Regulatory modules function in a non-autonomous manner to control transcription of the mbp gene

Abstract

Multiple regulatory modules contribute to the complex expression programs realized by many loci. Although long thought of as isolated components, recent studies demonstrate that such regulatory sequences can physically associate with promoters and with each other and may localize to specific sub-nuclear transcription factories. These associations provide a substrate for putative interactions and have led to the suggested existence of a transcriptional interactome. Here, using a controlled strategy of transgenesis, we analyzed the functional consequences of regulatory sequence interaction within the myelin basic protein (mbp) locus. Interactions were revealed through comparisons of the qualitative and quantitative expression programs conferred by an allelic series of 11 different enhancer/inter-enhancer combinations ligated to a common promoter/reporter gene. In a developmentally contextual manner, the regulatory output of all modules changed markedly in the presence of other sequences. Predicted by transgene expression programs, deletion of one such module from the endogenous locus reduced oligodendrocyte expression levels but unexpectedly, also attenuated expression of the overlapping golli transcriptional unit. These observations support a regulatory architecture that extends beyond a combinatorial model to include frequent interactions capable of significantly modulating the functions conferred through regulatory modules in isolation.

Thymic CCL2 influences induction of T-cell tolerance

“…MBP transcription is regulated by 4 enhancers localized in the first 10 kb of the mbp 5 0 -flanking sequence. One of the enhancers can enhance the transcription of both mbp and golli-mbp genes [51]. Although it has not been localized, the expression pattern of the MBP-CCL2 transgene that we observe is thus consistent with integration at a site(s) controlled by a Gollimbp enhancer.…”

Cis‐control of Six1 expression in neural crest cells during craniofacial development

“…In Sato's study, the two enhancers were cloned and examined individually, which could explain why enhancer activity in these tissues was not reported. The traditional view is that the interactions of multiple enhancers is mainly summative; however, there have also been reports of other more complex mechanisms such as the nonautonomous regulatory modules in the control of mbp in Drosophila . In the present study, a synergistic effect of Six1E1 and Six1E2 was observed, adding an additional example of enhancer synergy in vertebrates.…”

Functional organization of an Mbp enhancer exposes striking transcriptional regulatory diversity within myelinating glia

“…Specifically, the mbp and hprt loci are in different topological domains on different chromosomes, likely localize to distinct nuclear domains, recruit different epigenetic marks (Dixon et al, ; Dowen et al, ; Dowen and Young, ; Gibcus and Dekker, ; Jin et al, ) and generate unique non‐coding RNAs (ncRNAs); all with potential, and possibly competing, regulatory consequences (reviewed by Bonasio and Shiekhattar, ). To begin relating our findings with M3 reporter constructs to its function within the endogenous mbp locus, we evaluated the expression of an endogenous mbp allele deleted of M3 (Dib et al, ). This M3KO allele exposed the presence of additional regulatory components capable of driving mbp expression in oligodendrocytes at all ages (Dib et al, ).…”

“…The adjacent M2 lacks autonomous activity but augments M1. M3, the focus of this investigation, drives robust reporter gene expression in myelinating oligodendrocytes at all ages and when deleted from the endogenous locus, mbp and overlapping golli transcripts are markedly reduced (Dib et al, ). It also drives transient expression in myelin‐elaborating Schwann cells in juveniles.…”