BACKGROUND: Mitochondrial DNA (mtDNA) mutations cause a wide range of serious genetic diseases with maternal inheritance. Because of the high transmission risk and the absence of therapy in these disorders, at-risk couples often ask for prenatal diagnosis (PND). However, because heteroplasmy load (coexistence of mutant and wild-type mtDNA) may vary among tissues and with time, the possibility that a single fetal sample may not reflect the whole neonate impedes prenatal diagnosis of mtDNA diseases. METHODS: We performed 13 prenatal diagnoses for the NARP (neurogenic weakness, ataxia, retinitis pigmentosa) m.8993T-->G mtDNA mutation (p.Leu156Arg) in the ATP synthase subunit 6 gene. Analyses were performed on chorionic villous (CVS) and/or amniocyte samples carried out at various stages of pregnancy, using a method enabling quantification of low DNA amounts. RESULTS: Maternal mutant loads ranged from 0 to 75% in blood and had no predictive value for the fetus status, except for women with no detectable mutant DNA, whose fetuses were consistently mutation-free. In 8/13 PND, mutant load was <30%. These children are healthy at 2-7 years of age. In 5/13 PND, mutant load ranged from 65 to 100%, and parents preferred to terminate the pregnancies (15-22 weeks of gestation). Single-cell analysis of 20 trophoblastic cells and 21 amniocytes isolated from two affected fetuses found an average mutant load close to the overall CVS and amniocyte mutant load, despite striking intercellular variation. The m.8993T-->G mutant loads, assessed in 7, 17, 11, and 5 different tissues from 4 terminations, respectively, were identical in all tissues from a given individual (mean (SD) 78 (1.2)%, 91 (0.7)%, 74 (2)%, and 63 (1.6)% for the 4 fetuses, respectively). CONCLUSIONS: Our results indicate that the placental/amniotic mutant loads do reflect the NARP mutant mtDNA load in the whole fetus, even when the sample amount is small, and suggest that heteroplasmy level remains stable during pregnancy, at least after 10 weeks of gestation. Although these data establish the feasibility of PND for this mutation, assessing more precisely the correlation between mutant load and disease severity should further help in interpreting PND results.
BACKGROUND: Mitochondrial DNA (mtDNA) mutations cause a wide range of serious genetic diseases with maternal inheritance. Because of the high transmission risk and the absence of therapy in these disorders, at-risk couples often ask for prenatal diagnosis (PND). However, because heteroplasmy load (coexistence of mutant and wild-type mtDNA) may vary among tissues and with time, the possibility that a single fetal sample may not reflect the whole neonate impedes prenatal diagnosis of mtDNA diseases. METHODS: We performed 13 prenatal diagnoses for the NARP (neurogenic weakness, ataxia, retinitis pigmentosa) m.8993T-->G mtDNA mutation (p.Leu156Arg) in the ATP synthase subunit 6 gene. Analyses were performed on chorionic villous (CVS) and/or amniocyte samples carried out at various stages of pregnancy, using a method enabling quantification of low DNA amounts. RESULTS: Maternal mutant loads ranged from 0 to 75% in blood and had no predictive value for the fetus status, except for women with no detectable mutant DNA, whose fetuses were consistently mutation-free. In 8/13 PND, mutant load was <30%. These children are healthy at 2-7 years of age. In 5/13 PND, mutant load ranged from 65 to 100%, and parents preferred to terminate the pregnancies (15-22 weeks of gestation). Single-cell analysis of 20 trophoblastic cells and 21 amniocytes isolated from two affected fetuses found an average mutant load close to the overall CVS and amniocyte mutant load, despite striking intercellular variation. The m.8993T-->G mutant loads, assessed in 7, 17, 11, and 5 different tissues from 4 terminations, respectively, were identical in all tissues from a given individual (mean (SD) 78 (1.2)%, 91 (0.7)%, 74 (2)%, and 63 (1.6)% for the 4 fetuses, respectively). CONCLUSIONS: Our results indicate that the placental/amniotic mutant loads do reflect the NARP mutant mtDNA load in the whole fetus, even when the sample amount is small, and suggest that heteroplasmy level remains stable during pregnancy, at least after 10 weeks of gestation. Although these data establish the feasibility of PND for this mutation, assessing more precisely the correlation between mutant load and disease severity should further help in interpreting PND results.
Authors: C Bouchet; J Steffann; J Corcos; S Monnot; V Paquis; A Rötig; S Lebon; P Levy; G Royer; I Giurgea; N Gigarel; A Benachi; Y Dumez; A Munnich; J P Bonnefont Journal: J Med Genet Date: 2006-05-11 Impact factor: 6.318
Authors: P F Chinnery; D R Thorburn; D C Samuels; S L White; H M Dahl; D M Turnbull; R N Lightowlers; N Howell Journal: Trends Genet Date: 2000-11 Impact factor: 11.639
Authors: Nadine Gigarel; Nelly Frydman; Philippe Burlet; Violaine Kerbrat; Julie Steffann; René Frydman; Arnold Munnich; Pierre F Ray Journal: Hum Genet Date: 2003-12-12 Impact factor: 4.132
Authors: Auke B C Otten; Suzanne C E H Sallevelt; Phillippa J Carling; Joseph C F M Dreesen; Marion Drüsedau; Sabine Spierts; Aimee D C Paulussen; Christine E M de Die-Smulders; Mary Herbert; Patrick F Chinnery; David C Samuels; Patrick Lindsey; Hubert J M Smeets Journal: Hum Reprod Date: 2018-07-01 Impact factor: 6.918
Authors: Sophie Monnot; Nadine Gigarel; David C Samuels; Philippe Burlet; Laetitia Hesters; Nelly Frydman; René Frydman; Violaine Kerbrat; Benoit Funalot; Jelena Martinovic; Alexandra Benachi; Josué Feingold; Arnold Munnich; Jean-Paul Bonnefont; Julie Steffann Journal: Hum Mutat Date: 2011-01 Impact factor: 4.878
Authors: Gerald Pfeffer; Emma L Blakely; Charlotte L Alston; Adam Hassani; Mike Boggild; Rita Horvath; David C Samuels; Robert W Taylor; Patrick F Chinnery Journal: J Neurol Neurosurg Psychiatry Date: 2012-05-10 Impact factor: 10.154