The design of twins reared apart, very rare genetic epidemiological resources has been hailed as fascinating experiment of nature. However, not so many studies have been based on it due to the difficulty in recruiting the participants. It also makes the only existing research on twins raised apart particularly valuable. How to utilize these resources fully will be the focus of this research area. This review will overview its design background, basic hypothesis, and current status of research and give advice for the research in this field in China.
China ; Humans ; Research Design ; trends ; Twin Studies as Topic ; trends ; Twins ; genetics ; statistics & numerical data

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.
DNA Methylation ; Epigenesis, Genetic ; Forensic Genetics ; Genomic Imprinting ; Histones/genetics* ; Humans ; Twin Studies as Topic ; Twins, Monozygotic/genetics*

The prevalence of child and adolescent growth and mental-behavior related diseases are increasing, and the pathogenesis are complex. Twins are excellent natural resources for complex chronic diseases research as they share the maternal intrauterine environment, born at the same time and share the same family environment in early years, which could benefit the adjust ment of confounding factors, such as age, genetic factors and early family environmental factors. Birth cohort with twin families involved could be more effective in exploring the genetic and environmental factors for complex chronic diseases at the very beginning of life. This paper summarizes the objective, content, progress, strengths and potential problems of Wuhan Twin Birth Cohort, with emphasis on the overall design and progress of the study.
Adolescent ; Asian People ; Birth Weight ; Child ; China ; Cohort Studies ; Diseases in Twins/genetics* ; Epidemiological Monitoring ; Female ; Humans ; Male ; Twin Studies as Topic ; Twins

OBJECTIVETo analyse the heritabilities of physical growth items of body and its related factors.

METHODSAn 116 twin pairs of Han nationality, 67 monozygotic (MZ) and 49 like-sex dizygotic (DZ) aged 6 to 12 years, were investigated from June to October in 2004. The measurements included height, weight, sitting height, chest circumference, biacromial breadth and biiliac breadth, and BMI index calculated by the former two measurements. The heritabilities were estimated by using intraclass correlation coefficient method from the adjusted data for age.

RESULTSThe intraclass correlation coefficient was greater in the MZ twins than in the DZ twins. The estimated heritabilities of height, weight, BMI, sitting height, chest circumference, biacromial breadth and biiliac breadth were 0.89, 0.88, 0.73, 0.87, 0.78, 0.78, 0.73 in boys and 0.87, 0.74, 0.72, 0.86, 0.62, 0.56, 0.59 in girls adjusted for age. Therefore, there were no sex difference for the heritabilities of height, sitting height and BMI, but the male heritabilities of weight, chest circumference, biacromial breadth and biiliac breadth were higher than the female's respectively.

CONCLUSIONPhysical growth items should be mainly determined by the genetic factors. There are sex differences for the heritabilities of weight, chest circumference, biacromial breadth and biiliac breadth, i.e., the girls might be affected more easily by environmental factors than the boys in these items.

Asian Continental Ancestry Group ; genetics ; Body Height ; genetics ; Body Mass Index ; Body Weight ; genetics ; Child ; China ; Female ; Humans ; Male ; Twin Studies as Topic ; Twins, Dizygotic ; ethnology ; genetics ; Twins, Monozygotic ; ethnology ; genetics

OBJECTIVESTo study the contribution of the genes and environment to variation of serum levels of lipids and lipoprotein.

METHODSOne hundred and forty-three healthy monozygotic (MZ) twin pairs and 93 dizygotic (DZ) ones aged 5 to 19 [with a mean of (11.2 +/- 3.4) years]. Microsatellite polymorphism (STR) was used to diagnose zygosity of twins, and intraclass correlation coefficient method and Falconer formula were performed to investigate heritability of serum lipids and lipoproteins unadjusted or adjusted for age and sex. Logarithmic transformation was used for data with skewed distribution. Influence of relevant physical and biochemical indicators on serum lipids and other components was analyzed with partial coefficients of correlation adjusted for age and sex.

RESULTSIn the twin samples, difference in serum level of triglycerides (TG) between MZ and DZ was not statistically significant with intraclass variation and intraclass correlation. There was significant difference in serum levels of total cholesterol (TC), high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol (LDL-C), and lipoprotein [Lp(a)] between MZ and DZ, with their heritability estimates of 0.56, 0.55, 0.49 and 0.58 unadjusted, respectively, and 0.63, 0.63, 0.55 and 0.64 adjusted for age and sex, respectively. Serum levels of TC, HDL-C, LDL-C and Lp(a) correlated reversely with age. Serum levels of TC, HDL-C and LDL-C in girls were slightly higher than those in boys. Most indicators for serum levels of lipids and lipoprotein, except for serum level of Lp(a) correlated with body mass index (BMI), body fat ratio, Pelidisi index, and other indexes such as blood pressure, blood sugar, serum level of calcium, adjusted for age and sex.

CONCLUSIONSSerum levels of TC, HDL-C and Lp(a) were influenced more greatly by genetic factors, and serum level of TG was mainly influenced by environmental ones. Levels of blood lipids in children were influenced by age and sex, and correlated with indicators that reflect their body fat and nutritional status.

Adolescent ; Adult ; Age Factors ; Child ; Cholesterol, HDL ; blood ; genetics ; Cholesterol, LDL ; blood ; genetics ; Female ; Humans ; Lipids ; blood ; genetics ; Lipoproteins ; blood ; genetics ; Male ; Sex Factors ; Triglycerides ; blood ; genetics ; Twin Studies as Topic ; Twins, Dizygotic ; Twins, Monozygotic