Table 2. Relationship between mitochondria haplogroup and copy number among African American participants in the SAPPHIRE and SAGE II cohorts*.
| Mitochondrial haplogroup† | SAPPHIRE cohort | SAGE II cohort | ||||||
|---|---|---|---|---|---|---|---|---|
| Number of participants‡ | African ancestry (mean ± SD)§ | Copy number (mean ± SD)|| | P-value¶ | Number of participants‡ | African ancestry (mean ± SD)§ | Copy number (mean ± SD)|| | P-value¶ | |
| L0 | 164 | 0.81 ± 0.09 | 201.95 ± 59.25 | 0.827 | 64 | 0.82 ± 0.09 | 228.63 ± 59.02 | 0.734 |
| L1 | 682 | 0.82 ± 0.09 | 215.91 ± 60.95 | 0.010 | 243 | 0.80 ± 0.11 | 228.75 ± 52.67 | 0.618 |
| L2 | 1088 | 0.82 ± 0.09 | 211.52 ± 58.99 | 0.079 | 370 | 0.81 ± 0.10 | 228.66 ± 60.10 | 0.621 |
| L3 | 1408 | 0.82 ± 0.09 | 218.27 ± 62.84 | 0.001 | 465 | 0.81 ± 0.09 | 237.46 ± 65.52 | 0.063 |
| East Eurasian | 61 | 0.77 ± 0.16 | 222.52 ± 44.71 | 0.008 | 49 | 0.67 ± 0.18 | 222.18 ± 56.82 | 0.739 |
| West Eurasian | 181 | 0.56 ± 0.27 | 203.33 ± 57.60 | Reference | 88 | 0.58 ± 0.18 | 225.48 ± 52.70 | Reference |
SAPPHIRE denotes the Study of Asthma Phenotypes and Pharmacogenomic Interactions by Race-ethnicity; SAGE II, Study of African Americans, Asthma, Genes, & Environment II; and SD, standard deviation.
*The SAPPHIRE study sample was restricted to participants aged ≥18 years at enrollment and the SAGE II study samples was restricted to participants aged <20 years at enrollment.
†Geographical mitochondrial haplogroup assignments were based on those described by Pereira et al. (Am J Hum Genet. 2009; 84:628–40). Haplogroups L0, L1, L2, and L3 are considered to be African. Given the small number of study individuals with non-African haplogroups, we grouped most of the remaining haplogroups into the broad categories of East Eurasian and West Eurasian.
‡Includes individuals with and without asthma in each cohort.
§African ancestry was estimated using a set of autosomal markers which spanned the nuclear genome.
||The mitochondrial copy number estimate was for whole blood. It was based on the sequencing read depth ratio between mitochondrial and nuclear DNA isolated from blood leukocytes.
¶P-values were calculated using the Welch two sample t-test to compare mitochondrial copy numbers between West Eurasian haplogroups (referent) and the other haplogroups.