{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,31]],"date-time":"2026-07-31T05:00:15Z","timestamp":1785474015318,"version":"3.56.0"},"reference-count":43,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2026,7,29]],"date-time":"2026-07-29T00:00:00Z","timestamp":1785283200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100009592","name":"Beijing Municipal Science and Technology Commission","doi-asserted-by":"crossref","award":["Z221100005222031"],"award-info":[{"award-number":["Z221100005222031"]}],"id":[{"id":"10.13039\/501100009592","id-type":"DOI","asserted-by":"crossref"}]},{"award":["Z221100005222031"],"award-info":[{"award-number":["Z221100005222031"]}],"id":[{"id":"https:\/\/ror.org\/034k14f91","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Genes"],"abstract":"<jats:p>Background: Beijing\u2019s 2024 school physical education reforms have substantially increased activity demands on children, yet population-level genotype data for Chinese schoolchildren remain scarce. Objectives: To characterize ACTN3 R577X, MTHFR C677T, MTHFR A1298C, and MTRR A66G polymorphisms in 564 Beijing schoolchildren; test Hardy-Weinberg equilibrium (HWE); compare allele frequencies with East Asian reference populations; and perform multi-locus cumulative allele analysis across all four loci. Methods: Cross-sectional study of 564 primary and secondary school students (265 males, 299 females) in Beijing. Genotyping was performed by PCR and Sanger sequencing using saliva-derived DNA; the overall call rate was 100% (564\/564). HWE was assessed using the exact test of Wigginton et al. Allele frequencies were compared with 1000 Genomes CHB (n=103) and gnomAD EAS (n\u22482604) using chi-squared or Fisher\u2019s exact tests. Cumulative variant allele counts (0\u20138) were computed across all four loci. Linkage disequilibrium (LD) and haplotype frequencies were estimated using the EM algorithm. Results: All four loci were in HWE (all p&gt;0.05). Genotype frequencies were: ACTN3 R577X\u2014RR 31.56%, RX 49.11%, XX 19.33%; MTHFR C677T\u2014CC 18.62%, CT 46.99%, TT 34.40%; MTHFR A1298C\u2014AA 71.81%, AC 26.42%, CC 1.77%; MTRR A66G\u2014AA 56.21%, AG 35.82%, GG 7.98%. No significant sex differences were observed at any locus (all p&gt;0.05). Allele frequencies were consistent with East Asian reference populations. Across all four loci, 87.23% of students carried \u22652 variant alleles; 29.26% carried \u22654. LD between MTHFR C677T and A1298C was moderate to strong (|D\u2032|=0.97, r2=0.23). The double-mutant T-C haplotype was rare (frequency =0.002). Conclusions: This study provides genotype frequency data for exercise- and folate metabolism-related polymorphisms in a sample of Beijing schoolchildren. These descriptive frequency data establish a baseline for future genotype\u2013phenotype association studies; however, the sample is limited to two schools in two districts of Beijing and does not represent the broader Chinese pediatric population. Studies incorporating fitness, biochemical, and dietary data are required before such genetic profiles can inform educational or clinical recommendations. Given the purely descriptive, cross-sectional nature of the study and the absence of phenotypic data, these genotype frequency data do not, on their own, provide a basis for individualized physical education programming or nutritional recommendations.<\/jats:p>","DOI":"10.3390\/genes17080886","type":"journal-article","created":{"date-parts":[[2026,7,29]],"date-time":"2026-07-29T10:13:47Z","timestamp":1785320027000},"page":"886","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Distribution of ACTN3 R577X, MTHFR C677T, MTHFR A1298C, and MTRR A66G Polymorphisms in 564 School-Aged Children in Beijing: A Cross-Sectional Study"],"prefix":"10.3390","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0009-0004-8322-4196","authenticated-orcid":false,"given":"Xinrui","family":"Peng","sequence":"first","affiliation":[{"name":"Precision Omics Laboratory for Sport Medicine & Engineering, Sports & Medicine Integrative Innovation Center, Capital University of Physical Education and Sports, Beijing 100191, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wangxin","family":"Ding","sequence":"additional","affiliation":[{"name":"Precision Omics Laboratory for Sport Medicine & Engineering, Sports & Medicine Integrative Innovation Center, Capital University of Physical Education and Sports, Beijing 100191, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xin","family":"Kang","sequence":"additional","affiliation":[{"name":"Precision Omics Laboratory for Sport Medicine & Engineering, Sports & Medicine Integrative Innovation Center, Capital University of Physical Education and Sports, Beijing 100191, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuhao","family":"Yan","sequence":"additional","affiliation":[{"name":"Precision Omics Laboratory for Sport Medicine & Engineering, Sports & Medicine Integrative Innovation Center, Capital University of Physical Education and Sports, Beijing 100191, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-5904-0873","authenticated-orcid":false,"given":"Yanjing","family":"Chen","sequence":"additional","affiliation":[{"name":"Precision Omics Laboratory for Sport Medicine & Engineering, Laboratory and State Owned Assets Management Division, Capital University of Physical Education and Sports, Beijing 100191, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7915-0495","authenticated-orcid":false,"given":"Yan","family":"Zhang","sequence":"additional","affiliation":[{"name":"Precision Omics Laboratory for Sport Medicine & Engineering, Sports & Medicine Integrative Innovation Center, Capital University of Physical Education and Sports, Beijing 100191, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,7,29]]},"reference":[{"key":"ref_1","unstructured":"Beijing Municipal Education Commission (2026, June 03). 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