Delta-Sarcoglycan Gene Polymorphism Frequency in Amerindian and Mestizo Populations of Mexico

Abstract

Mutations on the delta-sarcoglycan gene have been associated with the development of both hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy. Recently, the polymorphism c.−94C>G was associated with HCM in Japanese patients. The aim of our study was to evaluate the frequency of c.−94C>G polymorphism in Mexican-Amerindian and Mexican-Mestizo populations. We analyzed the frequency of this polymorphism in 165 Mexican-Amerindian individuals (23 Triquis, 25 Zapotecos, 24 Mayas, 41 Nahuas, and 52 Mixtecos) and 100 unrelated Mexican-Mestizos. Allele frequencies were similar in all Amerindian groups (0.33 Triquis, 0.54 Zapotecos, 0.54 Mayas, 0.46 Nahuas, and 0.49 Mixtecos). When compared with Mexican-Mestizos, only Triquis were different (p = 0.00742). However, when comparing the total sample of the Amerindian population with the Mestizos, the difference was not significant (p = 0.12225). Allele frequencies of Mexican populations were higher than in Asians and less than African and European populations (p < 0.05). These data show that the distribution of the C allele is higher in Mexican populations studied and consequently it is necessary to define if this may be associated with genetic susceptibility for HCM in the Mexican patients.

Introduction

Sarcoglycans (SGs) are assembled into a tetrameric complex constituted by α, β, γ, and δ SGs that are integrated into the dystrophin-associated protein complex. Mutations on these proteins are responsible for limb/girdle muscular dystrophies (LGMD-2D, -2E, -2F, and -2C, respectively) (Lim et al., 1995; Noguchi et al., 1995; Nigro et al., 1996). δ-SG is one of the first proteins of the SG complex to be expressed during muscle development and has been considered fundamental for the assembly and insertion in sarcolemma. Further, gene defects in δ-SG have been associated with the development of both hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) (Nigro, 1997; Moreira et al., 2003).

Currently, there are about 27 known variations in SG gene (SGCD) (www.dmd.nl/sgcd_seqvar.html). Three are the mutations c.212G>C (Kärkkäinen et al., 2003), c.451T>G, and c.699 + 13_699 + 15de (Tsubata et al., 2000) causing DCM. The polymorphism c.−94C>G is associated with HCM (Honda et al., 2007). This polymorphism is located in nucleotide −94 of exon 1 in the 5′-untranslated region of SGCD (5′-UTR). Implicated nucleotides are guanine (G) and cytosine (C), whereas the C allele was a significant risk factor for coronary spasm in Japanese patients with HCM (Honda et al., 2007).

Analysis of c.−94C>G polymorphism in Japanese and Chinese populations showed that the frequency for the G allele is much greater (0.844). On the contrary, in northern and western European populations as well as in the African population the frequency is greater for the C allele (0.828) in comparison with the G allele (0.172) (www.hapmap.org). This polymorphism has not been analyzed in Mexican-Amerindian and Mexican-Mestizo populations. Because these populations have a greater proportion of genes with an Asian ancestral origin (Lisker et al., 1990; Cavalli-Sforza, 1997; Gamboa et al., 2000), frequencies of the polymorphism in these populations may be similar to Asian populations and may be a risk factor for HCM in these populations, similar to what has been reported for the Japanese population. The aim of our study was to evaluate the frequency of c.−94C>G polymorphism in Mexican-Amerindian and Mexican-Mestizo populations.

Materials and Methods

Study subjects

We studied c.−94C>G polymorphism in 265 individuals from two groups. The first group included 165 Mexican-Amerindian individuals: 23 Triquis (from the state of Oaxaca in southeastern Mexico), 24 Mayas (from the state of Yucatan in southeastern Mexico), 25 Zapotecos (from the state of Oaxaca in southeastern Mexico), 41 Nahuas (from the state of Guerrero in southern Mexico), and 52 Mixtecos (from the state of Oaxaca in southeastern Mexico). All Amerindian individuals and their ancestors (two generations) were born in the same community and spoke their own native language (Triquis, Zapotecos, and Mixtecos are included in the linguistic family Oto-mangue; Nahuas belong to the family Yuto-Nahua and Mayas to the family Maya). The second group was comprised of 100 healthy unrelated individuals aged 30-70 years. They were all born in Mexico and their parents and grandparents were born in Mexico and were considered Mexican-Mestizos. Included data of the c.−94C>G polymorphism in the HapMap databases (www.hapmap.org/) for the populations of Yoruba (Nigeria, YRI, n = 90, including 30 parent-offspring trios), European-Americans (Utah residents with ancestry from northern and western Europe, CEU, n = 90, including 30 parent-offspring trios from the Centre d'Etude du Polymorphisme Humain), Han Chinese (CHB, n = 45, Beijing, China) and Japanese (JPT, n = 45, Tokyo, Japan) were used.

The study was approved by the Ethics Committee in Investigation in Health, National Medical Center XXI Century, Mexican Institute of Social Security. All participants provided written informed consent prior to their inclusion in the study.

Screening for c.−94C > G polymorphism

Peripheral blood samples were obtained from all individuals, and genomic DNA was purified using Illustra Blood GenomicPrep Mini Spin Kit (GE Healthcare, Buckinghamshire, UK). Single-nucleotide polymorphism (SNP) analysis was performed using real-time PCR allelic discrimination. The c.−94C>G polymorphism was genotyped by TaqMan assay (C_26840118_10; TaqMan Single-Nucleotide Polymorphism Genotyping Assays; Applied Biosystems, Foster City, CA) on an ABI Prism 7900HT (Applied Biosystems). Genotyping call rate exceeded 95% and no discordant genotypes were observed in 20 duplicate samples. Real-time PCR was initiated with preincubation for 10 min at 95°C, followed by 40 cycles of 15 s at 92°C and 1 min at 60°C.

Statistical analysis

Genotype distributions were tested for deviation from Hardy-Weinberg equilibrium in all groups. Allele and genotype frequencies were compared using χ² test; a p-value of <0.05 was accepted as statistically significant.

Results

Allele and genotype distributions of the c.−94C>G polymorphism were analyzed in all groups described previously. Allele frequencies in these groups were similar except for Triquis (0.33 Triquis, 0.54 Zapotecos, 0.54 Mayas, 0.46 Nahuas, and 0.49 Mixtecos). Triquis showed a marked difference from the other individuals analyzed (Table 1). When each Amerindian group was compared with the entire Mexican-Mestizo sample, Triquis was the only group that demonstrated a significant difference. However, when the total sample of Mexican-Amerindian populations was compared with the Mexican-Mestizos, the difference was not significant (p = 0.12225; Table 2).

Table 1.

Allele and Genotype Frequencies of c.−94C>G Polymorphism in Mexican Populations

		Genotype frequency n (%)			Allele frequency n (%)
	n	CC	CG	GG	C	G	p-Value^a
Triquis	23	4 (17.40)	7 (30.43)	12 (52.17)	15 (32.60)	31 (67.40)	0.00742
Mayas	24	7 (29.17)	12 (50.00)	5 (20.83)	26 (54.17)	22 (45.83)	ND
Zapotecos	25	8 (32.00)	11 (44.00)	6 (24.00)	27 (54.00)	23 (46.00)	ND
Nahuas	41	10 (24.40)	18 (43.90)	13 (31.71)	38 (46.34)	44 (53.66)	ND
Mixtecos	52	11 (21.15)	29 (55.77)	12 (23.08)	51 (49.04)	53 (51.00)	ND
Mestizos	100	28 (28.00)	53 (53.00)	19 (19.00)	109 (54.50)	91 (45.50)	ND

p-Value of compared Mexican-Amerindian populations versus Mexican-Mestizos population.

ND, p-value not significantly different.

Table 2.

Allele Frequencies of c.−94C>G Polymorphism in Different Populations

		Allele frequency n (%)		p-Value^a
	n	C	G	Versus Mestizos	Versus European	Versus Chinese	Versus Japanese	Versus African
Amerindian	165	157 (47.48)	173 (52.42)	0.12225	0.00026	9.723 e −07	4.239 e −08	6.479 e −14
Mestizos	100	109 (54.50)	91 (45.50)		0.04889	1.514 e −08	5.357 e −10	1.704 e −08
European (CEU)	90	116 (64.44)	64 (35.55)
Chinese (CHB)	45	17 (18.90)	73 (81.10)
Japanese (JPT)	45	14 (15.56)	76 (84.44)
African (YRI)	90	147 (81.67)	33 (18.33)

p-Value of compared Mexican-Amerindian and Mexican-Mestizos population versus each population previously described (European, Asian, Chinese, and African).

Mexican-Amerindian and Mexican-Mestizo allele frequencies were compared with other populations obtained from HapMap databases. Our data show that the C allele is more frequent in Mexican-Amerindian and Mexican-Mestizos (47.48% and 54.50%, respectively; p > 0.05; Table 2) than in Asian populations from Japan and China (15.56% and 18.90%, respectively; p < 0.05; Table 2) but less frequent than in African and European populations (81.67% and 64.44%, respectively; p < 0.05; Table 2).

Discussion

Mutations in SGCD contributed to the pathogenesis of LGMD-2F, DCM, and HCM. The c.−94C>G polymorphism was significantly associated with coronary spasm in Japanese patients with HCM. In this study, allele and genotype frequencies of this polymorphism are described in Mexican-Amerindian and Mexican-Mestizo populations. Frequencies were compared among Mexican populations. Similar values were observed in allelic and genotypic frequencies with the exception of Triquis who showed the lowest allele frequency. Genotypic differences between Triquis and other Mexican-Amerindian and Mestizo groups were previously observed for other genetic markers such as PPARG2 Ala12 (Canizales-Quinteros et al., 2007), MTHFR, and ANGIO (Coral-Vázquez, pers. comm., 2008). This difference is mainly attributable to the fact that the Triquis are a closed ethnic group with only 25,000 inhabitants and a rigid social organization that prevents them from mixing with other populations (Lewin-Fischer and Sandoval-Cruz, 2007.

Mexican population frequencies were also compared with other world populations (as described in the Materials and Methods section), and the distribution of this polymorphism showed that the frequencies were significantly different (Table 2). Consequently, the c.−94C>G polymorphism distribution observed in Mexican populations is distinguished from other populations including Europeans, Asians, and Africans. We expected similar frequencies to those in Asian populations because it has been observed that the Mexican-Amerindian populations have a higher proportion of genes with Asian origin (Vargas-Alarcón et al., 2002; Gamboa et al., 2006); however, Mexican-Amerindian frequencies were very different from Asian populations. This is very interesting because the allelic frequencies of the Mexican-Amerindian and Mexican-Mestizo populations have differences with all the populations that were compared. Therefore, it is necessary to study the c.−94C>G polymorphism in Mexican patients with HCM to clarify whether the high frequency found in this study from this allele confers susceptibility for developing HCM in the Mexican population.

Footnotes

Acknowledgments

This work was supported by the Consejo Nacional de Ciencia y Tecnología (CONACYT), México (grant no. 86350) and by the Fondo para la Investigación en Salud (FIS), Mexico (grant FIS/MSS/PROT/547).

Disclosure Statement

No competing financial interests exist.

References

Canizales-Quinteros

, Aguilar-Salinas

, Ortiz-López

et al. 2007. Association of PPARG2 Pro12Ala variant with larger body mass index in Mestizo and Amerindian populations of Mexico. Hum Biol, 79:111-119.

Cavalli-Sforza

. 1997. Genes, peoples, and languages. Proc Natl Acad Sci USA, 94:7719-7724.

Gamboa

, Hernández-Pacheco

, Hesiquio

. 2000. Apolipoprotein polymorphism in the Indian and Mestizo populations of México. Hum Biol, 62:975-981.

Gamboa

, Zamora

, Rodríguez-Pérez

et al. 2006. Distribution of paraoxonase PON1 gene polymorphisms in Mexican populations: its role in the lipid profile. Exp Mol Pathol, 80:85-90.

Honda

, Sugiyama

, Sakamoto

et al. 2007. Impact of delta sarcoglycan gene polymorphism on the occurrence of coronary spastic angina in Japanese patients with hypertrophic cardiomyopathy. Circ J, 71:1263-1267.

Kärkkäinen

, Miettinen

, Tuomainen

et al. 2003. A novel mutation, Arg71Thr, in the delta-sarcoglycan gene is associated with dilated cardiomyopathy. J Mol Med, 81:795-800.

Lewin-Fischer

, Sandoval-Cruz

. 2007. Triquis. Comisión Nacional para el Desarrollo de los Pueblos Indígenas (CDI): Mexico City, Mexico.

Lim

, Duclos

, Broux

et al. 1995. Beta-sarcoglycan: characterization and role in limb girdle muscular dystrophy linked to 4q12. Nat Genet, 11:257-265.

Lisker

, Pérez-Briceño

, Ramirez

et al. 1990. Gene frequencies and admixture estimates in four Mexican urban centers. Hum Biol, 62:791-801.

10.

Moreira

, Vainzof

, Suzuki

et al. 2003. Genotype-phenotype correlations in 35 Brazilian families with sarcoglycanopathies including the description of three novel mutations. J Med Genet, 40:E12.

11.

Nigro

, Moreira

, Piluso

et al. 1996. Autosomal recessive limb-girdle muscular dystrophy, LGMD2F, is caused by a mutation in the delta sarcoglycan gene. Nat Genet, 14:195-198.

12.

Nigro

, Okazaki

, Belsito

et al. 1997. Identification of the Syrian hamster cardiomyopathy gene. Hum Mol Genet, 6:601-607.

13.

Noguchi

, Mcnally

, Othmane

et al. 1995. Mutations in the dystrophin-associated protein gamma-sarcoglycan in chromosome 13 muscular dystrophy. Science, 270:819-822.

14.

Tsubata

, Bowles

, Vatta

et al. 2000. Mutations in the human delta-sarcoglycan gene in familial and sporadic dilated cardiomyopathy. J Clin Invest, 106:655-662.

15.

Vargas-Alarcón

, Gamboa

, Vergara

et al. 2002. LMP2 and LMP7 gene polymorphism in Mexican populations: Mestizos and Amerindians. Genes Immun, 3:373-377.