The primers (Eurofins MWG Operon; Huntsville, AL) for amplification (Table S1) and sequencing (Table S2) were designed using the Primer3 web resource.32 (link) All 22 exons and their adjacent intronic sequences of the SLC44A2 gene were amplified (DNA Engine Tetrad 2 Peltier Thermal Cycler; Bio-Rad, Hercules, CA) using only 8 reactions (Table S1).