A descriptive analysis of hyperlipidemia in adult twins in China / 中华流行病学杂志

Objective: To describe the distribution characteristics of hyperlipidemia in adult twins in the Chinese National Twin Registry (CNTR) and explore the effect of genetic and environmental factors on hyperlipidemia. Methods: Twins recruited from the CNTR in 11 project areas across China were included in the study. A total of 69 130 (34 565 pairs) of adult twins with complete information on hyperlipidemia were selected for analysis. The random effect model was used to characterize the population and regional distribution of hyperlipidemia among twins. The concordance rates of hyperlipidemia were calculated in monozygotic twins (MZ) and dizygotic twins (DZ), respectively, to estimate the heritability. Results: The age of all participants was (34.2±12.4) years. This study's prevalence of hyperlipidemia was 1.3% (895/69 130). Twin pairs who were men, older, living in urban areas, married,had junior college degree or above, overweight, obese, insufficient physical activity, current smokers, ex-smokers, current drinkers, and ex-drinkers had a higher prevalence of hyperlipidemia (P<0.05). In within-pair analysis, the concordance rate of hyperlipidemia was 29.1% (118/405) in MZ and 18.1% (57/315) in DZ, and the difference was statistically significant (P<0.05). Stratified by gender, age, and region, the concordance rate of hyperlipidemia in MZ was still higher than that in DZ. Further, in within-same-sex twin pair analyses, the heritability of hyperlipidemia was 13.04% (95%CI: 2.61%-23.47%) in the northern group and 18.59% (95%CI: 4.43%-32.74%) in the female group, respectively. Conclusions: Adult twins were included in this study and were found to have a lower prevalence of hyperlipidemia than in the general population study, with population and regional differences. Genetic factors influence hyperlipidemia, but the genetic effect may vary with gender and area.

A descriptive analysis on hypertension in adult twins in China / 中华流行病学杂志

Objective: To describe the distribution characteristics of hypertension among adult twins in the Chinese National Twin Registry (CNTR) and to provide clues for exploring the role of genetic and environmental factors on hypertension. Methods: A total of 69 220 (34 610 pairs) of twins aged 18 and above with hypertension information were selected from CNTR registered from 2010 to 2018. Random effect models were used to describe the population and regional distribution of hypertension in twins. To estimate the heritability, the concordance rates of hypertension were calculated and compared between monozygotic twins (MZ) and dizygotic twins (DZ). Results: The age of all participants was (34.1±12.4) years. The overall self-reported prevalence of hypertension was 3.8%(2 610/69 220). Twin pairs who were older, living in urban areas, married, overweight or obese, current smokers or ex-smokers, and current drinkers or abstainers had a higher self-reported prevalence of hypertension (P<0.05). Analysis within the same-sex twin pairs found that the concordance rate of hypertension was 43.2% in MZ and 27.0% in DZ, and the difference was statistically significant (P<0.001). The heritability of hypertension was 22.1% (95%CI: 16.3%- 28.0%). Stratified by gender, age, and region, the concordance rate of hypertension in MZ was still higher than that in DZ. The heritability of hypertension was higher in female participants. Conclusions: There were differences in the distribution of hypertension among twins with different demographic and regional characteristics. It is indicated that genetic factors play a crucial role in hypertension in different genders, ages, and regions, while the magnitude of genetic effects may vary.

Clinical analysis of monochorionic-diamniotic twins with genetic discordance / 中华医学遗传学杂志

OBJECTIVE@#To explore the genetic etiology of 5 cases of monochorionic-diamniotic (MCDA) with genetic discordance.@*METHODS@#148 cases of MCDA twins who were diagnosed by amniocentesis at the Maternal and Child Health Care Hospital of Guangxi Zhuang Autonomous Region from January 2016 to June 2020 were selected as the study subjects. Relevant clinical data of the pregnant women were collected, and amniotic fluid samples of the twins were collected separately. Chromosomal karyotyping analysis and single nucleotide polymorphism array (SNP array) assay were carried out.@*RESULTS@#The results of chromosomal karyotyping analysis showed that 5 of the MCDA twins had inconsistent chromosome karyotypes, with an incidence of 3.4% (5/148). SNP array assay showed that 3 fetuses were mosaics.@*CONCLUSION@#Genetic discordance occurs among MCDA twins, and prenatal counseling for such cases should be given by doctors with experience in medical genetics and fetal medicine, and personalized clinical management should be recommended.

A descriptive analysis on coronary heart disease in adult twins in China / 中华流行病学杂志

Objective: To describe the distribution characteristics of coronary heart disease in adult twins recruited from Chinese Twin Registry (CNTR), and provide clues and evidence for the effect of genetic and environmental influences on coronary heart disease. Methods: By using the data of CNTR during 2010-2018, a total of 34 583 twin pairs aged ≥18 years who completed questionnaire survey and had related information were included in the current study to analyze the population and area distribution characteristics of coronary heart disease. Random effect models were used to compare the differences between groups. The concordane rate of coronary heart disease were calculated respectively in monozygotic (MZ) twin pairs and dizygotic (DZ) twin pairs to estimate the heritability. Results: The twin pairs included in this analysis were aged (34.2±12.4) years. The overall prevalence rate of coronary heart disease in twin pairs was 0.7%. Twin pairs who were women, older, obese and lived in northern China had higher prevalence of coronary heart disease (P<0.05). Intra-pair analysis in the same-sex twin pairs found that the concordane rate of coronary heart disease was higher in MZ twin pairs (25.3%) than in DZ twins (7.4%), and the difference was statistically significant (P<0.001). The overall heritability of coronary heart disease was 19.3% (95%CI: 11.8%-26.8%). Stratified by gender, age and area, the concordane rate was still higher in MZ twin pairs than in DZ pairs. Participants who were women, aged 18-30 years or ≥60 years and lived in northern China had a higher heritability of coronary heart disease. Conclusion: The distribution of coronary heart disease in twin pairs differed in populations and areas. The prevalence of coronary heart disease was affected by genetic factors, but the effect varied with age, gender and area.

A descriptive analysis on type 2 diabetes in twins in China / 中华流行病学杂志

Objective: To describe the distribution characteristics of type 2 diabetes in twins in Chinese National Twin Registry (CNTR), provide clues and evidence for revealing the influence of genetic and environmental factors for type 2 diabetes. Methods: Of all twins registered in the CNTR during 2010-2018, a total 18 855 twin pairs aged ≥30 years with complete registration information were included in the analysis. The random effect model was used to describe the population and area distribution characteristics and concordance of type 2 diabetes in twin pairs. Results: The mean age of the subjects was (42.8±10.2) years, the study subjects included 10 339 monozygotic (MZ) twin pairs and 8 516 dizygotic (DZ) twin pairs. The self-reported prevalence rate of type 2 diabetes was 2.2% in total population and there was no sighificant difference between MZ and DZ. Intra-twin pairs analysis showed that the concordance rate of type 2 diabetes was 38.2% in MZ twin pairs, and 16.0% in DZ twin pairs, the difference was statistically significant (P<0.001). The concordance rate of type 2 diabetes in MZ twin parts was higher than that in DZ twin pairs in both men and women, in different age groups and in different areas (P<0.05). Further stratified analysis showed that in northern China, only MZ twin pairs less than 60 years old were found to have a higher concordance rate of type 2 diabetes compared with DZ twin pairs (P<0.05). In southern China, the co-prevalence rate in male MZ twin pairs aged ≥60 years was still higher than that in DZ twin pairs (P<0.05). Conclusion: The twin pairs in this study had a lower self-reported prevalence of type 2 diabetes than the general population. The study results suggested that genetic factors play a role in type 2 diabetes prevalence in both men and women, in different age groups and in different areas, however, the effect might vary.

Estudo datiloscópico entre gêmeos monozigóticos para fins de identificação humana / Datiloscopic study between monozygotic twins for human identification purposes

Objetivo: Analisar as características datiloscópicas entre pares de gêmeos monozigóticos (GM), observando coincidências e divergências entre os irmãos e avaliando o potencial identifi-catório dos relevos dérmicos digitais para individualização dos mesmos. Material e Métodos: Estudo cego e transversal, quanti-tativo, de abordagem indutiva e observação direta extensiva. As impressões digitais foram analisadas e classificadas em tipos fundamentais (arco, presilha interna, presilha externa, verticilo e anômalo) e acidentais (anômalo, cicatriz e amputação) e, posteriormente, assinalados os pontos característicos. Resulta-dos: Foram coletadas 46 fichas datiloscópicas, oriundas de 23 pares de GM, sendo 14 duplas pertencentes ao sexo feminino e 9 ao masculino, com idades entre 18 e 28 anos. Os dedos que apresentaram maior concordância entre os pares de GM foram os polegares, direito e esquerdo, e o anular direito, com 82,5%. Na mão direita, o padrão mais observado foi presilha externa, enquanto no membro esquerdo o tipo prevalente foi presilha interna. Conclusão: As estruturas que compõem as impressões digitais, apesar de muito semelhantes, são capazes de individualizar GM pela existência de pontos característicos individuais, auxiliando no processo de identificação humana. (AU)

Objective: To analyze dactyloscopy characteristics between MT pairs, observing coincidences and divergences between the siblings and evaluating the identification potential of the finger-prints for their individualization. Material and Methods: Blind and cross-secional, quantitative study with inductive approach and extensive direct observation. The fingerprints were analyzed and classified into patternal types (arch, internal clip, external clip, verticil and anomalous) and accidental (anomalous, scar and amputation) and, later, the characteristic points were pointed out. Results: 46 fingerprint records were collected from 23 MT pairs, of those 14 were female pairs and 9 male, with ages between 18 to 28 years. The fingers that showed the highest agreement among the MT pairs were the right and left thumbs, and the right ring finger with 82.5%. The right hand showed the external clip as the most frequent pattern, while the left hand the prevalent type was internal clip. Conclusion: The fingerprints' components, although very similar, are able to individualize MT by the existence of individual characteristic points, supporting the process of human identification. (AU)

Acardius mylacephalus: un diagnóstico poco frecuente / Acardius mylacephalus: an infrequent diagnosis

Se presenta el caso clínico de una primigesta de 21 años de edad, a quien se le detectó un embarazo gemelar monoamniótico y monocigótico en el examen ecográfico en el Centro Provincial de Genética de Santiago de Cuba. El primer feto presentaba hidronefrosis bilateral predominantemente en el lado izquierdo, y el segundo estructura fetal rudimentaria y deforme, área cardíaca mal estructurada y latidos cardíacos solo arrítmicos y bradicárdicos, además de que no se definieron los órganos internos y todo se encontraba rodeado de linfangioma quístico grave con grandes quistes paravertebrales y un solo cordón umbilical con tres vasos. Lo descrito en la ecografía se corroboró con los resultados de la necropsia, lo cual se correspondió con la variedad Acardius mylacephalus

The case report of a 21 years primigravida woman is presented to whom a monoamniotic and monochorial twin pregnancy was detected in the echographic exam at the Genetic Provincial Center of Santiago de Cuba. The first fetus presented bilateral hydronephrosis predominantly in the left side, and the second rudimentary and deformed fetal structure, not well structured heart area and just arrhythmic and bradycardiac heart beats besides that the internal organs were not defined and everything was surrounded by severe cystic lymphangioma with big paravertebral cysts and a single umbilical cord with three vessels. Everything described in the echogram was corroborated with the results of the autopsy, which corresponded with Acardius mylacephalus variety

Research Progress on the Detection Method of DNA Methylation and Its Application in Forensic Science / 法医学杂志

As an important part of epigenetic marker, DNA methylation involves in the gene regulation and attracts a wide spread attention in biological auxology, geratology and oncology fields. In forensic science, because of the relative stable, heritable, abundant, and age-related characteristics, DNA methylation is considered to be a useful complement to the classic genetic markers for age-prediction, tissue-identification, and monozygotic twins' discrimination. Various methods for DNA methylation detection have been validated based on methylation sensitive restriction endonuclease, bisulfite modification and methylation-CpG binding protein. In recent years, it is reported that the third generation sequencing method can be used to detect DNA methylation. This paper aims to make a review on the detection method of DNA methylation and its applications in forensic science.

Genetic and Environmental Effects on the Abdominal Aortic Diameter Development / Efeitos Genéticos e Ambientais no Desenvolvimento do Diâmetro da Aorta Abdominal

Abstract Background: Configuration of the abdominal aorta is related to healthy aging and a variety of disorders. Objectives: We aimed to assess heritable and environmental effects on the abdominal aortic diameter. Methods: 114 adult (69 monozygotic, 45 same-sex dizygotic) twin pairs (mean age 43.6 ± 16.3 years) underwent abdominal ultrasound with Esaote MyLab 70X ultrasound machine to visualize the abdominal aorta below the level of the origin of the renal arteries and 1-3 cm above the bifurcation. Results: Age- and sex-adjusted heritability of the abdominal aortic diameter below the level of the origin of the renal arteries was 40% [95% confidence interval (CI), 14 to 67%] and 55% above the aortic bifurcation (95% CI, 45 to 70%). None of the aortic diameters showed common environmental effects, but unshared environmental effects were responsible for 60% and 45% of the traits, respectively. Conclusions: Our analysis documents the moderate heritability and its segment-specific difference of the abdominal aortic diameter. The moderate part of variance was explained by unshared environmental components, emphasizing the importance of lifestyle factors in primary prevention. Further studies in this field may guide future gene-mapping efforts and investigate specific lifestyle factors to prevent abdominal aortic dilatation and its complications.

Resumo Fundamento: A configuração da aorta abdominal relaciona-se com o envelhecimento saudável e uma série de distúrbios. Objetivos: Avaliar efeitos herdáveis e ambientais no diâmetro da aorta abdominal. Métodos: 114 pares de gêmeos adultos (69 monozigóticos e 45 dizigóticos do mesmo sexo), com idade média de 43,6 ± 16,3 anos, foram submetidos a ultrassonografia abdominal com o aparelho Esaote MyLab 70X para visualização da aorta abdominal abaixo da origem das artérias renais e 1-3 cm acima da bifurcação aórtica. Resultados: A herdabilidade ajustada para idade e sexo do diâmetro da aorta abdominal abaixo da origem das artérias renais foi 40% [intervalo de confiança (IC) 95%, 14 – 67%] e acima da bifurcação, 55% (IC 95%, 45 – 70%). Nenhum dos diâmetros aórticos apresentou efeitos ambientais comuns, mas os efeitos ambientais não compartilhados foram responsáveis por 60% e 45% dos traços, respectivamente. Conclusões: Nossa análise mostrou herdabilidade moderada e diferença do diâmetro da aorta abdominal com especificidade de segmento. A parte moderada da variância foi explicada pelo componente ambiental não compartilhado, enfatizando a importância do estilo de vida na prevenção primária. Estudos adicionais nesse campo poderão guiar futuros esforços de mapeamento genético e investigar fatores específicos de estilo de vida para prevenir dilatação da aorta abdominal e suas complicações.

Genetic and environmental influence on thyroid gland volume and thickness of thyroid isthmus: a twin study

Objectives Decreased thyroid volume has been related to increased prevalence of thyroid cancer. Subjects and methods One hundred and fourteen Hungarian adult twin pairs (69 monozygotic, 45 dizygotic) with or without known thyroid disorders underwent thyroid ultrasound. Thickness of the thyroid isthmus was measured at the thickest portion of the gland in the midline using electronic calipers at the time of scanning. Volume of the thyroid lobe was computed according to the following formula: thyroid height*width*depth*correction factor (0.63). Results Age-, sex-, body mass index- and smoking-adjusted heritability of the thickness of thyroid isthmus was 50% (95% confidence interval [CI], 35 to 66%). Neither left nor right thyroid volume showed additive genetic effects, but shared environments were 68% (95% CI, 48 to 80%) and 79% (95% CI, 72 to 87%), respectively. Magnitudes of monozygotic and dizygotic co-twin correlations were not substantially impacted by the correction of covariates of body mass index and smoking. Unshared environmental effects showed a moderate influence on dependent parameters (24-50%). Conclusions Our analysis support that familial factors are important for thyroid measures in a general twin population. A larger sample size is needed to show whether this is because of common environmental (e.g. intrauterine effects, regional nutrition habits, iodine supply) or genetic effects.

Combined Genome-Wide Linkage and Association Analyses of Fasting Glucose Level in Healthy Twins and Families of Korea

This study was undertaken to identify genetic polymorphisms that are associated with the risk of an elevated fasting glucose (FG) level using genome-wide analyses. We explored a quantitative trait locus (QTL) for FG level in a genome-wide study from a Korean twin-family cohort (the Healthy Twin Study) using a combined linkage and family-based association analysis approach. We investigated 1,754 individuals, which included 432 families and 219 pairs of monozygotic twins. Regions of chromosomes 2q23.3-2q31.1, 15q26.1-15q26.3, 16p12.1, and 20p13-20p12.2, were found to show evidence of linkage with FG level, and several markers in these regions were found to be significantly associated with FG level using family-based or general association tests. In particular, a single-nucleotide polymorphism (rs6138953) on the PTPRA gene in the 20p13 region (combined P = 1.8 x 10(-6)) was found to be associated with FG level, and the PRKCB1 gene (in 16p12.1) to be possibly associated with FG level. In conclusion, multiple regions of chromosomes 2q23.3-2q31.1, 15q26.1-15q26.3, 16p12.1, and 20p13-20p12.2 are associated with FG level in our Korean twin-family cohort. The combined approach of genome-wide linkage and family-based association analysis is useful to identify novel or known genetic regions concerning FG level in a family cohort study.

Genetic and environmental determinants of menstrual characteristics.

Background: The impact of women's menstrual cycle on her quality of life, health, work, and community is substantial. Menstrual disturbance is linked with general ill conditions such as migraine, asthma, and endocrinopathies. The clinical significance of medical interventions to prevent these conditions becomes clear if the role of genetic or environment is clarified. Aims: To identify the genetic and environmental contribution on menstrual characteristics. Setting and Design: This was a cross-sectional study in 2 Asian countries. Materials and Methods: 2 cohorts of monozygotic and dizygotic twins born between (1945-1988, n = 122) and (1951-1993, n = 71) were taken. A standard questionnaire was designed inclusive of socio- demographic characteristics of subjects as well as menstrual history (duration, interval, amount, irregularity). Subjects were interviewed by phone. Statistical Analysis: Quantitative variables were analyzed using Falconars' formula as well as maximum likelihood analysis. Structural modeling was then applied to twin correlations to provide estimates of the relative genetic and/or environmental factors contribution in determining the measured trait. Results: Menstrual characteristics were found to be under environmental influence where the best fitting model for menstrual interval and duration was common environment. CDF plotting confirmed the results for both variables. Proband-wise concordance analysis for amount of menstruation, amenorrhea, and irregular menstruation revealed no genetic influence. The best fitting model for menstrual irregularity was CE (C73%, E27%). The same model was defined for amenorrhea (C48%, E52%). Conclusions: Environmental factors are most likely responsible to determine the menstrual flow, its integrity, and regularity. These factors need to be studied further.

Differences of DNA methylation profiles in monozygotic twins' blood samples / 法医学杂志

OBJECTIVE@#To evaluate the potential usefulness of DNA methylation in individual discrimination of monozygotic twins by investigating the differences of DNA methylation profiles in monozygotic twins' blood samples.@*METHODS@#Blood samples from 22 pairs of monozygotic twins were obtained with informed consent. Genomic DNA extracts were bisulfite treated followed by detection with Infinium HumanMethylation27 BeadChip Assays(Illumina, USA). Epigenetic distances between each pair of monozygotic twins and each pair of unrelated individuals of same gender were calculated with Euclidean distance algorithms. Distribution of epigenetic distance in monozygotic twin group was statistically compared with that in unrelated individuals.@*RESULTS@#Difference of epigenetic distance between male and female pairs was not statistically significant in unrelated individual group or in monozygotic twin group (P = 0.0695 and 0.4825, respectively). Epigenetic distance of monozygotic twins was significantly lower than that of unrelated individual pair of same gender (Median: 6.02 vs 7.20, P = 0.0002). However, all the epigenetic distance in monozygotic twin group or in unrelated individuals were significantly higher than 4.00 (P < 0.000 1).@*CONCLUSION@#DNA methylation profiles of monozygotic twin's blood samples were significantly different with each other, which was similar to that in unrelated individuals of same gender. These results indicated that DNA methylation was a useful biomarker in individual discrimination of monozygotic twins.

Discordância de apresentação da doença celíaca em gêmeos monozigóticos

CONTEXTO: A doença celíaca é uma enteropatia autoimune causada pela sensibilidade ao glúten em indivíduos geneticamente predispostos. Apesar da característica genética da doença, estudos demonstram discordância de 30 por cento na sua apresentação em gêmeos monozigóticos. OBJETIVO: Apresentar dois pares de gêmeos monozigóticos, comprovados por estudos genéticos, discordantes para apresentação da doença celíaca. MÉTODO: Os pacientes foram acompanhados no Serviço de Gastroenterologia Pediátrica do Hospital das Clínicas da Universidade Federal de Minas Gerais desde 1990, sendo submetidos a exames clínicos periódicos, biopsias intestinais e sorologia para anticorpos IgG e IgA antigliadina, determinados pela técnica de ELISA (ensaio imunoenzimático), e anticorpos classe IgA antiendomísio, determinados pela técnica de imunofluorescência indireta. Estudos genéticos foram realizados através da técnica de amplificação por PCR e posterior tipagem de loci de microssatélites do tipo STR (short tandem repeats). RESULTADOS: Em cada par de gêmeos, apenas um apresentou doença celíaca até o momento, mostrando que, apesar do genótipo idêntico, este não foi o único determinante para a expressão da doença. CONCLUSÃO: Outros fatores, ambientais e genéticos, parecem contribuir para determinação da doença.

CONTEXT: The celiac disease is an immune-mediated enteropathy caused by a permanent sensitivity to gluten in genetically susceptible individuals. Despite the genetic characteristic of the disease, studies show discrepancy of 30 percent in its presentation in monozygotic twins. OBJECTIVE: To present two pairs of monozygotic confirmed by genetic study and discordant for presentation of celiac disease. METHODS: The patients were followed up at the Pediatric Gastroenterology Service - Hospital das Clínicas da Universidade Federal de Minas Gerais, MG, Brazil, since 1990, and were submitted to periodical clinical examinations, intestinal biopsies and serology for IgA and IgG antigliadin antibodies, determined by the ELISA technique, and IgA antiendomysial, determined by indirect immunofluorescence. Genetic study was conducted by the technique of amplification by PCR and later typing loci of microsatellites type of STR (short tandem repeats). RESULTS: In each pair of twins only one has presented celiac disease so far, demonstrating that despite the identical genotype, it was not the single determinant to express the condition. CONCLUSION: Other environmental and genetic factors might contribute to determining the disease.

A Case of Monozygotic Twins with Crohn's Disease / 대한소화기학회지

Although the incidence and prevalence rates of IBD in Korea are still lower than Western populations, they have been increasing rapidly during the past decades. Crohn's disease (CD) tends to run in families because it is thought to be related to genetic susceptibility coupled with environmental factors. A large number of monozygotic and dizygotic twin pairs with inflammatory bowel disease have been reported in western countries. The population relative risk in first-degree relatives is considered to be about equal in both Koreans and westerners. To our best knowledge, there is no report in monozygotic twins with CD in Korea. This case report is the first documented occurrence of concordant CD occurring in monozygotic twins in Korea.

A Case of Monozygotic Twins with Crohn's Disease / 대한소화기학회지

Although the incidence and prevalence rates of IBD in Korea are still lower than Western populations, they have been increasing rapidly during the past decades. Crohn's disease (CD) tends to run in families because it is thought to be related to genetic susceptibility coupled with environmental factors. A large number of monozygotic and dizygotic twin pairs with inflammatory bowel disease have been reported in western countries. The population relative risk in first-degree relatives is considered to be about equal in both Koreans and westerners. To our best knowledge, there is no report in monozygotic twins with CD in Korea. This case report is the first documented occurrence of concordant CD occurring in monozygotic twins in Korea.

Epigenetics and its new progress in monozygotic twins / 法医学杂志

Epigenetic, which refers to heritable differences of genes without changing their DNA sequences, is one of the most important biology phenomena in multicellular eukaryotes. Its research contents involves DNA methylation, genomic imprinting, histone acetylation, histone methylation, chromatin remodeling, pseudogene, and microRNA etc. Monozygotic twins is developed from one single zygote and are genetically identical in genomic DNA sequence. From the view of classical genetics, traditional genetic markers such as short tandem repeat and single nucleotide polymorphism can not play important role in discriminating monozygotic twins. So it is very essential to find new genetic markers. Recent achievements made in epigenetics show that there exist striking differences in monozygotic twins and provide a new strategy to discriminate the monozygotic twins. In this paper, the concepts, research contents of epigenetics and its application perspective in discriminating monozygotic twins are reviewed.

Genetic and Environmental Influences on Birthweight in a Sample of Korean Twins

This study is the first report of genetic and environmental influences on birthweight using Korean twins. The sample consisted of 255 monozygotic (MZ) and 178 dizygotic (DZ) twin pairs drawn from the Seoul Twin Family Study. Intraclass twin correlations were computed for the twins' birthweights obtained from parents (typically mothers) of the twins. To estimate genetic and shared and nonshared environmental influences on birthweight, standard univariate model-fitting analyses were performed using a software, Mx. For each gender, MZ twin correlations were higher than DZ twin correlations, suggesting existence of genetic influences on birthweight; however, DZ twin correlations were higher than half the MZ twin correlations, indicating that shared environmental factors are also important. For each zygosity, twin correlations were not significantly different between males and females, implicating that genes and environments that cause individual differences in birthweight may not vary between males and females. Model-fitting analyses based on the data pooled across gender yielded estimates of 17% for genetic, 60% for shared environmental, and 23% for nonshared environmental influences on birthweight.

Expression in normals and in subjects with schizophrenia of a novel gene fragment originally isolated from monozygotic twins discordant for schizophrenia

Differentially expressed clones from subtracted cDNA libraries of a pair of monozygotic twins discordant for schizophrenia have been reported in the literature. The clones were expressed in lymphocytes from the healthy twin, but not from the schizophrenic twin. In the current study, we assessed the expression of one of these clones, oksc12b, in 10 normal controls and in 10 patients who met DSM-IV criteria for schizophrenia and had never received neuroleptic medication. We hypothesized that this clone would be differentially expressed in normal controls and in the schizophrenic patients, and that its expression could be a peripheral marker of the disease. Lymphocytes were isolated and total RNA was purified, reverse-transcribed, and quantified by two PCR methods. In the first PCR assay, oksc12b expression was measured relative to beta-actin gene expression. The second PCR assay consisted of a competitive procedure using a heterologous DNA internal standard. Neither method confirmed any difference in oksc12b expression between schizophrenic patients and normal controls. Subtypes of schizophrenia or the general heterogeneity of this syndrome may explain the discrepancy found. It is also possible that the differentially expressed clones are present in discordant monozygotic twins, but not in other patients.

Crescimento fetal / Fetal growth

No presente texto os autores revisam os fatores que determinam e influenciam o crescimento fetal, assim como os métodos para sua avaliação, sem, no entanto pretender esgotar o assunto