SLC6A20 and respiratory failure: Genome-wide association studies (GWAS) on single nucleotide polymorphism (SNP) revealed a strong correlation between the SLC6A20 gene regulatory region (allele GA of rs11385942) and the respiratory failure observed in severe COVID-19, although the allele can be characterised by decreased expression of CXCR6 but increased synthesis rate of SLC6A20 and LZTFL1 [128].