One‑carbon pathway gene expression analyses in blood samples of subjects with trisomy 21

Trisomy 21 (T21) is the genetic cause of Down syndrome (DS), and the presence of extra genetic material causes altered expression of genes located on chromosome 21 (Hsa21) and others, with effects as altered levels of metabolic reaction products. The one‑carbon pathway plays a central role in correct human neurodevelopment and was found to be altered in DS and neurological impairments of different entities. In this work, the expression of 42 genes involved in the one‑carbon cycle was analyzed in blood samples from 10 subjects with T21 and 10 euploid (N) subjects. Additionally, plasmatic concentration of methylcobalamin (MeCbl) was evaluated in 10 subjects with T21 and 7 N subjects. The results showed that 13 genes out of 42 were differentially expressed: 11 were over-expressed (ABCC3, ABCC4, ARMT1, CTH, FOLR2, GART, ICMT, PRMT2, SETD4, SLC19A1, and NSD2) and 2 were under-expressed (NSUN3 and TRMT112). Among these, 4 over-expressed genes are located on Hsa21 (GART, PRMT2, SETD4, and SLC19A1). Statistical analyses revealed significant correlations between gene expression data, highlighting interconnections among genes. Finally, MeCbl shows a slight statistically significant reduction in the T21 group. In conclusion, the presence of three copies of Hsa21 leads to the dysregulation of gene expression associated with the one‑carbon cycle. This dysregulation affects genes located on both Hsa21 and other chromosomes resulting in metabolic alterations. Additionally, new gene interconnections were discovered that have not been previously reported in the literature.