Epigenetic memory plays crucial roles in gene regulation. It not only modulates 
the expression of specific genes but also has ripple effects on transcription as 
well as translation of other genes. Very often an alteration in expression 
occurs either via methylation or demethylation. In this context, "1-carbon 
metabolism" assumes a special significance since its dysregulation by higher 
levels of homocysteine; Hcy (known as hyperhomocysteinemia; HHcy), a byproduct 
of "1-Carbon Metabolism" during methionine biosynthesis leads to serious 
implications in cardiovascular, renal, cerebrovascular systems, and a host of 
other conditions. Currently, the circular RNAs (circRNAs) generated via 
non-canonical back-splicing events from the pre-mRNA molecules are at the center 
stage for their essential roles in diseases via their epigenetic manifestations. 
We recently identified a circular RNA transcript (circGRM4) that is 
significantly upregulated in the eye of cystathionine β-synthase-deficient mice. 
We also discovered a concurrent over-expression of the mGLUR4 receptor in the 
eyes of these mice. In brief, circGRM4 is selectively transcribed from its 
parental mGLUR4 receptor gene (GRM4) functions as a "molecular-sponge" for the 
miRNAs and results into excessive turnover of the mGLUR4 receptor in the eye in 
response to extremely high circulating glutamate concentration. We opine that 
this epigenetic manifestation potentially predisposes HHcy people to 
retinovascular malfunctioning.