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• C677T MTHFR frequencies in different Canadian Provinces.
  Natalie K Björklund
  Published on: 28 November 2003

• Published on: 28 November 2003

  C677T MTHFR frequencies in different Canadian Provinces.

  • Natalie K Björklund
  • Other Contributors:
    • Bernard N. Chodirker1,2 Cheryl R. Greenberg1,2 , Lorne E Seargeant1, Jane A. Evans1,2,3,

  Dear Editor

  Wilcken et al, (2003), in “Geographical and ethnic variation of the 677C>T allele of the 5,10 methylenetetrahydrofolate reductase (MTHFR): finds from over 7000 newborns from 16 areas worldwide” showed that the TT genotype in Calgary, Alberta was present in 5.8% of newborns as compared to one previous report from Quebec of 11% [Infante-Rivard et al., 2003]. The authors did not explain why this...

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  Dear Editor

  Wilcken et al, (2003), in “Geographical and ethnic variation of the 677C>T allele of the 5,10 methylenetetrahydrofolate reductase (MTHFR): finds from over 7000 newborns from 16 areas worldwide” showed that the TT genotype in Calgary, Alberta was present in 5.8% of newborns as compared to one previous report from Quebec of 11% [Infante-Rivard et al., 2003]. The authors did not explain why this difference was present, but they did state that the latter study was drawn from a selected population of infants over the 10th percentile, whereas their own study involved consecutive newborns.

  We suggest that the difference in the frequency seen in Alberta and Quebec more likely reflects the ethnic origin of Albertans versus the Quebeçois. Most Quebec residents are descendants of immigrants from France and the province has a larger proportion of Greeks and Italians compared to other Canadian jurisdictions. Caucasians in Alberta are generally the descendants of Northern and Eastern Europeans with 50% of the population being descendents of immigrants from the UK and Ireland [Population by ethnic origin,1996]. French, Italy and Greece all have a higher frequency of C677T MTHFR than eastern and northern European countries. Therefore, it is not surprising that the Quebeçois also have higher frequencies than Albertans. There have also been five other C677T MTHFR association studies in Quebec that included small control groups variously selected with homozygote frequencies ranging from 11 to 16% [Deloughery et al., 1996, Christensen et al., 1997, 1999, Delvin 2000, Merouani et al., 2001.]

  The largest single study of C677T MTHFR frequency was conducted using newborn screening filter paper cards here in Manitoba. Mogk et al (2000), genotyped 977 consecutive Manitoba newborns for the 677 C>T polymorphism and found the frequency of 677 C>T homozygotes to be 7%. The percentage of TT genotypes in Manitoba is 7% (36% heterozygotes). Manitoba has the second largest ethnically French population in Canada and has a substantial Metis (French/Aboriginal) population. We would therefore expect the frequency in Manitoba to be intermediate between that of Quebec and Alberta, as our data indicate. It is our opinion that both the 5.8% Alberta result and the 11% Quebec result are accurate estimates of the frequencies of this variant in these two ethnically different Canadian provinces.

  Reference

  (1) Population by ethnic origin, 1996 Census, provinces and territories.2003a. Statistics Canada

  (2) Christensen B, Arbour L, Tran P, Leclerc D, Sabbaghian N, Platt R, Gilfix BM, Rosenblatt DS, Gravel RA, Forbes P, Rozen R.5-21- 1999.Genetic polymorphisms in methylenetetrahydrofolate reductase and methionine synthase, folate levels in red blood cells, and risk of neural tube defects. Am J Med Genet 84:151-157.

  (3) Christensen B, Frosst P, Lussier-Cacan S, Selhub J, Goyette P, Rosenblatt DS, Genest J, Jr., Rozen R.1997.Correlation of a common mutation in the methylenetetrahydrofolate reductase gene with plasma homocysteine in patients with premature coronary artery disease. Arterioscler Thromb Vasc Biol 17:569-573.

  (4) Deloughery TG, Evans A, Sadeghi A, McWilliams J, Henner WD, Taylor LM, Jr., Press RD.12-15-1996.Common mutation in methylenetetrahydrofolate reductase. Correlation with homocysteine metabolism and late-onset vascular disease. Circulation 94:3074-3078.

  (5) Delvin EE, Rozen R, Merouani A, Genest J, Jr., Lambert M.2000a.Influence of methylenetetrahydrofolate reductase genotype, age, vitamin B-12, and folate status on plasma homocysteine in children. Am J Clin Nutr 72:1469-1473.

  (6) Infante-Rivard C, Rivard GE, Yotov WV, Genin E, Guiguet M, Weinberg C, Gauthier R, Feoli-Fonseca JC.7-4-2002.Absence of association of thrombophilia polymorphisms with intrauterine growth restriction. N Engl J Med 347:19-25.

  (7) Merouani A, Lambert M, Delvin EE, Genest J, Jr., Robitaille P, Rozen R.2001.Plasma homocysteine concentration in children with chronic renal failure. Pediatr Nephrol 16:805-811.

  (8) Mogk RL, Rothenmund H, Evans JA, Carson N, Dawson AJ.2000b.The frequency of the C677T substitution in the methylenetetrahydrofolate reductase gene in Manitoba. Clin Genet 58:406-408.

  (9) Wilcken B, Bamforth F, Li Z, Zhu H, Ritvanen A, Redlund M, Stoll C, Alembik Y, Dott B, Czeizel AE, Gelman-Kohan Z, Scarano G, Bianca S, Ettore G, Tenconi R, Bellato S, Scala I, Mutchinick OM, Lopez MA, de Walle H, Hofstra R, Joutchenko L, Kavteladze L, Bermejo E, Martinez-Frias ML, Gallagher M, Erickson JD, Vollset SE, Mastroiacovo P, Andria G, Botto LD.2003b.Geographical and ethnic variation of the 677C>T allele of 5,10 methylenetetrahydrofolate reductase (MTHFR): findings from over 7000 newborns from 16 areas world wide. J Med Genet 40:619-625.

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  Conflict of Interest:
  None declared.

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