Association Between DSCR1 Variations and Congenital Heart Disease Susceptibility.

BACKGROUND The objective of this study was aimed to detect the association of Down syndrome critical region 1 (DSCR1) gene polymorphisms (rs149048873 and rs143081213) and congenital heart disease (CHD) susceptibility. MATERIAL AND METHODS This case-control study included 102 CHD patients and 113 healthy controls. Cases and controls were matched in age and gender. Genotypes of DSCR1 gene polymorphisms were detected by TaqMan method in cases and controls. Hardy-Weinberg equilibrium (HWE) examination was performed by PLINK 1.0 software. Chi square test was utilized to assess the distribution of the genotypes and the alleles. Relative risk of CHD was presented by odds ratios (ORs) with 95% confidence intervals (CIs). All of the calculations were implemented using SPSS 18.0. RESULTS Variant genotype distribution of rs149048873 and rs143081213 mutations were higher in cases than in controls, but the differences were not statistically obvious (P>0.05). Additionally, frequencies of mutant allele of the two polymorphisms were also significantly different in case and control groups (P>0.05). CONCLUSIONS No significant associations existed between DSCR1 gene rs149048873 and rs143081213 polymorphisms and CHD susceptibility.

Background

Congenital heart disease (CHD) refers to defects in heart and vessel structure which exist from birth. CHD is the most common type of congenital deformities and one of the leading birth defects related to deaths. Incidence of this disease in China was about 8/1000 in the past few years [1], and the morbidity presents an upward trend in recent years. CHD could be classified into various types, and its symptoms are related to the types. Among other symptoms, CHD frequently presents shortness of breath for some patients in early stage while others may express no sign throughout their lives.

CHD may be caused by genetic or environmental factors, but is usually a combination of the two sides [2-7]. It has been recognized that multiple environmental factors can increase the CHD risk through their influences on gravida during pregnancy, such as viral infection, chemical, and maternal diseases [8-11]. But not all pregnant women who expose to risk factors bear CHD infants, indicating there are differences in individual susceptibility which is determined by hereditary factors. So it is believed that the main causes of CHD embrace genetic changes, including focal mutation, deletion or insertion of DNA and chromosomal abnormalities [12]. Locating at chromosome 21, down syndrome critical region-1 (DSCR1, also known as RCAN1) gene is implicated in the structure of fetal heart [13]. It is speculated that single nucleotide polymorphisms (SNPs) of DSCR1 gene might play potential roles in the occurrence of CHD.

In this study, we compared the genotype distribution of the DSCR1 gene polymorphisms (rs149048873 and rs143081213) in CHD patients and healthy controls. The association between the DSCR1 gene polymorphisms and CHD susceptibility were detected in Chinese Han population.

Material and Methods

Subjects

In this case-control study, case group comprised 102 children with CHD who were hospitalized in Beijing Children’s Hospital affiliated to Capital Medical University from JAN 2012 to JAN 2015. The healthy controls were recruited from Beijing region. Controls were matched with cases in age and gender. All of the subjects were 0–11 years old and unrelated Chinese Han people. Written informed consents were signed by the children’s parents. This study was approved by the ethic committee of Beijing Children’s Hospital affiliated to Capital Medical University.

Genotyping method

Genomic DNA was extracted from 1ml fasting venous blood using TIANamp Blood DNA Kit (TIANGEN, China). Genotype distribution of DSCR1 gene polymorphisms (rs149048873 and rs143081213) were detected by TaqMan probe assay method using ABI PRISM 7700 system (Applied Biosystems, USA).

Statistical analysis

Hardy-Weinberg equilibrium (HWE) examination was performed by PLINK 1.0 software. SPSS 18.0 were used to conduct statistical analysis. P<0.05 is considered statistical significance. The differences of genotype and allele distribution between case and control groups were assessed by Chi square test. Odds ratios (ORs) with 95% confidence intervals (CIs) were utilized to present the relative risk of CHD.

Results

HWE examination

Genotype and allele distribution of rs149048873 and rs143081213 variants of DSCR1 gene were in accordance with HWE in both case and control groups (P>0.05), indicating the representativeness of the subjects.

Association of DSCR1 gene rs149048873 and rs143081213 variations with CHD risk

The frequencies of the genotypes and alleles of the two variations were compared between the case and control groups (Table 1). Variant genotypes AA and AA in rs149048873 and rs143081213 respectively were more frequent in case group than in control group. But the difference of the frequencies was not significant (P>0.05). Frequencies of rs149048873 A allele and rs143081213 A allele in cases were 9.31% and 6.86% respectively, and were higher than that in controls. No significant difference, however, was observed in the two allele between case and control groups (P>0.05).

Table 1

Genotype distribution of DSCR1 gene rs149048873 and rs143081213 polymorphisms.

SNP	Case n=102 (%)	Control n=113 (%)	P	OR (95%CI)
rs149048873
GG	84 (82.35)	99 (87.61)	–	–
GA	17 (16.67)	13 (11.50)	0.274	1.541 (0.708–3.357)
AA	1 (0.98)	1 (0.89)	0.908	1.179 (0.073–19.131)
G	185 (96.69)	211 (93.36)	–	–
A	19 (9.31)	15 (6.64)	0.304	1.445 (0.714–2.924)
rs143081213
GG	89 (87.25)	101 (89.38)	–	–
GA	12 (11.76)	11 (9.73)	0.629	1.238 (0.521–2.944)
AA	1 (0.98)	1 (0.89)	0.929	1.135 (0.070–18.410)
G	190 (93.14)	213 (94.25)	–	–
A	14 (6.86)	13 (5.75)	0.635	1.207 (0.554–2.633)

Discussion

CHD is defined as a gross structural abnormality of the heart or great vessels in actually (or potentially) functional significance. As the most common defect among birth defects, CHD is one of the leading causes of noninfectious death in the first year of neonates [14]. In 2000 CHD was provided a generic classification system. For some types of CHD, no symptom was detected throughout whole life. Unfortunately, most CHD cases develop the disease in their early lives. With the improvement of medical standards, the quantity of preterm infant is increasing, and so is the incidence of CHD. The mortality of the disease, however, shows a downward tendency [15]. Occasionally, the situations in a small part of CHD patients could improve without treatment. Mild abnormalities in patients having no obvious obstacle in circulatory function do not require any treatment. CHD is generally serious and requires to be treated through surgery and/or medications. CHD creates huge economic burdens to family and society. Early diagnosis and suitable treatment for CHD could increase the survival rate and achieve good prognosis. The exploration on CHD etiology will contribute to the diagnosis of it. Previous studies found that CHD is a complex disease, and affected by gene and environment factors [16-18]. However, the pathogenesis of CHD is still unclear.

To date, several studies have investigated the pathogenic genes of CHD [19-21]. It is reported that DSCR1 gene is related to cardiogenesis [22-24]. Protein encoded by DSCR1 gene is a regulator of calcineurin 1, and inhibits the genetic transcription of the calcineurin-dependent signaling pathways. The expression of DSCR1 gene is mainly detected in the heart and central nervous system in embryos [22]. This gene is located in chromosome 21q22.12, and contains 9 exons. It has been revealed that a regulatory sequence in the promoter region of human DSCR1 gene could alter the expression of the gene [24]. DSCR1 gene is associated with many diseases [25-28], including CHD. Polymorphisms of the gene might play potential roles in the expression of the gene, and contribute to the occurrence and development of many diseases. rs149048873 and rs143081213, the two SNPs in the promoter region of DSCR1 gene, may change the expression of this gene, and then affect the occurrence of CHD. However, there were few studies focusing on relationship of these polymorphisms with the occurrence of CHD.

So we explored the association between DSCR1 gene polymorphisms (rs149048873 and rs143081213) and the susceptibility of CHD in this study through detecting the distribution of the genotypes and alleles of the two SNPs in case and control groups. Even though distribution of the variant genotypes mutations was higher in cases than in controls, no significant difference was found between the two groups. Similar results were observed in the variant alleles. Frequencies of A and A alleles in the polymorphisms rs149048873 and rs143081213 respectively were 9.31% and 6.86% in cases, and higher than in controls (about 2.67% and 1.11%). The differences still were not significant. These results were identical with those from previous study which conducted in sporadic CHD [28]. Our study suggested that DSCR1 gene rs149048873 and rs143081213 polymorphisms had no significant association with the CHD risk.

Conclusions

Although the subjects were representative, there still existed many limitations in our study, including small sample size and unadjusted results. Therefore, well designed multiple-center studies need to be carried out in the future to obtain more effective evidence to clarify the etiology of CHD.