Genetic Variants at the rs4720169 Locus of TBX20 and the rs12921862 Locus of AXIN1 May Increase the Risk of Congenital Heart Defects in the Mexican Population: A Pilot Study

Abstract

Background:

Congenital heart defects (CHDs) are the most common type of birth defects and a major cause of infant mortality. Although knowledge of genetic risk variants for CHDs is scarce, most cases of CHDs are considered to be due to multifactorial inheritance.

Objective:

To analyze the association of 14 single nucleotide polymorphic variants previously associated with a risk of CHDs in a Mexican population with isolated CHDs.

Materials and Methods:

DNA samples obtained from healthy subjects and from subjects with isolated atrial, ventricular, or atrioventricular septal defects living in Northeastern Mexico were analyzed by real time-polymerase chain reaction for allelic discrimination of genetic variants of the genes TBX1, TBX20, ASTX-18-AS1, AXIN1, MTHFR, NKX2.5, BMP4, and NFATc1. The odds ratios (ORs) for allele and genotype frequencies and inheritance models were obtained.

Results:

Forty-two patients and 138 controls were included. Two variants were found to confer a risk of CHDs: variant rs4720169 of TBX20 in which the OR for the heterozygous state was 1.88 (95% confidence interval [CI]: 1.12-3.14, p = 0.010), whereas the OR for the homozygous state was 3.82 (95% CI: 1.18-12.3, p = 0.010); and variant rs12921862 of AXIN1 in which the OR for the heterozygous state was 4.15 (95% CI: 2.42-7.10; p ≤ 0.001), whereas the OR for the homozygous state was 9.2 (95% CI: 1.31-64.7, p = 0.008) for allele A.

Conclusion:

Genetic variants of the TBX20 and AXIN1 genes confer a significantly increased risk of congenital septal heart defects in a population from Northeastern Mexico.

Introduction

Congenital heart defects (CHDs) encompass a group of anomalies of the heart and the great vessels. These defects are the most common type of human malformations with a worldwide frequency of 7 of every 1000 live newborns (Burn and Goodship, 2007). The frequency of CHDs in Mexico is unknown; however, their impact on childhood mortality is remarkable since they represent the second most common cause of death in children <4 years old, and the number of cases has increased since 1998 in most Mexican states (Torres-Cosme et al., 2016; INEGI, 2018). Like most human malformations, CHDs may be explained by multifactorial inheritance, with a concordance and a heritability of 40-60% and 37%, respectively (Davison, 1967; Kuo et al., 2018). Early diagnosis and prevention of congenital birth defects have improved worldwide, and the survival rate has increased, such that the study of genetic and environmental contributing factors has gained interest among public health researchers (Torres-Cosme et al., 2016).

To analyze the genetic risk factors for CHDs, it is important to note that embryonic heart development includes a complex and well-orchestrated transcription regulation network, involving ∼1500 genes (of which only 239 are well identified) and additional noncoding sequences that lead to the migration of neural crest cells and mesodermal cellular growth, proliferation, and differentiation at as early as the fourth week of gestation (Bentham and Bhattacharya, 2010; Devaux et al., 2015). The role of gene mutations and copy number variations in CHDs associated with monogenic and chromosome syndromes has been increasingly understood (e.g., TBX1 in 22q11 deletion syndrome, ELN in Williams syndrome, and TBX5 in Holt-Oram syndrome). Nonsyndromic and isolated CHDs are less understood since multiple genes and gene interactions may be involved. The development of new techniques, such as genome-wide sequencing (GWS) and exome sequencing, has enabled researchers to find gene variants that may confer a risk of CHDs in specific populations.

For example, studies have identified risk variants for the development of different types of heart malformations in the Chinese population (Table 1). The frequencies of these risk variants are estimated in the general population based on public databases whose information is obtained by GWS tests, scientific publications, and ancestry tests.

Table 1.

Some of the Single Nucleotide Variants Reported in the Literature, Showing rs Code, Population in Which the Study Was Done, Related Type of Congenital Heart Defect, Allele Risk Variant, and Statistical Analysis

References	Polymorphism	Gene	Population	Type of CHD	Risk variant	OR
Wang et al. (2013a)	rs1045642	ABCB1	Sichuan, China	Any CHD	C allele	3.5
Qian et al. (2014)	rs762642	BMP4	Nanjing, China		G allele	1.22
Wang et al. (2013b)	rs2277923	NKX2-5	Wuhuan, China			1.26
Zhao et al. (2015)	rs870142	STX18-AS1	Chengdu, China	ASD	T allele	1.5
Pu et al. (2015)	rs12921862	AXIN1	Sichuan, China		A allele	3.09
Zhu et al. (2006)	rs1801133	MTHFR	Liaoning, China		TT genotype	4.08
Ma et al. (2015)	rs4720169	TBX20	Urumqi, China		A allele	1.96

ASD, atrial septal defect; CHD, congenital heart defects; OR, odds ratio.

However, not many studies exist regarding genetic variants and CHDs in the Mexican population. Only the variants C677T (rs1801133) and A1298C (rs1801131) in the MTHFR gene have been studied, and the results have been controversial. Balderrábano-Saucedo et al. (2013) found a positive association between mothers with a genotype with variant rs1801133 (TT vs. TC and CC alleles) and the presence of complex CHDs in their offspring, whereas Sánchez-Urbina et al. (2012) did not find an increased risk with any of the mother-child genotype combinations when analyzing the same variant. Both studies involved patients from central Mexico.

Due to the genetic diversity of the Mexican population, the aim of this study is to analyze the risk association of 14 single nucleotide variants (SNVs) from eight genes that were previously reported to be associated with a risk of CHDs in a population with CHDs from Northeastern Mexico.

Materials and Methods

From 2010 to 2012, participants were recruited from two public local hospitals: University Hospital “Dr. José Eleuterio González” and Maternal and Child Highly Specialized Regional Hospital, which are both located in Nuevo León, Mexico. The study was approved by the Ethics and Research Committee of the University Hospital “Dr. José Eleuterio González” and Autonomous University of Nuevo León (UANL) (No. GN11-003). Before enrollment, all participants or their guardians provided written informed consent after the study was explained to them. This was a prospective case-control study that included subjects with a confirmed nonsyndromic ventricular septal defect (VSD), atrial septal defect (ASD), or endocardial cushion defect (ECD). Subjects with a positive family history of a CHD or with a clear environmental risk factor related to the malformation were excluded. Similarly, the presence of other malformations could suggest a chromosomal or monogenic etiology for the CHD, thus subjects with additional symptoms were also excluded. Control subjects were obtained from previously collected DNA samples from healthy individuals, which were stored in the DNA Bank of the Genetics Department at University Hospital “Dr. José Eleuterio González.”

Genetic variants selection

Single copy variant polymorphisms were identified from the existing literature. The search was conducted with the following keywords: “congenital heart defect,” “heart malformation,” “polymorphism,” “SNP,” and “genetic variant.” Studies were selected if they met the following criteria: (1) a description of the allele frequency in the population under examination, (2) the odds ratios (OR) calculation, and (3) a significant p-value. Most of the studies involved the Chinese population, so our search was limited to that population to compare the frequencies found with our findings involving the Mexican population. No markers for ancestry were included in the study since no differences in ancestry proportions have been identified in northeastern populations (Cerda-Flores et al., 2002; Martinez-Fierro et al., 2009). Genes, type of variant, locus, function, and the associated CHD are listed in Table 2.

Table 2.

Selected Single Nucleotide Variants

Gene	Locus	SNV	CHD type	Function	Position	Pred ^a	Ref. ^a	Alt. ^a	Alternate allele frequency
Gene	Locus	SNV	CHD type	Function	Position	Pred ^a	Ref. ^a	Alt. ^a	Asian,^a %	Latino,^a %	Northeast Mexican population,^b %
TBX1	22q11.2	rs41260844	VSD	Transcription factor	Upstream	Benign	C	T	49.7	23.2	21.0
TBX20	7p14.2	rs17675131	ASD	Transcription factor	Intron	Benign	G	A	24.4	49.3	46.0
TBX20	7p14.2	rs4720169	ASD	Transcription factor	Intron	Benign	G	A	33.9	61.0	53.0
STX-18-AS1	4p16	rs16835979	ASD	Antisense RNA	Intron	Benign	C	A	33.5	22.1	24.0
		rs6824295			Intron	Benign	C	T	34.0	22.3	24.0
		rs870142			Intron	Moderate pathogenic	C	T	32.3	22.0	24.0
AXIN1	16p13.3	rs370681	ASD	Cytoplasmic protein	Intron	Benign	C	T	30.4	38.9	39.0
		rs1805105			Exon 2	Benign	A	G	29.9	43.9	46.0
		rs12921862			Intron	Benign	C	A	20.3	11.0	16.0
MTHFR	1p36	rs1801133	VSD, ASD, ECD	Folate metabolism	Exon 5	Possible pathogenic	G	A	29.4	50.3	48.0
MTHFR	1p36	rs1801131	VSD, ASD, ECD	Folate metabolism	Exon 8	Possible pathogenic	T	G	21.9	16.0	18.0
NKX2.5	5q35.1	rs2277923	ASD	Transcription factor	Exon 1	Benign	T	C	63.4	54.9	50.0
BMP4	14q22.2	rs762642	ASD	Morphogenetic protein	Intron	Benign	A	C	40.7	43.9	39.0
NFATc1	18q23	rs754505	Any CHD	Transcription factor	Intron	Benign	G	A	9.9	4.3	11.0

Reference sequence (Ref.)^a and alternate allele (Alt.)^a are shown, as well as their frequency in Asian and Latin populations.

Bold indicates variants whose frequency differs from Latin and Northeast Mexican populations.

Frequencies were obtained from VarSome data library (Kopanos et al. 2018).

Allele frequencies for Northeast Mexican populations are the ones found in this study.

ECD, endocardial cushion defect; Pred, variant classification; SNV, single nucleotide variant; VSD, ventricular septum defect.

DNA extraction and genotyping

Genomic DNA was isolated from venous blood or from dry blood spots on filter paper using QIAamp^® DNA Blood Mini Kit (QIAGEN, Hilden, Germany), following provider specifications, and posteriorly frozen at −20°C until further analysis. DNA quantity and quality were obtained using the NanoDrop™ 8000 Spectrophotometer (Thermo Fisher, Wilmington). Polymerase chain reaction (PCR) amplification and genotyping were performed using real time-PCR in the Step One Plus (Thermo Fisher). A set of prevalidated SNVs was used for rhAmp in the Step One Plus (Thermo Fisher) in 10 μL. SNV allelic discrimination was done using FAM and YAKIMA.

Data analysis

Genotype and allele frequencies were obtained. Differences in distributions between both groups were analyzed with Pearson's chi-squared test. The role of each of these variants in the etiology of CHD is not completely understood, and neither the underlying genetic model of behavior is known for each allele, so we decided to analyze in two different ways. On the one hand, assuming that each variant acts independently, the Hardy-Weinberg equilibrium (HWE), allele and genotypic frequencies, and ORs were calculated using the IHG program (https://ihg.helmholtz-muenchen.de/ihg/snps.html). On the other hand, assuming that the variants are linked, a Mendelian inheritance model could be proposed using the allele and genotype frequencies. The OR values were obtained, and the one with the lowest Akaike Information Criterion (AIC) value was used to select the Mendelian model that fit the best. The analysis was performed using the SNPStats program (www.snpstats.net/start.htm). A p-value <0.05 was considered statistically significant.

Results

Samples from 50 patients with nonsyndromic VSD, ASD, or ECD were obtained. Eight samples were excluded from the analysis due to incomplete data. Twenty-three subjects were male and 19 were female. Subjects' ages ranged from 0 months to 9 years, and 72% were <1 year old. There were 27 subjects with VSD, 9 with ASD, 1 with ECD, and 2 subjects with both ASD and VSD. Blood samples from 138 unmatched healthy controls were obtained from the Genetics Department's biobank to match a 3:1 ratio.

Allelic and genotype frequencies and association analysis

All but 3 of the 14 SNVs were in HWE of which two variants were identified in the control group (rs754505 of NFATc1 and rs370681 of AXIN1). As a result, these two variants were excluded from the analysis since alleles must be in HWE in the control group to be considered suitable for association analysis. The other variant was identified in the case group (rs12921862 of AXIN1), thereby suggesting that it is related to pathology. Pearson's chi-squared test revealed statistical significance for variants rs4720169 of TBX20 (p = 0.05) and rs12921862 of AXIN1 (p ≤ 0.001) for septal heart defects (ASD, VSD, or ECD) between the case and control groups. Variants rs1801133 and rs1801131 of the MTHFR gene, which had previously been studied in Mexico, did not show an increased risk of CHDs in our population. The rest of the variants (rs41260844, rs17675131, rs16835979, rs6824295, rs870142, rs370681, rs1805105, rs2277923, rs762642, and rs754505) also did not show an increased risk of CHDs as statistical significance was not found.

According to the independent segregation model, only two variants showed a statistically significant increase in the risk of CHDs: assuming that the alternate allele (A) is related with risk (instead of the reference G allele), allele and genotype frequencies for variant rs4720169 of TBX20 revealed an OR of 1.88 (confidence interval [CI]: 1.12-3.14, p = 0.015) for allele A and an OR of 3.88 (CI: 1.18-12.33, p = 0.018) for homozygous AA. Assuming that the alternate allele (A) is related with risk (instead of the reference C allele), variant rs12921862 of AXIN1 revealed an OR of 4.15 (CI: 2.42-7.10, p ≤ 0.001) for allele A and an OR of 9.23 (CI: 1.31-64.71, p = 0.008) for homozygous AA. Armitage's trend test showed an OR of 1.90, p = 0.01 and an OR of 5.11 p ≤ 0.001 for rs4720169 on TBX20 and rs12921862 on AXIN1, respectively (Table 3).

Table 3.

According to the Independent Segregation Model, Two Variants rs4720169 and rs12921862, Showed a Statistically Significant Risk Based on Allele and Genotype Frequencies

	Control	n	%	Cases	N	%	Assuming risk allele A
rs4720169	GG	33	0.30	GG	4	0.04	[G] vs. [A]	[GG vs. GA]	[GG+] vs. [AA]	[GG] vs. [GA+AA]	Common OR
TBX20	GA	64	0.68	GA	19	0.18	OR = 1.88 CI = 1.12-3.14 p = 0.015	OR = 2.44CI = 0.77-7.79p = 0.120	OR = 3.82 CI = 1.18-12.33 p = 0.018	OR = 2.986CI = 0.99-8.98p = 0.043	OR = 1.90 p = 0.018
	AA	41	0.38	AA	19	0.19
	HWE			HWE
	p = 0.41			p = 0.81

	Control	n	%	Cases	n	%	Assuming risk allele A
rs12921862	AA	3	0.03	AA	2	0.08	[C] vs. [A]	[CC] vs. [CA]	[CC+] vs. [AA]	[CC] vs. [CA+AA]	Common OR
AXIN1	AC	38	0.36	AC	33	0.20	OR = 4.15 CI = 2.41-7.10 p ≤ 0.001	OR = 12.03 CI = 4.90-29.53 p = <0.001	OR = 9.23 CI = 1.31-64.71 p = <0.001	OR = 11.82 CI = 4.85-28.80 p = <0.001	OR = 5.11 p = <0.001
	CC	97	0.97	CC	7	0.13
	HWE			HWE
	p = 0.74			p ≤ 0.001

Statistically significant values are in bold.

CI, confidence interval; HWE, Hardy-Weinberg equilibrium.

Regarding the dependent segregation model, rs4720169 of TBX20 revealed an OR of 3.82 (CI: 1.18-12.34, p = 0.05) in a codominant model, whereas variant rs12921862 of AXIN1 showed an OR of 0.08 (CI: 0.03-0.21, p ≤ 0.001) in a dominant model (Table 4). Results for all variants are shown in Supplementary Tables S1 and S2.

Table 4.

According to a Dependent Segregation Model, rs4720169 and Variant rs12921862 on AXIN1 Reveal a Statistical Significant Odds Ratio for Codominant and Dominant Models, Respectively

Model	Genotype	Cases	Control	OR (95% CI)	p	AIC
Variant rs472016
Codominant	A/A	19 (45.2%)	41 (29.7%)	1.00	0.05	195.6
	G/A	19 (45.2%)	64 (46.4%)	1.56 (0.74-3.29)
	G/G	4 (9.5%)	33 (23.9%)	3.82 (1.18-12.34)
Variant rs12921862
Dominant	c/c	7 (16.7%)	97 (70.3%)	1.00	<0.001	160.2
Dominant	c/A-A/A	35 (83.3%)	41 (29.7%)	0.08 (0.03-0.21)	<0.001	160.2

The one with the lowest AIC value was used to select the Mendelian model that fit best.

Statistically significant values are in bold.

AIC, Akaike Information Criterion.

Discussion

Variants in the sequence of genes that regulate embryonic cardiac processes are thought to act as risk factors for CHDs; however, there is little knowledge of how they influence abnormal development of the heart. The genes selected for this study have been associated with an increased risk of CHDs in selected Chinese populations (Wang et al., 2012; Shen et al., 2013; Wang et al., 2013b; Qian et al., 2014; Xuan et al., 2014; Ma et al., 2015; Pu et al., 2015; Zhao et al., 2015). However, there are no data available on the frequency of these variants in the Mexican population (frequencies found in this study are shown in Table 2). For most alleles, the reported frequency of the alternate allele in the Latino population is similar to the one found in subjects from Northeastern Mexico, except for rs4720169 of TBX20, rs1801133 of MTHFR, and rs754505 of NFATc1 (although rs754505 of NFATc1 was not in HW equilibrium in our control group). While it is possible that these differences could be skewed due to a small sample size, a case-control study with a 3:1 ratio supports the validation of these findings.

The two variants we found to be associated with a risk of CHDs, rs4720169 in TBX20 and rs12921862 in AXIN1, have also been identified in the Chinese population (Ma et al., 2015; Pu et al., 2015, respectively). TBX20 is a member of the T-BOX family, a transcription factor required for mammalian heart development. It is involved in the differentiation and proliferation of the second heart field and, therefore, contributes to cardiac neural crest migration and the formation of the right ventricle and the outflow tract. Analyzing rs4720169 as an independent variant, Ma et al. (2015) found that this SNV was risk related in patients with ASD, with an OR of 1.96 for the AA genotype (p = 0.008), which is lower than the OR found in our study (OR 3.82, CI = 1.18-12.33, p = 0.018) following an independent model. These findings support the notion that this gene is involved in alterations of heart development. However, an analysis assuming a non-Mendelian-dependent model revealed an OR of 3.82 (CI = 1.18-12.34, p = 0.05) for a codominant model for the GG genotype. The A allele was found to be more frequent in our population (68% in cases and 53% in controls) compared with the Asian population (34%) (Kopanos et al., 2018). Since there are no other studies comparing the frequency of this SNV in other Mexican regions, further studies are needed to determine the distribution of this variant throughout Mexico, its association with CHDs, and environmental factors involved that could modify this variant's role in pathology.

AXIN1 is a component of the WNT signal transduction pathway, and has a role in the β-catenin complex assembly regulating cell proliferation and promoting myogenesis or osteogenesis. Pu et al. (2015) studied three variants (rs12921862, rs1805105, and rs370681) of the AXIN1 gene; for rs12921862, they found a significantly increased risk of ASD with an OR of 3.09 (CI: 2.03-4.71, p ≤ 0.001) for the A allele. In the independent model analysis, the same variant revealed a similar significance with an OR of 4.15 (CI: 2.42-7.10, p ≤ 6.61 × 10⁻⁸) for the same allele, whereas there was an OR of 12.03 (CI: 4.9-29.5, p = 7.811 × 10⁻¹⁰) for the heterozygous CA genotype and an OR of 9.23 (CI: 1.3-64.7, p = 0.008) for the homozygous AA genotype. Assuming a dependent segregation model, however, the association analysis revealed an OR of 0.08 (CI: 0.03-0.21, p ≤ 0.001) in a dominant model.

Both SNVs are located in nontranscribed regions: rs4720169 of TBX20 is located in intron 3 and rs12921862 of AXIN1 is located in intron 2. According to the American College of Human Genetics guidelines (Richards et al., 2015) for the interpretation of sequence variants, these SNVs had been previously classified as BA1 (allele frequency is >5%) and also BP4 (multiple lines of computational evidence suggest no impact on gene or gene product) because of their frequency in most populations. Although the roles of these SNVs are not completely understood, it is well known that complete inactivation of either gene leads to embryonic lethality. As such, it is possible that these variants can act as negative regulators for normal gene function and may influence susceptibility to CHDs. Given that functional studies have not been done to determine if the variants are associated with an altered transcription process, further studies should be conducted to understand the effect of these variants in gene expression. We propose that the differences seen in the two association models could be related to the type of analysis performed (independent segregation vs. dependent segregation). A larger sample and a multivariate analysis would also allow us to establish which of the two analysis models best explain the behavior of these SNVs.

According to the American College of Medical Genetics guidelines, the two variants rs1801133 and rs1801131 of the MTHFR gene, which were previously studied in Mexico, have sometimes been referred to as pathogenic for different malformations in some populations. Polymorphism 677C→T (rs1801133) has been studied in almost all Mexican states, where it has been found that the frequency of the T allele is higher than that in other populations, which is similar to what has been found in the Chinese population (Wang et al., 2016). Although the frequency of the T allele varies throughout Mexican states (Contreras-Cubas et al., 2016), a previous study in Nuevo Leon found a prevalence of 19.7% for the TT genotype, 54.2% for CT, and 26% for CC (Aguirre-Rodríguez et al., 2008), which is consistent with our results (TT 23%, CT 52%, and CC 25%). In our study, this variant did not reveal a statistically significant association with CHDs in either of the two models; however, in studies of the Chinese population, this variant has been associated with CHDs (Zhu et al., 2006; Xu et al., 2010; Xuan et al., 2014). Since the effect of this variant is closely related to folic acid blood levels because of its role in folate metabolism, it is possible that our study did not show an association of CHDs with this variant of MTHFR because we focused solely on septal defects and did not perform a multivariate analysis considering folic acid consumption between the case and control groups. Future studies will be pursued to establish whether folate levels and this variant are, in fact, associated with a higher risk of CHDs in the Mexican population. It is also possible that in other Mexican states the relationship between the variants and CHDs could be different since other genetic markers have shown genetic stratification across Mexico (Silva-Zolezzi et al., 2009).

In conclusion, two previously reported SNVs of TBX20 and AXIN1, which are involved in the development of the embryonic heart, were found to be associated with CHDs in a northeastern Mexican population. Nevertheless, a larger sample may be needed to confirm the association of these variants, and a multivariable analysis may be required to determine any correlation with environmental risk factors since CHDs are multifactorial in origin.

Footnotes

Acknowledgments

We are grateful to the parents of the patients who kindly agreed to collaborate in the study, to the Medical Genetics Department in Hospital Universitario “Dr. José E. González” for the funding support, to the medical students who assisted with the project, and to Dr. Gabriela Elizondo Cárdenas for writing assistance.

Author Disclosure Statement

No competing financial interests exist.

Funding Information

This study was funded by the Genetics Department from University Hospital “Dr. José E. Gonzalez.”

Supplementary Material

References

Aguirre-Rodríguez

, Martínez-de Villarreal

, Velazco-Campos

, et al. (2008) Prevalence of 677T polymorphism of the MTHFR gene in a population sample from Nuevo León, México [in Spanish]. Salud Pública México, 50:5-6.

Balderrábano-Saucedo

, Sánchez-Urbina

, Sierra-Ramírez

, et al. (2013) Polymorphism 677c→t MTHFR gene in Mexican mothers of children with complex congenital heart disease. Pediatr Cardiol, 34:46-51.

Bentham

, Bhattacharya

(2010) Molecular basis of cardiovascular development. In: Kumar

, Elliot P (eds) Principles and Practice of Clinical Cardiovascular Genetics. Oxford. University Press, New York, pp 17-25.

Burn

, Goodship

(2007) Congenital heart disease. In: Rimoin

, Connor

, Pyeritz

, Korf B (eds) Emery and Rimoin's Principles and Practice of Medical Genetics, 5th ed. Elsevier, Pennsylvania, pp 1083-1159.

Cerda-Flores

, Budowle

, Jin

, et al. (2002) Maximum likelihood estimates of admixture in northeastern Mexico using 13 short tandem repeat loci. Am J Hum Biol, 14:429-439.

Contreras-Cubas

, Sánchez-Hernández

, García-Ortiz

, et al. (2016) Heterogeneous distribution of MTHFR gene variants among Mestizos and Diverse Amerindian Groups from Mexico. PLoS One, 11:e0163248.

Davison

(1967) Concordance and discordance of congenital heart disease in 20 families. J Med Genet, 4:245-250.

Devaux

, Zangrando

, Schroen B et al. (2015) Long noncoding RNAs in cardiac development and ageing. Nat Rev Cardiol, 12:415-425.

Instituto Nacional de Estadística y Geografía (INEGI) (2018) Principales causas de mortalidad por residencia habitual, grupos de edad y sexo del fallecido. Available at: www.inegi.org.mx/programas/mortalidad (accessed January 20, 2019).

10.

Kopanos

, Tsiolkas

, Kouris

, et al. (2018) VarSome: The Human Genomic Variant Search Engine. BioRxiv. 2018. Available at: https://varsome.com (accessed February 10, 2019).

11.

Kuo

, Lin

, Hung

, et al. (2018) Familial aggregation and heritability of congenital heart defects. Circ J, 82:232-238.

12.

, Xiang

, Li

, et al. (2015) [Association between TBX20 gene polymorphism and congenital atrial septal defects]. Zhonghua Nei Ke Za Zhi, 54:860-864.

13.

Martinez-Fierro

, Beuten

, Leach

, et al. (2009) Ancestry informative markers and admixture proportions in northeastern Mexico. J Hum Genet, 54:504-509.

14.

, Chen

, Zhou

, et al. (2015) Association between polymorphisms in AXIN1 gene and atrial septal defect. Biomarkers, 19:674-678.

15.

Qian

, Mo

, Da

, et al. (2014) Common variations in BMP4 confer genetic susceptibility to sporadic congenital heart disease in a Han Chinese population. Pediatr Cardiol, 25:1442-1447.

16.

Richards

, Aziz

, Bale

, et al. (2015) Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics and the association for molecular pathology. Genet Med, 17:405-424.

17.

Sánchez-Urbina

, Galaviz-Hernández

, Sierra-Ramírez

, et al. (2012) Methylenetetrahydrofolate reductase gene 677CT polymorphism and isolated congenital heart disease in a Mexican population [in Spanish]. Rev Esp Cardiol, 65:158-163.

18.

Silva-Zolezzi

, Hidalgo-Miranda

, Estrada-Gil

, et al. (2009) Analysis of genomic diversity in Mexican Mestizo populations to develop genomic medicine in Mexico. PNAS, 106:8611-8616.

19.

Shen

, Li

, Shen

, et al. (2013) Association of NFATc1 gene polymorphism with ventricular septal defect in the Chinese Han population. Chin Med J, 126:78-81.

20.

Torres-Cosme

, Rolón-Porras

, Aguinaga-Ríos

, et al. (2016) Mortality from congenital heart disease in Mexico: A problem on the rise. PLoS One, 11:e0150422.

21.

Wang

, Xie

, Zhou

, et al. (2013a) Increased risk for congenital heart defects in children carrying the ABCB1 Gene C3435T polymorphism and maternal periconceptional toxicants exposure. PLoS One, 8:e68807.

22.

Wang

, Chen

, Ma

, et al. (2012) Genetic analysis of the TBX1 gene promoter in ventricular septal defects. Mol Cell Biochem, 370:53-58.

23.

Wang

, Fu

, Li

, et al. (2016) Geographical and ethnic distributions of the MTHFR C677T, A1298C and MTRR A66G gene polymorphisms in Chinese populations: A meta-analysis. PLoS One, 11:e0152414.

24.

Wang

, Zou

, Zhong

, et al. (2013b) Associations between two genetic variants in NKX2-5 and risk of congenital heart disease in Chinese population: A meta-analysis. PLoS One, 8:e70979.

25.

, Xu

, Xue

, et al. (2010) MTHFR c.1793G>A polymorphism is associated with congenital cardiac disease in a Chinese population. Cardiol Young, 7:1-9.

26.

Xuan

, Li

, Zhao

, et al. (2014) Association between MTHFR polymorphisms and congenital heart disease: A meta-analysis based on 9,329 cases and 15,076 controls. Sci Rep, 4:7311.

27.

Zhao

, Li

, Dian

, et al. (2015) Association between the European GWAS-identified susceptibility locus at chromosome 4p16 and the risk of atrial septal defect: A case-control study in Southwest China and a meta-analysis. PLos One, 10:e0123959.

28.

Zhu

, Li

, Yan

, et al. (2006) Maternal and offspring MTHFR gene C677T polymorphism as predictors of congenital atrial septal defect and patent ductus arteriosus. Mol Hum Reprod, 12:51-54.

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