Genetic defect suggests high blood pressure may come from mother

The defect results from a point mutation -- the substitution of a single DNA "base" for another during replication -- in the genes of a tiny cellular organ called the mitochondria, which generates a cell's energy. When reproductive cells come together to form an embryo, the mitochondrial DNA from the mother cell is passed on to the offspring. Evidence has suggested a mother-child inheritance link for high blood pressure due to mitochondrial inheritance.

The Chinese-led group, which also included researchers from the Cincinnati Children's Hospital Medical Center and the Medical University of Vienna in Austria, provides clinical, genetic, molecular and biochemical evidence that a mitochondrial mutation designated tRNAIle 4263A>G is associated with inherited high blood pressure. The DNA substitution researchers discovered is an adenine-to-guanine switch at position 4263 on the mitochondrial genome (4263A>G).

Geneticists identified a large family from northern China in which 15 of 27 members who descended from the same female ancestor had blood pressures above 140/90 mmHg even after treatment. Only seven of 81 non-maternal relatives had high blood pressure.

Researchers compared the family members with 342 Chinese residents of the same northern area to confirm a maternal link. Analysis of the mitochondrial genome of the maternal relatives and other tests revealed the site of the hypertension-related mutation and showed that it impairs the mitochondrial respiration chain, which increases levels of a reactive oxygen species (i.e., free radicals).

The findings show that inherited mitochondrial dysfunction is involved in high blood pressure and may provide new insights into maternally transmitted hypertension, researchers said.