Heritability of Commonly Measured Blood Cell Phenotypes in the San Antonio Family Heart Study.

Heritability (h²) indicates the extent to which genes contribute to the observed inter-individual variation in a phenotype. Traits that have a high h² may be fruitful targets of a subsequent genome screen to identify quantitative trait loci (QTL) and the genetic variants underlying them. We have estimated the heritabilities of measurements that commonly comprise a complete blood cell count (CBC) for members of the San Antonio Family Heart Study (table). The number of white blood cells per μL of blood (WBC) was not under genetic influence (h² = 0.160, p = 0.253), however, the individual components of the differential (lymphocyte, monocyte, and granulocyte percentage) did appear to be. Red blood cell count (RBC) had the highest heritability (h² = 0.638, p < 0.001) with both the mean corpuscular volume (MCV) and the red cell distribution width (RDW) demonstrating moderate heritability. The platelet count (Plt) and the mean platelet volume (MPV) had a mild genetic influence that was nominally significant. Currently, the fourth longitudinal examination of this cohort is in progress and to date we have measurements for 154 Mexican American subjects in 16 nuclear families. If prior recruitment rate is maintained, bivariate analyses assessing pleiotropy between traits may be available for presentation. Some of these traits have been investigated previously, but for many these are the first reported h² estimates to our knowledge. This investigation is a necessary first step to understanding the contributions of genes to these important clinical measurements and to the elucidation of the biological pathways involved in their regulation, which may lead to improved diagnostics and therapies to treat blood cell-related disorders.