Genomer

Genomer is a term used in some areas of genomics and systems biology to denote a proposed modular unit of genome organization. In this usage, a genomer is a region of the genome that is functionally cohesive enough to act as a regulatory and expression unit, yet is smaller than a chromosome and larger than a single gene. The concept is intended to capture how groups of genes and regulatory elements can be organized to influence gene activity in a coordinated way.

Definitions of genomer vary across studies. Some researchers describe genomers as blocks bounded by features of the 3D genome, such as chromatin interaction domains or boundaries marked by CTCF and cohesin, aligning with the idea of regulatory domains. Others define genomers by shared regulatory logic, such as coordinated expression patterns among resident genes or conserved cis-regulatory architectures across related species. Because the term is not standardized, there is no universally accepted criterion for delimiting a genomer, and its boundaries may differ between datasets or approaches.

Identification and analysis of genomers typically rely on integrative methods. These include Hi-C or related chromosome conformation capture data to map physical contacts, ChIP-seq for architectural proteins and histone marks, and RNA-seq to assess co-expression. Comparative genomics can help test for boundary conservation, while functional assays may test regulatory coherence within proposed genomers.

Significance of the concept lies in its potential to illuminate how genome organization constrains regulation and contributes to evolution. However, genomers remain a niche or exploratory construct, and they are not universally adopted as a standard unit in genome annotation. See also: topologically associating domain, regulatory domain, chromatin neighborhood.