetes mellitus

Deficient production of interleukin-2 has been reported in Type I diabetes, but its cause has not been elucidated. We therefore measured interleukin-2 production in 27 patients with Type I diabetes, 20 patients with Type II diabetes (6 requiring insulin), 5 monozygotic twin pairs discordant for Type I diabetes, and 10 nondiabetic persons with islet-cell antibodies. Interleukin-2 production was decreased in patients with Type I diabetes as compared with controls (35.8 +/- 2.5 vs. 61.6 +/- 4.6 percent, P less than 0.001). Interleukin-2 production did not differ between patients with Type II diabetes and controls, regardless of whether the patients used insulin. Twins with Type I diabetes had decreased interleukin-2 production as compared with normal controls (33.2 +/- 5.4 vs. 61.6 +/- 4.6 percent, P less than 0.001) and with their nondiabetic twins (33.2 +/- 5.4 vs. 54.5 +/- 3.4 percent, P less than 0.005). Interleukin-2 production in nondiabetic twins and in nondiabetic persons with islet-cell antibodies was normal. There was no correlation between glycosylated hemoglobin levels and interleukin-2 production in any diabetic group. We conclude that patients with Type I diabetes have an acquired defect in interleukin-2 production, whereas patients with Type II diabetes do not, and that this defect is not correlated with an ongoing autoimmune process, with hyperglycemia, or with insulin administration or oral hypoglycemic therapy. Thus, the defect appears to be related to marked beta-cell destruction, although not to the metabolic consequences thereof or the responsible autoimmune process.     

Identical twins discordant for multiple sclerosis have a shift in their T-cell receptor repertoires

CD4 T‐cells have an important role in the autoimmune response in multiple sclerosis (MS). We investigate the possibility that a shift occurs in the T‐cell receptor (TR) repertoire of identical twins discordant for MS. We compare the CDR3 spectratype distributions of 24 different TR V beta (TRBV) segments in naïve CD4 T‐cells from discordant MS twins and from healthy identical twins. We also compare the CDR3 spectratype distributions in unrelated healthy pairs, formed by combining members of different healthy twins, with the CDR3 spectratype distributions in unrelated pairs of MS patients and in unrelated pairs of their apparently healthy cotwins, formed by combining members of different discordant twins. We use the correlation coefficient (r‐value) as a measure of similarity of CDR3 spectratypes in each pair, and we test for the significance of the difference between r‐values from the different pairs. We observe that the r‐value for the CDR3 spectratype distributions among discordant twins differs significantly from the corresponding r‐value for the healthy twins for two TRBV segments. Further, the r‐values, for both the unrelated MS patient pairs and the unrelated pairs of their apparently healthy cotwins, differ significantly from the r‐values for healthy unrelated pairs of individuals. We conclude that both the MS patients and their apparently healthy cotwins have shifts in their CDR3 repertoires. Because we study naïve CD4 T‐cells, we postulate that CDR3 repertoire shifts precede MS and predispose to MS, but are unlikely to be sufficient to cause MS.     

Chromosome findings in twins with early-onset autistic disorder

In a twin study of autistic disorder, chromosome analyses were carried out in nine pairs of monozygotic (MZ) twins, two pairs of dizygotic (DZ) twins, one set of MZ triplets, one single twin from a MZ pair, and seven single twins from DZ pairs. All but one of the MZ sets were concordant for autistic disorder; all DZ pairs were discordant. Fragile X(q)(27.3) was found in one pair of MZ twins and in MZ triplets, i.e., in 9% of the population with autistic disorder. A marker chromosome of unknown origin was detected in a male twin with autistic disorder from a discordant DZ pair.     

A double heterozygous hemoglobin. Hemoglobin OIndonesia and hemoglobin DPunjab in an individual.

During surveys for abnormal hemoglobins in Iran, an individual was found to have four electrophoretically distinct hemoglobins. The abnormality was found only in the father of the propositus, in two of the father's sisters, and in three brothers and sisters of the propositus. Investigations revealed that the four hemoglobin components are the result of a double heterozygosity between an alpha-chain variant (Hb OIndonesia) and a beta-chain variant (Hb DPunjab). The presence of the abnormal hemoglobins was not associated with hemolytic disorders or obvious clinical symptoms.     

Down''s syndrome in twins

Male twins concordant for Down's syndrome and female twins discordant for Down's syndrome were investigated. Both males have trisomy 21 (47, XY, 21 +), and their parents are normal. One of the female twins is mosaic for trisomy 21 (46, XX/47, XX, 21 +) and the other is normal (46, XX). On the basis of multiple parameters, it is suggested that both pairs of twins are mono-zygous, including the female twins discordant for Down's syndrome.
Once the underlying cytogenetic mechanisms are understood and elucidated, genetic counselling can be undertaken.     

Similarities in Drinking Behavior of Twin’s Friends: Moderation of Heritability of Alcohol Use

Previous research has indicated that friends’ drinking may influence alcohol use in adolescents and young adults. We explored whether similarities in the drinking behavior of friends of twins influence the genetic architecture of alcohol use in adolescence and young adulthood. Survey data from The Netherlands Twin Register were available for 1,526 twin pairs aged 16–25 years. We categorized the twin pairs as concordant (both report similar alcohol use in their friends) or discordant for the alcohol use of their friends. Genetic moderator models were tested by carrying out multi-group analyzes in Mplus. Findings showed a significant moderation effect. Genetic factors were more and common environment less important in the explanation of variation in alcohol use in twins discordant for alcohol use of friends than in twins concordant for alcohol use of friends. Edited by Michael Lyons.     

Characterization of CD8+ T cell repertoire in identical twins discordant and concordant for multiple sclerosis

Autoreactive CD4+ and CD8+ T cells directed against CNS autoantigens may play a role in the development of multiple sclerosis (MS). Identical twins share the same genetic background but not the TCR repertoire that is shaped by the encounter with self or foreign antigens. To gain insights into the interplay between MS and T cell repertoire, peripheral blood CD4+ and CD8+ T lymphocytes and their CCR7+/CCR7- subsets from five pairs of identical twins (four discordant and one concordant for MS; none of which had taken disease-modifying therapy) were compared by TCR beta-chain (TCRB) complementary-determining region 3 (CDR3) spectratyping. CD4+ T cells generally showed a Gaussian distribution, whereas CD8+ T cells exhibited subject-specific, widely skewed TCR spectratypes. There was no correlation between CD8+ T cell oligoclonality and disease. Sequencing of predominant spectratype expansions revealed shared TCRB-CDR3 motifs when comparing inter- and/or intrapair twin members. In many cases, these sequences were homologous to published TCRs, specific for viruses implicated in MS pathogenesis, CNS autoantigens, or copaxone [glatiramer acetate (GA)], implying the occurrence of naturally GA-responding CD8+ T cells. It is notable that these expanded T cell clones with putative pathogenic or regulatory properties were present in the affected as well as in the healthy subject, thus suggesting the existence of a "MS predisposing trait" shared by co-twins discordant for MS.     

Healthy monozygous twins do not recognize identical T cell epitopes on the myelin basic protein autoantigen

The T cell response against myelin basic protein (MBP) has been extensively studied in humans because of its putative role in the pathophysiology of multiple sclerosis (MS). Higher concordance rates in monozygous twins as well as an increased risk in relatives suggest the role of genetic factors in MS susceptibility. Very little is known about the shaping of T cell repertoire towards self antigens in humans and their contribution to disease susceptibility in autoimmune disorders. Here we report the comparative T cell epitope recognition patterns towards the MBP auto-antigen in healthy identical twins. We have established MBP-specific T cell lines from eight sets of twins and characterized their fine epitope specificity. Intra-pair comparison showed the co-existence of shared as well as distinct epitopes in six of eight pairs and a complete absence of concordant epitope recognition within two other pairs. These findings indicate that important differences in T cell repertoires against a self antigen may be observed between genetically identical healthy individuals, rendering difficult the interpretation of the differences which may be observed between identical twins discordant for an autoimmune disease.     

Exercise-induced bronchial lability in monozygotic (identical) and dizygotic (nonidentical) twins

Exercise tests and skin tests were carried out on 8 pairs of identical and 7 pairs of nonidentical twins. The pairs of twins were selected so that at least one member of each pair had clinical asthma or was a first-degree relative of a patient with asthma and had an increased bronchial lability on exercise. Clinical concordance for active asthma was found in 3 of the identical pairs but only one of the nonidentical pairs. In 2 further identical pairs, one subject had active asthma and the other had a past history of asthma. In 6 of the identical pairs, the other twin was also found to have an increased bronchial lability, while only one of the nonidentical pairs was concordant in this respect. From the point of view of atopy shown by skin tests, 6 identical pairs were concordant compared with one of the nonidentical pairs. Concordance for atopy and bronchial lability did not necessarily go together. The significantly higher rate of concordance among the identical twins, for both increased bronchial lability and atopy, shows the importance of inheritance for these characters.     

Screening for hemoglobinopathies during routine hemoglobin A1c testing using the Tosoh G7 Glycohemoglobin Analyzer

Approximately 5.1% of the US population has diabetes mellitus, and hemoglobin (Hb) A1c levels are routinely measured to monitor long-term glycemic control in these patients. Many laboratories use ion exchange chromatography for such measurements, and the presence of hemoglobin variants and hemoglobinopathies often results in abnormal peaks on the chromatogram. The goal of this study was to evaluate the potential that detection of these abnormal peaks provides as a screening tool for Hb variants and hemoglobinopathies. We examined 366 specimens with abnormal peaks observed during routine Hb A1c measurements using the G7 Glycohemoglobin Analyzer (Tosoh Bioscience, Inc.). Hb variants and hemoglobinopathies were characterized by alkaline and acid electrophoresis, solubility testing for Hb S, and clinical parameters. In 252 cases, sickle cell trait was identified with a mean retention time (RT) of 1.44 (SD +/-0.02) min. In 82 cases, Hb C trait was identified with a mean RT of 1.66 +/-0.03 min. RTs for other Hb abnormalities, including sickle cell disease, homozygous Hb C disease, C Harlem trait, alpha-chain Hb variants, Hb D trait, Hb G trait, Hb J trait, Hb Raleigh, and Hb Lepore were also determined. Our results demonstrate that routine Hb A1c testing provides a potential screening tool for the detection of common hemoglobin variants and hemoglobinopathies.The previously unreported RTs for the G7 Glycohemoglobin Analyzer are provided, which can facilitate further testing in previously undiagnosed patients and confirm the cause of abnormal peaks in patients with known hemoglobin abnormalities.     

Phenotypic variability in monozygotic twins with neurofibromatosis 2

Mutations in the neurofibromatosis 2 (NF2) tumor suppressor gene on chromosome 22q12 cause a clinically variable autosomal dominant syndrome characterized by bilateral vestibular schwannomas (VSs), other nervous system tumors, and early onset lenticular cataracts. We studied three pairs of monozygotic (MZ) twins with NF2, all with bilateral VSs, to separate genetic from nongenetic causes of clinical variability. The evaluation included gadolinium-enhanced high-resolution magnetic resonance imaging of the head and spine, neuro-ophthalmic examination with slit lamp, physical examination, and zygosity testing with microsatellite markers. Each MZ pair was concordant for general phenotypic subtype (mild or severe) and often for the affected organ systems. However, the MZ pairs were discordant for some features of disease presentation or progression. For example, all three pairs were discordant for presence or type of associated cranial tumors. We hypothesize that phenotypic differences between NF2 MZ twins are at least partly due to stochastic processes, such as the loss of the second NF2 allele or alleles of other genes. © 1996 Wiley-Liss, Inc.     

Laterality in twins: The relationship between handedness and hemispheric asymmetry for speech

The present study examined the relationship between dichotic listening performance and handedness in twins. The 53 monozygotic (MZ) and 35 dizygotic (DZ) pairs concordant for right-handedness displayed ear asymmetries and total correct scores comparable to those found in right-handed singletons. The left- and right-handed members of the 19 MZ and 8 DZ pairs discordant for handedness were also similar to left- and right-handed singletons, respectively, with regard to ear asymmetry and overall performance. These data demonstrate that the relationship between handedness and brain organization observed in both MZ and DZ twins is similar to that found in the singleton population. The pattern of intraclass correlations obtained suggests that handedness discordance may be associated with greater differences in ear asymmetry within MZ pairs than within DZ pairs, possibly reflecting differences in the etiology of discordance for handedness in the two groups. In contrast, MZ cotwins were more similar than DZ cotwins, regardless of handedness, when total correct performance was measured.This research was supported in part by NIH Grant RO3MH2710101.