Intractable Rare Dis Res. 2023;12(1):29-34. (DOI: 10.5582/irdr.2023.01016)

A regionally adapted HRM-based technique to screen MMACHC carriers for methylmalonic acidemia with homocystinuria in Shandong Province, China

Yang HN, Li M, Zou L, Zou H, Zhao Y, Cui YZ, Han JX

Methylmalonic acidemia with homocystinuria (MMA-cblC) is an autosomal recessive genetic disorder of organic acid metabolism. Shandong, a northern province of China, has a significantly high incidence of about 1/4,000, suggesting a high carrying rate among the local population. The current study established a PCR technique involving high-resolution melting (HRM) to screen for carriers based on hotspot mutation analysis to further develop a preventive strategy to reduce the local incidence of this rare disease. Whole-exome sequencing of 22 families with MMA-cblC and a comprehensive literature review were used to identify MMACHC hotspot mutations in Shandong Province. Subsequently, a PCR-HRM assay based on the selected mutations was established and optimized for large-scale hotspot mutation screening. The accuracy and efficiency of the screening technique was validated using samples from 69 individuals with MMA-cblC and 1,000 healthy volunteers. Six hotspot mutations in the MMACHC gene (c.609G>A, c.658_660delAAG, c.80A>G, c.217C>T, c.567dupT and c.482G>A), which account for 74% of the alleles associated with MMA-cblC, were used to establish a screening technique. The established PCR-HRM assay detected 88 MMACHC mutation alleles in a validation study with 100% accuracy. In the general population in Shandong, the carrying rate of 6 MMACHC hotspot mutations was 3.4%. In conclusion, the 6 hotspots identified cover the majority of the MMACHC mutation spectrum, and the Shandong population has a particularly high carrying rate of MMACHC mutations. The PCR-HRM assay is highly accurate, cost-effective, and easy to use, making it an ideal choice for mass carrier screening.

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