HTR2A and obstructive sleep apnea syndrome: In that study, 53 candidate genes for OSA were genotyped and three loci were identified meeting chip-wide significance criteria, 2 in EAs (loci in C-reactive protein - CRP and glial cell derived neurotrophic factor - GDNF) and 1 in AAs (locus in serotonin 2A receptor - HTR2A).