CpGds

CpGds is not an established term in major reference databases; in some genomics papers, CpGds is used informal ly to denote CpG-dense segments of DNA. The term is typically used to refer to regions with higher frequency of CpG dinucleotides than the genomic background, often comparable to what are called CpG islands or high-CpG-density regions. CpG density in the genome is measured by the observed-to-expected CpG ratio and by the proportion of CpG sites within a given window. In mammals, CpG dinucleotides are relatively rare genome-wide due to methylation-driven mutations, but CpG-dense segments near gene promoters tend to be relatively unmethylated and therefore accessible for transcription initiation.

Annotation and interpretation: CpGds are frequently located in promoter regions, first exons, and other regulatory elements. They are often associated with housekeeping genes and developmentally regulated genes. Aberrant methylation of CpG-dense regions is a hallmark of many cancers and various developmental disorders, and studies may refer to CpGds when analyzing methylation patterns across the genome.

Methods and resources: Identification is performed through whole-genome bisulfite sequencing, reduced representation bisulfite sequencing, or methylation arrays, followed by segmentation to define CpG-dense regions. Statistical criteria for CpGds vary across studies, so readers should consult the specific paper for definitions. References to CpGds may appear alongside discussions of CpG islands, methylation landscapes, and epigenomic regulation.