Figure 1.

FXN protein levels in the non-FA and FA human heart. (A) Human cardiac FXN levels in individuals who do not have FA. Heart samples from five subjects at autopsy were obtained from the Department of Pathology at Weill Cornell Medicine. For each heart, the septum, left ventricle (including lateral, posterior, and anterior walls), and right ventricle were assessed. Samples were analyzed in triplicate (mean ± SEM). Subject 1 (80-year-old male, White), yellow circle; Subject 2 (75-year-old male, Hispanic), red pentagram; Subject 3 (65-year-old female, African American), blue triangle; Subject 4 (73-year-old female, White), green square; and Subject 5 (72-year-old male, White), purple diamond. Although there was subject to subject variability, on average, FXN levels in the different heart regions were similar (p ≥ 0.06). The mean of all heart samples was 59 ± 5 ng FXN/mg protein (dashed line). (B) FXN levels in human FA homozygote and heterozygote heart estimated using the mean normal levels (A) extrapolated to the heart using the FXN levels in noncardiac tissues in FA homozygous and heterozygotes (see FXN levels in a non-FA disease heart in the Results section and Lazaropoulos et al.³⁰). FA, Friedreich's ataxia; FXN, frataxin; SEM, standard error of the mean.