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MED17
mediator complex subunit 17
MED17 is located on the long (q) arm of chromosome 11, at band 11q21. Arm ratio per GRCh38 - banding schematic.
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Overview
MED17 (mediator complex subunit 17) encodes a structural component of the Mediator complex, a multi-protein assembly that coordinates the activity of RNA polymerase II during gene transcription. The Mediator complex serves as a molecular bridge, transmitting regulatory signals from DNA-binding transcription factors to the core transcription machinery. This communication is essential for precise control of gene expression patterns during development and in response to cellular signals.
Pathogenic variants in MED17 have been associated with neurodevelopmental conditions, reflecting the gene's importance in brain development and function. The protein's role in transcriptional regulation means that disruptions can affect multiple biological processes, particularly those requiring tightly controlled gene expression programmes.
What the gene does
The MED17 protein functions as a core structural subunit within the Mediator complex, which consists of approximately 30 different protein components organised into distinct modules. This complex acts as a central hub for transcriptional regulation, physically linking sequence-specific transcription factors bound to DNA regulatory elements with RNA polymerase II and its associated general transcription factors at gene promoters.
MED17 contributes to the architectural stability of the Mediator complex and helps maintain the proper positioning of other subunits. The complex processes signals from multiple transcription factors simultaneously, integrating diverse regulatory inputs to fine-tune the rate of gene transcription. This regulatory mechanism is particularly important during embryonic development, when precise spatial and temporal patterns of gene expression are required for proper tissue formation. The protein is expressed across most cell types, reflecting the fundamental nature of its role in cellular gene regulation.
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Chromosome location
MED17 is located on chromosome 11 at the cytogenetic band 11q21. This chromosomal region contains numerous genes involved in diverse cellular processes. The genomic structure and exon organisation of MED17 enable the production of the full-length protein required for Mediator complex assembly.
Protein structure
The MED17 protein is 651 amino acids in length and contains a disordered region spanning amino acids 51-83. Intrinsically disordered regions lack a fixed three-dimensional structure and often mediate protein-protein interactions or provide regulatory flexibility. This disordered segment may facilitate dynamic interactions with other Mediator subunits or transcriptional regulators, contributing to the complex's ability to respond to diverse cellular signals.
Key variants
Genetic variants in MED17 range from single nucleotide changes to small deletions or insertions that may affect protein structure or expression levels. Pathogenic variants can disrupt the protein's ability to integrate properly into the Mediator complex or impair its structural contribution to the assembly. The severity of clinical features may depend on the specific variant and its impact on protein function.
Sample of pathogenic variants
10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.1360C>T | p.Arg454Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Infantile cerebral and cerebellar atrophy with postnatal progressive microcephaly |
c.1405_1433dup | p.Leu478_Ile479insMetPheMetAsnLeuValTer | Pathogenic/Likely pathogenic | ★★☆☆ | Infantile cerebral and cerebellar atrophy with postnatal progressive microcephaly |
c.1582C>T | p.Gln528Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Infantile cerebral and cerebellar atrophy with postnatal progressive microcephaly |
c.472C>T | p.Gln158Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Infantile cerebral and cerebellar atrophy with postnatal progressive microcephaly |
c.538C>T | p.Gln180Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Infantile cerebral and cerebellar atrophy with postnatal progressive microcephaly |
c.565C>T | p.Arg189Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Infantile cerebral and cerebellar atrophy with postnatal progressive microcephaly |
c.589C>T | p.Arg197Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Infantile cerebral and cerebellar atrophy with postnatal progressive microcephaly |
c.657del | p.His219fs | Pathogenic/Likely pathogenic | ★★☆☆ | Infantile cerebral and cerebellar atrophy with postnatal progressive microcephaly |
c.835C>T | p.Arg279Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Infantile cerebral and cerebellar atrophy with postnatal progressive microcephaly |
c.916G>T | p.Glu306Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Infantile cerebral and cerebellar atrophy with postnatal progressive microcephaly |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
Pathogenic variants in MED17 have been linked to neurodevelopmental conditions characterised by intellectual disability and developmental delay. These features reflect the gene's critical role in the transcriptional programmes that guide brain development. The broad regulatory function of the Mediator complex means that MED17 disruption may affect multiple organ systems, though neurological manifestations are typically most prominent. Clinical presentations can vary among affected individuals depending on the specific genetic variant and other genetic or environmental factors.
No disease links recorded for this gene in our reference set.
UK clinical status
MED17 appears on the NHS Genomic Medicine Service PanelApp resource, indicating its relevance to UK clinical genomic testing. The gene is classified with green status on the DDG2P (Developmental Disorders Genotype-to-Phenotype) panel and the Intellectual disability panel (version R29), signifying a confirmed association with developmental conditions based on expert review of available evidence. This classification supports the inclusion of MED17 in diagnostic gene panels for patients presenting with unexplained intellectual disability or developmental delay.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What does the MED17 gene do?
MED17 provides instructions for making a protein that forms part of the Mediator complex, a large molecular assembly that helps control gene expression by connecting regulatory proteins to the machinery that reads genes. This process is essential for normal cellular function and development.
How are MED17 variants inherited?
The inheritance pattern of MED17-related conditions can vary depending on the specific variant. Some pathogenic changes may occur spontaneously (de novo) rather than being inherited from parents, whilst others may follow autosomal dominant or recessive patterns.
Is genetic testing available for MED17 in the UK?
Yes, MED17 is included on NHS clinical gene panels for intellectual disability and developmental disorders. Testing may be arranged through clinical genetics services when a patient's clinical features suggest a possible genetic cause.